Author Description

In the present thesis it was clearly demonstrated that sea bass is able to mount a specific antibody response to different antigens: Vibrio anguillarum, P. damselae ssp. piscicida and DNP. The kinetics of primary and secondary responses were studied in both intraperitoneally (ip) and direct immersion (di) vaccinated fish. While the head kidney was the main ASC-producing organ after ip immunisation, in the di immunised fish it was shown that the gills (and probably the skin) are likely to play a major role in the protection against natural challenges. In addition, a clear age effect was observed in the ASC responses of immersion vaccinated fish, with significantly higher numbers of ASC and faster ASC responses in the oldest groups. More importantly, there was no evidence that direct immersion exposure to P. damselae ssp. piscicida at the earliest stages used in the present study (0.1g) is tolerogenic. The kinetics and specificity of the invasion ability of P. damselae ssp. piscicida was studied and supported the results from others suggesting an intracellular phase to the life cycle of the bacterium. The fact that heat-inactivated antiserum obtained from sea bass immunised with a P. damselae ssp. piscicida bacterin reduced the invasiveness of the bacteria, strongly suggests that the antiserum contained antibodies against factors responsible for the adhesion and invasion of the pathogen. Intramolecular-induced suppression appears to play an important role in the regulation of the antibody response in sea bass, as suggested by the extremely low variability observed in the Ig L chain sequences obtained from DNP 494 -KLH immunised sea bass.