umu.sePublikationer
Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 82
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Avican, Ummehan
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Doruk, Tugrul
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Östberg, Yngve
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Fahlgren, Anna
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    The Tat substrate SufI is critical for the ability of Yersinia pseudotuberculosis to cause systemic infection2017Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 85, nr 4, artikel-id e00867-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The twin arginine translocation (Tat) system targets folded proteins across the inner membrane and is crucial for virulence in many important humanpathogenic bacteria. Tat has been shown to be required for the virulence of Yersinia pseudotuberculosis, and we recently showed that the system is critical for different virulence-related stress responses as well as for iron uptake. In this study, we wanted to address the role of the Tat substrates in in vivo virulence. Therefore, 22 genes encoding potential Tat substrates were mutated, and each mutant was evaluated in a competitive oral infection of mice. Interestingly, a.sufI mutant was essentially as attenuated for virulence as the Tat-deficient strain. We also verified that SufI was Tat dependent for membrane/periplasmic localization in Y. pseudotuberculosis. In vivo bioluminescent imaging of orally infected mice revealed that both the.sufI and Delta tatC mutants were able to colonize the cecum and Peyer's patches (PPs) and could spread to the mesenteric lymph nodes (MLNs). Importantly, at this point, neither the Delta tatC mutant nor the Delta sufI mutant was able to spread systemically, and they were gradually cleared. Immunostaining of MLNs revealed that both the Delta tatC and Delta sufI mutants were unable to spread from the initial infection foci and appeared to be contained by neutrophils, while wild-type bacteria readily spread to establish multiple foci from day 3 postinfection. Our results show that SufI alone is required for the establishment of systemic infection and is the major cause of the attenuation of the Delta tatC mutant.

  • 2.
    Bamyaci, Sarp
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Ekestubbe, Sofie
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Nordfelth, Roland
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Erttmann, Saskia F.
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Edgren, Tomas
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    YopN Is Required for Efficient Effector Translocation and Virulence in Yersinia pseudotuberculosis2018Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 86, nr 8, artikel-id e00957-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Type III secretion systems (T3SSs) are used by various Gram-negative pathogens to subvert the host defense by a host cell contact-dependent mechanism to secrete and translocate virulence effectors. While the effectors differ between pathogens and determine the pathogenic life style, the overall mechanism of secretion and translocation is conserved. T3SSs are regulated at multiple levels, and some secreted substrates have also been shown to function in regulation. In Yersinia, one of the substrates, YopN, has long been known to function in the host cell contact-dependent regulation of the T3SS. Prior to contact, through its interaction with TyeA, YopN blocks secretion. Upon cell contact, TyeA dissociates from YopN, which is secreted by the T3SS, resulting in the induction of the system. YopN has also been shown to be translocated into target cells by a T3SS-dependent mechanism. However, no intracellular function has yet been assigned to YopN. The regulatory role of YopN involves the N-terminal and C-terminal parts, while less is known about the role of the central region of YopN. Here, we constructed different in-frame deletion mutants within the central region. The deletion of amino acids 76 to 181 resulted in an unaltered regulation of Yop expression and secretion but triggered reduced YopE and YopH translocation within the first 30 min after infection. As a consequence, this deletion mutant lost its ability to block phagocytosis by macrophages. In conclusion, we were able to differentiate the function of YopN in translocation and virulence from its function in regulation.

  • 3.
    Bartra, Sara Schesser
    et al.
    Department of Microbiology and Immunology, University of Miami Miller School of Medicine.
    Jackson, Michael W
    Ross, Julia A
    Plano, Gregory V
    Calcium-regulated type III secretion of Yop proteins by an Escherichia coli hha mutant carrying a Yersinia pestis pCD1 virulence plasmid.2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 2, s. 1381-6Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of four large deletions that removed a total of ca. 36 kb of DNA from the ca. 70-kb Yersinia pestis pCD1 virulence plasmid were constructed using lambda Red-mediated recombination. Escherichia coli hha deletion mutants carrying the virulence plasmid with the deletions expressed a functional calcium-regulated type III secretion system. The E. coli hha/pCD1 system should facilitate molecular studies of the type III secretion process.

  • 4.
    Bartra, Sara Schesser
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Styer, Katie L
    O'Bryant, Deanna M
    Nilles, Matthew L
    Hinnebusch, B Joseph
    Aballay, Alejandro
    Plano, Gregory V
    Resistance of Yersinia pestis to complement-dependent killing is mediated by the Ail outer membrane protein2008Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, nr 2, s. 612-622Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Yersinia pestis, the causative agent of plague, must survive in blood in order to cause disease and to be transmitted from host to host by fleas. Members of the Ail/Lom family of outer membrane proteins provide protection from complement-dependent killing for a number of pathogenic bacteria. The Y. pestis KIM genome is predicted to encode four Ail/Lom family proteins. Y. pestis mutants specifically deficient in expression of each of these proteins were constructed using lambda Red-mediated recombination. The Ail outer membrane protein was essential for Y. pestis to resist complement-mediated killing at 26 and 37 degrees C. Ail was expressed at high levels at both 26 and 37 degrees C, but not at 6 degrees C. Expression of Ail in Escherichia coli provided protection from the bactericidal activity of complement. High-level expression of the three other Y. pestis Ail/Lom family proteins (the y1682, y2034, and y2446 proteins) provided no protection against complement-mediated bacterial killing. A Y. pestis ail deletion mutant was rapidly killed by sera obtained from all mammals tested except mouse serum. The role of Ail in infection of mice, Caenorhabditis elegans, and fleas was investigated.

  • 5.
    Belibasakis, Georgios N
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Oral cellbiologi. Umeå universitet, Medicinsk fakultet, Odontologi, Oral mikrobiologi.
    Johansson, Anders
    Umeå universitet, Medicinsk fakultet, Odontologi, Parodontologi.
    Wang, Y
    Chen, C
    Kalfas, S
    Lerner, Ulf
    Umeå universitet, Medicinsk fakultet, Odontologi, Oral cellbiologi.
    The cytolethal distending toxin induces receptor activator of NF-κB ligand expression in human gingival fibroblasts and periodontal ligament cells2005Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 73, nr 1, s. 342-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actinobacillus actinomycetemcomitans is associated with localized aggressive periodontitis, a disease characterized by rapid loss of the alveolar bone surrounding the teeth. Receptor activator of NF-kappaB Ligand (RANKL) and osteoprotegerin (OPG) are two molecules that regulate osteoclast formation and bone resorption. RANKL induces osteoclast differentiation and activation, whereas OPG blocks this process by acting as a decoy receptor for RANKL. The purpose of this study was to investigate the effect of A. actinomycetemcomitans on the expression of RANKL and OPG in human gingival fibroblasts and periodontal ligament cells. RANKL mRNA expression was induced in both cell types challenged by A. actinomycetemcomitans extract, whereas OPG mRNA expression remained unaffected. Cell surface RANKL protein was also induced by A. actinomycetemcomitans, whereas there was no change in OPG protein secretion. A cytolethal distending toxin (Cdt) gene-knockout strain of A. actinomycetemcomitans did not induce RANKL expression, in contrast to its wild-type strain. Purified Cdt from Haemophilus ducreyi alone, or in combination with extract from the A. actinomycetemcomitans cdt mutant strain, induced RANKL expression. Pretreatment of A. actinomycetemcomitans wild-type extract with Cdt antiserum abolished RANKL expression. In conclusion, A. actinomycetemcomitans induces RANKL expression in periodontal connective tissue cells. Cdt is crucial for this induction and may therefore be involved in the pathological bone resorption during the process of localized aggressive periodontitis.

  • 6.
    Berglin, Ewa H.
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Carlsson, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Potentiation by sulfide of hydrogen peroxide-induced killing of Escherichia coli1985Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 49, nr 3, s. 538-543Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    L-Cysteine potentiates 100-fold the hydrogen peroxide-induced killing of a growing culture of Escherichia coli K-12 (Berglin et al., J. Bacteriol. 152:81-88). In the present study it is shown that hydrogen sulfide is formed from L-cysteine and that sodium sulfide could substitute for L-cysteine in the potentiation of hydrogen peroxide-induced killing of E. coli K-12. Addition of an amino acid, L-leucine, L-valine, or L-alanine, to an L-cysteine-containing medium with a growing culture of E. coli K-12 inhibited hydrogen sulfide formation and the potentiation of hydrogen peroxide-induced killing. These amino acids did not inhibit hydrogen sulfide formation from L-cysteine by a cell extract, and they did not inhibit the potentiation by sulfide of hydrogen peroxide-induced killing. This indicated that the amino acids protected the culture from L-cysteine-potentiated, hydrogen peroxide-induced killing by inhibiting the transport of L-cysteine into the cell. The potentiation by sodium sulfide of hydrogen peroxide-induced killing was abolished by the metal ion chelator 2,2'-bipyridyl. This indicated that metal ions, in addition to sulfide, were involved in the killing. Toxic effects of hydrogen peroxide are often presumed to be mediated by hydroxyl radicals formed in iron-catalyzed reactions. It was demonstrated that iron sulfide was more efficient than ferrous iron in catalyzing the formation of hydroxyl radicals from hydrogen peroxide. It was suggested that hydrogen sulfide formed in polymicrobial infections may play an important role in the host defense by potentiating the antimicrobial effect of hydrogen peroxide produced by phagocytic cells.

  • 7. Bielig, H
    et al.
    Rompikuntal, Pramod Kumar
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Mitesh, Dongre
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Zurek, B
    Lindmark, B
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Kufer, T A
    University of Cologne.
    NOD-like receptor activation by outer-membrane vesicles (OMVs) from non-O1 non-O139 Vibrio cholerae is modulated by the quorum sensing regulator HapR2011Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 79, nr 4, s. 1418-1427Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrio cholerae is an inhabitant of aquatic systems and one of the causative agents of severe dehydrating diarrhea in humans. It has also emerged as an important cause of different kinds of inflammatory responses and in particular, V. cholerae strains of the non-O1 non-O139 serogroups (NOVC) have been associated with such infections in human. We analyzed the potential of outer membrane vesicles (OMVs) derived from the NOVC strain V:5/04 to induce inflammatory responses in human host cells. V:5/04 OMVs were taken up by human epithelial cells and induced inflammatory responses. siRNA-mediated gene knock-down revealed that the inflammatory potential of NOVC OMVs was partially mediated by the nucleotide-binding domain, leucine rich repeat containing family member NOD1. Physiochemical analysis of the content of these OMVs, in conjunction with NOD1 and NOD2 reporter assays in HEK293T cells, confirmed the presence of both NOD1 and NOD2 active peptidoglycan in the OMVs. Furthermore, we show that deletion of the quorum sensing regulator HapR which mimics an infective life style, specifically reduced the inflammatory potential of the V:5/04 OMVs and their ability to activate NOD1 and NOD2. In conclusion, our study shows that NOVC OMVs elicit immune responses mediated by NOD1 and NOD2 in mammalian host cells. Moreover, we provide evidence that the quorum sensing machinery plays an important regulatory role in this process by attenuating the inflammatory potential of OMVs in infective conditions. This work thus identified a new facet of how Vibrio affects host immune responses and defines a role for the quorum sensing machinery in this process.

  • 8.
    Binesse, Johan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lindgren, Helena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lindgren, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Conlan, Wayne
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Roles of Reactive Oxygen Species-Degrading Enzymes of Francisella tularensis SCHU S42015Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 83, nr 6, s. 2255-2263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is a facultative intracellular bacterium utilizing macrophages as its primary intracellular habitat and is therefore highly capable of resisting the effects of reactive oxygen species (ROS), potent mediators of the bactericidal activity of macrophages. We investigated the roles of enzymes presumed to be important for protection against ROS. Four mutants of the highly virulent SCHU S4 strain with deletions of the genes encoding catalase (katG), glutathione peroxidase (gpx), a DyP-type peroxidase (FTT0086), or double deletion of FTT0086 and katG showed much increased susceptibility to hydrogen peroxide (H2O2) and slightly increased susceptibility to paraquat but not to peroxynitrite (ONOO-) and displayed intact intramacrophage replication. Nevertheless, mice infected with the double deletion mutant showed significantly longer survival than SCHU S4-infected mice. Unlike the aforementioned mutants, deletion of the gene coding for alkyl-hydroperoxide reductase subunit C (ahpC) generated a mutant much more susceptible to paraquat and ONOO- but not to H2O2. It showed intact replication in J774 cells but impaired replication in bone marrow-derived macrophages and in internal organs of mice. The live vaccine strain, LVS, is more susceptible than virulent strains to ROS-mediated killing and possesses a truncated form of FTT0086. Expression of the SCHU S4 FTT0086 gene rendered LVS more resistant to H2O2, which demonstrates that the SCHU S4 strain possesses additional detoxifying mechanisms. Collectively, the results demonstrate that SCHU S4 ROS-detoxifying enzymes have overlapping functions, and therefore, deletion of one or the other does not critically impair the intracellular replication or virulence, although AhpC appears to have a unique function.

  • 9.
    Brännström, Kristoffer
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sellin, Mikael E
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Holmfeldt, Per
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Brattsand, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Dermatologi och venereologi.
    Gullberg, Martin
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    The Schistosoma mansoni protein Sm16/SmSLP/SmSPO-1 assembles into a nine-subunit oligomer with potential To inhibit Toll-like receptor signaling.2009Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 77, nr 3, s. 1144-1154Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Sm16/SmSLP/SmSPO-1 (Sm16) protein is secreted by the parasite Schistosoma mansoni during skin penetration and has been ascribed immunosuppressive activities. Here we describe the strategy behind the design of a modified Sm16 protein with a decreased aggregation propensity, thus facilitating the expression and purification of an Sm16 protein that is soluble in physiological buffers. The Stokes radii and sedimentation coefficients of recombinant and native proteins indicate that Sm16 is an approximately nine-subunit oligomer. Analysis of truncated Sm16 derivatives showed that both oligomerization and binding to the plasma membrane of human cells depend on multiple C-terminal regions. For analysis of immunomodulatory activities, Sm16 was expressed in Pichia pastoris to facilitate the preparation of a pyrogen/endotoxin-free purified protein. Recombinant Sm16 was found to have no effect on T-lymphocyte activation, cell proliferation, or the basal level of cytokine production by whole human blood or monocytic cells. However, Sm16 exerts potent inhibition of the cytokine response to the Toll-like receptor (TLR) ligands lipopolysaccharide (LPS) and poly(I:C) while being less efficient at inhibiting the response to the TLR ligand peptidoglycan or a synthetic lipopeptide. Since Sm16 specifically inhibits the degradation of the IRAK1 signaling protein in LPS-stimulated monocytes, our findings indicate that inhibition is exerted proximal to the TLR complex.

  • 10.
    Bröms, Jeanette E
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lavander, Moa
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Meyer, Lena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    IglG and IglI of the Francisella pathogenicity island are important virulence determinants of Francisella tularensis LVS2011Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 79, nr 9, s. 3683-3696Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Gram-negative bacterium Francisella tularensis is the causative agent of tularemia, a disease intimately associated with the multiplication of the bacterium within host macrophages. This in turn requires the expression of Francisella pathogenicity island (FPI) genes, believed to encode a type VI secretion system. While the exact functions of many of the components have yet to be revealed, some have been found to contribute to the ability of Francisella to cause systemic infection in mice as well as to prevent phagolysosomal fusion and facilitate escape into the host cytosol. Upon reaching this compartment, the bacterium rapidly multiplies, inhibits activation of the inflammasome, and ultimately causes apoptosis of the host cell. In this study, we analyzed the contribution of the FPI-encoded proteins IglG, IglI, and PdpE to the aforementioned processes in F. tularensis LVS. The ΔpdpE mutant behaved similarly to the parental strain in all investigated assays. In contrast, ΔiglG and ΔiglI mutants, although they were efficiently replicating in J774A.1 cells, both exhibited delayed phagosomal escape, conferred a delayed activation of the inflammasome, and exhibited reduced cytopathogenicity as well as marked attenuation in the mouse model. Thus, IglG and IglI play key roles for modulation of the intracellular host response and also for the virulence of F. tularensis.

  • 11. Bunikis, J
    et al.
    Noppa, L
    Östberg, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Barbour, A G
    Bergström, Sven
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Surface exposure and species specificity of an immunoreactive domain of a 66-kilodalton outer membrane protein (P66) of the Borrelia spp. that cause Lyme disease1996Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 64, nr 12, s. 5111-5116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A chromosomally encoded 66-kDa protein (P66) of Borrelia spp. that cause Lyme disease has previously been shown to be associated with the spirochetal outer membrane. A topological model of P66 predicts a surface-exposed fragment which links the N- and C-terminal intramembranous domains of the protein (J. Bunikis, L. Noppa, and S. Bergström, FEMS Microbiol. Lett. 131:139-145, 1995). In the present study, an immunogenic determinant of P66 was identified by a comparison of the immunoreactivities of different fragments of P66 generated either by proteolytic treatment of intact spirochetes or as recombinant proteins expressed in Escherichia coli. The immune response to P66 during natural infection was found to be directed against the predicted surface domain which comprises amino acids at positions 454 through 491. A sequence comparison revealed considerable polymorphism of the surface domains of P66 proteins of different Lyme disease-causing Borrelia species. Five sequence patterns of this domain were observed in the B. garinii strains studied. In contrast, sequences of the relevant part of P66 of the B. afzelii and B. burgdorferi sensu stricto isolates studied were identical within the respective species. In immunoblotting, 5 of 17 (29.4%) sera from North American patients with early disseminated or persistent Lyme disease reacted against P66 of B. burgdorferi sensu stricto B31. These sera, however, failed to recognize P66 of B. afzelii and B. garinii, as well as an analog of P66 in the relapsing fever agent, B. hermsii. In conclusion, the topological model of P66 is supported by the demonstration of an apparent surface localization of an immunoreactive domain of this protein. Furthermore, analogous to the plasmid-encoded borrelial outer surface proteins, the predicted surface-exposed portion of chromosomally encoded P66 appears to be antigenically heterogenous.

  • 12.
    Bönquist, Linda
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Lindgren, Helena
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Golovliov, Igor
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Guina, Tina
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    MglA and Igl proteins contribute to the modulation of Francisella tularensis live vaccine strain-containing phagosomes in murine macrophages2008Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, nr 8, s. 3502-3510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Francisella tularensis live vaccine strain (LVS), in contrast to its iglC mutant, replicates in the cytoplasm of macrophages. We studied the outcome of infection of the murine macrophagelike cell line J774A.1 with LVS and with iglC, iglD, and mglA mutants, the latter of which is deficient in a global regulator. Compared to LVS, all of the mutants showed impaired intracellular replication up to 72 h, and the number of the mglA mutant bacteria even decreased. Colocalization with LAMP-1 was significantly increased for all mutants compared to LVS, indicating an impaired ability to escape into the cytoplasm. A lysosomal acidity-dependent dye accumulated in approximately 40% of the vacuoles containing mutant bacteria but not at all in vacuoles containing LVS. Preactivation of the macrophages with gamma interferon inhibited the intracellular growth of all strains and significantly increased acidification of phagosomes containing the mutants, but it only slightly increased the LAMP-1 colocalization. The intracellular replication and phagosomal escape of the iglC and iglD mutants were restored by complementation in trans. In conclusion, the IglC, IglD, and MglA proteins each directly or indirectly critically contribute to the virulence of F. tularensis LVS, including its intracellular replication, cytoplasmic escape, and inhibition of acidification of the phagosomes.

  • 13. Cerveny, Lukas
    et al.
    Straskova, Adela
    Dankova, Vera
    Hartlova, Anetta
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Ceckova, Martina
    Staud, Frantisek
    Stulik, Jiri
    Tetratricopeptide Repeat Motifs in the World of Bacterial Pathogens: Role in Virulence Mechanisms2013Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 81, nr 3, s. 629-635Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The tetratricopeptide repeat (TPR) structural motif is known to occur in a wide variety of proteins present in prokaryotic and eukaryotic organisms. The TPR motif represents an elegant module for the assembly of various multiprotein complexes, and thus, TPR-containing proteins often play roles in vital cell processes. As the TPR profile is well defined, the complete TPR protein repertoire of a bacterium with a known genomic sequence can be predicted. This provides a tremendous opportunity for investigators to identify new TPR-containing proteins and study them in detail. In the past decade, TPR-containing proteins of bacterial pathogens have been reported to be directly related to virulence-associated functions. In this minireview, we summarize the current knowledge of the TPR-containing proteins involved in virulence mechanisms of bacterial pathogens while high-lighting the importance of TPR motifs for the proper functioning of class II chaperones of a type III secretion system in the pathogenesis of Yersinia, Pseudomonas, and Shigella.

  • 14.
    Danielsson Niemi, Liza
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Johansson, Ingegerd
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Salivary statherin peptide-binding epitopes of commensal and potentially infectious Actinomyces spp. delineated by a hybrid peptide construct2004Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 72, nr 2, s. 782-787Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Adhesion of microorganisms to host receptor molecules such as salivary statherin molecules is a common event in oral microbial colonization. Here we used a hybrid peptide construct (with both a hydroxyapatite-binding portion and a test peptide portion) to map the interaction of Actinomyces species (and Candida albicans) with statherin. Adhesion to hybrid peptides and truncated statherin variants revealed three binding types, types I to III. (i) Type I strains of rat, hamster, and human infection origins bound C-terminal-derived QQYTF and PYQPQY peptides. The QQYTF peptide inhibited statherin binding for some strains but not for others. (ii) Type II strains of human and monkey tooth origins bound middle-region-derived YQPVPE and QPLYPQ peptides. Neither strain was inhibited by soluble peptides. (iii) Type III strains of human infection origins (and C. albicans) did not bind to either statherin-derived peptides or truncated statherin. Moreover, the type I strains inhibited by QQYTF were also inhibited by TF and QAATF peptides and were detached from statherin by the same peptides. In conclusion, it is suggested that commensal and potentially infectious microorganisms bind middle or C-terminal statherin differently and that other microbes might require discontinuous epitopes.

  • 15.
    Drobni, Mirva
    et al.
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Li, Tong
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Krüger, Carina
    Loimaranta, Vuokko
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Kilian, Mogens
    Hammarström, Lennart
    Jörnvall, Hans
    Bergman, Tomas
    Strömberg, Nicklas
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Host-derived pentapeptide affecting adhesion, proliferation, and local pH in biofilm communities composed of Streptococcus and Actinomyces species.2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 11, s. 6293-6299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordonii. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif and selectively stimulated oral colonization of this organism in a rat model in vivo. In contrast, the growth of Streptococcus mutans, implicated in caries, was not affected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated the pH increase (i.e., ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PRP degradation and Arg catabolism, whereas cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition, and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 of 10 strains) but not of S. gordonii (n=5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordonii to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacterium interaction in which a host peptide released by bacterial proteolysis affects key properties in biofilm formation.

  • 16.
    Drobni, Mirva
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Li, Tong
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Krüger, Karina
    Loimaranta, Vuokko
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Kilian, Mogens
    Hammarström, Lennart
    Jörnvall, Hans
    Bergman, Tomas
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    A host-derived pentapeptide enhancing host-bacteria commensalisms and communication2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 11, s. 6293-6299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordond. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif and selectively stimulated oral colonization of this organism in a rat model in vivo. In contrast, the growth of Streptococcus mutans, implicated in caries, was not affected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated the pH increase (i.e., ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PR-P degradation and Arg catabolism, whereas cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition, and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 of 10 strains) but not of S. gordonii (n = 5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordond to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacterium interaction in which a host peptide released by bacterial proteolysis affects key properties in biofilm formation.

  • 17. Dörr, Tobias
    et al.
    Möll, Andrea
    Chao, Michael C.
    Cava, Felipe
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Lam, Hubert
    Davis, Brigid M.
    Waldor, Matthew K.
    Differential Requirement for PBP1a and PBP1b in In Vivo and In Vitro Fitness of Vibrio cholerae2014Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 82, nr 5, s. 2115-2124Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the roles of the Vibrio cholerae high-molecular-weight bifunctional penicillin binding proteins, PBP1a and PBP1b, in the fitness of this enteric pathogen. Using a screen for synthetic lethality, we found that the V. cholerae PBP1a and PBP1b proteins, like their Escherichia coli homologues, are each essential in the absence of the other and in the absence of the other's putative activator, the outer membrane lipoproteins LpoA and LpoB, respectively. Comparative analyses of V. cholerae mutants suggest that PBP1a/LpoA of V. cholerae play a more prominent role in generating and/or maintaining the pathogen's cell wall than PBP1b/LpoB.V. cholerae lacking PBP1b or LpoB exhibited wild-type growth under all conditions tested. In contrast, V. cholerae lacking PBP1a or LpoA exhibited growth deficiencies in minimal medium, in the presence of deoxycholate and bile, and in competition assays with wild-type cells both in vitro and in the infant mouse small intestine. PBP1a pathway mutants are particularly impaired in stationary phase, which renders them sensitive to a product(s) present in supernatants from stationary-phase wild-type cells. The marked competitive defect of the PBP1a pathway mutants in vivo was largely absent when exponential-phase cells rather than stationary-phase cells were used to inoculate suckling mice. Thus, at least for V. cholerae PBP1a pathway mutants, the growth phase of the inoculum is a key modulator of infectivity.

  • 18. Elmwall, Jonas
    et al.
    Kwiecinski, Jakub
    Na, Manli
    Ali, Abukar Ahmed
    Osla, Veronica
    Shaw, Lindsey N.
    Wang, Wanzhong
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap, Patologi.
    Sävman, Karin
    Josefsson, Elisabet
    Bylund, Johan
    Jin, Tao
    Welin, Amanda
    Karlsson, Anna
    Galectin-3 Is a Target for Proteases Involved in the Virulence of Staphylococcus aureus2017Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 85, nr 7, artikel-id e00177-17Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Staphylococcus aureus is a major cause of skin and soft tissue infection. The bacterium expresses four major proteases that are emerging as virulence factors: aureolysin (Aur), V8 protease (SspA), staphopain A (ScpA), and staphopain B (SspB). We hypothesized that human galectin-3, a beta-galactoside-binding lectin involved in immune regulation and antimicrobial defense, is a target for these proteases and that proteolysis of galectin-3 is a novel immune evasion mechanism. Indeed, supernatants from laboratory strains and clinical isolates of S. aureus caused galectin-3 degradation. Similar proteolytic capacities were found in Staphylococcus epidermidis isolates but not in Staphylococcus saprophyticus. Galectin-3-induced activation of the neutrophil NADPH oxidase was abrogated by bacterium-derived proteolysis of galectin-3, and SspB was identified as the major protease responsible. The impact of galectin-3 and protease expression on S. aureus virulence was studied in a murine skin infection model. In galectin-3 (+)/(+) mice, SspB-expressing S. aureus caused larger lesions and resulted in higher bacterial loads than protease-lacking bacteria. No such difference in bacterial load or lesion size was detected in galectin-3 (+)/(+) mice, which overall showed smaller lesion sizes than the galectin-3 (+)/(+) animals. In conclusion, the staphylococcal protease SspB inactivates galectin-3, abrogating its stimulation of oxygen radical production in human neutrophils and increasing tissue damage during skin infection.

  • 19.
    Eriksson, Anna
    et al.
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Biomedicinsk laboratorievetenskap.
    Norgren, Mari
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Biomedicinsk laboratorievetenskap.
    Cleavage of antigen-bound immunoglobulin G by SpeB contributes to streptococcal persistence in opsonizing blood.2003Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 71, nr 1, s. 211-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Group A streptococci (GAS) express a superantigen, SpeB, having cysteine protease activity. SpeB exhibits several properties that might contribute to virulence, the most recently discovered being the ability to cleave immunoglobulin G (IgG) in a manner similar to that of papain. In the present study, we confirmed this latter finding and found that the irreversible inhibition of SpeB protease activity completely abolishes IgG cleavage. SpeB cleavage of IgG was not species restricted since SpeB cleaved both human, rabbit, and mouse IgG. In order to investigate the nature of the SpeB cleavage of IgG, antibodies were immobilized prior to exposure to SpeB, either by unspecific binding of the Fc to GAS surface proteins or by antigen-specific binding. Analysis of the IgG molecules by SDS-PAGE showed that SpeB could cleave antigen-bound antibodies, while the IgG bound to IgG-binding proteins was protected from cleavage. In a phagocytosis assay using whole blood, the M49 GAS strain NZ131 showed a significantly higher survival than its isogenic speB mutant. Furthermore, the addition of extracellular supernatant derived from an overnight culture of native NZ131 increased the survival of its isogenic speB derivative. This indicates that SpeB's ability to cleave off the Fc part of antigen-bound IgG contributes to GAS escape from opsonophagocytosis while not interfering with the formation of a host-like coat by unspecific IgG binding.

  • 20.
    Esberg, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Löfgren-Burström, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk biovetenskap, Patologi.
    Öhman, Ulla
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Strömberg, Nicklas
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Kariologi.
    Host and bacterial phenotype variation in adhesion of streptococcus mutans to matched human hosts2012Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 80, nr 11, s. 3869-3879Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The commensal pathogen Streptococcus mutans uses AgI/II adhesins to adhere to gp340 adsorbed on teeth. Here we analyzed isolates of S. mutans (n = 70 isolates) from caries and caries-free human extremes (n = 19 subjects) by multilocus sequence typing (MLST), AgI/II full-length gene sequencing, and adhesion to parotid saliva matched from the strain donors (nested from a case-control sample of defined gp340 and acidic proline-rich protein [PRP] profiles). The concatenated MLST as well as AgI/II gene sequences showed unique sequence types between, and identical types within, the subjects. The matched adhesion levels ranged widely (40% adhesion range), from low to moderate to high, between subjects but were similar within subjects (or sequence types). In contrast, the adhesion avidity of the strains was narrow, normally distributed for high, moderate, or low adhesion reference saliva or pure gp340 regardless of the sequence type. The adhesion of S. mutans Ingbritt and matched isolates and saliva samples correlated (r = 0.929), suggesting that the host specify about four-fifths (r(2) = 0.86) of the variation in matched adhesion. Half of the variation in S. mutans Ingbritt adhesion to saliva from the caries cases-controls (n = 218) was explained by the primary gp340 receptor and PRP coreceptor composition. The isolates also varied, although less so, in adhesion to standardized saliva (18% adhesion range) and clustered into three major AgI/II groups (groups A, B-1, and B-2) due to two variable V-region segments and diverse AgI/II sequence types due to a set of single-amino-acid substitutions. Isolates with AgI/II type A versus types B-1 and B-2 tended to differ in gp340 binding avidity and qualitative adhesion profiles for saliva gp340 phenotypes. In conclusion, the host saliva phenotype plays a more prominent role in S. mutans adhesion than anticipated previously.

  • 21.
    Fahlgren, Anna
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Avican, Kemal
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Westermark, Linda
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Nordfelth, Roland
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Fällman, Maria
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Colonization of cecum is important for development of persistent infection by Yersinia pseudotuberculosis2014Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 82, nr 8, s. 3471-3482Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Yersiniosis is a human disease caused by the bacterium Yersinia pseudotuberculosis or Yersinia enterocolitica. The infection is usually resolved but can lead to postinfectious sequelae, including reactive arthritis and erythema nodosum. The commonly used Yersinia mouse infection model mimics acute infection in humans to some extent but leads to systemic infection and eventual death. Here, we analyzed sublethal infection doses of Y. pseudotuberculosis in mice in real time using bioluminescent imaging and found that infections using these lower doses result in extended periods of asymptomatic infections in a fraction of mice. In a search for the site for bacterial persistence, we found that the cecum was the primary colonization site and was the site where the organism resided during a 115-day infection period. Persistent infection was accompanied by sustained fecal shedding of cultivable bacteria. Cecal patches were identified as the primary site for cecal colonization during persistence. Y. pseudotuberculosis bacteria were present in inflammatory lesions, in localized foci, or as single cells and also in neutrophil exudates in the cecal lumen. The chronically colonized cecum may serve as a reservoir for dissemination of infection to extraintestinal sites, and a chronic inflammatory state may trigger the onset of postinfectious sequelae. This novel mouse model for bacterial persistence in cecum has potential as an investigative tool to unveil a deeper understanding of bacterial adaptation and host immune defense mechanisms during persistent infection.

  • 22.
    Forslund, Anna-Lena
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Kuoppa, Kerstin
    FOI Swedish Defence Research Agency, Division of CBRN Defence and Security.
    Meibom, Karin L.
    Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades; INSERM, U570, Unit of Pathogenesis of Systemic Infections.
    Alkhuder, Khaled
    Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades; INSERM, U570, Unit of Pathogenesis of Systemic Infections.
    Dubail, Iharilalao
    Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades; INSERM, U570, Unit of Pathogenesis of Systemic Infections.
    Dupuis, Marion
    Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades; INSERM, U570, Unit of Pathogenesis of Systemic Infections.
    Charbit, Alain
    Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades; INSERM, U570, Unit of Pathogenesis of Systemic Infections.
    Hfq, a novel pleiotropic regulator of virulence-associated genes in Francisella tularensis2009Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 77, nr 5, s. 1866-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is a highly infectious pathogen that infects animals and humans, causing tularemia. The ability to replicate within macrophages is central for virulence and relies on expression of genes located in the Francisella pathogenicity island (FPI), as well as expression of other genes. Regulation of FPI-encoded virulence gene expression in F. tularensis involves at least four regulatory proteins and is not fully understood. Here we studied the RNA-binding protein Hfq in F. tularensis and particularly the role that it plays as a global regulator of gene expression in stress tolerance and pathogenesis. We demonstrate that Hfq promotes resistance to several cellular stresses (including osmotic and membrane stresses). Furthermore, we show that Hfq is important for the ability of the F. tularensis vaccine strain LVS to induce disease and persist in organs of infected mice. We also demonstrate that Hfq is important for stress tolerance and full virulence in a virulent clinical isolate of F. tularensis, FSC200. Finally, microarray analyses revealed that Hfq regulates expression of numerous genes, including genes located in the FPI. Strikingly, Hfq negatively regulates only one of two divergently expressed putative operons in the FPI, in contrast to the other known regulators, which regulate the entire FPI. Hfq thus appears to be a new pleiotropic regulator of virulence in F. tularensis, acting mostly as a repressor, in contrast to the other regulators identified so far. Moreover, the results obtained suggest a novel regulatory mechanism for a subset of FPI genes.

  • 23. Frick, Julia S
    et al.
    Fink, Kerstin
    Kahl, Frauke
    Niemiec, Maria J
    Quitadamo, Matteo
    Schenk, Katrin
    Autenrieth, Ingo B
    Identification of commensal bacterial strains that modulate Yersinia enterocolitica and dextran sodium sulfate-induced inflammatory responses: implications for the development of probiotics.2007Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 75, nr 7, s. 3490-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An increasing body of evidence suggests that probiotic bacteria are effective in the treatment of enteric infections, although the molecular basis of this activity remains elusive. To identify putative probiotics, we tested commensal bacteria in terms of their toxicity, invasiveness, inhibition of Yersinia-induced inflammation in vitro and in vivo, and modulation of dextran sodium sulfate (DSS)-induced colitis in mice. The commensal bacteria Escherichia coli, Bifidobacterium adolescentis, Bacteroides vulgatus, Bacteroides distasonis, and Streptococcus salivarius were screened for adhesion to, invasion of, and toxicity for host epithelial cells (EC), and the strains were tested for their ability to inhibit Y. enterocolitica-induced NF-kappaB activation. Additionally, B. adolescentis was administered to mice orally infected with Y. enterocolitica and to mice with mucosae impaired by DSS treatment. None of the commensal bacteria tested was toxic for or invaded the EC. B. adolescentis, B. distasonis, B. vulgatus, and S. salivarius inhibited the Y. enterocolitica-induced NF-kappaB activation and interleukin-8 production in EC. In line with these findings, B. adolescentis-fed mice had significantly lower results for mean pathogen burden in the visceral organs, intestinal tumor necrosis factor alpha mRNA expression, and loss of body weight upon oral infection with Y. enterocolitica. In addition, the administration of B. adolescentis decelerated inflammation upon DSS treatment in mice. We suggest that our approach might help to identify new probiotics to be used for the treatment of inflammatory and infectious gastrointestinal disorders.

  • 24.
    Garbom, Sara
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forsberg, Ake
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Wolf-Watz, Hans
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Kihlberg, Britt-Marie
    Identification of novel virulence-associated genes via genome analysis of hypothetical genes.2004Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 72, nr 3, s. 1333-1340Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sequencing of bacterial genomes has opened new perspectives for identification of targets for treatment of infectious diseases. We have identified a set of novel virulence-associated genes (vag genes) by comparing the genome sequences of six human pathogens that are known to cause persistent or chronic infections in humans: Yersinia pestis, Neisseria gonorrhoeae, Helicobacter pylori, Borrelia burgdorferi, Streptococcus pneumoniae, and Treponema pallidum. This comparison was limited to genes annotated as hypothetical in the T. pallidum genome project. Seventeen genes with unknown functions were found to be conserved among these pathogens. Insertional inactivation of 14 of these genes generated nine mutants that were attenuated for virulence in a mouse infection model. Out of these nine genes, five were found to be specifically associated with virulence in mice as demonstrated by infection with Yersinia pseudotuberculosis in-frame deletion mutants. In addition, these five vag genes were essential only in vivo, since all the mutants were able to grow in vitro. These genes are broadly conserved among bacteria. Therefore, we propose that the corresponding vag gene products may constitute novel targets for antimicrobial therapy and that some vag mutants could serve as carrier strains for live vaccines.

  • 25.
    Gekara, Nelson O
    et al.
    Molecular Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany.
    Groebe, Lothar
    Viegas, Nuno
    Weiss, Siegfried
    Listeria monocytogenes desensitizes immune cells to subsequent Ca2+ signaling via listeriolysin O-induced depletion of intracellular Ca2+ stores.2008Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, nr 2, s. 857-862Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Listeriolysin O (LLO), the pore-forming toxin of Listeria monocytogenes, is a prototype of the cholesterol-dependent cytolysins (CDCs) secreted by several pathogenic and nonpathogenic gram-positive bacteria. In addition to mediating the escape of the bacterium into the cytosol, this toxin is generally believed to be a central player in host-pathogen interactions during L. monocytogenes infection. LLO triggers the influx of Ca(2+) into host cells as well as the release of Ca(2+) from intracellular stores. Thus, many of the cellular responses induced by LLO are related to calcium signaling. Interestingly, in this study, we report that prolonged exposure to LLO desensitizes cells to Ca(2+) mobilization upon subsequent stimulations with LLO. Cells preexposed to LLO-positive L. monocytogenes but not to the LLO-deficient Deltahly mutant were found to be highly refractory to Ca(2+) induction in response to receptor-mediated stimulation. Such cells also exhibited diminished Ca(2+) signals in response to stimulation with LLO and thapsigargin. The presented results suggest that this phenomenon is due to the depletion of intracellular Ca(2+) stores. The ability of LLO to desensitize immune cells provides a significant hint about the possible role played by CDCs in the evasion of the immune system by bacterial pathogens.

  • 26. Hajjar, Adeline M
    et al.
    Harvey, Megan D
    Shaffer, Scott A
    Goodlett, David R
    Sjöstedt, Anders
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Edebro, Helen
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Forsman, Mats
    FOI, Umeå (Swedish Defence Research Agency).
    Byström, Mona
    Pelletier, Mark
    Wilson, Christopher B
    Miller, Samuel I
    Skerrett, Shawn J
    Ernst, Robert K
    Lack of in vitro and in vivo recognition of Francisella tularensis subspecies lipopolysaccharide by Toll-like receptors.2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 12, s. 6730-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is an intracellular gram-negative bacterium that is highly infectious and potentially lethal. Several subspecies exist of varying pathogenicity. Infection by only a few organisms is sufficient to cause disease depending on the model system. Lipopolysaccharide (LPS) of gram-negative bacteria is generally recognized by Toll-like receptor 4 (TLR4)/MD-2 and induces a strong proinflammatory response. Examination of human clinical F. tularensis isolates revealed that human virulent type A and type B strains produced lipid A of similar structure to the nonhuman model pathogen of mice, Francisella novicida. F. novicida LPS or lipid A is neither stimulatory nor an antagonist for human and murine cells through TLR4 or TLR2. It does not appear to interact with TLR4 or MD-2, as it is not an antagonist to other stimulatory LPS. Consistent with these observations, aerosolization of F. novicida LPS or whole bacteria induced no inflammatory response in mice. These results suggest that poor innate recognition of F. tularensis allows the bacterium to evade early recognition by the host innate immune system to promote its pathogenesis for mammals.

  • 27. Hansen, Lori M.
    et al.
    Gideonsson, Pär
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Canfield, Don R.
    Borén, Thomas
    Umeå universitet, Medicinska fakulteten, Institutionen för medicinsk kemi och biofysik.
    Solnick, Jay V.
    Dynamic Expression of the BabA Adhesin and Its BabB Paralog during Helicobacter pylori Infection in Rhesus Macaques2017Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 85, nr 6, artikel-id e00094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Most Helicobacter pylori strains express the BabA adhesin, which binds to ABO/Leb blood group antigens on gastric mucin and epithelial cells and is found more commonly in strains that cause peptic ulcers or gastric cancer, rather than asymptomatic infection. We and others have previously reported that in mice, gerbils, and rhesus macaques, expression of babA is lost, either by phase variation or by gene conversion, in which the babB paralog recombines into the babA locus. The functional significance of loss of babA expression is unknown. Here we report that in rhesus monkeys, there is independent selective pressure for loss of babA and for overexpression of BabB, which confers a fitness advantage. Surprisingly, loss of babA by phase variation or gene conversion is not dependent on the capacity of BabA protein to bind Leb, which suggests that it may have other, unrecognized functions. These findings have implications for the role of outer membrane protein diversity in persistent H. pylori infection.

  • 28. Hartley, M G
    et al.
    Green, M
    Choules, G
    Rogers, D
    Rees, D G C
    Newstead, S
    Sjostedt, Anders
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Titball, R W
    Protection afforded by heat shock protein 60 from Francisella tularensis is due to copurified lipopolysaccharide.2004Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 72, nr 7, s. 4109-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heat shock proteins (Hsps) have attracted significant attention as protective antigens against a range of diseases caused by bacterial pathogens. However, more recently there have been suggestions that the protective response is due to the presence of peptide components other than Hsps. We have shown that mice that had been immunized with purified heat shock protein 60 (Hsp60) isolated from Francisella tularensis were protected against a subsequent challenge with some strains of the bacterium. However, this protection appeared to be due to trace amounts of lipopolysaccharide, which were too low to be detected by using the Limulus amoebocyte lysate assay. This finding raises the possibility that the protection afforded by other bacterial Hsp60 proteins may be due to trace quantities of polysaccharide antigens carried by and acting in conjunction with the Hsps.

  • 29. Hazlett, Karsten RO
    et al.
    Caldon, Seth D
    McArthur, Debbie G
    Cirillo, Kerry A
    Kirimanjeswara, Girish S
    Magguilli, Micheal L
    Malik, Meenakshi
    Shah, Aaloki
    Broderick, Scott
    Golovliov, Igor
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Metzger, Dennis W
    Rajan, Krishna
    Sellati, Timothy J
    Loegering, Daniel J
    Adaptation of Francisella tularensis to the mammalian environment is governed by cues which can be mimicked in vitro2008Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, nr 10, s. 4479-4488Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intracellular bacterium Francisella tularensis survives in mammals, arthropods, and freshwater amoeba. It was previously established that the conventional media used for in vitro propagation of this microbe do not yield bacteria that mimic those harvested from infected mammals; whether these in vitro-cultivated bacteria resemble arthropod- or amoeba-adapted Francisella is unknown. As a foundation for our goal of identifying F. tularensis outer membrane proteins which are expressed during mammalian infection, we first sought to identify in vitro cultivation conditions that induce the bacterium's infection-derived phenotype. We compared Francisella LVS grown in brain heart infusion broth (BHI; a standard microbiological medium rarely used in Francisella research) to that grown in Mueller-Hinton broth (MHB; the most widely used F. tularensis medium, used here as a negative control) and macrophages (a natural host cell, used here as a positive control). BHI- and macrophage-grown F. tularensis cells showed similar expression of MglA-dependent and MglA-independent proteins; expression of the MglA-dependent proteins was repressed by the supraphysiological levels of free amino acids present in MHB. We observed that during macrophage infection, protein expression by intracellular bacteria differed from that by extracellular bacteria; BHI-grown bacteria mirrored the latter, while MHB-grown bacteria resembled neither. Naïve macrophages responding to BHI- and macrophage-grown bacteria produced markedly lower levels of proinflammatory mediators than those in cells exposed to MHB-grown bacteria. In contrast to MHB-grown bacteria, BHI-grown bacteria showed minimal delay during intracellular replication. Cumulatively, our findings provide compelling evidence that growth in BHI yields bacteria which recapitulate the phenotype of Francisella organisms that have emerged from macrophages.

  • 30. Holmgren, J
    et al.
    Svennerholm, A M
    Gothefors, Leif
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Pediatrik.
    Jertborn, M
    Stoll, B
    Enterotoxigenic Escherichia coli diarrhea in an endemic area prepares the intestine for an anamnestic immunoglobulin A antitoxin response to oral cholera B subunit vaccination.1988Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 56, nr 1, s. 230-3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examined whether infection with enterotoxigenic Escherichia coli (ETEC) producing the heat-labile enterotoxin (LT) can prime the gut immune system to respond more efficiently to the immunologically related cholera B subunit component of a recently developed oral B subunit-whole-cell cholera vaccine (B-WCV). Nine Bangladeshi adults who had been hospitalized for watery diarrhea caused by LT-producing ETEC were given a single oral immunization with B-WCV on day 28 after hospital admission. The vaccine preparation used was adjusted to contain a lower-than-usual dose of B subunit, which had been found in previous studies to elicit a significant gut mucosal immunoglobulin A antitoxin response mainly in individuals with previous toxin-specific priming of their gut immune system. For comparison, nine patients convalescing from severe cholera disease and eight healthy subjects with no recent history of either cholera or ETEC infection were given the same oral vaccination with B-WCV. Vaccination in the ETEC convalescents induced an immunoglobulin A antitoxin response in intestinal lavage fluid which was comparable with that in the vaccinated cholera convalescents and superior to that in the vaccinated, previously uninfected controls. By contrast, only the cholera patients responded with anamnestic-type anti-cholera lipopolysaccharide antibody titer rises in the intestine after vaccination. These data support the specificity of the anamnestic anti-cholera toxin response in the ETEC patients after vaccination with cholera B-WCV.

  • 31.
    Holmström, Anna
    et al.
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Rosqvist, Roland
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Wolf-Watz, Hans
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Mikrobiologi.
    Virulence plasmid-encoded YopK is essential for Yersinia pseudotuberculosis to cause systemic infection in mice.1995Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 63, nr 6, s. 2269-2276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The virulence plasmid common to pathogenic Yersinia species encodes a number of secreted proteins denoted Yops (Yersinia outer proteins). Here, we identify and characterize a novel plasmid-encoded virulence determinant of Yersinia pseudotuberculosis, YopK. The yopK gene was found to be conserved among the three pathogenic Yersinia species and to be homologous to the previously described yopQ and yopK genes of Y. enterocolitica and Y. pestis, respectively. Similar to the other Yops, YopK expression and secretion were shown to be regulated by temperature and by the extracellular Ca2+ concentration; thus, yopK is part of the yop regulon. In addition, YopK secretion was mediated by the specific Yop secretion system. In Y. pseudotuberculosis, YopK was shown neither to have a role in this bacterium's ability to resist phagocytosis by macrophages nor to cause cytotoxicity in HeLa cells. YopK was, however, shown to be required for the bacterium to cause a systemic infection in both intraperitoneally and orally infected mice. Characterization of the infection kinetics showed that, similarly to the wild-type strain, the yopK mutant strain colonized and persisted in the Peyer's patches of orally infected mice. A yopE mutant which is impaired in cytotoxicity and in antiphagocytosis was, however, found to be rapidly cleared from these lymphoid organs. Neither the yopK nor the yopE mutant strain could overcome the primary host defense and reach the spleen. This finding implies that YopK acts at a different level during the infections process than the antiphagocytic YopE cytotoxin does.

  • 32.
    Isaksson, Elin L
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Aili, Margareta
    Fahlgren, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Carlsson, Sara E
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Rosqvist, Roland
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Wolf-Watz, Hans
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    The membrane localization domain is required for intracellular localization and autoregulation of YopE in Yersinia pseudotuberculosis.2009Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 77, nr 11, s. 4740-4749Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent work has shown that a domain of YopE of Yersinia pseudotuberculosis ranging from amino acids 54 to 75 (R. Krall, Y. Zhang, and J. T. Barbieri, J. Biol. Chem. 279:2747-2753, 2004) is required for proper localization of YopE after ectopic expression in eukaryotic cells. This domain, called the membrane localization domain (MLD), has not been extensively studied in Yersinia. Therefore, an in cis MLD deletion mutant of YopE was created in Y. pseudotuberculosis. The mutant was found to secrete and translocate YopE at wild-type levels. However, the mutant was defective in the autoregulation of YopE expression after the infection of HeLa cells. Although the mutant translocated YopE at wild-type levels, it showed a delayed HeLa cell cytotoxicity. This delay was not caused by a change in GTPase activating protein (GAP) activity, since the mutant showed wild-type YopE GAP activity toward Rac1 and RhoA. The MLD mutant displayed a changed intracellular localization pattern of YopE in HeLa cells after infection, and the YopEDeltaMLD protein was found to be dispersed within the whole cell, including the nucleus. In contrast, wild-type YopE was found to localize to the perinuclear region of the cell and was not found in the nucleus. In addition, the yopEDeltaMLD mutant was avirulent. Our results suggest that YopE must target proteins other than RhoA and Rac1 and that the MLD is required for the proper targeting and hence virulence of YopE during infection. Our results raise the question whether YopE is a regulatory protein or a "true" virulence effector protein.

  • 33.
    Ishikawa, Takahiko
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Sabharwal, Dharmesh
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Bröms, Jeanette
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Milton, Debra L
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Pathoadaptive conditional regulation of the type VI secretion system in Vibrio cholerae O1 strains2012Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 80, nr 2, s. 575-584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The most recently discovered secretion pathway in gram-negative bacteria, the type VI secretion system (T6SS), is present in many species and is considered important for the survival of non-O1 non-O139 Vibrio cholerae in aquatic environments. Until now, it was not known whether there is a functionally active T6SS in wild-type V. cholerae O1 strains, the cause of cholera disease in humans. Here, we demonstrate the presence of a functionally active T6SS in wild-type V. cholerae O1 strains, as evidenced by the secretion of the T6SS substrate Hcp, which required several gene products encoded within the putative vas gene cluster. Our analyses showed that the T6SS of wild-type V. cholerae O1 strain A1552 was functionally activated when the bacteria were grown under high-osmolarity conditions. The T6SS was also active when the bacteria were grown under low temperature (23°C), suggesting that the system may be important for the survival of the bacterium in the environment. A test of the interbacterial virulence of V. cholerae strain A1552 against an Escherichia coli K-12 strain showed that it was strongly enhanced under high osmolarity and that it depended on the hcp genes. Interestingly, we found that the newly recognized osmoregulatory protein OscR plays a role in the regulation of T6SS gene expression and secretion of Hcp from V. cholerae O1 strains.

  • 34. Jakubovics, NS
    et al.
    Kerrigan, SW
    Nobbs, AH
    Strömberg, Nicklas
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    van Dolleweerd, CJ
    Cox, DM
    Kelly, CG
    Jenkinson, HF
    Functions of cell surface-anchored antigen I/II family and Hsa polypeptides in interactions of Streptococcus gordonii with host receptors.2005Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 73, nr 10, s. 6629-6638Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Streptococcus gordonii colonizes multiple sites within the human oral cavity. This colonization depends upon the initial interactions of streptococcal adhesins with host receptors. The adhesins that bind salivary agglutinin glycoprotein (gp340) and human cell surface receptors include the antigen I/II (AgI/II) family polypeptides SspA and SspB and a sialic acid-binding surface protein designated Hsa or GspB. In this study we determined the relative functions of the AgI/II polypeptides and Hsa in interactions of S. gordonii DL1 (Challis) with host receptors. For an isogenic mutant with the sspA and sspB genes deleted the levels of adhesion to surface-immobilized gp340 were reduced 40%, while deletion of the hsa gene alone resulted in >80% inhibition of bacterial cell adhesion to gp340. Adhesion of S. gordonii DL1 cells to gp340 was sialidase sensitive, verifying that Hsa has a major role in mediating sialic acid-specific adhesion to gp340. Conversely, aggregation of S. gordonii cells by fluid-phase gp340 was not affected by deletion of hsa but was eliminated by deletion of the sspA and sspB genes. Deletion of the AgI/II polypeptide genes had no measurable effect on hsa mRNA levels or Hsa surface protein expression, and deletion of hsa did not affect AgI/II polypeptide expression. Further analysis of mutant phenotypes showed that the Hsa and AgI/II proteins mediated adhesion of S. gordonii DL1 to human HEp-2 epithelial cells. Hsa was also a principal streptococcal cell surface component promoting adhesion of human platelets to immobilized streptococci, but Hsa and AgI/II polypeptides acted in concert in mediating streptococcal cell-platelet aggregation. The results suggest that Hsa directs primary adhesion events for S. gordonii DL1 (Challis) with immobilized gp340, epithelial cells, and platelets. AgI/II polypeptides direct gp340-mediated aggregation, facilitate multimodal interactions necessary for platelet aggregation, and modulate S. gordonii-host engagements into biologically productive phenomena.

  • 35. Jonsson, Maria
    et al.
    Noppa, L
    Barbour, A G
    Bergström, S
    Heterogeneity of outer membrane proteins in Borrelia burgdorferi: comparison of osp operons of three isolates of different geographic origins.1992Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 60, nr 5, s. 1845-53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biochemical and immunochemical studies of the outer membrane proteins of Borrelia burgdorferi have shown that the OspA and OspB proteins from strains of different geographic origins may differ considerably in their reactivities with monoclonal antibodies and in their apparent molecular weights. To further characterize this variation in Osp proteins between strains, the osp operons and deduced translation products from two strains, one from Sweden (ACAI) and one from eastern Russia (Ip90), were studied. Polyacrylamide gel electrophoresis and Western blot (immunoblot) analyses confirmed differences between ACAI, Ip90, and the North American strain B31 in their Osp proteins. The sequences of the ospA and ospB genes of ACAI and Ip90 were compared with that of the previously studied osp operon of B31 (S. Bergström, V. G. Bundoc, and A. G. Barbour, Mol. Microbiol. 3:479-486, 1989). The osp genes of ACAI and Ip90, like the corresponding genes of B31, were found on plasmids with apparent sizes of about 50 kb and are cotranscribed as a single unit. Pairwise comparisons of the nucleotide sequences revealed that the ospA genes of ACAI and Ip90 were 85 and 86% identical, respectively, to the ospA gene of strain B31 and 86% identical to each other. The ospB sequences of these two strains were 79% identical to the ospB gene of B31 and 81% identical to each other. There was significantly greater similarity between the ospA genes of the three different strains than there was between the ospA and ospB genes within each strain. These studies suggest that the duplication of osp genes in B. burgdorferi occurred before the geographical dispersion of strains represented by ACAI, Ip90, and B31.

  • 36.
    Kelk, Peyman
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Parodontologi.
    Claesson, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Hänström, L
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Parodontologi.
    Lerner, Ulf
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral cellbiologi.
    Kalfas, S
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Parodontologi.
    Abundant secretion of bioactive interleukin-1beta by human macrophages induced by Actinobacillus actinomycetemcomitans leukotoxin2005Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 73, nr 1, s. 453-458Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actinobacillus actinomycetemcomitans produces a leukotoxin that selectively kills human leukocytes. Recently, we reported that macrophages are highly sensitive to leukotoxin and that their lysis involves activation of caspase 1. In this study, we show that leukotoxin also induces the production and release of proinflammatory cytokines from human macrophages. The macrophages were challenged with leukotoxin or lipopolysaccharide (LPS) from A. actinomycetemcomitans or LPS from Escherichia coli, and the production and secretion of interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha (TNF-alpha) were determined at the mRNA and protein levels by reverse transcription-PCR and enzyme-linked immunosorbent assay, respectively. Leukotoxin (1 to 30 ng/ml) induced abundant production and secretion of IL-1beta, while the effects on IL-6 and TNF-alpha production were limited. Leukotoxin (1 ng/ml) caused a 10-times-higher release of IL-1beta than did LPS (100 ng/ml). The secreted IL-1beta was mainly the bioactive 17-kDa protein. At higher concentrations (>30 ng/ml), leukotoxin caused secretion of mainly inactive cytokine, the 31-kDa pro-IL-1beta. The presence of specific antibodies to IL-1beta or of a caspase 1 inhibitor blocked the secretion and production of the cytokine. Supernatants of leukotoxin-challenged macrophages stimulated bone resorption when tested in a mouse calvarial model. The activity could be blocked by an IL-1 receptor antagonist or specific antibodies to IL-1beta. We concluded that A. actinomycetemcomitans leukotoxin can trigger abundant production and secretion of bioactive IL-1beta by human macrophages, which is mediated by activation of caspase 1.

  • 37.
    Kelk, Peyman
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Parodontologi.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Parodontologi.
    Claesson, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Hänström, L
    Kalfas, S
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Oral mikrobiologi.
    Caspase 1 involvement in human monocyte lysis induced by Actinobacillus actinomycetemcomitans leukotoxin2003Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 71, nr 8, s. 4448-4455Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actinobacillus actinomycetemcomitans, an oral bacterium implicated in the etiology of periodontal diseases, produces a leukotoxin that selectively lyses primate neutrophils and monocytes, the major populations of defense cells in the periodontium. Though lysis requires expression of the receptor lymphocyte function-associated molecule 1 (LFA-1) on the cell surface, not all LFA-1-expressing leukocyte populations are equally susceptible to the toxin. In this study, the susceptibility of human leukocytes to leukotoxin-induced lysis is compared to their expression of LFA-1 and the activity of caspase 1. Cytolysis was determined by the activity of lactate dehydrogenase released from peripheral human leukocytes after 1-h exposure to leukotoxin. Monocytes were lysed at leukotoxin concentrations of > or = 5 ng/ml, while the corresponding values for neutrophils and lymphocytes were approximately 10 times greater. Similar LFA-1 expression was found in all susceptible cell populations irrespective of their degree of sensitivity to the toxin. Exposure of monocytes to leukotoxin increased their caspase 1 activity about fivefold within 10 to 20 min. Presence of the caspase 1 inhibitor Ac-YVAD-CMK significantly blocked the leukotoxin-induced lysis of monocytes only. At sublytic concentrations, leukotoxin induced no apoptotic activity in monocytes, as revealed by the lack of caspase 3 activation and DNA fragmentation. Monocytes are the most lysis-sensitive leukocytes for A. actinomycetemcomitans leukotoxin. Their lysis by this toxin depends on caspase 1 activation and proceeds through a process that differs from classical apoptosis.

  • 38.
    Kouokam, J Clavin
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Wai, Sun Nyunt
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Fällman, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Dobrindt, Ulrich
    Hacker, Jörg
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Active cytotoxic necrotizing factor 1 associated with outer membrane vesicles from uropathogenic Escherichia coli.2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 4, s. 2022-2030Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cytotoxic necrotizing factor type 1 (CNF1) is one of the virulence factors produced by uropathogenic Escherichia coli (UPEC). How this toxin is translocated from the bacterial cytoplasm to the surrounding environment is not well understood. Our data suggest that CNF1 may be regarded as a secreted protein, since it could be detected in culture supernatants. Furthermore, we found that CNF1 was tightly associated to outer membrane vesicles, suggesting that such vesicles play a role in the secretion of this protein. Interestingly, vesicle samples containing CNF1 could exert the effects known for this protein on HeLa cell cultures, showing that CNF1 is transported by vesicles in its active form. Taken together, our results strongly suggest that outer membrane vesicles could be a means for the bacteria to deliver CNF1 to the environment and to the infected tissue. In addition, our results indicate that the histone-like nucleoid structuring protein H-NS has a role in the downregulation of CNF1 production and that it affects the outer membrane vesicle release in UPEC strain J96.

  • 39.
    Lai, Xin-He
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Golovliov, Igor
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Fancisella tularensis induces cytopathogenicity and apaptosis in murine macrophages via a mechanism that requires intracellular bacterial multiplication2001Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 69, nr 7, s. 4691-4694Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The murine macrophage-like cell line J774.A1 ingests and allows intracellular growth of Francisella tularensis. We demonstrate that, after 24 h of infection, a pronounced cytopathogenicity resulted and the J774 cells were undergoing apoptosis. Despite this host cell apoptosis, no decrease in bacterial numbers was observed. When internalization of bacteria was prevented or intracellularly located F. tularensis bacteria were eradicated within 12 h, the progression of host cell cytopathogenicity and apoptosis was prevented.

  • 40.
    Lai, Xin-He
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Delineation of the molecular mechanisms of Francisella tularensis-induced apoptosis in murine macrophages2003Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 71, nr 8, s. 4642-4646Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is a facultative intracellular bacterium capable of inducing apoptosis in murine macrophages. Here we analyzed the pathway leading to apoptosis in the murine macrophage-like cell line J774A.1 after infection with F. tularensis strain LVS (named LVS for live vaccine strain). We obtained evidence that the infection affected the mitochondria of the macrophages, since it induced release of the mitochondrial molecule cytochrome c into the cytosol and changed the potential over the mitochondrial membrane. Moreover, activation of caspase 9 and the executioner caspase 3 was also observed in the LVS-infected J774A.1 macrophages. The activated caspase 3 degraded poly(ADP-ribose) polymerase (PARP). All of these events were observed within 9 to 12 h after the initiation of infection, and maximum degradation of a synthetic caspase 3 substrate occurred at 18 h. The internucleosomal fragmentation and PARP degradation resulting from activation of this apoptotic pathway was prevented by the caspase 3 inhibitor Z-DEVD-fmk. No involvement of caspase 1, caspase 8, Bcl-2, or Bid was observed. Thus, the F. tularensis infection induces macrophage apoptosis through a pathway partly resembling the intrinsic apoptotic pathway.

  • 41. Lakio, L
    et al.
    Paju, S
    Alfthan, G
    Tiirola, T
    Asikainen, Sirkka
    Umeå universitet, Medicinsk fakultet, Odontologi, Oral mikrobiologi.
    Pussinen, PJ
    Actinobacillus actinomycetemcomitans serotype d-specific antigen contains the O antigen of lipopolysaccharide.2003Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 71, nr 9, s. 5005-5011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actinobacillus actinomycetemcomitans is a gram-negative, facultatively anaerobic bacterium which is associated especially with aggressive forms of periodontitis. Contradictory results on the localization of the A. actinomycetemcomitans serotype-specific antigen have been reported. The aim of the present study was to characterize the A. actinomycetemcomitans serotype d-specific antigen. The antigen was isolated by affinity chromatography. The affinity column was prepared from immunoglobulin G isolated from rabbit antiserum raised against A. actinomycetemcomitans serotype d. The isolated antigen was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and silver staining, all of which revealed a ladder-like structure typical for the O antigen of lipopolysaccharide (LPS). In a displacement enzyme-linked immunosorbent assay (ELISA), the isolated antigen displaced in a concentration-dependent manner the binding of the polyclonal rabbit antiserum raised against A. actinomycetemcomitans serotype d to the competing whole-cell serotype d antigen. The isolated antigen contained LPS, and an equal concentration of LPS isolated from A. actinomycetemcomitans serotype d gave a similar displacement curve in the ELISA. In order to test the immunogenic properties of the isolated antigen, it was used to immunize a rabbit. The antiserum raised against the isolated antigen displayed specificity in Western blotting and ELISA similar to that of antibody raised against LPS isolated from A. actinomycetemcomitans serotype d. In conclusion, our results show that the A. actinomycetemcomitans serotype d-specific antigen contains the O-antigenic structure of LPS.

  • 42.
    Lavander, Moa
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Department of Medical Countermeasures, Division of NBC Defense, Swedish Defense Research Agency, SE-901 82 Umeå, Sweden.
    Ericsson, Solveig K.
    Bröms, Jeanette E
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Department of Medical Countermeasures, Division of NBC Defense, Swedish Defense Research Agency, SE-901 82 Umeå, Sweden.
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Department of Medical Countermeasures, Division of NBC Defense, Swedish Defense Research Agency, SE-901 82 Umeå, Sweden.
    The Twin Arginine Translocation System is Essential for Virulence of Yersinia pseudotuberculosis2006Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, nr 3, s. 1768-1776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Yersinia species pathogenic to humans have been extensively characterized with respect to type III secretion and its essential role in virulence. This study concerns the twin arginine translocation (Tat) pathway utilized by gram-negative bacteria to secrete folded proteins across the bacterial inner membrane into the periplasmic compartment. We have shown that the Yersinia Tat system is functional and required for motility and contributes to acid resistance. A Yersinia pseudotuberculosis mutant strain with a disrupted Tat system (tatC) was, however, not affected in in vitro growth or more susceptible to high osmolarity, oxidative stress, or high temperature, nor was it impaired in type III secretion. Interestingly, the tatC mutant was severely attenuated via both the oral and intraperitoneal routes in the systemic mouse infection model and highly impaired in colonization of lymphoid organs like Peyer's patches and the spleen. Our work highlights that Tat secretion plays a key role in the virulence of Y. pseudotuberculosis.

  • 43. Li, T
    et al.
    Bratt, P
    Jonsson, AP
    Ryberg, M
    Johansson, Ingegerd
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Griffiths, WJ
    Bergman, T
    Strömberg, Nicklas
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Possible release of an ArgGlyArgProGln pentapeptide with innate immunity properties from acidic proline-rich proteins by proteolytic activity in commensal streptococcus and actinomyces species.2000Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 68, nr 9, s. 5425-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study suggests degradation of salivary acidic proline-rich proteins (PRPs) into potential innate-immunity-like peptides by oral Streptococcus and Actinomyces species. PRP degradation paralleled cleavage of Pro-containing substrates. PRP degradation by S. gordonii strain SK12 instantly released a Pyr(1)-Pro(104)Pro(105) and a Gly(111)-Pro(149)Gln(150) peptide together with a presumed Arg(106)Gly(107)Arg(108)Pro(109)Gln(110) pentapeptide. The synthetic Arg(106)Gly(107)Arg(108)Pro(109)Gln(110) peptide desorbed bound bacteria and counteracted sucrose-induced decrease of dental plaque pH in vitro.

  • 44. Li, T
    et al.
    Johansson, Ingegerd
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Hay, DI
    Strömberg, Nicklas
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Strains of Actinomyces naeslundii and Actinomyces viscosus exhibit structurally variant fimbrial subunit proteins and bind to different peptide motifs in salivary proteins.1999Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 67, nr 5, s. 2053-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oral strains of Actinomyces spp. express type 1 fimbriae, which are composed of major FimP subunits, and bind preferentially to salivary acidic proline-rich proteins (APRPs) or to statherin. We have mapped genetic differences in the fimP subunit genes and the peptide recognition motifs within the host proteins associated with these differential binding specificities. The fimP genes were amplified by PCR from Actinomyces viscosus ATCC 19246, with preferential binding to statherin, and from Actinomyces naeslundii LY7, P-1-K, and B-1-K, with preferential binding to APRPs. The fimP gene from the statherin-binding strain 19246 is novel and has about 80% nucleotide and amino acid sequence identity to the highly conserved fimP genes of the APRP-binding strains (about 98 to 99% sequence identity). The novel FimP protein contains an amino-terminal signal peptide, randomly distributed single-amino-acid substitutions, and structurally different segments and ends with a cell wall-anchoring and a membrane-spanning region. When agarose beads with CNBr-linked host determinant-specific decapeptides were used, A. viscosus 19246 bound to the Thr42Phe43 terminus of statherin and A. naeslundii LY7 bound to the Pro149Gln150 termini of APRPs. Furthermore, while the APRP-binding A. naeslundii strains originate from the human mouth, A. viscosus strains isolated from the oral cavity of rat and hamster hosts showed preferential binding to statherin and contained the novel fimP gene. Thus, A. viscosus and A. naeslundii display structurally variant fimP genes whose protein products are likely to interact with different peptide motifs and to determine animal host tropism.

  • 45. Li, T
    et al.
    Khah, MK
    Slavnic, S
    Johansson, Ingegerd
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Strömberg, Nicklas
    Umeå universitet, Medicinsk fakultet, Odontologi, Kariologi.
    Different type 1 fimbrial genes and tropisms of commensal and potentially pathogenic Actinomyces spp. with different salivary acidic proline-rich protein and statherin ligand specificities.2001Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 69, nr 12, s. 7224-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Actinomyces spp. exhibit type 1 fimbria-mediated adhesion to salivary acidic proline-rich proteins (PRPs) and statherin ligands. Actinomyces spp. with different animal and tissue origins belong to three major adhesion types as relates to ligand specificity and type 1 fimbria genes. (i) In preferential acidic-PRP binding, strains of Actinomyces naeslundii genospecies 1 and 2 from human and monkey mouths displayed at least three ligand specificities characterized by preferential acidic-PRP binding. Slot blot DNA hybridization showed seven highly conserved type 1 fimbria genes (orf1- to -6 and fimP) in genospecies 1 and 2 strains, except that orf5 and orf3 were divergent in genospecies 1. (ii) In preferential statherin binding, oral Actinomyces viscosus strains of rat and hamster origin (and strain 19246 from a human case of actinomycosis) bound statherin preferentially. DNA hybridization and characterization of the type 1 fimbria genes from strain 19246 revealed a homologous gene cluster of four open reading frames (orfA to -C and fimP). Bioinformatics suggested sortase (orfB, orf4, and part of orf5), prepilin peptidase (orfC and orf6), fimbria subunit (fimP), and usher- and autotransporter-like (orfA and orf1 to -3) functions. Those gene regions corresponding to orf3 and orf5 were divergent, those corresponding to orf2, orf1, and fimP were moderately conserved, and those corresponding to orf4 and orf6 were highly conserved. Restriction fragment length polymorphism analyses using a fimP probe separated human and monkey and rat and hamster strains into phylogenetically different groups. (iii) In statherin-specific binding, strains of A. naeslundii genospecies 1 from septic and other human infections displayed a low-avidity binding to statherin. Only the orf4 and orf6 gene regions were highly conserved. Finally, rat saliva devoid of statherin bound bacterial strains avidly irrespective of ligand specificity, and specific antisera detected either type 1, type 2, or both types of fimbria on the investigated Actinomyces strains.

  • 46.
    Lindberg, Stina
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Xia, Yan
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Sondén, Berit
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Göransson, Mikael
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Hacker, Jörg
    Institut für Moleculare Infektionsbiologie, Würzburg, Germany.
    Uhlin, Bernt Eric
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Regulatory Interactions among adhesin gene systems of uropathogenic Escherichia coli2008Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 76, nr 2, s. 771-780Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Uropathogenic Escherichia coli strain J96 carries multiple determinants for fimbrial adhesins. The regulatory protein PapB of P fimbriae has previously been implicated in potential coregulatory events. The focB gene of the F1C fimbria determinant is highly homologous to papB; the translated sequences share 81% identity. In this study we investigated the role of PapB and FocB in regulation of the F1C fimbriae. By using gel mobility shift assays, we showed that FocB binds to sequences in both the pap and foc operons in a somewhat different manner than PapB. The results of both in vitro cross-linking and in vivo oligomerization tests indicated that FocB could function in an oligomeric fashion. Furthermore, our results suggest that PapB and FocB can form heterodimers and that these complexes can repress expression of the foc operon. The effect of FocB on expression of type 1 fimbriae was also tested. Taken together, the results that we present expand our knowledge about a regulatory network for different adhesin gene systems in uropathogenic E. coli and suggest a hierarchy for expression of the fimbrial adhesins.

  • 47.
    Lindgren, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Honn, Marie
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Golovlev, Igor
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Kadzhaev, Konstantin
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Conlan, Wayne
    NRC Canada.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    The 58-kilodalton major virulence factor of Francisella tularensis is required for efficient utilization of iron2009Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 77, nr 10, s. 4429-4436Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigated the role of the 58-kDa FTT0918 protein in the iron metabolism of Francisella tularensis. The phenotypes of SCHU S4, a prototypic strain of F. tularensis subsp. tularensis, and the Delta FTT0918 and Delta fslA isogenic mutants were analyzed. The gene product missing in the Delta fslA mutant is responsible for synthesis of a siderophore. When grown in broth with various iron concentrations, the two deletion mutants generally reached lower maximal densities than SCHU S4. The Delta FTT0918 mutant, but not the Delta fslA mutant, upregulated the genes of the F. tularensis siderophore locus (fsl) operon even at high iron concentrations. A chrome azurol sulfonate plate assay confirmed siderophore production by all strains except the Delta fslA strain. In a cross-feeding experiment using medium devoid of free iron, SCHU S4 promoted growth of the Delta fslA strain but not of the Delta FTT0918 strain. The sensitivity of SCHU S4 and the Delta FTT0918 and Delta fslA strains to streptonigrin demonstrated that the Delta FTT0918 strain contained a smaller free intracellular iron pool and that the Delta fslA strain contained a larger one than SCHU S4. In contrast to the marked attenuation of the Delta FTT0918 strain, the Delta fslA strain was as virulent as SCHU S4 in a mouse model. Altogether, the data demonstrate that the FTT0918 protein is required for F. tularensis to utilize iron bound to siderophores and that it likely has a role also in siderophore-independent iron acquisition. We suggest that the FTT0918 protein be designated Fe utilization protein A, FupA.

  • 48.
    Lindgren, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Honn, Marie
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Salomonsson, Emelie
    Kuoppa, Kerstin
    Forsberg, Åke
    Swedish Def Res Agcy, Div CBRN Def & Secur, SE-90182 Umea, Sweden .
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi. Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR).
    Iron content differs between Francisella tularensis subspecies tularensis and subspecies holarctica strains and correlates to their susceptibility to H(2)O(2)-induced killing2011Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 79, nr 3, s. 1218-1224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis, the causative agent of tularemia, is one of the most infectious bacterial pathogens known and is classified as a category A select agent and a facultative intracellular bacterium. Why F. tularensis subsp. tularensis causes a more severe form of tularemia than F. tularensis subsp. holarctica does is not known. In this study, we have identified prominent phenotypic differences between the subspecies, since we found that F. tularensis subsp. tularensis strains contained less iron than F. tularensis subsp. holarctica strains. Moreover, strain SCHU S4 of F. tularensis subsp. tularensis was less susceptible than FSC200 and the live vaccine strain (LVS) of F. tularensis subsp. holarctica to H(2)O(2)-induced killing. The activity of the H(2)O(2)-degrading enzyme catalase was similar between the strains, whereas the iron content affected their susceptibility to H(2)O(2), since iron starvation rendered F. tularensis subsp. holarctica strains more resistant to H(2)O(2). Complementing LVS with fupA, which encodes an important virulence factor that regulates iron uptake, reduced its iron content and increased the resistance to H(2)O(2)-mediated killing. By real-time PCR, it was demonstrated that FSC200 and LVS expressed higher levels of gene transcripts related to iron uptake and storage than SCHU S4 did, and this likely explained their high iron content. Together, the results suggest that F. tularensis subsp. tularensis strains have restricted iron uptake and storage, which is beneficial for their resistance to H(2)O(2)-induced killing. This may be an important factor for the higher virulence of this subspecies of F. tularensis, as reactive oxygen species, such as H(2)O(2), are important bactericidal components during tularemia.

  • 49.
    Lindgren, Helena
    et al.
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Shen, Hua
    Zingmark, Carl
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Golovliov, Igor
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Conlan, Wayne
    NRC, Kanada.
    Sjöstedt, Anders
    Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi. Umeå universitet, Medicinsk fakultet, Klinisk mikrobiologi, Klinisk bakteriologi.
    Resistance of Francisella tularensis strains against reactive nitrogen and oxygen species with special reference to the role of KatG.2007Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 75, nr 3, s. 1303-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis is a facultative intracellular bacterial pathogen capable of proliferating within host macrophages. The mechanisms that explain the differences in virulence between various strains of the species are not well characterized. In the present study, we show that both attenuated (strain LVS) and virulent (strains FSC200 and SCHU S4) strains of the pathogen replicate at similar rates in resting murine peritoneal exudate cells (PEC). However, when PEC were activated by exposure to gamma interferon (IFN-gamma), they killed LVS more rapidly than virulent strains of the pathogen. Addition of N(G)-monomethyl-l-arginine, an inhibitor of inducible nitric oxide synthase, to IFN-gamma-treated PEC, completely inhibited killing of the virulent strains, whereas it only partially blocked the killing of LVS. Similarly, in a cell-free system, SCHU S4 and FSC200 were more resistant to killing by H(2)O(2) and ONOO(-) than F. tularensis LVS. Catalase encoded by katG is a bacterial factor that can detoxify bactericidal compounds such as H(2)O(2) and ONOO(-). To investigate its contribution to the virulence of F. tularensis, katG deletion-containing mutants of SCHU S4 and LVS were generated. Both mutants demonstrated enhanced susceptibility to H(2)O(2) in vitro but replicated as effectively as the parental strains in unstimulated PEC. In mice, LVS-DeltakatG was significantly attenuated compared to LVS whereas SCHU S4-DeltakatG, despite slower replication, killed mice as quickly as SCHU S4. This implies that clinical strains of the pathogen have katG-independent mechanisms to combat the antimicrobial effects exerted by H(2)O(2) and ONOO(-), the loss of which could have contributed to the attenuation of LVS.

  • 50.
    Lindgren, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi. Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Stenmark, Stephan
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Chen, Wangxue
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi.
    Tärnvik, Arne
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Infektionssjukdomar.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Distinct roles of reactive nitrogen and oxygen species to control infection with the facultative intracellular bacterium Francisella tularensis.2004Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 72, nr 12, s. 7172-7182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reactive nitrogen species (RNS) and reactive oxygen species (ROS) are important mediators of the bactericidal host response. We investigated the contribution of these two mediators to the control of infection with the facultative intracellular bacterium Francisella tularensis. When intradermally infected with the live vaccine strain F. tularensis LVS, mice deficient in production of RNS (iNOS(-/-) mice) or in production of ROS by the phagocyte oxidase (p47(phox-/-) mice) showed compromised resistance to infection. The 50% lethal dose (LD(50)) for iNOS(-/-) mice was <20 CFU, and the LD(50) for p47(phox-/-) mice was 4,400 CFU, compared to an LD(50) of >500,000 CFU for wild-type mice. The iNOS(-/-) mice survived for 26.4 +/- 1.8 days, and the p47(phox-/-) mice survived for 10.1 +/- 1.3 days. During the course of infection, the serum levels of gamma interferon (IFN-gamma) and interleukin-6 were higher in iNOS(-/-) and p47(phox-/-) mice than in wild-type mice. Histological examination of livers of iNOS(-/-) mice revealed severe liver pathology. Splenocytes obtained 5 weeks after primary infection from antibiotic-treated iNOS(-/-) mice showed an in vitro recall response that was similar in magnitude and greater secretion of IFN-gamma compared to cells obtained from wild-type mice. In summary, mice lacking expression of RNS or ROS showed extreme susceptibility to infection with F. tularensis LVS. The roles of RNS and ROS seemed to be distinct since mice deficient in production of ROS showed dissemination of infection and died during the early phase of infection, whereas RNS deficiency led to severe liver pathology and a contracted course of infection.

12 1 - 50 av 82
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf