Acute Lung Injury Results from Innate Sensing of Viruses by an ER Stress Pathway

Incursions of new pathogenic viruses into humans from animal reservoirs are occurring with alarming frequency. The molecular underpinnings of immune recognition, host responses, and pathogenesis in this setting are poorly understood. We studied pandemic influenza viruses to determine the mechanism by which increasing glycosylation during evolution of surface proteins facilitates diminished pathogenicity in adapted viruses. ER stress during infection with poorly glycosylated pandemic strains activated the unfolded protein response, leading to inflammation, acute lung injury, and mortality. Seasonal strains or viruses engineered to mimic adapted viruses displaying excess glycans on the hemagglutinin did not cause ER stress, allowing preservation of the lungs and survival. We propose that ER stress resulting from recognition of non-adapted viruses is utilized to discriminate “non-self” at the level of protein processing and to activate immune responses, with unintended consequences on pathogenesis. Understanding this mechanism should improve strategies for treating acute lung injury from zoonotic viral infections. [Display omitted] •ER stress pathways can mediate immune recognition of zoonotic viruses•Glycosylation status of viral proteins regulates activation of ER stress•Acute lung injury from pandemic influenza viruses is dependent on this activation•Adaptation through glycan addition mediates immune escape of seasonal IAV Hrincius et al. show that the recognition of poorly glycosylated viral proteins of pandemic influenza by an ER stress pathway is utilized as an intracellular sensor of non-self at the level of protein processing and results in acute lung injury.