FUSION-MEDIATED MICROINJECTION OF LYSOZYME INTO HEPG2 CELLS THROUGH HEMAGGLUTININ NEURAMINIDASE-DEPLETED SENDAI VIRUS ENVELOPES

The potential of reconstituted Sendai viral envelopes containing only the fusion protein (F-virosomes) was evaluated for a targeted cytosoli c delivery of lysozyme to human hepatoblastoma cells (HepG2) in cultur e. I-125-Lysozyme loaded into F-virosomes was used to monitor its fusi on-mediated transfer to the HepG2 cells. Using fusion assay based on t he transfer of water soluble probe, we have demonstrated the existence of aqueous connection between F-virosomes and target cells. Target sp ecificity of the F-virosomes was ensured by the strong interaction bet ween terminal 6-galactose moiety of F protein and the asialoglycoprote in receptor on the membrane of HepG2 cells. Incubation of the loaded F -virosomes with cells resulted in fusion-mediated injection, as inferr ed from the ability of cells to internalize lysozyme in the presence o f azide (an inhibitor of the endocytotic process). Binding as well as fusion of the F-virosomes to HepG2 cells was solely mediated by the F protein. Introduction of I-125-lysozyme into the HepG2 cells was confi rmed by selective accumulation of acid and antibody-precipitable radio activity in the cytosolic compartment. The structural integrity of the internalized lysozyme was also assessed. The potential usefulness of F-virosomes with defined specificities as biological carrier for both in vitro and in vivo cytosolic delivery of macromolecules and drugs ha s been established.