Co-administration of tilapia alpha-helical antimicrobial peptides with subunit antigens boost immunogenicity in mice and tilapia (Oreochromis niloticus)

Modern vaccines based on purified recombinant antigens have improved their safety; however they induce a suboptimal immune response without the help of adjuvants. Consequently, the development of new adjuvants to enhance the immunogenicity of purified subunit antigens and modulate resulting immune responses is of great interest. In the present study, we evaluated the ability of antimicrobial peptides Oreochromicins previously isolated from tilapia Oreochromis niloticus to enhance adaptive immune responses in mice and tilapia. When co-administrated with ovalbumin in mice, Oreochromicin-1 induced a T_H1 humoral immune response. Oreochromicin-2 and 3 induce a T_H1 cellular immune response characterized by the induction of interferon-γ in a dose depend manner. Additionally, co-administration of Oreochromicin-1 with the sea lice my32 from Lepeophtheirus salmonis antigen (my32-Ls) increases the humoral immune response in mice and tilapia. We also tested different combinations of these Oreochromicins with the sea lice antigen my32-Ls in mice. Humoral and cellular T_H1 responses were enhanced by co-administration of my32-Ls/Oreochromicin-3 and the combination my32-Ls/Oreochromicin-2/3. In agreement with these results, Oreochromicin-1 and 3 enhanced in vitro T_H1 cytokine IFN-γ production in Concanavalin A primed splenocytes from naïve mice after a 48 h incubation period. In summary, the results showed that tilapia alpha-helical antimicrobial peptides Oreochromicins are able to boost immune response in mammals and fish, encouraging their use as T_H1 molecular adjuvants to subunit antigens.