Respiratory syncytial virus (RSV) causes severe lower respiratory tract infections (LRTI) associated with decreased pulmonary function, asthma, and allergy. Recently, we demonstrated that RSV induces the hexosamine biosynthetic pathway via the unfolded protein response (UPR), which is a pathway controlling protein glycosylation and secretion of the extracellular matrix (ECM). Because the presence of matrix metalloproteinases and matricellular growth factors (TGF) is associated with severe LRTI, we studied the effect of RSV on ECM remodeling and found that RSV enhances the deposition of fibronectin-rich ECM by small airway epithelial cells in a manner highly dependent on the inositol requiring kinase (IRE1α)–XBP1 arm of the UPR. To understand this effect comprehensively, we applied pharmacoproteomics to understand the effect of the UPR on N-glycosylation and ECM secretion in RSV infection. We observe that RSV induces N-glycosylation and the secretion of proteins related to ECM organization, secretion, or proteins integral to plasma membranes, such as integrins, laminins, collagens, and ECM-modifying enzymes, in an IRE1α–XBP1 dependent manner. Using a murine paramyxovirus model that activates the UPR in vivo, we validate the IRE1α–XBP1-dependent secretion of ECM to alveolar space. This study extends understanding of the IRE1α–XBP1 pathway in regulating N-glycosylation coupled to structural remodeling of the epithelial basement membrane in RSV infection.

Initiated in the lower airways, idiopathic pulmonary fibrosis (IPF) is a fatal disease that disrupts the lung’s functional architecture, for which therapeutics are of limited efficacy; consequently, the disease is progressive and incurable. New therapeutic approaches providing delivery of mechanism-modifying drugs directly to the diseased regions may maximize therapeutic effects while minimizing systemic exposure. In this context, inhalable nanomedicine is an emerging approach for targeted pulmonary delivery, enabling a highly localized therapeutic effect. However, successful clinical translation is hindered by complex biological and engineering challenges in the diseased lungs, including region-specific clearance mechanisms, mucosal airway obstruction, microenvironmental remodeling, and disrupted aerodynamics of particle deposition. This review highlights these critical obstacles in the context of lower airway pathology, focusing on the growing understanding of the epithelial–mesenchymal transition, basal lamina remodeling, and fibroblastic heterogeneity in IPF. Therapeutic payloads, including small molecules, antibodies, and peptides, are compared in terms of stability, targeting, and tissue access. We further discuss emerging nanoparticle-based strategies designed to overcome these pulmonary barriers, with a focus on dendron micelles, dendrimer–peptide conjugates, lipopeptides, and biological vesicles. Finally, we explore advances in formulation engineering and aerosol generation technologies that are shaping the path toward clinically translatable inhalable nanomedicines.

Respiratory syncytial virus (RSV), a member of the genus Orthopneumovirus, is an etiological agent in infant lower respiratory tract infections (LRTIs) producing substantial global morbidity. Here, secretoglobin (Scgb1a1)-derived progenitors play a primary role in triggering innate, inflammatory, and cell state transitions in response to RSV LRTIs. Whether RSV activation of innate signaling in this epithelial sentinel population leads to chronic airway disease is unknown. To understand the role of innate signaling in Scgb1a1-derived progenitors, a model of RSV post-viral disease (PVLD) was developed and studied in the presence or absence of RelA conditional knockout (CKO). Single-cell RNA sequencing (scRNA-seq) studies showed that RSV-PVLD induced a transition of atypical, differentiation-intermediate, alveolar type 2 (aAT2) cells characterized by tumor protein 63 (TRP63), aquaporin 3 (AQP3), and Itgβ4 expression, as well as changes in PDGFRβ mesenchyme. A single-cell trajectory analysis and lineage-tracing experiments using Scgb1a1 CreER^TM X mTmG mice demonstrated that the Scgb1a1+ populations were precursors to the aAT2 population. Mechanistically, we found that the formation of the aAT2 population was prevented by RelA CKO. A differential gene expression analysis revealed that RSV-PVLD coordinately upregulates nuclear receptor subfamily 1 group D (Nr1d1/2), clock and basic helix-loop-helix ARNT-like 1 (Bmal) genes both in the aAT2 cell and in its Pdgfrα+ mesenchymal niche in a RelA-dependent manner. A systematic analysis of intercellular epithelial–mesenchymal communication in the scRNA-seq data showed that the clock-dysregulated epithelial–mesenchymal niche produces aberrant ANGPTL4 expression. ANGPTL4 upregulation was confirmed by the measurement of both its mRNA and protein. Moreover, ANGPTL4 is biologically active in the BALF of RSV-PVLD mice, inhibiting lipoprotein lipase activity. We conclude that RSV-PVLD is mediated, at least in part, by RelA signaling in Scgb1a1-derived epithelial progenitors, dysregulating ANGPTL4 signaling in an epithelial–mesenchymal niche, resulting in persistence of atypical alveolar epithelial cells with dysregulated of clock gene expression.

Respiratory syncytial virus (RSV), a member of genus Orthopneumovirus, is an etiological agent in infant lower respiratory tract infections (LRTIs) producing substantial global morbidity. Here, secretoglobin (Scgb1a1)-derived progenitors play a primary role in triggering innate, inflammatory, and cell state transitions in response to RSV LRTIs. Whether RSV activation of innate signaling in this epithelial sentinel population leads to chronic airway disease is unknown. To understand the role of innate signaling in Scgb1a1-derived progenitors, a model of RSV-post viral disease (PVLD) was developed and studied in the presence or absence of RelA conditional knockout (CKO). In wild type mice, we observed persistence of atypical, differentiation intermediate, alveolar type 2 (aAT2) cells characterized by tumor protein 63 (Trp63), Aquaporin-3 (Aqp3) and Itgb4 expression. Mechanistically, we found the formation of aAT2 population was prevented by RelA CKO. Lineage tracing using Scgb1a1 CreER^TM X mTmG mice demonstrated that the Scgb1a1+ populations were precursors to the aAT2 population. Single-cell RNA sequencing (scRNA-seq) showed that RSV-PVLD coordinately upregulates Nuclear Receptor Subfamily 1 Group D (Nr1d1/2), Clock and Basic Helix-Loop-Helix ARNT Like 1 (Bmal) both in the aAT2 cell and its Pdgfra+-mesenchymal niche in a RelA-dependent manner. Systematic analysis of intercellular epithelial-mesenchymal communication in the scRNA-Seq data showed that the clock-dysregulated epithelial-mesenchymal niche produces aberrant Angptl4 expression. We conclude that RSV-PVLD is mediated, at least in part, by RelA signaling in Scgb1a1-derived epithelial progenitors dysregulating an aAT2-PDGFRa epithelial-mesenchymal niche associated with persistent RSV replication, ANGPTL4 signaling and inflammatory clock expression.