It should be noticed that the phenomenon of hydrogen bonds and electrostatic interaction formed between R246 and antibody observed in the 7L2F is not unique. We noted that R246 in NTD is in close contact with glutamic acid in several antibodies, viz 4A8 (PDB ID: 7C2L), FC05 (PDB ID: 7CWS), 2-51 (PDB ID: 7L2C), 1-87 (PDB ID: 7L2D), with a mode similar to R246-D105 as highlighted in Figure . Because of the above reasons, R246I mutation will decrease the binding affinity to many antibodies.