Interactions of Sendai virus with liposome target membrane

A model system for the study of interactions of Sendai virus with target membranes has been developed using liposomes containing viral receptor gangliosides. The fluorescence quenching dye, calcein, was entrapped into liposomal aqueous compartment to monitor the kinetics of membrane permeability changes induced by the virus. An assay method employing ultracentrifugation with airfuge was also developed to monitor the kinetics of Sendai virus-liposome and other preceding events, i.e., binding steps. In order to interpret the results at a more fundanmental level, we simplified the liposome composition to only contain two lipids, i.e., phosphotidylethanolamine and ganglioside GD1a. The lipid packing of this target membrane has been characterized biophysically and was found to have a gel-liquid o crystalline phase transiton between 20 and 25%deg;C. Parallel temperature dependence studies have allowed us to correlate the physical parameters of target membrane, such as lipid stucture order, fluid vs gel phase, etc., to the fusion and leakage activities of the virus. Since Sendai virus induces fusion and membrane permeability changes are intuitively related, we also have investigated the relationship between these two events.