Variant rs4986790 of toll-like receptor 4 affects the signaling and induces cell dysfunction in patients with severe COVID-19.

Objectives: We investigated the expression of toll-like receptor (TLR)-4 on the cell surface of innate and adaptive cells from patients with COVID-19 carrying the rs4986790 GG genotype in the TLR4 gene and the functional profile of these cells.

Methods: We included 1169 hospitalized patients with COVID-19. The rs4986790 in TLR4 was identified by real-time polymerase chain reaction. Peripheral blood mononuclear cells were isolated and cultured to evaluate TLR-4 expression on immune cells. Supernatants recovered culture assays were stored, and we measured cytokines and cytotoxic molecules.

Results: We showed that the rs4986790 (GG) was significantly associated (P = 0.0310) with severe COVID-19. Cells of patients with COVID-19 carrying the GG genotype have increased the frequency of monocytes and activated naïve and non-switched B cells positive to TLR-4 when cells are stimulated with lipopolysaccharide and with spike protein of SARS-CoV-2. Also, cells from patients with GG COVID-19 cannot produce pro-inflammatory cytokines after lipopolysaccharide stimulus, but they are high producers of cytotoxic molecules at baseline.

Conclusions: The rs4986790 GG genotype of the TLR4 is associated with the risk of COVID-19 and acute respiratory distress syndrome. Peripheral blood mononuclear cells of patients carrying the rs4986790 (TLR4) GG genotype had a limited delivery of pro-inflammatory cytokines compared to the AA and AG genotypes in which TLR-4 stimulation induces IL-10, IL-6, tumor necrosis factor-α, and Fas ligand production.