Cytotoxicity induced by monoclonal antibody to alpha-fetoprotein coadministered with spleen cells of nude mice

Use of blue-sepharose for purification of immunotoxin containing type 1 ribosome-inactivating protein, gelonin

This paper describes a method suitable for purifying immunotoxin containing type 1 ribosome-inactivating protein, gelonin. The separation of free (unreacted) 80G, a monoclonal antibody against alpha-fetoprotein (AFP), from semipurified 80G-gelonin conjugate was unsuccessful by conventional CM-Sepharose ion-exchange chromatography because the isoelectric point of the conjugate did not increase enough to reach that of gelonin alone. In contrast, Blue Sepharose affinity chromatography could efficiently separate free 80G from the semipurified conjugate because the conjugate was bound to the column by its gelonin moiety while free 80G was not in buffer containing NaCl of a particular concentration range. However, a small amount of conjugate containing gelonin modified with N-succinimidyl 3-(2-pyridyldithio)propionate, but not with 2-iminothiolane, could not bind to the column. The conjugate purified by the use of Blue Sepharose showed selective cytotoxicity against AFP-producing human hepatoma cells.

Immunotoxins composed of monoclonal antibody to alpha-fetoprotein and gelonin as a potent hepatoma-targeted drug delivery system

This study was carried out to evaluate our monoclonal antibody (MoAb) to alpha-fetoprotein (AFP), 80G, as a carrier for targeting AFP-producing hepatoma. Pharmacokinetic analysis showed that the MoAb 80G was actively incorporated into AFP-producing HuH-7N cells (xenograft of human hepatoma cell line, HuH-7) in nude mice. Four conjugates composed of MoAb 80G, and a type 1 ribosome-inactivating protein, gelonin, were prepared. They involve two disulfide-linked and two thioether-linked conjugates. The binding activity of conjugates against AFP remained as high as that of intact 80G according to enzyme-linked immunosorbent assay. The in vitro cytotoxic effects of all the conjugates were specific against AFP-producing HuH-7 cells. Of these conjugates, two containing gelonin modified with 2-iminothiolane were more potent than the others. They showed significant antitumor activity upon AFP-producing HuH-7N cells in nude mice. However, the disulfide conjugate was more toxic to mice than the thioether conjugate judging from the loss in body weight and the liver damage. These results suggest that our MoAb 80G is a suitable carrier for targeting AFP-producing hepatoma cells, and that the noncleavable thioether conjugate is promising as an AFP-producing hepatoma-targeted drug delivery system.