Specific immune response in mucosal and systemic compartments of Cirrhinus mrigala vaccinated against Edwardsiella tarda: In vivo kinetics using different antigen delivery routes

Abstract

Mucosal immune barriers confer protection against invading fish pathogens. Here, we conducted an experiment for 60 days to assess the mucosal and systemic immune response in Mrigal (Cirrhinus mrigala), an Indian major carp. Fish were immunized with inactivated Edwardsiella tarda by four different routes, namely, oral, immersion, injection, and anal intubation. An indirect enzyme‐linked immunosorbent assay (ELISA) was used to measure the specific immune response (antibody) in serum and mucus (collected from skin, gill, and gut) of the fish on 0, 15, 30, 45, and 60 days postimmunization. For specific immune response in the serum, significantly higher (p < 0.05) optical density (OD) values were obtained in the anal group (0.52 ± 0.03) and in the oral group (0.48 ± 0.03). In the skin mucus, significantly higher OD values were obtained in the oral group (0.48 ± 0.04) and immersion group (0.32 ± 0.03). In the gill mucus, significantly higher OD values were obtained in the oral group (0.82 ± 0.08) and the immersion group (0.73 ± 0.03). In the gut mucus, significantly higher OD values were obtained in the immersion group (0.080 ± 0.007) compared to the rest of the treatments. Fish from all the groups were challenged with LD50 dose of E. tarda at the end of the experiment. We conclude that oral and immersion immunization routes offer better protection of C. mrigala compared to other antigen delivery routes.