Immunisation of rainbow trout Oncorhynchus mykiss with a multiple antigen peptide system (MAPS)

To test the effectiveness of a multiple antigen peptide system (MAPS) as a method of vaccinating fish against peptides, rainbow trout were immunised with two MAPS containing the decapeptide GnRH. The first (MAPS 1) was homologous for GnRH, whereas the second (MAPS 2) was heterologous and contained alternating sequences of GnRH and a measles virus T cell epitope. Following vaccination with varying concentrations of the MAPS, serum antibody titres were monitored for 10 weeks. Only MAPS administered in adjuvant elicited an antibody response against GnRH. Whilst the kinetics of the responses mirrored those seen in sera from fish vaccinated against GnRH coupled to a carrier protein, the magnitude of the responses were significantly lower in sera from fish vaccinated with both MAPS. Interestingly, higher titres were seen against the MAPS than against GnRH in ELISA, possibly reflecting additional epitopes. The data are discussed with respect to the need to define T cell epitopes in fish, to allow the synthesis of more effective heterologous MAPS for future studies.