FIG. 6.
Model for the proposed mechanism of action of palivizumab and motavizumab. The diagram shows proposed progression of the conformational changes in F protein that are proposed to fuel the process of fusion (28). The attachment assay results showed that palivizumab and motavizumab did not inhibit the transition from the prefusion to prehairpin conformation. The lipid-mixing assay results suggest that palivizumab and motavizumab do not inhibit the transition to either the prehairpin or hairpin conformations, as described in the text. The virus transcription assay and the cell-to-cell fusion assay showed that palivizumab and motavizumab inhibited fusion at either the transition from the prehairpin-to-hairpin conformation or the hairpin-to-postfusion conformation. HR-N and HR-C denote the F protein N-terminal and C-terminal heptad repeats, respectively.