Phage-display library selection of high-affinity human single-chain antibodies to tumor-associated carbohydrate antigens sialyl Lewis(x) and Lewis(x)

mAbs against tumor-associated carbohydrate antigens have the potential to p lay a prominent role in cancer immunotherapy, However, it has not been poss ible to fully exploit the clinical utility of such antibodies primarily, be cause those of adequate affinity could be derived only from murine sources. To address this problem, we prepared a single-chain Fv (scFv) antibody lib rary from the peripheral blood lymphocytes of 20 patients with various canc er diseases. Completely human high-affinity scFv antibodies were then selec ted by using synthetic sialyl Lewis(x) and Lewis(x) BSA conjugates, These h uman scFv antibodies were specific for sialyl Lewis(x) and Lewisx, as demon strated by ELISA, BIAcore, and flow cytometry binding to the cell surface o f pancreatic adenocarcinoma cells. Nucleotide sequencing revealed that at l east four unique scFv genes were obtained. The Kd values ranged front 1.1 t o 6.2 x 10(-7) M that were comparable to the affinities of mAbs derived fro m the secondary immune response. These antibodies could be valuable reagent s for probing the structure and function of carbohydrate antigens and in th e treatment of human tumor diseases.