Interleukin-8 Production by Human Airway Epithelial Cells in Response to Pseudomonas aeruginosa Clinical Isolates Expressing Type a or Type b Flagellins

Pseudomonas aeruginosa lung infection is a major cause of morbidity and mortality worldwide. P. aeruginosa flagellin, the main structural protein of the flagellar filament, is a virulence factor with proinflammatory activity on respiratory epithelial cells. P. aeruginosa bacteria express one of two isoforms of flagellin (type a or b) that differ in their primary amino acid sequences as well as in posttranslational glycosylation. In this study, the distribution of type a and b flagellins among 3 P. aeruginosa laboratory strains and 14 clinical isolates (1 ulcerative keratitis, 3 cystic fibrosis, and 10 acute pneumonia isolates) was determined, and their abilities to stimulate interleukin-8 (IL-8) production by human airway epithelial cells was compared. By comparison with the PAK (type a) and PAO1 (type b) prototype laboratory strains, 10/14 (71.4%) of clinical isolates expressed type a and 4/14 (28.6%) expressed type b flagellins. Among four cell lines surveyed, BEAS-2B cells were found to give the greatest difference between constitutive and flagellin-stimulated IL-8 production. All 17 flagellins stimulated IL-8 production by BEAS-2B cells (range, 700 to 4,000 pg/ml). However, no discernible differences in IL-8 production were evident when comparing type a versus type b flagellins or flagellins from laboratory versus clinical strains or among the clinical strains.