Selection of an anti-CD20, single-chain antibody by phage ELISA on fixed cells.

Cloning the correct genes that code for antibody-variable domains from hybridomas is often complicated by the presence of several immunoglobulin transcripts, some of them arising from a myeloma cell line. For the rapid functional evaluation of recombinant antibody fragments against cell-surface antigens, we established an efficient expression and screening system using phagemid antibodies and fixed cells. VL and VH-polymerase chain reaction (PCR) products, amplified from hybridoma cDNA, were cloned into the phagemid vector pSEX81. After transduction into E. coli and phage rescue, clones were tested for antigen binding using a phage-enzyme-linked immunosorbent assay (ELISA) procedure with whole cells fixed to ELISA wells. This procedure facilitated the successful cloning of a functional anti-CD20, single-chain antibody from hybridoma cDNA. The CD20 B-lymphocyte surface antigen expressed by B-cell lymphomas is an attractive target for cancer treatment using immunoconjugates or bi-specific antibodies.