Zika virus (ZIKV) causes an increase of Guillain Barre syndrome and microcephaly. ZIKV is transmitted via Aedes mosquitos, which also spreads dengue virus (DENV). DENV has four serotypes that differ by 30-35% and DENV envelop protein differs from ZIKV envelop protein by 41-46%. Primary infection by DENV leads to life-long immunity to the infecting serotype but not to the other serotypes. Secondary infection by other serotypes is often associated with life-threatening complications. It is believed that the antibodies generated in the primary infection opsonize the secondary virus in the secondary infection to target monocytes and macrophages via Fc-receptor-mediated endocytosis leading to higher viral loads and severe diseases, i.e. antibody-dependent enhancement (ADE) of infection. It was shown that human monoclonal antibodies generated from DENV-infected subjects cross-reacted with ZIKV. Importantly they greatly enhanced ZIKV infection, potentially ADE in humans. To develop a vaccine that prevents ADE, we propose to develop a unique vaccine which will induce ZIKV and DENV1-4-specific cytotoxic T lympgocytes (CTLs) but no specific antibodies. CTLs alone are shown to effectively control infection in DENV mouse model. We hypothesize that a vaccine inducing CTLs specific for ZIKV and DENV1-4 NS3,4b and 5 will prevent ADE by reducing the secondary infection. We plan to use papillomavirus-like particles (PV VLPs) as a delivery vector and an adjuvant: PV VLPs are highly immunogenic and are the major components for the HPV vaccines approved by the FDA. The VLPs can also be used to package DNA plasmids that carry genes of interest to form papillomavirus pseudoviruses. The pseudoviruses can enter dendritic cells and macrophages for antigen presentation. The VLPs as well as DNA itself can activate the NLRP3 and AIM2 inflammasomes, respectively, to help mount effective adaptive immune responses. Notably, the pseudoviruses are able to elicit strong immune responses via systemic immunization route. We plan to use the VLPs to make pseudoviruses encoding ZIKV and DENV1-4 NS3/4b/5 proteins to induce specific CTLs and effector memory T cells.
In Aim 1 we will develop papillomaviruses pseudoviruses carrying plasmids expressing NS3/4b/5 protein fragments unique to ZIKV and DENV1-4. We will make the proteins unstable and degraded in proteasomes to avoid antibody induction and to enhance CTL generation by rearranging the gene sequences and adding ubiquitin at its 5's end; We plan to use bovine papillomavirus and cottontail rabbit papillomavirus VLPs to package plasmids encoding the unstable and ubiquinated ZIKV and DENV1-4 NS3/4b/5 proteins to make the pseudoviruses.
In Aim 2, we will test if systemic immunization with the pseudoviruses induces strong NS3/4b/5-specific CTL and effector memory T cell responses. Further we plan to test if the vaccine will reduce ADE of infection in the animal models.
Zika virus or Dengue virus infection can cause severe diseases. The goal of this project is to develop an effective vaccine to prevent the severe diseases. This vaccine will contribute to saving lives worldwide.
