A recombinant CD7-specific single-chain immunotoxin is a potent inducer of apoptosis in acute leukemic T cells.
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.
Peipp
Matthias
M
Chair of Genetics, University of Erlangen-Nuremberg, Staudtstrasse 5, D-91058 Erlangen, Germany.
Küpers
Heide
H
Saul
Domenica
D
Schlierf
Beate
B
Greil
Johann
J
Zunino
Susan J
SJ
Gramatzki
Martin
M
Fey
Georg H
GH
D036002:ADP Ribose Transferases / Q000494:pharmacology*; D000818:Animals; D000918:Antibody Specificity; D019011:Antigens, CD7 / Q000276:immunology*; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D001427:Bacterial Toxins; D019556:COS Cells; D002648:Child; D000939:Epitopes / Q000276:immunology; D005098:Exotoxins / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D000922:Immunotoxins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology*; D007223:Infant; D019169:Jurkat Cells / Q000166:cytology / Q000187:drug effects; D015458:Leukemia, T-Cell / Q000188:drug therapy* / Q000276:immunology / Q000473:pathology; D011065:Poly(ADP-ribose) Polymerases; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D019011:Antigens, CD7; D001427:Bacterial Toxins; D000939:Epitopes; D005098:Exotoxins; D007128:Immunoglobulin Fragments; D000922:Immunotoxins; D011065:Poly(ADP-ribose) Polymerases; D011994:Recombinant Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A