Rat model of chronic lung infections caused by non-typable Haemophilus influenzae.

Patients with chronic obstructive pulmonary disease (COPD) often have chronic or recurrent pulmonary infections with non-typable Haemophilus influenzae. A model of these infections exploited agar bead vehicles to protect the inoculum from rapid clearance, and a chronic lung infection of at least 42 days duration was established in rats. This infection induced increases in serum IgG titres to outer-membrane (OM) and lipo-oligosaccharide (LOS) antigens; immunoblotting demonstrated that this humoral response was directed partly against the outer-membrane proteins (OMPs). Lung lavage fluid also contained an increased titre of IgG antibodies to OM and LOS 42 days after infection. Antibodies produced during infection with one strain of H. influenzae cross-reacted with OMPs from another, non-typable H. influenzae strain. Despite their encasement in agar beads, pulmonary H. influenzae remained susceptible to amoxycillin. This model of chronic pulmonary infections due to non-typable H. influenzae appears to resemble the situation in COPD patients and may be useful for experimental therapeutic studies.