Association of TLR4 (896A/G and 1196C/T) Gene Polymorphisms with Asthma Risk: A Meta-Analysis

BACKGROUND: Conflicting data have been reported on the association between Toll-like receptor 4 (TLR4) +896A/G and +1196C/T polymorphisms and the risk of asthma. Therefore, we conducted this meta-analysis to clarify the effect of TLR4 +896A/G and +1196C/T polymorphisms on the risk of asthma. MATERIAL/METHODS: An electronic literature search was performed using PubMed, Embase, Web of Science, Chinese National Knowledge Infrastructure (CNKI), and Wanfang Data to find relevant studies. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the strength of the associations. All statistical analyses were conducted using STATA software version 12.0. RESULTS: A total of 14 studies with 2873 asthma cases and 3110 controls were included. The pooled results indicated a significant association between TLR4 +1196C/T polymorphism and the risk of asthma (T vs. C: OR=0.79, 95%CI=0.63–0.99, P=0.04; TT+CT vs. CC: OR=0.76, 95%CI=0.59–0.96, P=0.03; CT vs. CC: OR=0.74, 95%CI=0.58–0.95, P=0.02). In subgroup analysis by ethnicity, TLR4 +1196C/T polymorphism was significantly associated with asthma risk in Asians (T vs. C: OR=0.73, 95%CI=0.54–0.98, P=0.04; TT+CT vs. CC: OR=0.70, 95%CI=0.51–0.96, P=0.03; CT vs. CC: OR=0.69, 95%CI=0.50–0.96, P=0.03), but not in whites. For TLR4 +896A/G polymorphism, no significant association was found between TLR4 +896A/G polymorphism and asthma risk under any genetic models. CONCLUSIONS: The results of this meta-analysis suggest that T allele of the TLR4 +1196C/T might act as a protective factor against the development of asthma.