TLR3-Activated Monocyte-Derived Dendritic Cells Trigger Progression from Acute Viral Infection to Chronic Disease in the Lung

MAPK13 controls structural remodeling and disease after epithelial injury

All living organisms are charged with repair after injury particularly at epithelial barrier sites, but in some cases this response leads instead to structural remodeling and long-term disease. Identifying the molecular and cellular control of this divergence is key to disease modification. In that regard, stress kinase control of epithelial stem cells is a rational entry point for study. Here we examine the potential for mitogen-activated protein kinase 13 (MAPK13) regulation of epithelial stem cells using models of respiratory viral injury and post-viral lung disease. We show that Mapk13 gene-knockout mice handle acute infectious illness as expected but are protected against structural remodeling manifest as basal-epithelial stem cell (basal-ESC) hyperplasia-metaplasia, immune activation, and mucinous differentiation. In corresponding cell models, Mapk13-deficiency directly attenuates basal-ESC growth and organoid formation. Extension to human studies shows marked induction/activation of basal-cell MAPK13 in clinical samples of comparable remodeling found in asthma and COPD. Here again, MAPK13 gene-knockdown inhibits human basal-ESC growth in culture. Together, the data identify MAPK13 as a control for structural remodeling and disease after epithelial injury and as a suitable target for down-regulation as a disease-modifying strategy.

rWTC-MBTA Vaccine Induces Potent Adaptive Immune Responses Against Glioblastomas via Dynamic Activation of Dendritic Cells

Despite strides in immunotherapy, glioblastoma multiforme (GBM) remains challenging due to low inherent immunogenicity and suppressive tumor microenvironment. Converting "cold" GBMs to "hot" is crucial for immune activation and improved outcomes. This study comprehensively characterized a therapeutic vaccination strategy for preclinical GBM models. The vaccine consists of Mannan-BAM-anchored irradiated whole tumor cells, Toll-like receptor ligands [lipoteichoic acid (LTA), polyinosinic-polycytidylic acid (Poly (I:C)), and resiquimod (R-848)], and anti-CD40 agonistic antibody (rWTC-MBTA). Intracranial GBM models (GL261, SB28 cells) are used to evaluate the vaccine efficacy. A substantial number of vaccinated mice exhibited complete regression of GBM tumors in a T-cell-dependent manner, with no significant toxicity. Long-term tumor-specific immune memory is confirmed upon tumor rechallenge. In the vaccine-draining lymph nodes of the SB28 model, rWTC-MBTA vaccination triggered a major rise in conventional dendritic cell type 1 (cDC1) 12 h post-treatment, followed by an increase in conventional dendritic cell type 2 (cDC2), monocyte-derived dendritic cell (moDC), and plasmacytoid dendritic cell (pDC) on Day 5 and Day 13. Enhanced cytotoxicity of CD4+ and CD8+ T cells in vaccinated mice is verified in co-culture with tumor cells. Analyses of immunosuppressive signals (T-cell exhaustion, myeloid-derived suppressor cells (MDSC), M2 macrophages) in the GBM microenvironment suggest potential combinations with other immunotherapies for enhanced efficacy. In conclusion, the authors findings demonstrate that rWTC-MBTA induces potent and long-term adaptive immune responses against GBM.

Mitogen-activated protein kinase-guided drug discovery for post-viral and related types of lung disease

Respiratory viral infections are a major public health problem, with much of their morbidity and mortality due to post-viral lung diseases that progress and persist after the active infection is cleared. This paradigm is implicated in the most common forms of chronic lung disease, such as asthma and COPD, as well as other virus-linked diseases including progressive and long-term coronavirus disease 2019. Despite the impact of these diseases, there is a lack of small-molecule drugs available that can precisely modify this type of disease process. Here we will review current progress in understanding the pathogenesis of post-viral and related lung disease with characteristic remodelling phenotypes. We will also develop how this data leads to mitogen-activated protein kinase (MAPK) in general and MAPK13 in particular as key druggable targets in this pathway. We will also explore recent advances and predict the future breakthroughs in structure-based drug design that will provide new MAPK inhibitors as drug candidates for clinical applications. Each of these developments point to a more effective approach to treating the distinct epithelial and immune cell based mechanisms, which better account for the morbidity and mortality of post-viral and related types of lung disease. This progress is vital given the growing prevalence of respiratory viruses and other inhaled agents that trigger stereotyped progression to acute illness and chronic disease.

A potent MAPK13-14 inhibitor prevents airway inflammation and mucus production

Common respiratory diseases continue to represent a major public health problem, and much of the morbidity and mortality is due to airway inflammation and mucus production. Previous studies indicated a role for mitogen-activated protein kinase 14 (MAPK14) in this type of disease, but clinical trials are unsuccessful to date. Our previous work identified a related but distinct kinase known as MAPK13 that is activated in respiratory airway diseases and is required for mucus production in human cell-culture models. Support for MAPK13 function in these models came from effectiveness of MAPK13 versus MAPK14 gene-knockdown and from first-generation MAPK13-14 inhibitors. However, these first-generation inhibitors were incompletely optimized for blocking activity and were untested in vivo. Here we report the next generation and selection of a potent MAPK13-14 inhibitor (designated NuP-3) that more effectively downregulates type-2 cytokine-stimulated mucus production in air-liquid interface and organoid cultures of human airway epithelial cells. We also show that NuP-3 treatment prevents respiratory airway inflammation and mucus production in new minipig models of airway disease triggered by type-2 cytokine challenge or respiratory viral infection. The results thereby provide the next advance in developing a small-molecule kinase inhibitor to address key features of respiratory disease.NEW & NOTEWORTHY This study describes the discovery of a potent mitogen-activated protein kinase 13-14 (MAPK13-14) inhibitor and its effectiveness in models of respiratory airway disease. The findings thereby provide a scheme for pathogenesis and therapy of lung diseases [e.g., asthma, chronic obstructive pulmonary disease (COPD), Covid-19, postviral, and allergic respiratory disease] and related conditions that implicate MAPK13-14 function. The findings also refine a hypothesis for epithelial and immune cell functions in respiratory disease that features MAPK13 as a possible component of this disease process.

Murine Parainfluenza Virus Persists in Lung Innate Immune Cells Sustaining Chronic Lung Pathology

Respiratory viruses including the human parainfluenza viruses (hPIVs) are a constant burden to human health, with morbidity and mortality frequently increased after the acute phase of the infection. Although is proven that respiratory viruses can persist in vitro, the mechanisms of virus or viral products persistence, their sources, and their impact on chronic respiratory diseases in vivo are unknown. Here, we used Sendai virus (SeV) to model hPIV infection in mice and test whether virus persistence associates with the development of chronic lung disease. Following SeV infection, virus products were detected in lung macrophages, type 2 innate lymphoid cells (ILC2s) and dendritic cells for several weeks after the infectious virus was cleared. Cells containing viral protein showed strong upregulation of antiviral and type 2 inflammation-related genes that associate with the development of chronic post-viral lung diseases, including asthma. Lineage tracing of infected cells or cells derived from infected cells suggests that distinct functional groups of cells contribute to the chronic pathology. Importantly, targeted ablation of infected cells or those derived from infected cells significantly ameliorated chronic lung disease. Overall, we identified persistent infection of innate immune cells as a critical factor in the progression from acute to chronic post viral respiratory disease.

A potent MAPK13-14 inhibitor prevents airway inflammation and mucus production

Common respiratory diseases continue to represent a major public health problem, and much of the morbidity and mortality is due to airway inflammation and mucus production. Previous studies indicated a role for mitogen-activated protein kinase 14 (MAPK14) in this type of disease, but clinical trials are unsuccessful to date. Our previous work identified a related but distinct kinase known as MAPK13 that is activated in respiratory airway diseases and is required for mucus production in human cell-culture models. Support for MAPK13 function in these models came from effectiveness of MAPK13 versus MAPK14 gene-knockdown and from first-generation MAPK13-14 inhibitors. However, these first-generation inhibitors were incompletely optimized for blocking activity and were untested in vivo. Here we report the next generation and selection of a potent MAPK13-14 inhibitor (designated NuP-3) that more effectively down-regulates type-2 cytokine-stimulated mucus production in air-liquid interface and organoid cultures of human airway epithelial cells. We also show that NuP-3 treatment prevents respiratory airway inflammation and mucus production in new minipig models of airway disease triggered by type-2 cytokine challenge or respiratory viral infection. The results thereby provide the next advance in developing a small-molecule kinase inhibitor to address key features of respiratory disease.

An alternative mechanism for skeletal muscle dysfunction in long-term post-viral lung disease

Chronic lung disease is often accompanied by disabling extrapulmonary symptoms, notably skeletal muscle dysfunction and atrophy. Moreover, the severity of respiratory symptoms correlates with decreased muscle mass and in turn lowered physical activity and survival rates. Previous models of muscle atrophy in chronic lung disease often modeled chronic obstructive pulmonary disease (COPD) and relied on cigarette smoke exposure and LPS stimulation, but these conditions independently affect skeletal muscle even without accompanying lung disease. Moreover, there is an emerging and pressing need to understand the extrapulmonary manifestations of long-term post-viral lung disease (PVLD) as found in COVID-19. Here, we examine the development of skeletal muscle dysfunction in the setting of chronic pulmonary disease caused by infection due to the natural pathogen Sendai virus using a mouse model of PVLD. We identify a significant decrease in myofiber size when PVLD is maximal at 49 days after infection. We find no change in the relative types of myofibers, but the greatest decrease in fiber size is localized to fast-twitch-type IIB myofibers based on myosin heavy chain immunostaining. Remarkably, all biomarkers of myocyte protein synthesis and degradation (total RNA, ribosomal abundance, and ubiquitin-proteasome expression) were stable throughout the acute infectious illness and chronic post-viral disease process. Together, the results demonstrate a distinct pattern of skeletal muscle dysfunction in a mouse model of long-term PVLD. The findings thereby provide new insights into prolonged limitations in exercise capacity in patients with chronic lung disease after viral infections and perhaps other types of lung injury.NEW & NOTEWORTHY Our study used a mouse model of post-viral lung disease to study the impact of chronic lung disease on skeletal muscle. The model reveals a decrease in myofiber size that is selective for specific types of myofibers and an alternative mechanism for muscle atrophy that might be independent of the usual markers of protein synthesis and degradation. The findings provide a basis for new therapeutic strategies to correct skeletal muscle dysfunction in chronic respiratory disease.

Lung Remodeling Regions in Long-Term Coronavirus Disease 2019 Feature Basal Epithelial Cell Reprogramming

Respiratory viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can trigger chronic lung disease that persists and even progresses after expected clearance of infectious virus. To gain an understanding of this process, we examined a series of consecutive fatal cases of coronavirus disease 2019 (COVID-19) that came to autopsy at 27 to 51 days after hospital admission. In each patient, we identify a stereotyped bronchiolar-alveolar pattern of lung remodeling with basal epithelial cell hyperplasia, immune activation, and mucinous differentiation. Remodeling regions also feature macrophage infiltration and apoptosis and a marked depletion of alveolar type 1 and 2 epithelial cells. This entire pattern closely resembles findings from an experimental model of post-viral lung disease that requires basal-epithelial stem cell growth, immune activation, and differentiation. Together, the results provide evidence of basal epithelial cell reprogramming in long-term COVID-19 and thereby yield a pathway for explaining and correcting lung dysfunction in this type of disease.

An alternative mechanism for skeletal muscle dysfunction in long-term post-viral lung disease

Chronic lung disease is often accompanied by disabling extrapulmonary symptoms, notably skeletal muscle dysfunction and atrophy. Moreover, the severity of respiratory symptoms correlates with decreased muscle mass and in turn lowered physical activity and survival rates. Previous models of muscle atrophy in chronic lung disease often modeled COPD and relied on cigarette smoke exposure and LPS-stimulation, but these conditions independently affect skeletal muscle even without accompanying lung disease. Moreover, there is an emerging and pressing need to understand the extrapulmonary manifestations of long-term post-viral lung disease (PVLD) as found in Covid-19. Here, we examine the development of skeletal muscle dysfunction in the setting of chronic pulmonary disease using a mouse model of PVLD caused by infection due to the natural pathogen Sendai virus. We identify a significant decrease in myofiber size when PVLD is maximal at 49 d after infection. We find no change in the relative types of myofibers, but the greatest decrease in fiber size is localized to fast-twitch type IIB myofibers based on myosin heavy chain immunostaining. Remarkably, all biomarkers of myocyte protein synthesis and degradation (total RNA, ribosomal abundance, and ubiquitin-proteasome expression) were stable throughout the acute infectious illness and chronic post-viral disease process. Together, the results demonstrate a distinct pattern of skeletal muscle dysfunction in a mouse model of long-term PVLD. The findings thereby provide new insight into prolonged limitations in exercise capacity in patients with chronic lung disease after viral infections and perhaps other types of lung injury.

Age-Dependent Reduction in Asthmatic Pathology through Reprogramming of Postviral Inflammatory Responses

Asthma is a chronic disease of childhood, but for unknown reasons, disease activity sometimes subsides as children mature. In this study, we present clinical and animal model evidence suggesting that the age dependency of childhood asthma stems from an evolving host response to respiratory viral infection. Using clinical data, we show that societal suppression of respiratory virus transmission during coronavirus disease 2019 lockdown disrupted the traditional age gradient in pediatric asthma exacerbations, connecting the phenomenon of asthma remission to virus exposure. In mice, we show that asthmatic lung pathology triggered by Sendai virus (SeV) or influenza A virus is highly age-sensitive: robust in juvenile mice (4-6 wk old) but attenuated in mature mice (>3 mo old). Interestingly, allergen induction of the same asthmatic traits was less dependent on chronological age than viruses. Age-specific responses to SeV included a juvenile bias toward type 2 airway inflammation that emerged early in infection, whereas mature mice exhibited a more restricted bronchiolar distribution of infection that produced a distinct type 2 low inflammatory cytokine profile. In the basal state, aging produced changes to lung leukocyte burden, including the number and transcriptional landscape of alveolar macrophages (AMs). Importantly, depleting AMs in mature mice restored post-SeV pathology to juvenile levels. Thus, aging influences chronic outcomes of respiratory viral infection through regulation of the AM compartment and type 2 inflammatory responses to viruses. Our data provide insight into how asthma remission might develop in children.

Asthma reduces glioma formation by T cell decorin-mediated inhibition of microglia

To elucidate the mechanisms underlying the reduced incidence of brain tumors in children with Neurofibromatosis type 1 (NF1) and asthma, we leverage Nf1 optic pathway glioma (Nf1^OPG) mice, human and mouse RNAseq data, and two different experimental asthma models. Following ovalbumin or house dust mite asthma induction at 4-6 weeks of age (WOA), Nf1^OPG mouse optic nerve volumes and proliferation are decreased at 12 and 24 WOA, indicating no tumor development. This inhibition is accompanied by reduced expression of the microglia-produced optic glioma mitogen, Ccl5. Human and murine T cell transcriptome analyses reveal that inhibition of microglia Ccl5 production results from increased T cell expression of decorin, which blocks Ccl4-mediated microglia Ccl5 expression through reduced microglia NFκB signaling. Decorin or NFκB inhibitor treatment of Nf1^OPG mice at 4-6 WOA inhibits tumor formation at 12 WOA, thus establishing a potential mechanistic etiology for the attenuated glioma incidence observed in children with asthma.

Basal epithelial stem cells cross an alarmin checkpoint for postviral lung disease

Epithelial cells are charged with protection at barrier sites, but whether this normally beneficial response might sometimes become dysfunctional still needs definition. Here, we recognized a pattern of imbalance marked by basal epithelial cell growth and differentiation that replaced normal airspaces in a mouse model of progressive postviral lung disease due to the Sendai virus. Single-cell and lineage-tracing technologies identified a distinct subset of basal epithelial stem cells (basal ESCs) that extended into gas-exchange tissue to form long-term bronchiolar-alveolar remodeling regions. Moreover, this cell subset was selectively expanded by crossing a cell-growth and survival checkpoint linked to the nuclear-localized alarmin IL-33 that was independent of IL-33 receptor signaling and instead connected to autocrine chromatin accessibility. This mechanism creates an activated stem-progenitor cell lineage with potential for physiological or pathological function. Thus, conditional loss of Il33 gene function in basal epithelial cells disrupted the homeostasis of the epithelial barrier at skin and gut sites but also markedly attenuated postviral disease in the lung based on the downregulation of remodeling and inflammation. Thus, we define a basal ESC strategy to deploy innate immune machinery that appears to overshoot the primordial goal of self-defense. Our findings reveal new targets to stratify and correct chronic and often deadly postviral disease.

Nuclear IL-33 as a growth and survival agent within basal cells

IL-33 is a well-studied cytokine that resides normally within nuclei but can be released by cell damage or stress to then signal via a single receptor widely expressed on immune cells to promote host resistance and type 2 allergic immunity. In this issue of the JCI, Wu et al. used a well-established model of mouse Sendai viral infection to show that IL-33 was induced in distal lung airway epithelium, specifically in cell-cycling basal cells. IL-33 induced cell-cycling basal cells to expand and migrate into the alveolar compartment, presumably to restore barrier function. However, restoring barrier function with airway-derived cells may also result in persistent alveolar metaplasia. Surprisingly, nuclear IL-33 in this system acted cell autonomously, independently of release and conventional ST2 (IL1RL1) receptor signaling. The findings uncover a signaling role for nuclear IL-33 in viral activation of mouse basal cells and add to the well-known "alarmin" function of IL-33.