Non-typeable Haemophilus influenzae adhere to and invade human bronchial epithelial cells via an interaction of lipooligosaccharide with the PAF receptor

Adherence and invasion are thought to be key events in the pathogenesis of non-typeable Haemophilus influenzae (NTHi). The role of NTHi lipooligosacch aride (LOS) in adherence was examined using an LOS-coated polystyrene bead adherence assay. Beads coated with NTHi 2019 LOS adhered significantly more to 16HBE14 human bronchial epithelial cells than beads coated with truncat ed LOS isolated from an NTHi 2019 pgmB::erm(r) mutant (P = 0.037). Adherenc e was inhibited by preincubation of cell monolayers with NTHi 2019 LOS (P = 0.0009), but not by preincubation with NTHi 2019 pgmB::erm(r) LOS. Competi tive inhibition studies with a panel of compounds containing structures fou nd within NTHi LOS suggested that a phosphorylcholine (ChoP) moiety was inv olved in adherence. Further experiments revealed that mutations affecting t he oligosaccharide region of LOS or the incorporation of ChoP therein cause d significant decreases in the adherence to and invasion of bronchial cells by NTHi 2019 (P < 0.01). Analysis of infected monolayers by confocal micro scopy showed that ChoP(+) NTHi bacilli co-localized with the PAF receptor. Pretreatment of bronchial cells with a PAF receptor antagonist inhibited in vasion by NTHi 2109 and two other NTHi strains expressing ChoP(+) LOS glyco forms exhibiting high reactivity with an anti-ChoP antibody on colony immun oblots. These data suggest that a particular subset of ChoP(+) LOS glycofor ms could mediate NTHi invasion of bronchial cells by means of interaction w ith the PAF receptor.