Method for the preparation of bispecific F(ab′)2μ fragments from mouse monoclonal antibodies of the immunoglobulin M class and characterization of the fragments

Bispecific F(ab')2 mu, fragments (Bs F(ab')2 mu) binding simultaneously both sialyl Lewis A antigen (SLA) and human carcinoembryonic antigen (CEA) were prepared by disulfide bond exchange between F(ab')2 mu, fragments derived from IgM monoclonal antibodies (mAbs) against SLA and CEA, and were purified to homogeneity in a one-step procedure of hydrophobic interaction HPLC. The final yield of Bs F(ab')2 mu from F(ab')2 mu fragments was 70-78%, and the purity was higher than 98%. The immunoreactivities of the Bs F(ab')2 mu fragments against SLA and CEA were almost the same as those of the respective parental F(ab')2 mu, fragments. The dissociation constant (0.17 mu M) of the Bs F(ab')2 mu, for CEA was in good agreement with that of the parental F(ab')2 mu, fragments. Although the number of applications of IgM mAbs is restricted because of the large molecular mass and low solubility, Bs F(ab')2 mu might, nevertheless, be a useful tool for immunotherapy and immunodiagnosis. (C) 1999 Elsevier Science B.V. All rights reserved.