Juvenile, but Not Adult, Mice Display Increased Myeloid Recruitment and Extracellular Matrix Remodeling during Respiratory Syncytial Virus Infection

Early-life pulmonary viral infection leads to long-term functional and lower airway structural changes in the lungs

Early-life respiratory virus infections have been correlated with enhanced development of childhood asthma. In particular, significant numbers of respiratory syncytial virus (RSV)-hospitalized infants go on to develop lung disease. It has been suggested that early-life viral infections may lead to altered lung development or repair that negatively impacts lung function later in life. Our data demonstrate that early-life RSV infection modifies lung structure, leading to decreased lung function. At 5 wk postneonatal RSV infection, significant defects are observed in baseline pulmonary function test (PFT) parameters consistent with decreased lung function as well as enlarged alveolar spaces. Lung function changes in the early-life RSV-infected group continue at 3 mo of age. The altered PFT and structural changes induced by early-life RSV were mitigated in TSLPR-/- mice that have previously been shown to have reduced immune cell accumulation associated with a persistent Th2 environment. Importantly, long-term effects were demonstrated using a secondary RSV infection 3 mo following the initial early-life RSV infection and led to significant additional defects in lung function, with severe mucus deposition within the airways, and consolidation of the alveolar spaces. These studies suggest that early-life respiratory viral infection leads to alterations in lung structure/repair that predispose to diminished lung function later in life.NEW & NOTEWORTHY These studies outline a novel finding that early-life respiratory virus infection can alter lung structure and function long-term. Importantly, the data also indicate that there are critical links between inflammatory responses and subsequent events that produce a more severe pathogenic response later in life. The findings provide additional data to support that early-life infections during lung development can alter the trajectory of airway function.

Metatranscriptome Reveals Specific Immune and Microbial Signatures of Respiratory Syncytial Virus Infection in Children

Respiratory syncytial virus (RSV) is the most frequently detected respiratory virus in children with acute lower respiratory tract infection. Previous transcriptome studies have focused on systemic transcriptional profiles in blood and have not compared the expression of multiple viral transcriptomes. Here, we sought to compare transcriptome responses to infection with four common respiratory viruses for children (respiratory syncytial virus, adenovirus, influenza virus, and human metapneumovirus) in respiratory samples. Transcriptomic analysis showed that cilium organization and assembly were common pathways related to viral infection. Compared with other virus infections, collagen generation pathways were distinctively enriched in RSV infection. We identified two interferon-stimulated genes (ISGs), CXCL11 and IDO1, which were upregulated to a greater extent in the RSV group. In addition, a deconvolution algorithm was used to analyze the composition of immune cells in respiratory tract samples. The proportions of dendritic cells and neutrophils in the RSV group were significantly higher than those in the other virus groups. The RSV group exhibited a higher richness of Streptococcus than the other virus groups. The concordant and discordant responses mapped out here provide a window to explore the pathophysiology of the host response to RSV. Last, according to host-microbe network interference, RSV may disrupt respiratory microbial composition by changing the immune microenvironment. IMPORTANCE In the present study, we demonstrated the comparative results of host responses to infection between RSV and other three common respiratory viruses for children. The comparative transcriptomics study of respiratory samples sheds light on the significant roles that ciliary organization and assembly, extracellular matrix changes, and microbial interactions play in the pathogenesis of RSV infection. Additionally, it was demonstrated that the recruitment of neutrophils and dendritic cells (DCs) in the respiratory tract is more substantial in RSV infection than in other viral infections. Finally, we discovered that RSV infection dramatically increased the expression of two ISGs (CXCL11 and IDO1) and the abundance of Streptococcus.

The IRE1α-XBP1s Arm of the Unfolded Protein Response Activates N-Glycosylation to Remodel the Subepithelial Basement Membrane in Paramyxovirus Infection

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.

Defining the Versican Interactome in Lung Health and Disease

The extracellular matrix (ECM) imparts critical mechanical and biochemical information to cells in the lungs. Proteoglycans are essential constituents of the ECM and play a crucial role in controlling numerous biological processes, including regulating cellular phenotype and function. Versican, a chondroitin sulfate proteoglycan required for embryonic development, is almost absent from mature, healthy lungs and is re-expressed and accumulates in acute and chronic lung disease. Studies using genetically engineered mice show that the versican-enriched matrix can be pro- or anti-inflammatory depending on the cellular source or disease process studied. The mechanisms whereby versican develops a contextual ECM remain largely unknown. The primary goal of this review is to provide an overview of the interaction of versican with its many binding partners, the "versican interactome," and how through these interactions, versican is an integrator of complex extracellular information. Hopefully, the information provided in this review will be used to develop future studies to determine how versican and its binding partners can develop contextual ECMs that control select biological processes. While this review focuses on versican and the lungs, what is described can be extended to other proteoglycans, tissues, and organs.