ABSTRACT
Pre-clinical studies of allogeneic stem cell transplantation suggest that depletion of naive T cells from donor lymphocytes will reduce the risk of GvHD but preserve immunity to infectious pathogens. In this study, we have established a clinical-grade protocol under good manufacturing practice conditions for purging CD62L(+) naive T cells from steady-state leukapheresis products using the CliniMACS system. The efficacy of immunomagnetic CD62L depletion was assessed by analysis of cell composition and functional immune responses. A median 2.9 log CD62L depletion was achieved with no evidence of CD62L shedding during the procedure and a mean T-cell yield of 47%. CD62L(-) cells comprised an equal mix of CD4(+) and CD8(+) T cells, with elimination of B cells but maintenance of regulatory T cells and natural killer cell populations. CD62L-depleted T cells were predominantly CD45RA(-) and CD45RA(+) effector memory (>90%) and contained the bulk of pentamer-staining antivirus-specific T cells. Functional assessment of CD62L(-) cells revealed the maintenance of antiviral T-cell reactivity and a reduction in the alloreactive immune response compared with unmanipulated cells. Clinical-grade depletion of naive T cells using immunomagnetic CD62L beads from steady-state leukapheresis products is highly efficient and generates cells suitable for adoptive transfer in the context of clinical trials.