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  • 51.
    Salomonsson, Emelie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forslund, Anna-Lena
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Kuoppa, Kerstin
    CBRN Defence and Security, FOI Swedish Defence Research Agency, Sweden..
    Michell, Stephen
    School of Biosciences, University of Exeter, Devon, UK.
    Titball, Richard
    School of Biosciences, University of Exeter, Devon, UK.
    Oyston, Petra
    Defence Science and Technology Laboratory, Porton Down, UK..
    Noppa, Laila
    CBRN Defence and Security, FOI Swedish Defence Research Agency, Sweden..
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS). Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Role of type IV pilin encoding genes in virulence of Francisella tularensis subspecies holarcticaManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The number of virulence factors identified in Francisella tularensis, the causative agent of tularemia, is so far relatively few. The F. tularensis genome contains some genes with homology to known virulence factors. One of these is the type IV pili system, which is known to have a key role in virulence of other bacterial species. When we compared different F. tularensis subspecies we could identify distinct differences in Type IV pilin genes between the highly virulent type A strains and the less pathogenic type B strains. In this work we addressed the role in virulence of the different pilin genes in a virulent type B strain. Of all the pilin genes only PilA and the pseudopilins FTT1621-1622 were proven to have a role in virulence. In addition we also verified that the gene encoding the PilT ATPase is non-functional due to a non-sense mutation and we also confirmed that the truncated pilT has no role in mouse virulence. Furthermore we also provide evidence that the F. tularensis pilins are posttranslationally modified presumably by glycosylation by a PilO dependent mechanism.

  • 52.
    Salomonsson, Emelie
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Kuoppa, Kerstin
    FOI, Umeå (Swedish Defence Research Agency).
    Forslund, Anna-Lena
    FOI, Umeå (Swedish Defence Research Agency).
    Golovliov, Igor
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Sjöstedt, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk mikrobiologi, Klinisk bakteriologi.
    Noppa, Laila
    FOI, Umeå (Swedish Defence Research Agency).
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Reintroduction of two deleted virulence loci restores full virulence of the live vaccine strain (LVS) of Francisella tularensisManuskript (Övrig (populärvetenskap, debatt, mm))
  • 53.
    Salomonsson, Emelie
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå Centre for Microbial Research (UCMR). Umeå universitet, Medicinska fakulteten, Molekylär Infektionsmedicin, Sverige (MIMS).
    Kuoppa, Kerstin
    Totalförsvarets forskningsinstitut FOI.
    Forslund, Anna-Lena
    Zingmark, Carl
    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).
    Golovliov, Igor
    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).
    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).
    Noppa, Laila
    Totalförsvarets forskningsinstitut FOI.
    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).
    Reintroduction of two deleted virulence loci restores full virulence to the live vaccine strain of Francisella tularensis2009Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 77, nr 8, s. 3424-3431Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A disadvantage of several old vaccines is that the genetic events resulting in the attenuation are often largely unknown and reversion to virulence cannot be excluded. In the 1950s, a live vaccine strain, LVS, was developed from a type B strain of Francisella tularensis, the causative agent of tularemia. LVS, which is highly attenuated for humans but still virulent for mice by some infection routes, has been extensively studied and found to protect staff from laboratory-acquired tularemia. The efforts to improve biopreparedness have identified a demand for a vaccine against tularemia. Recently the rapid progress in genomics of different Francisella strains has led to identification of several regions of differences (RDs). Two genes carried within RDs, pilA, encoding a putative type IV pilin, and FTT0918, encoding an outer membrane protein, have been linked to virulence. Interestingly, LVS has lost these two genes via direct repeat-mediated deletions. Here we show that reintroduction of the two deleted regions restores virulence of LVS in a mouse infection model to a level indistinguishable from that of virulent type B strains. The identification of the two attenuating deletion events could facilitate the licensing of LVS for use in humans.

  • 54.
    Straskova, Adela
    et al.
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Pavkova, Ivona
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Link, Marek
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Forslund, Anna-Lena
    Swedish Defence Research Agency, Division of NBC-Defence, 901 82 Umea, Sweden.
    Kuoppa, Kerstin
    CBRN Defence and Security, FOI Swedish Defence Research Agency, Sweden.
    Noppa, Laila
    CBRN Defence and Security, FOI Swedish Defence Research Agency, Sweden.
    Kroca, Michal
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Fucikova, Alena
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Klimentova, Jana
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Krocova, Zuzana
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Swedish Defence Research Agency, Division of NBC-Defence, 901 82 Umea, Sweden.
    Stulik, Jiri
    Center of Advanced Studies and Institute of Molecular Pathology, Faculty of Military Health Science UO, Czech Republic.
    Proteome analysis of an attenuated Francisella tularensis dsbA mutant: identification of potential DsbA substrate proteins2009Ingår i: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 8, nr 11, s. 5336-5346Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Francisella tularensis (F. tularensis) is highly infectious for humans via aerosol route and untreated infections with the highly virulent subsp. tularensis can be fatal. Our knowledge regarding key virulence determinants has increased recently but is still somewhat limited. Surface proteins are potential virulence factors and therapeutic targets, and in this study, we decided to target three genes encoding putative membrane lipoproteins in F. tularensis LVS. One of the genes encoded a protein with high homology to the protein family of disulfide oxidoreductases DsbA. The two other genes encoded proteins with homology to the VacJ, a virulence determinant of Shigella flexneri. The gene encoding the DsbA homologue was verified to be required for survival and replication in macrophages and importantly also for in vivo virulence in the mouse infection model for tularemia. Using a combination of classical and shotgun proteome analyses, we were able to identify several proteins that accumulated in fractions enriched for membrane-associated proteins in the dsbA mutant. These proteins are substrate candidates for the DsbA disulfide oxidoreductase as well as being responsible for the virulence attenuation of the dsbA mutant.

  • 55.
    Sundin, Charlotta
    et al.
    Department of Microbiology, FOI NBC-Defence, Umeå.
    Henriksson, Maria L.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Hallberg, Bengt
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Forsberg, Åke
    Department of Microbiology, FOI NBC-Defence, Umeå.
    Frithz-Lindsten, Elisabet
    Department of Microbiology, FOI NBC-Defence, Umeå.
    Exoenzyme T of Pseudomonas aeruginosa elicits cytotoxicity without interfering with Ras signal transduction2001Ingår i: Cellular Microbiology, Vol. 3, nr 4, s. 237-46Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One virulence strategy used by the opportunistic pathogen Pseudomonas aeruginosa is to target toxic proteins into eukaryotic cells by a type III secretion mechanism. Two of these proteins, ExoS and ExoT, show 75% homology on amino acid level. However, compared with ExoS, ExoT exhibits highly reduced ADP-ribosylating activity and the role of ExoT in pathogenesis is poorly understood. To study the biological effect of ExoT, we used a strategy by which ExoT was delivered into host cells by the heterologous type III secretion system ofYersinia pseudotuberculosis. ExoT was found to induce a rounded cell morphology and to mediate disruption of actin microfilaments, similar to that induced by an ADP-ribosylation defective ExoS (E381A) and the related cytotoxin YopE of Y. pseudotuberculosis. In contrast to ExoS, ExoT had no major effect on cell viability and did not modify or inactivate Ras by ADP-ribosylation in vivo. However, similar to ExoS and YopE, ExoT exhibited GAP (GTPase activating protein) activity on RhoA GTPase in vitro. Interestingly, ExoT(R149K), deficient for GAP activity, still caused a morphological change of HeLa cells. Based on our findings, we suggest that the ADP-ribosylating activity of ExoT target another, as yet unidentified, host protein that is distinct from Ras.

  • 56.
    Sundin, Charlotta
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet).
    Thelaus, Johanna
    Bröms, Jeanette E
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten).
    Polarisation of type III translocation by Pseudomonas aeruginosa requires PcrG, PcrV and PopN2004Ingår i: Microbial Pathogenesis, ISSN 0882-4010, E-ISSN 1096-1208, Vol. 37, nr 6, s. 313-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Type III secretion (TTS) mediated translocation of exoenzymes is a key virulence strategy utilised by the opportunistic pathogen Pseudomonas aeruginosa to deliver exoenzyme effectors into the eukaryotic cell. We have previously shown that type III mediated translocation is a contact dependent process, which requires the secreted translocator proteins PerV, PopB and PopD. To further analyse this mechanism, HeLa cells were infected with the wild-type strain PAK as well as isogenic pcrV, popB, popD, pcrG and popN mutants. In the presence of eukaryotic cells, expression of exoenzyme S (ExoS) increased. When cells were infected with the wild-type strain PAK no ExoS was detected in the tissue culture medium. This confirms that ExoS translocation by P. aeruginosa occurs by a polarised mechanism. In contrast, high levels of ExoS were recovered in the tissue Culture medium when cells were infected with pcrG, pcrV and popN mutants. Additionally, ExoS expression levels were higher for these mutants regardless of inducing conditions. This suggests that PcrG, PcrV and PopN are involved in negative regulation of ExoS expression and secretion, and are required to ensure polarised delivery of effectors into target cells.

  • 57.
    Sundin, Charlotta
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för molekylärbiologi (Teknisk-naturvetenskaplig fakultet). Department of Medical Countermeasures, FOI NBC-Defence, S-901 82 Umeå, Sweden.
    Wolfgang, Matthew C.
    Lory, Stephen
    Forsberg, Åke
    Umeå universitet, Medicinska fakulteten, Institutionen för molekylärbiologi (Medicinska fakulteten). Department of Medical Countermeasures, FOI NBC-Defence, S-901 82 Umeå, Sweden.
    Frithz-Lindsten, Elisabet
    Type IV pili are not specifically required for contact dependent translocation of exoenzymes by Pseudomonas aeruginosa2002Ingår i: Microbial Pathogenesis, ISSN 0882-4010, Vol. 33, nr 6, s. 265-277Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The type III secretion system (TTSS) of the opportunistic pathogen Pseudomonas aeruginosa enables the bacterium to deliver exoenzymes directly into the eukaryotic cell. In this study we have investigated the role of key factors involved in this process. We could demonstrate that the translocators PopB, PopD and PcrV are absolutely required for delivery of Exoenzyme S into host cells. By analyzing different Tfp (type IV pili) mutants we could establish a correlation between the frequency of bacteria binding to the host cell and the levels of translocated ExoS, thereby verifying that the process is contact dependent. However, there was no absolute requirement for the Tfp per se, since the pilus could be substituted with a different type of adhesin, the non-fimbrial adhesin pH6 antigen of Yersinia pestis. Taken together, our results demonstrate that binding to establish close contact between the type III secretion organelle and the host cell is essential for translocation, while the additional activities of Tfp are not essential for the delivery of TTSS proteins.

  • 58.
    Tafazoli, Farideh
    et al.
    Division of Medical Microbiology, Department of Health and Environment, Linköping University, Linköping, Sweden.
    Holmström, Anna
    Swedish Defence Research Agency, Division of CBRN Defence and Security, SE-901 82 Umeå, Sweden.
    Forsberg, Åke
    Department of Microbiology, National Defence Research Establishment, Umeå, Sweden.
    Magnusson, Karl-Eric
    Division of Medical Microbiology, Department of Health and Environment, Linköping University, Linköping, Sweden.
    Apically exposed, tight junction-associated beta1-integrins allow binding and YopE-mediated perturbation of epithelial barriers by wild-type Yersinia bacteria2000Ingår i: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 68, nr 9, s. 5335-5343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using polarized epithelial cells, primarily MDCK-1, we assessed the mode of binding and effects on epithelial cell structure and permeability of Yersinia pseudotuberculosis yadA-deficient mutants. Initially, all bacteria except the invasin-deficient (inv) mutant adhered apically to the tight junction areas. These contact points of adjacent cells displayed beta1-integrins together with tight junction-associated ZO-1 and occludin proteins. Indeed, beta1-integrin expression was maximal in the tight junction area and then gradually decreased along the basolateral membranes. Wild-type bacteria also opened gradually the tight junction to paracellular permeation of different-sized markers, viz., 20-, 40-, and 70-kDa dextrans and 45-kDa ovalbumin, as well as to their own translocation between adjacent cells in intimate contact with beta1-integrins. The effects on the epithelial cells and their barrier properties could primarily be attributed to expression of the Yersinia outer membrane protein YopE, as the yopE mutant bound but caused no cytotoxicity. Moreover, the apical structure of filamentous actin (F-actin) was disturbed and tight junction-associated proteins (ZO-1 and occludin) were dispersed along the basolateral membranes. It is concluded that the Yersinia bacteria attach to beta1-integrins at tight junctions. Via this localized injection of YopE, they perturb the F-actin structure and distribution of proteins forming and regulating tight junctions. Thereby they promote paracellular translocation of bacteria and soluble compounds.

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