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Identification of a Novel Host-Specific IgM Protease in Streptococcus suis
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
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2013 (English)In: Journal of Bacteriology, ISSN 0021-9193, E-ISSN 1098-5530, Vol. 195, no 5, 930-940 p.Article in journal (Refereed) Published
Abstract [en]

Streptococcus suis serotype 2 is a highly invasive, extracellular pathogen in pigs with the capacity to cause severe infections in humans. This study was initiated by the finding that IgM degradation products are released after opsonization of S. suis. The objective of this work was to identify the bacterial factor responsible for IgM degradation. The results of this study showed that a member of the IdeS family, designated Ide(Ssuis) (Immunoglobulin M-degrading enzyme of S. suis), is responsible and sufficient for IgM cleavage. Recombinant Ide(Ssuis) was found to degrade only IgM but neither IgG nor IgA. Interestingly, Western blot analysis revealed that Ide(Ssuis) is host specific, as it exclusively cleaves porcine IgM but not IgM from six other species, including a closely related member of the Suidae family. As demonstrated by flow cytometry and immunofluorescence microscopy, Ide(Ssuis) modulates binding of IgM to the bacterial surface. Ide(Ssuis) is the first prokaryotic IgM-specific protease described, indicating that this enzyme is involved in a so-far-unknown mechanism of host-pathogen interaction at an early stage of the host immune response. Furthermore, cleavage of porcine IgM by Ide(Ssuis) is the first identified phenotype reflecting functional adaptation of S. suis to pigs as the main host.

Place, publisher, year, edition, pages
Washington: American society of microbiology , 2013. Vol. 195, no 5, 930-940 p.
National Category
Microbiology in the medical area
Identifiers
URN: urn:nbn:se:umu:diva-70155DOI: 10.1128/JB.01875-12ISI: 000316961400003OAI: oai:DiVA.org:umu-70155DiVA: diva2:619733
Available from: 2013-05-06 Created: 2013-05-06 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Streptococcal immunoglobulin degrading enzymes of the IdeS and IgdE family
Open this publication in new window or tab >>Streptococcal immunoglobulin degrading enzymes of the IdeS and IgdE family
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Bacteria of the genus Streptococcus are common asymptomatic colonisers of humans and animals. As opportunistic pathogens they can however, depending on their host’s immune status and other circumstances, cause mild to very severe infections. Streptococci are highly intertwined with specific host species, but can also cause zoonosis or anthroponosis in more uncommon hosts. Prolonged and reoccurring infections require immune evasion strategies to circumvent detection and eradication by the host’s immune defence. A substantial part of the immune defence against bacterial pathogens is mediated by immunoglobulins. This thesis is based on work to identify and characterise immunoglobulin degrading enzymes secreted by different Streptococcus species as a means to sabotage and evade antibody-mediated immune responses.

Stoichiometric and kinetic analysis of the IgG degrading enzyme IdeS from the important human pathogen S. pyogenes revealed that IdeS cleaves IgG, opposed to previous publications, as a monomer following classical Michaelis-Menten kinetics.

The IdeS homologue of S. suis, IdeSsuis, did however not cleave IgG, but was highly specific fo rporcine IgM. S. suis was found to possess yet another protease, IgdE, capable of cleaving porcine IgG. Both of these proteases were shown to promote increased bacterial survival in porcine blood during certain conditions.

IgdE is the founding member of a novel cysteine protease family (C113). Novel streptococcal members of this protease family were shown to specifically degrade certain IgG subtypes of the respective Streptococcus species’ main host. The observed substrate specificity of IgdE family proteases reflects the host tropism of these Streptococcus species, thereby giving insights into host-pathogen co-evolution.

The abundance of immunoglobulin degrading enzymes among Streptococcus species indicates the importance of evasion from the antibody mediated immune responses for streptococci. These novel identified immunoglobulin degrading enzymes of the IdeS and IgdE protease families are potential valid vaccine targets and could also be of biotechnological use.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2017. 61 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1892
Keyword
Streptococcus, S. pyogenes, S. agalactiae, S. suis, S. porcinus, S. pseudoporcinus, S. equi subsp. zooepidemicus, protease, immunoglobulin, immune evasion, IdeS, IgdE
National Category
Cell and Molecular Biology Biochemistry and Molecular Biology
Research subject
Molecular Biology
Identifiers
urn:nbn:se:umu:diva-134552 (URN)9789176016985 (ISBN)
Public defence
2017-06-01, Major Groove, Byggnad 6L, Norrlands Universitetssjukhus, Umeå, 13:00 (English)
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Available from: 2017-05-11 Created: 2017-05-08 Last updated: 2017-05-15Bibliographically approved

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Spoerry, Christianvon Pawel-Rammingen, Ulrich
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