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Coronavirus disease 2019 (COVID-19) is the latest respiratory pandemic caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). Although infection initiates in the proximal airways, severe and sometimes fatal symptoms of the disease are caused by infection of the alveolar type 2 (AT2) cells of the distal lung and associated inflammation. In this study, we develop primary human lung epithelial infection models to understand initial responses of proximal and distal lung epithelium to SARS-CoV-2 infection. Differentiated air-liquid interface (ALI) cultures of proximal airway epithelium and alveosphere cultures of distal lung AT2 cells are readily infected by SARS-CoV-2, leading to an epithelial cell-autonomous proinflammatory response with increased expression of interferon signaling genes. Studies to validate the efficacy of selected candidate COVID-19 drugs confirm that remdesivir strongly suppresses viral infection/replication. We provide a relevant platform for study of COVID-19 pathobiology and for rapid drug screening against SARS-CoV-2 and emergent respiratory pathogens.

Rationale: The role of FSTL-1 (follistatin-like 1) in lung homeostasis is unknown.Objectives: We aimed to define the impact of FSTL-1 attenuation on lung structure and function and to identify FSTL-1-regulated transcriptional pathways in the lung. Further, we aimed to analyze the association of FSTL-1 SNPs with lung disease.Methods: FSTL-1 hypomorphic (FSTL-1 Hypo) mice underwent lung morphometry, pulmonary function testing, and micro-computed tomography. Fstl1 expression was determined in wild-type lung cell populations from three independent research groups. RNA sequencing of wild-type and FSTL-1 Hypo mice identified FSTL-1-regulated gene expression, followed by validation and mechanistic in vitro examination. FSTL1 SNP analysis was performed in the COPDGene (Genetic Epidemiology of Chronic Obstructive Pulmonary Disease) cohort.Measurements and Main Results: FSTL-1 Hypo mice developed spontaneous emphysema, independent of smoke exposure. Fstl1 is highly expressed in the lung by mesenchymal and endothelial cells but not immune cells. RNA sequencing of whole lung identified 33 FSTL-1-regulated genes, including Nr4a1, an orphan nuclear hormone receptor that negatively regulates NF-κB (nuclear factor-κB) signaling. In vitro, recombinant FSTL-1 treatment of macrophages attenuated NF-κB p65 phosphorylation in an Nr4a1-dependent manner. Within the COPDGene cohort, several SNPs in the FSTL1 region corresponded to chronic obstructive pulmonary disease and lung function.Conclusions: This work identifies a novel role for FSTL-1 protecting against emphysema development independent of smoke exposure. This FSTL-1-deficient emphysema implicates regulation of immune tolerance in lung macrophages through Nr4a1. Further study of the mechanisms involving FSTL-1 in lung homeostasis, immune regulation, and NF-κB signaling may provide additional insight into the pathophysiology of emphysema and inflammatory lung diseases.

Despite the discovery of key pattern recognition receptors and CD4+ T cell subsets in laboratory mice, there is ongoing discussion of the value of murine models to reflect human disease. Pneumocystis is an AIDS-defining illness, in which risk of infection is inversely correlated with peripheral CD4+ T cell counts. Due to medical advances in the control of HIV, the current epidemiology of Pneumocystis infection is predominantly due to primary human immunodeficiencies and immunosuppressive therapies. To this end, we found that every human genetic immunodeficiency associated with Pneumocystis infection that has been tested in mice recapitulated susceptibility. For example, humans with a loss-of-function IL21R mutation are severely immunocompromised. We found that IL-21R, in addition to CD4+ T cell intrinsic STAT3 signaling, were required for generating protective antifungal class-switched antibody responses, as well as effector T cell-mediated protection. Furthermore, CD4+ T cell intrinsic IL-21R/STAT3 signaling was required for CD4+ T cell effector responses, including IL-22 production. Recombinant IL-22 administration to Il21r-/- mice induced the expression of a fungicidal peptide, cathelicidin antimicrobial peptide, which showed in vitro fungicidal activity. In conclusion, SPF laboratory mice faithfully replicate many aspects of human primary immunodeficiency and provide useful tools to understand the generation and nature of effector CD4+ T cell immunity.

The article highlights ongoing challenges in managing cystic fibrosis (CF) in patients despite advancements in modulator therapies. Topics include the persistence of chronic bacterial infections within the lungs and airways that remain a hallmark of CF, the limitations of current therapies in fully controlling infection and inflammation, and the need for further research to enhance treatment efficacy for patients who do not respond optimally to modulators.

Lung tumor-promoting environmental exposures and γherpesvirus infections are associated with Type 17 inflammation. To test the effect of γherpesvirus infection in promoting lung tumorigenesis, we infected mutant K-Ras-expressing (K-RasLA1) mice with the murine γherpesvirus MHV68 via oropharyngeal aspiration. After 7 weeks, the infected mice displayed a more than 2-fold increase in lung tumors relative to their K-RasLA1 uninfected littermates. Assessment of cytokines in the lung revealed that expression of Type 17 cytokines (Il-6, Cxcl1, Csf3) peaked at day 7 post-infection. These observations correlated with the post-infection appearance of known immune mediators of tumor promotion via IL-17A in the lungs of tumor-bearing mice. Surprisingly, Cd84, an immune cell marker mRNA, did not increase in MHV68-infected wild-type mice lacking lung tumors. Csf3 and Cxcl1 protein levels increased more in the lungs of infected K-RasLA1 mice relative to infected wild-type littermates. Flow cytometric and transcriptomic analyses indicated that the infected K-RasLA1 mice had increased Ly6Gdim/Ly6Chi immune cells in the lung relative to levels seen in uninfected control K-RasLA1 mice. Selective methylation of adenosines (m6A modification) in immune-cell-enriched mRNAs appeared to correlate with inflammatory infiltrates in the lung. These observations implicate γherpesvirus infection in lung tumor promotion and selective accumulation of immune cells in the lung that appears to be associated with m6A modification of mRNAs in those cells. [ABSTRACT FROM AUTHOR]

Recurrent Pseudomonas aeruginosa infections coupled with robust, damaging neutrophilic inflammation characterize the chronic lung disease cystic fibrosis (CF). The proresolving lipid mediator, 15-epi lipoxin A4 (15-epi LXA4), plays a critical role in limiting neutrophil activation and tissue inflammation, thus promoting the return to tissue homeostasis. Here, we show that a secreted P. aeruginosa epoxide hydrolase, cystic fibrosis transmembrane conductance regulator inhibitory factor (Cif), can disrupt 15-epi LXA4 transcellular biosynthesis and function. In the airway, 15-epi LXA4 production is stimulated by the epithelial-derived eicosanoid 14,15-epoxyeicosatrienoic acid (14,15-EET). Cif sabotages the production of 15-epi LXA4 by rapidly hydrolyzing 14,15-EET into its cognate diol, eliminating a proresolving signal that potently suppresses IL-8-driven neutrophil transepithelial migration in vitro. Retrospective analyses of samples from patients with CF supported the translational relevance of these preclinical findings. Elevated levels of Cif in bronchoalveolar lavage fluid were correlated with lower levels of 15-epi LXA4, increased IL-8 concentrations, and impaired lung function. Together, these findings provide structural, biochemical, and immunological evidence that the bacterial epoxide hydrolase Cif disrupts resolution pathways during bacterial lung infections. The data also suggest that Cif contributes to sustained pulmonary inflammation and associated loss of lung function in patients with CF.

Signaling through the IL-17 receptor (IL-17R) is required to prevent oropharyngeal candidiasis (OPC) in mice and humans. However, the IL-17-responsive cell type(s) that mediate protection are unknown. Using radiation chimeras, we were able to rule out a requirement for IL-17RA in the hematopoietic compartment. We saw remarkable concordance of IL-17-controlled gene expression in C. albicans-infected human oral epithelial cells (OECs) and in tongue tissue from mice with OPC. To interrogate the role of the IL-17R in OECs, we generated mice with conditional deletion of IL-17RA in superficial oral and esophageal epithelial cells (Il17raΔK13). Following oral Candida infection, Il17raΔK13 mice exhibited fungal loads and weight loss indistinguishable from Il17ra-/- mice. Susceptibility in Il17raΔK13 mice correlated with expression of the antimicrobial peptide β-defensin 3 (BD3, Defb3). Consistently, Defb3-/- mice were susceptible to OPC. Thus, OECs dominantly control IL-17R-dependent responses to OPC through regulation of BD3 expression.

Commensal microbiota are critical for the development of local immune responses. In this article, we show that gut microbiota can regulate CD4 T cell polarization during pulmonary fungal infections. Vancomycin drinking water significantly decreased lung Th17 cell numbers during acute infection, demonstrating that Gram-positive commensals contribute to systemic inflammation. We next tested a role for RegIIIγ, an IL-22-inducible antimicrobial protein with specificity for Gram-positive bacteria. Following infection, increased accumulation of Th17 cells in the lungs of RegIIIγ(-/-) and Il22(-/-) mice was associated with intestinal segmented filamentous bacteria (SFB) colonization. Although gastrointestinal delivery of rRegIIIγ decreased lung inflammatory gene expression and protected Il22(-/-) mice from weight loss during infection, it had no direct effect on SFB colonization, fungal clearance, or lung Th17 immunity. We further show that vancomycin only decreased lung IL-17 production in mice colonized with SFB. To determine the link between gut microbiota and lung immunity, serum-transfer experiments revealed that IL-1R ligands increase the accumulation of lung Th17 cells. These data suggest that intestinal microbiota, including SFB, can regulate pulmonary adaptive immune responses.

Asthma is a common chronic disease without cure. Our understanding of asthma onset, pathobiology, classification, and management has evolved substantially over the past decade; however, significant asthma-related morbidity and excess healthcare use and costs persist. To address this important clinical condition, the NHLBI convened a group of extramural investigators for an Asthma Research Strategic Planning workshop on September 18-19, 2014, to accelerate discoveries and their translation to patients. The workshop focused on (1) in utero and early-life origins of asthma, (2) the use of phenotypes and endotypes to classify disease, (3) defining disease modification, (4) disease management, and (5) implementation research. This report summarizes the workshop and produces recommendations to guide future research in asthma.

Giardia lamblia is a leading protozoan cause of diarrheal disease worldwide. It colonizes the lumen and epithelial surface of the small intestine, but does not invade the mucosa. Acute infection causes only minimal mucosal inflammation. Effective immune defenses exist, yet their identity and mechanisms remain incompletely understood. Interleukin (IL)-17A has emerged as an important cytokine involved in inflammation and antimicrobial defense against bacterial pathogens at mucosal surfaces. In this study, we demonstrate that IL-17A has a crucial function in host defense against Giardia infection. Using murine infection models with G. muris and G. lamblia, we observed marked and selective induction of intestinal IL-17A with peak expression after 2 weeks. Th17 cells in the lamina propria and innate immune cells in the epithelial compartment of the small intestine were responsible for the IL-17A response. Experiments in gene-targeted mice revealed that the cytokine, and its cognate receptor IL-17RA, were required for eradication of the parasite. The actions of the cytokine were mediated by hematopoietic cells, and were required for the transport of IgA into the intestinal lumen, since IL-17A deficiency led to marked reduction of fecal IgA levels, as well as for increased intestinal expression of several other potential effectors, including β-defensin 1 and resistin-like molecule β. In contrast, intestinal hypermotility, another major antigiardial defense mechanism, was not impacted by IL-17A loss. Taken together, these findings demonstrate that IL-17A and IL-17 receptor signaling are essential for intestinal defense against the important lumen-dwelling intestinal parasite Giardia.

RationaleStress is associated with asthma morbidity in Puerto Ricans (PRs), who have reduced bronchodilator response (BDR).ObjectivesTo examine whether stress and/or a gene regulating anxiety (ADCYAP1R1) is associated with BDR in PR and non-PR children with asthma.MethodsThis was a cross-sectional study of stress and BDR (percent change in FEV1 after BD) in 234 PRs ages 9-14 years with asthma. We assessed child stress using the Checklist of Children's Distress Symptoms, and maternal stress using the Perceived Stress Scale. Replication analyses were conducted in two cohorts. Polymorphisms in ADCYAP1R1 were genotyped in our study and six replication studies. Multivariable models of stress and BDR were adjusted for age, sex, income, environmental tobacco smoke, and use of inhaled corticosteroids.Measurements and main resultsHigh child stress was associated with reduced BDR in three cohorts. PR children who were highly stressed (upper quartile, Checklist of Children's Distress Symptoms) and whose mothers had high stress (upper quartile, Perceived Stress Scale) had a BDR that was 10.2% (95% confidence interval, 6.1-14.2%) lower than children who had neither high stress nor a highly stressed mother. A polymorphism in ADCYAP1R1 (rs34548976) was associated with reduced BDR. This single-nucleotide polymorphism is associated with reduced expression of the gene for the β2-adrenergic receptor (ADRB2) in CD4(+) lymphocytes of subjects with asthma, and it affects brain connectivity of the amygdala and the insula (a biomarker of anxiety).ConclusionsHigh child stress and an ADCYAP1R1 single-nucleotide polymorphism are associated with reduced BDR in children with asthma. This is likely caused by down-regulation of ADRB2 in highly stressed children.