DELIVERY OF MACROMOLECULES INTO CYTOSOL USING LIPOSOMES CONTAINING HEMOLYSIN FROM LISTERIA-MONOCYTOGENES

The cytosolic space of cells is an important but relatively inaccessib le target for the delivery of therapeutic macromolecules. Here we desc ribe the efficient delivery of macromolecules into the cytosolic space of macrophages from liposomes that contain listeriolysin O (LLO), the hemolytic protein of Listeria monocytogenes that normally mediates ba cterial passage from phagosomes into cytosol, LLO was purified and enc apsulated inside pH-sensitive liposomes, along with other molecules to be delivered, When internalized by bone marrow-derived macrophages, t hese liposomes rapidly released encapsulated fluorescent dye, first in to endosomes and then into the cytosol, without measurably harming the cells. Furthermore, these liposomes efficiently delivered encapsulate d ovalbumin to the cytosolic pathway of antigen processing and present ation, as measured by the major histocompatibility complex (MHC) class I-restricted presentation of peptides derived from ovalbumin. Deliver y was significantly better than that obtained by other currently avail able liposome formulations, LLO-containing liposomes should therefore provide an efficient vehicle for delivery of antigens or therapeutic m olecules in vivo.