High expression of interleukin-18 receptor alpha correlates with severe respiratory viral disease and defines T cells with reduced cytotoxic signatures.

Hyperactivated immunity underpins severe outcomes of respiratory viral infections, yet specific immune perturbations are ill-defined. Our recent findings identified OLAH (oleoyl-ACP-hydrolase) as a driver of life-threatening viral diseases. In the same patient cohorts, we now identify the gene encoding IL-18Rα chain (IL18R1), as being highly expressed in life-threatening influenza, COVID-19, RSV and multisystem inflammatory syndrome in children (MIS-C) and demonstrate markedly elevated surface protein IL-18Rα expression on CD8 T cells in these infections. Using a mouse model of severe influenza, we further show that high IL-18Rα expression on effector T cells is associated with increased disease severity. We find that IL-18Rα expression on CD8 T cells is inversely associated with cytotoxicity-related genes, including granzyme A, granzyme B, perforin, Eomes, and KLRG-1. Our study demonstrates that IL-18Rα is associated with severe and fatal respiratory disease outcomes and proposes the use of IL-18Rα as a potential biomarker for severe respiratory viral disease.