Dynamic expression of immune response genes in the sea bass, Dicentrarchus labrax, experimentally infected with the monogenean Diplectanum aequans.

The sea bass, Dicentrarchus labrax, is one of the most extensively farmed marine fishes in the Mediterranean. Under the high-density condition common in aquaculture, the monogenean gill parasite Diplectanum aequans can cause significant economic losses. This study used real-time quantitative PCR to investigate the dynamic expression of immune response genes in sea bass infected with Diplectanum aequans. The target genes, interleukin-1 (IL-1beta, transforming growth factor (TGF-beta and T-cell receptor (TCR-beta), were studied in the gills and spleen of the sea bass from the first day of infection until thirty days post- infection. Our results showed that there was an increase in IL-1beta gene expression in the spleen and gills and in TGF-beta gene expression in the gills of infected fish. These results show that parasitic infection induced a local inflammatory reaction and that reaction was restricted to the site of infection. Finally, the absence of relationship between TCR-beta expression and the parasitic infection suggests that the adaptive immune system is not involved in the response against this parasite.