DEVELOPMENT AND CHARACTERIZATION OF 3 RECOMBINANT SINGLE-CHAIN ANTIBODY FRAGMENTS (SCFVS) DIRECTED AGAINST THE CD19 ANTIGEN

Antibodies that recognize antigens restricted to leukemia, lymphoma, a nd normal hematopoietic cells represent a unique opportunity to develo p therapeutics, because they have the potential for relatively selecti ve treatment of these diseases, Antibodies that recognize the CD19 ant igen found on normal and malignant B cells, but not on stem cells, hav e been used to develop immunoconjugates, However, these conjugates are large and might be suboptimal in tumor penetration when compared to m olecules using smaller single chain Fv (scFv) antibody fragments, scFv has the advantage of being a molecularly engineered homogeneous molec ule, Ln this report, we demonstrate the cloning, expression, and bindi ng of three anti-CD19 antibodies as scFvs. All three scFvs were succes sfully cloned and expressed, FVS191, derived from cell line B43, and F VS192, derived from SJ25C1, were properly refolded and bound CD19 anti gen in FAGS competition assays, These anti-CD19 scFv should be useful in the further development of diagnostic and therapeutic molecules.