A recombinant CD7-specific single-chain immunotoxin is a potent inducer of apoptosis in acute leukemic T cells

Matthias Peipp, Heide Küpers, Domenica Saul, Beate Schlierf, Johann Greil, Susan J. Zunino, Martin Gramatzki, Georg H. Fey

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64 Scopus citations


A recombinant immunotoxin was constructed from the hybridoma antibody TH-69 directed against human CD7, a surface antigen of leukemic T cells. The antibody was subcloned as a single chain Fv (scFv) fragment and genetically linked to a truncated Pseudomonas exotoxin A fragment containing the catalytic domains II and III but lacking the receptor binding domain I. Domain I was replaced by the scFv, thus conferring restricted specificity for CD7.positive cells. The bacterially expressed and purified toxin retained binding specificity for CD7-positive cells. It promoted apoptosis in two CD7-positive cell lines derived from T-lineage acute lymphoblastic leukemias, CEM and Jurkat, but not in the CD7-negative B-lymphoid lines REH, Nalm-6, and SEM. Maximum killing in excess of 95% was reached after 96 h in CEM and Jurkat cells with a single dose of 100 ng/ml. Cells treated with a similarly constructed scFv-exotoxin A immunotoxin against melanoma-associated chondroitin sulfate proteoglycan, an antigen absent from leukemic T cells, remained unaffected. Lysis of target cells occurred via apoptosis as evidenced by staining with Annexin V and specific cleavage of poly(ADP-ribose) polymerase. Approximately 20% of leukemic cells from a patient with CD7-positive acute T-cell leukemia kept in long-term primary culture for 30 cell generations were killed within 96 h after treatment with the toxin. These findings justify further evaluation of the agent in view of potential therapeutic applications.

Original languageEnglish (US)
Pages (from-to)2848-2855
Number of pages8
JournalCancer Research
Issue number10
StatePublished - May 15 2002
Externally publishedYes

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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