Rhinoviruses are the major trigger of acute asthma exacerbations and asthmatic subjects are more susceptible to these infections. To investigate the underlying mechanisms of this increased susceptibility, we examined virus replication and innate responses to rhinovirus (RV)-16 infection of primary bronchial epithelial cells from asthmatic and healthy control subjects. Viral RNA expression and late virus release into supernatant was increased 50- and 7-fold, respectively in asthmatic cells compared with healthy controls. Virus infection induced late cell lysis in asthmatic cells but not in normal cells. Examination of the early cellular response to infection revealed impairment of virus induced caspase 3/7 activity and of apoptotic responses in the asthmatic cultures. Inhibition of apoptosis in normal cultures resulted in enhanced viral yield, comparable to that seen in infected asthmatic cultures. Examination of early innate immune responses revealed profound impairment of virus-induced interferon-β mRNA expression in asthmatic cultures and they produced >2.5 times less interferon-β protein. In infected asthmatic cells, exogenous interferon-β induced apoptosis and reduced virus replication, demonstrating a causal link between deficient interferon-β, impaired apoptosis and increased virus replication. These data suggest a novel use for type I interferons in the treatment or prevention of virus-induced asthma exacerbations.

Rationale: Severe, steroid-resistant asthma is the major unmet need in asthma therapy. Disease heterogeneity and poor understanding of pathogenic mechanisms hampers the identification of therapeutic targets. Excessive nucleotide-binding oligomerization domain–like receptor family, pyrin domain–containing 3 (NLRP3) inflammasome and concomitant IL-1β responses occur in chronic obstructive pulmonary disease, respiratory infections, and neutrophilic asthma. However, the direct contributions to pathogenesis, mechanisms involved, and potential for therapeutic targeting remain poorly understood, and are unknown in severe, steroid-resistant asthma. Objectives: To investigate the roles and therapeutic targeting of the NLRP3 inflammasome and IL-1β in severe, steroid-resistant asthma. Methods: We developed mouse models of Chlamydia and Haemophilus respiratory infection–mediated, ovalbumin-induced severe, steroid-resistant allergic airway disease. These models share the hallmark features of human disease, including elevated airway neutrophils, and NLRP3 inflammasome and IL-1β responses. The roles and potential for targeting of NLRP3 inflammasome, caspase-1, and IL-1β responses in experimental severe, steroid-resistant asthma were examined using a highly selective NLRP3 inhibitor, MCC950; the specific caspase-1 inhibitor Ac-YVAD-cho; and neutralizing anti–IL-1β antibody. Roles for IL-1β–induced neutrophilic inflammation were examined using IL-1β and anti-Ly6G. Measurements and Main Results: Chlamydia and Haemophilus infections increase NLRP3, caspase-1, IL-1β responses that drive steroid-resistant neutrophilic inflammation and airway hyperresponsiveness. Neutrophilic airway inflammation, disease severity, and steroid resistance in human asthma correlate with NLRP3 and IL-1β expression. Treatment with anti–IL-1β, Ac-YVAD-cho, and MCC950 suppressed IL-1β responses and the important steroid-resistant features of disease in mice, whereas IL-1β administration recapitulated these features. Neutrophil depletion suppressed IL-1β–induced steroid-resistant airway hyperresponsiveness. Conclusions: NLRP3 inflammasome responses drive experimental severe, steroid-resistant asthma and are potential therapeutic targets in this disease.

Nontuberculous Mycobacterium infections, particularly Mycobacterium abscessus, are increasingly common among patients with cystic fibrosis and chronic bronchiectatic lung diseases. Treatment is challenging due to intrinsic antibiotic resistance. Bacteriophage therapy represents a potentially novel approach. Relatively few active lytic phages are available and there is great variation in phage susceptibilities among M. abscessus isolates, requiring personalized phage identification. Mycobacterium isolates from 200 culture-positive patients with symptomatic disease were screened for phage susceptibilities. One or more lytic phages were identified for 55 isolates. Phages were administered intravenously, by aerosolization, or both to 20 patients on a compassionate use basis and patients were monitored for adverse reactions, clinical and microbiologic responses, the emergence of phage resistance, and phage neutralization in serum, sputum, or bronchoalveolar lavage fluid. No adverse reactions attributed to therapy were seen in any patient regardless of the pathogen, phages administered, or the route of delivery. Favorable clinical or microbiological responses were observed in 11 patients. Neutralizing antibodies were identified in serum after initiation of phage delivery intravenously in 8 patients, potentially contributing to lack of treatment response in 4 cases, but were not consistently associated with unfavorable responses in others. Eleven patients were treated with only a single phage, and no phage resistance was observed in any of these. Phage treatment of Mycobacterium infections is challenging due to the limited repertoire of therapeutically useful phages, but favorable clinical outcomes in patients lacking any other treatment options support continued development of adjunctive phage therapy for some mycobacterial infections.

Acute exacerbations of asthma are frequently caused by viral infections, but the inflammatory mechanisms in virus-induced asthma are poorly understood. The aim of the present study was to determine whether viral infection in acute asthma was associated with increased sputum neutrophil degranulation and increased cellular lysis and whether these changes are related to clinical severity.Adults (n=49) presenting to the emergency department with acute asthma were examined for infection by means of sputum direct-fluorescence antigen detection, sputum culture, and sputum polymerase chain reaction for Mycoplasma, Chlamydia andLegionella pneumophila, and all common respiratory viruses. Subjects infected with one of these agents were classed as having an infective exacerbation. Spirometry and sputum induction were performed on presentation and 4–5 weeks later.Thirty-seven subjects (76%) had virus infection and acute asthma. Those with virus infection had increased sputum neutrophils (p<0.05) and increased neutrophil elastase (p<0.05), this was related to increased elevated sputum lactate dehydrogenase (LDH). Subjects with noninfective asthma had an increase in the proportion of sputum eosinophils. Both groups had elevated sputum eosinophil cationic protein (ECP) concentrations. Higher levels of sputum LDH and ECP were associated with a longer hospital stay.Virus infection and acute asthma is associated with neutrophilic inflammation, cell lysis and more severe clinical disease.

Patients with asthma–chronic obstructive pulmonary disease overlap syndrome (ACOS) have been largely excluded from pivotal therapeutic trials and, as a result, its treatment remains poorly defined and lacking firm evidence. To date, there is no universally accepted definition of ACOS, which has made it difficult to understand its epidemiology or pathophysiology. Despite many uncertainties, there is emerging agreement that some of the key features of ACOS include persistent airflow limitation in symptomatic individuals 40 years of age and older, a well-documented history of asthma in childhood or early adulthood and a significant exposure history to cigarette or biomass smoke. In this perspective, we propose a case definition of ACOS that incorporates these key features in a parsimonious algorithm that may enable clinicians to better diagnose patients with ACOS and most importantly enable researchers to design therapeutic and clinical studies to elucidate its epidemiology and pathophysiology and to ascertain its optimal management strategies.