Moraxella catarrhalis in chronic obstructive pulmonary disease: burden of disease and immune response

High frequencies of nonviral colds and respiratory bacteria colonization among children in rural Western Uganda

Introduction

Respiratory illness is the most common childhood disease globally, especially in developing countries. Previous studies have detected viruses in approximately 70-80% of respiratory illnesses.

Methods

In a prospective cohort study of 234 young children (ages 3-11 years) and 30 adults (ages 22-51 years) in rural Western Uganda sampled monthly from May 2019 to August 2021, only 24.2% of nasopharyngeal swabs collected during symptomatic disease had viruses detectable by multiplex PCR diagnostics and metagenomic sequencing. In the remaining 75.8% of swabs from symptomatic participants, we measured detection rates of respiratory bacteria Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae by quantitative PCR.

Results

100% of children tested positive for at least one bacterial species. Detection rates were 87.2%, 96.8%, and 77.6% in children and 10.0%, 36.7%, and 13.3% for adults for H. influenzae, M. catarrhalis, and S. pneumoniae, respectively. In children, 20.8% and 70.4% were coinfected with two and three pathogens, respectively, and in adults 6.7% were coinfected with three pathogens but none were coinfected with two. Detection of any of the three pathogens was not associated with season or respiratory symptoms severity, although parsing detection status by symptoms was challenged by children experiencing symptoms in 80.3% of monthly samplings, whereas adults only reported symptoms 26.6% of the time. Pathobiont colonization in children in Western Uganda was significantly more frequent than in children living in high-income countries, including in a study of age-matched US children that utilized identical diagnostic methods. Detection rates were, however, comparable to rates in children living in other Sub-Saharan African countries.

Discussion

Overall, our results demonstrate that nonviral colds contribute significantly to respiratory disease burden among children in rural Uganda and that high rates of respiratory pathobiont colonization may play a role. These conclusions have implications for respiratory health interventions in the area, such as increasing childhood immunization rates and decreasing air pollutant exposure.

Association between Moraxella keratitis and advanced glycation end products

Diabetes mellitus is recognized as a major predisposing factor for Moraxella keratitis. However, how diabetes mellitus contributes to Moraxella keratitis remains unclear. In this study, we examined Moraxella keratitis; based on the findings, we investigated the impact of advanced glycation end products (AGEs) deposition in the cornea of individuals with diabetic mellitus on the adhesion of Moraxella isolates to the cornea. A retrospective analysis of 27 culture-proven cases of Moraxella keratitis at Ehime University Hospital (March 2006 to February 2022) was performed. Moraxella isolates were identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Among the patients, 30.4% had diabetes mellitus and 22.2% had the predominant ocular condition of using steroid eye drops. The species identified were Moraxella nonliquefaciens in 59.3% and Moraxella lacunata in 40.7% of patients. To investigate the underlying mechanisms, we assessed the effects of M. nonliquefaciens adherence to simian virus 40-immortalized human corneal epithelial cells (HCECs) with or without AGEs. The results demonstrated the number of M. nonliquefaciens adhering to HCECs was significantly increased by adding AGEs compared with that in controls (p < 0.01). Furthermore, in the corneas of streptozotocin-induced diabetic C57BL/6 mice treated with or without pyridoxamine, an AGE inhibitor, the number of M. nonliquefaciens adhering to the corneas of diabetic mice was significantly reduced by pyridoxamine treatment (p < 0.05). In conclusion, the development of Moraxella keratitis may be significantly influenced by the deposition of AGEs on the corneal epithelium of patients with diabetes mellitus.

Bacterial Vaccinations in Patients with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a frequent, often progressive, chronic disease of the lungs. Patients with COPD often have impaired immunity; therefore, they are prone to chest infections, such as pneumonia or bronchitis. Acute exacerbations of COPD are major events that accelerate disease progression, contributing to its symptoms' burden, morbidity, and mortality. Both pneumonia and acute exacerbations in COPD are caused by bacteria against which there are effective vaccinations. Although the number of randomised controlled studies on bacterial vaccinations in COPD is limited, national and international guidelines endorse specific vaccinations in patients with COPD. This review will summarise the different types of vaccinations that prevent pneumonia and COPD exacerbations. We also discuss the results of early phase studies. We will mainly focus on Streptococcus pneumoniae, as this bacterium was predominantly investigated in COPD. However, we also review studies investigating vaccinations against Haemophilus influenzae, Moraxella catarrhalis, and Bordetella pertussis.

Inhibiting F-Actin Polymerization Impairs the Internalization of Moraxella catarrhalis

Moraxella catarrhalis, a commensal in the human nasopharynx, plays a significant role in the acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Its pathogenicity involves adherence to respiratory epithelial cells, leading to infection through a macropinocytosis-like mechanism. Previous investigations highlighted the diverse abilities of M. catarrhalis isolates with different phenotypes to adhere to and invade respiratory epithelial cells. This study used a murine COPD model and in vitro experiments to explore the factors influencing the pathogenicity of distinct phenotypes of M. catarrhalis. Transcriptome sequencing suggested a potential association between actin cytoskeleton regulation and the infection of lung epithelial cells by M. catarrhalis with different phenotypes. Electron microscopy and Western blot analyses revealed a decrease in filamentous actin (F-actin) expression upon infection with various M. catarrhalis phenotypes. Inhibition of actin polymerization indicated the involvement of F-actin dynamics in M. catarrhalis internalization, distinguishing it from the adhesion process. Notably, hindering F-actin polymerization impaired the internalization of M. catarrhalis. These findings contribute vital theoretical insights for developing preventive strategies and individualized clinical treatments for AECOPD patients infected with M. catarrhalis. The study underscores the importance of understanding the nuanced interactions between M. catarrhalis phenotypes and host lung epithelial cells, offering valuable implications for the management of AECOPD infections.

Inhaled corticosteroids and risk of lower respiratory tract infection with Moraxella catarrhalis in patients with chronic obstructive pulmonary disease

BACKGROUND

Use of inhaled corticosteroids (ICS) is common in patients with chronic obstructive pulmonary disease (COPD) and has been associated with an increased risk of pneumonia. Moraxella catarrhalis is one of the most common bacterial causes of infectious exacerbation in COPD. Currently, to our knowledge, no studies have investigated if ICS increases the risk of lower respiratory tract infection with M. catarrhalis in patients with COPD.

OBJECTIVE

To investigate if accumulated ICS use in patients with COPD, is associated with a dose-dependent risk of infection with M. catarrhalis.

METHODS

This observational cohort study included 18 870 persons with COPD who were registered in The Danish Register of COPD. Linkage to several nationwide registries was performed.Exposure to ICS was determined by identifying all prescriptions for ICS, redeemed within 365 days prior to study entry. Main outcome was a lower respiratory tract sample positive for M. catarrhalis. For the main analysis, a Cox multivariate regression model was used.We defined clinical infection as admission to hospital and/or a redeemed prescription for a relevant antibiotic, within 7 days prior to 14 days after the sample was obtained.

RESULTS

We found an increased, dose-dependent, risk of a lower respiratory tract sample with M. catarrhalis among patients who used ICS, compared with non-users. For low and moderate doses of ICS HR was 1.65 (95% CI 1.19 to 2.30, p=0.003) and 1.82 (95% CI 1.32 to 2.51, p=0.0002), respectively. In the group of patients with highest ICS exposure, the HR of M. catarrhalis was 2.80 (95% CI 2.06 to 3.82, p<0.0001). Results remained stable in sensitivity analyses. 87% of patients fulfilled the criteria for clinical infection, and results remained unchanged in this population.

CONCLUSION

Our study shows a dose-dependent increased risk of infection with M. catarrhalis associated to ICS exposure.

Seasonal Dynamics of the Upper Respiratory Tract Microbiome in Chronic Obstructive Pulmonary Disease

Introduction

Increasing evidence suggests that seasonal changes can trigger the alternation of airway microbiome. However, the dynamics of the upper airway bacterial ecology of chronic obstructive pulmonary disease (COPD) patients across different seasons remains unclear.

Methods

In this study, we present a 16S ribosomal RNA survey of the airway microbiome on 72 swab samples collected in different months (March, May, July, September, and November) in 2019 from 18 COPD patients and from six resampled patients in November in 2020.

Results

Our study uncovered a dynamic airway microbiota where changes appeared to be associated with seasonal alternation in COPD patients. Twelve clusters of temporal patterns were displayed by differential and clustering analysis along the time course, systematically revealing distinct microbial taxa that prefer to grow in cool and warm seasons, respectively. Moreover, the upper airway microbiome composition was relatively stable in the same season in different years.

Discussion

Given the tight association between airway microbiome and COPD disease progression, this study can provide useful information for clinically understanding the seasonal trend of disease phenotypes in COPD patients.

The Airway Microbiome-IL-17 Axis: a Critical Regulator of Chronic Inflammatory Disease

The respiratory tract is home to a diverse microbial community whose influence on local and systemic immune responses is only beginning to be appreciated. Increasing reports have linked changes in this microbiome to a range of pulmonary and extrapulmonary disorders, including asthma, chronic obstructive pulmonary disease and rheumatoid arthritis. Central to many of these findings is the role of IL-17-type immunity as an important driver of inflammation. Despite the crucial role played by IL-17-mediated immune responses in protection against infection, overt Th17 cell responses have been implicated in the pathogenesis of several chronic inflammatory diseases. However, our knowledge of the influence of bacteria that commonly colonise the respiratory tract on IL-17-driven inflammatory responses remains sparse. In this article, we review the current knowledge on the role of specific members of the airway microbiota in the modulation of IL-17-type immunity and discuss how this line of research may support the testing of susceptible individuals and targeting of inflammation at its earliest stages in the hope of preventing the development of chronic disease.

Immunity against Moraxella catarrhalis requires guanylate-binding proteins and caspase-11-NLRP3 inflammasomes

Moraxella catarrhalis is an important human respiratory pathogen and a major causative agent of otitis media and chronic obstructive pulmonary disease. Toll-like receptors contribute to, but cannot fully account for, the complexity of the immune response seen in M. catarrhalis infection. Using primary mouse bone marrow-derived macrophages to examine the host response to M. catarrhalis infection, our global transcriptomic and targeted cytokine analyses revealed activation of immune signalling pathways by both membrane-bound and cytosolic pattern-recognition receptors. We show that M. catarrhalis and its outer membrane vesicles or lipooligosaccharide (LOS) can activate the cytosolic innate immune sensor caspase-4/11, gasdermin-D-dependent pyroptosis, and the NLRP3 inflammasome in human and mouse macrophages. This pathway is initiated by type I interferon signalling and guanylate-binding proteins (GBPs). We also show that inflammasomes and GBPs, particularly GBP2, are required for the host defence against M. catarrhalis in mice. Overall, our results reveal an essential role for the interferon-inflammasome axis in cytosolic recognition and immunity against M. catarrhalis, providing new molecular targets that may be used to mitigate pathological inflammation triggered by this pathogen.

Estimating the contribution of respiratory pathogens to acute exacerbations of COPD using routine data

OBJECTIVES

To characterise microbiology testing and results associated with emergency admissions for acute exacerbation of COPD (AECOPD), and determine the accuracy of ICD-10 codes in retrospectively identifying laboratory-confirmed respiratory pathogens in this setting.

METHODS

Using person-level data from the Secure Anonymised Information Linkage Databank in Wales, we extracted emergency admissions for COPD from 1/12/2016 to 30/11/2018 and undertook linkage of admissions data to microbiology data to identify laboratory-confirmed infection. We further used these data to assess the accuracy of pathogen-specific ICD-10 codes.

RESULTS

We analysed data from 15,950 people who had 25,715 emergency admissions for COPD over the two-year period. 99.5% of admissions could be linked to a laboratory test within 7 days of admission date. Sputum was collected in 5,013 (19.5%) of admissions, and respiratory virus testing in 1,219 (4.7%). Where respiratory virus testing was undertaken, 46.7% returned any positive result. Influenza was the virus most frequently detected, in 21.5% of admissions where testing was conducted. ICD-10 codes exhibited low sensitivity in detecting laboratory-confirmed respiratory pathogens.

CONCLUSIONS

In people admitted to hospital with AECOPD, increased testing for respiratory viruses could enable more effective antibiotic stewardship and isolation of cases. Linkage with microbiology data achieves more accurate and reliable case definitions.

Metabolomics of Respiratory Diseases

Metabolomics is an expanding field of systems biology that is gaining significant attention in respiratory research. As a unique approach to understanding and diagnosing diseases, metabolomics provides a snapshot of all metabolites present in biological samples such as exhaled breath condensate, bronchoalveolar lavage, plasma, serum, urine, and other specimens that may be obtained from patients with respiratory diseases. In this article, we review the rapidly expanding field of metabolomics in its application to respiratory diseases, including asthma, chronic obstructive pulmonary disease (COPD), pneumonia, and acute lung injury, along with its more severe form, adult respiratory disease syndrome. We also discuss the potential applications of metabolomics for monitoring exposure to aerosolized occupational and environmental materials. With the latest advances in our understanding of the microbiome, we discuss microbiome-derived metabolites that arise from the gut and lung in asthma and COPD that have mechanistic implications for these diseases. Recent literature has suggested that metabolomics analysis using nuclear magnetic resonance (NMR) and mass spectrometry (MS) approaches may provide clinicians with the opportunity to identify new biomarkers that may predict progression to more severe diseases which may be fatal for many patients each year.

FHUSPA2/10 is a bactericidal monoclonal antibody targeting multiple repeated sequences of Moraxella catarrhalis UspA2

Moraxella catarrhalis is an important and common respiratory pathogen that can cause Otitis Media, Community Acquired Pneumonia, and has been associated with an increased risk of exacerbations in chronic obstructive pulmonary disease in adults, leading to morbidity and mortality. Its ubiquitous surface protein A2 (UspA2) has been shown to interact with host structures and extracellular matrix proteins, suggesting a role at an early stage of infection and a contribution to bacterial serum resistance. The UspA proteins are homo-trimeric autotransporters that appear as a lollipop-shaped structure in electron micrographs. They are composed of an N-terminal head with adhesive properties, followed by a stalk, which ends by an amphipathic helix and a C-terminal membrane domain. The three family members UspA1, UspA2 and UspA2H, present different amino acid signatures both at the head and membrane-spanning regions. By combining electron microscopy, hydrogen deuterium exchange mass spectrometry and protein modeling, we identified a shared and repeated epitope recognized by FHUSPA2/10, a potent cross-bactericidal monoclonal antibody raised by UspA2 and deduced key amino acids involved in the binding. The finding strengthens the potential of UspA2 to be incorporated in a vaccine formulation against M. catarrhalis.

Respiratory Viral and Bacterial Exacerbations of COPD—The Role of the Airway Epithelium

COPD is a leading cause of death worldwide, with acute exacerbations being a major contributor to disease morbidity and mortality. Indeed, exacerbations are associated with loss of lung function, and exacerbation frequency predicts poor prognosis. Respiratory infections are important triggers of acute exacerbations of COPD. This review examines the role of bacterial and viral infections, along with co-infections, in the pathogenesis of COPD exacerbations. Because the airway epithelium is the initial site of exposure both to cigarette smoke (or other pollutants) and to inhaled pathogens, we will focus on the role of airway epithelial cell responses in regulating the pathophysiology of exacerbations of COPD. This will include an examination of the interactions of cigarette smoke alone, and in combination with viral and bacterial exposures in modulating epithelial function and inflammatory and host defense pathways in the airways during COPD. Finally, we will briefly examine current and potential medication approaches to treat acute exacerbations of COPD triggered by respiratory infections.

Infective Endocarditis by Moraxella Species: A Systematic Review

Moraxella catarrhalis is the most clinically relevant species among Moraxella spp. For decades, it was considered to be part of the normal human flora in the upper respiratory tract. However, since the late 1970s, considerable evidence has proposed that M. catarrhalis is an important pathogen in the human respiratory tract. Even though Infective Endocarditis (IE) is rarely caused by Moraxella spp., these infections can be problematic due to the lack of experience in their management. The aim of this study was to systematically review all published cases of IE by Moraxella spp. A systematic review of PubMed, Scopus and Cochrane library (through 8 December 2021) for studies providing epidemiological, clinical, microbiological data as well as treatment data and outcomes of IE by Moraxella spp. was performed. A total of 27 studies, containing data for 31 patients, were included. A prosthetic valve was present in 25.8%. Mitral valve was the most commonly infected site. Fever, sepsis and embolic phenomena were the most common clinical presentations. Cephalosporins, aminoglycosides, aminopenicillins and penicillin were the most commonly used antimicrobials. Overall mortality was 12.9%.

Predictors of the Development of Protracted Bacterial Bronchitis following Presentation to Healthcare for an Acute Respiratory Illness with Cough: Analysis of Three Cohort Studies

We describe the prevalence and risk factors for protracted bacterial bronchitis (PBB) following healthcare presentation for an acute cough illness in children. Data from three studies of the development of chronic cough (CC) in children were combined. PBB was defined as a wet cough of at least 4-weeks duration with no identified specific cause of cough that resolved following 2–4 weeks of appropriate antibiotics. Anterior nasal swabs were tested for 17 viruses and bacteria by polymerase chain reaction. The study included 903 children. Childcare attendance (adjusted relative risk (aRR) = 2.32, 95% CI 1.48–3.63), prior history of chronic cough (aRR = 2.63, 95% CI 1.72–4.01) and age <2-years (<12-months: aRR = 4.31, 95% CI 1.42–13.10; 12-<24 months: aRR = 2.00, 95% CI 1.35–2.96) increased risk of PBB. Baseline diagnoses of asthma/reactive airways disease (aRR = 0.30, 95% CI 0.26–0.35) or bronchiolitis (aRR = 0.15, 95% CI 0.06–0.38) decreased risk. M. catarrhalis was the most common organism (52.4%) identified in all children (PBB = 72.1%; no PBB = 50.2%, p < 0.001). We provide the first data on risks for PBB in children following acute illness and a hypothesis for studies to further investigate the relationship with wheeze-related illnesses. Clinicians and parents/guardians should be aware of these risks and seek early review if a wet cough lasting more than 4-weeks develops the post-acute illness.

UspA2 is a cross-protective Moraxella catarrhalis vaccine antigen

Moraxella catarrhalis (Mcat) is a key pathogen associated with exacerbations of chronic obstructive pulmonary disease (COPD) in adults and playing a significant role in otitis media in children. A vaccine would help to reduce the morbidity and mortality associated with these diseases. UspA2 is an Mcat surface antigen considered earlier as vaccine candidate before the interest in this molecule vanished due to sequence variability. However, the observation that some conserved domains are the target of bactericidal antibodies prompted us to reconsider UspA2 as a potential vaccine antigen. We first determined its prevalence among the COPD patients from the AERIS study, as the prevalence of UspA2 in a COPD-restricted population had yet to be documented. The gene was found in all Mcat isolates either as UspA2 or UspA2H variant. The percentage of UspA2H variant was higher than in any report so far, reaching 51%. A potential link between the role of UspA2H in biofilm formation and this high prevalence is discussed. To study further UspA2 as a vaccine antigen, recombinant UspA2 molecules were designed and used in animal models and bactericidal assays. We showed that UspA2 is immunogenic and that UspA2 immunization clears Mcat pulmonary challenge in a mouse model. In a serum bactericidal assay, anti-UspA2 antibodies generated in mice, guinea pigs or rabbits were able to kill Mcat strains of various origins, including a subset of isolates from the AERIS study, cross-reacting with UspA2H and even UspA1, a closely related Mcat surface protein. In conclusion, UspA2 is a cross-reactive Mcat antigen presenting the characteristics of a vaccine candidate.

The Role of Non-Typeable Haemophilus influenzae Biofilms in Chronic Obstructive Pulmonary Disease

Non-typeable Haemophilus influenzae (NTHi) is an ubiquitous commensal-turned-pathogen that colonises the respiratory mucosa in airways diseases including Chronic Obstructive Pulmonary Disease (COPD). COPD is a progressive inflammatory syndrome of the lungs, encompassing chronic bronchitis that is characterised by mucus hypersecretion and impaired mucociliary clearance and creates a static, protective, humid, and nutrient-rich environment, with dysregulated mucosal immunity; a favourable environment for NTHi colonisation. Several recent large COPD cohort studies have reported NTHi as a significant and recurrent aetiological pathogen in acute exacerbations of COPD. NTHi proliferation has been associated with increased hospitalisation, disease severity, morbidity and significant lung microbiome shifts. However, some cohorts with patients at different severities of COPD do not report that NTHi is a significant aetiological pathogen in their COPD patients, indicating other obligate pathogens including Moraxella catarrhalis, Streptococcus pneumoniae and Pseudomonas aeruginosa as the cause. NTHi is an ubiquitous organism across healthy non-smokers, healthy smokers and COPD patients from childhood to adulthood, but it currently remains unclear why NTHi becomes pathogenic in only some cohorts of COPD patients, and what behaviours, interactions and adaptations are driving this susceptibility. There is emerging evidence that biofilm-phase NTHi may play a significant role in COPD. NTHi displays many hallmarks of the biofilm lifestyle and expresses key biofilm formation-promoting genes. These include the autoinducer-mediated quorum sensing system, epithelial- and mucus-binding adhesins and expression of a protective, self-produced polymeric substance matrix. These NTHi biofilms exhibit extreme tolerance to antimicrobial treatments and the immune system as well as expressing synergistic interspecific interactions with other lung pathogens including S. pneumoniae and M. catarrhalis. Whilst the majority of our understanding surrounding NTHi as a biofilm arises from otitis media or in-vitro bacterial monoculture models, the role of NTHi biofilms in the COPD lung is now being studied. This review explores the evidence for the existence of NTHi biofilms and their impact in the COPD lung. Understanding the nature of chronic and recurrent NTHi infections in acute exacerbations of COPD could have important implications for clinical treatment and identification of novel bactericidal targets.

Progressive deterioration of the upper respiratory tract and the gut microbiomes in children during the early infection stages of COVID-19

Children are less susceptible to coronavirus disease 2019 (COVID-19), and they have manifested lower morbidity and mortality after infection, for which a multitude of mechanisms may be considered. Whether the normal development of the gut-airway microbiome in children is affected by COVID-19 has not been evaluated. Here, we demonstrate that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection alters the upper respiratory tract and the gut microbiomes in nine children. The alteration of the microbiome is dominated by the genus Pseudomonas, and it sustains for up to 25–58 days in different individuals. Moreover, the patterns of alternation are different between the upper respiratory tract and the gut. Longitudinal investigation shows that the upper respiratory tract and the gut microbiomes are extremely variable among children during the course of COVID-19. The dysbiosis of microbiome persists in 7 of 8 children for at least 19–24 days after discharge from the hospital. Disturbed development of both the gut and the upper respiratory microbiomes and prolonged dysbiosis in these nine children imply possible long-term complications after clinical recovery from COVID-19, such as predisposition to the increased health risk in the post-COVID-19 era.

Isoxanthanol alleviates Staphylococcus aureus induced chronic obstructive pulmonary disease in rat model through promotion of miR-145-5p expression

The present study was aimed to evaluate the isoxanthanol against Staphylococcus aureus chronic obstructive pulmonary disease (COPD) in rat model. The isoxanthanol decreased the parasitic load by almost 99% in the Staphylococcus aureus infected rats. It significantly (P < 0.05) decreased mortality rate of the rats, prevented pulmonary tissue damage and aggregation of inflammatory cytokines. In Staphylococcus aureus infected rats, isoxanthanol treatment inhibited production of interleukin-18, interleukin-1β and TNF-α significantly (P < 0.05) in the BALF and pulmonary tissues. Treatment of the Staphylococcus aureus-infected rats with isoxanthanol inhibited up-regulation of NLRP3, ASC and caspase-1 expression. In Staphylococcus aureus-infected rats the expression of miR-145-5p was remarkably increased on treatment with isoxanthanol. In summary, isoxanthanol prevents Staphylococcus aureus-induced COPD in rats through up-regulation of miR-145-5p and suppression of inflammatory cytokines. Therefore, isoxanthanol can be of therapeutic importance for the treatment of Staphylococcus aureus induced COPD.

Investigation and Functional Enrichment Analysis of the Human Host Interaction Network with Common Gram-Negative Respiratory Pathogens Predicts Possible Association with Lung Adenocarcinoma

Haemophilus influenzae (Hi), Moraxella catarrhalis (MorCa) and Pseudomonas aeruginosa (Psa) are three of the most common gram-negative bacteria responsible for human respiratory diseases. In this study, we aimed to identify, using the functional enrichment analysis (FEA), the human gene interaction network with the aforementioned bacteria in order to elucidate the full spectrum of induced pathogenicity. The Human Pathogen Interaction Database (HPIDB 3.0) was used to identify the human proteins that interact with the three pathogens. FEA was performed via the ToppFun tool of the ToppGene Suite and the GeneCodis database so as to identify enriched gene ontologies (GO) of biological processes (BP), cellular components (CC) and diseases. In total, 11 human proteins were found to interact with the bacterial pathogens. FEA of BP GOs revealed associations with mitochondrial membrane permeability relative to apoptotic pathways. FEA of CC GOs revealed associations with focal adhesion, cell junctions and exosomes. The most significantly enriched annotations in diseases and pathways were lung adenocarcinoma and cell cycle, respectively. Our results suggest that the Hi, MorCa and Psa pathogens could be related to the pathogenesis and/or progression of lung adenocarcinoma via the targeting of the epithelial cellular junctions and the subsequent deregulation of the cell adhesion and apoptotic pathways. These hypotheses should be experimentally validated.

Clinical characteristics of community-acquired pneumonia due to Moraxella catarrhalis in adults: a retrospective single-centre study

Background

Although Moraxella catarrhalis (M. catarrhalis) is a common cause of community-acquired pneumonia (CAP), studies investigating clinical manifestations of CAP due to M. catarrhalis (MC-CAP) in adults are limited. Since S. pneumoniae is the leading cause of CAP globally, it is important to distinguish between MC-CAP and CAP due to S. pneumoniae (SP-CAP) in clinical practice. However, no past study compared clinical characteristics of MC-CAP and SP-CAP by statistical analysis. We aimed to clarify the clinical characteristics of MC-CAP by comparing those of SP-CAP, as well as the utility of sputum Gram staining.

Methods

This retrospective study screened CAP patients aged over 20 years visiting or admitted to Okinawa Miyako Hospital between May 2013 and April 2018. Among these, we included patients whom either M. catarrhalis alone or S. pneumoniae alone was isolated from their sputum by bacterial cultures.

Results

We identified 134 MC-CAP and 130 SP-CAP patients. Although seasonality was not observed in SP-CAP, almost half of MC-CAP patients were admitted in the winter. Compared to those with SP-CAP, MC-CAP patients were older (p < 0.01) and more likely to have underlying pulmonary diseases such as asthma and bronchiectasis (p < 0.01). Approximately half of asthmatic MC-CAP and SP-CAP patients had asthma attacks. Although winter is an influenza season in Japan, co-infection with influenza virus was less common in MC-CAP compared to SP-CAP patients (3% vs. 15%, p < 0.01). Bronchopneumonia patterns on X-ray, as well as bronchial wall thickening, bilateral distribution, and segmental pattern on CT were more common in MC-CAP patients than in SP-CAP patients (p < 0.01). Sputum Gram stain was highly useful method for the diagnosis in both MC-CAP and SP-CAP (78.4% vs. 89.2%), and penicillins were most frequently chosen as an initial treatment for both pneumonias.

Conclusions

This is the first study to show that MC-CAP occurred in older people compared to SP-CAP, influenza virus co-infection was less common in MC-CAP than SP-CAP, and that MC-CAP frequently caused asthma attacks. Gram stain contributed for the appropriate treatment, resulting in conserving broad-spectrum antibiotics such as cephalosporins and fluoroquinolones in both MC-CAP and SP-CAP patients.

Role of pulmonary microorganisms in the development of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a chronic obstructive respiratory disease characterized by irreversible airway limitation and persistent respiratory symptoms. The main clinical symptoms of COPD are dyspnoea, chronic cough, and sputum. COPD is often accompanied by other respiratory diseases, which can cause worsening of the disease. COPD patients with dyspnoea and aggravation of cough and sputum symptoms represent acute exacerbations of COPD (AECOPD). There is mounting evidence suggesting that dysbiosis of pulmonary microbiota participates in the disease. However, investigations of dysbiosis of pulmonary microbiota and the disease are still in initial phases. To screen, diagnose, and treat this respiratory disease, integrating data from different studies can improve our understanding of the occurrence and development of COPD and AECOPD. In this review, COPD epidemiology and the primary triggering mechanism are explored. Emerging knowledge regarding the association of inflammation, caused by pulmonary microbiome imbalance, and changes in lung microbiome flora species involved in the development of the disease are also highlighted. These data will further our understanding of the pathogenesis of COPD and AECOPD and may yield novel strategies for the use of pulmonary microbiota as a potential therapeutic intervention.

Role of Lung Microbiome in Innate Immune Response Associated With Chronic Lung Diseases

Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), lung fibrosis, and lung cancer, pose a huge socio-economic burden on society and are one of the leading causes of death worldwide. In the past, culture-dependent techniques could not detect bacteria in the lungs, therefore the lungs were considered a sterile environment. However, the development of culture-independent techniques, particularly 16S rRNA sequencing, allowed for the detection of commensal microbes in the lung and with further investigation, their roles in disease have since emerged. In healthy individuals, the predominant commensal microbes are of phylum Firmicutes and Bacteroidetes, including those of the genera Veillonella and Prevotella. In contrast, pathogenic microbes (Haemophilus, Streptococcus, Klebsiella, Pseudomonas) are often associated with lung diseases. There is growing evidence that microbial metabolites, structural components, and toxins from pathogenic and opportunistic bacteria have the capacity to stimulate both innate and adaptive immune responses, and therefore can contribute to the pathogenesis of lung diseases. Here we review the multiple mechanisms that are altered by pathogenic microbiomes in asthma, COPD, lung cancer, and lung fibrosis. Furthermore, we focus on the recent exciting advancements in therapies that can be used to restore altered microbiomes in the lungs.

Antibacterial Fusion Proteins Enhance Moraxella catarrhalis Killing

Moraxella catarrhalis is a human-specific commensal of the respiratory tract and an opportunistic pathogen. It is one of the leading cause of otitis media in children and of acute exacerbations in patients with chronic obstructive pulmonary disease, resulting in significant morbidity and economic burden. Vaccines and new immunotherapeutic strategies to treat this emerging pathogen are needed. Complement is a key component of innate immunity that mediates the detection, response, and subsequent elimination of invading pathogens. Many pathogens including M. catarrhalis have evolved complement evasion mechanisms, which include the binding of human complement inhibitors such as C4b-binding protein (C4BP) and Factor H (FH). Inhibiting C4BP and FH acquisition by M. catarrhalis may provide a novel therapeutic avenue to treat infections. To achieve this, we created two chimeric proteins that combined the Moraxella-binding domains of C4BP and FH fused to human immunoglobulin Fcs: C4BP domains 1 and 2 and FH domains 6 and 7 fused to IgM and IgG Fc, respectively. As expected, FH6-7/IgG displaced FH from the bacterial surface while simultaneously activating complement via Fc-C1q interactions, together increasing pathogen elimination. C4BP1-2/IgM also increased serum killing of the bacteria through enhanced complement deposition, but did not displace C4BP from the surface of M. catarrhalis. These Fc fusion proteins could act as anti-infective immunotherapies. Many microbes bind the complement inhibitors C4BP and FH through the same domains as M. catarrhalis, therefore these Fc fusion proteins may be promising candidates as adjunctive therapy against many different drug-resistant pathogens.

Moraxella catarrhalis phase-variable loci show differences in expression during conditions relevant to disease

Moraxella catarrhalis is a human-adapted, opportunistic bacterial pathogen of the respiratory mucosa. Although asymptomatic colonization of the nasopharynx is common, M. catarrhalis can ascend into the middle ear, where it is a prevalent causative agent of otitis media in children, or enter the lower respiratory tract, where it is associated with acute exacerbations of chronic obstructive pulmonary disease in adults. Phase variation is the high frequency, random, reversible switching of gene expression that allows bacteria to adapt to different host microenvironments and evade host defences, and is most commonly mediated by simple DNA sequence repeats. Bioinformatic analysis of five closed M. catarrhalis genomes identified 17 unique simple DNA sequence repeat tracts that were variable between strains, indicating the potential to mediate phase variable expression of the associated genes. Assays designed to assess simple sequence repeat variation under conditions mimicking host infection demonstrated that phase variation of uspA1 (ubiquitous surface protein A1) from high to low expression occurs over 72 hours of biofilm passage, while phase variation of uspA2 (ubiquitous surface protein A2) to high expression variants occurs during repeated exposure to human serum, as measured by mRNA levels. We also identify and confirm the variable expression of two novel phase variable genes encoding a Type III DNA methyltransferase (modO), and a conserved hypothetical permease (MC25239_RS00020). These data reveal the repertoire of phase variable genes mediated by simple sequence repeats in M. catarrhalis and demonstrate that modulation of expression under conditions mimicking human infection is attributed to changes in simple sequence repeat length.

Synchrony in serum antibody response to conserved proteins of Moraxella catarrhalis in young children

Conserved Moraxella catarrhalis (Mcat) proteins, oligopeptide permease (Opp)A, hemagglutinin (Hag), outer membrane protein (OMP) CD, Pilin A clade 2 (PilA2), and Moraxella surface protein (Msp) 22 have been studied as vaccine candidates. Children who experience frequent acute otitis media (AOM) confirmed with pathogen identification by tympanocentesis are referred to as stringently-defined otitis prone (sOP). Synchrony of serum antibody responses against 5 Mcat proteins, OppA, Hag, OMP CD, PilA2, and Msp22 resulting from nasopharyngeal colonization and AOM was studied for 85 non-otitis prone (NOP) children and 34 sOP children. Changes in serum IgG were quantitated with ELISA. Serum IgG antibody levels against OppA, Hag, OMP CD, and Msp22 rose in synchrony in NOP and sOP children; that is, the proteins appeared equally and highly immunogenic in children at age 6 to 22-25 months old and then leveled off in their rise at 22-25 to 30 months old. In contrast, rises of PilA2 were slow from 6 months old and kept constant and did not level off significantly before 30 months old. OppA, Hag, OMP CD, and Msp22 elicited a synchronous acquisition of naturally-induced serum antibody in young children. A multi-valent Mcat protein vaccine combining OppA, Hag, OMP CD, and Msp22 may exhibit less antigen competition when administered as a combination vaccine in young children.

Microbial burden and viral exacerbations in a longitudinal multicenter COPD cohort

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease characterized by frequent exacerbation phenotypes independent of disease stage. Increasing evidence shows that the microbiota plays a role in disease progression and severity, but long-term and international multicenter assessment of the variations in viral and bacterial communities as drivers of exacerbations are lacking.

METHODS

Two-hundred severe COPD patients from Europe and North America were followed longitudinally for 3 years. We performed nucleic acid detection for 20 respiratory viruses and 16S ribosomal RNA gene sequencing to evaluate the bacterial microbiota in 1179 sputum samples collected at stable, acute exacerbation and follow-up visits.

RESULTS

Similar viral and bacterial taxa were found in patients from the USA compared to Bulgaria and Czech Republic but their microbiome diversity was significantly different (P < 0.001) and did not impact exacerbation rates. Virus infection was strongly associated with exacerbation events (P < 5E-20). Human rhinovirus (13.1%), coronavirus (5.1%) and influenza virus (3.6%) constitute the top viral pathogens in triggering exacerbation. Moraxella and Haemophilus were 5-fold and 1.6-fold more likely to be the dominating microbiota during an exacerbation event. Presence of Proteobacteria such as Pseudomonas or Staphylococcus amongst others, were associated with exacerbation events (OR > 0.17; P < 0.02) but more strongly associated with exacerbation frequency (OR > 0.39; P < 4E-10), as confirmed by longitudinal variations and biotyping of the bacterial microbiota, and suggesting a role of the microbiota in sensitizing the lung.

CONCLUSIONS

This study highlights bacterial taxa in lung sensitization and viral triggers in COPD exacerbations. It provides a global overview of the diverse targets for drug development and explores new microbiome analysis methods to guide future patient management applications.

Procalcitonin and antibiotics in moderate-severe acute exacerbation of chronic obstructive pulmonary disease: to use or not to use

PURPOSE OF REVIEW

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. Acute exacerbations of COPD (AECOPD) are major driver for healthcare utilization with each exacerbation begetting the next exacerbation. It is, therefore, important to treat each episode effectively to prevent the next. However, this can be challenging as AECOPD result from complex interactions between host, environment and infective agents. The benefits of starting antibiotics in AECOPD, which are not life-threatening (e.g. not requiring mechanical ventilation) or not complicated by pneumonia remain controversial.

RECENT FINDINGS

The use of procalcitonin to guide antibiotic therapy in AECOPD has gained interest in recent years. The main advantage of this approach is a safe reduction in antibiotic use in a large group of patients, which may potentially translate to several other benefits. These include reduced antibiotic-related side-effects, reduced risk of developing antibiotic-resistant organisms and cost savings. This approach is associated with no increase in mortality or morbidity such as treatment failure, re-admission, admission to ICU.

SUMMARY

Procalcitonin-guided antibiotic therapy in AECOPD is a promising and safe approach, which may be ready for the prime time.

Persistence of Moraxella catarrhalis in Chronic Obstructive Pulmonary Disease and Regulation of the Hag/MID Adhesin

BACKGROUND

Persistence of bacterial pathogens in the airways has profound consequences on the course and pathogenesis of chronic obstructive pulmonary disease (COPD). Patients with COPD continuously acquire and clear strains of Moraxella catarrhalis, a major pathogen in COPD. Some strains are cleared quickly and some persist for months to years. The mechanism of the variability in duration of persistence is unknown.

METHODS

Guided by genome sequences of selected strains, we studied the expression of Hag/MID, hag/mid gene sequences, adherence to human cells, and autoaggregation in longitudinally collected strains of M. catarrhalis from adults with COPD.

RESULTS

Twenty-eight of 30 cleared strains of M. catarrhalis expressed Hag/MID whereas 17 of 30 persistent strains expressed Hag/MID upon acquisition by patients. All persistent strains ceased expression of Hag/MID during persistence. Expression of Hag/MID in human airways was regulated by slipped-strand mispairing. Virulence-associated phenotypes (adherence to human respiratory epithelial cells and autoaggregation) paralleled Hag/MID expression in airway isolates.

CONCLUSIONS

Most strains of M. catarrhalis express Hag/MID upon acquisition by adults with COPD and all persistent strains shut off expression during persistence. These observations suggest that Hag/MID is important for initial colonization by M. catarrhalis and that cessation of expression facilitates persistence in COPD airways.

ReVac: a reverse vaccinology computational pipeline for prioritization of prokaryotic protein vaccine candidates

Background

Reverse vaccinology accelerates the discovery of potential vaccine candidates (PVCs) prior to experimental validation. Current programs typically use one bacterial proteome to identify PVCs through a filtering architecture using feature prediction programs or a machine learning approach. Filtering approaches may eliminate potential antigens based on limitations in the accuracy of prediction tools used. Machine learning approaches are heavily dependent on the selection of training datasets with experimentally validated antigens (positive control) and non-protective-antigens (negative control). The use of one or few bacterial proteomes does not assess PVC conservation among strains, an important feature of vaccine antigens.

Results

We present ReVac, which implements both a panoply of feature prediction programs without filtering out proteins, and scoring of candidates based on predictions made on curated positive and negative control PVCs datasets. ReVac surveys several genomes assessing protein conservation, as well as DNA and protein repeats, which may result in variable expression of PVCs. ReVac’s orthologous clustering of conserved genes, identifies core and dispensable genome components. This is useful for determining the degree of conservation of PVCs among the population of isolates for a given pathogen. Potential vaccine candidates are then prioritized based on conservation and overall feature-based scoring. We present the application of ReVac, applied to 69 Moraxella catarrhalis and 270 non-typeable Haemophilus influenzae genomes, prioritizing 64 and 29 proteins as PVCs, respectively.

Conclusion

ReVac’s use of a scoring scheme ranks PVCs for subsequent experimental testing. It employs a redundancy-based approach in its predictions of features using several prediction tools. The protein’s features are collated, and each protein is ranked based on the scoring scheme. Multi-genome analyses performed in ReVac allow for a comprehensive overview of PVCs from a pan-genome perspective, as an essential pre-requisite for any bacterial subunit vaccine design. ReVac prioritized PVCs of two human respiratory pathogens, identifying both novel and previously validated PVCs.

The Moraxella catarrhalis phase-variable DNA methyltransferase ModM3 is an epigenetic regulator that affects bacterial survival in an in vivo model of otitis media

Background

Moraxella catarrhalis is a leading cause of otitis media (OM) and chronic obstructive pulmonary disease (COPD). M. catarrhalis contains a Type III DNA adenine methyltransferase (ModM) that is phase-variably expressed (i.e., its expression is subject to random, reversible ON/OFF switching). ModM has six target recognition domain alleles (modM1–6), and we have previously shown that modM2 is the predominant allele, while modM3 is associated with OM. Phase-variable DNA methyltransferases mediate epigenetic regulation and modulate pathogenesis in several bacteria. ModM2 of M. catarrhalis regulates the expression of a phasevarion containing genes important for colonization and infection. Here we describe the phase-variable expression of modM3, the ModM3 methylation site and the suite of genes regulated within the ModM3 phasevarion.

Results

Phase-variable expression of modM3, mediated by variation in length of a 5′-(CAAC)_n-3′ tetranucleotide repeat tract in the open reading frame was demonstrated in M. catarrhalis strain CCRI-195ME with GeneScan fragment length analysis and western immunoblot. We determined that ModM3 is an active N6-adenine methyltransferase that methylates the sequence 5′-AC^m6ATC-3′. Methylation was detected at all 4446 5′-ACATC-3′ sites in the genome when ModM3 is expressed. RNASeq analysis identified 31 genes that are differentially expressed between modM3 ON and OFF variants, including five genes that are involved in the response to oxidative and nitrosative stress, with potential roles in biofilm formation and survival in anaerobic environments. An in vivo chinchilla (Chinchilla lanigera) model of otitis media demonstrated that transbullar challenge with the modM3 OFF variant resulted in an increased middle ear bacterial load compared to a modM3 ON variant. In addition, co-infection experiments with NTHi and M. catarrhalis modM3 ON or modM3 OFF variants revealed that phase variation of modM3 altered survival of NTHi in the middle ear during early and late stage infection.

Conclusions

Phase variation of ModM3 epigenetically regulates the expression of a phasevarion containing multiple genes that are potentially important in the progression of otitis media.

Bacterial load and defective monocyte-derived macrophage bacterial phagocytosis in biomass smoke-related COPD

Lower airway colonisation with species of potentially pathogenic bacteria (PPB) is associated with defective bacterial phagocytosis, in monocyte-derived macrophages (MDMs) and alveolar macrophages, from tobacco smoke-associated chronic obstructive pulmonary disease (S-COPD) subjects. In the developing world, COPD among nonsmokers is largely due to biomass smoke (BMS) exposure; however, little is known about PPB colonisation and its association with impaired innate immunity in these subjects.

We investigated the PPB load (Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Pseudomonas aeruginosa) in BMS-exposed COPD (BMS-COPD) subjects compared with S-COPD and spirometrically normal subjects. We also examined the association between PPB load and phagocytic activity of MDMs and lung function. Induced sputum and peripheral venous blood samples were collected from 18 healthy nonsmokers, 15 smokers without COPD, 16 BMS-exposed healthy subjects, 19 S-COPD subjects and 23 BMS-COPD subjects. PPB load in induced sputum and MDM phagocytic activity were determined using quantitative PCR and fluorimetry, respectively.

Higher bacterial loads of S. pneumoniae, H. influenzae and P. aeruginosa were observed in BMS-COPD subjects. Increased PPB load in BMS-exposed subjects was significantly negatively associated with defective phagocytosis in MDMs and spirometric lung function indices (p<0.05).

Increased PPB load in airways of BMS-COPD subjects is inversely associated with defective bacterial phagocytosis and lung function.

Antibodies against the Majority Subunit (PilA) of the Type IV Pilus of Nontypeable Haemophilus influenzae Disperse Moraxella catarrhalis from a Dual-Species Biofilm

Middle ear infections (or otitis media [OM]) are highly prevalent among children worldwide and present a tremendous socioeconomic challenge for health care systems. More importantly, this disease diminishes the quality of life of young children. OM is often chronic and recurrent, due to the presence of highly antibiotic-resistant communities of bacteria (called biofilms) that persist within the middle ear space. To combat these recalcitrant infections, new and powerful biofilm-directed approaches are needed. Here, we describe the ability to disrupt a biofilm formed by the two most common bacteria that cause chronic and recurrent OM in children, via an approach that combines the power of vaccines with that of traditional antibiotics. An outcome of this strategy is that antibiotics can more easily kill the bacteria that our vaccine-induced antibodies have released from the biofilm. We believe that this approach holds great promise for both the prevention and treatment of OM.

Otitis media (OM) is often polymicrobial, with nontypeable Haemophilus influenzae (NTHI) and Moraxella catarrhalis (Mcat) frequently cocultured from clinical specimens. Bacterial biofilms in the middle ear contribute to the chronicity and recurrence of OM; therefore, strategies to disrupt biofilms are needed. We have focused our vaccine development efforts on the majority subunit of NTHI type IV pili, PilA. Antibodies against a recombinant, soluble form of PilA (rsPilA) both disrupt and prevent the formation of NTHI biofilms in vitro. Moreover, immunization with rsPilA prevents and resolves NTHI-induced experimental OM. Here, we show that antibodies against rsPilA also prevent and disrupt polymicrobial biofilms. Dual-species biofilms formed by NTHI and Mcat at temperatures that mimic the human nasopharynx (34°C) or middle ear (37°C) were exposed to antiserum against either rsPilA or the OMP P5 adhesin of NTHI. NTHI+Mcat biofilm formation was significantly inhibited by antiserum directed against both adhesin proteins at either temperature. However, only anti-rsPilA disrupted NTHI+Mcat preestablished biofilms at either temperature and actively dispersed both NTHI and Mcat via interspecies quorum signaling. Newly released NTHI and Mcat were significantly more susceptible to killing by antibiotics. Taken together, these results revealed new opportunities for treatment of biofilm-associated diseases via a strategy that combines vaccine-induced antibody-mediated biofilm dispersal with traditional antibiotics, at a significantly reduced dosage to exploit the newly released, antibiotic-sensitive phenotype. Combined, our data strongly support the utility of rsPilA both as a preventative and as a therapeutic vaccine antigen for polymicrobial OM due to NTHI and Mcat.

Sputum Moraxella catarrhalis strains exhibit diversity within and between COPD subjects

Purpose

Moraxella catarrhalis is implicated in the pathogenesis of some COPD exacerbations. We sought to investigate whether the M. catarrhalis strain is variable between COPD subjects; that an exacerbation is associated with acquisition of a new strain and that certain strains are more commonly associated with exacerbations.

Patients and methods

Sputum samples were collected at stable and exacerbation visits from COPD subjects from a single center as part of the COPDMAP consortium. Samples identified as M. catarrhalis positive by qPCR were recultured in liquid cultures grown to extract genomic DNA; underwent Illumina MiSeq and bacterial genome sequences were de novo assembled and Multi Locus Sequence Type (MLST) was determined.

Results

Thirty-five samples were obtained from 18 subjects. These included 13 stable and 22 exacerbation samples. The diversity between samples was very large with 25 different M. catarrhalis MLSTs being identified out of the 35 samples of which 12 MSLTs have not been described previously. Change and persistence of M. catarrhalis strain were observed between stable visits, from stable to exacerbation and vice-a-versa, and between exacerbation visits.

Conclusion

Sputum M. catarrhalis strains exhibit marked diversity within and between COPD subjects. Acquisition of a new strain is common between stable and exacerbation events such that no strain is specifically associated with an exacerbation.

Moraxella catarrhalis Restriction-Modification Systems Are Associated with Phylogenetic Lineage and Disease

Moraxella catarrhalis is a human-adapted pathogen, and a major cause of otitis media (OM) and exacerbations of chronic obstructive pulmonary disease. The species is comprised of two main phylogenetic lineages, RB1 and RB2/3. Restriction–modification (R-M) systems are among the few lineage-associated genes identified in other bacterial genera and have multiple functions including defense against foreign invading DNA, maintenance of speciation, and epigenetic regulation of gene expression. Here, we define the repertoire of R-M systems in 51 publicly available M. catarrhalis genomes and report their distribution among M. catarrhalis phylogenetic lineages. An association with phylogenetic lineage (RB1 or RB2/3) was observed for six R-M systems, which may contribute to the evolution of the lineages by restricting DNA transformation. In addition, we observed a relationship between a mutually exclusive Type I R-M system and a Type III R-M system at a single locus conserved throughout a geographically and clinically diverse set of M. catarrhalis isolates. The Type III R-M system at this locus contains the phase-variable Type III DNA methyltransferase, modM, which controls a phasevarion (phase-variable regulon). We observed an association between modM presence and OM-associated middle ear isolates, indicating a potential role for ModM-mediated epigenetic regulation in OM pathobiology.

Mapping Protective Regions on a Three-Dimensional Model of the Moraxella catarrhalis Vaccine Antigen Oligopeptide Permease A

A vaccine against Moraxella catarrhalis would reduce tremendous morbidity, mortality, and financial burden by preventing otitis media in children and exacerbations of chronic obstructive pulmonary disease (COPD) in adults. Oligopeptide permease A (OppA) is a candidate vaccine antigen that is (i) a nutritional virulence factor expressed on the bacterial cell surface during infection, (ii) widely conserved among strains, (iii) highly immunogenic, and (iv) a protective antigen based on its capacity to induce protective responses in immunized animals. In the present study, we show that the antibodies to OppA following vaccination mediate accelerated clearance in animals after pulmonary challenge. To identify regions of OppA that bind protective antibodies, truncated constructs of OppA were engineered and studied to map regions of OppA with surface-accessible epitopes that bind high-avidity antibodies following vaccination. Protective epitopes were located in the N and C termini of the protein. Immunization of mice with constructs corresponding to these regions (T5 and T8) induced protective responses. Studies of overlapping peptide libraries of constructs T5 and T8 with OppA immune serum identified two discrete regions on each construct. These potentially protective regions were mapped on a three-dimensional computational model of OppA, where regions with solvent-accessible amino acids were identified as three potentially protective epitopes. In all, these studies revealed two regions with three specific epitopes in OppA that induce potentially protective antibody responses following vaccination. Detection of antibodies to these regions could serve to guide vaccine formulation and as a diagnostic tool for monitoring development of protective responses during clinical trials.

A Prospective Study of Bacteriological Etiology in Hospitalized Acute Exacerbation of COPD Patients: Relationship with Lung Function and Respiratory Failure

OBJECTIVES

Bacterial infections are the major cause of acute exacerbation of COPD (AE-COPD). The relationship between lung functions and respiratory failure (arterial blood gas parameters) with the etiology of AE-COPD has not been clearly understood. We conducted this study to determine the bacterial profile in AE-COPD and to identify the associated risk factors and drug sensitivity pattern.

MATERIAL AND METHODS

Seventy-two patients hospitalized for AE-COPD were prospectively evaluated. Quantitative sputum culture, blood gas analysis, and drug sensitivity testing were performed at the time of admission, and pulmonary function testing was performed 6 weeks after discharge as per standard guidelines.

RESULTS

Bacterial pathogens were isolated in 34 (47.22%) cases. Pathogens isolated were Pseudomonas aeruginosa (38.23%), Klebsiella pneumoniae (29.41%), Staphylococcus aureus (23.53%), Streptococcus pneumoniae (5.88%), and Acinetobacter spp. (2.94%). Isolation of bacterial pathogen was observed in patients with advancing age (p=0.02), frequent exacerbations (p<0.001), systemic steroid use (p=0.005), and deranged lung function (p=0.02). Binary logistic regression analysis revealed that higher partial pressure of carbon dioxide (PaCO2) was independently associated with isolation of K. pneumoniae (p=0.025) and P. aeruginosa (p=0.001). Additional independent factors that favor isolation of K. pneumoniae were age >55 years (p=0.017) and systemic steroid use (p=0.017). Antibiotic sensitivity testing showed that ciprofloxacin and piperacillin/tazobactum were effective in 27/34 (79.41%) of isolates followed by gentamycin in 26/34 (76%).

CONCLUSION

Hypercapnic respiratory failure is an independent risk factor for isolation of K. pneumoniae and P. aeruginosa in addition to advanced age and systemic steroid use. These findings may be an important adjunct in deciding the initial antibiotic therapy.

A Moraxella catarrhalis vaccine to protect against otitis media and exacerbations of COPD: An update on current progress and challenges

Moraxella catarrhalis is a major cause of morbidity and mortality worldwide, especially causing otitis media in young children and exacerbations of chronic obstructive pulmonary disease in adults. This pathogen uses several virulence mechanisms to colonize and survive in its host, including adherence and invasion of host cells, formation of polymicrobial biofilms with other bacterial pathogens, and production of β-lactamase. Given the global impact of otitis media and COPD, an effective vaccine to prevent M. catarrhalis infection would have a huge impact on the quality of life in both patient populations by preventing disease, thus reducing morbidity and health care costs. A number of promising vaccine antigens have been identified for M. catarrhalis. The development of improved animal models of M. catarrhalis disease and identification of a correlate of protection are needed to accelerate vaccine development. This review will discuss the current state of M. catarrhalis vaccine development, and the challenges that must be addressed to succeed.

Virulence determinants of Moraxella catarrhalis: distribution and considerations for vaccine development

Moraxella catarrhalis is a human-restricted opportunistic bacterial pathogen of the respiratory mucosa. It frequently colonizes the nasopharynx asymptomatically, but is also an important causative agent of otitis media (OM) in children, and plays a significant role in acute exacerbations of chronic obstructive pulmonary disease (COPD) in adults. As the current treatment options for M. catarrhalis infection in OM and exacerbations of COPD are often ineffective, the development of an efficacious vaccine is warranted. However, no vaccine candidates for M. catarrhalis have progressed to clinical trials, and information regarding the distribution of M. catarrhalis virulence factors and vaccine candidates is inconsistent in the literature. It is largely unknown if virulence is associated with particular strains or subpopulations of M. catarrhalis, or if differences in clinical manifestation can be attributed to the heterogeneous expression of specific M. catarrhalis virulence factors in the circulating population. Further investigation of the distribution of M. catarrhalis virulence factors in the context of carriage and disease is required so that vaccine development may be targeted at relevant antigens that are conserved among disease-causing strains. The challenge of determining which of the proposed M. catarrhalis virulence factors are relevant to human disease is amplified by the lack of a standardized M. catarrhalis typing system to facilitate direct comparisons of worldwide isolates. Here we summarize and evaluate proposed relationships between M. catarrhalis subpopulations and specific virulence factors in the context of colonization and disease, as well as the current methods used to infer these associations.

A Cation-Binding Surface Protein as a Vaccine Antigen To Prevent Moraxella catarrhalis Otitis Media and Infections in Chronic Obstructive Pulmonary Disease

Moraxella catarrhalis is an exclusively human respiratory tract pathogen that is a common cause of otitis media in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. A vaccine to prevent these infections would have a major impact on reducing the substantial global morbidity and mortality in these populations. Through a genome mining approach, we identified AfeA, an ∼32-kDa substrate binding protein of an ABC transport system, as an excellent candidate vaccine antigen. Recombinant AfeA was expressed and purified and binds ferric, ferrous, manganese, and zinc ions, as demonstrated by thermal shift assays. It is a highly conserved protein that is present in all strains of M. catarrhalis Immunization with recombinant purified AfeA induces high-titer antibodies that recognize the native M. catarrhalis protein. AfeA expresses abundant epitopes on the bacterial surface and induces protective responses in the mouse pulmonary clearance model following aerosol challenge with M. catarrhalis Finally, AfeA is expressed during human respiratory tract infection of adults with chronic obstructive pulmonary disease (COPD). Based on these observations, AfeA is an excellent vaccine antigen to be included in a vaccine to prevent infections caused by M. catarrhalis.

Microbiota Promotes Chronic Pulmonary Inflammation by Enhancing IL-17A and Autoantibodies

RATIONALE

Changes in the pulmonary microbiota are associated with progressive respiratory diseases including chronic obstructive pulmonary disease (COPD). Whether there is a causal relationship between these changes and disease progression remains unknown.

OBJECTIVES

To investigate the link between an altered microbiota and disease, we used a murine model of chronic lung inflammation that is characterized by key pathological features found in COPD and compared responses in specific pathogen-free (SPF) mice and mice depleted of microbiota by antibiotic treatment or devoid of a microbiota (axenic).

METHODS

Mice were challenged with LPS/elastase intranasally over 4 weeks, resulting in a chronically inflamed and damaged lung. The ensuing cellular infiltration, histological damage, and decline in lung function were quantified.

MEASUREMENTS AND MAIN RESULTS

Similar to human disease, the composition of the pulmonary microbiota was altered in diseased animals. We found that the microbiota richness and diversity were decreased in LPS/elastase-treated mice, with an increased representation of the genera Pseudomonas and Lactobacillus and a reduction in Prevotella. Moreover, the microbiota was implicated in disease development as mice depleted, or devoid, of microbiota exhibited an improvement in lung function, reduced inflammation, and lymphoid neogenesis. The absence of microbial cues markedly decreased the production of IL-17A, whereas intranasal transfer of fluid enriched with the pulmonary microbiota isolated from diseased mice enhanced IL-17A production in the lungs of antibiotic-treated or axenic recipients. Finally, in mice harboring a microbiota, neutralizing IL-17A dampened inflammation and restored lung function.

CONCLUSIONS

Collectively, our data indicate that host-microbial cross-talk promotes inflammation and could underlie the chronicity of inflammatory lung diseases.

Isogenic mutations in the Moraxella catarrhalis CydDC system display pleiotropic phenotypes and reveal the role of a palindrome sequence in its transcriptional regulation

Moraxella catarrhalis is becoming an important human respiratory tract pathogen affecting significant proportions from the population. However, still little is known about its physiology and molecular regulation. To this end, the CydDC, which is a heterodimeric ATP binding cassette transporter that has been shown to contribute to the maintenance of the redox homeostasis across the periplasm in other Gram-negative bacteria, is studied here. Amino acids multiple sequence alignments indicated that M. catarrhalis CydC is different from the CydC proteins of the bacterial species in which this system has been previously studied. These findings prompted further interest in studying this system in M. catarrhalis. Isogenic mutant in the CydDC system showed suppression in growth rate, hypersensitivity to oxidative and reductive stress and increased accumulation of intracellular cysteine levels. In addition, the growth of cydC^- mutant exhibited hypersensitivity to exogenous cysteine; however, it did not display a significant difference from its wild-type counterpart in the murine pulmonary clearance model. Moreover, a palindrome was detected 94bp upstream of the cydD ORF suggesting it might act as a potential regulatory element. Real-time reverse transcription-PCR analysis showed that deletion/change in the palindrome resulted into alterations in the transcription levels of cydC. A better understanding of such system and its regulation helps in developing better ways to combat M. catarrhalis infections.

Secondary Bacterial Infections Associated with Influenza Pandemics

Lower and upper respiratory infections are the fourth highest cause of global mortality (Lozano et al., 2012). Epidemic and pandemic outbreaks of respiratory infection are a major medical concern, often causing considerable disease and a high death toll, typically over a relatively short period of time. Influenza is a major cause of epidemic and pandemic infection. Bacterial co/secondary infection further increases morbidity and mortality of influenza infection, with Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus reported as the most common causes. With increased antibiotic resistance and vaccine evasion it is important to monitor the epidemiology of pathogens in circulation to inform clinical treatment and development, particularly in the setting of an influenza epidemic/pandemic.

The Contribution of Small Airway Obstruction to the Pathogenesis of Chronic Obstructive Pulmonary Disease

The hypothesis that the small conducting airways were the major site of obstruction to airflow in normal lungs was introduced by Rohrer in 1915 and prevailed until Weibel introduced a quantitative method of studying lung anatomy in 1963. Green repeated Rohrer's calculations using Weibels new data in 1965 and found that the smaller conducting airways offered very little resistance to airflow. This conflict was resolved by seminal experiments conducted by Macklem and Mead in 1967, which confirmed that a small proportion of the total lower airways resistance is attributable to small airways <2 mm in diameter. Shortly thereafter, Hogg, Macklem, and Thurlbeck used this technique to show that small airways become the major site of obstruction in lungs affected by emphysema. These and other observations led Mead to write a seminal editorial in 1970 that postulated the small airways are a silent zone within normal lungs where disease can accumulate over many years without being noticed. This review provides a progress report since the 1970s on methods for detecting chronic obstructive pulmonary disease, the structural nature of small airways' disease, and the cellular and molecular mechanisms that are thought to underlie its pathogenesis.

The role of acute and chronic respiratory colonization and infections in the pathogenesis of COPD

COPD is a major global concern, increasingly so in the context of ageing populations. The role of infections in disease pathogenesis and progression is known to be important, yet the mechanisms involved remain to be fully elucidated. While COPD pathogens such as Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae are strongly associated with acute exacerbations of COPD (AECOPD), the clinical relevance of these pathogens in stable COPD patients remains unclear. Immune responses in stable and colonized COPD patients are comparable to those detected in AECOPD, supporting a role for chronic colonization in COPD pathogenesis through perpetuation of deleterious immune responses. Advances in molecular diagnostics and metagenomics now allow the assessment of microbe–COPD interactions with unprecedented personalization and precision, revealing changes in microbiota associated with the COPD disease state. As microbial changes associated with AECOPD, disease severity and therapeutic intervention become apparent, a renewed focus has been placed on the microbiology of COPD and the characterization of the lung microbiome in both its acute and chronic states. Characterization of bacterial, viral and fungal microbiota as part of the lung microbiome has the potential to reveal previously unrecognized prognostic markers of COPD that predict disease outcome or infection susceptibility. Addressing such knowledge gaps will ultimately lead to a more complete understanding of the microbe–host interplay in COPD. This will permit clearer distinctions between acute and chronic infections and more granular patient stratification that will enable better management of these features and of COPD.

Bacterial infections in patients with primary ciliary dyskinesia: Comparison with cystic fibrosis

Primary ciliary dyskinesia (PCD) is an autosomal recessive disorder associated with severely impaired mucociliary clearance caused by defects in ciliary structure and function. Although recurrent bacterial infection of the respiratory tract is one of the major clinical features of this disease, PCD airway microbiology is understudied. Despite the differences in pathophysiology, assumptions about respiratory tract infections in patients with PCD are often extrapolated from cystic fibrosis (CF) airway microbiology. This review aims to summarize the current understanding of bacterial infections in patients with PCD, including infections with Pseudomonas aeruginosa, Staphylococcus aureus, and Moraxella catarrhalis, as it relates to bacterial infections in patients with CF. Further, we will discuss current and potential future treatment strategies aimed at improving the care of patients with PCD suffering from recurring bacterial infections.

Potential impact of a Moraxella catarrhalis vaccine in COPD

Moraxella catarrhalis is the second most common cause of exacerbations in adults with COPD, resulting in enormous morbidity and mortality in this clinical setting. Vaccine development for M. catarrhalis has lagged behind the other two important causes of exacerbations in COPD, nontypeable Haemophilus influenzae and Streptococcus pneumoniae. While no licensed vaccine is currently available for M. catarrhalis, several promising candidate vaccine antigens have been identified and characterized and are close to entering clinical trials. Key steps that are required to advance vaccines for M. catarrhalis along the translational pipeline include standardization of assay systems to assess candidate antigens, identification of a reliable correlate of protection and expansion of partnerships between industry, academia and government to overcome regulatory hurdles. A vaccine to prevent M. catarrhalis infections in COPD would have a major impact in reducing morbidity, mortality and healthcare costs in COPD.

PRELP Enhances Host Innate Immunity against the Respiratory Tract Pathogen Moraxella catarrhalis

Respiratory tract infections are one of the leading causes of mortality worldwide urging better understanding of interactions between pathogens causing these infections and the host. Here we report that an extracellular matrix component proline/arginine-rich end leucine-rich repeat protein (PRELP) is a novel antibacterial component of innate immunity. We detected the presence of PRELP in human bronchoalveolar lavage fluid and showed that PRELP can be found in alveolar fluid, resident macrophages/monocytes, myofibroblasts, and the adventitia of blood vessels in lung tissue. PRELP specifically binds respiratory tract pathogens Moraxella catarrhalis, Haemophilus influenzae, and Streptococcus pneumoniae, but not other bacterial pathogens tested. We focused our study on M. catarrhalis and found that PRELP binds the majority of clinical isolates of M. catarrhalis (n = 49) through interaction with the ubiquitous surface protein A2/A2H. M. catarrhalis usually resists complement-mediated serum killing by recruiting to its surface a complement inhibitor C4b-binding protein, which is also a ligand for PRELP. We found that PRELP competitively inhibits binding of C4b-binding protein to bacteria, which enhances membrane attack complex formation on M. catarrhalis and thus leads to increased serum sensitivity. Furthermore, PRELP enhances phagocytic killing of serum-opsonized M. catarrhalis by human neutrophils in vitro. Moreover, PRELP reduces Moraxella adherence to and invasion of human lung epithelial A549 cells. Taken together, PRELP enhances host innate immunity against M. catarrhalis through increasing complement-mediated attack, improving phagocytic killing activity of neutrophils, and preventing bacterial adherence to lung epithelial cells.