Permeability of phospholipid vesicles to the tumor antigen epitope gp100280-288

Peptidesderived from antigenic proteins can be used to generate or expand cytotoxic T lymphocytes(CTLs ) that target cellsinfected by virusor intracellular bacteria, or which are undergoing neoplastic transformation. While the simplest, riskfree administration route for exogenous peptides is intradermal injection, they can also be used for ex vivo pulsing of antigen- presenting cells (APCs) such as dendritic cells. Soluble peptides, however, are considered poor immunogens; among the multiple factors possibly involved, enzyme hydrolysis appears to be particularly important. Lipid vesicles, frequently composed of mixed phospholipids and containing cholesterol and/or polymer- bound lipids, have long been used as vehicles for the delivery of drugs, proteins, peptides, and nucleic acids. Among the factorscontrolling vesicle permeability, a relevant role is played by the size and polarity of the substance carried. Herein we verified the efflux of class I-restricted epitopes from sonicated vesicles composed of a single phospholipid, and the effect of thisparameter on the protection from enzyme hydrolysis provided by the vesicles. The peptide used as model was a tumor antigen epitope, the class I-restricted nonapeptide gp100280–288 (Tyr-Leu-Glu-Pro-Gly-Pro-Val-Thr- Ala), while cultured human fibroblasts were used as a source of enzymes.The permeability of lipid vesicles to gp100280–288 was verified by measuring the release of peptide by sonicated phospholipid vesicles.