Li Ningqiu

An outer membrane protein, OmpK, is an effective vaccine candidate for Vibrio harveyi in Orange-spotted grouper (Epinephelus coioides).

The outer membrane proteins of the fish pathogen, Vibrio harveyi, have a role in interaction between bacterium and host and are potential candidates for vaccine development. In this study, the gene encoding an outer membrane protein, OmpK, which serves as the receptor for broad-host-range vibriophage KVP40 in V. harveyi, was isolated and characterized. Then the OmpK gene coding for mature peptide was subcloned into prokaryotic expression vector pBV220 and transformed into Escherichia coli DH5 alpha strain. After temperature induction, a recombinant protein was detected about 28 kDa in molecular weight and accounted for 24.8% of total proteins of whole cell as estimated by SDS-PAGE and scanning analysis of gel image. Polyclonal antibodies were raised in rabbits against the purified protein and the reaction of the antibody was confirmed by western blotting using the purified protein and crude extract of V. harveyi. Orange-spotted groupers (Epinephelus coioides) vaccinated with recombinant OmpK produced specific antibodies, and were highly resistant to infection by virulent V. harveyi. These results indicate that the OmpK is an effective vaccine candidate against V. harveyi in Orange-spotted groupers.

An avirulent Micropterus salmoides rhabdovirus vaccine candidate protects Chinese perch against rhabdovirus infection

ABSTRACT In order to develop live vaccine against Siniperca chuatsi rhabdovirus (SCRV) disease, an avirulent virus strain, designed as Micropterus salmoides rhabdovirus Sanshui (MSRV‐SS), was selected from six fish rhabdovirus isolates (SCRV‐QYSymbol SCRV‐SSSymbol SCRV‐GMSymbol CMRV‐FSSymbol OMBRV‐JMSymbol MSRV‐SS) by fish challenge assay. When Chinese perch (Siniperca chuatsi) were intraperitoneally injected live virus strain MSRV‐SS, they were completely protected from virulent SCRV‐GM challenge with a relative percent survival (RPS) of 100% on 18th day post vaccination. Then, the wild type MSRV‐SS was purified by plaque clone assays, and the biological characteristics of the clonal strain designed as MSRV‐SS‐7 were investigated. The MSRV‐SS‐7 was avirulent to Chinese perch and its growth characteristic was similar to the MSRV‐SS. The immune protection effects of clonal MSRV‐SS‐7 against virulent SCRV‐GM were evaluated by intraperitoneal injection (IP) vaccination and immersion (IM) vaccination, their RPSs were all 100%. Altogether, these results indicate that MSRV‐SS‐7 is a potential live vaccine candidate against SCRV disease. Figure. No caption available. HighlightsA natural rhabdoviruses avirulent strain MSRV‐SS was picked out and its antigenicity was determined.The clonal strain MSRV‐SS‐7 was obtained by plaque purification and its bio‐characteristics were determined.Live MSRV‐SS‐7 protected Chinese perch against virulent SCRV by intraperitoneal injection or immersion immunization.