For the production of an effective liposomal vaccine, tumor surface antigenic proteins (TSAP) were directly transferred from BALB RVD leukemia cells to a lecithin liposome containing an artificial boundary lipid (DDPC, 1,2-dimyristoylamido-1,2-deoxyphospbatidylcholine). When DMPC (20 mol%)-DDPC (80 mol%) liposomes were employed the highest efficiency of membrane protein transfer was achieved. From studies of specific lectin-induced aggregation of the membrane protein-transferred liposome, saccharide moieties of proteins transferred were found to contain at least sialic acid, galactose, and mannose moieties. This membrane protein-transferred liposome showed significantly higher efficiency of macrophage uptake compared with the other two liposomes, namely no membrane protein-reconstituted liposome and liposome with proteins which were first extracted by butanol from turner cell and then reconstituted to liposome. Judging from results obtained, TSAP was considered to be certainly involved in membrane proteins transferred from the tumor cell to liposome. When mice were immunized by the TSAP-transferred liposome (liposomal vaccine) and subsequently challenged by BALB RVD, high CTL induction and excellent prevention of tumor growth were observed, as expected.
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