A vaccine combining ORF132 and ORF25 expressed by Saccharomyces cerevisiae induces protective immunity in Carassius auratus gibelio against CyHV-2

CyHV-2 is the pathogen of herpesvirus hematopoietic necrosis (HVHN), resulting in significant economic losses in crucian carp. Although multiple oral vaccines have been developed to prevent CyHV-2, they have not achieved ideal protective effects. To improve the protective effect of oral vaccine, a combination vaccine was conducted by mixing recombinant Saccharomyces cerevisiae displaying ORF132 or ORF25 on the cell surface in a 1:1 ratio. Oral immunization with this combined vaccine induced specific antibodies against ORF132 and ORF25 in fish serum, as well as increased the transcription levels of IgT, IgM, IL-1β, IFN-1, and TNF-α in the spleen, head-kidney, and hindgut. Importantly, the combined vaccine provided significant protection against CyHV-2 infection in crucian carp, resulting in a relative percent survival of 80.77 %. Additionally, it suppressed viral load and alleviated pathological damage of CyHV-2-infected fish. The results suggest that the combined vaccine exhibits a better protective effect compared to the single-antigen vaccines, indicating it as a promising approach to prevent CyHV-2 outbreaks.