Depletion of Alloreactive T-Cells by Anti-CD137-Saporin Immunotoxin

Abstract

Depletion of alloreactive T-lymphocytes from allogeneic bone marrow transplants may prevent graft-versus-host disease (GVHD) without impairing donor cell engraftment, immunity, and the graft-versus-leukemia (GVL) effect. Alloreactive T-cells may be identified by their expression, upon activation, of CD137, a costimulatory receptor and putative surrogate marker for antigen-specific effector T-cells. In this context, we tested the use of anti-CD137-saporin immunotoxin to selectively deplete mouse and human alloreactive T-cells. Anti-CD137 antibodies were internalized by cells within 4 h of binding to the cell surface CD137, and anti-CD137-saporin immunotoxin effectively killed polyclonally activated T-cells or antigen-stimulated T-cells. Transfer of donor T-cells after allodepletion with anti-CD137-saporin immunotoxin failed to induce any evident expression of GVHD; however, a significant GVL effect was observed. Targeting of CD137 with an immunotoxin was also effective in killing polyclonally activated or alloreactive human T-cells. Our results indicate that anti-CD137-saporin immunotoxin may be used to deplete alloreactive T-cells prior to bone marrow transplantation and thereby prevent GVHD and the relapse of leukemia.

Plant Ribosome-Inactivating Proteins: Progesses, Challenges and Biotechnological Applications (and a Few Digressions)

“…Instead of anti-cancer treatment, RIPs have been also used to eliminate the cholinergic inputs to hippocampus [ 187 ], monocyte-derived inflammatory dendritic cells [ 188 ], and alloreactive CD4 + and CD8 + T-cells through CD137-mediated internalization [ 189 ]. The cholinergic projections to ventral subiculum were selectively eliminated using 192 IgG-saporin conjugates, and this model is useful for investigation of the cholinergic modulation of subicular theta-gamma activity on spatial learning and memory functions in rats.…”

“…CD137 signaling is considered to be involved in multiple stages of GVHD development. Lee et al developed a method to selectively eliminate alloreactive CD4 + and CD8 + T-cells through CD137-mediated internalization of anti-CD137 mAbs conjugated with saporin [ 189 ]. CD137-expressing cells were killed by the treatment with the conjugate, and transfer of donor T-cells after allodepletion showed no evident GVHD [ 189 ].…”

Integration of the Innate and Adaptive Immunity by CD137-CD137L Bidirectional Signals: Implications in Allograft Rejection

“…However, blockade of CD137 in conditioned recipients reduces either CD8 + T cell-mediated or CD4 + T cell-mediated GVHD lethality (21). Consistently, in a MHC-disparity acute GVHD model, depletion of alloreactive donor CD137 + T cells does not induce the development of GVHD (22). It also has been shown that cardiac allograft rejection is inhibited by anti-CD137L monoclonal antibody in T-cell-replete mice (23).…”

Sequential Prodrug Strategy To Target and Eliminate ACPA-Selective Autoreactive B Cells

“…To demonstrate that restored antigen-recognition by B cells, could also result in selective killing of ACPA-expressing B cells, we conjugated the biotinylated antigen variants to a streptavidin-saporin conjugate (SA-ZAP, Figure A and B). , Saporin is a cytotoxic ribosome inhibitor that induces cell death by apoptosis, which has been used in many in vivo studies as antibody-drug conjugate. − Equal numbers (1 × 10 4 ) of ACPA-expressing and TT-specific immortalized B cells were cultured with 0, 0.1, 1, 10, and 100 nM antigen-SA-ZAP conjugates. After 4 days of incubation, a XTT cell viability assay was performed to assess the amount of remaining viable cells.…”