Interleukin-17 (IL-17) and IL-17 receptor (IL-17R) signaling are essential for regulating mucosal host defense against many invading pathogens. Commensal bacteria, especially segmented filamentous ...bacteria (SFB), are a crucial factor that drives T helper 17 (Th17) cell development in the gastrointestinal tract. In this study, we demonstrate that Th17 cells controlled SFB burden. Disruption of IL-17R signaling in the enteric epithelium resulted in SFB dysbiosis due to reduced expression of α-defensins, Pigr, and Nox1. When subjected to experimental autoimmune encephalomyelitis, IL-17R-signaling-deficient mice demonstrated earlier disease onset and worsened severity that was associated with increased intestinal Csf2 expression and elevated systemic GM-CSF cytokine concentrations. Conditional deletion of IL-17R in the enteric epithelium demonstrated that there was a reciprocal relationship between the gut microbiota and enteric IL-17R signaling that controlled dysbiosis, constrained Th17 cell development, and regulated the susceptibility to autoimmune inflammation.
•SFB-induced Th17 cell expansion in the gut controls the degree of SFB colonization•IL-17R-dependent regulation of α-defensin, Nox1, and Pigr controls SFB•Intestinal IL-17R signaling regulates dysbiosis and autoimmune inflammation.
Segmented filamentous bacteria (SFB) regulate Th17 cell development in the gastrointestinal tract. Kolls and colleagues find that intestinal IL-17R signaling regulates the abundance of the gut microbiota and SFB specifically by promoting expression of antimicrobial factors. Abrogation of intestinal IL-17R signaling results in bacterial overgrowth and enhanced susceptibility to autoimmune inflammation.
The cytokine IL-17, and signaling via its heterodimeric IL-17RA/IL-17RC receptor, is critical for host defense against extracellular bacterial and fungal pathogens. Polarized lung epithelial cells ...express IL-17RA and IL-17RC basolaterally. However, their contribution to IL-17-dependent pulmonary defenses in vivo remains to be determined. To address this, we generated mice with conditional deletion of Il17ra or Il17rc in Scgb1a1-expressing club cells, a major component of the murine bronchiolar epithelium. These mice displayed an impaired ability to recruit neutrophils into the airway lumen in response to IL-17, a defect in bacterial clearance upon mucosal challenge with the pulmonary pathogen Klebsiella pneumoniae, and substantially reduced epithelial expression of the chemokine Cxcl5. Neutrophil recruitment and bacterial clearance were restored by intranasal administration of recombinant CXCL5. Our data show that IL-17R signaling in the lung epithelium plays a critical role in establishing chemokine gradients that are essential for mucosal immunity against pulmonary bacterial pathogens.
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•IL-17 receptor signaling in the lung epithelium is required for neutrophil recruitment•Conditional deletion of IL-17R in the lung epithelium impairs bacterial clearance•Expression of the chemokine Cxcl5 is reduced in the IL-17R-deficient epithelium•Recombinant CXCL5 administration restores neutrophil recruitment and bacterial clearance
IL-17 plays key roles in host defense, but the target cells in the lung are unclear. Chen et al. show that pulmonary epithelial IL-17R signaling is essential for regulating chemokine gradients, neutrophil recruitment, and bacterial clearance in the lungs. Epithelial administration of an IL-17R agonist may benefit patients with pneumonia.
Respiratory tract infections are a leading cause of morbidity and mortality in newborns, infants, and young children. These early life infections present a formidable immunologic challenge with a ...number of possibly conflicting goals: simultaneously eliminate the acute pathogen, preserve the primary gas-exchange function of the lung parenchyma in a developing lung, and limit long-term sequelae of both the infection and the inflammatory response. The latter has been most well studied in the context of childhood asthma, where multiple epidemiologic studies have linked early life viral infection with subsequent bronchospasm. This review will focus on the clinical relevance of respiratory syncytial virus (RSV), human metapneumovirus (HMPV), and rhinovirus (RV) and examine the protective and pathogenic host responses within the neonate.
Primary immunodeficiency disorders (PIDDs) describe a myriad of diseases caused by inherited defects within the immune system. As the number of identified genetic defects associated with PIDDs ...increases, understanding the incidence and outcomes of PIDD patients becomes imperative.
To characterize the frequency of new diagnoses, patterns of health care utilization, rates of hematopoietic stem cell transplantation (HSCT), and mortality in pediatric patients with PIDDs.
A retrospective cohort analysis of the Pediatric Health Information System database from 2004 to 2018 for pediatric inpatients with an International Classification of Diseases, Ninth and 10th Revisions (ICD-9/ICD-10). code associated with PIDD.
A total of 17,234 patients with a PIDD were hospitalized from 2004 to 2018. There were 2.8 new PIDD diagnoses and 6.3 PIDD hospitalizations per 1,000 discharges; these metrics were unchanged during the study period. The number of new diagnoses for B-cell and antibody defects significantly increased over time. The number of new PIDD diagnoses significantly increased in adolescents or adults and decreased in infants. T-cell disorders had the highest number of intensive care unit admissions. There were 747 PIDD patients who underwent HSCT; complications of HSCT significantly decreased over time. Mortality rates significantly decreased in all PIDD patients and in patients receiving HSCT.
The total hospitalizations and incidence of PIDDs within the hospitalized pediatric population were unchanged. There were significant changes in the class of PIDD diagnosed, the age at diagnosis, and health care utilization metrics. Mortality significantly decreased over time within the PIDD cohort.
Human metapneumovirus (HMPV) is a primary cause of acute respiratory infection, yet there are no approved vaccines or antiviral therapies for HMPV. Early host responses to HMPV are poorly ...characterized, and further understanding could identify important antiviral pathways. Type III interferon (IFN-λ) displays potent antiviral activity against respiratory viruses and is being investigated for therapeutic use. However, its role in HMPV infection remains largely unknown. Here, we show that IFN-λ is highly upregulated during HMPV infection
in human and mouse airway epithelial cells and
in mice. We found through several immunological and molecular assays that type II alveolar cells are the primary producers of IFN-λ. Using mouse models, we show that IFN-λ limits lung HMPV replication and restricts virus spread from upper to lower airways but does not contribute to clinical disease. Moreover, we show that IFN-λ signaling is predominantly mediated by CD45
non-immune cells. Mice lacking IFN-λ signaling showed diminished loss of ciliated epithelial cells and decreased recruitment of lung macrophages in early HMPV infection along with higher inflammatory cytokine and interferon-stimulated gene expression, suggesting that IFN-λ may maintain immunomodulatory responses. Administration of IFN-λ for prophylaxis or post-infection treatment in mice reduced viral load without inflammation-driven weight loss or clinical disease. These data offer clinical promise for IFN-λ in HMPV treatment.
Human metapneumovirus (HMPV) is a common respiratory pathogen and often contributes to severe disease, particularly in children, immunocompromised people, and the elderly. There are currently no licensed HMPV antiviral treatments or vaccines. Here, we report novel roles of host factor IFN-λ in HMPV disease that highlight therapeutic potential. We show that IFN-λ promotes lung antiviral responses by restricting lung HMPV replication and spread from upper to lower airways but does so without inducing lung immunopathology. Our data uncover recruitment of lung macrophages, regulation of ciliated epithelial cells, and modulation of inflammatory cytokines and interferon-stimulated genes as likely contributors. Moreover, we found these roles to be distinct and non-redundant, as they are not observed with knockout of, or treatment with, type I IFN. These data elucidate unique antiviral functions of IFN-λ and suggest IFN-λ augmentation as a promising therapeutic for treating HMPV disease and promoting effective vaccine responses.
Inducible bronchus-associated lymphoid tissue (iBALT) is an ectopic lymphoid structure composed of highly organized T cell and B cell zones that forms in the lung in response to infectious or ...inflammatory stimuli. Here, we develop a model for fungal-mediated iBALT formation, using infection with Pneumocystis that induces development of pulmonary lymphoid follicles. Pneumocystis-dependent iBALT structure formation and organization required CXCL13 signaling. Cxcl13 expression was regulated by interleukin (IL)-17 family members, as Il17ra−/−, Il17rb−/−, and Il17rc−/− mice failed to develop iBALT. Interestingly, Il17rb−/− mice have intact Th17 responses, but failed to generate an anti-Pneumocystis Th2 response. Given a role for Th2 and Th17 immunity in iBALT formation, we demonstrated that primary pulmonary fibroblasts synergistically upregulated Cxcl13 transcription following dual stimulation with IL-13 and IL-17A in a STAT3/GATA3-dependent manner. Together, these findings uncover a role for Th2/Th17 cells in regulating Cxcl13 expression and provide an experimental model for fungal-driven iBALT formation.
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•Pneumocystis infection results in development of iBALT in a CXCL13-dependent manner•Pneumocystis-driven iBALT formation requires both Th2 and Th17 immunity•Pulmonary fibroblasts treated with IL-13 and IL-17A synergistically induce Cxcl13•IL-17A/IL-13 stimulation requires STAT3, STAT6, and GATA3 for induction of Cxcl13
Eddens et al. develop a model for fungal-inducible bronchus-associated lymphoid tissue (iBALT) formation driven by infection or exposure to Pneumocystis. Pneumocystis induces Th2 and Th17 immunity, both of which are required for iBALT formation.
Respiratory viruses are a common cause of morbidity and mortality around the world. Viruses like influenza, RSV, and most recently SARS‐CoV‐2 can rapidly spread through a population, causing acute ...infection and, in vulnerable populations, severe or chronic disease. Developing effective treatment and prevention strategies often becomes a race against ever‐evolving viruses that develop resistance, leaving therapy efficacy either short‐lived or relevant for specific viral strains. On June 29 to July 2, 2022, researchers met for the Keystone symposium “Respiratory Viruses: New Frontiers.” Researchers presented new insights into viral biology and virus–host interactions to understand the mechanisms of disease and identify novel treatment and prevention approaches that are effective, durable, and broad.
Respiratory viruses are a common cause of morbidity and mortality around the world. Viruses like influenza, RSV, and most recently SARS‐CoV‐2 can rapidly spread through a population, causing acute infection and, in vulnerable populations, severe or chronic disease. On June 29 to July 2, 2022, researchers met for the Keystone symposium “Respiratory Viruses: New Frontiers”. The meeting was held jointly with the symposium “Viral Immunity: Basic Mechanisms and Therapeutic Applications.” Researchers presented new insights into viral biology and virus‐host interactions to understand the mechanisms of disease and identify novel treatment and prevention approaches that are effective, durable, and broad.
pneumonia is the most common serious opportunistic infection in patients with HIV/AIDS. Furthermore,
pneumonia is a feared complication of the immunosuppressive drug regimens used to treat ...autoimmunity, malignancy, and posttransplantation rejection. With an increasing at-risk population, there is a strong need for novel approaches to discover diagnostic and vaccine targets. There are multiple challenges to finding these targets, however. First,
has a largely unannotated genome. To address this, we evaluated each protein encoded within the
genome by comparisons to proteins encoded within the genomes of other fungi using NCBI BLAST. Second,
relies on a multiphasic life cycle, as both the transmissible form (the ascus) and the replicative form (the trophozoite troph) reside within the alveolar space of the host. To that end, we purified asci and trophs from
and utilized transcriptomics to identify differentially regulated genes. Two such genes,
and
, are differentially regulated in the ascus and the troph, respectively, and can be utilized to characterize the state of the
life cycle
, encoding a β-1,3-glucan synthase with a large extracellular domain previously identified using surface proteomics, was more highly expressed on the ascus form of
GSC-1 ectodomain immunization generated a strong antibody response that demonstrated the ability to recognize the surface of the
asci. GSC-1 ectodomain immunization was also capable of reducing ascus burden following primary challenge with
Finally, mice immunized with the GSC-1 ectodomain had limited fungal burden following natural transmission of
using a cohousing model.
The current report enhances our understanding of
biology in a number of ways. First, the current study provided a preliminary annotation of the
genome, addressing a long-standing issue in the field. Second, this study validated two novel transcripts enriched in the two predominant life forms of
These findings allow better characterization of the
life cycle
and could be valuable diagnostic tools. Furthermore, this study outlined a novel pipeline of -omics techniques capable of revealing novel antigens (e.g., GSC-1) for the development of vaccines against
.
Pneumocystis is an important opportunistic fungus that causes pneumonia in children and immunocompromised individuals. Recent genomic data show that divergence of major surface glycoproteins may ...confer speciation and host range selectivity. On the other hand, immune clearance between mice and humans is well correlated. Thus, we hypothesized that humanize mice may provide information about human immune responses involved in controlling Pneumocystis infection. CD34-engrafted huNOG-EXL mice controlled fungal burdens to a greater extent than nonengrafted mice. Moreover, engrafted mice generated fungal-specific IgM. Fungal control was associated with a transcriptional signature that was enriched for genes associated with nonopsonic recognition of trophs (CD209) and asci (CLEC7A). These same genes were downregulated in CD4-deficient mice as well as twins with bare lymphocyte syndrome with Pneumocystis pneumonia.
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