ADHERENCE OF NONTYPABLE HAEMOPHILUS-INFLUENZAE PROMOTES REORGANIZATION OF THE ACTIN CYTOSKELETON IN HUMAN OR CHINCHILLA EPITHELIAL-CELLS IN-VITRO

Non-typeable Haemophilus influenzae (NTHi) are opportunistic mucosal p athogens which adhere to epithelial cells via a variety of non-specifi c and specific interactions. Several adhesins have been identified and while the complimentary receptor(s) for each of these adhesins has no t yet been fully characterized, it is widely accepted that adherence i s an absolute prerequisite for disease. Several reports have indicated that NTHi can also be internalized and reside intracellularly. For th is to occur, NTHi must be taken up by mucosal epithelial cells lining the respiratory tract. We have noted, by TEM, that adherent NTHi overl ie an electron dense area in the cell membrane of human epithelial cel ls which is associated with a localized complex assembly of cytoskelet al fibers in the eukaryotic cytoplasm. We thus examined the potential involvement of cytoskeletal actin in this phenomenon via FITC-phalloid in labeling of respiratory tract epithelial cells which had been incub ated with several clinical isolates of NTHi. Strong punctate fluoresce nce was coincident with adherent NTHi to both human oropharyngeal and chinchilla middle ear epithelial cells. This reactivity was similar to the discrete fluorescent spots observed with enteropathogenic Escheri chia coli which were adhered to HeLa cells. In contrast, none of the N THi isolates tested induced actin polymerization in cells of endotheli al origin. While the exact mechanisms involved are yet to be elucidate d, our data indicated that actin nucleation was coincident with NTHi a dherence. (C) 1997 Academic Press Limited.