Recombinant C fragment of botulinum neurotoxin B serotype (rBoNTB (HC)) immune response and protection in the rhesus monkey

Botulinum neurotoxin B (BoNTB) is a distinct protein subtype of a family of neurotoxins with the potential for use in biological warfare or terrorist attacks. This study is one in a series evaluating the immunogenicity and protective effects of recombinant vaccines against the different subtypes of botulinum toxin. The recombinant subunit vaccines encoding the C fragment portion (50 kDa) of the toxins are produced in the yeast, Pichia pastoris. In this study, groups of rhesus monkeys were vaccinated with three doses (1 and 5 μg per dose) of rBoNTB(H_c) vaccine. Total and neutralizing antibody titers were determined at various times during and postvaccination. Two groups of vaccinated monkeys plus non-vaccinated controls were actively challenged with B toxin by aerosol exposure. All monkeys receiving vaccine were protected from the toxin and no clinical signs of disease were observed, while controls displaying classic signs of botulism succumbed to the toxin challenge. Two additional groups of monkeys receiving the same vaccine regiment as the first two groups had significant levels of circulating neutralizing antibody titers up to 24 months postvaccination. This non-human primate study demonstrated the short- and long-term immunity afforded by the rBoNTB(H_c) vaccine.