CD46-Independent Binding of Neisserial Type IV Pili and the Major Pilus Adhesin, PilC, to Human Epithelial Cells

Abstract

Neisseria gonorrhoeae is a gram-negative bacterial pathogen which infects the human mucosal epithelium. An early critical event in neisserial infection is the type IV pilus-mediated adherence to the host cell. The PilC protein, located on the pilus tip, has earlier been identified as the major pilus adhesin. Previous studies suggested that the cell surface protein CD46 is a pilus receptor for Neisseria. We investigated the role of CD46 in pilus-mediated gonococcal infection of epithelial cells. Differences in binding efficiencies of piliated gonococci as well as purified pilus adhesin PilC2 on human epithelial cell lines did not correlate to the level of surface-expressed CD46. Additionally, no binding of piliated gonococci or PilC2 protein was observed on CD46-transfected CHO and MDCK cells. Furthermore, specific down-regulation of CD46 expression in human epithelial cell lines by RNA interference did not alter the binding efficiency of piliated gonococci or purified PilC2 protein, although other CD46-dependent processes, such as measles virus infection and C3b cleavage, were significantly reduced. These data support the notion that pilus-mediated gonococcal infection of epithelial cells can occur in a CD46-independent manner, thus questioning the function of CD46 as an essential pilus receptor for pathogenic neisseriae.

Monoclonal Antibody Detection of CD46 Clustering beneath Neisseria gonorrhoeae Microcolonies

“…Our study does not directly address this issue but does show that CD46 can cluster beneath adherent neisseriae. A recent study by Kirchner et al did not detect CD46 clustering upon N. gonorrhoeae infection of epithelial cells (19). The primary difference between our study and theirs was the difference in infection times (3 h versus 90 min).…”

“…CD46 levels in several cell lines do not correlate with the level of binding by piliated N. gonorrhoeae or PilC, the major adhesin of type IV pili (19,44). Our study does not directly address this issue but does show that CD46 can cluster beneath adherent neisseriae.…”

Type IV Pilin Proteins: Versatile Molecular Modules

“…The major pilin from Neisseria, PilE, was reported to hemagglutinate erythrocytes (351) and to mediate binding to host proteins on endothelial cells (110). The receptor for Neisseria pili was proposed to be CD46 (214,413), although newer evidence suggests otherwise (224).…”

Humanized Mouse Model to Study Bacterial Infections Targeting the Microvasculature

“…CD46 was suggested to be the Tfp receptor and transgenic animals were produced to act as mouse models. However, infection in these animals does not lead to extensive infection or to rash development 12,13 . Other animal models that have been described for the bacteremia aspect of Neisseria infection take into account the bacterial preference for human transferrin as an iron source 14,15 .…”