Polymorphisms in toll-like receptor 1 and 9 genes and their association with tuberculosis susceptibility in Chinese Holstein cattle.

Toll-like receptors (TLRs) are a class of pattern recognition receptors that play a pivotal role in the innate and adaptive immune systems. Studies have shown that TLR variants play roles in various human infectious diseases. The aim of the present study was to investigate whether the functional genetic variations at positions C632T, G1409A, A1475C, G1550A and G1596A in TLR1 and at A2700G and A3156G in TLR9 confer susceptibility or resistance to bovine tuberculosis (bTB). Genotyping of the TLR1 and TLR9 gene polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and single-strand conformation polymorphism (PCR-SSCP) in 586 Chinese Holstein cows (154 infected with bTB, 432 non-infected). The frequencies of the GH and HH genotypes at TLR1-G1596A differed significantly between bTB-infected and non-infected animals [p=0.001 for both GH and HH; GH odds ratio (OR)=2.43 95% confidence interval (CI) (1.47-4.03); and HH OR=1.49 95% CI (0.85-2.62)]. There was a trend toward an increased relative risk of tuberculosis (TB) incidence in the CD genotype at the TLR1-A1475C locus [p=0.056, OR=1.59 95% CI (0.98-2.58)]. The present study suggests that variants in the TLR1 gene are associated with susceptibility to bTB, whereas no significant association can be inferred from the polymorphisms in the TLR9 gene.