title: Early-life chlamydial lung infection enhances allergic airways disease through age-dependent differences in immunopathology.
abstract: BACKGROUND
  Asthma typically originates in early-life, and the impact of infection during immunologic maturation is a critical factor in disease pathogenesis. The progression of aberrant T(H)2 cell responses and disease development has been attributed to a lack of infections. However, exposure to specific pathogens such as Chlamydia may alter immunologic programming and predispose to asthma.
  
  
  OBJECTIVE
  To investigate the effects of chlamydial infection at different ages on allergic airways disease in later life.
  
  
  METHODS
  Neonatal, infant, or adult BALB/c mice were infected and 6 weeks later were sensitized and subsequently challenged with ovalbumin. Hallmark features of allergic airways disease were compared with uninfected allergic and nonallergic controls.
  
  
  RESULTS
  Early-life (neonatal and infant) but not adult chlamydial infection enhanced the development of hallmark features of asthma in ovalbumin-induced allergic airways disease. Notably early-life infection increased mucus-secreting cell numbers, IL-13 expression, and airway hyperresponsiveness. Neonatal infection attenuated eosinophil influx and ovalbumin-specific T(H)2 cytokine release and numbers of activated myeloid dendritic cells (DCs) in lymph nodes. By contrast, infant infection augmented features of allergic inflammation with increased airway eosinophils, T(H)2 cytokine, and DC responses. Both neonatal and infant infection increased systemic DC-induced IL-13 release from CD4(+) T cells. The timing of infection had significant effects on lung structure because neonatal but not infant or adult infection induced increases in alveolar diameter.
  
  
  CONCLUSIONS
  Early-life respiratory chlamydial infections modulate immune responses, alter lung function and structure, and enhance the severity of allergic airways disease in later life.
authors.affiliation: Centre for Asthma and Respiratory Disease and Hunter Medical Research Institute, University of Newcastle, Newcastle, Australia.
authors.forename: Jay C
authors.initials: JC
authors.lastname: Horvat
authors.forename: Malcolm R
authors.initials: MR
authors.lastname: Starkey
authors.forename: Richard Y
authors.initials: RY
authors.lastname: Kim
authors.forename: Simon
authors.initials: S
authors.lastname: Phipps
authors.forename: Peter G
authors.initials: PG
authors.lastname: Gibson
authors.forename: Kenneth W
authors.initials: KW
authors.lastname: Beagley
authors.forename: Paul S
authors.initials: PS
authors.lastname: Foster
authors.forename: Philip M
authors.initials: PM
authors.lastname: Hansbro
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001249:Asthma / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D016535:Bronchial Hyperreactivity / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D002469:Cell Separation; D002690:Chlamydia Infections / Q000150:complications / Q000276:immunology*; D016207:Cytokines / Q000276:immunology; D003713:Dendritic Cells / Q000276:immunology; D004804:Eosinophils / Q000276:immunology; D005434:Flow Cytometry; D006967:Hypersensitivity / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D018793:Interleukin-13 / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018418:Th2 Cells / Q000276:immunology
chemical_list: D016207:Cytokines; D018793:Interleukin-13