Targeting of poly(rI)-poly(rC) by fusogenic (F protein) immunoliposomes.

The aim of this study is to investigate the intracellular delivery of polynucleotides by fusogenic immunoliposomes. We have studied the internalization of poly(rI)-poly(rC) (polyIC) by liposomes into murine L929 cells. The liposomes were prepared by incorporating Sendaï virus fusogenic F protein into the lipid bilayer and targeted by a monoclonal antibody (mAb) bound to the liposomes via protein A (Staphylococcus aureus). The immunoliposomes ensured a sufficient yield of polyIC internalization, which was estimated by its ability to induce antiviral activity. In the absence of RNase treatment free and encapsulated polyIC had the same inducing effect, but in the presence of nuclease only the encapsulated polyIC, and not free polyIC, maintained its antiviral effect. The fusion process making possible the internalization of polyIC was confirmed by the fact that the polyIC effect was mainly inhibited by an anti-F protein mAb which inhibited erythrocyte hemolysis by the virus.