H e m a t o lo g y E d u c a t io n - European Hematology Association

16 th Congress of the European Hematology Association
intensity conditioning regimen was employed in 28
adult patients with advanced hematological malignancies
who were transplanted with haploidentical CD34+
positively selected stem cells. 25 Engraftment was
achieved in 78% of the patients, and the toxicity was
mostly infections. The co-transplantation of ex vivoexpanded
donor-derived mesenchymal stem cells
together with CD34+ positively selected stem cells
accelerated lymphocyte recovery and reduced the risk
of graft failure in pediatric patients. 26
Transplantation of negatively T-cell depleted stem cells
Depletion of CD3+/CD19+ lymphocytes
While initial attempts to deplete T-cells from BM
resulted only in 1–1.5 log reduction of T-cells, semiautomated
devices for the concomitant depletion of Tand
B-lymphocytes to prevent GVHD and post-transplant
EBV-associated lymphoproliferative disease,
respectively, allow the effective depletion of CD3+
and CD19+ lymphocytes (CD3/19 depletion) from
mobilized peripheral stem cell grafts. 27 The T-cell
depletion with this method (3.5–4 log) is less than
compared with the CD34+ positive selection method
(4.5–5 log). In contrast to the CD34+ positive selection
method, large numbers of NK-cells, monocytes, dendritic
cells, and other myeloid cells are retained in the
graft. In the first clinical study, 20 children with hematological
malignancies were transplanted with CD3depleted
PBSC following a TBI-based myeloablative
preparative regimen. 28 Of 19 evaluable patients, all
engrafted. Six patients (30%) died from TRM and 4
patients (20%) from disease recurrence. Ten patients
(50%) are alive and well. A subsequent pediatric study
was performed in 25 patients with advanced refractory
hematological malignancies (n=9) or patients with
relapse after a previous standard myeloablative transplantation
(n=16). 29 Since these patients were considered
to be at high risk of TRM with a myeloablative
preparative regimen, a less intensive non TBI-based
conditioning regimen consisting of fludarabine (200
mg/m²), thiotepa (10 mg/kg), melphalan (120 mg/m²),
and the anti-CD3 antibody OKT-3 was employed.
Two of three patients who did not engraft were rescued
by another transplant from their original donor,
and one patient had early disease progression without
donor engraftment. The cumulative incidences of
grade II-IV and grade III-IV GVHD were 44% and 8%,
respectively. The cumulative incidence of chronic
GVHD was 28%. Thirteen patients died of disease
recurrence and four from TRM. No lethal viral infections
were seen. Eight patients remain alive with a performance
score greater than or equal to 90%.
In a comparative analysis of the immune reconstitution
in these two cohorts of patients, a much faster
recovery of thymopoiesis, as determined by the rapid
increase of T-cell receptor excision circles (TREC), and a
rapid return of the T-cell receptor repertoire were seen
in the patients who received a non TBI-based less intensive
preparative regimen compared with the patients
who received myeloablative TBI. 30
Additional studies were initiated in pediatric and
adult patients using the less intensive non TBI-based
preparative regimen, consisting of fludarabine (160
mg/m²), thiotepa (10 mg/kg), melphalan (140 mg/m²),
and OKT-3. 31 In a study of 38 pediatric patients, primary
engraftment was seen in 83%. The major cause of graft
failure was rejection. However, after reconditioning and
a second transplant with CD3/19 depleted PBSC from
the other haploidentical parental donor, 32 engraftment
was finally obtained in 98% of the patients. Most
importantly, only 1 out of the 38 patients died from
TRM. Acute GVHD grade 0-I, II, and III-IV were seen in
73%, 24%, and 3% of the patients respectively. In a
recent update, Pfeiffer et al. reported an event-free survival
of 51% for children with acute leukemia who
were in morphological remission at time of transplantation.
33 In a study in adult patients, a similar approach
was used with the same preparative regimen. 34 Twentynine
high risk patients were transplanted and 9/29
patients are alive. The TRM in the first 100 days was
20% and 12 patients relapsed. The immune reconstitution
was analyzed in 28 adult patients who received a
haploidentical CD3/19-depleted graft. T-cell reconstitution
was delayed with a median of 70 CD4+ T-cells/µl
on day +100 post-transplant, whereas the NK cell recovery
was fast reaching normal values at day +20. 35
Depletion of TcRab+/CD19+ lymphocytes
Compared with CD34+ positive selection, the number
of graft-contaminating T-cells is approximately 10fold
higher in CD3/19-depleted grafts, requiring shortterm
post-transplant immunosuppression with
mycophenolate mofetil (MMF). 36 A more effective
approach for the negative depletion of T-cells is the
recently described negative depletion of T-cell receptor
(TcR) ab+ T-lymphocytes from mobilized peripheral
stem cell grafts. 37 With this method, a T-cell reduction of
4.5–5 log can be achieved, which is comparable with
CD34+ positive selection. This approach retains NK
cells, monocytes, dendritic cells, and gδ+ T-lymphocytes
in the graft. gδ+ T-lymphocytes are non-alloreactive
lymphocytes with important anti-infectious and antitumor
properties (for review, see 38 ), which might have
an impact on the outcome of haploidentical transplantation.
In this context, it has been reported that gδ+ T-cells
can exert an anti-leukemic effect in partially mismatched
HSCT. 39 In this retrospective analysis, patients
with a high gδ T-cell count post-transplant had a better
5-year survival than those with normal or low counts
(70.8 vs. 19.6%, p=0.0001), while no difference in the
incidence of GVHD was observed. The first clinical
experience in children undergoing haploidentical transplantation
of TcRab/CD19-depleted T-cells are promising
with a rapid donor engraftment, a rapid expansion
of gδ+ T-lymphocytes, and a rapid immune reconstitution
with a median time to reach 100 CD3+ T-cells of 34
days (own unpublished observations).
Transplantation of T-cell replete bone marrow
and/or peripheral stem cells
The use of T-cell replete BM or PBSCs relies either on
the composition of the graft, on intensive pharmacological
prophylaxis for GVHD, or on the in-vivo T-cell
depletion of the donor-derived T-cells after infusion of
the graft using polyclonal antithymocyte globulin (ATG)
or monoclonal antibodies (Alemtuzumab). Huang et al.
combined G-CSF-primed BM and unmanipulated PBSC
| 66 | Hematology Education: the education programme for the annual congress of the European Hematology Association | 2011; 5(1)