Abstract
Pseudomonas aeruginosa is the most important bacterial pathogen associated with chronic airway infection, especially in cystic fibrosis. We addressed the question of whether the galactophilic internal lectin of P. aeruginosa (PA-I) could represent a virulence factor for the respiratory epithelium. PA-I lectin was localized in all the bacteria of P. aeruginosa ATCC 33347 as determined by immunofluorescence staining. We investigated the dose-dependent effect of P. aeruginosa PA-I lectin on the growth, the ciliary beating frequency, and the morphology of human respiratory cells in primary culture of nasal polyps collected from non-cystic fibrosis patients. PA-I lectin significantly (P < 0.01) inhibited the growth of respiratory cells at a concentration of > or = 10 micrograms/ml. The percentage of active ciliated cell surface of the cultures decreased significantly (P < 0.05) at a PA-I lectin concentration of 50 micrograms/ml. Exposed to a low concentration of PA-I lectin (10 micrograms/ml), respiratory epithelial cells showed intracytoplasmic vacuoles when examined by light and transmission electron microscopy. At a higher concentration of PA-I lectin (100 micrograms/ml), major cell damage and severe epithelial shedding occurred. These results demonstrate that the P. aeruginosa internal PA-I lectin has a dose-dependent cytotoxic effect on respiratory epithelial cells in vitro. The P. aeruginosa PA-I lectin may represent a virulence factor by contributing to the respiratory epithelial damage during P. aeruginosa respiratory infections.