Interleukin-17F and interleukin-6 gene polymorphisms in Asian Indian patients with Takayasu arteritis

Objectives

To assess genetic association between single nucleotide polymorphisms (SNPs) in genes encoding T-helper cytokines and Takayasu Arteritis (TA) susceptibility in Asian Indian population.

Methods

In Phase-1, the genomic DNA of 120 TA patients and 119 healthy controls were genotyped for SNPs rs1800795 (interleukin (IL)-6), rs763780 (IL-17F), rs1800871, rs1800872, rs1800896 (IL-10) and rs1800468, rs1800469, rs1800470 (transforming growth factor-β). Allele frequencies between cases and controls were compared using chi-squared test and also reassessed empirically (p_e) by 10,000 permutations. In Phase-2, additional 98 TA patients and 101 controls were genotyped for replicating the significant associations noted in Phase-1 of the study.

Results

All 8 SNPs in Phase 1 were in Hardy-Weinberg proportions. The G allele at rs763780 (IL-17F) was significantly associated with TA (p = 0.014). We also found that rs1800795 (IL-6) was associated with tuberculosis (p = 0.001) under a dominant model. In Phase-2 replication part of the study, the rs763780 showed a trend towards association with TA (p = 0.08), and the magnitude and direction of the odds ratio (OR) also were consistent with results of Phase-1. In the combined analysis, protective association of the G allele of rs763780 with TA was again significant [OR (95% CI) = 0.44 (0.25–0.77); p = 0.0029]. The G allele was also significantly associated (p < 0.05) with underlying tuberculosis (TB) and occurrence of syncope in TA.

Conclusion

G allele of rs763780 in IL-17F gene was protectively associated against susceptibility to TA. GG genotypes of rs1800795 in IL-6 was also associated with occurrence of tuberculosis in our patients with TA.