NEISSERIA PILC PROTEIN IDENTIFIED AS TYPE-4 PILUS TIP LOCATED ADHESIN

TYPE-4 pilus-mediated adherence of Neisseria gonorrhoeae and Neisseria meningitidis is considered to be a crucial early event in neisserial infections(1,2). In addition to the principal pilus subunit (pilin or PilE), both pathogens produce low quantities of a phase-variable PilC protein which is implicated in pilus biogenesis and pilus-mediated epi thelial cell adherence(3,4). The identity, however, of the pilus adhes in has remained obscure(4,5). Here we describe the isolation of a PilC protein from a gonococcal overproducing strain and demonstrate its sp ecific interaction with human epithelial cells. Our results are consis tent with the cell and species tropisms of neisserial infections. Bind ing of PilC effectively competes with pilus-mediated, but not Opa-medi ated(6), attachment of N. gonorrhoeae and of N. meningitidis, indicati ng that both pathogens interact with identical or very similar epithel ial cell receptors. Immunogold electron microscopy using antisera rais ed against purified PilC and synthetic peptides locates PilC at the ti p of gonococcal pill. PilC thus represents an essential pilus-associat ed adhesin, providing a rationale for selective protection against nei sserial infections.