Genetic variation in TLR10 is not associated with chronic Q fever, despite the inhibitory effect of TLR10 on Coxiella burnetii-induced cytokines in vitro

Coxiella burnetii, the causative agent of Q fever, is recognized by TLR2. TLR10 can act as an inhibitory receptor on TLR2-derived immune responses. Therefore, we investigated the role of TLR10 on C. burnetii-induced cytokine production and assessed whether genetic polymorphisms in TLR10 influences the development of chronic Q fever. HEK293 cells, transfected with TLR2, TLR10 or TLR2/TLR10, and human peripheral blood mononuclear cells (PBMCs) in the presence of anti-TLR10, were stimulated with C burnetii. In both assays, the absence of TLR10 resulted in increased cytokine responses after C burnetii stimulation. In addition, the effect of single nucleotide polymorphisms (SNPs) in TLR10 was examined in healthy volunteers whose PBMCs were stimulated with C burnetii Nine Mile or the Dutch outbreak isolate C burnetii 3262. Individuals bearing SNPs in TLR10 displayed increased cytokine production upon C burnetii 3262 stimulation. Furthermore, 139 chronic Q fever patients and 220 controls were genotyped for TLR10 N241H, 1775V and I369L. None of these polymorphisms were associated with increased susceptibility to chronic Q fever. In conclusion, TLR10 has an inhibitory effect on in vitro cytokine production by C. burnetii, but the presence of TLR10 polymorphisms does not lead to an increased risk of developing chronic Q fever. (C) 2015 Elsevier Ltd. All rights reserved.