Accelerated immune recovery following LLME treated donor lymphocyte infusion

Delayed immune reconstitution is a major cause of morbidity and mortality after T cell depleted allogeneic progenitor cell transplant (PCT). To accelerate immune reconstitution without GVHD, we have administered escalating doses of L-leucyl-L-leucine methyl ester (LLME) treated lymphocytes (DLI) to 18 patients post CD34+ cell-enriched PCT in an ongoing phase I trial. LLME’s cellular toxicity occurs after polymerization by dipeptidyl peptidase, leading to selective depletion of cells with cytotoxic effector granules containing perforin. Products treated with LLME demonstrated a median depletion of 94.9% CD56+ cells, 75.8 % CD8+ cells, but only 37.2% CD4+ cells. Patients initially received 10e4 (haploidentical (HAPLO)), 10e5 (HLA identical unrelated (URD)), or 10e6 (HLA identical sibling (SIB)) CD3+ cells/kg in cohorts of 3, and were eligible for additional infusions at a one log higher dose after 28 days if there was no evidence of GVHD or the CD4 count was less than the target of 100 cells/ml. The initial dose was escalated by one log in subsequent cohorts if no complications were observed in the previous cohort. Nine patients received grafts from SIBs (4 at 10e6, 5 at 10e7), six from URDs (3 at10e5, 3 at 10e6), and three from HAPLOs (3 at 10e4). All patients had pre-DLI CD4 counts of <5.0 cells/ml, and received 1 to 3 infusions post PCT. Since ATG was used during PCT cytoablation, the first DLI infusions were administered after ATG levels were <2 mcg/ml. After DLI #1, 6/8 evaluable matched SIB recipients and 2/6 evaluable URD recipients demonstrated early recovery of donor derived CD4+ cells prior to day 35 s/p DLI, with a median CD4 count of 139 cells/ul (range 57–471). Ten of these achieved a CD4+ count above 100 after 1–3 total infusions. In contrast, none of the haploidentical recipients (receiving the smallest doses) had an increase in CD4+ counts. Five patients developed GVHD (Grade I–II (n =4), Grade III (n = 1 following 4×10e7 LLME DLI). In recovering patients, spectratype analysis of CD4+ cells comparing DLI before LLME treatment with lymphocytes recovered from the patients post DLI demonstrated that 94% of the resolvable Vb families were equally complex. Perforin positive cells, as well as adenovirus (n = 2), EBV (n = 1) and CMV (n = 2) specific lymphocytes, also recovered post-PCT in these patients. These preliminary results suggest that LLME treated DLI can accelerate CD4+ reconstitution without causing severe GVHD.