PREPARATION AND CHARACTERIZATION OF DIPALMITOYLPHOSPHATIDYLCHOLINE LIPOSOMES CONTAINING INTERLEUKIN-2

Human recombinant interleukin-2 (IL-2) has been associated or mixed wi th small unilamellar vesicles prepared from dipalmitoylphosphatidylcho line (DPPC). Whatever the mode of IL-2 introduction, a considerable pr oportion of the added protein was associated with the liposomes, as de termined by gel filtration and ultrafiltration/centrifugation, suggest ing that IL-2 can interact with the lipid bilayer as well as being ent rapped within the aqueous phase. Moreover, IL-2 prevented the aggregat ion/fusion of the vesicles at 4 degrees C. Liposome-associated protein was partially protected from digestion by pepsin, especially at the C -terminal, since no fluorescence emission from the tryptophan in this region was detected in the resulting peptides after separation by HPLC . Such systems could constitute a sustained release form of IL-2 for i mmunotherapy.