The present invention relates to an immunostimulatory nanocomplex. The immunostimulatory nanocomplex comprises polyglutamic acid (PGA), a first positively charged substance, a second positively charged substance and a dengue viral protein for holding the dengue viral protein inside. The immunostimulatory nanocomplex is characterized by having a nonuniformally and positively charge distribution along a radial direction thereof. The nonuniformally and positively charge distribution comprises a first electrically charged portion having substantially electrical neutrality, a second electrically charged portion surrounding the first electrically charged portion, and a third electrically charged portion surrounding the second electrically charged portion. The third electrically charged portion has a third volume charge density more than a second volume charge density of the second electrically charged portion, thereby enhancing CD8(+) T-cell response and higher antibody titer after administrating an organism with the immunostimulatory nanocomplex.