Helminth trained nerve and airway associated interstitial macrophages are indispensable for mitigating pathology during respiratory viral infection 2302249

Introduction Disease severity following respiratory viral infection often poorly correlates with viral burden, implicating dysfunction of inflammation regulation in host. Lung-resident macrophages are central to pulmonary homeostasis, yet how distinct subsets mediate disease tolerance is unclear. We identified CD169+ nerve- and airway-associated interstitial macrophages (NAMs) that expand early after infection and hypothesized that NAMs acquire local trained immunity to promote disease tolerance during viral challenge. Methods Mice were transiently infected with the lung-migrating helminth Nippostrongylus brasiliensis and challenged 4—5 weeks later with lethal H1N1 influenza. Survival, weight loss, lung pathology, pulmonary function, and viral burden were assessed. Immune responses were analyzed by flow cytometry, cytokine profiling, and confocal microscopy. NAM dependency was tested using a NAM-DTR model to deplete trained NAMs and replace them with untrained cells. Single-cell RNA-seq and ATAC-seq were performed to define transcriptional and epigenetic programs. Results Prior helminth exposure induced a durable trained state that protected mice from influenza-induced weight loss and mortality without altering viral burden, indicating disease tolerance. Trained mice showed reduced lung pathology and improved gas exchange. Protection was associated with elevated type-2 cytokines and increased eosinophils, whereas untrained mice developed excessive neutrophilia and NET formation. NAMs expanded following helminth exposure and were essential for protection, as depletion and replacement of trained NAMs with untrained cells abolished survival. ScRNA-seq and ATAC-seq analyses revealed stable reprogramming of NAMs toward inflammation control, lung repair, and type-2 immunity. Conclusion These findings establish NAMs as critical mediators of pulmonary disease tolerance and demonstrate that lung-resident macrophages can acquire local trained immunity that preserves tissue integrity during severe viral infection. Funding Source 5F32HL154598 (P.D.Y.), 5T3-A1100853 (P.D.Y.) R01AI188824, 1R01AI143861 (K.M.K.), 3R01AI143861-02S1 (K.M.K.), NYU Cardiovascular Research Center pilot award (K.M.K.)