Genetic Polymorphism in TLR Genes of Chicken Lines Selected for Resistance or Susceptibility to Marek's Disease

Toll like receptor (TLR) genes are known to play an important role in innate immune competence through pattern recognition receptors by identifying the pathogen associated molecular patterns. Changes in amino acid sequences due to non-synonymous substitutions in TLR genes may alter the structure/functions of PRRs and hence disease resistance. Therefore, single nucleotide polymorphisms (SNPs) from coding regions of TLR genes in chicken lines selected for resistance or susceptibility to Marek’s disease were investigated. A total of 41 SNPs were detected in the 10 TLR genes screened, of which 20 were non-synonymous substitutions. Of particular note, 11 SNPs were detected in both TLR3 and TLR1LA genes including 8 and 3 non-synonymous SNPs, respectively. In the resistant line, two amino acid changes occurred in the extracellular leucine rich repeats (LRR), one each in the LRR_typical, transmembrane  and Toll interleukin 1- resistance (TIR) domains of TLR3 gene, whereas in the susceptible line, all 3 amino acid changes occurred in the extracellular LRR domain. This suggests that genetic polymorphisms of TLR genes, particularly for TLR3, might contributed to genetic resistance or susceptibility to Marek’s disease in these selected chicken lines.