Despite the approval of a Dengue virus (DV) vaccine in five endemic countries, dengue prevention would benefit from an immunization strategy highly immunogenic in young infants and not curtailed by viral interference. Problematically, infants younger than 9 year of age, whom are particularly prone to Dengue severe infection and death, cannot be immunized using current approved DV vaccine. The most important issues documented so far are the lack of efficiency and enhancement of the disease in young seronegative recipients, as well as uneven protection against the four DV serotypes. Based on data from clinical trials that showed enhanced performance of dengue vaccines when the host has previous anti-flaviviral immunity, I proposed here an attractive solution to complement the current vaccine: a recombinant measles vaccine vectoring dengue protective antigens to be administered to young infants. I hypothesized that recombinant measles virus expressing Dengue 2 and 4 antigens would successfully induce neutralizing responses against DV2 and 4 and the vaccine cocktail of this recombinant measles can prime anti-flaviviral neutralizing immunity. For this dissertation, I generated and performed preclinical immune assessment for four novel Measles-Dengue (MV-DV) vaccine candidates. I generated four MVs expressing the pre membrane (prM) and full length or truncated (90%) forms of the major envelope (E) from DV2 and DV4. Two virus, MVvac2-DV2(prME)N and MVvac2-DV4(prME), expressed high levels of membrane associated full-length E, while the other two viruses, MVvac2-DV2(prMEsol)N and MVvac2-DV4(prMEsol)N, expressed and secreted truncated, soluble E protein to its extracellular environment. The last two vectored vaccines proved superior anti-dengue neutralizing responses comparing to its corresponding full length vectors. Remarkably, when MVvac2-DV2/4(prMEsol)N recombinant vaccines were combined, the vaccine cocktail was able to prime cross-neutralizing responses against DV 1 and the relatively distant 17D yellow fever virus attenuated strain. Thus, I identify a promising DV vaccination strategy, MVvac2-DV2/4(prMEsol)N, which can prime broad neutralizing immune responses by using only two of the four available DV serotypes. The current MV immunization scheme can be advantageus to prime broad anti-flaviviral neutralizing immunity status, which will be majorly boosted by subsequent chimeric Dengue vaccine approaches.

ABSTRACT In terms of prevalence, human suffering and costs dengue infections are the most important arthropod-borne viral disease worldwide. Dengue virus (DENV) is a mosquito-borne flavivirus and the etiological agent of dengue fever and dengue hemorrhagic fever. Thus, development of a safe and efficient vaccine constitutes an urgent necessity. Besides the traditional strategies aim at generating immunization options, the usage of viral vectors to deliver antigenic stimulus in order to elicit protection are particularly attractive for the endeavor of a dengue vaccine. The viral vector (MVvac2) is genetically equivalent to the currently used measles vaccine strain Moraten, which adds practicality to my approach. The goal of the present study was to generate a recombinant measles virus expressing structural antigens from two strains of DENV (DENV2 and DENV4) The recombinant vectors replication profile was comparable to that of the parental strain and expresses either membrane bound or soluble forms of DENV2 and DENV4 E glycoproteins. I discuss future experiments in order to demonstrate its immunogenicity in our measles-susceptible mouse model.