However, IL-4 was also detected providing an evidence for a Th2-mediated immune response. Rothman et al. , analyzing a tetravalent inactivated dengue vaccine, also detected high levels IFN-γ, but no IL-4 after the stimulation with dengue virus. We suggest that our high levels of IL-10 can be associated with a Th2 pattern immune response, it is accepted that this type of response is able Lonafarnib ic50 to induce a strong antibody production. However, we
did not evaluate the production of IgG1 versus IgG2a antibodies and so we cannot confirm the shift of immune response in favor of Th2 pattern. The cellular proliferation assay, accessed by flow cytometry, evaluated the activation of spleen cells from mice immunized with DENV-4-DNAv, DENV-4 (positive control), and pCI (negative control). Spleen cells of all groups of immunized animals presented find more a significant proliferation
in the presence of lymphocyte mitogen concanavalin A, compared to cells that were not stimulated (media stimulation). When specifically stimulated with DENV-4, the spleen cells from DENV-4-DNAv-immunized mice proliferated in a significant higher percentage than cells from pCI-immunized animals (negative control) and did not exhibited a significant difference in proliferation compared to the cells of the animals in the DENV-4-immunized group. Taking together, these data confirmed that the DENV-4 and DENV-4-DNAv were capable of inducing a specific immune response in the immunized mice. Data on T cell response after immunization against dengue are scarce, mainly because most of the studies on dengue vaccine development focus their search for a specific immune response on neutralizing antibodies . Here we show a
positive performance of DENV-4-DNAv vaccine concerning its ability to induce specific T cell response, antibody production and protection after challenge. The challenge experiments show that 80% of the mice immunized with DENV-4-DNAv were protected from the disease induced by the intracerebral inoculation with lethal doses of DENV-4, the same percentage observed in DENV-4 immunized mice. On the other hand, in pCI and PBS-inoculated animals, the protection rate was 20% and 0%, respectively. The observation that 20% Adenosine of the inoculated mice in the DENV-4 and DENV-4-DNAv died after challenge despite the fact that all of them developed neutralizing antibodies might be explained by the animal model used in dengue vaccine experiments. The animal model most frequently used to test the efficacy of dengue vaccines during dengue vaccine development is based in intracerebral inoculation of mice with a mouse-brain-adapted dengue virus. However, this model does not represent a natural disease as encephalitis is not commonly associated with dengue infections.