<i>IL17F</i>: A Possible Risk Marker for Spondyloarthritis in <i>HLA-B*27</i> Negative Brazilian Patients

HLA-B*27 is an important marker for spondyloarthritis (SpA), however, many SpA patients are HLA-B*27 negative. Thus, the aim of this study was to investigate the influence of IL17, TNF and VDR gene polymorphisms in SpA patients who were HLA-B*27 negative. This case-control study was conducted in 158 patients [102 patients with ankylosing spondylitis (AS) and 56 with psoriatic arthritis (PsA)] and 184 controls. HLA-B*27 genotyping was performed using PCR-SSP and IL17A (rs2275913), IL17F (rs763780), TNF-308 (rs1800629), TNF-238 (rs361525), FokI C>T (rs2228570), TaqI C>T (rs731236), ApaI A>C (rs7975232), and BsmI C>T (rs1544410) using PCR-RFLP. Statistical analyses were performed by Chi-square and logistic regression using OpenEpi and SNPStats software. The IL17F C allele frequency was higher in patients with SpA, AS and PsA compared to controls. The IL17F T/C genotype frequency was higher in SpA patients in an overdominant inheritance model and when men and women were separately analyzed. IL17A_IL17F AC haplotype was significantly associated to the risk for SpA patients. As for VDR, the ApaI a/a was a potential risk factor for SpA in men. In conclusion, IL17F C variant contributed to the risk of SpA in Brazilian patients who were HLA-B*27 negative and could be a potential marker for SpA