Structural elucidation of the interactions between F glycoprotein and palivizumab.

(a) Predicted structure of the RSV-A postfusion F glycoprotein (PDB: 3RRT) bound to palivizumab Fab fragment (PBD: 2HWZ). Pink dots, antigenic site II (amino acid residues 258–275); upper panel, side view; lower panel, top view. (b) Predicted interface of polar inter-chain interactions between the RSV-A postfusion F glycoprotein antigenic site II and Fab fragment of palivizumab. The location of the four residues (Ala241, Val247, Asn276, Gln279) on the F glycoprotein for which mutations were observed in the Lebanese strains are shown. (c) Polar contacts by Asn276 in the RSV-A F glycoprotein vs (d) showing disappearance of a 2.3 Å polar bond with Tyr100 on Fab H chain due to the N276S substitution while maintaining the 2.9 Å polar bond with Tyr94. (e) Polar contacts by Ala241 in the RSV-A F glycoprotein vs (f) showing no changes of polar interactions with the A241V substitution. (g) Polar contacts by Val247 in the RSV-A F glycoprotein vs (h) showing no changes of polar interactions with the V247I substitution. (i) Polar contacts by Q279 in the RSV-B F glycoprotein vs (j) showing the appearance of a new 1.6 Å polar bond with Ala241 on an adjacent chain of the F glycoprotein due to the Q279H substitution. Yellow, palivizumab Fab heavy chain; orange, palivizumab Fab light chain; magneta, F glycoprotein F chain; blue, F glycoprotein E chain; green, F glycoprotein B chain; yellow dashed lines, polar contacts.