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Structural basis for neutralization of Japanese encephalitis virus by two potent therapeutic antibodies

Abstract

Japanese encephalitis virus (JEV), closely related to dengue, Zika, yellow fever and West Nile viruses, remains neglected and not well characterized1. JEV is the leading causative agent of encephalitis, and is responsible for thousands of deaths each year in Asia. Humoral immunity is essential for protecting against flavivirus infections and passive immunization has been demonstrated to be effective in curing disease2,3. Here, we demonstrate that JEV-specific monoclonal antibodies, 2F2 and 2H4, block 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 Å and 4.6 Å resolution cryo-electron microscopy 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 JEV4, unveil 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. Our results provide a structural and molecular basis for the application of 2F2 and 2H4 to treat JEV infection.

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Acknowledgements

We thank Y. Chen, Z. Yang and B. Zhou for SPR technical support; X. Huang, B. Zhu and Z. Guo for cryo-EM technical support; and M.S. Diamond, S. Lok and D. Stuart for providing comments on the paper. The cryo-EM datasets were collected at the Center for Biological Imaging, Institute of Biophysics; the X-ray diffraction datasets were collected at beam line BL18U of the Shanghai Synchrotron Facility. Work was supported by the Ministry of Science and Technology 973 Project (grant no. 2014CB542800); the National Key Research and Development Program of China (no. 2016YFC1200400); the National Science Foundation, grant no. 81330036, no. 31570717, no. 81171557 and no.81520108019; the Strategic Priority Research Program of the Chinese Academy of Sciences, grant no. XDB08020200; and US NIH grants R01 AI1 12381 and R21 AI09464. X.W. is supported by the Young Elite Scientist sponsorship of CAST and program C of “One Hundred Talented People” of the Chinese Academy of Sciences.

Author information

X.Q., Y.L., P.Y., N.W., Q.G. and X.Wa. performed the experiments; W.M., X.W., T.D. and F.Z. provided the reagents; X.Wa., Y.L., Z.X. and Z.R. designed the study; all authors analysed the data; and X.Wa., Y.L., Z.X., S.-L.L. and Z.R. wrote the manuscript.

Competing interests

The authors declare no competing financial interests.

Correspondence to Xiangxi Wang or Zhikai Xu or Zihe Rao.

Supplementary information

Supplementary Information

Supplementary Figures 1–15, Supplementary Tables 1–5 and Supplementary References.

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Further reading

Fig. 1: 2F2 and 2H4 are JEV-specific neutralizing antibodies of therapeutic value.
Fig. 2: Cryo-EM structures of JEV–2F2-Fab and JEV–2H4-Fab.
Fig. 3: Interactions between 2H4 Fab and three E proteins.
Fig. 4: 2F2 and 2H4 neutralize JEV by inhibiting attachment and fusion of JEV.