Recombinant human monoclonal igA antibody against CEA to recruit neutrophils to CEA-expressing cells

IgA is able to trigger antibody-dependent cellular cytotoxicity (ADCC) by recruiting neutrophils expressing the Fc receptor for the CHalpha chain. We herein describe the preparation of a human recombinant anti-CEA IgA antibody to kill carcinoembryonic antigen (CEA)-expressing tumor cells via ADCC by neutrophils. A single chain Fv (scFv) gene was constructed using a cDNA library of a hybridoma clone that produces a human anti-CEA monoclonal IgG4 (C2-45). The scFv gene, linked with a CHalpha gene, was inserted into the pBK283 vector, which was cotransfected into BmN4 insect cells with the wild-virus BmNPV. After cloning and amplification, the recombinated virus was injected into silkworm larvae. The resulting human recombinant IgA, designated as 45scFvLCHalpha, was purified from hemolymph by Ni-affinity chromatography and characterized by ELISA, Western blotting, and the ADCC assay. 45scFvLCHalpha with an IgA antigenicity was bound to CEA and showed effective killing of the CEA-expressing cells in the presence of IFN-gamma-activated neutrophils. These data suggest the recombinant anti-CEA IgA antibody recruiting neutrophils maybe a useful means for the antibody-based immunotherapy of human CEA-expressing tumors.