Advances in the treatment of virus-induced asthma

The Wiser Strategy of Using Beta-Agonists in Asthma: Mechanisms and Rationales

Concerns regarding the safety of beta-2 agonists have led to revisions of the major asthma guidelines to better address these issues. Although these updates allow for a combination of previous and current strategies, they may confuse clinical practitioners. Beta-2 agonists are vital for alleviating asthma symptoms by relaxing smooth muscles; however, they also pose significant risks by inducing pro-inflammatory mediators both in vitro and in vivo. In addition to the risks of overuse and symptom masking, the use of beta-agonists alone at therapeutic doses can worsen airway inflammation and enhance virus-induced inflammation during asthma exacerbation. Inhaled corticosteroids (ICS) can effectively prevent these adverse effects. With new insights into the mechanisms of these adverse events, reserving short-acting beta-agonists for acute symptom relief during exacerbations and only for those who are already on ICS or oral steroids represents a careful approach to using beta-agonists with least adverse effects in patients with asthma. However, a major drawback of this approach is the potential non-compliance with ICS, leading to beta-agonist use without the necessary counteraction by ICS. An optimal strategy, both during and outside exacerbations, would integrate beta-agonists into an anti-inflammatory regimen that includes ICS, ideally combined with the same inhaler to ensure their concurrent use where finances allow. This would maintain the beneficial effects of beta-agonists, such as bronchodilation, while preventing the adverse effects from the induction of inflammatory mediators. This method is aligned with diverse clinical settings, maximizes the safe use of beta-agonists, and supports a comprehensive guideline-compliant management strategy.

Cullin5 drives experimental asthma exacerbations by modulating alveolar macrophage antiviral immunity

Asthma exacerbations caused by respiratory viral infections are a serious global health problem. Impaired antiviral immunity is thought to contribute to the pathogenesis, but the underlying mechanisms remain understudied. Here using mouse models we find that Cullin5 (CUL5), a key component of Cullin-RING E3 ubiquitin ligase 5, is upregulated and associated with increased neutrophil count and influenza-induced exacerbations of house dust mite-induced asthma. By contrast, CUL5 deficiency mitigates neutrophilic lung inflammation and asthma exacerbations by augmenting IFN-β production. Mechanistically, following thymic stromal lymphopoietin stimulation, CUL5 interacts with O-GlcNAc transferase (OGT) and induces Lys48-linked polyubiquitination of OGT, blocking the effect of OGT on mitochondrial antiviral-signaling protein O-GlcNAcylation and RIG-I signaling activation. Our results thus suggest that, in mouse models, pre-existing allergic injury induces CUL5 expression, impairing antiviral immunity and promoting neutrophilic inflammation for asthma exacerbations. Targeting of the CUL5/IFN-β signaling axis may thereby serve as a possible therapy for treating asthma exacerbations.

Epidemiology and Immunopathogenesis of Virus Associated Asthma Exacerbations

Asthma is a common airway disease, affecting millions of people worldwide. Although most asthma patients experience mild symptoms, it is characterized by variable airflow limitation, which can occasionally become life threatening in the case of a severe exacerbation. The commonest triggers of asthma exacerbations in both children and adults are viral infections. In this review article, we will try to investigate the most common viruses triggering asthma exacerbations and their role in asthma immunopathogenesis, since viral infections in young adults are thought to trigger the development of asthma either right away after the infection or at a later stage of their life. The commonest viral pathogens associated with asthma include the respiratory syncytial virus, rhinoviruses, influenza and parainfluenza virus, metapneumovirus and coronaviruses. All these viruses exploit different molecular pathways to infiltrate the host. Asthmatics are more prone to severe viral infections due to their unique inflammatory response, which is mostly characterized by T2 cytokines. Unlike the normal T1 high response to viral infection, asthmatics with T2 high inflammation are less potent in containing a viral infection. Inhaled and/or systematic corticosteroids and bronchodilators remain the cornerstone of asthma exacerbation treatment, and although many targeted therapies which block molecules that viruses use to infect the host have been used in a laboratory level, none has been yet approved for clinical use. Nevertheless, further understanding of the unique pathway that each virus follows to infect an individual may be crucial in the development of targeted therapies for the commonest viral pathogens to effectively prevent asthma exacerbations. Finally, biologic therapies resulted in a complete change of scenery in the treatment of severe asthma, especially with a T2 high phenotype. All available data suggest that monoclonal antibodies are safe and able to drastically reduce the rate of viral asthma exacerbations.

Rhinovirus infection induces secretion of endothelin-1 from airway epithelial cells in both in vitro and in vivo models

BACKGROUND

Rhinovirus (RV) infection of airway epithelial cells triggers asthma exacerbations, during which airway smooth muscle (ASM) excessively contracts. Due to ASM contraction, airway epithelial cells become mechanically compressed. We previously reported that compressed human bronchial epithelial (HBE) cells are a source of endothelin-1 (ET-1) that causes ASM contraction. Here, we hypothesized that epithelial sensing of RV by TLR3 and epithelial compression induce ET-1 secretion through a TGF-β receptor (TGFβR)-dependent mechanism.

METHODS

To test this, we used primary HBE cells well-differentiated in air-liquid interface culture and two mouse models (ovalbumin and house dust mite) of allergic airway disease (AAD). HBE cells were infected with RV-A16, treated with a TLR3 agonist (poly(I:C)), or exposed to compression. Thereafter, EDN1 (ET-1 protein-encoding gene) mRNA expression and secreted ET-1 protein were measured. We examined the role of TGFβR in ET-1 secretion using either a pharmacologic inhibitor of TGFβR or recombinant TGF-β1 protein. In the AAD mouse models, allergen-sensitized and allergen-challenged mice were subsequently infected with RV. We then measured ET-1 in bronchoalveolar lavage fluid (BALF) and airway hyperresponsiveness (AHR) following methacholine challenge.

RESULTS

Our data reveal that RV infection induced EDN1 expression and ET-1 secretion in HBE cells, potentially mediated by TLR3. TGFβR activation was partially required for ET-1 secretion, which was induced by RV, poly(I:C), or compression. TGFβR activation alone was sufficient to increase ET-1 secretion. In AAD mouse models, RV induced ET-1 secretion in BALF, which positively correlated with AHR.

CONCLUSIONS

Our data provide evidence that RV infection increased epithelial-cell ET-1 secretion through a TGFβR-dependent mechanism, which contributes to bronchoconstriction during RV-induced asthma exacerbations.

Impact of Airway Virus in Severe Asthmatic Patients: A Pilot Study

The lungs have their own microbiota which seems to be altered in disease processes such as asthma. Viral infection accounts for many asthma exacerbations. Little is known about the lung virome, and the role that viruses play in non-exacerbating asthmatics. We aimed to assess if detection of virus in bronchoscopy samples of asthmatic patients in a non-exacerbating state influences their asthma control and modulates airway cytokine composition. Patients were recruited from a specialist asthma clinic and underwent bronchoscopy with standardised bronchoalveolar lavage (BAL). Viral analysis was performed; cell differential and cytokine levels were measured. Forty-six samples were obtained of which 10.8% demonstrated evidence of airway virus, and 91.3% of patients in the cohort were classed as severe asthmatics. Oral steroid use was significantly higher in severe asthmatic patients with virus detected, and the forced expiratory volume in one second tended to be lower in the virus-detected group. It was also found that BAL interleukin-13 and tumor necrosis factor-α levels were significantly higher in severe asthmatic patients with virus detected. Our results suggest that in severe asthmatics in a non-exacerbating state, the presence of virus resulted in overall poorer asthma control. The pattern of cytokine elevation seen in asthmatic patients with virus detected may provide insight to the pathophysiology involved.

IL-25 blockade augments antiviral immunity during respiratory virus infection

IL-25 is implicated in the pathogenesis of viral asthma exacerbations. However, the effect of IL-25 on antiviral immunity has yet to be elucidated. We observed abundant expression and colocalization of IL-25 and IL-25 receptor at the apical surface of uninfected airway epithelial cells and rhinovirus infection increased IL-25 expression. Analysis of immune transcriptome of rhinovirus-infected differentiated asthmatic bronchial epithelial cells (BECs) treated with an anti-IL-25 monoclonal antibody (LNR125) revealed a re-calibrated response defined by increased type I/III IFN and reduced expression of type-2 immune genes CCL26, IL1RL1 and IL-25 receptor. LNR125 treatment also increased type I/III IFN expression by coronavirus infected BECs. Exogenous IL-25 treatment increased viral load with suppressed innate immunity. In vivo LNR125 treatment reduced IL-25/type 2 cytokine expression and increased IFN-β expression and reduced lung viral load. We define a new immune-regulatory role for IL-25 that directly inhibits virus induced airway epithelial cell innate anti-viral immunity.

Viral Infection and Respiratory Exacerbation in Children: Results from a Local German Pediatric Exacerbation Cohort

Respiratory viruses play an important role in asthma exacerbation, and early exposure can be involved in recurrent bronchitis and the development of asthma. The exact mechanism is not fully clarified, and pathogen-to-host interaction studies are warranted to identify biomarkers of exacerbation in the early phase. Only a limited number of international exacerbation cohorts were studied. Here, we have established a local pediatric exacerbation study in Germany consisting of children with asthma or chronic, recurrent bronchitis and analyzed the viriome within the nasopharyngeal swab specimens derived from the entire cohort (n = 141). Interestingly, 41% of exacerbated children had a positive test result for human rhinovirus (HRV)/human enterovirus (HEV), and 14% were positive for respiratory syncytial virus (RSV). HRV was particularly prevalent in asthmatics (56%), wheezers (50%), and atopic (66%) patients. Lymphocytes were decreased in asthmatics and in HRV-infected subjects, and patients allergic to house dust mites were more susceptible to HRV infection. Our study thus confirms HRV infection as a strong 'biomarker' of exacerbated asthma. Further longitudinal studies will show the clinical progress of those children with a history of an RSV or HRV infection. Vaccination strategies and novel treatment guidelines against HRV are urgently needed to protect those high-risk children from a serious course of disease.

Innate Immune Evasion by Human Respiratory RNA Viruses

The impact of respiratory virus infections on the health of children and adults can be very significant. Yet, in contrast to most other childhood infections as well as other viral and bacterial diseases, prophylactic vaccines or effective antiviral treatments against viral respiratory infections are either still not available, or provide only limited protection. Given the widespread prevalence, a general lack of natural sterilizing immunity, and/or high morbidity and lethality rates of diseases caused by influenza, respiratory syncytial virus, coronaviruses, and rhinoviruses, this difficult situation is a genuine societal challenge. A thorough understanding of the virus-host interactions during these respiratory infections will most probably be pivotal to ultimately meet these challenges. This review attempts to provide a comparative overview of the knowledge about an important part of the interaction between respiratory viruses and their host: the arms race between host innate immunity and viral innate immune evasion. Many, if not all, viruses, including the respiratory viruses listed above, suppress innate immune responses to gain a window of opportunity for efficient virus replication and setting-up of the infection. The consequences for the host's immune response are that it is often incomplete, delayed or diminished, or displays overly strong induction (after the delay) that may cause tissue damage. The affected innate immune response also impacts subsequent adaptive responses, and therefore viral innate immune evasion often undermines fully protective immunity. In this review, innate immune responses relevant for respiratory viruses with an RNA genome will briefly be summarized, and viral innate immune evasion based on shielding viral RNA species away from cellular innate immune sensors will be discussed from different angles. Subsequently, viral enzymatic activities that suppress innate immune responses will be discussed, including activities causing host shut-off and manipulation of stress granule formation. Furthermore, viral protease-mediated immune evasion and viral manipulation of the ubiquitin system will be addressed. Finally, perspectives for use of the reviewed knowledge for the development of novel antiviral strategies will be sketched.

The manufacturing of human viral challenge agents for use in clinical studies to accelerate the drug development process

OBJECTIVE

This manuscript aims to provide an overview of the unique considerations and best practice principles associated with the manufacture of human viral challenge agents.

RESULTS

Considerations are discussed on the entire process from strain and viral source selection through manufacturing, safety and efficacy testing. The human viral challenge (HVC) model is an important tool to help accelerate the drug development process but producing viruses suitable for use in the model presents a unique set of challenges. There are many case by case decisions and risk assessments to consider and no clear international standard to produce viruses for this purpose. The authors present challenge virus manufacturing considerations from the current literature, regulatory guidance and their own direct experience in producing challenge viruses. The use of these viral stocks in clinical studies, as published in peer-reviewed journals, is also briefly described.

Effects of Fruit and Vegetable Consumption on Risk of Asthma, Wheezing and Immune Responses: A Systematic Review and Meta-Analysis

Evidence suggests that reduced intake of fruit and vegetables may play a critical role in the development of asthma and allergies. The present review aimed to summarize the evidence for the association between fruit and vegetable intake, risk of asthma/wheeze and immune responses. Databases including PubMed, Cochrane, CINAHL and EMBASE were searched up to June 2016. Studies that investigated the effects of fruit and vegetable intake on risk of asthma/wheeze and immune responses were considered eligible (n = 58). Studies used cross-sectional (n = 30), cohort (n = 13), case-control (n = 8) and experimental (n = 7) designs. Most of the studies (n = 30) reported beneficial associations of fruit and vegetable consumption with risk of asthma and/or respiratory function, while eight studies found no significant relationship. Some studies (n = 20) reported mixed results, as they found a negative association between fruit only or vegetable only, and asthma. In addition, the meta-analyses in both adults and children showed inverse associations between fruit intake and risk of prevalent wheeze and asthma severity (p < 0.05). Likewise, vegetable intake was negatively associated with risk of prevalent asthma (p < 0.05). Seven studies examined immune responses in relation to fruit and vegetable intake in asthma, with n = 6 showing a protective effect against either systemic or airway inflammation. Fruit and vegetable consumption appears to be protective against asthma.