Antigenicity and immunity of recombinant OmpAII from Aeromonas veronii and protection against virulent Aeromonas infections in Carassius auratus gibelio

Aeromonas spp. can infect a variety of aquatic and terrestrial animals including humans and cause motile aeromonad septicemia (MAS). OmpA is an important virulence factor of fish pathogens such as Aeromonas veronii and Aeromonas hydrophila. In the current study, we examined the antigenicity and immune efficiency of a recombinant protein OmpAII vaccine against a lethal challenge of A. veronii. The whole ompAII gene from A. veronii strain GZ09007 was successfully cloned and expressed in Escherichia coli. The affinity-purified rOmpAII emulsified with Montanide ISA 763 A adjuvant was used to immunize gibel carp(Carassius auratus gibelio). PBS-ISA763A emulsion and PBS were the controls. The relative survival of vaccinated versus PBS control fish against a lethal challenge of A. veronii strains GZ09007, YC170511, XZ180501 and A. hydrophila Hn099 on day 28 post immunization were 100, 100, 38 and 89%, respectively. The vaccinated fish produced continuously high specific antibody titers. The lysozyme(LZM) activity in the sera of rOmpAII-ISA763A immunized fish was significantly higher than the controls from 7d to 56d. However, the superoxide dismutase (SOD) activity of rOmpAII-ISA763A was significantly higher than the controls only on 14d, 42d and 56d. Therefore, The OmpAII from A. veronii GZ09007 displayed positive antigenicity and immunity against Aeromonas infection challenges and is a candidate as a commercial reagent.