Immune mechanisms of respiratory viral infections in asthma

Mutations at the conserved N-Terminal of the human Rhinovirus capsid gene VP4, and their impact on the immune response

Rhinoviruses (RV) are the major cause of chronic obstructive pulmonary disease and are associated with exacerbation development as well as community-acquired pneumonia in children, leading to substantial morbidity, mortality, and hospital admission. Here we have examined how changes at the amino terminal of the conserved VP4 epitope of different RV serotypes may affect pulmonary cytokine and chemokine responses and disease severity. Samples positive for rhinovirus were used for genetic characterization, followed by profiling gene expression of pulmonary Th1 and Th2 cytokines/chemokines by RT-PCR arrays. Genetic sequencing and homology 3D modeling revealed changes at the amino terminal of the conserved viral protein 4 (VP4) epitope in the RV-A101 serotype, especially serine at several positions that are important for interactive binding with the host immune cells. We found dysregulation of pulmonary gene expression of Th1- and Th2-related cytokines and chemokines in RV-A 101 and RV-C 8 pneumonia patients. These findings might contribute to a better understanding of RV immunity and the potential mechanisms underlying the pathogenesis of severe RV infections, but further functional studies are needed to confirm the causal relationship.

Airway epithelial cell response to RSV is mostly impaired in goblet and multiciliated cells in asthma

BACKGROUND

In patients with asthma, respiratory syncytial virus (RSV) infections can cause disease exacerbation by infecting the epithelial layer of the airways, inducing subsequent immune response. The type I interferon antiviral response of epithelial cells upon RSV infection is found to be reduced in asthma in most-but not all-studies. Moreover, the molecular mechanisms causing the differences in the asthmatic bronchial epithelium in response to viral infection are poorly understood.

METHODS

Here, we investigated the transcriptional response to RSV infection of primary bronchial epithelial cells (pBECs) from patients with asthma (n=8) and healthy donors (n=8). The pBECs obtained from bronchial brushes were differentiated in air-liquid interface conditions and infected with RSV. After 3 days, cells were processed for single-cell RNA sequencing.

RESULTS

A strong antiviral response to RSV was observed for all cell types, for all samples (p<1e-48). Most (1045) differentially regulated genes following RSV infection were found in cells transitioning to secretory cells. Goblet cells from patients with asthma showed lower expression of genes involved in the interferon response (false discovery rate <0.05), including OASL, ICAM1 and TNFAIP3. In multiciliated cells, an impairment of the signalling pathways involved in the response to RSV in asthma was observed.

CONCLUSION

Our results highlight that the response to RSV infection of the bronchial epithelium in asthma and healthy airways was largely similar. However, in asthma, the response of goblet and multiciliated cells is impaired, highlighting the need for studying airway epithelial cells at high resolution in the context of asthma exacerbation.

Biologics for asthma and risk of pneumonia

OBJECTIVE

Modification of the immune system with biologics raises theoretical concerns about the risk of infections but it is still unclear whether currently routinely used biologics in severe asthma may facilitate the development of pneumonia. Therefore, we aimed to determine whether omalizumab, mepolizumab, benralizumab, and dupilumab are associated with pneumonia in a real-world setting.

METHODS

A retrospective disproportionality analysis was performed using adverse event (AE) reports submitted to FAERS from January 2020 to September 30, 2023. MedDRA was used to identify infections and infestations and then pneumonia cases. ROR and PRR were used to measure disproportionality.

RESULTS

The percentage of reported cases of pneumonia compared to infections and infestations was highest for mepolizumab (36.8%), followed by omalizumab (32.6%), benralizumab (19.2%) and dupilumab (5.7%). We found a moderate or strong signal for increased risk of pneumonia with mepolizumab (ROR = 3.74, 95%CI 3.50-4.00), omalizumab (ROR = 3.26, 95%CI 3.06-3.49) and benralizumab (ROR = 2.65, 95%CI 2.49-2.83).

CONCLUSIONS

Mepolizumab, omalizumab and benralizumab, but not dupilumab, were associated with high odds of reporting pneumonia. Our results represent only potential associations between these biologics and pneumonia but not causality. The nature of the FAERS database is such that the cause of the reported events is uncertain. Therefore, we can only roughly estimate the incidence of AEs by the signal strength (ROR value). Nevertheless, although causality could not be assessed, the signal from our study is interesting. We believe it deserves to be further substantiated by real-world studies with robust designs.

Interferons as negative regulators of ILC2s in allergic lung inflammation and respiratory viral infections

Group 2 innate lymphoid cells (ILC2s), characterized by a lack of antigen receptors, have been regarded as an important component of type 2 pulmonary immunity. Analogous to Th2 cells, ILC2s are capable of releasing type 2 cytokines and amphiregulin, thus playing an essential role in a variety of diseases, such as allergic diseases and virus-induced respiratory diseases. Interferons (IFNs), an important family of cytokines with potent antiviral effects, can be triggered by microbial products, microbial exposure, and pathogen infections. Interestingly, the past few years have witnessed encouraging progress in revealing the important role of IFNs and IFN-producing cells in modulating ILC2 responses in allergic lung inflammation and respiratory viral infections. This review underscores recent progress in understanding the role of IFNs and IFN-producing cells in shaping ILC2 responses and discusses disease phenotypes, mechanisms, and therapeutic targets in the context of allergic lung inflammation and infections with viruses, including influenza virus, rhinovirus (RV), respiratory syncytial virus (RSV), and severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2).

Ingestion, Immunity, and Infection: Nutrition and Viral Respiratory Tract Infections

Respiratory infections place a heavy burden on the health care system, particularly in the winter months. Individuals with a vulnerable immune system, such as very young children and the elderly, and those with an immune deficiency, are at increased risk of contracting a respiratory infection. Most respiratory infections are relatively mild and affect the upper respiratory tract only, but other infections can be more serious. These can lead to pneumonia and be life-threatening in vulnerable groups. Rather than focus entirely on treating the symptoms of infectious disease, optimizing immune responsiveness to the pathogens causing these infections may help steer towards a more favorable outcome. Nutrition may have a role in such prevention through different immune supporting mechanisms. Nutrition contributes to the normal functioning of the immune system, with various nutrients acting as energy sources and building blocks during the immune response. Many micronutrients (vitamins and minerals) act as regulators of molecular responses of immune cells to infection. It is well described that chronic undernutrition as well as specific micronutrient deficiencies impair many aspects of the immune response and make individuals more susceptible to infectious diseases, especially in the respiratory and gastrointestinal tracts. In addition, other dietary components such as proteins, pre-, pro- and synbiotics, and also animal- and plant-derived bioactive components can further support the immune system. Both the innate and adaptive defense systems contribute to active antiviral respiratory tract immunity. The initial response to viral airway infections is through recognition by the innate immune system of viral components leading to activation of adaptive immune cells in the form of cytotoxic T cells, the production of neutralizing antibodies and the induction of memory T and B cell responses. The aim of this review is to describe the effects of a range different dietary components on anti-infective innate as well as adaptive immune responses and to propose mechanisms by which they may interact with the immune system in the respiratory tract.

The risk of respiratory tract infections and antibiotic use in a general population and among people with asthma

Aim

The aim of this study was to investigate occupational, environmental, early life and other risk factors associated with respiratory infections and antibiotics use in a general population and among asthmatic individuals.

Method

This study included 15 842 participants of the Respiratory Health in Northern Europe (RHINE) study aged 25–54 years from five Nordic countries, who answered a questionnaire covering respiratory outcomes, exposures, demographic characteristics and numbers of infections and courses of antibiotics in the last 12 months. Multiple logistic regression with and without adjustment for age, sex, smoking status, body mass index and centre were used to study the risk of infection and antibiotics in relation to asthma, and also the association between infection and antibiotics and occupations.

Results

In the whole population, 11.6% reported having three or more respiratory infections, and 14.7% had used antibiotics because of respiratory tract infections within the last year. Asthmatic participants reported tripled odds for such infections (adjusted OR 2.98, 95% CI 2.53–3.52) and antibiotics use (adjusted OR 3.67, 95% CI 3.18–4.24) as compared to non-asthmatic participants. Both in the general and the asthmatic population, female sex, obesity and exposure to building dampness were associated with respiratory infections. Female sex and current smoking and living in Tartu were associated with antibiotic use. The use of antibiotics was doubled in people hospitalised for severe respiratory infection in childhood.

Conclusion

In this study we identified several factors associated with increased respiratory infections and use of antibiotics in a general population and among asthmatic individuals. The frequency of respiratory infections and subsequent antibiotic treatment were increased among those with asthma.

The main findings of this study are that asthmatics reported three times higher odds for respiratory tract infections and more than three times higher odds for subsequent antibiotics than subjects without asthmahttps://bit.ly/3hwsH67

Experimental Antiviral Therapeutic Studies for Human Rhinovirus Infections

Rhinovirus infection is common and usually causes mild, self-limiting upper respiratory tract symptoms. Rhinoviruses can cause exacerbation of chronic respiratory diseases, such as asthma or chronic obstructive pulmonary disease, leading to a significant burden of morbidity and mortality. There has been a great deal of progress in efforts to understand the immunological basis of rhinovirus infection. However, despite a number of in vitro and in vivo attempts, there have been no effective treatments developed. This review article summarises the up to date virological and immunological understanding of these infections. We discuss the challenges researchers face, and key solutions, in their work to investigate potential therapies including in vivo rhinovirus challenge studies. Finally, we explore past and present experimental therapeutic strategies employed in the treatment of rhinovirus infections and highlight promising areas of future work.

Mast Cell Proteases Tryptase and Chymase Induce Migratory and Morphological Alterations in Bronchial Epithelial Cells

Chronic respiratory diseases are often characterized by impaired epithelial function and remodeling. Mast cells (MCs) are known to home into the epithelium in respiratory diseases, but the MC-epithelial interactions remain less understood. Therefore, this study aimed to investigate the effect of MC proteases on bronchial epithelial morphology and function. Bronchial epithelial cells were stimulated with MC tryptase and/or chymase. Morphology and epithelial function were performed using cell tracking analysis and holographic live-cell imaging. Samples were also analyzed for motility-associated gene expression. Immunocytochemistry was performed to compare cytoskeletal arrangement. Stimulated cells showed strong alterations on gene, protein and functional levels in several parameters important for maintaining epithelial function. The most significant increases were found in cell motility, cellular speed and cell elongation compared to non-stimulated cells. Also, cell morphology was significantly altered in chymase treated compared to non-stimulated cells. In the current study, we show that MC proteases can induce cell migration and morphological and proliferative alterations in epithelial cells. Thus, our data imply that MC release of proteases may play a critical role in airway epithelial remodeling and disruption of epithelial function.

Single-cell transcriptomic analysis reveals key immune cell phenotypes in the lungs of patients with asthma exacerbation

BACKGROUND

Asthma exacerbations are associated with heightened asthma symptoms, which can result in hospitalization in severe cases. However, the molecular immunologic processes that determine the course of an exacerbation remain poorly understood, impeding the progression of development of effective therapies.

OBJECTIVE

Our aim was to identify candidate genes that are strongly associated with asthma exacerbation at a cellular level.

METHODS

Subjects with asthma exacerbation and healthy control subjects were recruited, and bronchoalveolar lavage fluid was isolated from these subjects via bronchoscopy. Cells were isolated through fluorescence-activated cell sorting, and single-cell RNA sequencing was performed on enriched cell populations.

RESULTS

We showed that the levels of monocytes, CD8+ T cells, and macrophages are significantly elevated in the bronchoalveolar lavage fluid of patients. A set of cytokines and intracellular transduction regulators are associated with asthma exacerbations and are shared across multiple cell clusters, forming a complicated molecular framework. An additional group of core exacerbation-associated modules is activated, including eukaryotic initiation factor 2 signaling, ephrin receptor signaling, and C-X-C chemokine receptor type 4 signaling in the subpopulations of CD8+ T cells (C1-a) and monocyte clusters (C7 clusters), which are associated with infection.

CONCLUSION

Our study identified a significant number of severe asthma-associated genes that are differentially expressed by multiple cell clusters.

Early-life EV-A71 infection augments allergen-induced airway inflammation in asthma through trained macrophage immunity

Virus-induced asthma is prevalent among children, but its underlying mechanisms are unclear. Accumulated evidence indicates that early-life respiratory virus infection increases susceptibility to allergic asthma. Nonetheless, the relationship between systemic virus infections, such as enterovirus infection, and the ensuing effects on allergic asthma development is unknown. Early-life enterovirus infection was correlated with higher risks of allergic diseases in children. Adult mice exhibited exacerbated mite allergen-induced airway inflammation following recovery from EV-A71 infection in the neonatal period. Bone marrow-derived macrophages (BMDMs) from recovered EV-A71-infected mice showed sustained innate immune memory (trained immunity) that could drive naïve T helper cells toward Th2 and Th17 cell differentiation when in contact with mites. Adoptive transfer of EV-A71-trained BMDMs induced augmented allergic inflammation in naïve recipient mice, which was inhibited by 2-deoxy-D-glucose (2-DG) pretreatment, suggesting that trained macrophages following enterovirus infection are crucial in the progression of allergic asthma later in life.

Is asthma a risk factor for COVID-19? Are phenotypes important?

These results reaffirm the idea that asthma does not appear to be a risk factor for the development of #COVID19. However, most of the asthma patients in this study had a non-T2 phenotype. https://bit.ly/38hIp18.

Resolved Influenza A Virus Infection Has Extended Effects on Lung Homeostasis and Attenuates Allergic Airway Inflammation in a Mouse Model

Allergic airway inflammation (AAI) involves T helper cell type 2 (Th2) and pro-inflammatory responses to aeroallergens and many predisposing factors remain elusive. Influenza A virus (IAV) is a major human pathogen that causes acute respiratory infections and induces specific immune responses essential for viral clearance and resolution of the infection. Beyond acute infection, IAV has been shown to persistently affect lung homeostasis and respiratory immunity. Here we asked how resolved IAV infection affects subsequently induced AAI. Mice infected with a sublethal dose of IAV were sensitized and challenged in an ovalbumin mediated mouse model for AAI after resolution of the acute viral infection. Histological changes, respiratory leukocytes, cytokines and airway hyperreactivity were analyzed in resolved IAV infection alone and in AAI with and without previous IAV infection. More than five weeks after infection, we detected persistent pneumonia with increased activated CD4⁺ and CD8⁺ lymphocytes as well as dendritic cells and MHCII expressing macrophages in the lung. Resolved IAV infection significantly affected subsequently induced AAI on different levels including morphological changes, respiratory leukocytes and lymphocytes as well as the pro-inflammatory cytokine responses, which was clearly diminished. We conclude that IAV has exceptional persisting effects on respiratory immunity with substantial consequences for subsequently induced AAI.

Equine Asthma: Current Understanding and Future Directions

The 2019 Havemeyer Workshop brought together researchers and clinicians to discuss the latest information on Equine Asthma and provide future research directions. Current clinical and molecular asthma phenotypes and endotypes in humans were discussed and compared to asthma phenotypes in horses. The role of infectious and non-infectious causes of equine asthma, genetic factors and proposed disease pathophysiology were reviewed. Diagnostic limitations were evident by the limited number of tests and biomarkers available to field practitioners. The participants emphasized the need for more accessible, standardized diagnostics that would help identify specific phenotypes and endotypes in order to create more targeted treatments or management strategies. One important outcome of the workshop was the creation of the Equine Asthma Group that will facilitate communication between veterinary practice and research communities through published and easily accessible guidelines and foster research collaboration.

Immune Modulation in Asthma: Current Concepts and Future Strategies

Asthma treatment concepts have profoundly changed over the last 20 years, from standard therapeutic regimens for all patients with asthma towards individually tailored interventions targeting treatable traits ("precision medicine"). A precise and highly effective immune modulation with minimal adverse effects plays a central role in this new concept. Recently, there have been major advances in the treatment of asthma with immune-modulatory compounds. One example is the approval of several highly potent biologics for the treatment of severe asthma. New immune-modulatory strategies are expected to enter clinical practice in the future; these innovations will be especially important for patients with treatment-resistant asthma.

Inducible epithelial resistance against acute Sendai virus infection prevents chronic asthma-like lung disease in mice

BACKGROUND AND PURPOSE

Respiratory viral infections play central roles in the initiation, exacerbation and progression of asthma in humans. An acute paramyxoviral infection in mice can cause a chronic lung disease that resembles human asthma. We sought to determine whether reduction of Sendai virus lung burden in mice by stimulating innate immunity with aerosolized Toll-like receptor (TLR) agonists could attenuate the severity of chronic asthma-like lung disease.

EXPERIMENTAL APPROACH

Mice were treated by aerosol with 1-μM oligodeoxynucleotide (ODN) M362, an agonist of the TLR9 homodimer, and 4-μM Pam2CSK4 (Pam2), an agonist of the TLR2/6 heterodimer, within a few days before or after Sendai virus challenge.

KEY RESULTS

Treatment with ODN/Pam2 caused ~75% reduction in lung Sendai virus burden 5 days after challenge. The reduction in acute lung virus burden was associated with marked reductions 49 days after viral challenge in eosinophilic and lymphocytic lung inflammation, airway mucous metaplasia, lumenal mucus occlusion and hyperresponsiveness to methacholine. Mechanistically, ODN/Pam2 treatment attenuated the chronic asthma phenotype by suppressing IL-33 production by type 2 pneumocytes, both by reducing the severity of acute infection and by down-regulating Type 2 (allergic) inflammation.

CONCLUSION AND IMPLICATIONS

These data suggest that treatment of susceptible human hosts with aerosolized ODN and Pam2 at the time of a respiratory viral infection might attenuate the severity of the acute infection and reduce initiation, exacerbation and progression of asthma.

Circulating MicroRNAs and T-Cell Cytokine Expression Are Associated With the Characteristics of Asthma Exacerbation

Purpose

Immunological mechanisms underlying asthma exacerbation have not been elucidated. The aim of this study was to assess the associations of various asthma exacerbation traits with selected serum microRNA (miRNA) expression and T-cell subpopulations.

Methods

Twenty-one asthmatics were studied during asthma exacerbation (exacerbation visit [EV] and the follow-up visit [FV] at 6 weeks). At both visits, spirometry was performed, fractional exhaled nitric oxide (FeNO) was measured, and nasopharyngeal and blood samples were collected. In nasopharyngeal samples, respiratory viruses were assayed by multiplex polymerase chain reaction (PCR), and bacterial cultures were performed. Serum miRNAs were assayed with real-time PCR. T-cell surface markers, eosinophil progenitors and intracellular cytokines were assessed by flow cytometry.

Results

Two-thirds of patients had moderate or severe exacerbation and the FV, overall improvement in asthma control was observed. The mean expression of serum miRNA-126a, miRNA-16 and miRNA-21 was significantly lower at the EV than at the FV. At EV, miRNA-29b correlated with FeNO (r = 0.44, P < 0.05), and 5 of 7 miRNA tested correlated with pulmonary function tests. The number of cluster of differentiation (CD)45+CD4+interleukin (IL)4+ cells was significantly higher at the EV than at the FV, and positive correlations of T-regulatory cells and eosinophil progenitors with asthma control was found. At the EV, serum miRNAs negatively correlated with the number of T cells expressing IL-4, IL-17, IL-22 and interferon gamma, while at the FV both positive and negative correlations with T-cell subsets were observed. No association of detected pathogen (viruses and bacteria) in nasopharyngeal fluid with clinical, functional and immunological parameters was found.

Conclusions

Epigenetic dysregulation during asthma exacerbation could be related to respiratory function, airway inflammation and T-cell cytokine expression.

Future Research Directions in Pneumonia. NHLBI Working Group Report

Pneumonia is a complex pulmonary disease in need of new clinical approaches. Although triggered by a pathogen, pneumonia often results from dysregulations of host defense that likely precede infection. The coordinated activities of immune resistance and tissue resilience then dictate whether and how pneumonia progresses or resolves. Inadequate or inappropriate host responses lead to more severe outcomes such as acute respiratory distress syndrome and to organ dysfunction beyond the lungs and over extended time frames after pathogen clearance, some of which increase the risk for subsequent pneumonia. Improved understanding of such host responses will guide the development of novel approaches for preventing and curing pneumonia and for mitigating the subsequent pulmonary and extrapulmonary complications of pneumonia. The NHLBI assembled a working group of extramural investigators to prioritize avenues of host-directed pneumonia research that should yield novel approaches for interrupting the cycle of unhealthy decline caused by pneumonia. This report summarizes the working group's specific recommendations in the areas of pneumonia susceptibility, host response, and consequences. Overarching goals include the development of more host-focused clinical approaches for preventing and treating pneumonia, the generation of predictive tools (for pneumonia occurrence, severity, and outcome), and the elucidation of mechanisms mediating immune resistance and tissue resilience in the lung. Specific areas of research are highlighted as especially promising for making advances against pneumonia.

The airway epithelium in asthma

Asthma is a genetically and phenotypically complex disease that has a major impact on global health. Signs and symptoms of asthma are caused by the obstruction of airflow through the airways. The epithelium that lines the airways plays a major role in maintaining airway patency and in host defense. The epithelium initiates responses to inhaled or aspirated substances, including allergens, viruses, and bacteria, and epithelial-derived cytokines are important in the recruitment and activation of immune cells in the airway. Changes in the structure and function of the airway epithelium are a prominent feature of asthma. Approximately half of individuals with asthma have evidence of active type 2 immune responses in the airway. In these individuals, epithelial cytokines promote type 2 responses, and responses to type 2 cytokines result in increased epithelial mucus production and other effects that cause airway obstruction. Recent work also implicates other epithelial responses, including interleukin-17, interferon and ER stress responses, that may contribute to asthma pathogenesis and provide new targets for therapy.

Transcriptome networks identify mechanisms of viral and nonviral asthma exacerbations in children

Respiratory infections are common precursors to asthma exacerbations in children, but molecular immune responses that determine whether and how an infection causes an exacerbation are poorly understood. By using systems-scale network analysis, we identify repertoires of cellular transcriptional pathways that lead to and underlie distinct patterns of asthma exacerbation. Specifically, in both virus-associated and nonviral exacerbations, we demonstrate a set of core exacerbation modules, among which epithelial-associated SMAD3 signaling is upregulated and lymphocyte response pathways are downregulated early in exacerbation, followed by later upregulation of effector pathways including epidermal growth factor receptor signaling, extracellular matrix production, mucus hypersecretion, and eosinophil activation. We show an additional set of multiple inflammatory cell pathways involved in virus-associated exacerbations, in contrast to squamous cell pathways associated with nonviral exacerbations. Our work introduces an in vivo molecular platform to investigate, in a clinical setting, both the mechanisms of disease pathogenesis and therapeutic targets to modify exacerbations.

Recent advances in understanding rhinovirus immunity

Rhinoviruses are the most common cause of upper respiratory tract infections. However, they can induce exacerbations of chronic obstructive pulmonary disease and asthma, bronchiolitis in infants, and significant lower respiratory tract infections in children, the immunosuppressed, and the elderly. The large number of rhinovirus strains (currently about 160) and their antigenic diversity are significant obstacles in vaccine development. The phenotype of immune responses induced during rhinovirus infection can affect disease severity. Recognition of rhinovirus and a balance of innate responses are important factors in rhinovirus-induced morbidity. Immune responses to rhinovirus infections in healthy individuals are typically of the T helper type 1 (Th1) phenotype. However, rhinovirus-driven asthma exacerbations are additionally characterised by an amplified Th2 immune response and airway neutrophilia. This commentary focuses on recent advances in understanding immunity toward rhinovirus infection and how innate and adaptive immune responses drive rhinovirus-induced asthma exacerbations.

Research highlights from the 2017 ERS International Congress: airway diseases in focus

For another year, high-quality research studies from around the world transformed the annual ERS International Congress into a vivid platform to discuss trending research topics, to produce new research questions and to further push the boundaries of respiratory medicine and science. This article reviews only some of the high-quality research studies on asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis and chronic cough that were presented during the congress through the Airway Diseases Assembly (ERS Assembly 5) and places them into the context of current knowledge and research challenges.

Members of the @ERStalk Airway Diseases Assembly discuss clinical highlights from #ERSCongress 2017http://ow.ly/G51Y30i7fMR