The Epitope-substituted DNA Vaccine Improves Safety and Immunogenicity against Dengue Virus Type 2

• Main Authors: Chung-Tao Tang, 唐中道
• Other Authors: Han-Chung Wu
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/j58wkh

博士 === 國防醫學院 === 生命科學研究所 === 103 === Dengue virus (DENV), a global and mosquito-borne disease, is divided into four serotypes (DENV1-4). Cross-reactive and non-neutralizing antibodies against envelope (E) protein of DENV bind to the Fcγ receptors (FcγR) of cells, and thereby exacerbate viral infection by heterologous serotypes via antibody-dependent enhancement (ADE). Identification and modification of enhancing epitopes may mitigate enhancement of DENV infection. In this study, we characterized the DB21-6 and DB39-2 monoclonal antibodies (mAbs) against DENV1-4 and domain I-II of E protein by immunofluorescence assay (IFA); these antibodies poorly neutralized and potently enhanced DENV infection both in vitro and in vivo. In addition, DB21-6 and DB39-2 were observed to compete with sera antibodies from dengue patients for binding to DENV2. The epitopes of these enhancing mAbs were identified using phage display, structural prediction, and mapping of virus-like particle (VLP) mutants. N8, R9, V12, and E13 are the reactive residues of DB21-6, while N8, R9, and E13 are the reactive residues of DB39-2. N8 substitution tends to maintain VLP secretion, and decreases the binding activity of DB21-6 and DB39-2. After immunization by DNA vaccines, the N8R-immunized sera exerted greater in vitro neutralizing and in vivo protective activity against DENV2 in ICR suckling mice than wild-type (WT)-immunized sera. Furthermore, treatment with N8R-immunized sera reduced the enhancement of mortality in AG129 mice. These results support identification and substitution of enhancing epitope as a novel strategy for developing safe dengue vaccines.