Modifications of an immunodominant peptide antigen induce different anti‐polyoma tumor responses in two separate mouse strains

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Abstract
An immunodominant polyoma peptide antigen MT162‐176 was modified with regard to amino acid (aa) composition in an attempt to analyze its immunogenicity in detail. Twelve modifications of peptide MT 162‐176, 3 overlapping peptides and 9 peptides with point mutations, were synthesized and used for immunizations of (A.CA x C57BL/6)F1 and CBA mice against the syngeneic polyoma tumors SECA and SEBA All 3 overlapping peptides MT 162‐176, MT165‐174 and MT 170‐176, were immunogenic in (A.CA x CS7BL/6)F1 mice against SECA, indicating that possibly more than one immunogenic epitope may be recognized within the MT 162‐176 sequence. In CBA mice, the 2 peptides covering the C‐terminal half were immunogenic against SEBA, while the N‐terminal peptide was possibly somewhat less efficient. The peptides with aa point mutations induced different anti‐tumor responses in the 2 mouse strains. In CBA mice, only one mutant, MT162‐176.28, was immunogenic. For (A.CA x C57BI)F1 3 different mutants, MTI62176.29, MTI62‐I76.35 and MTI62‐I76.36 were immunogenic against SECA, while the remaining 6 had lost their activity. These results suggest that a different emphasis of recognition of peptide MT 162‐176 exists with regard to the 2 mouse strains examined. Furthermore, different immunization procedures were tested. We found that repeated immunizations with peptide without Freund's adjuvant was the most efficient. © 1992 Wiley‐Liss, Inc.