Sequence analysis of OmNramp α and quantitative expression of Nramp homologues in different trout strains after infection with Myxobolus cerebralis

Abstract

Salmonid whirling disease caused by the metazoan parasite Myxobolus cerebralis is an ongoing problem in wild and farmed rainbow trout Oncorhynchus mykiss populations. Rainbow trout from different strains vary in susceptibility to the parasite. Identification of underlying mechanisms could be a starting point for improved control of the disease. We conducted infection trials using 2 rainbow trout strains and brown trout Salmo trutta fario, a species not susceptible to the parasite, to investigate host immune response and resistance mechanisms. We compared expression levels of 2 natural resistance-associated macrophage proteins (Nramp α and β) after infection with M. cerebralis. Total RNA was extracted from skin, muscle, kidney, head and spinal column, and gene expression was quantified by real-time PCR. Significant decreases in expression of both genes were observed at different time points in the infected susceptible rainbow trout compared to the non-infected group. Furthermore, the OmNramp α (O. mykiss natural resistance-associated macrophage protein α) sequences in 2 resistant and 1 non-resistant rainbow trout strain were analysed and compared for sequence aberrations. © Inter-Research 2007.