| 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. |
