Abstract: As a significant pattern-recognition receptor, toll-like receptor (TLR) is essential for the natural immunity. Its polymorphism has a profound influence on responses to a wide range of pathogens and is associated with resistance and susceptibility to diseases.【Objective】This study speculated on the polymorphisms of TLR4 and function analysis of the mutation (C1027A) in its coding sequence in Suzhong pig. 【Method】 PCR-SSCP was used to search the mutations of TLR4 in 127 samples of Suzhong pigs. The expression levels of TLR4 and proinflammatory cytokines TNF-α and IL-1β were detected by real-time PCR in porcine alveolar macrophages (PAMs) that were induced by LPS. And the PAMs were grouped by their different genotypes (CC and AC) in 1027 bp of coding sequence (CDS) to discuss whether this mutation of TLR4 influenced its sensitivity to LPS. 【Result】 Three SNPs were found, including G962A, C1027A and G960A, and the first two of them were nonsynonymous SNPs and C1027A changed the character of amino acid. LPS stimulation markedly increased TLR4 and proinflammatory cytokines TNF-α and IL-1β mRNA expression. And PAMs had different sensitivities and response to LPS between genotypes CC and AC of C1027A. 【Conclusion】The coding sequence of TLR4 was relatively conservative in Suzhong pig and this population had low polymorphism and genetic variation. The mutation in C1027A can affect the binding ability to LPS. So, allele C in 1027 bp of TLR4 is the resistance allele to Gram-negative bacterial infections in Suzhong pig.

Key words: Suzhong pig, TLR4, PCR-SSCP, LPS, TNF-α, IL-1β