COMPARISON OF FUSION PHAGE LIBRARIES DISPLAYING V-H OR SINGLE-CHAIN FV ANTIBODY FRAGMENTS DERIVED FROM THE ANTIBODY REPERTOIRE OF A VACCINATED MELANOMA PATIENT AS A SOURCE OF MELANOMA-SPECIFIC TARGETING MOLECULES

A single-chain Fv (scFv) fusion phage library derived from random comb inations of V-H and V-L (variable heavy and light chains) domains in t he antibody repertoire of a vaccinated melanoma patient was previously used to isolate clones that bind specifically to melanoma cells, An u nexpected finding was that one of the clones encoded a truncated scFv molecule with most of the V-L domain deleted, indicating that a V-H do main alone can exhibit tumor-specific binding, In this report a V-H fu sion phage library containing V-H domains unassociated with V-L domain s was compared with a scFv fusion phage library as a source of melanom a-specific clones; both libraries contained the same V-H domains from the vaccinated melanoma patient, The results demonstrate that the clon es can be isolated from both libraries, and that both libraries should be used to optimize the chance of isolating clones binding to differe nt epitopes. Although this strategy has been tested only for melanoma, it is also applicable to other cancers. Because of their small size, human origin and specificity for cell surface tumor antigens, the V-H and scFv molecules have significant advantages as tumor-targeting mole cules for diagnostic and therapeutic procedures and can also serve as probes for identifying the cognate tumor antigens.