ROUTE OF VACCINE ADMINISTRATION - EFFECTS ON THE SPECIFIC HUMORAL RESPONSE IN RAINBOW-TROUT ONCORHYNCHUS-MYKISS

The specific humoral response of teleost fish to extracellular bacteri a was examined using a rainbow trout- Vibrio anguillarum model. Treatm ent groups were immunized by oral, immersion, and injection routes. Al l 3 delivery methods conferred full protection in controlled laborator y challenges (p < 0.01). Prior to boosting, serum antibody titers did not correlate with protection in the orally and immersion-vaccinated g roups, but, contrary to previous studies, titers measured 10 and 17 d after boosting correlated positively with protection in all 3 vaccinat ed groups. The route of administration strongly affected the magnitude of the antibody response as measured by enzyme-linked immunosorbent a ssay (ELISA) and Western blots; however, the antigenic epitopes recogn ized were not substantially altered by delivery method as evidenced in immunoblot patterns. Given that the primary and booster vaccination p rotocols were identical, the data suggest that all 3 vaccinated groups may have had a specific humoral response following initial immunizati on but that specific serum antibody levels before boosting were too lo w to be detected by ELISA in fish vaccinated by oral and immersion rou tes. An anamnestic response was evident in all 3 groups. The data supp ort the possibility that teleosts, like higher vertebrates, have a pro tective immune response to extracellular bacteria that is predominantl y humoral. Route of delivery may primarily affect the efficiency with which the immunogenic constituents of the vaccine are presented to the relevant recognition and effector components of the immune system.