Humoral immune response of European eel Anguilla anguilla experimentally infected with Anguillicola crassus

A humoral immune response of the European eel Anguilla anguilla elicited by an experimental infection was demonstrated for the first time against the swimbladder nematode Anguillicola crassus. Eels were experimentally infecte d once or repeatedly and the antibody response was observed over a period o f 325 d. Specific antibodies against A. crassus in the peripheral blood of the eels were measured using an ELISA and the immunoblot technique. Anti-A. crassus antibodies were first observed 8 wk post infection, and appeared t o be independent of both the number of infective third stage larvae (L-3) a dministered and the frequency of administration. However, individual eels s howed great differences in the course of the antibody response. The late ap pearance of antibodies in the peripheral blood supports the hypothesis that not the invading L-3 but rather the adult parasites elicit the production of specific antibodies. A stage-specific antibody response against the L-3 was not observed. Main antigens are located in the body wall, especially in the gelatinous outer cuticle, of adult A. crassus.