A Novel T cell-based Vaccine to Prevent Dengue/Zika virus infection - Dengue virus (DENV) and Zika virus (ZIKV) are transmitted via Aedes mosquitos and can cause severe diseases such as Dengue hemorrhage fever (DHF) and Dengue shock syndrome (DSS) or Guillain-Barre syndrome and microcephaly. DENV has four serotypes which all have significant homology to ZIKV. Primary infection by DENV leads to life-long immunity to the infecting serotype, but not to other serotypes. Secondary infection by other serotypes is often associated with life-threatening complications, such as DHF and DSS. It is believed that the antibodies generated in the primary infection opsonize the secondary infection virus to target monocytes and macrophages via Fc-receptor-mediated endocytosis, leading to higher viral loads and severe disease pathology. This is known as antibody-dependent enhancement (ADE) of infection and has been confirmed in mouse models. Importantly, a DENV vaccine (Dengvaxia) expressing precursor membrane (prM) and envelope (E) proteins from 4 serotypes of DENV in DENV-uninfected children leads to more hospitalization care than in the infected ones (a possible consequence of ADE). Thus, there is an urgent need for a vaccine that prevents DENV/ZIKV infection without causing ADE. To address this problem, we designed a vaccine by targeting ZIKV non-structural protein 3 (NS3) without E and prM proteins and by using ubiquitin and gene rearrangement strategy to enhance its degradation in the proteasome with the goal of inducing only NS3- specific cytotoxic T lymphocytes (CTLs). Our data showed that the DNA vaccine greatly reduced viral titers in tissues and blood of the adult Ifnar1−/− mice challenged with ZIKV and all of the mice survived. The vaccine also remarkably reduced placenta tissue damage and levels of pro-inflammatory cytokines, and fully protected fetuses against ZIKV-induced damage. This protection required CD8+ CTLs. No ADE was detected in the vaccinated mice. To expand the protection spectrum, here we propose to develop a vaccine expressing ubiquitinated and rearranged ZIKV/DENV1-4 NS3 proteins. We expect that the vaccine will induce specific CTL responses with protection against ZIKV and DENV1-4, but no ADE. Furthermore, we plan to use papillomavirus-like particles (PV-VLPs) as an adjuvant to generate CD4+ T helper cells to enhance ZIKV/DENV-specific memory CTL responses. In Aim 1, we propose to make plasmids by using ZIKV/DENV1-4 NS3 as target antigens and rearranging their gene sequences and adding ubiquitin gene upstream. We will compare if they are better than unmodified NS3 in CTL generation. Then we will use PV-VLPs to make pseudoviruses (plasmids inside the VLPs) as the vaccine. We will test if the vaccine induces long-term CTL responses in mice. In Aim 2, we will determine whether immunization with the vaccine provides long-term protection (reduction of viral titers and/or prolonged survival) against ZIKV/DENV1-4 challenge without causing ADE in a novel HLA-B*0702 transgenic-AG129 mouse model. This project will provide a safe and effective candidate vaccine to prevent DENV/ZIKV-mediated diseases.
