Development and effect evaluation of Streptococcus suis type 2 vaccine medium with high antigenic activity based on response surface analysis.

The study aimed to develop a Streptococcus suis type 2 (SS2) vaccine medium with a high antigenic activity. SS2 CVCC60615 strain was used as the experimental object. The SS2 vaccine medium was developed by a single factor test, Plackett-Burman test, steepest ascent test and response surface analysis. The culture medium fermentation verification results showed that the maximum viable count in the culture medium of SS2 vaccine was 1.09 x 109 CFU/mL, which was 2.41 times higher than that obtained by using TSB medium. Through the determination of SS2 antigenic activity at different time points, it was found that the antigenic activity of bacteria was the highest within 1~3 h after the count of viable bacteria reached the maximum in the fermentation culture process of SS2. The mice infection test showed that the inactivated vaccine prepared when the SS2 antigen activity was the highest had a higher IgG antibody titer and a vaccine protection rate than the commercial inactivated vaccine. The study indicates that the inactivated vaccine prepared using the developed high antigen activity SS2 vaccine culture medium has the advantages of high IgG antibody titer and strong immune protection force. [ABSTRACT FROM AUTHOR]