Isolation of human tumor-specific antibodies by selection of an antibody phage library on melanoma cells

A human single-chain Fv (scFv) library as fusion to phage was constructed f rom donors with a high titer of autoantibodies. The library was subjected t o three rounds of positive selection on human melanoma cells and negative s election on human peripheral blood mononuclear cells, Two scFv clones, B3 a nd B4, were isolated that bound melanoma cells in cell ELISA and fluorescen ce-activated cell sorting. The scFvs were characterized further by immunohi stochemistry on a large number of normal human tissues. No cross-reactivity with normal tissues was observed. On the other hand, the target antigens w ere expressed in sections from several different melanoma patients and in s ome breast cancer and basal cell carcinoma sections. The unusually high tum or specificity of the B3 and B4 antigens makes them attractive targets for the specific therapy of melanoma, The selection strategy used should be gen erally applicable to the identification of novel cell surface antigens by a ntibody phage display.