Hag Mediates Adherence ofMoraxella catarrhalisto Ciliated Human Airway Cells

Abstract

Moraxella catarrhalis is a human pathogen causing otitis media in infants and respiratory infections in adults, particularly patients with chronic obstructive pulmonary disease. The surface protein Hag (also designated MID) has previously been shown to be a key adherence factor for several epithelial cell lines relevant to pathogenesis by M. catarrhalis, including NCIH292 lung cells, middle ear cells, and A549 type II pneumocytes. In this study, we demonstrate that Hag mediates adherence to air-liquid interface cultures of normal human bronchial epithelium (NHBE) exhibiting mucociliary activity. Immunofluorescent staining and laser scanning confocal microscopy experiments demonstrated that the M. catarrhalis wild-type isolates O35E, O12E, TTA37, V1171, and McGHS1 bind principally to ciliated NHBE cells and that their corresponding hag mutant strains no longer associate with cilia. The hag gene product of M. catarrhalis isolate O35E was expressed in the heterologous genetic background of a nonadherent Haemophilus influenzae strain, and quantitative assays revealed that the adherence of these recombinant bacteria to NHBE cultures was increased 27-fold. These experiments conclusively demonstrate that the hag gene product is responsible for the previously unidentified tropism of M. catarrhalis for ciliated NHBE cells.Moraxella catarrhalis is a gram-negative pathogen of the middle ear and lower respiratory tract (29,40,51,52,69,78). The organism is responsible for ϳ15% of bacterial otitis media cases in children and up to 10% of infectious exacerbations in patients with chronic obstructive pulmonary disease (COPD). The cost of treating these ailments places a large financial burden on the health care system, adding up to well over $10 billion per annum in the United States alone (29,40,52,95,97). In recent years, M. catarrhalis has also been increasingly associated with infections such as bronchitis, conjunctivitis, sinusitis, bacteremia, pneumonia, meningitis, pericarditis, and endocarditis (3, 12, 13, 17-19, 24, 25, 27, 51, 67, 70, 72, 92, 99, 102-104). Therefore, the organism is emerging as an important health problem.M. catarrhalis infections are a matter of concern due to high carriage rates in children, the lack of a preventative vaccine, and the rapid emergence of antibiotic resistance in clinical isolates. Virtually all M. catarrhalis strains are resistant to ␤-lactams (34,47,48,50,53,65,81,84). The genes specifying this resistance appear to be gram positive in origin (14, 15), suggesting that the organism could acquire genes conferring resistance to other antibiotics via horizontal transfer. Carriage rates as high as 81.6% have been reported for children (39,104). In one study, Faden and colleagues analyzed the nasopharynx of 120 children over a 2-year period and showed that 77.5% of these patients became colonized by M. catarrhalis (35). These investigators also observed a direct relationship between the development of otitis media and the frequency of colonization. This high carriage rate, coupled with th...

Characterization of an autotransporter adhesin protein shared by Burkholderia mallei and Burkholderia pseudomallei

“…BpaC expression was also found to increase adherence by 7-fold to normal human bronchial epithelium (NHBE) cultured in an air-liquid interface system, which has been shown to represent an environment similar to the airway lumen in vivo [54,63,64]. These results demonstrate that BpaC mediates adherence to respiratory epithelial cells.…”

“…Normal human bronchial epithelium (NHBE; LONZA) was expanded, cryopreserved and cultured in an air-liquid interface system as previously described [54,63,64]. The apical surface of the NHBE was exposed to air for a minimum of 3 weeks prior to use in adherence assays to ascertain proper cellular differentiation and the development of functional cilia.…”

Cilia Dysfunction in Lung Disease

“…Recurrent bronchitis is associated with loss of ciliated cells in children (154). A number of microorganisms impair cilia function by mechanisms including reducing ciliary beat frequency, disrupting ciliary coordination and inducing ciliary dyskinesia (155, 156). Some bacterial pathogens specifically target ciliated cells for adherence, including Actinobacillus pleuropneumonia , Pseudomonas aeruginosa , Moraxella catarrhalis , Mycoplasma pneumonia , Mycoplasma hyopneumoniae , and Bordatella species (155).…”

“…A number of microorganisms impair cilia function by mechanisms including reducing ciliary beat frequency, disrupting ciliary coordination and inducing ciliary dyskinesia (155, 156). Some bacterial pathogens specifically target ciliated cells for adherence, including Actinobacillus pleuropneumonia , Pseudomonas aeruginosa , Moraxella catarrhalis , Mycoplasma pneumonia , Mycoplasma hyopneumoniae , and Bordatella species (155). Epithelial samples from chronically infected patients with bronchiectasis show a disruption of ciliary orientation associated with decreased mucociliary clearance although cilia ultrastructure and ciliary beat frequency remain normal (157).…”

Antibodies against In Vivo -Expressed Antigens Are Sufficient To Protect against Lethal Aerosol Infection with Burkholderia mallei and Burkholderia pseudomallei

“…Given their important roles in pathogenicity, overall structure, and cellular location at the host-pathogen interface, autotransporter proteins (ATs) represent excellent targets for developing countermeasures (65)(66)(67)(68)(69)(70)(71)(72)(73)(74). These molecules form one of the largest families of virulence factors in Gram-negative bacteria and contribute a wide range of phenotypes, such as serum resistance, lipolytic activity, biofilms, and host cell adhesion (75)(76)(77)(78)(79). Thus, targeting ATs may impede the ability of pathogenic organisms to establish themselves in a host, persist, and cause disease.…”