BINDING OF RAS ONCOGENE PEPTIDES TO PURIFIED HLA-DQ(ALPHA-1(ASTERISK)0102,BETA-1(ASTERISK)0602) AND HLA-DR(ALPHA,BETA-1(ASTERISK)0101) MOLECULES

Mutated oncogene peptides may be presented to T cells by HLA molecules . To be able to design the optimal peptides for stimulation of T cells in individuals with different HLA molecules, it is important to analy se the binding characteristics of oncogene peptides to HLA. HLA-DQ6 {D Q(alpha 10102,beta 1*0602)} and HLA-DR1 {DR(alpha,beta 1*0101)} molec ules were purified from lysates of homozygous EBV-transformed cell lin es. Purified HLA molecules were then tested for their ability to bind synthetic peptides in gel filtration assays. A p21 ras oncogene peptid e (previously found to stimulate DQ6-restricted T-cell clones) and an influenza matrix peptide were labelled with I-125 and served as indica tor peptides for binding to DQ6 and DR1 respectively. Binding of homol ogous truncated and mutated p21 ras peptides and unrelated peptides wa s then evaluated by their capacity to inhibit binding of the indicator peptides. p21 ras-derived peptides were found to bind to both DQ6 and DR1 molecules indicating the existence of a promiscuous binding motif in these peptides. The binding affinities seemed to vary between the different peptides, but the amino acid substitutions resulting from na tural mutations were not critical for binding. Notably, the results ob tained for DQ6 in the biochemical peptide binding assay correlated wel l with results obtained in a functional assay using T-cell clones as p robes.