Cooperation between CD4+ T Cells and Humoral Immunity Is Critical for Protection against Dengue Using a DNA Vaccine Based on the NS1 Antigen

Abstract

Dengue virus (DENV) is spread through most tropical and subtropical areas of the world and represents a serious public health problem. At present, the control of dengue disease is mainly hampered by the absence of antivirals or a vaccine, which results in an estimated half worldwide population at risk of infection. The immune response against DENV is not yet fully understood and a better knowledge of it is now recognized as one of the main challenge for vaccine development. In previous studies, we reported that a DNA vaccine containing the signal peptide sequence from the human tissue plasminogen activator (t-PA) fused to the DENV2 NS1 gene (pcTPANS1) induced protection against dengue in mice. In the present work, we aimed to elucidate the contribution of cellular and humoral responses elicited by this vaccine candidate for protective immunity. We observed that pcTPANS1 exerts a robust protection against dengue, inducing considerable levels of anti-NS1 antibodies and T cell responses. Passive immunization with anti-NS1 antibodies conferred partial protection in mice infected with low virus load (4 LD50), which was abrogated with the increase of viral dose (40 LD50). The pcTPANS1 also induced activation of CD4+ and CD8+ T cells. We detected production of IFN-γ and a cytotoxic activity by CD8+ T lymphocytes induced by this vaccine, although its contribution in the protection was not so evident when compared to CD4+ cells. Depletion of CD4+ cells in immunized mice completely abolished protection. Furthermore, transfer experiments revealed that animals receiving CD4+ T cells combined with anti-NS1 antiserum, both obtained from vaccinated mice, survived virus infection with survival rates not significantly different from pcTPANS1-immunized animals. Taken together, results showed that the protective immune response induced by the expression of NS1 antigen mediated by the pcTPANS1 requires a cooperation between CD4+ T cells and the humoral immunity.

Immunization with E Plus NS1-2a Enhanced Protection against Dengue Virus Serotype 2 in Mice

“…Furthermore, E+NS1-2a induced the highest anti-DENV titre, indicating there was no interference in expression and inducing immune response between those two proteins, implying that two proteins may trigger immune response via different mechanism. Our results were further supported by study from Gonçalves group, which found that effective defences against DENV can be achieved with the combination of both antibodies and T cells responses but not any of them alone [24]. Our results suggested that a combination of E and NS1-2a could induce both humoral and cellular immunity and that a balanced Th1/Th2 immune response is a primary goal for the development of DENV vaccines.…”

“…However, there is no effective human DNA vaccine available due to the poor immunogenicity observed in clinical studies. Our previous studies and others showed that co-expressing prME and NS1 of DENV1 or DENV2 could induce strong immune responses and enhance survival of infected mice [18,23,24] when compared with prME alone. However, the long fragment of prME and NS1 may limit DNA expression and thereby reduce immune response.…”

HLA-DRB1 Alleles Are Associated With Different Magnitudes of Dengue Virus–Specific CD4+T-Cell Responses

“…Some studies have suggested a potential contribution of DENV-specific CD4 + T-cell responses to disease pathogenesis, while other studies have illustrated a potential protective role for this type of adaptive response [2][3][4]. DENV-specific CD4 + T cells were associated with direct effector cytotoxic function and, thus, have the potential to directly contribute to viral clearance by clearing DENV-infected macrophages that contribute to disease pathogenesis through the effects of antibody dependent enhancement [5][6][7].…”

Cyclic Dinucleotide–Adjuvanted Dengue Virus Nonstructural Protein 1 Induces Protective Antibody and T Cell Responses

“…In clinical trials, the NIH TV-003 DENV vaccine candidate induced NS1-specific CD4 + and CD8 + T cell responses comparable in breadth and magnitude to those found upon natural infection (54,55). Furthermore, a study testing an NS1-based DNA vaccine in mice indicated that both NS1-specific Abs and CD4 + T cells are critical for protection against DENV infection (17). Thus, these data suggest that the induction of NS1-specific CD4 + T cell responses by dengue vaccine candidates may significantly contribute to protective efficacy.…”

“…Importantly, NS1 is ∼64-79% conserved across the four DENV serotypes (11,12), and immunodominant regions of this protein have been identified in both NS1immunized and DENV-infected mice, as well as in naturally infected humans (10,(13)(14)(15)(16). The role of NS1-specific CD4 + T cells against DENV infection is a topic of active investigation, and studies have provided evidence of the likely protective effect of these cells (17)(18)(19)(20). Taken together, these findings support further research of NS1 as an important Ag for dengue vaccine development.…”