Development and evaluation of recombinant multi-epitopes vaccine against nervous necrosis virus.

Capsid protein (CP) is the antigen of nervous necrosis virus (NNV), a fatal microorganism for almost marine fishes. Antigen epitope is a special chemical group in an antigen molecule that determines the specificity of the antigen, usually consisting of 5-15 amino acid residues. However, the antigen epitope of NNV antigen remains unclear. In this study, using immunoinformatic method, we analyzed the antigen epitope of CP and designed a multi-epitopes vaccine of NNV (PA). Furthermore, we evaluated the immune responses induced by PA vaccine. The results showed that three cytotoxic T lymphocyte epitopes and six B-cell lymphocyte epitopes were predicted, with high antigenicity, non-allergen, and non-toxin. Based on these epitopes, a multi-epitopes vaccine of NNV (PA) was designed and prepared. After immunization, the mRNA expression levels of IL-1β, TNF-α, CD4, CD8, MHC-Ⅰ, and MHC-Ⅱ in PA group were significantly up-regulated. Moreover, it has been proven that PA could significantly activate antigen presenting cells. Importantly, PA could induce similar levels of antibodies secretion and immune protection, compared to CP group. The survival rate reached 77.22 % in PA group. This study provides a cheap and effective strategy for aquatic vaccine design, which will be beneficial in application to development of vaccine in aquaculture industry.