A novel pan-epitope based nanovaccine self-assembled with CpG enhances immune responses against flavivirus

Flavivirus is a highly prevalent and outbreak-prone disease, affecting billions of individuals annually and posing substantial public health challenges. Vaccination is critical to reducing the global impact of flavivirus infections, making the development of a safe and effective vaccine a top priority. The self-assembled pan-epitope vaccine presents key advantages for improving immunogenicity and safety without relying on external vectors or adding immunomodulatory elements, both of which are essential for successful vaccine development. In this study, the pan-epitope peptide TBT was combined with adjuvant CpG to form the TBT-CpG nanovaccine (TBT-CpG NaVs), which was found to be spherical, uniform in shape, and demonstrated strong serum stability. In vitro studies showed that the TBT-CpG NaVs were efficiently taken up and internalized by bone marrow-derived dendritic cells (BMDCs). Flow cytometry and transcriptomic analysis indicated that the antigens were effectively presented to antigen-presenting cells (APCs) via the MHC II pathway, which facilitated BMDCs maturation and promoted the release of pro-inflammatory cytokines IL-1β, TNF-α, and IL-6. In vivo studies confirmed that TBT-CpG NaVs enhanced antigen-specific IgG levels, significantly increased IFN-γ and IL-4 expression in spleen cells, and offered protective effects against Dengue virus (DENV) and Zika virus (ZIKV) infections. Safety evaluations revealed no hepatotoxicity and no significant organ damage in immunized mice. The self-assembled candidate nanovaccine TBT-CpG NaVs effectively activates BMDCs and triggers a targeted immune response, providing antiviral effects against DENV and ZIKV. This vaccine demonstrates good immunogenicity and safety, establishing a promising foundation and a new strategy for the development of safe and effective vaccines.