Antiidiotypic DNA vaccination induces serum bactericidal activity and protection against group B meningococci

• Published in: The Journal of experimental medicine Vol. 203; no. 1; pp. 111 - 118
• Main Authors: Beninati, Concetta, Midiri, Angelina, Mancuso, Giuseppe, Biondo, Carmelo, Arigò, Milena, Gerace, Elisabetta, Papasergi, Salvatore, Gambuzza, Maria, Boretti, Mauro, Magliani, Walter, Conti, Stefania, Polonelli, Luciano, Teti, Giuseppe
• Format: Journal Article
• Language: English
• Published: United States The Rockefeller University Press 23.01.2006
• Subjects: Animals; Animals, Newborn; Antibodies, Bacterial - immunology; Bacterial Vaccines; Blood Bactericidal Activity; Cercopithecus aethiops; COS Cells; Immunoglobulin Variable Region - immunology; Meningococcal Infections - immunology; Meningococcal Infections - prevention & control; Mice; Mice, Inbred BALB C; Neisseria meningitidis; Neisseria meningitidis, Serogroup B - immunology; Neisseria meningitidis, Serogroup B - pathogenicity; Rats; Rats, Wistar; Vaccines, DNA
• ISSN: 0022-1007; 1540-9538; 1892-1007
• DOI: 10.1084/jem.20051540

No vaccine is available for preventing infections by serogroup B Neisseria meningitidis (MenB), which accounts for a major portion of meningococcal cases in developed countries, because of the poor immunogenicity of the capsular polysaccharide (CP) even after protein conjugation. We have previously induced anticapsular antibodies by immunization with a single chain variable fragment (scFv), which mimics a protective CP epitope. This surrogate antigen, however, was ineffective at inducing serum bactericidal activity, an accepted marker of protection in humans. Serum bactericidal activity was consistently achieved by immunizing mice with the scFv-encoding gene. Immunization with vectors without a secretory signal sequence before the scFv resulted in markedly higher bactericidal activity relative to those with such a sequence. The induced antibodies were capsule specific, as shown by complete inhibition of bactericidal activity by purified MenB CP and by resistance to killing of MenA or MenC. Moreover, these antibodies were predominantly of the IgG2a isotype, reflecting a T helper type 1 response. Administration of sera from scFv gene-vaccinated animals protected infant rats against MenB bacteremia. These data illustrate the potential of vaccination with genes encoding capsular mimics in providing protection against MenB and other encapsulated bacteria.