Genetic mechanisms of critical illness in Covid-19

Host-mediated lung inflammation is present,1 and drives mortality,2 in critical illness caused by Covid-19.Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development.3 Here we report the results of the GenOMICC(Genetics Of Mortality In Critical Care)genome-wide association study(GWAS)in 2244 critically ill Covid-19 patients from 208 UK intensive care units(ICUs).We identify and replicate novel genome-wide significant associations,on chr12q24.13(rs10735079,p=1.65[Formula:see text]10-8)in a gene cluster encoding antiviral restriction enzyme activators(OAS1,OAS2,OAS3),on chr19p13.2(rs2109069,p=2.3[Formula:see text]10-12)near the gene encoding tyrosine kinase 2(TYK2),on chr19p13.3(rs2109069,p=3.98[Formula:see text]10-12)within the gene encoding dipeptidyl peptidase 9(DPP9),and on chr21q22.1(rs2236757,p=4.99[Formula:see text]10-8)in the interferon receptor gene IFNAR2.We identify potential targets for repurposing of licensed medications:using Mendelian randomisation we found evidence in support of a causal link from low expression of IFNAR2,and high expression of TYK2,to life-threatening disease;transcriptome-wide association in lung tissue revealed that high expression of the monocyte/macrophage chemotactic receptor CCR2 is associated with severe Covid-19.Our results identify robust genetic signals relating to key host antiviral defence mechanisms,and mediators of inflammatory organ damage in Covid-19.Both mechanisms may be amenable to targeted treatment with existing drugs.Large-scale randomised clinical trials will be essential before any change to clinical practice.