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.
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.
Tazzari
P L
PL
Service of Transfusion Medicine, S. Orsola-Malpighi Hospital, Bologna, Italy.
Polito
L
L
Bolognesi
A
A
Pistillo
M P
MP
Capanni
P
P
Palmisano
G L
GL
Lemoli
R M
RM
Curti
A
A
Biancone
L
L
Camussi
G
G
Conte
R
R
Ferrara
G B
GB
Stirpe
F
F
D000069594:Abatacept; D000818:Animals; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000276:immunology*; D060908:CTLA-4 Antigen; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D006084:Graft Rejection / Q000188:drug therapy*; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D006801:Humans; D018796:Immunoconjugates; D007135:Immunoglobulin Variable Region / Q000627:therapeutic use*; D000922:Immunotoxins / Q000627:therapeutic use*; D051379:Mice; D008811:Mice, Inbred DBA; D009699:N-Glycosyl Hydrolases / Q000627:therapeutic use; D009368:Neoplasm Transplantation / Q000276:immunology; D010940:Plant Proteins / Q000627:therapeutic use*; D054789:Ribosome Inactivating Proteins, Type 1; D054790:Ribosome Inactivating Proteins, Type 2; D000076985:Saporins; D013601:T-Lymphocytes / Q000187:drug effects
D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; C556707:Ctla4 protein, mouse; D018796:Immunoconjugates; D007135:Immunoglobulin Variable Region; D000922:Immunotoxins; D010940:Plant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; D054790:Ribosome Inactivating Proteins, Type 2; D000069594:Abatacept; D009699:N-Glycosyl Hydrolases; D000076985:Saporins