CD45RA Depleted T-cell Infusion for Prevention of Infections After TCRab/CD19-depleted Allo-HSCT

Overview

The purpose of this prospective randomized study is to determine whether infusions of T-memory cells prevent infections in children with leukemia after allogeneic alpha, beta T-cell receptor (TcRab)/CD19-depleted hematopoietic stem cell transplantation (HSCT).

Graft-versus-host disease (GVHD) remains the most important direct complication of hematopoietic stem cell transplantation. Methods used to prevent GVHD include diverse pharmacologic interventions and ex vivo methods of T-cell depletion, the latter being the most effective ones. Historically depletion of T-cells from the graft is associated with increased rate of graft failure, relapse of malignant disease and prolonged immune deficiency. Selective depletion of TCR-alpha/beta T-lymphocytes is a new method of hematopoietic stem cell graft manipulation, which is thought to conserve important cell populations, e.g. NK cells and gamma/delta T cells within the graft. Preliminary results suggest that TCR alpha/beta depletion ensures high engraftment rate, low early mortality and good control of GVHD. The problem of delayed immune reconstitution and life-threatening viral infections remains incompletely resolved. Depletion of naive (CD45RA-positive) T-cells was developed as a new method of graft manipulation to prevent GVHD. Research data indicate that alloreactivity is associated mainly with naive T-cell fraction. In vitro depletion of CD45RA lowers significantly the alloreactive response while retaining reactivity to pathogens. In previous pilot protocol the investigators confirmed that infusion after TCR-alpha/beta depleted transplantation of low doses of CD45RA-depleted mononuclear cells are safe and potentially protective against viral infections. The biologic readout for the protocol was a quantitative assessment of T-cell reactivity to common pathogens after infusion and owing to the trial results expansion of CMV-specific CD8 T-cells was discovered in most of the patients. In current randomized protocol the investigators are posing a question if donor lymphocytes infusion (DLI) of low doses of CD45RA-depleted mononuclear cells are effective in viral prophylaxis after TCR-alpha/beta depleted transplantation.