Single nucleotide polymorphisms in toll-like receptor 6 are associated with altered lipopeptide- and mycobacteria-induced interleukin-6 secretion

Toll-like receptors (TLRs) are critical mediators of the immune response to pathogens. The influence of human TLR6 polymorphisms on susceptibility to infection is only partially understood. Most microbes contain lipopeptides recognized by TLR2/1 or TLR2/6 heterodimers. Our aim was to determine whether single nucleotide polymorphisms in TLR6 are associated with altered immune responses to lipopeptides and whole mycobacteria. We sequenced the TLR6 coding region in 100 healthy South African adults to assess genetic variation and determined associations between polymorphisms and lipopeptide- and mycobacteria-induced interleukin (IL)-6 production in whole blood. We found two polymorphisms, C745T and G1083C, that were associated with altered IL-6 secretion. G1083C was associated with altered IL-6 levels in response to lipopeptides, Mycobacterium tuberculosis lysate (Mtb lysate, P =0.018) and Bacille Calmette-Guerin (BCG P =0.039). The 745T allele was also associated with lower NF- κ B signaling in response to di-acylated lipopeptide, PAM2 ( P =0.019) or Mtb ( P =0.026) in an HEK293 cell line reconstitution assay, compared with the 745C allele. We conclude that TLR6 polymorphisms may be associated with altered lipopeptide-induced cytokine responses and recognition of Mtb. These studies provide new insight into the role of TLR6 variation and the innate immune response to human infection.