Chlamydia pneumoniae, asthma, and COPD: what is the evidence?

Learning objectives: Reading this article will familiarize the reader with (1) the unique chlamydial intracellular life cycle and the propensity for h uman chlamydial infections to become persistent and to result in immunopath ologic (inflammatory) damage in target organs and (2) current evidence link ing Chlamydia pneumoniae (Cpn) infection to obstructive lung diseases (asth ma and chronic obstructive pulmonary disease, COPD). Potential therapeutic implications of the Cpn-asthma association are also discussed. Data sources: All Medline articles (January 1985 to March 1999) that cross- referenced the exploded MESH headings "lung diseases, obstructive" and "Chl amydia pneumoniae" (N = 76). Additional referenced articles, published abst racts, book chapters, and conference proceedings were also utilized. Study selection: (1) Case reports and case series that identified Cpn infec tion in asthma and/or COPD and (2) epidemiologic studies of markers for Cpn infection in asthma and/or COPD that included one or more control groups. Results: Of 18 controlled epidemiologic studies lover 4000 cases/controls), 15 found significant associations between Cpn infection and asthma using o rganism detection (polymerase chain reaction (PCR) testing (n = 2 studies) or fluorescent antigen testing (n = 1)), Cpn-specific secretory IgA (sIgA) antibody testing (n = 1), and/or specific serum IgE (n = 2), IgA (n = 4), I gG (n = 3) or other antibody criteria (n = 7). Eight case reports and 13 ca se series of Cpn infection in asthma lover 100 patients) also include descr iptions of improvement or complete disappearance of asthma symptoms after p rolonged antibiotic therapy directed against Cpn. Significant associations with COPD lover 1000 cases/controls) were reported in 5 of 6 studies. Resul ts of treating chronic chlamydial infections in COPD patients have not been reported. Conclusions: Although the full clinical significance of these Cpn-obstructi ve lung disease associations remains to be established, reports of asthma i mprovement after treatment of Cpn infection deserve further investigation. Clinicians who manage asthma should be aware of this information since it m ay help to manage difficult cases. The hypothesis that Cpn infection in COP D can amplify smoking associated inflammation and worsen fixed obstruction also deserves further study.