Genetic evidence from proteome-wide analysis identifies plasma proteins driving risk of respiratory tract infections

BACKGROUND: Respiratory tract infections (RTIs) remain a major global cause of morbidity, yet the causal role of circulating plasma proteins in RTI susceptibility is unclear. We aimed to systematically identify plasma proteins that causally influence the risk of upper and lower respiratory tract infections (URTIs, LRTIs) using a proteome-wide Mendelian randomization (MR) framework. METHODS: We performed two-sample MR analyses using genetic instruments for 2923 plasma proteins from 54,219 UK Biobank participants and outcome data from the FinnGen consortium (97,696 URTI and 28,542 LRTI cases). Colocalization analyses were conducted to confirm shared genetic architecture. Functional enrichment and protein-protein interaction (PPI) analyses were used to elucidate potential biological pathways. RESULTS: We identified 11 plasma proteins with significant causal associations with RTI risk. Four proteins (FKBP1B, GFRA1, UBE2L6, and CSF3) showed consistent effects for both URTI and LRTI, with moderate-to-strong colocalization evidence for UBE2L6 and GFRA1. The remaining seven proteins demonstrated infection-specific associations: YAP1 and MST1 (URTIs), and APOE, IL1RL1, and FKBPL (LRTIs). PPI and Gene Ontology (GO) enrichment analyses highlighted tumor necrosis factor (TNF) as a central hub, with cytokine-cytokine receptor interaction and leukocyte-mediated immunity as dominant pathways. CONCLUSIONS: This proteome-wide MR and colocalization study identifies novel plasma proteins and immune pathways implicated in RTI susceptibility, providing insights into potential biomarkers and therapeutic targets for infection prevention and management. Further validation in diverse populations and tissue-specific proteomic studies is warranted.