PAGE Type , and Source of the Isolates Used in These Studies Meningococcalisolate Serogroup

The recognition that attachment of pathogenic Neisseria to human mucosal surfaces involves specific interactions between polymeric filaments called pili and host cell receptors (1-4) has suggested new approaches to the immunoprophylaxis of meningococcal and gonococcal disease. Pili are present on meningococci and gonococci isolated from human mucosal surfaces (3, 4) and are found on meningococci after tissue invasion (5). In vitro studies indicate that pili facilitate the attachment of meningococci and gonococci to human cells and to human mucosa in organ culture (6, 7). Piliation is also correlated with resistance of gonococci to phagocytosis by human polymorphonuclear leukocytes (8). Antibodies to pili are detected after fulminant meningococcal disease (9) and in sera and mucosal secretions after natural gonococcal infection (10). These antibodies may block attachment of pathogenic Neisseria to human mucosal surfaces (11). However, gonococcal pili are remarkable for their antigenic diversity (12), and different pili types may occur on meningococci (13). Antibody directed at one pilus serotype may have limited potential for blocking pilus function of heterologous serotypes. Recently (14), a parenteral pilus vaccine composed of a single pilus type was found to be ineffective in preventing gonorrhea caused by a broad range of gonococcal strains. An alternative approach to an efficacious pilus vaccine is based on the observation that gonococcal pili have structurally conserved immunorecessive regions that encompass a common receptor-binding domain, and immunodominant, structurally variable regions that determine serotype specificity (15, 16). A vaccine containing an immunogenic pilus peptide encompassing the conserved region might elicit an antibody that binds all gonococcal pill and blocks their pathogenic function (15, 16). Because pili are also the most important surface components mediating attachment of meningococci (2, 3) and because of the close genetic relationship of meningococci and gonococci (17), more detailed information was sought concerning the nature of meningococcal pili and the structural and antigenic relationships between menin-