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Construction and characterization of human CD7-specific single-chain Fv immunotoxins
M E Pauza1, S O Doumbia, C A Pennell
1Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis 55455, USA.
Abstract:
To develop novel therapeutic agents for treatment of human T cell malignancies, we constructed two single-chain Fv (sFv) immunotoxins specific for the T cell-associated Ag CD7. The sFv fragments were derived from the murine hybridomas 3A1e and 3A1f and were expressed as soluble proteins in Escherichia coli. Surface plasmon resonance analyses demonstrated that the purified 3A1e and 3A1f sFv fragments specifically bound CD7 with high affinity, 8.1 and 1.8 nM, respectively. The difference in affinity is chiefly due to a slower dissociation rate for the 3A1f sFv fragment. Despite this difference, both monovalent sFv fragments were comparably internalized by CD7+ human T leukemic cells within 30 min. These data support findings of previous studies suggesting that CD7 internalization does not require cross-linking. The sFv immunotoxins were assembled by linking ricin toxin A chain to the C termini of the sFv fragments via disulfide bonds. Both sFv immunotoxins were comparably potent in their ability to inhibit protein synthesis in vitro in CD7+ Jurkat cells (50% inhibiting concentration = 15 pM). Further preclinical studies on the use of the 3A1e and 3A1f sFv immunotoxins to treat human T cell diseases therefore appear warranted.
Insights
Researchers developed novel single-chain variable fragment (sFv) immunotoxins targeting CD7 for T cell malignancies. These agents showed potent protein synthesis inhibition in vitro, warranting further preclinical studies for treating T cell diseases.
Area of Science:
- Immunology
- Oncology
- Biotechnology
Background:
- Human T cell malignancies represent a significant therapeutic challenge.
- Targeting cell-specific antigens is a promising strategy for developing novel cancer therapies.
Purpose of the Study:
- To construct and characterize novel single-chain variable fragment (sFv) immunotoxins targeting the T cell-associated antigen CD7.
- To evaluate the efficacy of these immunotoxins in inhibiting protein synthesis in CD7-expressing T leukemic cells.
Main Methods:
- Single-chain Fv fragments were derived from murine hybridomas (3A1e and 3A1f) and expressed in E. coli.
- Surface plasmon resonance was used to assess binding affinity to CD7.
- Immunotoxins were assembled by linking ricin toxin A chain to sFv fragments.
- In vitro protein synthesis inhibition assays were performed using CD7+ Jurkat cells.
Main Results:
- Both 3A1e and 3A1f sFv fragments demonstrated specific binding to CD7 with high affinity (8.1 nM and 1.8 nM, respectively).
- Monovalent sFv fragments were rapidly internalized by CD7+ T leukemic cells, independent of cross-linking.
- Both sFv immunotoxins exhibited comparable and potent inhibition of protein synthesis in vitro (IC50 = 15 pM).
Conclusions:
- The developed sFv immunotoxins targeting CD7 are potent therapeutic candidates for human T cell malignancies.
- The rapid internalization of CD7 by these immunotoxins supports their potential clinical utility.
- Further preclinical investigation of these immunotoxins for treating T cell diseases is warranted.