Transfusion of CD45RA-depleted Donor Lymphocytes to Improve Regeneration of Antimicrobial Immunity After TCR-alpha/Beta Depleted Hematopoietic Stem Cell Transplantation

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 the current protocol we plan to test whether relatively low doses of CD45RA-depleted mononuclear cells can be safely infused after TCR-alpha/beta depleted transplantation. The biologic readout for the protocol will be quantitative assessment of T-cell reactivity to common pathogens after infusion.