Pre-existing dengue virus (DenV) immunity is a risk factor for severe dengue mediated by antibody-dependent enhancement (ADE), which occurs when a seropositive DenV patient is re-infected with a DenV of a different serotype. DenV and Zika virus (ZikV) are highly similar, and ADE has been observed between them. As DenV and ZikV co-circulate in many regions of the world, a vaccine that provides protection against both viruses without inducing ADE is needed. The main objective of this work was to determine the potential as a vaccine candidate of a mimotope of the shared epitope EDE of DenV and ZikV, displayed in the capsid of adeno-associated virus serotype 8 (AAV-8).

AAV-8 capsids that display the EDE mimotope (chimeric VLP) and native control capsids (native VLP) were produced. The VLPs were purified using iodixanol gradients and characterized by Western blot, dot blot, transmission electron microscopy, and cryo-electron microscopy, showing that the chimeric VLPs were recognized by a monoclonal antibody specific for DenV and ZikV, and not for AAV-8, and that the chimeric protein assembled into AAV-8 capsids with typical morphologies. Groups of BALB/c mice were subcutaneously or intramuscularly immunized with chimeric VLP, native VLP, or controls. Serum samples were collected to evaluate the humoral immune response through the ELISA test. Mice immunized with chimeric VLP produced antibodies that recognized DenV serotype 2 and ZikV. In silico biophysical studies were performed to analyze the interaction between the mimotope and the antibody against DenV and ZikV. We then evaluated the function of the chimeric VLP as a viral vector. The chimeric VLP could encapsidate the eGFP gene and transduce the HEK-293 and CHO cells, showing that the function of the AAV vector was retained after modification.

This work represents a new strategy for the development of a vaccine against DenV and ZikV based on a mimotope.