Epithelial Immune Cell Interactions in Persistent T2 Inflammation

Project 1: Epithelial Immune Cell Interactions in Persistent T2 Inflammation Project Summary Type-2 (T2) inflammation of the airways is an important therapeutic target in asthma, particularly for individuals who have persistent T2 inflammation despite adequate conventional therapy. Recent work from our laboratory demonstrates that mast cells (MC)s and eosinophils (Eos) infiltrate the airway epithelium in asthma in close association with airway dysfunction in the form of airway hyperresponsiveness (AHR) and have distinct spatial relationships with T2 airway inflammation. To model interactions between the epithelium and these classically defined innate effector cells, we developed models of primary airway epithelial cells (AECs) cocultured with these cells, revealing that both MCs and Eos engage in feed-forward loops that regulate epithelial gene expression in a manner that is accentuated when MCs are cocultured with primary AECs from children with asthma. We extended this model to ex vivo respiratory viral infection with human rhinovirus-A16 (RV16) and discovered bidirectional regulatory circuits including novel regulators of T2 gene expression by MCs. Our central hypothesis is that the epithelium acts in concert with MCs and Eos in the setting of respiratory viral infection to propagate inflammation through T2 and non-T2 mechanisms that lead to persistent T2 inflammation of the airways. We further hypothesize that these mechanisms are accentuated in individuals with T2-high asthma and that there are identifiable components of this T2 inflammation that persist despite corticosteroid treatment. Our initial results identified specific candidates for these bidirectional circuits between traditionally defined regulators of type-1 (T1) and type-3 (T3) inflammation and the persistence of T2 inflammation, including epithelial-derived interferons (IFN)s, IL-33, IL-36g, IL-18, and IL- 1b. We have also found that the epithelium promotes sustained T2 gene expression in MCs, which is only partly attenuated by maximal dose corticosteroids. This project will investigate the bidirectional interactions between MCs and Eos with primary AECs from individuals with T2-high as compared to non-T2 asthma and elucidate mechanisms by which RV16 infection and specific mediators induced by RV16 perpetuate inflammation. In Specific Aim 1, we examine epithelial-MC circuits, focusing on T1 and T3 signals that propagate T2 and other gene networks expressed in MCs and the components that are not sensitive to corticosteroids. In Specific Aim 2 we extend these results to examine how Eos and MCs act together as a functional unit within the epithelial microenvironment. In Specific Aim 3 we conduct ex vivo studies of airway cells from individuals with asthma and complement these studies with an in vivo human ICAM1 transgenic mouse model to examine the transcriptional response of MCs and Eos to epithelial-derived cytokines and infection with RV16. Completion of these studies will provide a better understanding of the interplay between the airway epithelium and relevant innate immune cells in the context of respiratory viral infection and the persistence of inflammation in the face of inhaled corticosteroid therapy. Project Number: 5U19AI175089-03 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: TEAL HALLSTRAND (+1 co-PI) | Institution: UNIVERSITY OF WASHINGTON, SEATTLE, WA | Award Amount: $247,508 | Activity Code: U19 | Study Section: ZAI1-JTS-I(J1) View on NIH RePORTER: https://reporter.nih.gov/project-details/5U19AI17508903