Molecular Characterization of host-specific and –unspecific properties of IdeC, the IgG-specific protease of Streptococcus canis
Veterinary Medical Science
Final Report Abstract
Streptococcus canis is an opportunistic Lancefield group-G pathogen that colonises the mucosal surfaces and skin of the host, affecting predominantly cats and dogs. S. canis is also a zoonotic pathogen causing a broad variety of local and systemic human infections after transmission from companion animals. Different virulence factors of streptocooci mediate colonisation, survival and replication during pathogenesis. This project is focused on the functional characterisation of the Streptococcal cysteine protease IdeC, which specifically cleaves Immunglobulin G (IgG). Cleavage of IgG is supposed to confer an important bacterial strategy to evade the host´s humoral immune defense mechanism during infection. Previous work has demonstrated that IdeC cleaves IgG belonging to cats, dogs and humans but not of other animals, such as cattle. The first aim of this project was to characterize to detail the cause of the documented species specificity by biochemically analysing the interactions between IdeC and feline, canine, and human IgG. Our results of cleavage efficiency assessment demonstrated that efficiency of IdeC cleavage differs between species, with the most efficient cleavage occurring in feline IgG, followed by human IgG, and finally canine IgG is cleaved with the least efficiency. To explore possible reasons for the monitored differences in IgG cleavage efficiency, we have quantified cleavage of different subtypes of IgG. Moreover, we have investigated the impact of post-translational modifications, and of N-glycosylations of IgG molecules on cleavage efficiency. Analysis of the IdeC amino acid sequence revealed presence of an RGD motive, representing the amino acids arginine, glycin and aspartate, which are known to mediate interaction with eukaryotic cell surface receptors named integrins. Since integrin binding is known as an important bacterial virulence mechanism promoting attachment and internalization to host cells, a further aim was to analyse the function of IdeC as integrin-binding protein of S. canis. Our data demonstrate that the surface-displayed protein IdeC binds to endothelial and epithelial cells, and electron microscopy confirmed that this IdeC-binding mediates bacterial uptake into host cells. We further identified αVβ3-integrins present on eukaryotic cells as specific IdeC receptor mediating interaction via an RGD-amino acid motif, thereby inducing bacterial uptake. In sum, these results identified the cysteine protease IdeC as a pivotal virulence factor of S. canis promoting humoral immune-evasion by cleavage of IgG and additionally facilitating bacterial uptake into host cells by mediating attachment of S. canis to eukaryotic integrin receptors. Therefore, data obtained in this project significantly contribute to understanding of major pathogenic mechanism of Streptococcus canis.
Publications
-
Limiting Factors in Treatment Success of Biofilm-Forming Streptococci in the Case of Canine Infective Endocarditis Caused by Streptococcus canis. Veterinary Sciences, 10(5), 314.
Katsburg, Miriam; Weingart, Christiane; Aubry, Etienne; Kershaw, Olivia; Kikhney, Judith; Kursawe, Laura; Lübke-Becker, Antina; Moter, Annette; Skrodzki, Marianne; Kohn, Barbara & Fulde, Marcus
-
New variant strain of Streptococcus canis with Lancefield group C isolated from canine otitis externa. Veterinary Microbiology, 285, 109869.
Katsburg, Miriam and Brombach, Julian and Hanke, Dennis, Aubry, Etienne, Lübke-Becker, Antina & Fulde, Marcus
-
The type-2 Streptococcus canis M protein SCM-2 binds fibrinogen and facilitates antiphagocytic properties. Frontiers in Microbiology, 14.
Lapschies, Antje-Maria; Aubry, Etienne; Kohler, Thomas P.; Goldmann, Oliver; Hammerschmidt, Sven; Nerlich, Andreas; Eichhorn, Inga; van Vorst, Kira & Fulde, Marcus
