Detection of serum and mucosal antibody production and antibody secreting cells (ASCs) in large yellow croaker (Pseudosciaena crocea) following vaccination with Vibrio harveyi via different routes

The kinetics of mucosal and serum antibody response as well as antibody secreting cells (ASCs) production were studied in large yellow croaker following vaccination with inactivated Vibrio harveyi by different routes: oral administration, intraperitoneal (IP) injection and immersion. Indirect ELISA was used to measure the antibody level in serum and cutaneous mucus, and ELISPOT was used to monitor the ASCs derived from gill, blood and head kidney. The data demonstrated that IP injection resulted in the highest antibody levels in the systemic circulation, whereas immersion induced significant antibody levels in mucous. As for the ASCs response, IP injection induced high numbers of ASCs in the head kidney and blood; oral intubation only induced a slight ASCs response in the head kidney; immersion induced a much stronger ASCs response in the gill. These results indicate that mucosal antibodies following immersion immunization are independent of a systemic response and more sensitive, since it could be triggered earlier than serum antibodies. The mucosal antibodies following IP injection immunization may depend on a systemic immune response. The protective effects of the three vaccination methods were compared by challenging with live V. harveyi. Survival of the three groups of vaccinated fish varied from 40 to 60%, while 100% mortality was found in control fish. Compared with IP and oral vaccination, immersion stimulated higher specific antibody titers in the mucosal system and achieved similar protection, so it is an effective and efficient method for immunizing a large number of fish against V. harveyi.