Antiidiotypic DNA vaccination induces serum bactericidal activity and protection against group B meningococci.
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.
Beninati
Concetta
C
Dipartimento di Patologia e Microbiologia Sperimentale, Università degli Studi di Messina, I-98125 Messina, Italy.
Midiri
Angelina
A
Mancuso
Giuseppe
G
Biondo
Carmelo
C
Arigò
Milena
M
Gerace
Elisabetta
E
Papasergi
Salvatore
S
Gambuzza
Maria
M
Boretti
Mauro
M
Magliani
Walter
W
Conti
Stefania
S
Polonelli
Luciano
L
Teti
Giuseppe
G
D000818:Animals; D000831:Animals, Newborn; D000907:Antibodies, Bacterial / Q000276:immunology; D001428:Bacterial Vaccines; D001770:Blood Bactericidal Activity; D019556:COS Cells; D002522:Chlorocebus aethiops; D007135:Immunoglobulin Variable Region / Q000276:immunology; D008589:Meningococcal Infections / Q000276:immunology / Q000517:prevention & control*; D051379:Mice; D008807:Mice, Inbred BALB C; D038541:Neisseria meningitidis, Serogroup B / Q000276:immunology* / Q000472:pathogenicity; D051381:Rats; D017208:Rats, Wistar; D019444:Vaccines, DNA
D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D007135:Immunoglobulin Variable Region; D019444:Vaccines, DNA