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Research Project: Exploration of Novel repRNA Vaccine Candidates for Rift Valley Fever Virus

Location: Foreign Arthropod Borne Animal Disease Research

Project Number: 3022-32000-024-016-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2023
End Date: Aug 31, 2025

Rift Valley Fever virus (RVFV) represents a significant zoonotic threat to the United States and there are no approved RVFV vaccines for domestic use in cattle, sheep, or goats, the key amplifying host of the virus. Further, emerging genotypes of RVFV and expansion of their geographic range warrant the development of new vaccines that can protect against all RVFV genotypes. The development of these vaccines will aid in control measures of RVFV to prevent amplification of RVFV in cattle, sheep, and goats. The cooperator has developed a self-amplifying replicon RNA (repRNA) vaccine platform delivered by a Lipid InOrganic Nanoparticle (LION) that is currently being evaluated in an ongoing phase III clinical trial in India, an ongoing phase I trial in South Korea, and with additional trials pending in the Philippines, Brazil, and the United States to evaluate safety and immunogenicity of our COVID-19 vaccine. In contrast to lipid nanoparticle-formulated RNA approaches, our approach uncouples the RNA and formulation processes so that each can be manufactured and stored separately where the final drug product is prepared at the bedside by simple mixing of the two components LION and repRNA, as separate products, can be stored long-term at 4°C and -20°C, respectively, enabling simplified distribution and stockpiling. Furthermore, updates to the repRNA product do not necessitate additional manufacturing of LION, allowing for mixing/matching to facilitate rapid response to emerging pandemics. This drug product presentation is highly amenable to the prototype approach proposed here, where target-specific vaccines can be manufactured as different RNA products, and simply combined at the pharmacy or vaccination site with LION. This would eliminate the need for an additional encapsulation manufacturing process currently required for lipid nanoparticle-based formulations, reducing both the time and cost of manufacturing and allowing for a simplified distribution plan where LION can be locally stockpiled. We have made both repRNA and LION drug products under current good manufacturing practice (cGMP) regulations and, having demonstrated safety and immunogenicity in animals and humans, we have laid the necessary groundwork to facilitate rapid translation of vaccine candidates for other indications into the clinic or for agricultural practice, such as for the prevention of RVFV infection. To improve stability of repRNA vaccines, we are currently developing lyophilization processes as well as optimizing delivery of DNA-launched repRNA (repDNA) vaccines. Here we propose to advance the development of repDNA as a stable formulation for agricultural applications. The objectives of this collaboration are to create novel vaccine candidates for each RVFV genotype and evaluate their immunogenicity, through development of RVFV repRNA vaccines. The following objectives are anticipated for this project: 1. Design of repRNA and repDNA vaccine candidates against Rift Valley Fever 2. Evaluation of immunogenicity in mice

1. Vaccine candidate design 1.1. Synthesis and cloning of prM-E repRNA and repDNA constructs 1.2. Qualification of RNA substance 1.3. Characterization of protein expression in vitro 1.4. Characterization of innate immune response to vaccine candidates in vitro 2. Murine immunogenicity 2.1. Assay development 2.1.1. Cloning and rescue of VSV-RVFV recombinant virus 2.1.2. Development of cell impedance-based neutralization assay 2.1.3. Development of mouse and pig ELISAs 2.1.4. Development of mouse splenocyte ELISPOT assays 2.2. repRNA/LION 2.2.1. Vaccine candidate screen 2.2.2. Dose titration of top two vaccine candidates 2.2.3. Durability of prime-only and prime/boost of lead vaccine candidate 2.3. repDNA/pharmajet 2.3.1. Formulation optimization for pharmajet delivery of repDNA 2.3.2. Comparison of tropis and stratis delivery of repDNA in mice 2.3.3. Comparison of lead pharmajet/repDNA and LION/repRNA