Alphavirus Replicon Vaccines against Botulinum Neurotox*

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DESCRIPTION (provided by applicant): The objectives of the proposed research are to construct alphavirus replicon particle vaccines directed against all seven serotypes of botulinum neurotoxin (BoNT); perform in vitro evaluations and preclinical animal studies of these vaccines; perform production scale-up and GMP manufacture of a bivalent vaccine against BoNT (serotypes A and B), prepare and submit an Investigational New Drug (IND) application, and perform a phase I clinical trial. BoNT is highly lethal by the aerosol route and is a credible and significant bioterrorist threat. Existing investigational vaccines have significant shortcomings. We propose a novel approach, using a propagation-defective, single cycle, RNA replicon vector system, derived from an attenuated strain of Venezuelan equine encephalitis (VEE) virus, to produce virus-like replicon particles (VRP) expressing the carboxy-terminal half of the heavy chain (Hc) of all serotypes of BoNT. Preliminary animal studies have demonstrated the safety and feasibility of this approach, as both monovalent and bivalent VRP vaccines induced neutralizing antibody responses against the expressed BoNT Hc that conferred long-term protection against challenge with homologous toxin. The project will include seven specific aims. (1) Construct VRP vaccines expressing Hc fragments of all seven BoNT serotypes. (2) Perform in vitro characterization of these vaccines. (3) Evaluate preclinical safety, immunogenicity and efficacy in murine challenge models. (4) Perform scale-up development of processes for GMP-compliant manufacture of a bivalent (serotypes A and B) BoNT Hc fragment VRP vaccine selected for clinical evaluation. (5) Perform GMP manufacture of this vaccine. (6) Perform benchmark preclinical studies and prepare an IND. (7) Conduct a phase 1 clinical trial. To achieve these aims, human codon-optimized genes for BoNT Hc will be inserted into VEE replicon vectors. Using a novel DNA helper system that precludes replicon/helper recombination, the replicon RNAs will be packaged into VRP with a VEE glycoprotein coat that confers dendritic cell tropism. Safety, immunogenicity and efficacy will be evaluated using established animal models. Process scale-up, GMP manufacture, preclinical and clinical testing will be performed based on previous experience with a VRP vaccine for HIV. Results of these studies will provide the basis for future clinical trials of a comprehensive 7-valent BoNT Hc fragment VRP vaccine.