Association of HLA-G 3’UTR Polymorphisms with Soluble HLA-G Levels and Disease Activity in Patients with Rheumatoid Arthritis: A Case-Control Study

Abstract

ABSTRACTBackground: Human leukocyte antigen (HLA)-G antigens are inducible non-classical major histocompatibility complex class Ib molecules which play an important role in the regulation of inflammatory processes and immunomodulation in autoimmune diseases. There are controversial reports on the impact of HLA-G gene polymorphisms on rheumatoid arthritis (RA). This study aimed at examining the impact of 14 base pair (bp) ins/del (rs66554220) and +3142G>C (rs1063320) polymorphisms and correlating these with soluble HLA-G (sHLA-G) levels to understand the susceptibility to RA in our sample cohort.Methods: Genomic DNA from 140 RA patients and 125 healthy controls was isolated using the salting out method. The genotyping of two polymorphisms of HLA-G (+3142G>C and 14 bp ins/del) was done by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and PCR method, respectively. Levels of sHLA-G were estimated by ELISA and disease activity was calculated by disease activity score (DAS28-ESR).Results: The HLA-G +3142G>C polymorphism was found to be associated with a decreased risk of RA as attributed to recessive inheritance tested model results (OR = 0.4, 95%C.I. = 0.2–0.9, p = .0313*, GG + GC versus CC). Our finding did not support an association between HLA-G 14 bp ins/del variant and risk/protection of RA. The sHLA-G levels were significantly lower in +3142GG and +3142GC RA patients as compared to healthy controls.Conclusion: HLA-G +3142G>C gene polymorphism might decrease the risk of occurrence of RA in our sample cohort as +3142CC genotype is associated with increased sHLA-G levels.Abbreviations: HLA-G: human leukocyte antigen-G; RA: rheumatoid arthritis; MHC: major histocompatibility complex; UTR: untranslated region; URR: upstream regulatory region; SLE: systemic lupus erythematous; PCR-RFLP: polymerase chain reaction restriction fragment length polymorphism; sHLA-G: soluble HLA-G; bp: base pair; ACR/EULAR: American College of Rheumatology/European League against Rheumatism; RF: rheumatoid factor; Anti-CCP: anti-cyclic citrullinated peptide; DAS28-ESR: Disease Activity Score 28- Erythrocyte Sedimentation Rate; TJC: tender joint count; SJC: swollen joint count; ESR: erythrocyte sedimentation rate; PGA: patient global assessment; HTN: hypertension; DM: diabetes mellitus; TB: tuberculosis; IEC: Institute Ethics Committee; ELISA: enzyme linked immunosorbent assay; ROC: receiver operating characteristics; AUC: area under curve; SNP: single nucleotide polymorphism; MTX: methotrexate; DMARDs: disease modifying anti-rheumatic drugs; Treg: regulatory T cells; IL: interleukinUnits: soluble HLA-G: Units/mL {U/mL}