Multifunctional calcium phosphate nanoparticles as novel HIV-1 vaccine platform

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The importance of IgG Fc-effector functions for the efficacy of HIV vaccines is increasingly recognized. Although different types of vaccines were shown to induce antibodies with different Fc-activities, there is no clear strategy how to raise HIV-Env antibody responses with a desired pattern of Fc-effector functions. Previously we demonstrated that the antibody responses to Env appear to be biased, both in humans and in mice. And Env-specific CD4+ T-cells with a Th2-shifted phenotype are responsible for the IgG1 bias in mice. Based on our previous results, we propose to explore two novel HIV-1 vaccination strategies, both based on multifunctional calcium-phosphate (CaP) nanoparticles (NPs). We aim to bypass the Env-induced bias in T-helper cell responses, and maintain the native trimeric structure of the Env immunogen required to raise antibodies to conformational epitopes. The work programme includes a novel two component vaccine strategy, in which first component is optimized for induction of T-helper cell responses, while the second component presents the Env immunogen in the correct conformation to the B-cells. For priming of HIV-Env specific T-helper cell responses, we propose to encapsulate linear synthetic peptides of HIV-Env together with TLR-ligands for Th1 T-cell polarization in CaP nanoparticles. Surface functionalization with CD11c-targeting antibodies should guide these NPs to dendritic cells. To target B-cells we aim to develop and characterize CaP NPs directionally coated with conformationally stabilized, soluble HIV-1 Env-spikes and functionalized with TLR-ligands inside. A second vaccination strategy includes the recruitment of heterologous Th cells induced by a common licensed to provide efficient intrastructural help for Env-functionalized CaP-wrapped virus particles. Wrapped particles used in licensed vaccines will be protected from the antibody responses, but be rapidly unwrapped due to the acidic pH in the endo-lysosome after uptake by antigen-presenting cells. The immunogenicity of the two different vaccination strategies will be determined in mouse models.