mRNA-LNP Vaccines Encoding for Dengue Optimized prM/ENV Proteins Induce Protective Immunity without ADE

Dengue virus (DENV) is the most common mosquito-borne virus in the world, causing nearly 400 million infections annually. Despite this prevalence there are no approved vaccine for DENV naïve individuals or therapeutics. DENV consists of four distinct serotypes, DENV 1-4, that share 60-70% homology. Development of a safe and efficacious pan-Dengue vaccine has been complicated by the potential of antibody-dependent enhancement, in which cross-reactive non-neutralizing antibodies can enhance infection and pathology. We previously demonstrated that a mRNA-LNP that encodes for the DENV-1 prM and Envelope proteins generates homotypic neutralizing immune responses and protects against a lethal challenge. The DENV-1 vaccine avoided ADE by 3-point mutations, G106R, L107D, and F108A, to the fusion loop (FL), one of the dominant ADE epitopes. Using a similar design methodology, here we present mRNA-LNP chimeric prM-E vaccines for DENV 2, 3, and 4. These vaccines maintained the ΔFL modifications, but encode a chimeric E protein with Japanese Encephalitis Virus’ (JEV) stem/transmembrane (st/tm) to improve VLP expression and stability. All three vaccines elicited neutralizing titers of serotype specific antibodies in immunocompetent C57/BL6 mice and are protected against a lethal homotypic DENV challenge in susceptible mice. Mutation of the FL epitope lowered ADE in the sera from vaccinated mice. We formulated monoclonal vaccines against all DENV serotypes into a single tetravalent vaccine and evaluated for immunogenicity and protection in mice. The tetravalent vaccine elicited a mixed response with antiviral CD4 and CD8 T cells against all four DENV serotypes and neutralizing humoral responses against DENV 3 and DENV 4. Tetravalent vaccine recipient mice were protected against a lethal DENV 3 or DENV 4 challenge. Cumulatively, we have produced monovalent DENV mRNA-LNP vaccines against all four DENV serotypes that generate protective immunity and lower the potential for ADE.