A cell surface-displayed anti-c-myc single-chain antibody: new perspectives for the genetic improvement of cellular tumor vaccines

We have shown recently that cell surface-bound, single-chain Fv antibodies (scFv) are a powerful tool for the improvement of cellular tumor vaccines. To simplify this approach and to develop a general tool for the generation and improvement of cellular tumor vaccines, we chose an scFv against a peptide from the human proto-oncogene c-myc that could anchor any c-myc-tagged protein to the cell surface. The retroviral vector p50-Mx-neo (pMESV) was used to express scFv on the surface of the human melanoma line SkMel63. The cell-bound anti-c-myc scFv bound specifically to a soluble purified anti-CD28 scFv carrying a c-myc peptide-tag at its C terminus. Proof of principle was determined by incubating human peripheral blood lymphocytes with a mixture of (a) anti-c-myc-transfected SkMel63 cells binding the anti-CD28 scFv and (b) SkMel63 cells transfected with an anti-CD3 scFv. A clear synergistic effect on T-cell activation was observed that was comparable with that obtained in previous studies using SkMel63 cells transfected with the gene for the anti-CD28 scFv. As the cell surface-displayed anti-c-myc scFv can bind any c-myc-tagged protein of interest, this technique facilitates the genetic engineering of cellular vaccines for the therapy of virtually all human neoplasias.