5101

The disialoganglioside GD2 is an established target for neuroblastoma immunotherapy. To overcome poor antigenicity of the glycolipid GD2, we changed the nature of the antigen into peptides mimicking the structure of GD2, i.e. GD2 mimotopes. The efficiency of mimotope-based active vaccination strategies inducing protective anti-neuroblastoma immunity was already demonstrated in animal experiments.

In order to also achieve therapeutic success with such a vaccination approach, GD2 mimotopes were improved. First, two peptide mimotope sequences MA and MD identified by phage-display experiments were used for a progression of peptide substitutional analyses. For this purpose each amino acid of the MA and MD sequences was sequentially replaced by all other gene encoded amino acids. The substitutional analyses were prepared as cellulose membrane bound peptide arrays and subsequently tested for anti-GD2 MAB ch14.18 binding. The most promising candidate was chosen for the next substitutional analysis round. The best peptide candidates were synthesized and binding affinities to the anti-GD2-mAb ch14.18 were determined as dissociation constants (KD) by surface plasmon resonance studies. This approach resulted in an improved novel peptide (C3) with a more than five-fold increased affinity to ch14.18, compared to the wild type peptide.

Second, an alternative phage-display library independent approach was developed by the adoption of computer aided docking experiments. The criteria is design of an energetically optimal paratope structure of the anti-idiotypic-mAb 1A7 fitting into the corresponding binding domain of ch14.18. The peptide analysis allowed the construction of a stress reduced 3-dimensional model of the variable domain of ch14.18 and the nominal antigen GD2.

These results demonstrate two promising new approaches for the identification of peptide mimotopes for cancer immunotherapy.

Supported by DFG Lo 635-2 and Fördergesellschaft Kinderkrebs-Neuroblastom-Forschung

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA

American Association for Cancer Research
2007