Selective cytotoxic effects of immunotoxin--monoclonal anti-AFP-abrin-A chain conjugate on several human hepatoma cell lines.

A highly specific monoclonal antibody (anti-AFP) against alpha-fetoprotein (AFP) was linked to N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) to form conjugates which were purified with a protein A-sepharose CL-4B affinity column. The conjugate, PDP-Anti-AFP was then covalently coupled to the toxic abrin-A chain to synthesize immunotoxins. The immunotoxin, anti-AFP-abrin-A conjugate, which was also purified with a protein A-sepharose CL-4B affinity column, had a molecular weight of 180,000 and had 80% antigen-binding activity that of anti-AFP activity and 92% toxicity of abrin-A chain. The immunotoxin showed selective cytotoxicities toward the AFP secreting human hepatoma cell lines, such HepG2 and Hep3B, but not toward AFP non-secreting human hepatoma cell line, PLC/PRF/5.