Association of Vitamin D Receptor Cdx-2 Polymorphism with COVID-19: A Case-Control Study

Background: Host genetic variability has been suggested as an important explanation for inter-individual differences in COVID-19 susceptibility and severity.Most vitamin D actions in the regulation of immunity are mediated by vitamin D receptors (VDRs).Polymorphisms in the VDR gene have been associated with several health outcomes; however, their effects on COVID-19 still need more clarification.This study aims to investigate the association of the VDR SNP (rs11568820, Cdx-2) with susceptibility and interindividual variability of the severity of COVID-19.Methods: A total of 100 confirmed COVID-19 patients and 100 age and sex-matched controls were enrolled in this study between July and September 2021.COVID-19 patients were further subdivided into severe (n ¼ 50) and nonsevere (n ¼ 50) cases.All participants were subjected to genotyping of Cdx-2 SNP using the allelic discrimination of the Realtime PCR technique and assay of serum 25(OH)D levels by ELISA.Results: The results showed that the homozygous "GG" genotype was significantly higher in patients vs. controls, whereas the heterozygous "AG" genotype was significantly lower in COVID-19 patients.Thus, the heterozygous "AG" genotype is considered the protective genotype.This protection was more significant among males vs. females (P ¼ 0.02).However, there were no statistically significant differences in the genotype distributions of VDR Cdx-2 SNP between severe and nonsevere patients.Moreover, COVID-19 patients with the "AG" genotype presented higher 25(OH)D levels than the "GG" genotype (P ¼ 0.02).Conclusions: VDR SNP (rs11568820, Cdx-2) might be a potential risk factor for COVID-19, particularly among male patients.