GENERATION OF THE SINGLE-CHAIN ANTIBODY FRAGMENT CONSERVES THE IDIOTYPIC PROFILE OF THE ANTI-CD30 MONOCLONAL-ANTIBODY HRS3

Recombinant single chain antibody fragments (scFv) derived by combinin g immunoglobulin VL and VH regions provide valuable antibody-like reag ents. A number of them are shown to have retained the antigen specific ity of the parental monoclonal antibody (MoAb). Little is known about the idiotypic profile of scFv fragments compared with that of the pare ntal MoAb. To address this question we analysed the idiotypic profile of a scFv that was derived by phage-display techniques from the anti-C D30 MoAb HRS3. We assayed (i) binding of HRS3-scFv to recombinant CD30 -Fc antigen and to four different anti-idiotypic MoAbs defining at lea st three different idiotopes on HRS3, and (ii) cross-competition with the parental MoAb HRS3 and the closely related anti-CD30 MoAb HRS4. Th e assays revealed that the HRS3-scFv fragment exhibits the same specif icity for both CD30 antigen and the tested anti-idiotypic MoAbs compar ed with the parental MoAb demonstrating that the recombinant scFv frag ment has retained the complete idiotope of the parental MoAb.