Immunospecific targeting of immunoliposomes, F(ab′) 2 and IgG to red blood cells in vivo

Abstract

In this report a model to study the fate of target cells in the blood circulation after injection of appropriate immunoliposomes is discussed. The effect of intravenous administration of antimouse RBC immunoliposomes, F(ab′) 2 or IgG on the fate of intravenously injected 51Cr-labelled mouse RBC (Cr-mRBC) in the mouse and, particularly, in the rat was studied. The immunoliposome was of the Fab′-MPBPE-REV type (Fab′-fragments covalently linked to reverse phase evaporation vesicles by maleimido-4-( p-phenylbutyrate)phosphatidylethanolamine). In the rat model a high blood level (80%) of the injected dose of target cells, Cr-mRBC, was maintained for several hours. The elimination by Fab′-liposomes, F(ab′) 2 or IgG of Cr-mRBC, and subsequent uptake into liver and spleen was dose dependent. Administration of Fab′-liposomes or F(ab′) 2 resulted in a preferential uptake into the spleen (above a certain dose also, but much lower, uptake into the liver was observed), while after IgG administration 51Cr-label was mainly recovered in the liver. At equal protein doses (± 130 μg) Fab′-liposomes induced a faster elimination of the Cr-mRBC and a higher uptake into the spleen than F(ab′) 2. The potential advantage of the use of drug-loaded immunoliposomes to eliminate target cells from the blood stream and to induce a certain pharmacological effect in the target cells, in comparison with the free antibody administration of F(ab′) 2 or IgG is discussed.