Evaluation on aStreptococcus suisVaccine Using Recombinant Sao-L Protein Manufactured by Bioreactors as the Antigen in Pigs

Abstract

Streptococcus suis (S.suis) can be classified into 33 serotypes based on the structure of capsular polysaccharides. Recent research indicated that a new surface protein designated as Sao (surface antigen one) reacts with 30 serotypes of convalescent-phase sera during S.suis infections, which makes Sao a good potential antigen for developing S.suis vaccines. The objectives of this study were to produce recombinant Sao-L protein (rSao-L) from a strain of S.suis serotype 2 by a prokaryotic expression system in bioreactors and to use rSao-L as the antigen for a S.suis vaccine in mouse and swine models. The antibody titres in mice and pigs immunized with rSao-L were significantly (P<0.05) increased. After challenge with live S.suis serotype 1 bacteria, the anatomical lesions in pigs immunized with rSao-L were reduced by 60%. These data indicated that immunization with rSao-L can confer cross-serotype protection against S.suis. Moreover, percentages of CD8(+) and CD4(+) /CD8(+) double-positive T cells in immunized pigs were significantly higher than those of the control group (P<0.01). Using bioreactors to produce rSao-L as the antigen for S.suis vaccines may broaden protective efficacy and reduce production costs.