The research work entitled “Structural basis for neutralization of Japanese encephalitis virus by two potent therapeutic antibodies” was published on line in the journal of Nature Microbiologyon January 29, 2018. Using a combination of structural analysis, cellular assays and animal studies, scientists have identified the location of epitopes targeted by the antibodies and neutralizing mechanisms, which extends our understandings of the structural and molecular basis for the application of 2F2 and 2H4 that treat JEV infection.

JEV infection sometimes progresses into fatal neurological diseases.About 30% of Japanese encephalitis cases are fatal and 50% result in permanent neuropsychiatric sequelae. To date, no effective anti-viral drugs for treatment of infections caused by JEV are available. Therefore, it is very important to develop new vaccines and drugs to deal with JE.We revisited two “old” monoclonal antibodies (mAbs) reported by the Fourth Military Medical Universityin the 1980s in order to study the mechanism of neutralization of JEV by these antibodies at the atomic level.Both antibodies, 2F2 and 2H4, were reported to enhance survival rates of animals, including mice, goats and monkeys inoculated with JEV. However, molecular details of the mechanism of neutralization of JEV by these antibodies are unknown.

Here we demonstrate that JEV-specific monoclonal antibodies, 2F2 and 2H4, block the attachment of the virus to its receptor and also prevent fusion of the virus. Neutralization of JEV by these antibodies is exceptionally potent and confers clear therapeutic benefit in mouse models. A single 20 μg dose of these antibodies resulted in 100% survival and complete clearance of JEV from the brains of mice. The 4.7 angstrom and 4.6 angstrom resolution cryo-electron microscopy (cryo-EM) structures of JEV-2F2-Fab and JEV-2H4-Fab complexes, together with the crystal structure of 2H4 Fab and our recent near-atomic structure of JEVunveil the nature and location of epitopes targeted by the antibodies. Both 2F2 and 2H4 Fabs bind quaternary epitopes that span across three adjacent envelope proteins. Key interactions of the antibodies with JEV were verified using mutagenesis. Our results provide structural and molecular basis for the application of 2F2 and 2H4 that treat JEV infection.

Professor WANG Xiangxi at the Institute of Biophysics (IBP) of the Chinese Academy of Sciences, Professor Xuzhikai at the Fourth Military Medical University, in cooperation withProfessor RAO Ziheare correspondingauthors.This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the Ministry of Science and Technology 973 Project.

Article linkage: https://www.nature.com/articles/s41564-017-0099-x

By Zihe Rao research group