Identification of three novel in vivo-induced expressed antigens during infection with Streptococcus suis serotype 2.

Streptococcus suis serotype 2 (SS2) is a porcine and human pathogen with adhesive and invasive properties. The shortage of studies on the pathogenesis mechanisms of SS2 has made it very difficult to control infection with this pathogen. Three novel in vivo-induced antigens were identified using serological proteome analysis of the SS2 cell wall-associated proteins--SecA, autolysin and ZnuA--the upregulation of which in vivo relative to in vitro was shown by real-time PCR analysis. The in vivo-induced expression of znuA was also confirmed by the fact that the purified recombinant ZnuA could be recognized not by hyperimmune sera but by convalescent sera. This is, to the best of the authors' knowledge, the first report using an immunoproteomic method to identify in vivo-induced antigens of SS2.