Date Published: March 21, 2014
Publisher: Public Library of Science
Author(s): Shu-Wen Wan, Yi-Tien Lu, Chia-Hui Huang, Chiou-Feng Lin, Robert Anderson, Hsiao-Sheng Liu, Trai-Ming Yeh, Yu-Ting Yen, Betty A. Wu-Hsieh, Yee-Shin Lin, Balaji Manicassamy.
Infection with dengue virus (DENV) may cause life-threatening disease with thrombocytopenia and vascular leakage which are related to dysfunction of platelets and endothelial cells. We previously showed that antibodies (Abs) against DENV nonstructural protein 1 (NS1) cross-react with human platelets and endothelial cells, leading to functional disturbances. Based on sequence homology analysis, the C-terminal region of DENV NS1 protein contains cross-reactive epitopes. For safety in vaccine development, the cross-reactive epitopes of DENV NS1 protein should be deleted or modified.
We tested the protective effects of Abs against full-length DENV NS1, NS1 lacking the C-terminal amino acids (a.a.) 271-352 (designated ΔC NS1), and chimeric DJ NS1 consisting of N-terminal DENV NS1 (a.a. 1-270) and C-terminal Japanese encephalitis virus NS1 (a.a. 271-352). The anti-ΔC NS1 and anti-DJ NS1 Abs showed a lower binding activity to endothelial cells and platelets than that of anti-DENV NS1 Abs. Passive immunization with anti-ΔC NS1 and anti-DJ NS1 Abs reduced DENV-induced prolonged mouse tail bleeding time. Treatment with anti-DENV NS1, anti-ΔC NS1 and anti-DJ NS1 Abs reduced local skin hemorrhage, controlled the viral load of DENV infection in vivo, synergized with complement to inhibit viral replication in vitro, as well as abolished DENV-induced macrophage infiltration to the site of skin inoculation. Moreover, active immunization with modified NS1 protein, but not with unmodified DENV NS1 protein, reduced DENV-induced prolonged bleeding time, local skin hemorrhage, and viral load.
These results support the idea that modified NS1 proteins may represent an improved strategy for safe and effective vaccine development against DENV infection.
Dengue virus (DENV) belongs to the Flaviviridae family of enveloped, positive-strand RNA viruses, and is transmitted by Aedes mosquitoes. With increased international travel and climate change, the prevalence of dengue is spreading beyond its usual tropical and subtropical boundaries. Hence, dengue is becoming one of the most important health issues in the world. DENV infection causes variable clinical presentations ranging from mild dengue fever to severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). The major clinical manifestations of DHF/DSS are thrombocytopenia and vascular leakage, although additional symptoms, such as liver damage, may occur -.
This is the first study demonstrating vaccine potential for Abs against a modified DENV NS1 protein, from which harmful cross-reactive epitopes have been selectively deleted. Although the NS1 protein is not a virion structural protein, Abs against it can protect against infection of several flaviviruses in vivo, such as Yellow Fever Virus , , JEV , , West Nile Virus ,  and DENV , -, . Abs against NS1 exhibit cytolytic activity to kill virus-infected cells in a complement-dependent manner. In the present study, we demonstrate that not only anti-DENV NS1 Abs but also anti-ΔC NS1 and anti-DJ NS1 Abs possess the ability of Ab-mediated complement-dependent cytotoxicity. Moreover, all three Abs have the ability to control viral load in vivo (Figure 5) and in vitro (Figure 6B). A previous report showed that anti-NS1 Abs trigger Fcγ receptor-mediated phagocytosis and clearance of West Nile Virus-infected cells . Therefore, in addition to Ab-mediated complement-dependent cytotoxicity, other mechanisms by which anti-ΔC NS1 and anti-DJ NS1 Abs contribute to protection from DENV challenge need to be further investigated.