Table I.

Summary of relative HLA-A2 binding and antigenic activities of natural and modified Melan-A/MART-1 peptides

PositionaSubstitutionAmino Acid SequenceA2 BindingbAntigenic Activityc
27–35AAGIGILTV+/−+
27–35A28LALGIGILTV+Reduced
26–35EAAGIGILTV+/−++
26–35A27LELAGIGILTV++++ or more
• a Position of the peptide sequence in the Melan-A/MART-1 gene product.

• b The relative HLA-A2 binding activity is arbitrarily assigned as +/− to indicate intermediate to low binding activity as assessed in indirect assays of binding (8 ,9 ). One + indicates an increase in that activity of ∼1 order of magnitude.

• c The relative antigenic activity is arbitrarily assigned as + for the natural Melan-A/MART-1 nonapeptide and corresponds to ∼10–100 nM peptide concentration that causes half maximal lysis in a 4-h chromium release assay using T2 as target cells. Each extra + indicates an ∼10-fold decrease in this concentration. This decrease in the concentration of peptide required to obtain an equivalent level of cytolytic function corresponds to an increase in the efficiency of Ag recognition by specific CTL clones or polyclonal populations (9 ).