CHEMICALLY-INDUCED PLASMA-MEMBRANE VESICLES AS A USEFUL TOOL FOR THE INVESTIGATION OF VIRUS BINDING TO SUSCEPTIBLE CELLS

Binding to the surface of susceptible cells, the initial step of viral infections, represents an yet poorly understood event in the case of alphaviruses. In intact cells, the binding per se can only be studied when endocytosis is inhibited, e.g., at low incubation temperatures. H owever, nonphysiologically low temperatures may give only an imperfect picture of the events taking place at the cell surface during binding . In this report we present the application of chemically induced plas ma membrane vesicles (PMV) for binding studies. PMV produced overnight from Vero cells give high yields of homogeneous vesicles. PMV represe nt cellular plasma membranes as far as protein composition and enzyme activities are concerned, but are not competent for endocytosis. Bindi ng experiments to PMV were performed using Semliki Forest virus (SFV), a prototype of alphaviruses. The results show that the binding sites at the PMV surface are saturable and not competed by bovine serum albu min. Binding appeared to be specific and biologically relevant since f usion between viral and PMV membranes could be induced by lowering the incubation pH. Our model is of general interest since many cell types that are susceptible to viral infection may be induced to release PMV after adapting the method.