Splenic lymphocytes derived from DENV-4-DNAv inoculated group demonstrated high proliferative response to inactivated dengue virus. Fig. 4 shows the results obtained in the confirmatory experiment. T cell proliferation in the DENV-4-DNAv group was approximately 20%, similar to that observed in DENV-4 immunized group, suggesting that our vaccine induced a good cellular immune stimulation. In addition, proliferation responses of DENV-4-DNAv group were higher than that observed in the negative control. The results in Fig. 4 are representative of four animals

per group, but in both experiments all mouse-inoculated groups responded in a similar fashion. DENV-4-DNAv vaccine candidate was evaluated for their ability to induce protective immunity against lethal challenge with DENV-4. Groups of 10 three-week-old BALB/c mice were immunized with recombinant plasmid, positive and negative control Dolutegravir clinical trial mice were immunized with

DENV-4 (1 × 105 PFU) and with 100 μg of pCI, respectively. As shown in Fig. 5, immunization with DENV-4-DNAv induced significant protection against DENV-4 challenge, comparable to that observed in DENV-4 inoculated mice, where 80% of the challenged mice survived. However, only 20% survival was observed after immunization with pCI and no survival was obtained with PBS immunization. The protection levels of the immunized S3I-201 in vitro group was statistical significant (p = 0.01), when this group was compared with pCI immunized animals (Mantel-Cox statistical analysis). Dengue is responsible for the highest mortality and morbidity rates than any other disease caused by an arbovirus in humans [22]. Annually, more than 100 million cases of dengue fever and about 500,000 cases of DHF occur, and since there is no treatment for these diseases, immunization may provide the most realistic approach for controlling dengue infections [1] and [2]. The

efforts the for the development of vaccines against to dengue began more than 50 years ago, when serious cases of the disease were recognized, and since the 1970s the World Health Organization has sponsored several studies to obtain these vaccines [23] and [24]. A recombinant DNA vaccine is a new approach consisting of a plasmid backbone and the gene encoding the antigen of interest, and it is considered efficient due to the fact that it elicits both, the humoral and cellular immune responses. DNA vaccines have been tested in a series of animal models, including experimental infections in mice and primates [20] and [25]. Recently, there has been a remarkable effort on the development of DNA vaccines because they are safe, induces fewer side effects than the live attenuated vaccines, can be administered to immunocompromised individuals, are cheap to manufacture, and need low infrastructure for maintenance [26].