Abstract Chronic lower respiratory tract disease is a major cause of morbidity and mortality in the U.S. and worldwide. Currently there are no effective disease-modifying therapies and it remains unclear how to define and optimally treat disease endotypes within the spectrum of asthma and COPD (chronic obstructive pulmonary disease; chronic bronchitis and emphysema). This mechanistic research aims to define new pathways amenable to therapeutic intervention based on the role of diseased airway epithelial cells as an upstream driver of chronic airway disease. As a foundation for this proposal, multiple human clinical and translational studies as well as allergen- smoke- and virus-induced animal models have solidified the relevance of the pathogenic epithelial- derived cytokine IL-33 in COPD and asthma. However, a major knowledge gap that remains is understanding the mechanism by which nuclear-sequestered IL-33 can be activated and secreted from diseased airway cells to drive inflammation. Here we present preliminary data that demonstrates human COPD airway epithelial cells express increased levels of a truncated, spliced IL-33 isoform, which is capable of escaping nuclear sequestration to be abundantly secreted. Our analysis further revealed novel features of this secreted IL-33 isoform including post-translational modification, interaction with exosome-associated chaperones, and utilization of exosome trafficking pathways for secretion. Accordingly, this study aims to elucidate the impact of these newly-discovered features of IL-33 biology on the pathogenesis of chronic airway disease. Aim 1 will define how IL-33 interaction with exosomal chaperones enhances cytokine secretion and receptor activation to drive airway disease, using human cellular and mouse airway disease models coupled with validation in human airway disease specimens. Aim 2 will investigate the role of post-translational modification in augmenting IL-33 secretion and receptor activation to propagate disease, through an analogous approach using human cellular and mouse models with validation in human specimens. Together, these aims will address key steps in the pathologic sequence that initiates and sustains chronic airway disease, illuminating novel ways to target exosome-mediated cytokine secretion at the mucosal interface.