Analysis of innate immunity in the horse - a genomic approach

Innate immunity represents one of mechanisms underlying genetic resistance to intracellular bacteria. In laboratory mice, a specific gene (NRAMP1) controlling resistance and susceptibility to intracellular pathogens has been identified and other genes like iNOS, cytokine and/or MHC genes were shown to be involved. Genomic tools allow to analyze functional circuits and metabolic pathways, to identify specific genes and to dissect complex traits non only in model animal species. The aim of our work was to identify candidate genes involved in mechanisms of innate immunity in the horse and to investigate their polymorphism as a prerequisite for a functional genomic approach. Genes involved in antigen presentation (MHC class II - ELA-DR and DQB), in macrophage activation and regulation (interleukin12, interferon-gamma, tumor necrosis factor alpha and its receptor) and in iron metabolism (TfR, iNOS, NRAMP1) were analyzed. A second MHC DQB locus and new alleles were identified. The horse NRAMP1 gene was identified, sequenced and mapped to the chromosome 15. PCR-RFLP and PCR-SSCP techniques were used to analyze polymorphisms in the IFNG, TNFA and IL-12 genes. A GT microsatellite was found within the 3'UTR of the TNFR1 gene. The results will be used for expression analysis in macrophages infected with a model pathogen (Rhodococcus equi). (Texte intégral