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Abstract:
Dengue virus (DEN) infection may cause a mild febrile illness or the more severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). However, the mechanisms of DHF/DSS on subsequent infection with another serotype of dengue virus are not completely understood. Although the antibody-dependent enhancement (ADE) hypothesis showed that sub-neutralizing or non-neutralizing antibody derived from previous infection may enhance dengue virus infection in the next time, a causal relationship between ADE and DHF/DSS remains unverified. These problems increase the difficulty in development of safe and effective dengue virus vaccine.
Efforts to create a subunit vaccine by use of recombinant protein technology have been initiated. In an attempt to avoid the onset of ADE syndromes, studies have been undertaken to assess the protective capacity induced by non-structural-1 protein (NS1). In this study, we have purified a full length NS1 protein that is expressed from PRESET-DVNS1 plasmid in E. coli.. The antigenicity of recombinant NS1 protein is evaluated by Western blotting, ELISA, and immunofluorescence staining of DEN2-infected BHK-21 cells. Sera from B6 mice preimmunized with recombinant NS1 showed antibody-dependent complement-mediated lysis of DEN2-infected but not of non-infected BHK-21 cells, implicated a protective effect conferred by the anti-NS1 antibody.
Previous report showed that anti-NS1 antibodies generated in mice cross-reacted with human platelets. Our study showed that sera from dengue patients contained anti-NS1 antibodies which also cross-reacted with human platelets as compared to the control sera. Further studies indicated that mouse anti-recombinant NS1 antibodies could bind to human umbilical vein endothelial cells and suppressed ADP-induced platelet aggregation function in vitro, suggesting a role for immune-mediated hemostatic abnormalities. Although previous reports showed that NS1 could elicit a protective immune response in mice, some epitopes on NS1 may cause hemostatic abnormalities. To provide a more satisfactory and protective dengue vaccine candidate, a strategy may be proceeded by deleting the epitopes which cause the pathogenic effects.
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