Characterization of Lung Eosinophil Subsets During Respiratory Viral Infection in Mice with Pre-Existing Immunity

Abstract

Abstract Eosinophils are critical cells in Type 2 immune responses and mucosal tissue homeostasis. Historically, lung eosinophilia has been linked to aberrant Th2 responses in response to inhaled allergens or as a consequence of vaccine-associated enhanced respiratory disease in viral infection. In some animal models of respiratory viral infection, lung eosinophilia has been observed in the absence of overt pathology. Here, we interrogated the phenotype and function of eosinophil subsets recruited to the lung after a sublethal, vaccine-matched intranasal challenge, modeling breakthrough infection. We observed an enrichment for eosinophils in the lungs of TIV-vaccinated mice post-challenge that were phenotypically similar to that of OVA-sensitized allergic mice, but with a marked absence of strong inflammatory cytokine signatures, detectable viral titers, and enhanced morbidity. Moreover, we did not observe an influx of eosinophils in the lungs of challenged unvaccinated mice, which were unable to control viral replication and had strong pro-inflammatory cytokine profiles. This suggests that vaccine-matched viral infection of the respiratory mucosa after priming with antigen in the periphery can result in lung eosinophilia that is neither pathological nor disease-enhancing, but correlates more so with clearance during a breakthrough infection. We longitudinally discerned the differential cellular kinetics of lung eosinophils and the lung microenvironment after breakthrough influenza infection or OVA sensitization across multiple parameters, including pathology. We are further analyzing the eosinophil compartment via RNA-seq, imaging, and spectral flow cytometry for in-depth characterization of this phenomenon. Supported by NIH Public Health Service Institutional Research T32 Training Award (AI07647) and Centers of Excellence for Influenza Research and Response (CEIRR) contract (75N93021C00014-0-9999-1).