A bivalent oral vaccine against Micropterus salmoides rhabdovirus and largemouth bass ranavirus based on yeast surface display technology

Micropterus salmoides rhabdovirus (MSRV) and largemouth bass ranavirus (LMBV) are two major pathogens of Micropterus salmoides , for which no specific drugs or commercial vaccines are currently available. In this study, the G protein of MSRV and the MCP protein of LMBV were used as immunogens. Recombinant Saccharomyces cerevisiae strains displaying these proteins were constructed using yeast surface display technology, and the two recombinant yeasts were mixed at a 1:1 ratio to prepare a bivalent oral vaccine. Results showed that the bivalent vaccine induced G- and MCP-specific antibodies, upregulated the expression of specific immune-related genes such as IgM , IgT , and MHC II , and activated non-specific immune factors including TNFα , IL-1β , IFN1 , and Mx2 in the hindgut, liver, and spleen. Challenge experiments showed that the bivalent vaccine provided a relative percent survival (RPS) of 56.7% against LMBV challenge and 80% against MSRV challenge, while also reducing tissue viral loads and alleviating the histopathological damage induced by the virus. In conclusion, this study successfully developed a safe, low-cost bivalent oral vaccine that confers immune protection against both MSRV and LMBV, showing promising application prospects.