Article

Persistence of Community-Acquired Respiratory Distress Syndrome Toxin-Producing Mycoplasma pneumoniae in Refractory Asthma

Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA.
Chest (Impact Factor: 7.13). 05/2011; 140(2):401-7. DOI: 10.1378/chest.11-0221
Source: PubMed

ABSTRACT The role of Mycoplasma pneumoniae (Mp) in the initiation and persistence of asthma remains elusive. Mp community-acquired respiratory distress syndrome toxin (CARDS Tx) is a unique virulence factor that induces an intense lymphocytic response and exacerbates asthma in animal models. We sought to determine the incidence of Mp infection and the presence of CARDS Tx in subjects with refractory asthma (RA).
We conducted a prospective observational study in 64 subjects with RA. Respiratory secretions (sputum, nasal lavage, and throat swab) and blood were analyzed for the presence of CARDS Tx and P1 adhesin (P1) DNA by polymerase chain reaction (PCR), and CARDS Tx by antigen capture. Serum IgM and IgG antibodies to CARDS Tx were determined by enzyme-linked immunosorbent assay (ELISA).
Thirty-three of 64 subjects (52%) tested positive for Mp: 29 of 33 by CARDS Tx vs 10 of 33 by P1 assays. Ten subjects followed longitudinally for up to 633 days tested persistently positive for Mp. There were no significant differences in Mp-specific IgG responses between Mp-positive and Mp-negative groups. Eight of 10 subjects who tested persistently positive failed to mount a substantial IgG response to CARDS Tx, and up to 8 weeks of clarithromycin failed to eradicate Mp in five subjects.
Subjects with RA may be chronically infected with Mp. PCR for CARDS Tx appears to be the most sensitive method of identifying Mp infection. Despite the persistence of Mp in subjects with RA, some subjects failed to mount an IgG response, and macrolide therapy was insufficient to eradicate Mp.

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    • "Mycoplasma pneumoniae is a common human bacterial pathogen that causes acute or chronic respiratory infections and is linked to a variety of extrapulmonary infections or sequelae [2], [9], [10]. Clinical associations of M. pneumoniae infection with asthma exacerbations are increasing as detection methods improve [5], [7], [11], [12], [13], [14], [15], but the molecular mechanisms by which M. pneumoniae worsens asthma in humans are not well understood. "
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    ABSTRACT: Mycoplasma pneumoniae causes a range of airway and extrapulmonary pathologies in humans. Clinically, M. pneumoniae is associated with acute exacerbations of human asthma and a worsening of experimentally induced asthma in mice. Recently, we demonstrated that Community Acquired Respiratory Distress Syndrome (CARDS) toxin, an ADP-ribosylating and vacuolating toxin synthesized by M. pneumoniae, is sufficient to induce an asthma-like disease in BALB/cJ mice. To test the potential of CARDS toxin to exacerbate preexisting asthma, we examined inflammatory responses to recombinant CARDS toxin in an ovalbumin (OVA) murine model of asthma. Differences in pulmonary inflammatory responses between treatment groups were analyzed by histology, cell differentials and changes in cytokine and chemokine concentrations. Additionally, assessments of airway hyperreactivity were evaluated through direct pulmonary function measurements. Analysis of histology revealed exaggerated cellular inflammation with a strong eosinophilic component in the CARDS toxin-treated group. Heightened T-helper type-2 inflammatory responses were evidenced by increased expression of IL-4, IL-13, CCL17 and CCL22 corresponding with increased airway hyperreactivity in the CARDS toxin-treated mice. These data demonstrate that CARDS toxin can be a causal factor in the worsening of experimental allergic asthma, highlighting the potential importance of CARDS toxin in the etiology and exacerbation of human asthma.
    PLoS ONE 07/2014; 9(7):e102613. DOI:10.1371/journal.pone.0102613 · 3.23 Impact Factor
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    • "experimental animals and is readily detectable in airway fluids (Kannan et al., 2010; 2011; 2012; Techasaensiri et al., 2010; Muir et al., 2011; Peters et al., 2011). Furthermore , purified recombinant CARDS toxin elicits multiple inflammatory and temporally changing histopathological patterns in rodents and primates in a manner similar to those observed during M. pneumoniae infection (Hardy et al., 2009). "
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    ABSTRACT: Community-acquired respiratory distress syndrome (CARDS) toxin from Mycoplasma pneumoniae is a 591 amino acid virulence factor with ADP-ribosyltransferase (ADPRT) and vacuolating activities. It is expressed at low levels during in vitro growth and at high levels during colonization of the lung. Exposure of experimental animals to purified recombinant CARDS toxin alone is sufficient to recapitulate the cytopathology and inflammatory responses associated with M. pneumoniae infection in humans and animals. Here, by molecular modeling, serial truncations and site-directed mutagenesis, we show that the N-terminal region is essential for ADP-ribosylating activity. Also, by systematic truncation and limited proteolysis experiments we identified a portion of the C-terminal region that mediates toxin binding to mammalian cell surfaces and subsequent internalization. In addition, the C-terminal region alone induces vacuolization in a manner similar to full-length toxin. Together, these data suggest that CARDS toxin has a unique architecture with functionally separable N-terminal and C-terminal domains.
    Molecular Microbiology 06/2014; 93(3). DOI:10.1111/mmi.12680 · 5.03 Impact Factor
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    • "M. pneumoniae poorly expresses CARDS toxin during in vitro growth but dramatically increases synthesis in vivo [15]. Using specific CARDS toxin assays, we detected and co-localized M. pneumoniae and CARDS toxin in biological fluids of infected animals and human tissue samples [16], [17], [18]. Also, we observed dramatic seroconversion to CARDS toxin in M. pneumoniae-associated pneumonia patients, further indicating that this toxin is synthesized in vivo and possesses highly immunogenic epitopes [11]. "
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    ABSTRACT: Bacterial toxins possess specific mechanisms of binding and uptake by mammalian cells. Mycoplasma pneumoniae CARDS (Community Acquired Respiratory Distress Syndrome) toxin is a 68 kDa protein, which demonstrates high binding affinity to human surfactant protein-A and exhibits specific biological activities including mono-ADP ribosylation and vacuolization. These properties lead to inflammatory processes in the airway and a range of cytopathologies including ciliostasis, loss of tissue integrity and injury, and cell death. However, the process by which CARDS toxin enters target cells is unknown. In this study, we show that CARDS toxin binds to mammalian cell surfaces and is internalized rapidly in a dose and time-dependent manner using a clathrin-mediated pathway, as indicated by inhibition of toxin internalization by monodansylcadaverine but not by methyl-β-cyclodextrin or filipin. Furthermore, the internalization of CARDS toxin was markedly inhibited in clathrin-depleted cells.
    PLoS ONE 05/2013; 8(5):e62706. DOI:10.1371/journal.pone.0062706 · 3.23 Impact Factor
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