| Summary: | 碩士 === 國立成功大學 === 微生物及免疫學研究所 === 102 === Dengue virus (DENV) is a mosquito-transmitted flavivirus with four serotypes and is endemic in tropical and subtropical regions of the world. Infection with DENV causes diseases ranging from mild dengue fever to severe dengue hemorrhagic fever and dengue shock syndrome. Currently, there is no approved vaccine to prevent dengue infection. Our previous studies showed that the cross-reactive epitopes reside in the C-terminal region of DENV nonstructural protein 1 (NS1), and cause anti-DENV NS1 antibodies (Abs)-mediated endothelial cell apoptosis and platelet dysfunction. Therefore, we deleted the C-terminal region of DENV NS1 protein or replaced the C-terminal region with JEV NS1 protein, to generate ΔC NS1 and DJ NS1, respectively. Our previous studies also suggested that passive immunization with anti-ΔC or anti-DJ NS1 Abs twice can provide some therapeutic effects in DENV-infected mice. In this study, we attempted to determine the effective single dose of anti-modified NS1 Abs against DENV infection in a therapeutic mouse model. Results showed that the DENV-induced prolonged bleeding time was significantly reduced by treatment with anti-DJ NS1 Abs with a single dosage. Besides polyclonal Abs, we also investigated the therapeutic effects of anti-NS1 monoclonal Abs (mAbs). The mAb 2E8 can recognize NS1 of all four DENV serotypes, but does not recognize epitopes of DENV NS1 which cross-react with host proteins. Further analysis showed that the epitope recognized by mAb 2E8 is on the solvent accessible area of NS1. We found that mAb 2E8 causes complement-mediated cytolysis in vitro after DENV infection. Chimeric mAb 2E8 and another therapeutic candidate mAb 31B2 also induce complement-mediated cytolysis of DENV-infected cells. In the mouse model studies, treatment with mAb 2E8 reduced mouse tail prolonged bleeding time, viral antigen expression, and macrophage infiltration to local infection sites. We further found that administering anti-DJ NS1 or mAb 2E8 at day 1, 3, or 4 post-inoculation reduced prolonged bleeding time and hemorrhage even at day 5 post-infection. In summary, administration of a single dose of anti-DJ NS1 Abs or mAb 2E8 protected mice against DENV infection, suggesting that anti-modified DENV NS1 Abs may be a therapeutic option against dengue disease.
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