Transplantation-related mortality (TRM) is high after HLA-mismatched umbilical cord blood (UCB) transplantation (UCBT). In utero, exposure to noninherited maternal antigen (NIMA) is recognized by the fetus, which induces Tregulator cells to that haplotype. It is plausible that UCBTs in which recipients are matched to donor NIMAs may alleviate some of the excess mortality associated with this treatment. To explore this concept, we used marginal matched-pair Cox regression analysis to compare outcomes in 48 NIMA-matched UCBTs (ie, the NIMA of the donor UCB unit matched to the patient) and in 116 non–NIMA-matched UCBTs. All patients had a hematologic malignancy and received a single UCB unit. Cases and controls were matched on age, disease, disease status, transplantation-conditioning regimen, HLA match, and infused cell dose. TRM was lower after NIMA-matched UCBTs compared with NIMA-mismatched UCBTs (relative risk, 0.48; P=.05; 18% versus 32% at 5 years posttransplantation). Consequently, overall survival was higher after NIMA-matched UCBT. The 5-year probability of overall survival was 55% after NIMA-matched UCBTs versus 38% after NIMA-mismatched UCBTs (P=.04). When faced with the choice of multiple HLA-mismatched UCB units containing adequate cell doses, selecting an NIMA-matched UCB unit may improve survival after mismatched UCBT.

Limited cell dose hampers wider use of cord blood transplantation (CBT). By depleting plasma but not RBC during processing, nucleated cell (NC) loss is reduced to <0.1% which increases significantly the proportion of high cell dose products-3-fold for products with NC >or=200 x 10(7). Clinical outcome for plasma depleted (PD) CBT was previously unavailable. A retrospective audited analysis was performed on 118 PD CBT, with mean and median NC doses of 7.6 x 10(7)/kg and 5.6 x 10(7)/kg, respectively, for this mostly pediatric population. The median times to engraftment and engraftment rates for ANC 500 and platelet 20K were 22 and 50 days, respectively, and 90% +/- 3% and 77% +/- 5%, respectively. The incidences of grade III-IV acute graft-versus-host disease (aGVHD) and extensive chronic GVHD (cGVHD) were 13% +/- 4% and 17% +/- 6%, respectively. Relapse rate for malignancies was 25% +/- 6% and 100-day treatment-related mortality (TRM) was 16% +/- 3%. With a median follow-up of 557 days, the 1-year overall survival and relapse-free survival are 65% +/- 5% and 51% +/- 6%, respectively. These results demonstrate that PD CBT is safe and effective, and that eliminating RBC reduction or depletion improves cell recovery during CB processing, resulting in a larger proportion of the inventory with high NC number.

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Hematopoietic cell transplantation (HCT) using CCR5-Δ32/Δ32 stem cells from an adult donor has resulted in the only known cure of HIV infection. However, it is not feasible to repeat this procedure except rarely because of the low incidence of the CCR5-delta 32 allele, the availability of only a small number of potential donors for most patients and the need for a very close HLA match between donor and recipient. In contrast, cord blood (CB) transplants require significantly less stringent HLA matching. Therefore, our hypothesis is that cure of HIV infections by HCT can be accomplished much more readily using umbilical cord blood stem cells obtained from a modestly sized inventory of cryopreserved CCR5-Δ32/Δ32 CB units. To test this hypothesis we have developed a screening program for cord blood units and are developing an inventory of CCR5-Δ32/Δ32 cryopreserved units available for HCT. 300 such units are projected to provide for Caucasian pediatric patients a 73.6% probability of finding an adequately HLA matched unit with a cell dose of ≥ 2.5 x 107TNC/kg and a 27.9% probability for Caucasian adults. With a cell dose of ≥ 1 x 107TNC/kg the corresponding projected probabilities are 85.6% and 82.1%. The projected probabilities are lower for ethnic minorities. Impetus for using CB HCT was provided by a transplant of an adult with acute myelogenous leukemia who was not HIV infected. The HCT was performed with a CCR5-Δ32/Δ32 CB unit, and post-transplant in vitro studies indicated that the patient’s peripheral blood mononuclear cells (PBMCs) were resistant to HIV infection.

To augment graft cell dose, we evaluated the safety of the combined transplantation of two partially HLA-matched umbilical cord blood (UCB) units. Five patients with transfusion-dependent thalassemia, median age 11.1 years (range 10-13.1), received 2 UCB units after myeloablative conditioning. Cord blood units were a 4/6-HLA-match or better with the recipient, and contained a minimum combined pre-freeze CD34 cell dose of 3.0 Â 10 5 /kg. All patients engrafted at a median of 15 days (range 12-19). Four patients with durable trilineage engraftment showed acute grade I-III GVHD; none developed extensive chronic GVHD until the date of last contact. The median times to red blood cell transfusion independence and platelet engraftment were 32 and 49 days after transplant, respectively. With a median follow-up of 18.5 months (range 11-32), four patients transplanted with UCB from two different partially HLA-matched donors were transfusion-independent. Therefore, transfusion of two partially HLA-matched UCB units is safe, and may overcome the cell-dose barrier that limits the use of UCB in longterm recipients of multiple transfusions for thalassemia.