A Novel Strategy for Generating Safe and Effective Flavivirus Vaccines

The recent emergence and devastating impact of Zika virus (ZIKV) clearly demonstrates that arboviral emergence continues to defy accurate prediction and exposes our inability to rapidly respond to and control outbreaks. The medical and veterinary importance of emerging flaviviruses is significantly exacerbated by the absence of available vaccines, therapeutics, and reliable control measures. Vaccination remains the most reliable strategy for outbreak prevention and control, but vaccine development intrinsically involves trade-offs between safety and immunogenicity. This study will develop a platform to overcome these trade-offs by combining the safety advantages of non-replicating platforms with the rapid and long-lived immunogenicity of a live-attenuated vaccine. We have developed a unique chimeric virus platform based on a novel insect-specific flavivirus (ISFV), Aripo virus (ARPV). Preliminary data shows ARPV’s host restriction is noticeably later in the replication cycle than described for other ISFVs and is capable of entering vertebrate cells and developing a robust immune response in the absence of genomic replication. An ARPV/ZIKV chimera was developed to test our hypothesis that ARPV/ZIKV vaccination produces a rapid and robust innate, humoral, and cell-mediated immune response that elicits sterilizing immunity against subsequent ZIKV challenge. Preliminary studies show a single dose of ARPV/ZIKV produces a robust adaptive ZIKV-specific immune response that completely protects mice from viremia, weight loss, and mortality, while demonstrating exceptional safety in vivo. This platform is superior because of the increased safety of the chimera by virtue of its fundamental replication defect in vertebrate cells, increased immunogenicity due to a lack of inactivation requirements, and efficient genome delivery to target cells. This innovative and essential R01 aims to evaluate the safety profile, protective efficacy and mechanisms underlying the immunogenicity of ARPV/ZIKV vaccination via three aims: 1. Determine the efficacy of ARPV/ZIKV immunization for preventing ZIKV-induced disease in murine and rhesus macaque models. 2. Elucidate the correlates underlying vaccine-induced protection from ZIKV-induced disease in ARPV/ZIKV vaccinated murine models. 3. Evaluate the safety profile of this vaccine candidate in vitro and in vivo, and elucidate the mechanism underlying its immunogenicity. This study will generate a safe, efficacious, single-dose ZIKV vaccine that will be ideally suited to affordably control explosive outbreaks, which typically affect resource-limited regions. Our platform’s antigenic superiority will result in enhanced efficacy, effectively combining the safety of replication-defective virus-like particles or nucleic acid vaccines with the antigenic superiority, and rapid, long-lived immunogenicity of live-attenuated vaccines. This platform can also be readily translated to other flaviviruses of human or veterinary importance.