Immunotoxins Containing Recombinant Anti-CTLA-4 Single-Chain Fragment Variable Antibodies and Saporin: In Vitro Results and In Vivo Effects in an Acute Rejection Model

• Published in: The Journal of immunology (1950) 2001-10, Vol.167 (8), p.4222-4229
• Main Authors: Tazzari, Pier-Luigi, Polito, Letizia, Bolognesi, Andrea, Pistillo, Maria-Pia, Capanni, Paolo, Palmisano, Giulio Lelio, Lemoli, Roberto M, Curti, Antonio, Biancone, Luigi, Camussi, Giovanni, Conte, Roberto, Ferrara, Giovanni B, Stirpe, Fiorenzo
• Format: Article
• Language: English
• Subjects: Abatacept; Animals; Antigens, CD; Antigens, Differentiation - immunology; CTLA-4 Antigen; CTLA-4 protein; Dimerization; Dose-Response Relationship, Drug; Graft Rejection - drug therapy; Hematopoietic Stem Cells - drug effects; Humans; Immunoconjugates; Immunoglobulin Variable Region - therapeutic use; Immunotoxins - therapeutic use; Mice; Mice, Inbred DBA; N-Glycosyl Hydrolases - therapeutic use; Neoplasm Transplantation - immunology; Plant Proteins - therapeutic use; Ribosome Inactivating Proteins, Type 1; Ribosome Inactivating Proteins, Type 2; saporin; Saporins; T-Lymphocytes - drug effects
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.167.8.4222

Immunotoxins containing recombinant human-derived single-chain fragment variable (scFv) reagents (83 and 40) against CTLA-4 (CD152) linked to saporin, a ribosome-inactivating protein, were prepared and tested on CD3/CD28-activated T lymphocytes, MLRs, CTLA-4-positive cell lines, and hemopoietic precursors. Immunotoxins induced apoptosis in activated T lymphocytes and were able to specifically inhibit MLR between T lymphocytes and dendritic cells. The 83-saporin immunotoxin also inhibited the T cell activation in an MLR between T lymphocytes and an EBV-positive lymphoblastoid B cell line. Toxicity tests on hemopoietic precursors showed little or no effects in inhibiting colonies' growth. As the 83 scFv Ab was reactive also with activated mouse T lymphocytes, 83-saporin was tested in a model of tumor rejection consisting of C57BL/6 mice bearing a murine H.end endothelioma cell line, derived from DBA/2 mice. The lymphoid infiltration due to the presence of the tumor was reduced to a high extent, demonstrating that the immunotoxin was actually available and active in vivo. Thus, taking the results altogether, this study might represent a new breakthrough for immunotherapy, showing the possibility of targeting CTLA-4 to kill activated T cells, using conjugates containing scFv Abs and type 1 ribosome-inactivating protein.