The goal of this application is to develop a multicomponent anthrax vaccine that can be easily administered, induces Iong-lasting high antibody titers, and provides protection against Bacillus anthracis infection. Three novel platform technologies, needle-free skin patch transcutaneous immunization (TCI), phage T4 multicomponent display, and liposome and emulsion adjuvant formulations, will be brought to bear on developing an efficacious anthrax vaccine. The research wilt be carried out by two complementary laboratories, one highly skilled in the genetics and manufacture of T4 bacteriophage particles and expression of proteins on the surface of T4, and the other with broad experience with TCI, immunogenic liposomes, emulsions, vaccine formulations, and vaccine clinical trials, in close collaboration with a third laboratory that is a leader in anthrax toxin biology and production. Mutant forms of all three anthrax toxin components, protective antigen (PA), lethal factor (LF) and edema factor (EF), will be expressed either as individual proteins or as N-terminal fusions of the highly antigenic outer capsid protein (Hoc) of bacteriophage T4. The toxin-Hoc fusion proteins with an N-terminal hexa-histidine tag will be purified in large quantities and loaded onto the phage T4 icosahedral surface using an in vitro assembly system. The TCI and intramuscular (IM) routes of delivery for combinations of soluble proteins or T4 displayed antigens with liposome and emulsion adjuvant formulations will be evaluated in parallel tracks, using the mouse model, for generation of protective antibody titers. The immunized mice will be challenged with (i) anthrax toxin, (ii) Sterne strain, and (iii) Ames strain, to determine the efficacy of the vaccines. The best combinations that induce protection in mice against challenge with virulent Bacillus anthracis will be tested in a guinea pig model. Immune responses will be characterized, and challenge experiments with the virulent anthrax strain will be performed to select the best vaccine product(s) that induce long-lasting immunity. The most promising anthrax vaccine candidates will be tested in a nonhuman primate model, in addition to characterization of immune responses, the immunized macaques will be challenged with the aerosolized spores of Bacillus anthracis. The duration of protection as well as pathological changes will be assessed.
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