HLA-C and viral infectious disease: The HLA system containing nearly 27,000 alleles in classes I, II, and III is an exceedingly polymorphic region.115,116 Genetic variations across the HLA-A, HLA-B, HLA-C, HLA-DR, HLA-DP, and HLA-DQ genes, which encode MHC molecules, might change the process of viral infection by differentially mediating antiviral immunity.109,117 Several studies suggest that there may be specific risk and protective HLA alleles or haplotypes for COVID-19 incidence and mortality.9.