Using a virion assembly-defective dengue virus as a vaccine approach.

Dengue virus (DENV) is the most prevalent mosquito-transmitted viral pathogen in humans. The recently licensed dengue vaccine has major weaknesses. Therefore, there is an urgent need to develop improved dengue vaccines. Here we report a virion assembly-defective DENV as a novel vaccine platform. DENV containing an amino acid deletion (K188) in nonstructural protein 2A (NS2A) is fully competent in viral RNA replication, but is completely defective in virion assembly. When trans complemented with wild-type NS2A protein, the virion assembly defect could be rescued, generating pseudoinfectious virus (PIVNS2A) that can initiate single-round infection. The trans-complementation efficiency could be significantly improved through selection for adaptive mutations, leading to high yield of PIVNS2A production with titers of >107 infectious forming units (IFU)/ml. Mice immunized with a single dose of PIVNS2A elicited strong T cell immune response and neutralization antibodies, and were protected from wild-type virus challenge. Collectively, the results have proved the concept of using assembly-defective virus as a new vaccine approach. The study has also solved the technical bottleneck to produce high yield of PIVNS2A vaccine. The technology could be applicable to vaccine development for other viral pathogens.IMPORTANCE Many flaviviruses are significant human pathogens that pose global threats to public health. Although licensed vaccines are available for yellow fever, Japanese encephalitis, tick-borne encephalitis, and dengue viruses, new approaches are needed to develop improved vaccines. Using dengue virus as a model, we report a novel vaccine platform by using a virion assembly-defective virus. We show that such assembly-defective virus could be rescued to higher titers, and infect cells for a single round. Mice immunized with the assembly-defective virus were protected from wild-type virus infection. This vaccine approach could be applicable to other viral pathogens.