Cellular and molecular mechanisms of mucosal organ crosstalk in allergic diseases

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Abstract Allergic diseases including food allergies and allergic asthma represent a substantial health and economic burden, with the US Centers for Disease Control (CDC) estimating more than 50 million people within the US suffering from some form of allergic disease. The natural history of allergic diseases suggests immunological crosstalk between mucosal organs contributes to the co-occurrences of allergic diseases (e.g. food allergy and asthma) within the same individual, although the cellular and molecular mechanisms that underly this process have not been defined and represent a critical knowledge gap. Using in vivo mouse models we have shown that intragastric administration of allergen (ovalbumin, OVA) to OVA-sensitized mice not only elicits local eosinophilic inflammation within the allergen-exposed intestine, but also increases the frequency and alters the activation phenotype of tissue eosinophils within the allergen non-challenged, remote lung. Presence of inflammatory eosinophils within the remote lung are associated with mucous metaplasia and airway priming; the latter evidenced by generation of an exacerbated allergic airway inflammatory response upon subsequent inhalation of sub-optimal doses of an unrelated antigen (house dust mite). In contrast, intragastric OVA failed to enhance mucous metaplasia or airway priming in the remote lungs of eosinophil deficient mice. Collectively these prior data suggest intragastric challenge affects allergic susceptibility of the airways through dysregulation of lung tissue eosinophils. This proposal builds on these findings to investigate lung- and eosinophil-intrinsic mechanisms that underly intragastric allergen-driven dysregulation of remote lung eosinophils that lead to remote airway priming. We have found intragastric allergen challenge transiently alters the lung transcriptome, including induction of gene signatures implicated in eosinophil recruitment. Correlative analyses of serum proteins and blood eosinophil-expressed receptors further suggest systemic mediators and eosinophil-intrinsic factors contribute specifically to lung homing, including an eosinophil-derived subset of extracellular vesicles (EVs). Specific Aims test the central hypothesis: Intragastric allergen challenge activates 1) an IL-13:CCL11 axis in the remote lung via gut-derived type 2 innate lymphoid cells (ILC2s), and 2) IL-5/IL-33:ST2-dependent effects on circulating eosinophils that synergistically underly the dysregulation of tissue eosinophils within the remote lung. Our approach utilizes unique genetically modified mouse strains, including cytokine reporter mice and cell-targeted gene disruption, competitive adoptive transfer studies and innovative approaches to characterize eosinophil-derived extracellular vesicles. Translational approaches utilize human blood eosinophils. Completion of this proposal may offer important insights into immunological mechanisms that drive mucosal remote organ priming within the context of allergic inflammation, and as such is highly relevant to the development of better diagnostic and interventional approaches for patients with allergic diseases.