Vibriosis is one of the most prevalent
fish diseases caused by bacteria belonging to the genus Vibrio.
Vibriosis caused by Vibrio anguillarum produces a 38-kDa major outer membrane
porin protein (OMP) for biofilm formation and bile resistant activity. The gene encoding the
porin was used to construct
DNA vaccine. The protective efficiency of such
vaccine against V. anguillarum causing acute vibrio
haemorrhagic septicaemia was evaluated in Asian seabass (Lates calcarifer Bloch), a common species of the Indian coast and a potential resource for the aquaculture industry. In vitro
protein expression of
porin gene was determined by fluorescent microscopy after transfection of seabass kidney cell line (SISK). Fish immunized with a single
intramuscular injection of 20 microg of the OMP38
DNA vaccine showed significant serum antibody levels in 5th and 7th weeks after vaccination, compared to fish vaccinated with the control eukaryotic expression vector pcDNA3.1. Asian seabass vaccinated with the OMP38
DNA vaccine was challenged with pathogenic V. anguillarum by
intramuscular injection. A relative percent survival (RPS) rate of 55.6% was recorded. Bacterial agglutination and serum
complement activity was analysed by using
DNA vaccinated seabass serum above 80% of analysed strain was killed at the highest agglutination titre. Histopathological signs of V. anguillarum challenged fish were observed in around 45% of pVAOMP38, 90% of PBS and 87% of pcDNA3.1-vaccinated control fish. The results indicate that L. calcarifer vaccinated with a single dose of
DNA plasmid encoding the major outer
membrane protein shows moderate protection against acute
haemorrhagic septicaemia and mortality by V. anguillarum experimental
infection.