PRODUCTION OF ENGINEERED IGM-BINDING SINGLE-CHAIN ANTIBODIES IN ESCHERICHIA-COLI

Two single-chain antibodies were engineered and tested as novel bindin g proteins with specificity for immunoglobulin M. Genes for the two si ngle-chain Fv proteins were assembled from the variable light chain cD NA and variable heavy chain cDNA of monoclonal antibodies DA4.4 and Be t 2, which specifically bind human ISM and mouse IgM, respectively. Bo th single-chain Fv proteins were designed with a 14-amino acid linker which bridged the variable light chain and variable heavy chain domain s. The two proteins were expressed in Escherichia coli, purified and a ssayed for IgM-binding activity. Both proteins demonstrate a binding s pecificity for their corresponding IgM which is similar to the monoclo nal antibodies from which they were derived. These small ISM-binding p roteins may have applications in the investigation of the immune respo nse and in the detection and purification of monoclonal antibodies, ce ll-associated antibodies, and IgM from serum.