ENHANCEMENT OF INVIVO AND INVITRO T-CELL RESPONSE AGAINST MEASLES-VIRUS HEMAGGLUTININ AFTER ITS INCORPORATION INTO LIPOSOMES - EFFECT OF THE PHOSPHOLIPID-COMPOSITION

Artificial phospholipid bilayer vesicles were tested for their capacity to enhance the priming and the restimulation of mouse T cells against the haemagglutinin (H) glycoprotein of the measles virus in vivo and in vitro. H glycoprotein was purified and incorporated into liposomes made of cholesterol, dicetylphosphate and dilauroylphosphatidylcholine (DLPC) or distearoylphosphatidylcholine (DSPC). H in DLPC or DSPC-liposomes was found to be a potent in vivo stimulator of lymph node T cells harvested from mice immunized with measles virus, whereas H glycoprotein in free form did not elicit any proliferative T cell response. When used to immunize naive mice, only H in DSPC-liposomes was able to prime T cells as evidenced by the capacity of lymph node cells to proliferate in the presence of H in liposomes or measles virus as secondary stimulating agents in vitro. H-specific T cell clones derived from animals immunized with H in DSPC-liposomes were able to recognize H glycoprotein both in free form and incorporated into liposomes in the presence of naive spleen cells as APC. However, compared with the liposome forms, 20-fold more H protein in free form was required to elicit a T cell clone response at a similar level. This liposome immune enhancing effect on the T cell clone recognition of H glycoprotein was also observed when peritoneal exudate cells were used as APC. These data demonstrate that the insertion of a membrane-derived antigen into artificial membranes may be a prerequisite for the priming and stimulation of specific T cells both in vivo and in vitro. In addition, the nature of the phospholipid used to build the liposomes appears to be a critical parameter.