Background
Streptococcus pyogenes (S. pyogenes) is a human specific gram-positive bacterium associated with considerable morbidity and mortality. Immunity to streptococcal infections involves generation of antibodies facilitating bacterial clearance. Currently however, the basis for population immunity against S. pyogenes remains unclear. Here, we aimed to develop an unbiased and quantitative mass spectrometry-based method to determine the antibody dependent “antigen-ome” of S. pyogenes and identify the sub-proteome capable of eliciting a strong protective immune response.
Methods
To identify and quantitate immuno-dominant streptococcal antigens we perform in-depth bacterial fractionation on an invasive streptococcal M1 serotype to separate the secreted, cell wall and the membrane proteins followed by detailed proteomics analysis. IgG’s were isolated from acute and convalescent plasma of a septic patient cohort infected with different S. pyogenes strains and the bacterial fractions were passed over the purified IgG’s to capture specific antigens
Results
Mass spectrometry analysis of these anti-streptococcal antibody complex identified 40 streptococcal antigens. The strategy helped us rank these antigens based on their immunodominancy and understand their distribution pattern in different conditions. Patients seemed to have highly dynamic response towards these immuno-dominant antigens in the acute and convalescence phase. Further bioinformatics analysis of these proteins reveals some of them to be highly conserved, suggesting a basal level of circulating adaptive immune response against these antigens.
Conclusion
We report an automated proteomic approach showcasing the S. pyogenes antigen-ome profiling thereby providing novel insights on streptococcal antigens. Such a strategy could be applied across different pathogens to carefully discern the predominant antigens.