Construction of the single-chain Fv from 196-14 antibody toward ovarian cancer-associated antigen CA125

The variable regions of heavy- and light-chains of mouse monoclonal antibod y 196-14 toward ovarian cancer-associated antigen CA125 were linked with a peptide linker (GSTSGSGKSSEGKG) and a histidine tag was attached at the car boxyl terminal. This single-chain Fv (scFv) with a histidine tag was expres sed in Escherichia coli as an inclusion body The inclusion body was solubil ized with guanidium chloride, follow ed by purification on nickel nitrilotr iacetic acid agarose column and refolding into the active form, The scFv th us obtained bound to the Siso cells, which express CA125, and may recognize the same epitope as the parental 196-14 antibody IgG does.