Study on immunogenicity of Lrp subunit vaccine against Vibrio alginolyticus in pearl gentian grouper(Epinephelus fuscoguttatus xEpinephelus lanceolatus)

Vibrio alginolyticus is the main pathogen causing vibriosis in pearl gentian grouper, which has caused significant financial losses to farmers. To develop a sustainable and effective subunit vaccine for the prevention and control of vibriosis, Lrp recombinant protein from V. alginolyticus was expressed and purified in this study. Western Blotting and ELISA demonstrated that Lrp recombinant protein with relatively higher antigenicity in V. alginolyticus can be used as an antigen for the subunit vaccine. Chitosan oligosaccharide (COS) is a very potential aquatic vaccine adjuvant to boost the immunological protection of the vaccine. Therefore, to evaluate the immune response and protection of the subunit vaccine against V. alginolyticus in pearl gentian grouper, we designed the Lrp group and Lrp+COS group as experimental groups with PBS as the control group. Immunological testing revealed that grouper serum from the experimental group had significantly higher levels of the particular antibody IgM, lysozyme (LZM), catalase (CAT), and superoxide dismutase (SOD) than serum from the control group. Additionally, groupers from the experimental group showed higher immune gene expression levels, namely IgM, CD8 alpha, MHC-I alpha, IL-1 beta, IL-16, and TNF-alpha. After the challenge experiment, the immune protection rates of the Lrp group and Lrp+COS group were respectively enhanced to 60% and 72%. The aforementioned findings demonstrated that the Lrp+COS group's immunological impact was superior to that of the Lrp group. Therefore, the Lrp+COS subunit vaccine is a promising candidate for the prevention and management of vibrio infection in pearl grouper.