Kinetics and Extent of Fusion of Viruses with Target Membranes

This chapter describes procedures for analyzing fusion experiments. The results of fusion studies among influenza and Sendai viruses and liposomes, erythrocyte ghosts, and suspension cells are presented. The mass action model for membrane fusion views the overall fusion reaction as the sequence of a second-order process of liposome liposome, virus–liposome, or virus–cell adhesion or aggregation, followed by a first-order fusion reaction. The analysis of the final extent of fluorescence intensity can yield the percentage of virions capable of fusing with certain target membranes at a given pH. The analysis of the kinetics of fusion enables gauge the extent that the action of viral glycoproteins goes beyond the promotion of contact between apposed membranes. The analysis of final extents of fusion of influenza virus (at pH 5) and Sendai virus (above pH 7.5) with nonendocytosing suspension cells indicates that all virus particles can fuse if the number of virions per cell is not large.