Understanding the complex mechanisms of the immune system in dealing with the COVID-19 infection, which is probably related to the polymorphism in cytokine and chemokine genes, can explain the pro-inflammatory condition of patients. Therefore, in this study, the relationship between the frequency of single nucleotide polymorphisms in the two pro-inflammatory genes dipeptidylpeptidase 9 (DPP9) and interferon alpha and beta receptor subunit 2 (IFNAR2) and the severity of COVID-19 was assessed. This study involved 954 COVID-19 patients, including 528 recovered and 426 deceased patients. To investigate the polymorphisms of IFNAR2 rs2236757 and DPP9 rs2109069, we used the polymerase chain reaction with the restriction fragment length polymorphism assay. The results showed that IFNAR2 rs2236757 A allele is related to the reduced severity of the disease, whereas the incidence of DPP9 rs2109069 A allele was higher among the deceased than recovered individuals. On the other hand, in people carrying the G allele in the DPP9 gene polymorphism and the allele A in the IFNR2 gene polymorphism, the improvement of the disease was significantly higher. In conclusion, the results showed that IFNAR2 rs2236757 A allele is related to the decrease in the severity of the disease, while the frequency of DPP9 rs2109069 A allele was higher in deceased people than in recovered people. This shows the important role of genes related to inflammatory responses as well as the role of genetic variants of these genes in the severity of COVID-19.
Keywords: COVID-19; DPP9 rs2109069; IFNAR2 rs2236757.