ISOLATION OF SINGLE-CHAIN ANTIBODY FRAGMENTS WITH SPECIFICITY FOR CELL-SURFACE ANTIGENS BY PHAGE DISPLAY UTILIZING INTERNAL IMAGE ANTIIDIOTYPIC ANTIBODIES

Recombinant single chain antibody fragments (scFv) with specificity fo r membrane-bound antigens can be isolated by phage display techniques. The strategy involves selection of recombinant phage antibodies by bi nding to cells expressing the respective antigen. This results frequen tly in high nonspecific adherence of phages to cellular membranes. To resolve the problem we have made use of an internal image anti-idiotyp ic antibody mimicking the membrane-bound CD30 antigen and successfully isolated scFv fragments with specificity for CD30. The cDNA coding fo r the immunoglobulin heavy and light chain variable regions of the ant i-CD30 monoclonal antibody (mAb) HRS3 was expressed by phage display t echniques. Recombinant HRS3-scFv phages were efficiently enriched by o ne cycle of panning on the internal image anti-idiotypic mAb 9G10. The isolated HRS3-scFv clone retained the binding specificity of the pare ntal mAb HRS3 to the internal image anti-idiotypic mAb 9G10 as well as to an anti-idiotypic mAb without the internal image. Furthermore HRS3 -scFv reacted with recombinant and cell-bound CD30 antigen, respective ly. Binding of scFv fragments to anti-idiotypic mAbs will provide a ve rsatile strategy for the efficient isolation of recombinant antibody f ragments. (C) 1998 Elsevier Science B.V. All rights reserved.