An overview of cytokine used as adjuvants in fish: current state and future trends

Abstract Vaccination is the most appropriate way to control pathogens that threaten the global aquaculture industry. Unfortunately, vaccines generally do not provide satisfactory immune protection, especially those based on inactivated pathogens or recombinant antigens. Thus, it is necessary for adjuvants or immunostimulants to be used to improve the vaccine efficacy. Traditional adjuvants such as aluminium salts adjuvant and Freund’s adjuvant, are the most effective known adjuvants in aquaculture; however, due to their disadvantages, such as low adjuvanticity, short lasting time and serious side effects in vivo were also occurred. Searching for some combinations or alternative molecules of them as adjuvants is feasible to increase animal welfare without lowering the levels of immune protection. Recent advances in immunology confirmed that cytokines used as adjuvants have the advantages of eliciting the expression of costimulatory molecular and polarization of antigen‐presenting cells compared with aluminium slats adjuvant and oil adjuvant in fish farming. Moreover, the effects of most adjuvants are exerted mainly through the induction of cytokines production. Nowadays, cytokines have been evaluated for their abilities to offer effective adjuvant activities in both animal models and human studies. In this review, we summarized previous studies performed with different Th cytokines used as adjuvants on different types of fish vaccines, focusing on their protective efficacies and effects on the fish immune system as they delivered in vivo .