DNA vaccine-mediated innate immune response triggered by PRRs in teleosts

Aquacultured fish are threatened by many pathogens, often with serious consequences. Vaccination is one of the most effective tools for enhancing host immunity and protecting fish from infections. Vaccination with DNA vaccine is based on the administration of the gene encoding a vaccine antigen. Several effective DNA vaccines that encode viral or bacterial antigenic proteins have already been shown to be effective for cultured fish. This review summarizes current knowledge on fish DNA vaccines, and the mechanism of interaction between the DNA vaccines and host immunity, especially focusing on the enhancement of innate immunity mediated through direct-recognition of DNA vaccine by pattern recognition receptors (PRRs). To date, numerous fish PRR genes have been identified, and the primordial functions of PRRs involved in the innate immune response to viral and bacterial nucleic acids have been increasingly clarified. The evolutionary conservations and divergences in the PRR mechanisms of teleosts and mammals are focused on their molecular features and the recognition of DNA vaccine mediated by TANK binding kinase 1. In addition, the mechanism of type I interferon production in teleosts, which is enhanced after the recognition of cytosolic nucleic acids and current topics on DNA sensing by PRRs are also introduced.