No abstract

A bstractAeromonas hydrophila is a Gram-negative pathogen that can infect various fi sh, including largemouth bass ( Micropterus salmoides ), which have caused huge economic losses. In present study, largemouth bass anti-A . hydrophila antibodies were produced, then a highly immunogenic outer membrane proteins, AHA_3793, was identifi ed by combined western blotting and mass spectrometry analysis. Moreover, AHA_3793 was expressed, and its immunogenicity was further verifi ed by western blotting. Subsequently, the protective effi cacy of AHA_3793 were evaluated in largemouth bass. The results showed that rAHA_3793 could produce a relative percentage survival (RPS) of 61.76% for largemouth bass against A . hydrophila challenge. ELISA analysis showed the specifi c serum antibodies of largemouth bass against rAHA_3793 and A . hydrophila in vaccinated group in weeks 4 and 5 after immunization were signifi cantly higher than those in control group, which suggested that rAHA_3793 induced production of specifi c serum antibodies against rAHA_3793 and A . hydrophila . The qRT-PCR analysis showed that expressions of CD4-2 and MHC IIα were also signifi cantly up-regulated after immunization. These results collectively demonstrated that rAHA_3793 could induce a strong humoral immune response of largemouth bass, and then produce high immune protection eff ects against A . hydrophila infection.