| Summary: | Amoebic gill disease (AGD) is a disease caused by the ectoparasite Neoparamoeba perurans whichaffects several cultured marine fish worldwide. The characterization of pro-inflammatory andimmune related genes at the mRNA level in AGD-affected Atlantic salmon gills was performed at10 days post-inoculation using 2D quantitative RT-PCR, a method of mapping transcriptionalresponses in tissues. This method is a variant of traditional quantitative RT-PCR whereby RNA wasextracted and reverse transcribed from gill samples obtained using a biopsy punch from designatedareas of the gill from fish. In theory this method could be used to map the transcriptional responsesthroughout the entire gill with the resolution of the mapped changes dependent on the number andsize of gill subsamples. In the present study we restricted our subsample area to eight 2 mm biopsypunches from the dorsal portion of the second left gill arch of each individual fish.The genes of interest were IL-1β, TNF-α, TCR-α chain, CD8, CD4, MHC-IIα, MHC-I, IgM andIgT. A significant increase in expression of the mRNA of all the genes was observed in the gills ofAGD-affected fish. Furthermore, a correlation analysis between CD8-α and TCR-α showed that themRNA expression of these two genes was strongly positively correlated (r = 0.9). Contrary toprevious studies, our data suggest that the parasite, N. perurans , elicits a classical inflammatoryresponse in the gills of AGD-affected fish and indicates that the mRNA expression of immunegenes within gill lesions misrepresents the cellular immune response in the gills during AGD.
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