No abstract

No abstract

A B S T R A C T Gonococcal pili facilitate attachment of virulent Neisseria gonorrhoeae to human cells. To characterize this attachment function, purified gonococcal pili isolated from four strains possessing antigenically distinct pili were radiolabeled with 125I and used to measure the attachment of pili to various human cells in vitro. Human buccal and cervical-vaginal mucosal epithelial cells, fallopian tube mucosa, and sperm bound pili in greater numbers per ,um2 of surface area (1-10) than fetal tonsil fibroblasts, HeLa M cells, erythrocytes, or polymorphonuclear leukocytes. This cell specificity of attachment suggests a greater density of membrane pili binding sites on cells similar or identical to cells from natural sites of infection. The pili binding sites were quantitated as 1 x 104 per cervical-vaginal squamous cell.Pili of all antigenic types attached equally to a given cell type, implying that the attachment moiety of each pilus was similar.Attachment of gonococcal pili to human cells occurred quickly with saturation of presumed receptor sites within 20-60 min. Attachment was temperature dependent (370 > 20°> 4°C), and pH dependent (3.5 < 4.5 > 5.5 > 7.5). Attachment was inhibited by antibody to pili (homologous pili Ab > heterologous Ab). The extent of possible protection against gonococcal infection due to inhibition of pili-mediated attachment might prove limited as a result of the considerable antigenic heterogeneity among pili and the observation that blockage of pili attachment is maximal only with antibody to pili of the infecting strain. INTRODUCTIONThe pili (fimbriae) of Neisseria gonorrhoeae presumably mediate the attachment of the gonococcus to human tissues. Previous evidence for an attachment role of pili has relied on the use of whole gonococci whose attachment to human cells was enhanced or occurred exclusively when that organism was piliated (1)(2)(3)(4)(5)(6)(7)(8). Swanson (1) has reported that the presence of pili afford gonococci enhanced attachment to human amnion cells in vitro. The adherence of gonococci to human buccal mucosal cells (2), ecto-and endocervical epithelium, and fallopian tube mucosa (3), as well as exfoliated vaginal (4) and urothelial cells (5) is also enhanced by piliation. James-Holmquist et al. (6, 7) further implicated an attachment role of pili by demonstrating that antibody to purified gonococcal pili blocked the enhanced attachment of piliated gonococci to human sperm. The human fallopian tube has been used in perfusion culture by Ward et al. (8) to provide scanning electron microscope evidence of pili anchoring gonococci to the epithelial surface. The agglutination of human erythrocytes by the gonococcus has been correlated with the presence of pili by several investigators (2, 9-12). Recently, purified pili alone have been shown to be capable of direct erythrocyte agglutination (12). This agglutination can be blocked by antiserum to these purified pili, and the blockage reflects the antigenic heterogeneity of gonococcal pili (12).For the gonococcus,...

Isolated pure gonococcal pili were found capable of producing direct agglutination of human erythrocytes. Four different strains of gonococci were compared, and hemagglutination was produced by isolated pili or piliated gonococci but not by nonpiliated gonococci of each strain. Pili from each of the four strains were antigenically distinguishable using antisera specific for pili to agglutinate piliated gonococci, form precipitin lines in Ouchterlony immunodiffusion, or inhibit hemagglutination caused by purified pili or piliated gonococci. However, these tests also demonstrate some shared antigenicity among pili. Shared antigens among the four pili types were quantitated at less than or equal to 2.5% by radioimmunoassay. Inhibition of hemagglutination was most marked with antiserum to the homologous pili type. Inhibition of hemagglutination by antiserum to heterologous pili suggested that shared antigens on pili from B and 2686 strains of gonococci are located near the erythrocyte attachment moiety of B strain pili and removed from the attachment moiety of 2686 strain pili. These results suggest that antigenic heterogeneity of pili will prove an important factor in any efforts to use pili as a vaccine for gonorrhea.