Author contributions
Y.W. and W.H. conceived, designed, and supervised the experiments; M.C.
performed the neutralization assays; Z.H., J.Q., G.L. and F.Y. performed
12-2A12 crystallization, data collection and structure determination.
Y.Y., T.M. and Y.L completed 12-2A12 isolation and affinity
determination. M.C. and Z.H. wrote the manuscript; All authors approved
the final manuscript.