A universal live vaccine platform against multiple serotypes Streptococcus suis based on polyvalent antigen protein.

Streptococcus suis (S. suis) is a major pathogen that poses a long-term threat to swine populations. Due to its foodborne transmission, this pathogen has recently emerged as a leading cause of meningitis in humans, presenting a significant public health challenge. Currently, no vaccine is available to combat this disease, particularly a universal vaccine capable of addressing multiple subtypes of S. suis. In this study, we developed a universal live vaccine candidate against multiple serotypes S. suis based on the polyvalent antigen protein SE6. A live Salmonella Choleraesuis (S. Choleraesuis) vector was employed for the production and in vivo delivery of the polyvalent antigen. The SE6 protein was efficiently expressed within the S. Choleraesuis vector and delivered to the host's lymphatic system. The antiserum of mice immunized with SE6-delivering S. Choleraesuis vector produced a broader and potent opsonophagocytic response against multiple serotypes of S. suis. Finally, the SE6-delivering S. Choleraesuis vector demonstrated high efficacy in providing protection against S. suis serotypes 2, 7, and 9 in vivo.