Widespread gene-environment interactions shape the immune response to SARS-CoV-2 infection in hospitalized COVID-19 patients.

Genome-wide association studies performed in COVID-19 patients have uncovered various loci significantly associated with susceptibility to SARS-CoV-2 infection and disease severity. However, the underlying cis-regulatory genetic factors contributing to heterogeneity in the response to SARS-CoV-2 infection and their impact on clinical phenotypes remain enigmatic. Here, we use single-cell RNA-sequencing to quantify genetic contributions to cis-regulatory variation in 361,119 peripheral blood mononuclear cells of 63 acute COVID-19 patients, 39 convalescent samples, and 106 healthy controls. Expression quantitative trait loci mapping across cell types within each disease state group reveals thousands of cis-associated variants, of which hundreds are detected exclusively in immune cells derived from acute patients. Patient-specific genetic effects dissipate as infection resolves, suggesting that distinct gene regulatory networks are at play in the active infection state. Further, 20.3% of tested loci demonstrate significant cell state interactions with genotype, with pathways related to interferon responses and oxidative phosphorylation showing pronounced cell state-dependent variation, predominantly in CD14+ monocytes. Overall, we estimate that 16.8% of tested genes exhibit gene-environment interaction effects, highlighting the importance of environmental modifiers in the transcriptional regulation of the immune response to SARS-CoV-2. Our findings argue for the existence of extensive gene-environment effects among patients responding to an infection.