Coronavirus disease-2019 (COVID-19) is pro-inflammatory disorder characterized by acute respiratory distress syndrome. Interleukin-6, a cytokine secreted by macrophages, which mediates an inflammatory response, is frequently increased and associated with the severity in COVID-19 patients. The differential expression of IL6 cytokine in COVID-19 patients may be associated with the presence of single nucleotide polymorphisms (SNPs) in regulatory region of cytokine genes. The aim of this study is to investigate the role of two promoter polymorphisms of the IL6 gene (-597G > A and -174G > C) with the severity of COVID-19. The study included 242 patients, out of which 97 patients with severe symptoms and 145 patients with mild symptoms of COVID-19. Genotyping of two selected SNPs, rs1800795 (-174G > C) and rs1800797 (-597G > A) of promoter region of IL6 gene, was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In our study, individuals with GC genotypes of IL6 (-174G > C) polymorphism showed significantly higher risk of severity [adjusted odds (OR) 3.86, p <.001] but we did not observe any association of COVID-19 severity with rs1800797 (-597G > A) polymorphism. The COVID-19 severity was significantly higher in individuals having 'C' allele of IL6 (-174G > C) polymorphism (p = .014). Linkage disequilibrium between rs1800795 (-174G > C) and rs1800797 (-597G > A) showed that individuals having AC* haplotype significantly association with COVID-19 severity (p = .034). Our results suggest that 'C' allele of rs1800795 (-174G > C) polymorphism of IL6 may be the risk allele for severity of COVID-19 in North Indian population.
Keywords: COVID-19; IL6; PCR-RFLP; SNPs; haplotype analysis; severity.
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