Fifteen days after the third inoculation, the mice were challenged intracerebrally with a dose of 100LD50 (previously determined), prepared

from a DENV-4-infected suckling mouse brain (mouse-adapted H241 strain). Mouse mortality was monitored daily for 21 days. The statistical analysis (Long-Rank test, Mantel-Cox) was performed with GraphPad Prism 5.0 (GraphPad Software Inc., San Diego, CA). DENV-4-DNAv transfected cells Rucaparib showed positive fluorescence where DENV-4-specific MIAF was used, which indicates the expression of the DENV-4 prM and E proteins. In the cells transfected with pCI no fluorescence was seen. As positive control we used cells infected with dengue-4 virus, these cells were incubated with primary antibodies (DENV-4 MIAF) and secondary antibody (anti-mouse IgG) and analyzed in optical microscopy (Fig. 1). The band corresponding to prM and E protein, of approximately 53–54 kDa, was clearly visible in the lanes containing DENV-4-DNAv transfected cell lysates. This band corresponds to the expected molecular weight of the E protein and was detected in cell lysates by

immunoprecipitation followed by western blot from culture infected with dengue-4 virus and transfected with recombinant plasmid but not in cultures transfected with empty pCI (Fig. 2). Neutralizing antibodies is the goal of dengue vaccination; to evaluate the induction capacity of our construction we performed a PRNT assay, comparing the results with SKI-606 nmr virus immunization that is associated with induction of high levels

of neutralizing antibodies. As expected, animals immunized with the pCI plasmid did not produce neutralizing antibodies against dengue-4 virus. On the other hand, the animals immunized with DENV-4-DNAv unless produced rising levels, after each vaccine inoculation, of specific neutralizing antibodies against dengue-4 virus. The neutralizing antibody titers of DENV-4-DNAv immunized group were only one dilution lower than those titers observed in DENV-4-immnunized mice (Table 2). Once we detected satisfactory neutralizing antibodies levels after vaccination, we decided to evaluate the vaccine protection after challenge with a lethal infection. The spleen cells of DENV-4-DNAv-immunized animals produced high levels of IL-2, IL-10, IFN-γ in the presence of ConA and DENV-4 compared to non-stimulated cells. Cell supernatants of DENV-4-DNAv-immunized animals showed much higher concentrations of IL-10 and IL-2 than IFN-γ. The same profile was seen in the cell supernatants of mice immunized with DENV-4. IL-4 was not detected in any group of immunized mice independent of the time of supernatant collection (Fig. 3). To address if T cells obtained from DENV-4-DNAv immunized mice could respond to specific antigen stimulus, BALB/c mice were inoculated with 100 μg of DENV-4-DNAv in the quadriceps muscle as described in Section 2.