TLR4 Polymorphism, Nasopharyngeal Bacterial Colonization, and the Development of Childhood Asthma: A Prospective Birth-Cohort Study in Finnish Children

We aimed to explore the role of TLR4 (rs4986790) polymorphism in the nasopharyngeal (NP) bacterial colonization and its consequent impact on the development of childhood asthma. A semi-quantitative culture of NP swabs was performed on 473 children at 2 months of age and on 213 children at 13 months of age. TLR4 polymorphism was analyzed for 396 children. Children were followed from birth to the age of 7.5 years and the final outcome was physician-diagnosed asthma. The associations between TLR4 genotype, bacterial colonization, and asthma were analyzed. Children with TLR4 AG or GG genotype were more often colonized with Moraxella catarrhalis at 2 months of age (p = 0.009) and Haemophilus influenzae at 13 months of age (p = 0.018). Children who were colonized with H. influenzae at 13 months of age had a significantly higher risk of later development of asthma (p = 0.004). M. catarrhalis or H. Influenzae colonization at 2 months of age or TLR4 genotype Asp299Gly were not associated with the development of childhood asthma. TLR4 Asp299Gly polymorphism was associated with an increased risk of colonization of M. catarrhalis and H. influenzae in children. The colonization with H. influenzae at 13 months of age was associated with a higher risk of later development of childhood asthma.

HIRA-TAN detects pathogens of pneumonia with a progressive course despite antibiotic treatment

BACKGROUND

Empiric antibiotics are administered for pneumonia when the causative pathogens are unidentified. Pathogen-directed therapy is impeded by negative culture results and/or culture time lag. This circumstance necessitates a salvage method for pathogen identification, especially when antibiotic therapy has failed. Here, we aimed to preliminarily investigate the HIRA-TAN method in pneumonia with a progressive course despite prior empiric antibiotic therapy.

METHODS

This prospective study was conducted for patients who were referred to Dr. Zainoel Abidin Hospital, Aceh, Indonesia, from December 2016 to January 2017, owing to pneumonia with a progressive course. Sputum or pleural effusion was subjected to culture and the HIRA-TAN assay. The HIRA-TAN identified the candidate causative pathogens based on the difference in the cycle threshold (Ct) between the targeted pathogen and the single-copy human gene.

RESULTS

Patients (n=27) were predominantly males (22 patients, 81.5%), with a median age of 62 years. All patients had comorbid disease and were classified as hospital-acquired pneumonia (25 patients, 92.6%) with multilobar infiltrates (22 patients, 81.5%). Bacterial culture identified causative pathogen(s) in some (14 patients, 51.8%), whereas the HIRA-TAN identified pathogen(s) in most (23 patients, 85.2%). The rapid pathogen identification by the HIRA-TAN will provide valuable information in guiding pathogen-directed therapy.

CONCLUSIONS

The result warrants a larger clinical trial to confirm the clinical efficacy of the HIRA-TAN in patients with progressive pneumonia despite previous antibiotic treatment.

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.

Increased Nasopharyngeal Density and Concurrent Carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis Are Associated with Pneumonia in Febrile Children

Background

We assessed nasopharyngeal (NP) carriage of five pathogens in febrile children with and without acute respiratory infection (ARI) of the upper (URTI) or lower tract, attending health facilities in Tanzania.

Methods

NP swabs collected from children (N = 960) aged 2 months to 10 years, and with a temperature ≥38°C, were utilized to quantify bacterial density of S. pneumoniae (Sp), H. influenzae (Hi), M. catarrhalis (Mc), S. aureus (Sa), and N. meningitidis (Nm). We determined associations between presence of individual species, densities, or concurrent carriage of all species combination with respiratory diseases including clinical pneumonia, pneumonia with normal chest radiography (CXR) and endpoint pneumonia.

Results

Individual carriage, and NP density, of Sp, Hi, or Mc, but not Sa, or Nm, was significantly associated with febrile ARI and clinical pneumonia when compared to febrile non-ARI episodes. Density was also significantly increased in severe pneumonia when compared to mild URTI (Sp, p<0.002; Hi p<0.001; Mc, p = 0.014). Accordingly, concurrent carriage of Sp⁺, Hi⁺, and Mc⁺, in the absence of Sa^- and Nm^-, was significantly more prevalent in children with ARI (p = 0.03), or clinical pneumonia (p<0.001) than non-ARI, and in children with clinical pneumonia (p = 0.0007) than URTI. Furthermore, Sp⁺, Hi⁺, and Mc⁺ differentiated children with pneumonia with normal CXR, or endpoint pneumonia, from those with URTI, and non-ARI cases.

Conclusions

Concurrent NP carriage of Sp, Hi, and Mc was a predictor of clinical pneumonia and identified children with pneumonia with normal CXR and endpoint pneumonia from those with febrile URTI, or non-ARI episodes.

ATP-Binding Cassette (ABC) Transporters of the Human Respiratory Tract Pathogen, Moraxella catarrhalis: Role in Virulence

Moraxella catarrhalis is a human respiratory tract pathogen that causes otitis media (middle ear infections) in children and respiratory tract infections in adults with chronic obstructive pulmonary disease. In view of the huge global burden of disease caused by M. catarrhalis, the development of vaccines to prevent these infections and better approaches to treatment have become priorities. In previous work, we used a genome mining approach that identified three substrate binding proteins (SBPs) of ATP-binding cassette (ABC) transporters as promising candidate vaccine antigens. In the present study, we performed a comprehensive assessment of 19 SBPs of 15 ABC transporter systems in the M. catarrhalis genome by engineering knockout mutants and studying their role in assays that assess mechanisms of infection. The capacity of M. catarrhalis to survive and grow in the nutrient-limited and hostile environment of the human respiratory tract, including intracellular growth, account in part for its virulence. The results show that ABC transporters that mediate uptake of peptides, amino acids, cations and anions play important roles in pathogenesis by enabling M. catarrhalis to 1) grow in nutrient-limited conditions, 2) invade and survive in human respiratory epithelial cells and 3) persist in the lungs in a murine pulmonary clearance model. The knockout mutants of SBPs and ABC transporters showed different patterns of activity in the assay systems, supporting the conclusion that different SBPs and ABC transporters function at different stages in the pathogenesis of infection. These results indicate that ABC transporters are nutritional virulence factors, functioning to enable the survival of M catarrhalis in the diverse microenvironments of the respiratory tract. Based on the role of ABC transporters as virulence factors of M. catarrhalis, these molecules represent potential drug targets to eradicate the organism from the human respiratory tract.

[THE PATHOGENIC POTENTIAL OF MORAXELLA CATARRHALIS AND STAPHYLOCOCCUS EPIDERMIDIS UNDER INFLAMMATORY PROCESSES OF UPPER RESPIRATORY TRACTS]

The frequent isolation from biological material of Moraxella catarrhalis under bronchitis and pneumonia and Staphilococcus epidermidis under rhinitis and sinusitis requires profound investigation offactors ofpathogenicity ofthe mentioned microorganisms. The genetic and phenotypic markers of virulence of strains M. catarrhalis and S. epidermidis are examined. Their etiologic role in development of infection processes of respiratory tract and middle ear is determined The most of M catarrhalis strains isolated under bronchitis and pneumonia have gene mcaP responsiblefor production ofprotein McaP that provides adhesion to epithelium cell of host and lipolitic activity of bacteria. The strains isolated from patients with pneumonia had the most adhesive activity. The cluster of genes ICA with leading role of gene icaA is responsible for for availability offactors of intercellular adhesion in Staphilococci strains. In the clinical samples from patients with sinusitis this gene is detected 5 times more frequently than from healthy individuals. In phenotypic tests, expression of gene icaA in S. epidermidis isolated from patients is three times higher than in strains isolated from healthy individuals. To establish etiologic role of M. catarrhalis and S. epidermidis and to develop tactic of therapy of patients with bronchitis, pneumonia and sinusitis complex approach is needed, including detection of genetic and phenotypic markers of virulence in isolated microorganisms.

The role and regulation of Moraxella catarrhalis-induced human beta-defensin 3 expression in human pulmonary epithelial cells

BACKGROUND

Bacterial colonisation with Moraxella catarrhalis may partly sustain chronic inflammation in the lower airways of patients with chronic obstructive pulmonary disease (COPD). In addition, this bacterium causes infectious exacerbations of COPD, which often necessitate treatment with antibiotics. Antimicrobial peptides are the body's own antibiotic substances with bactericidal and bacteriostatic, as well as immunomodulatory function. In particular, human beta-defensin 3 (hBD-3) exerts an antimicrobial effect against an extraordinarily broad spectrum of pathogens. We therefore investigated the role of hBD-3 in infections of pulmonary epithelial cells with M. catarrhalis.

METHODS

The antimicrobial activity of hBD-3 vs. M. catarrhalis was evaluated in an antimicrobial susceptibility assay. We analyzed hBD-3 secretion of M. catarrhalis-infected pulmonary epithelial cells using ELISA. The role of M. catarrhalis-specific virulence factors, toll-like receptors (TLR) 2 and 4, MAPK pathways, and transcription factors AP-1 and NF-κB in the induction and regulation of hBD-3 expression were explored with specific inhibitors, small interference RNA, Western Blot, and chromatin immunoprecipitation (ChIP) assays.

RESULTS

HBD-3 exhibited a strong bactericidal effect against M. catarrhalis. M. catarrhalis induced hBD-3 expression in pulmonary epithelial cells, which was dependent on M. catarrhalis membranous lipoolygosaccharide (LOS), while the surface proteins UspA1 and UspA2 were not involved. Gene silencing of TLR2, but not TLR4, led to a reduced hBD-3 secretion after stimulation with M. catarrhalis or M. catarrhalis LOS. Inhibition of MAPKs ERK1/2 and JNK, but not p38, reduced hBD-3 secretion. HBD-3 expression was mediated through the recruitment of AP-1 to the hBD-3 gene promoter and was independent of NF-κB.

CONCLUSION

The immune response of pulmonary epithelial cells towards M. catarrhalis involves secretion of hBD-3, which has a bactericidal effect against this pathogen. Binding of M. catarrhalis virulence factor LOS to TLR2 causes an ERK1/2- and JNK-dependent induction of AP-1-related transcription of the hBD-3 gene, resulting in the production and secretion of hBD-3.

Role of Lipooligosaccharide in the Attachment ofMoraxella catarrhalisto Human Pharyngeal Epithelial Cells

The goal of this study was to determine the role of lipooligosaccharide in the attachment of Moraxella catarrhalis to human pharyngeal epithelial cells. Strain 2951 and its P(k) mutant strain 2951 galE were used in this study. This study suggests that the P(k) epitope of LOS is not an adhesin for M. catarrhalis, but plays a crucial role by its surface charge in the initial stage of attachment.

Longitudinal nasopharyngeal carriage and antibiotic resistance of respiratory bacteria in indigenous Australian and Alaska native children with bronchiectasis

Background

Indigenous children in Australia and Alaska have very high rates of chronic suppurative lung disease (CSLD)/bronchiectasis. Antibiotics, including frequent or long-term azithromycin in Australia and short-term beta-lactam therapy in both countries, are often prescribed to treat these patients. In the Bronchiectasis Observational Study we examined over several years the nasopharyngeal carriage and antibiotic resistance of respiratory bacteria in these two PCV7-vaccinated populations.

Methods

Indigenous children aged 0.5–8.9 years with CSLD/bronchiectasis from remote Australia (n = 79) and Alaska (n = 41) were enrolled in a prospective cohort study during 2004–8. At scheduled study visits until 2010 antibiotic use in the preceding 2-weeks was recorded and nasopharyngeal swabs collected for culture and antimicrobial susceptibility testing. Analysis of respiratory bacterial carriage and antibiotic resistance was by baseline and final swabs, and total swabs by year.

Results

Streptococcus pneumoniae carriage changed little over time. In contrast, carriage of Haemophilus influenzae declined and Staphylococcus aureus increased (from 0% in 2005–6 to 23% in 2010 in Alaskan children); these changes were associated with increasing age. Moraxella catarrhalis carriage declined significantly in Australian, but not Alaskan, children (from 64% in 2004–6 to 11% in 2010). While beta-lactam antibiotic use was similar in the two cohorts, Australian children received more azithromycin. Macrolide resistance was significantly higher in Australian compared to Alaskan children, while H. influenzae beta-lactam resistance was higher in Alaskan children. Azithromycin use coincided significantly with reduced carriage of S. pneumoniae, H. influenzae and M. catarrhalis, but increased carriage of S. aureus and macrolide-resistant strains of S. pneumoniae and S. aureus (proportion of carriers and all swabs), in a ‘cumulative dose-response’ relationship.

Conclusions

Over time, similar (possibly age-related) changes in nasopharyngeal bacterial carriage were observed in Australian and Alaskan children with CSLD/bronchiectasis. However, there were also significant frequency-dependent differences in carriage and antibiotic resistance that coincided with azithromycin use.

RNA-Seq-based analysis of the physiologic cold shock-induced changes in Moraxella catarrhalis gene expression

BACKGROUND

Moraxella catarrhalis, a major nasopharyngeal pathogen of the human respiratory tract, is exposed to rapid downshifts of environmental temperature when humans breathe cold air. The prevalence of pharyngeal colonization and respiratory tract infections caused by M. catarrhalis is greatest in winter. We investigated how M. catarrhalis uses the physiologic exposure to cold air to regulate pivotal survival systems that may contribute to M. catarrhalis virulence.

RESULTS

In this study we used the RNA-seq techniques to quantitatively catalogue the transcriptome of M. catarrhalis exposed to a 26 °C cold shock or to continuous growth at 37 °C. Validation of RNA-seq data using quantitative RT-PCR analysis demonstrated the RNA-seq results to be highly reliable. We observed that a 26 °C cold shock induces the expression of genes that in other bacteria have been related to virulence a strong induction was observed for genes involved in high affinity phosphate transport and iron acquisition, indicating that M. catarrhalis makes a better use of both phosphate and iron resources after exposure to cold shock. We detected the induction of genes involved in nitrogen metabolism, as well as several outer membrane proteins, including ompA, m35-like porin and multidrug efflux pump (acrAB) indicating that M. catarrhalis remodels its membrane components in response to downshift of temperature. Furthermore, we demonstrate that a 26 °C cold shock enhances the induction of genes encoding the type IV pili that are essential for natural transformation, and increases the genetic competence of M. catarrhalis, which may facilitate the rapid spread and acquisition of novel virulence-associated genes.

CONCLUSION

Cold shock at a physiologically relevant temperature of 26 °C induces in M. catarrhalis a complex of adaptive mechanisms that could convey novel pathogenic functions and may contribute to enhanced colonization and virulence.

[Study of prevalence of rare and difficult to cultivate causative agents of inflammatory diseases of respiratory organs]

AIM

Study the prevalence of Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, Legionella pneumophila, Moraxella catarrhalis, Cytomegalovirus, Herpes simplex I/II virus (HSV I/II) in individuals of various age groups with varying inflammatory broncho-pulmonary diseases.

MATERIALS AND METHODS

384 adults and 1001 children with clinically confirmed diagnoses were examined by PCR method: community-acquired pneumonia, acute bronchitis, bronchial asthma, ARD/ARVD, as well as 127 healthy children and 52 healthy adults. Sputum, smears from posterior fornix of pharynx, blood, saliva from children of the first year of life were used as material for the study.

RESULTS

Wide prevalence of M. pneumoniae and C. pneumoniae among adults and M. pneumoniae among children older than 1 year with inflammatory diseases of respiratory organs was established. C. psittaci, L. pneumophila, M. catarrhalis occurred in isolated cases in both adults and children. Active replication of herpes group viruses was detected in patients of all age groups with inflammatory broncho-pulmonary diseases, and in children Cytomegalovirus replication predominated, in adults--HSV I/II.

CONCLUSION

High frequency of prevalence of M. pneumoniae and C. pneumoniae in inflammatory diseases of respiratory tract was established, giving evidence of reasonability and necessity of examination of patients with various nosologic forms of diseases for these species of microorganisms with the aim of effective etiotropic therapy.

Colonization of healthy children by Moraxella catarrhalis is characterized by genotype heterogeneity, virulence gene diversity and co-colonization with Haemophilus influenzae

The colonization dynamics of Moraxella catarrhalis were studied in a population comprising 1079 healthy children living in Rotterdam, The Netherlands (the Generation R Focus cohort). A total of 2751 nasal swabs were obtained during four clinic visits timed to take place at 1.5, 6, 14 and 24 months of age, yielding a total of 709 M. catarrhalis and 621 Haemophilus influenzae isolates. Between January 2004 and December 2006, approximate but regular 6-monthly cycles of colonization were observed, with peak colonization incidences occurring in the autumn/winter for M. catarrhalis, and winter/spring for H. influenzae. Co-colonization was significantly more likely than single-species colonization with either M. catarrhalis or H. influenzae, with genotypic analysis revealing no clonality for co-colonizing or single colonizers of either bacterial species. This finding is especially relevant considering the recent discovery of the importance of H. influenzae-M. catarrhalis quorum sensing in biofilm formation and host clearance. Bacterial genotype heterogeneity was maintained over the 3-year period of the study, even within this relatively localized geographical region, and there was no association of genotypes with either season or year of isolation. Furthermore, chronological and genotypic diversity in three immunologically important M. catarrhalis virulence genes (uspA1, uspA2 and hag/mid) was also observed. This study indicates that genotypic variation is a key factor contributing to the success of M. catarrhalis colonization of healthy children in the first years of life. Furthermore, variation in immunologically relevant virulence genes within colonizing populations, and even within genotypically identical M. catarrhalis isolates, may be a result of immune evasion by this pathogen. Finally, the factors facilitating M. catarrhalis and H. influenzae co-colonization need to be further investigated.

B cell activation by outer membrane vesicles--a novel virulence mechanism

Secretion of outer membrane vesicles (OMV) is an intriguing phenomenon of Gram-negative bacteria and has been suggested to play a role as virulence factors. The respiratory pathogens Moraxella catarrhalis reside in tonsils adjacent to B cells, and we have previously shown that M. catarrhalis induce a T cell independent B cell response by the immunoglobulin (Ig) D-binding superantigen MID. Here we demonstrate that Moraxella are endocytosed and killed by human tonsillar B cells, whereas OMV have the potential to interact and activate B cells leading to bacterial rescue. The B cell response induced by OMV begins with IgD B cell receptor (BCR) clustering and Ca(2+) mobilization followed by BCR internalization. In addition to IgD BCR, TLR9 and TLR2 were found to colocalize in lipid raft motifs after exposure to OMV. Two components of the OMV, i.e., MID and unmethylated CpG-DNA motifs, were found to be critical for B cell activation. OMV containing MID bound to and activated tonsillar CD19(+) IgD(+) lymphocytes resulting in IL-6 and IgM production in addition to increased surface marker density (HLA-DR, CD45, CD64, and CD86), whereas MID-deficient OMV failed to induce B cell activation. DNA associated with OMV induced full B cell activation by signaling through TLR9. Importantly, this concept was verified in vivo, as OMV equipped with MID and DNA were found in a 9-year old patient suffering from Moraxella sinusitis. In conclusion, Moraxella avoid direct interaction with host B cells by redirecting the adaptive humoral immune response using its superantigen-bearing OMV as decoys.

Moraxella catarrhalis associated with acute urethritis imitating gonorrhoea acquired by oral-genital contact

A case of heterosexual transmission of Moraxella catarrhalis by fellatio, which resulted in acute purulent urethritis mimicking gonorrhoea in the male partner, is described. In male patients with urethritis due to M. catarrhalis, orogenital contact with a sexual partner carrying the organism in his/her oropharynx is the probable route of transmission.

Contribution of Moraxella catarrhalis type IV pili to nasopharyngeal colonization and biofilm formation

Moraxella catarrhalis is a gram-negative mucosal pathogen of the human respiratory tract. Although little information is available regarding the initial steps of M. catarrhalis pathogenesis, this organism must be able to colonize the human mucosal surface in order to initiate an infection. Type IV pili (TFP), filamentous surface appendages primarily comprised of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of bacteria. We previously identified the genes that encode the major proteins involved in the biosynthesis of M. catarrhalis TFP and determined that the TFP expressed by this organism are highly conserved and essential for natural transformation. We extended this initial study by investigating the contribution of TFP to the early stages of M. catarrhalis colonization. TFP-deficient M. catarrhalis bacteria exhibit diminished adherence to eukaryotic cells in vitro. Additionally, our studies demonstrate that M. catarrhalis cells form a mature biofilm in continuous-flow chambers and that biofilm formation is enhanced by TFP expression. The potential role of TFP in colonization by M. catarrhalis was further investigated using in vivo studies comparing the abilities of wild-type M. catarrhalis and an isogenic TFP mutant to colonize the nasopharynx of the chinchilla. These results suggest that the expression of TFP contributes to mucosal airway colonization. Furthermore, these data indicate that the chinchilla model of nasopharyngeal colonization provides an effective animal system for studying the early steps of M. catarrhalis pathogenesis.

The rise and spread of a new pathogen: seroresistant Moraxella catarrhalis

The nosocomial human pathogen Moraxella catarrhalis is one the most important agents of human respiratory tract infections. This species is composed of two distinct lineages, one of only moderate virulence, the so-called serosensitive subpopulation, and a second, the seroresistant one, which is enriched among strains that harbor two major virulence traits: complement resistance and adherence to epithelial cells. Using a suite of population genetics tools, we show that the seroresistant lineage is also characterized by higher homologous recombination and mutation rates at housekeeping genes relative to its less pathogenic counterpart. Thus, sex and virulence have evolved in tandem in M. catarrhalis. Moreover, phylogenetic and Bayesian analyses that take into account recombination between the two clades show that the ancestral group was avirulent, is possibly 70 million years old, and must have infected mammals prior to the evolution of humans, which occurred later. The younger seroresistant isolates went through an important population expansion some 5 million years ago, coincident with the hominid expansion. This rise and spread was possibly coupled with a host shift and the acquisition of virulence genes.

Role of different moieties from the lipooligosaccharide molecule in biological activities of the Moraxella catarrhalis outer membrane

Lipooligosaccharide (LOS), a major component of the outer membrane of Moraxella catarrhalis, consists of two major moieties: a lipid A and a core oligosaccharide (OS). The core OS can be dissected into a linker and three OS chains. To gain an insight into the biological activities of the LOS molecules of M. catarrhalis, we used a random transposon mutagenesis approach with an LOS specific monoclonal antibody to construct a serotype A O35Elgt3 LOS mutant. MALDI-TOF-MS of de-O-acylated LOS from the mutant and glycosyl composition, linkage, and NMR analysis of its OS indicated that the LOS contained a truncated core OS and consisted of a Glc-Kdo(2) (linker)-lipid A structure. Phenotypic analysis revealed that the mutant was similar to the wild-type strain in its growth rate, toxicity and susceptibility to hydrophobic reagents. However, the mutant was sensitive to bactericidal activity of normal human serum and had a reduced adherence to human epithelial cells. These data, combined with our previous data obtained from mutants which contained only lipid A or lacked LOS, suggest that the complete OS chain moiety of the LOS is important for serum resistance and adherence to epithelial cells, whereas the linker moiety is critical for maintenance of the outer membrane integrity and stability to preserve normal cell growth. Both the lipid A and linker moieties contribute to the LOS toxicity.

Regions important for the adhesin activity of Moraxella catarrhalis Hag

BACKGROUND

The Moraxella catarrhalis Hag protein, an Oca autotransporter adhesin, has previously been shown to be important for adherence of this respiratory tract pathogen to human middle ear and A549 lung cells.

RESULTS

The present study demonstrates that adherence of M. catarrhalis isogenic hag mutant strains to the human epithelial cell lines Chang (conjunctival) and NCIH292 (lung) is reduced by 50-93%. Furthermore, expressing Hag in a heterologous Escherichia coli background substantially increased the adherence of recombinant bacteria to NCIH292 cells and murine type IV collagen. Hag did not, however, increase the attachment of E. coli to Chang cells. These results indicate that Hag directly mediates adherence to NCIH292 lung cells and collagen, but is not sufficient to confer binding to conjunctival monolayers. Several in-frame deletions were engineered within the hag gene of M. catarrhalis strain O35E and the resulting proteins were tested for their ability to mediate binding to NCIH292 monolayers, middle ear cells, and type IV collagen. These experiments revealed that epithelial cell and collagen binding properties are separable, and that residues 385-705 of this ~2,000 amino acid protein are important for adherence to middle ear and NCIH292 cells. The region of O35E-Hag encompassing aa 706 to 1194 was also found to be required for adherence to collagen. In contrast, beta-roll repeats present in Hag, which are structural features conserved in several Oca adhesins and responsible for the adhesive properties of Yersinia enterocolitica YadA, are not important for Hag-mediated adherence.

CONCLUSION

Hag is a major adherence factor for human cells derived from various anatomical sites relevant to pathogenesis by M. catarrhalis and its structure-function relationships differ from those of other, closely-related autotransporter proteins.

Haemophilus influenzaeSurvival during Complement‐Mediated Attacks Is Promoted byMoraxella catarrhalisOuter Membrane Vesicles

Moraxella catarrhalis causes respiratory tract infections in children and in adults with chronic obstructive pulmonary disease. It is often isolated as a copathogen with Haemophilus influenzae. The underlying mechanism for this cohabitation is unclear. Here, in clinical specimens from a patient with M. catarrhalis infection, we document that outer membrane vesicles (OMVs) carrying ubiquitous surface protein (Usp) A1 and UspA2 (hereafter, UspA1/A2) were secreted. Further analyses revealed that OMVs isolated in vitro also contained UspA1/A2, which mediate interactions with, among other proteins, the third component of the complement system (C3). OMVs from M. catarrhalis wild-type clinical strains bound to C3 and counteracted the complement cascade to a larger extent than did OMVs without UspA1/A2. In contrast, UspA1/A2-deficient OMVs were significantly weaker inhibitors of complement-dependent killing of H. influenzae. Thus, our results suggest that a novel strategy exists in which pathogens collaborate to conquer innate immunity and that the M. catarrhalis vaccine candidates UspA1/A2 play a major role in this interaction.

The UspA1 protein of Moraxella catarrhalis induces CEACAM-1-dependent apoptosis in alveolar epithelial cells

Moraxella catarrhalis is a major cause of exacerbations of chronic obstructive pulmonary disease (COPD) and emphysema. M. catarrhalis-specific UspA1 and the epithelial carcinoembryonic antigen-related cell adhesion molecule (CEACAM1) were required to induce apoptosis. M. catarrhalis-induced apoptosis was significantly enhanced in HeLa cells stably transfected with CEACAM1, compared with HeLa cells not expressing CEACAM1. Infected cells showed increased activity of caspases 3, 6, and 9 but not of caspase 8. Reduced expression of Bcl-2, translocation of Bax into the mitochondria, and cytosolic increase of apoptosis-inducing factor in M. catarrhalis-infected cells implicated the involvement of mitochondrial death pathways. In conclusion, M. catarrhalis induced apoptosis in pulmonary epithelial cells--a process that was triggered by interaction between CEACAM1 and UspA1. Thus, M. catarrhalis-induced apoptosis of pulmonary epithelial cells may contribute to the development of COPD and emphysema.

Sulfatide and its synthetic analogues recognition by Moraxella catarrhalis

Moraxella catarrhalis is one of the major pathogens of respiratory and middle ear infections. Attachment of this bacterium to the surface of human pharyngeal epithelial cells is the first step in the pathogenesis of infections. This study revealed that sulfatide might act as a binding molecule for the attachment of M. catarrhalis to human pharyngeal epithelial cells. Furthermore, six different synthetic sulfatides were found to inhibit the attachment of M. catarrhalis significantly at an optimum concentration of 10 microg/ml. Synthetic sulfatides may have the potential to be used as a therapy to prevent M. catarrhalis infections.

Moraxella catarrhalis strain O35E expresses two filamentous hemagglutinin-like proteins that mediate adherence to human epithelial cells

Two-partner secretion (TPS) systems are a family of proteins being rapidly identified and characterized in a growing number of gram-negative bacteria. TPS systems mediate the secretion of proteins, many involved in virulence traits such as hemolysis, adherence to epithelial cells, inhibition of bacterial growth, and immunomodulation of the host. A TPS system typically consists of a transporter located in the bacterial outer membrane (OM) which is responsible for the recognition and secretion of at least one large exoprotein. Two of the better-characterized TPS systems specify the Bordetella pertussis FHA and Haemophilus influenzae HMW1/HMW2 proteins. We identified three gene products of Moraxella catarrhalis strain O35E that resemble TPS proteins and designated them MhaC (transporter), MhaB1 (exoprotein), and MhaB2 (exoprotein). Western blot analysis using anti-MhaC, or antibodies reacting to both MhaB1 and MhaB2 (MhaB-reactive), revealed that these antigens are expressed in the OM of 63% of isolates tested. Mutations in the mhaC gene specifying the putative transporter of the M. catarrhalis wild-type strains O35E, O12E, and McGHS1 resulted in the absence of MhaB1/MhaB2 in the OM of mutants. These results are therefore consistent with the Mha proteins functioning as a TPS system. Furthermore, we discovered that these mhaC mutants exhibit markedly decreased binding to human epithelial cells relevant to pathogenesis by M. catarrhalis (Chang, HEp2, A549, and/or 16HBE14o(-)). Expression of O12E MhaC and MhaB1 in a nonadherent strain of Escherichia coli was found to increase the adherence of recombinant bacteria to HEp2 monolayers by sevenfold, thereby demonstrating that this M. catarrhalis TPS system directly mediates binding to human epithelial cells. The construction of isogenic mutants in the mhaB1 and mhaB2 genes of strain O35E also suggests that the MhaB proteins play distinct roles in M. catarrhalis adherence.

Structure and immunological action of the human pathogen Moraxella catarrhalis IgD-binding protein

Several pathogens have acquired the capacity to bind immunoglobulins in a nonimmune manner, that is, the binding does not involve the normal antigen-binding sites of the antibodies. In contrast to gram-positive bacteria, for example Staphylococus aureus, nonimmune binding to gram-negative bacteria is rare. Moraxella catarrhalis outer membrane protein MID is the first to date known IgD-binding protein. MID is a 200-kDa autotransporter protein that exists as an oligomer and is governed at the transcriptional level. The majority of M. catarrhalis clinical isolates expresses MID. Two functional domains have been attributed to MID. MID764-913 functions as an adhesin and promotes the bacteria to attach to epithelial cells. The IgD-binding domain is located within MID962-1200 and the IgD-binding is related to the secondary and tertiary structure, that is, an oligomer is required for an optimal interaction. In parallel, M. catarrhalis activates B lymphocytes through the IgD B-cell receptor. This stimulatory capacity can be blocked by anti-IgD polyclonal antibodies, and M. catarrhalis mutants devoid of MID do not stimulate B cells. Moreover, MID and MID962-1200 activates B lymphocytes in the presence of T-helper 2 cytokines or soluble CD40L. Thus, available data suggest that MID is a T-cell-independent antigen.

Naso- and oropharyngeal potential respiratory pathogens in adults with nonpneumonic lower respiratory tract infection

The objective of this prospective study was to determine positive isolation rates for potential respiratory pathogens (PRPs) in the naso- and oropharynx of adults hospitalized for nonpneumonic lower respiratory tract infection (NPLRTI), compared with patients with community-acquired pneumonia (CAP) and healthy controls. The study population was 315 non-chronic obstructive pulmonary disease adults hospitalized with febrile lower respiratory tract infection (158 NPLRTI and 157 CAP) and 450 control subjects. Each participant was sampled by oropharyngeal swab, nasopharyngeal swab, and nasopharyngeal washings that were tested by conventional bacteriologic methods to identify PRP. At least 1 of the samples was positive for at least 1 of the 3 PRP bacteria in 55 NPLRTI patients (35%) compared with 51 CAP patients (33%) (NS) and 100 controls (22%) (P = 0.003 compared with NPLRTI and P = 0.02 compared with CAP). Samples were positive for Streptococcus pneumoniae in 14 NPLRTI patients (9%) compared with 29 CAP patients (19%) (P = 0.02) and 16 controls (4%) (NPLRTI P = 0.015, CAP P < 0.0001). The corresponding rates for Haemophilus influenzae were 23 (15%), 16 (10%), and 60 (13%) (NS for all 3 comparisons), and for Moraxella catarrhalis, 28 (18%), 25 (16%), and 48 (11%), respectively (NPLRTI versus controls, P = 0.03, NS other comparisons). We conclude that the rate of positive naso/oropharyngeal isolates for at least 1 of the 3 PRP bacteria in NPLRTI patients is similar to the corresponding rates for CAP patients and is higher in both groups than in controls.

Identification of aMoraxella catarrhalisgene that confers adherence to various human epithelial cell linesin vitro

Moraxella catarrhalis is a pathogen of the human airways. We found that expression of the M. catarrhalis gene mcmA by Escherichia coli increases adherence to epithelial cells 100-fold. Furthermore, we discovered that disrupting mcmA decreases M. catarrhalis adherence to laryngeal and lung cells, which are relevant to pathogenesis by the bacterium.