PREPARATION OF MUC-1 OLIGOMERS USING AN IMPROVED CONVERGENT SOLID-PHASE PEPTIDE-SYNTHESIS

The sequentially repeating nature of the core mucin polypeptide chain MUC-1 on the surface of malignant cells makes it an excellent target f or cancer immunotherapy. We describe a reliable and efficient method o f synthesizing oligomers, up to five tandem repeats and oligomer heter otope derivatives with a 15-amino acid epitope from tetanus toxin usin g an improved convergent solid-phase peptide synthesis. The different oligomers were easily distinguishable by reverse-phase high pressure l iquid chromatography, but they were poorly fixed and migrated with the same migration rate, irrespective of size, in electrophoretic studies . In contrast, the oligomer heterotopes exhibited size-dependent elect rophoretic behavior but in high pressure liquid chromatography chromat ograms the different heterotopes were eluted simultaneously in two pea ks representing the L-and D-enantiomers of the derivatives. The oligom er heterotopes were recognized as antigens in Western blotting with a murine monoclonal antibody against the epitope APDTR, In enzyme immuno assay studies with the same antibody an increasing reactivity was obse rved against the larger oligomers and confirmed by inhibition assays a s the MUC-1 pentamer was the most efficient inhibitor. These results s upport the suggestion that the pentamer attains a structure closer to the native conformation and is more immunogenic. In conclusion, large composite peptides can be reliably synthesized with the convergent sol id-phase peptide strategy offering an attractive option to vaccine des igning and development.