Background. Streptococcus suis is a commensal of pigs, but can also cause invasive infections. It is responsible for high economic losses in swine farming worldwide. As an emerging zoonotic agent S. suis is able to induce meningitis, arthritis and septicemia. The species comprises 35 serotypes of which serotype 2 is the most prevalent serotype , followed by serotypes 9, 7 and 3 in Europe . The mechanisms enabling the switch from commensal to an invasive pathogen are only partially resolved. We performed comparative profiling of S. suis proteome patterns and immunoproteome screening of S. suis antigens to explore adaptation to host niches and to identify new potential virulence/fitness factors and vaccine candidates.
Methods. S. suis proteomes were analyzed for serotypes 2, 9 and 7 from different growth phases using a data-independent acquisition (DIA) mass spectrometry workflow . In addition, S. suis specific antibody profiles were recorded using recombinantly expressed proteins in a multiplexed suspension bead array.
Results. Initially an in-house spectral library was generated using strain specific genome sequences and S. suis protein extracts from samples grown in different media, at different temperatures and after nutrient or iron limitation. Using a DIA-workflow and an optimized peptide preparation routinely around 1100 proteins were quantitatively profiled from low bacteria numbers (106 – 107) from rich medium, ex vivo samples (pig CSF and plasma) or after recovery from infection by cell sorting. Complementing this proteomics profiling the antibody response of infected pigs against a diverse range of S. suis antigens was recorded by bead-based immunoproteomics. This revealed differentially abundant proteins between these conditions and immunogenic proteins, which might be involved in adaptation to the different specific host niches and constitute potential new virulence factors and vaccine candidates.
Conclusion. The identified proteins provide a promising basis to evaluate conserved immunogenic antigens for multicomponent vaccines.