An oral multivalent fusion vaccine based on antigenic fragment VP56(310-500) and FlaC adjuvant confers effective protection against grass carp reovirus.
An oral multivalent fusion vaccine based on antigenic fragment VP56(310-500) and FlaC adjuvant confers effective protection against grass carp reovirus.
21 Jan 2026
Grass carp reovirus (GCRV) poses a serious economic threat to grass carp aquaculture and oral vaccination has become the strategy of choice for its control. In this study, multiple sequence alignment was conducted on the sequences of the VP56 of seven GCRV-II strains. The most frequent amino acid at each site was assigned to the fusion sequence to obtain the sequences of GCRV-FUSION (VP561-512). Through antigenic index analysis, the full-length sequence (VP561-512) was truncated, thereby obtaining five truncated antigen fragments: VP561-210, VP56100-209, VP56210-310, VP56310-500, and VP56410-500. Then, using flagellin C (FlaC) from Aeromonas hydrophila as an adjuvant, recombinant Pichia pastoris expressing VP561-512-FlaC, VP561-210-FlaC, VP56100-209-FlaC, VP56210-310-FlaC, VP56310-500-FlaC and VP56410-500-FlaC were constructed, and recombinant proteins were examined by SDS-PAGE and WB assays. The experimental fish was divided into 8 groups (blank control, P-pPIC3.5K, P-VP561-512-FlaC, P-VP561-210-FlaC, P-VP56100-209-FlaC, P-VP56210-310-FlaC, P-VP56310-500-FlaC, P-VP56410-500-FlaC) to evaluate the protective effect. The survival rate of the P-VP56310-500-FlaC group (54 %) was significantly higher than that of the blank control group (18 %). Oral P-VP56310-500-FlaC vaccine can effectively increase serum enzyme activities (lysozyme, total antioxidant capacity and complement component 3). The mRNA expressions of immune genes (TLR5a, IL-6, IFN1, Mx2, IL-1β, MHCII, IgM, IgT) in the P-VP56310-500-FlaC group were significantly increased. The vaccine P-VP56310-500-FlaC significantly inhibited the replication of GCRV in the spleen, head kidney and midgut, and reduced the degree of damage to the spleen. The above results indicate that oral P-VP56310-500-FlaC vaccine can effectively control GCRV infection, providing an effective strategy for the prevention of viral diseases in aquaculture.