SummaryMesenchymal stem cells (MSC) are being used increasingly in clinical trials for a range of regenerative and inflammatory diseases. Bone marrow is the traditional source but is relatively inaccessible in large volume. MSC have now been derived from tissues other than bone marrow including placenta and adipose tissue. We have used placenta obtained after delivery as a source of MSC and have been unable to detect any marked differences from marrow-derived MSC in terms of cell surface phenotype, chemokine receptor display, mesodermal differentiation capacity or immunosuppressive ability. This report described our manufacturing process for isolating and expanding placenta-derived human MSC and their safe infusion into the first patient in a clinical trial program of human placenta-derived MSC.

Cytomegalovirus reactivation and infection post-allogeneic hematopoietic stem cell transplant continue to cause morbidity and mortality. Current pharmacologic therapies are limited by side effects. Adoptive transfer of ex vivo generated cytomegalovirus-specific T cells has the potential to restore immunity, prevent cytomegalovirus, and circumvent the need for pharmacologic therapies. We have generated donor-derived cytomegalovirus-specific cytotoxic T cells using dendritic cells pulsed with the HLA-A2 restricted nonapeptide NLVPMVATV (NLV) derived from the cytomegalovirus-pp65 protein. These cytotoxic T cells have been given prophylactically to 9 recipients aged 4 to 65 years on or after day 28 post-allogeneic hematopoietic stem cell transplant. Only 2 of 9 recipients received T cell depletion in vivo or in vitro. There were no immediate adverse reactions to the infusions. During 97-798 days of follow-up, 2 recipients developed cytomegalovirus reactivation; neither developed cytomegalovirus disease or required pharmacotherapy. Three recipients developed acute graft versus host disease after infusion. Two recipients died, 1 from thrombotic thrombocytopenia purpura secondary to cyclosporine, 1 from complications of graft versus host disease. A transient increase in numbers of cytomegalovirus-specific T cells demonstrated by NLV-tetramer binding was seen in 6 recipients. Prophylactic adoptive transfer of NLV-specific T cells is safe and may be effective in preventing cytomegalovirus reactivation.

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CD19-specific chimeric antigen receptor (CAR19) T-cells effectively induce remission of B-cell malignancy, but the cost and complexity of production using viral vectors is a factor limiting widespread application. Furthermore, the small cargo capacity of viral vectors may hamper future development of more heavily engineered CAR T-cells. We demonstrated the feasibility of generating CAR19 T-cells from HLA-matched donors of sibling allogeneic hematopoietic stem cell transplant (HSCT) patients via a simple and inexpensive method using the high-capacity piggyBac transposon. A cohort of 10 patients with relapsed or refractory B-cell acute lymphoblastic leukemia or aggressive lymphoma following HSCT were the first human subjects to receive piggyBac-generated CAR19 T-cells. Treatment with intra-patient escalating doses of CAR19 T-cells was effective, with all 9 evaluable patients achieving complete remission. At a median follow-up of 18.0 months, 5 patients remained in complete remission of B-cell malignancy. One patient died of viral sepsis. Four patients developed cytokine release syndrome of maximum grade 2, and no neurotoxicity or new graft-versus-host disease occurred. However, two patients developed malignant CAR19 T-cell tumors, one of whom was successfully treated; one patient died of the secondary tumor. The piggyBac system represents a feasible alternative to viral vectors for the generation of effective CAR19 T-cells, but its oncogenic potential in the context of the described production process will need to be addressed before any further clinical use is possible. This trial was registered at www.anzctr.org.au as ACTRN12617001579381.

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