Generating neutralizing antibodies have been considered a prerequisite to control dengue virus (DENV) infection. However, T lymphocytes have also been shown to be important in a protective immune state. In order to investigate the contribution of both humoral and cellular immune responses in DENV immunity, we used an experimental model in which a non-lethal DENV2 strain (ACS46) is used to intracranially prime Balb/C mice which develop protective immunity against a lethal DENV2 strain (JHA1). Primed mice generated envelope-specific antibodies and CD8(+) T cell responses targeting mainly non-structural proteins. Immune sera from protected mice did not confer passive protection to naïve mice challenged with the JHA1 strain. In contrast, depletion of CD4(+) and CD8(+) T lymphocytes significantly reduced survival of ACS46-primed mice challenged with the JHA1 strain. Collectively, results presented in this study show that a cellular immune response targeting non-structural proteins are a promising way in vaccine development against dengue.

Dengue fever is caused by any of the four known dengue virus serotypes (DENV1 to DENV4) that affect millions of people worldwide, causing a significant number of deaths. There are vaccines based on chimeric viruses, but they still are not in clinical use. Anti-DENV vaccine strategies based on nonstructural proteins are promising alternatives to those based on whole virus or structural proteins. The DENV nonstructural protein 5 (NS5) is the main target of anti-DENV T cell-based immune responses in humans. In this study, we purified a soluble recombinant form of DENV2 NS5 expressed in Escherichia coli at large amounts and high purity after optimization of expression conditions and purification steps. The purified DENV2 NS5 was recognized by serum from DENV1-, DENV2-, DENV3-, or DENV4-infected patients in an epitope-conformation-dependent manner. In addition, immunization of BALB/c mice with NS5 induced high levels of NS5-specific antibodies and expansion of gamma interferon-and tumor necrosis factor alpha-producing T cells. Moreover, mice immunized with purified NS5 were partially protected from lethal challenges with the DENV2 NGC strain and with a clinical isolate (JHA1). These results indicate that the recombinant NS5 protein preserves immunological determinants of the native protein and is a promising vaccine antigen capable of inducing protective immune responses. Dengue fever is an acute disease caused by dengue virus (DENV), an arbovirus belonging to the Flaviviridae family, transmitted by Aedes mosquitoes (1, 2). In urban settings, DENV is found as four immunologically distinct types (serotypes), DENV1 to DENV4, which have approximately 30% divergence in their genomic nucleotide sequences (3-7). The disease may present with different degrees of manifestations that are classified by the WHO as dengue fever, dengue with warning signs, and severe dengue (8). A recent study showed that, annually, an average of 96 million DENV-infected people develop symptoms with severity sufficient to change their routines (1); according to previous studies, about 500,000 cases develop into severe forms of disease, which may include hemorrhage and shock syndrome (9). The mortality rate in this group reaches 10% in hospitalized patients, increasing to 30% in nontreated DENV-infected patients (9-11). Despite the high epidemiological importance of dengue fever, no effective anti-DENV drug or vaccine formulation is in clinical use for treatment or prevention of the disease.Several strategies have been explored, aiming toward the development of an effective dengue vaccine (12-21). Nonetheless, a tetravalent vaccine formulation requires a neutralizing response to all four serotypes (22)(23)(24)(25). A poor vaccine-induced response to structural proteins of any of the four serotypes may pose a risk of the onset of antibody-dependent enhancement (ADE) of virus replication upon infection by a subneutralized serotype (22-25). Moreover, protection based on the induction of neutralizing antibodies targeting structural proteins may be neg...

Dengue virus (DENV) causes dengue fever, a widely distributed endemic disease transmitted by mosquitoes. The complex interaction of DENV with the human immune system has complicated the development of an effective vaccine. This may be attributed, at least in part, to the lack of a suitable animal model capable to reproduce symptoms observed in humans. Mouse models are simple but usually rely on host-adapted virus strains or immunodeficient mouse lineages. Recent evidences indicated that some natural DENV strains are capable to infect immunocompetent mice. In addition, humanized mouse lineages can more faithfully reproduce some of the symptoms observed in humans. Such experimental models are valuable tools for the study of DENV biology.

effects of Escherichia coli thermo-labile toxin (LT1) derivatives in the specific antibody response directed to the E glycoprotein domain III of type 2 dengue virus (DENV2). 2014. 88 p. Masters thesis (Biology of Host-