Anti-Idiotype Vaccine Provides Protective Immunity Against Vibrio Harveyi in Grouper (Epinephelus Coioides)

Since anti-idiotype antibodies (anti-Id Abs) can display internal images similar to the epitopes of the original antigens, we aimed to produce an effective vaccine based on anti-Id Abs to protect grouper from Vibrio harveyi. Anti-Id IgG showing V. harveyi-like internal images was produced from rabbits immunized with the Id portion of grouper anti-V. harveyi antibodies and its Fab portion, anti-Id IgG (Fab), was then prepared to use as the anti-Id vaccine. The resulting anti-Id IgG (Fab) was intraperitoneally injected twice at a 21-day interval into grouper to evaluate its ability to induce effective anti-V. harveyi immunity and protection, in comparison with inactivated V. harveyi bacteria. We found that administration of grouper with anti-Id IgG (Fab) resulted in enhanced V. harveyi-specific serum titers, as well as lymphocyte proliferation. In addition, three weeks after boosting, 90% (18/20) of fish immunized with anti-Id IgG (Fab) survived at least 28 days after a lethal challenge of the heterologous, virulent strain of V. harveyi. The capability of this anti-Id IgG (Fab) to imitate the epitopes of V. harveyi antigens and effectively induce protective immunity would be advantageous for its application in developing an efficacious vaccine against V. harveyi for future farm use in fish.