PRR polymorphisms in patients hospitalized for COVID-19

SARS-CoV-2 infection causes an innate immune response that is activated through pattern-recognition receptors (PRRs), including Toll-like receptors (TLRs) and RIG-I-like receptors (RLRs). Endosomal TLR7/8 detects viral ssRNA, while TLR3 also recognizes dsRNA formed during viral replication. Both RIG-I and MDA5 recognize SARS-CoV-2 RNA in the cytoplasm of infected cells. PRR pathways recruit essential downstream adapter proteins to induce type I interferons (IFNs) and inflammatory cytokines. PRR polymorphisms were genotyped in 261 individuals, including 166 patients hospitalized for COVID-19, and evaluated their associations with clinical parameters and serum cytokine profiles. Single-nucleotide polymorphisms (SNPs) of TLR3 (rs3775290 and rs3775291), TLR7 (rs179008, rs3853839, and rs5741880), TLR8 (rs3764879 and rs3764880), IFIH1 rs1990760, and DDX58 rs73479410 were genotyped using qPCR allelic discrimination, while TLR3 rs3775296 was analyzed by PCR-RFLP. Cytokine concentrations were quantified in 57 COVID-19 patients using MILLIPLEX Magnetic Bead Panels and Luminex xMAP technology.