Avaliação do potencial vacinal de três peptídeos sintéticos, conservados e tetravalentes derivados dos domínios I e II da proteína do envelope do dengue virus.

Abstract

Dengue is an arbovirus that has distinguished itself in recent years as a serious public health problem in Brazil. The Dengue virus (DENV) belongs to the family Flaviviridae, genus Flavivirus and its genome is composed of a single stranded RNA with positive polarity. Currently, there are five serotypes of DENV, which are genetically and antigenically distinct. The development of a vaccine that confers simultaneous, efficient and lasting immunity against the five serotypes of DENV is a priority given the magnitude of the problem. In this study, we evaluated the vaccine potential of three synthetic, conserved and tetravalent peptides (PEP01, PEP02 and PEP03) derived from the envelope protein. An indirect ELISA assay showed the reactivity of Dengue IgM/IgG human positive serum samples against the synthetic peptides. Immunization assays in mice have shown that these peptides were able to induce the production of specific antibodies. However, the neutralization assays showed absence or lower titers of neutralizing antibodies. The spleen cells derived from mice immunized with the peptides showed a high IL-10 expression and reduced expression of TNF-α and IFN-γ after infection for all DENV serotypes when compared with the positive control. In addition, cells from mice immunized with the PEP02 and PEP03 peptides present, in vitro, a significant reduction of cell viability after infection with the four DENV serotypes. To continue the evaluation of this vaccine candidate for dengue, it was expressed in prokaryote system a recombinant protein (PEPDENV) containing sequences of the PEP01, PEP02 and PEP03 fused to a specific sequence able to induce neutralizing antibodies. Immunization with PEPDENV protein showed the immunogenicity of this protein in inducing high production of IgG1 antibodies in mice, however the sera of immunized animals showed no neutralizing activity of the viral particle. Immunoenzymatics assay using the peptides as the substrates showed that the sera of immunized animals with PEPDENV were able to recognize the peptides, with a high reactivity to PEP03. These results suggest that the lack of neutralizing activity of the antibodies may be due to an immune response more directed to the PEP03 than to the other regions of the molecule, confirming the immunogenicity of this peptide. However, further studies aimed at modifying the peptide sequence will be required to induce the production of an effective immune response against all four serotypes of DENV and also to enhance the immunogenicity of these vaccine candidates.