Sex-Specific Association of Toll-like Receptor 8 Polymorphisms with COVID-19 Case Status in a Korean Population

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen of coronavirus disease 2019 (COVID-19). Toll-like receptor 8 (TLR8), which is located on the X chromosome, plays as a key mediator of the innate immune response. Genetic variation in the form of single-nucleotide polymorphisms (SNPs) within TLR8 has been linked to changes in the transcriptional activity of this gene. Thus, we aimed to identify TLR8 SNPs in the proximal promoter region and investigate whether these SNPs are associated with COVID-19 case status in a Korean population. We performed amplicon sequencing to investigate the genotypes and allele frequencies of regulatory SNPs in COVID-19 patients (n = 191) and the control group (n = 173). Four polymorphic sites, rs5741883, rs186566524, rs3764879, and rs3764880, were identified within the TLR8 proximal promoter. Given the X-linked nature of this locus, allele and genotype frequencies were computed independently by sex. Notably, the minor C allele at rs3764879 occurred at a markedly reduced rate among male patients (10%) relative to male controls (24%), corresponding to an OR of 0.35 (95% CI 0.15-0.8; p = 0.018; q = 0.036). A parallel pattern emerged for rs3764880, where the minor A allele was likewise underrepresented in male patients (9%) versus male controls (24%), yielding an OR of 0.3 (95% CI 0.12-0.7; p = 0.01; q = 0.036). By contrast, neither genotype nor allele distributions differed significantly between female patients and female controls for any of the four variants. These results indicate that the TLR8 polymorphisms rs3764879 and rs3764880 may be associated with COVID-19 case status among Korean males, although further validation in larger, independent cohorts is required.