Chlamydia pneumoniae and chronic asthma: Updated systematic review and meta-analysis of population attributable risk

PLoS One. 2021 Apr 19;16(4):e0250034. doi: 10.1371/journal.pone.0250034. eCollection 2021.

Abstract

Background: Chlamydia pneumoniae (Cp) is an obligate intracellular human respiratory pathogen producing persisting lung infection with a plausible link to asthma pathogenesis. The population attributable risk of potentially treatable Cp infection in asthma has not been reported.

Methods: The author searched from 2000 to 2020 inclusive for previously un-reviewed and new cross sectional and prospective controlled studies of Cp biomarkers and chronic asthma in both children and adults. Qualitative descriptive results and quantitative estimates of population attributable risk for selected biomarkers (specific IgG, IgA and IgE) are presented.

Findings: No large, long-term prospective population-based studies of Cp infection and asthma were identified. About half of case-control studies reported one or more significant associations of Cp biomarkers and chronic asthma. Heterogeneity of results by age group (pediatric v adult asthma), severity category (severe/uncontrolled, moderate/partly controlled, mild/controlled) and antibody isotype (specific IgG, IgA, IgE) were suggested by the qualitative results and confirmed by meta-analyses. The population attributable risks for Cp-specific IgG and IgA were nul in children and were 6% (95% confidence interval 2%-10%, p = 0.002) and 13% (9%-18%, p<0.00001) respectively in adults. In contrast to the nul or small population attributable risks for Cp-specific IgG and IgA, the population attributable risk for C. pneumoniae-specific IgE (children and adults combined) was 47% (39%-55%, p<0.00001). In the subset of studies that reported on asthma severity categories, Cp biomarkers were positively and significantly (P<0.00001) associated with asthma severity.

Interpretation: C. pneumoniae-specific IgE is strongly associated with asthma and asthma severity, suggesting a possible mechanism linking chronic Cp infection with asthma in a subset of individuals with asthma. Infection biomarkers should be included in future macrolide treatment trials for severe and uncontrolled asthma.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Asthma / etiology*
  • Asthma / microbiology*
  • Asthma / physiopathology
  • Biomarkers
  • Case-Control Studies
  • Chlamydia Infections / epidemiology
  • Chlamydophila Infections / complications
  • Chlamydophila Infections / epidemiology
  • Chlamydophila pneumoniae / pathogenicity*
  • Chronic Disease
  • Cross-Sectional Studies
  • Humans
  • Prospective Studies
  • Respiratory Tract Infections / epidemiology
  • Risk Factors

Substances

  • Biomarkers

Grants and funding

The author received no specific funding for this work.