Investigation of the relationship between IL17A, IL17<underline>F</underline> and ILR1N polymorphisms and COVID-19 severity: The predictive role of IL17A rs2275913 polymorphism in the clinical course of COVID-19

Coronavirus disease 2019 (COVID-19) is an infectious respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although the mortality rate of the disease has been relatively under control as of 2022, more than 15 million confirmed COVID-19 cases have been detected in Turkey to date, causing more than 100,000 deaths. The clinical manifestation of the disease varies widely, ranging from asymptomatic to acute respiratory distress syndrome causing death. The immune response mechanisms have an important impact on the fine adjustment between healing and enhanced tissue damage. This study aims to investigate the relationship between the variants of the interleukin 1 receptor antagonist (IL1RN), interleukin 17A (IL17A), and interleukin 17F (IL17F) genes and COVID-19 severity. The study population comprised 202 confirmed COVID-19 cases divided into three groups according to severity. The IL1RN variable number of a tandem repeat (VNTR) polymorphism was genotyped by polymerase chain reaction (PCR), and IL17A rs2275913, IL17F rs763780 and rs2397084 polymorphisms were genotyped by the PCR-based restriction fragment length polymorphism method. Statistical analysis revealed a significant association between IL17A rs2275913 variant and COVID-19 severity. The AA genotype and the A allele of IL17A rs2275913 were found significant in the severe group. Additionally, we found a significant relationship between haplotype frequency distributions and severity of COVID-19 for the IL17F rs763780/rs2397084 (p = 0.044) and a combination of IL17F rs763780/rs2397084/ IL17A rs2275913 (p = 0.04). The CG and CGA haplotype frequencies were significantly higher in the severe group. IL17A rs2275913, IL17F rs763780 and rs2397084 variants appear to have important effects on the immune response in COVID-19. In conclusion, variants of IL17A rs2275913, IL17F rs763780 and rs2397084 may be the predictive markers for the clinical course and potential immunomodulatory treatment options in COVID-19, a disease that has placed a significant burden on our country.