The toll-like receptor 4 Asp299Gly variant: no influence on LPS responsiveness or susceptibility to pulmonary tuberculosis in The Gambia

SETTING Tuberculosis (TB) remains a major cause of morbidity and mortality worldwide. Studies in a murine model of pulmonary TB have identified a role for Toll-like receptor 4 (TLR4) in the development of chronic lung infection with Mycobacterium tuberculosis. The Asp299Gly polymorphism in the human TLR4 gene is associated with in vivo hyporesponsiveness to lipopolysaccharide (LPS) in Caucasians. OBJECTIVE To determine whether TLR4 Asp299Gly influences LPS responses or susceptibility to pulmonary TB in humans in a Gambian population sample. DESIGN We compared whole blood monokine responses to LPS in 245 healthy blood donors stratified by TLR4 Asp299Gly genotype to assess whether this polymorphism was functional in this population. A case-control study of 640 subjects was conducted to investigate whether TLR4 Asp299Gly was associated with TB. RESULTS LPS-induced tumour necrosis factor, interleukin-1 beta and interleukin-10 production was not influenced by TLR4 Asp299Gly genotype. There was no association between TLR4 Asp299Gly and TB. CONCLUSION Our data suggest that TLR4 Asp299Gly has no influence on monocyte LPS responses or susceptibility to TB in Gambians and could be an ancient neutral polymorphism.