Association of toll-like receptor 4 (TLR 4) gene exon 3 variants with serostatus of the ovine Johne's disease (paratuberculosis) in Turkish sheep

In the present study, the effect of exon 3 of the toll-like receptor 4 (TLR4) gene on ovine Johne's disease (OJD) serostatus was tested in Turkish sheep breeds. Initially, a retrospective cohort was performed using indirect ELISA on a commingled flock consisting of 3 native and 4 composite breeds (n = 1750). Case-control matched pairs were constructed according to the breed type and age (n = 188). Subsequently, exon 3 of the TLR4 gene was sequenced and coding variants were investigated. A total of 15 single nucleotide polymorphisms (SNPs) were detected and 12 of those SNPs were nonsynonymous. Next, 3 haplotype blocks consisting of these SNPs were constructed. The McNemar's test was conducted on both the SNPs and haplotypes. As a consequence, within the detection limits (power, 0.95; odds ratio > 3.3), no association was detected between the OJD serostatus and TLR4 exon 3 coding variants in Turkish sheep.