The role of Mycoplasma pneumoniae in acute and chronic asthma remains elusive;however, multiple lines of evidence linking Mycoplasma to chronic asthma, exacerbations of asthma, and long-term decrements In pulmonary function suggest this organism may play an important role in asthma. The diagnosis of M. pneumoniae infection, however, is difficult because M. pneumoniae is a fastidious organism, capable of extracellular and intracellular parasitism/persistence, and therefore, microbiological growth directly from clinical specimens almost always fails. The diagnosis of active M. pneumoniae becomes even more difficult in states of chronic carriage where organism burdens would be significantly lower. Recently, our group identified a M. pneumoniae ADP-ribosylating/vacuolating toxin known as the Community Acquired Respiratory Distress Syndrome Toxin (CARDS TX) and created a PCR probe (MPN372) specific for amplifying cards gene sequences. In a recent outbreak of Mycoplasma community-acquired pneumonia, the Centers for Disease Control and Prevention demonstrated that PCR to CARDS TX was the most sensitive assay tested. A major barrier for understanding the role of M. pneumoniae in asthma has been the relative absence of a sensitive method to detect M. pneumoniae and a failure to understand the specific immunomodulatory role of M. pneumoniae infection. Using sensitive PCR and antigen capture assays to detect CARDS TX, we have been able to demonstrate that 43.6% of adult subjects with acute exacerbations of asthma are positive to MPN372 by real-time PCR versus 11% of subjects admitted with non-asthmatic lung disease and 4% in normal healthy controls (p<.001 for acute asthma vs controls). Additionally, we have established a clinical research site to follow subjects with refractory asthma and found 30/62 subjects (48%) were PCR positive for CARDS TX, with 10% remaining persistently positive over a mean period of 10.3 months. Two thirds of these persistently positive subjects never mounted an IgG response to Mycoplasma (ELISA to either CARDS TX or PI adhesin). The Clinical Core will undertake a longitudinal study to collect samples on both CARDS TX +/- asthmatics as well as CARDS TX +/- healthy controls to establish the role of M. pneumoniae in asthma severity and control as well as the differences in the immunologic responses to M. pneumoniae in asthmatic subjects compared to healthy non-asthmatic controls.
The findings in this study will have a significant impact on our understanding of how M. pneumoniae impacts asthma severity and control. Since 10% of refractory asthmatics may be chronically infected with M. pneumoniae, interventions to eliminate M. pneumoniae or CARDS TX produced by M. pneumoniae has significant therapeutic implications.
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