Purpose: Haploidentical hematopoietic stem cell transplantation (haplo-SCT) provides an option for cancer patients lacking a compatible donor. However, the delayed immune reconstitution increases incidence of opportunistic infections and disease relapse. We conducted a phase I-II prospective trial to evaluate the effect of escalating doses of CD8-depleted (Miltenyi Device) donor lymphocyte infusions (DLIs) following RIC haplo-SCT. Here, we present the data on the immune reconstitution.

Patients and Methods: Twenty-eight patients (pts) with advanced lymphoproliferative diseases (n=24) or acute myeloid leukaemia (n=4) were enrolled in this study. Fifteen (54%) of 28 pts had refractory disease. All pts received a thiotepa-fludarabine based RIC regimen, with an ex vivo and in vivo T-cell depletion performed by CD34+ cell selection and alemtuzumab infusion. Fifty-four CD8-depleted DLIs were administered to 23 pts [dose level 1 (n=4): 1×104/kg on days + 45, +75, +105; dose level 2 (n=11): 5×104/kg on days + 45, +75, +105; dose level 3 (n=8): 1×104/kg on day+ 45, 5x104/kg on days +75 and +105].

Results: At a median follow-up of 29 months, 12 pts are alive (n=3 Hodgkin Lymphoma, n=6 Non-Hodgkin Lymphoma, n=1 Multiple Myeloma, n=2 Acute Myeloid Leukemia) and 16 died from any cause [n=6 for non-relapse mortality (NRM), n=10 for disease progression] with a 2-year estimates of overall survival of 39%. The 2-year cumulative incidence of NRM and relapse were 26% and 51%, respectively. Six pts (26%) developed grade II-IV acute graft-versus-host disease (GVHD) (dose level 1: no GVHD; dose level 2: 5 cases; dose level 3: 1 case). Following CD8-depleted DLIs, the major findings were:(i) a significant expansion of memory CD4+ cells and CD19+ cells (median value 107/μL and 135/μL, respectively) at 120 days after haplo-SCT; (ii) de-novo T-cell responses to cytomegalovirus (CMV) peptides performed by activation-induced CD137 expression: the median frequency of CMV-specific CD8+/CD137+ and CD4+/CD137+ cells were 2% and 0.4% at 200 days after haplo-SCT, respectively, as evaluated in a subset of pts at risk for CMV reactivation (R CMVpos/D CMVpos/neg); this frequency was associated to a clearance of CMV antigen; (iii) recovery of thymopoiesis: 10 of 20 (50%) pts showed measurable TREC at 1 year after haplo-SCT; (iv) the increase of CD19+ cells was associated to reconstitution of B lymphocyte repertoire as analysed by Immunoglobulin heavy chain (IgH) CDR3 spectratyping: median number peaks in normal donors and pts, at day 360 after haplo-SCT, were 17 (range, 14–21) versus 12 (range, 7–14), respectively.

Conclusions: Our study showed that CD8-depleted DLIs are a feasible procedure with low acute GVHD when using dose level 3. Long-term disease remissions can be observed in advanced lymphoid malignancies. Escalated doses of CD8-depleted DLIs exert complex effects on immune reconstitution: (i) provide help to expansion of CD8 T-cell clones, as suggested by the occurrence of the anti-CMV reactivity; (ii) support B-cell recovery, as demonstrated by a partial recovery of CDR3 polyclonality.

Disclosures: No relevant conflicts of interest to declare.

Author notes

Corresponding author