Study of the IgG endoglycosidase EndoS in group A streptococcal phagocyte resistance and virulence

Jonathan Sjögren,Cheryl Ym Okumura,Mattias Collin,Victor Nizet,Andrew Hollands

doi:10.1186/1471-2180-11-120

Jonathan Sjögren, Cheryl Ym Okumura + Show 3 more

Open Access

https://doi.org/10.1186/1471-2180-11-120

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Abstract

BackgroundThe secreted enzyme EndoS, an endoglycosidase from Streptococcus pyogenes, hydrolyzes the N-linked glycan of the constant region of immunoglobulin G (IgG) heavy chain and renders the antibody unable to interact with Fc receptors and elicit effector functions. In this study we couple targeted allelic replacement mutagenesis and heterologous expression to elucidate the contribution of EndoS to group A Streptococcus (GAS) phagocyte resistance and pathogenicity in vitro and in vivo.ResultsKnocking out the EndoS gene in GAS M1T1 background revealed no significant differences in bacterial survival in immune cell killing assays or in a systemic mouse model of infection. However, exogenous addition and heterologous expression of EndoS was found to increase GAS resistance to killing by neutrophils and monocytes in vitro. Additionally, heterologous expression of EndoS in M49 GAS increased mouse virulence in vivo.ConclusionsWe conclude that in a highly virulent M1T1 background, EndoS has no significant impact on GAS phagocyte resistance and pathogenicity. However, local accumulation or high levels of expression of EndoS in certain GAS strains may contribute to virulence.

Highlights

The secreted enzyme EndoS, an endoglycosidase from Streptococcus pyogenes, hydrolyzes the Nlinked glycan of the constant region of immunoglobulin G (IgG) heavy chain and renders the antibody unable to interact with Fc receptors and elicit effector functions
Generation of EndoS mutants and heterologous expression To investigate the contribution of EndoS to group A Streptococcus (GAS) and host-cell interactions an allelic replacement knockout in the M1T1 background was constructed and denoted 5448 ΔndoS
The results reveal that heterologous overexpression of EndoS in M49, NZ131[pNdoS] increased GAS resistance to killing by human neutrophils (Figure 1E)

Summary

Introduction

The secreted enzyme EndoS, an endoglycosidase from Streptococcus pyogenes, hydrolyzes the Nlinked glycan of the constant region of immunoglobulin G (IgG) heavy chain and renders the antibody unable to interact with Fc receptors and elicit effector functions. In this study we couple targeted allelic replacement mutagenesis and heterologous expression to elucidate the contribution of EndoS to group A Streptococcus (GAS) phagocyte resistance and pathogenicity in vitro and in vivo. A hypothesized GAS immune evasion factor is the secreted enzyme EndoS, an endoglycosidase possessing a highly specific hydrolyzing activity toward the Nlinked glycan of immunoglobulin G (IgG) [4]. We hypothesize that EndoS contributes to GAS virulence by hydrolyzing the Nlinked glycan on IgG and thereby impairing antibody mediated functions in the immune system. We couple targeted allelic replacement mutagenesis and heterologous gene expression to study EndoS activity during bacterial-host cell interaction in vitro and in vivo

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Discussion

Conclusion