2236041

pubmed:Citation

21

Anti-Tac(Fv)-PE40 is a recombinant single-chain immunotoxin containing the heavy and light variable regions of the anti-Tac monoclonal antibody fused to a mutant form of Pseudomonas exotoxin (PE). Anti-Tac binds to the p55 subunit of the human interleukin 2 (IL-2) receptor, and anti-Tac(Fv)-PE40 kills human or monkey cell lines that contain either the intact IL-2 receptor or its p55 subunit alone. To assess the usefulness of anti-Tac(Fv)-PE40 in treatment of IL-2 receptor-positive leukemia, we tested peripheral blood mononuclear cells from six patients with adult T-cell leukemia. In each of the six patients, anti-Tac(Fv)-PE40 was extremely cytotoxic to the malignant cells. Metabolic activity and sensitivity of the fresh cells improved when a small amount of IL-2 (10 units per ml) was present during incubation. The toxin concentration necessary to inhibit protein synthesis by 50% after 16-hr incubation of cells with immunotoxin varied from 1.6 to 16 ng/ml (2.5-25 x 10(-11) M). In every case, binding was by means of the Tac antigen because anti-Tac(Fv)-PE40 cytotoxicity was prevented by adding excess anti-Tac antibody. Moreover, anti-Tac alone or an inactive mutant of anti-Tac(Fv)-PE40 without ADP-ribosylation activity had very little cytotoxic activity. Peripheral blood mononuclear cells from normal controls, from a patient with Tac-negative leukemia, and from adult T-cell leukemia patients without significant peripheral blood involvement were not sensitive to anti-Tac(Fv)-PE40. These results indicate that anti-Tac(Fv)-PE40 is a potent cytotoxin against adult T-cell leukemia cells in vitro and warrants clinical testing.

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IM

MEDLINE

0027-8424

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8291-5

pubmed-meshheading:2236041-ADP Ribose Transferases, pubmed-meshheading:2236041-Antibodies, Monoclonal, pubmed-meshheading:2236041-Antigens, CD, pubmed-meshheading:2236041-Bacterial Toxins, pubmed-meshheading:2236041-Cell Line, pubmed-meshheading:2236041-Cell Survival, pubmed-meshheading:2236041-Exotoxins, pubmed-meshheading:2236041-Female, pubmed-meshheading:2236041-Humans, pubmed-meshheading:2236041-Immunoglobulin Variable Region, pubmed-meshheading:2236041-Immunotoxins, pubmed-meshheading:2236041-Leukemia, T-Cell, pubmed-meshheading:2236041-Leukemia-Lymphoma, Adult T-Cell, pubmed-meshheading:2236041-Leukocytes, Mononuclear, pubmed-meshheading:2236041-Male, pubmed-meshheading:2236041-Pseudomonas, pubmed-meshheading:2236041-Tumor Cells, Cultured, pubmed-meshheading:2236041-Virulence Factors

The recombinant immunotoxin anti-Tac(Fv)-Pseudomonas exotoxin 40 is cytotoxic toward peripheral blood malignant cells from patients with adult T-cell leukemia.

Journal Article