SEQUENCE CHANGES IN THE PILUS SUBUNIT LEAD TO TROPISM VARIATION OF NEISSERIA-GONORRHOEAE TO HUMAN TISSUE

Pill of Neisseria gonorrhoeae are correlated with increased bacterial attachment to epithelial cells and undergo both phase and antigenic va riation. Phase variation of gonococcal pill can be brought about by re combination events in the pilin structural gene, pilE, or by the on/of f switch in expression of PilC, a pilus biogenesis protein for which t wo loci exist. We have studied the binding to epithelial cell lines an d to fixed tissue sections of N. gonorrhoeae MS11 derivatives and muta nts carrying structurally defined PilE and PilC proteins. In situ bind ing studies of N. gonorhoeae to formalin-fixed tissue sections resulte d in a binding pattern similar to that obtained using viable epithelia l cell lines of different origin. Piliated gonococcal clones, containi ng different pilE sequences, varied dramatically from one another in t heir efficiencies at binding to corneal and conjunctival tissue, but b ound equally well to cervical and endometrial tissues. Further, the bi nding data suggested that PilC expression by itself, i.e. without pill , cannot confer bacterial binding and that expression of either PilC1 or PilC2 does not confer different binding properties to the bacterial cells. Possible receptors for piliated gonococci were expressed in hu man tissues, such as cervix, endometrium, cornea, intestine, stomach, mid-brain and meninges, but not in human kidney. Pretreatment of the t arget tissues with Proteinase K decreased the gonococcal binding drama tically, whereas pretreatment with neuraminidase and meta-periodate, w hich cleave carbon-carbon linkages between vicinal hydroxyl groups in carbohydrates, did not affect attachment of gonococci. These data argu e that pilus-dependent attachment of N. gonorrhoeae to human tissue ma y be mediated by a eukaryotic receptor having protein characteristics, and that the pilus subunit sequence may play an important role in the interaction with human cornea.