Diminished ICAM-1 expression and impaired pulmonary clearance of nontypeable Haemophilus influenzae in a mouse model of chronic obstructive pulmonary disease/emphysema

Infect Immun. 2008 Nov;76(11):4959-67. doi: 10.1128/IAI.00664-08. Epub 2008 Sep 15.

Abstract

The airways of patients with chronic obstructive pulmonary disease (COPD) are continually colonized with bacterial opportunists like nontypeable Haemophilus influenzae (NTHi), and a wealth of evidence indicates that changes in bacterial populations within the lung can influence the severity of COPD. In this study, we used a murine model for COPD/emphysema to test the hypothesis that COPD affects pulmonary clearance. Mice were treated with a pulmonary bolus of elastase, and as reported previously, the lungs of these mice were pathologically similar to those with COPD/emphysema at approximately 1 month posttreatment. Pulmonary clearance of NTHi was significantly impaired in elastase-treated versus mock-treated mice. While histopathologic analysis revealed minimal differences in localized lung inflammation between the two groups, lower levels of intercellular adhesion molecule 1 (ICAM-1) were observed for the airway epithelial surface of elastase-treated mice than for those of control mice. Following infection, elastase-treated mice had lung pathology consistent with pneumonia for as long as 72 h postinfection, whereas at the same time point, mock-treated mice had cleared NTHi and showed little apparent pathology. Large aggregates of bacteria were observed within damaged lung tissue of the elastase-treated mice, whereas sparse individual bacteria were observed in lungs of mock-treated mice at the same time point postinfection. Additional infection studies showed that NTHi mutants with biofilm defects were less persistent in the elastase-treated mice than the parent strain. These findings establish a model for COPD-related infections and support the hypotheses that ICAM-1 promotes clearance of NTHi. Furthermore, the data indicate that NTHi may form biofilms within the context of COPD-related infections.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biofilms
  • Disease Models, Animal
  • Haemophilus Infections / etiology*
  • Haemophilus influenzae / immunology
  • Intercellular Adhesion Molecule-1 / biosynthesis*
  • Mice
  • Mucociliary Clearance / physiology*
  • Pulmonary Emphysema / complications*
  • Pulmonary Emphysema / microbiology*
  • Pulmonary Emphysema / physiopathology*

Substances

  • Intercellular Adhesion Molecule-1