Relationship of Bovine SLC11A1 (Formerly NRAMP1) Polymorphisms to the Risk of Bovine Tuberculosis in Holstein Cattle

Many studies suggest significant genetic variation in the resistance of cattle and humans to infection with Mycobacterium bovis, the causative agent of zoonotic tuberculosis. The natural resistance associated macrophage protein 1 (NRAMP1), encoded by the SLC11A1 gene, plays a key role in the immunological control of a broad spectrum of infectious agents. The aim of the present study was to investigate the influence of single nucleotide polymorphisms (SNPs) of the SLC11A1 gene on bovine tuberculosis (bTB) susceptibility. We genotyped the SLC11A1 gene in 60 bTB-infected Holstein cows and 90 healthy control animals. The influence in the exon 4 and intron 4 regions of SLC11A1 genetic variations on bTB susceptibility was subsequently investigated by association analysis. Our finding demonstrated that the g.107117166A>G and g.107117369C>T polymorphisms of the SLC11A1 gene associated with bTB in Holstein cattle. The susceptibility of cattle with the g.107117166A>G genotype compared with the GG genotype was 3.40 (95% CI: 1.10-10.51; p=0.048) fold higher. The g. 107117166A>G SNP located in the exon 4 of the SLC11A1 gene and the functional consequence was missense. The deduced amino acid sequence for the protein product revealed an alanine to threonine conversion at position 96, which may affect initiation of protein synthesis and disrupt normal NRAMP1 function that protects animals against mycobacterial infection. The other susceptibility of cattle with the g.107117369C>T genotype compared with the TT genotype was 0.26 (95% CI: 0.12–0.56; p=0.001) fold lower. The g.107117369C>T polymorphism, located in the intron 4 of the SLC11A1 gene, may affect elements that control transcription and splicing of the NRAMP1 leading to affect pathophysiological characteristics in tuberculosis. This is the first report showing that the g. 107117166A>G and g.107117369C>T polymorphisms may contribute to SLC11A1-mediated bTB susceptibility.