Toll-like receptor 2 type 1 and type 2 polymorphisms in different chicken breeds.

Toll-like receptors mediate immune responses via recognition of pathogen-associated molecular patterns. Polymorphisms of toll-like receptors may affect their recognition of pathogen-associated molecular patterns, leading to varied host resistance to pathogenic infections. However, little is known about the polymorphisms of chicken toll-like receptors (ChTLR) among breeds. In this study, we cloned ChTLR2 type 1 and type 2 genes from 7 chicken breeds and analyzed their sequences. It was found that there were 10 amino acid polymorphism sites in ChTLR2 type 1 and type 2, among which 6 sites were in type 1 (5 sites in the extracellular domain and 1 site in the cytoplasmic domain) and 4 sites were in type 2 (all 4 sites in the extracellular domain). These results demonstrate that ChTLR2 type 1 and type 2 genes are polymorphic among chicken breeds, suggesting a varied resistance among breeds of chicken. We found that Laiwu Black chicken breeds have distinctive polymorphic sites at I699T in the type 1 and H561R in the type 2 ChTLR2 gene. Beijing Fatty chickens have distinctive sites at Q45R in type 1 and V66L in type 2. Nongda No.3 Chickens have distinctive sites at L115P, H232Y, and T494A in type 1. Hy-Line variety brown chickens have distinctive sites at I311V in type 2. Beijing White 939 chickens have distinctive sites at E284G in type 1 and A22V in type 2. These findings may provide some clues toward understanding the resistance of lighter chickens to salmonellosis.