Production of a single chain anti-CEA antibody from the hybridoma cell line T84.66 using a modified colony-lift selection procedure to detect antigen-positive ScFv bacterial clones.

Recombinant single chain Fv (scFv) antibodies offer many advantages over mouse monoclonal antibodies (MAbs) such as faster clearance from blood, improved tumor localization, reduced human anti-mouse antibody (HAMA) response, and the availability to manipulate the scFv through genetic approaches. The scFv antibody (designated RK10.2) was generated using anti-CEA T84.66 hybridoma cells as a source of genetic starting material and the Pharmacia Recombinant Phage Antibody System (RPAS). Escherichia coli clones expressing antigen-positive soluble scFv were identified using a modified colony-life selection procedure and antigen-coated filters. The resultant anti-CEA scFv (designated RK10.2) had a molecular weight of approximately 33.6 kDa and an isoelectric point of 5.2 at 15 degrees C. The RK10.2 scFv interacted with LS174 T cells bearing the CEA antigen and inhibited the anti-CEA MAb/CEA antigen interaction in ELISA and the anti-CEA MAb/LS174 T cell interaction in a RIA. The modified colony-lift approach circumvented the more time-consuming phage-display approach that is normally taken to affinity select for antigen-positive scFv clones.