Critical factors for liposome-incorporated tumour-associated antigens to induce protective tumour immunity to SL2 lymphoma cells in mice

Abstract

Physical and immunogenic properties of reconstituted membranes designed for the presentation of tumour-associated antigens (TAA) to the immune system are described. Proteins and lipids of crude membranes of SL2 murine lymphosarcoma cells were partially solubilized with octylglucoside. Reconstituted membranes, consisting mainly of unilamellar vesicles with a diameter of 0.03-0.15 microns, were formed by detergent removal and were purified by floatation in a discontinuous sucrose gradient to remove non-lipid-bound protein. Subcutaneous immunization of syngeneic mice with reconstituted membranes or with purified reconstituted membranes induced protection against an intraperitoneal challenge with 10(3) viable SL2 cells. Reconstituted membranes were more immunogenic than crude membranes in immunoprotection experiments when compared on the basis of protein dose. Detergent removal was required to obtain an immunogenic presentation form of SL2 membrane antigens and to avoid toxicity associated with the detergent. Reconstitution of SL2 membranes in the presence of exogenous phospholipid slightly increased the fraction of protein that associated with the reconstituted membranes. However, the immunogenicity of the solubilized membrane TAA was not significantly affected by the presence of exogenous phospholipid. The reconstitution procedure described may be useful in identifying membrane factors required for the induction of immune responses against TAA. The versatility of the system may be employed to develop safe alternatives for whole-cell vaccines.

Effect of immunomodulators on specific tumor immunity induced by liposome‐encapsulated tumor‐associated antigens

“…The vesicles were mainly unilamellar, with diameters of about 0.1 pm. These and other physical and chemical properties of the reconstituted membranes have been described (Bergers et al, 1993~). The feasibility of using reconstituted membranes for cancer vaccines and the importance of antigen presentation was demonstrated by the following observations made in the syngeneic SL2 (a spontaneously arisen, weakly immunogenic tumor)/DBA2 model: (1) reconstituted membranes were more immunogenic than crude membranes; (2) detergent removal was required to obtain an immunogenic presentation form of SL2 antigens; (3) immune responses were systemic and specific; and (4) additional phospholipid could be added without affecting the protective tumor immunity.…”