Background
Allogeneic hematopoietic cell transplantation is a potentially curative treatment for hematologic malignancies and nonmalignant disorders. Rapid immune reconstitution (IR) following transplantation has been associated with improved clinical outcomes and lower infection rates. Omidubicel, an advanced cell therapy, is manufactured from an HLA-matched single umbilical cord blood (UCB) unit and was recently approved by the FDA. Omidubicel consists of nicotinamide-expanded CD133+cells (cultured fraction (CF)) and a CD133-negative flow-through (non-cultured fraction (NF)). Faster hematopoietic recovery, reduced rates of infection, and shorter hospitalizations were demonstrated for transplantation with omidubicel compared to standard UCB.1 Further, recently published results demonstrate prompt multilineage IR, including T cell, natural killer (NK), and B cell populations. Robust and early reconstitution of lymphocyte subsets correlated with CD34+ cell dose.2 This study evaluated the myeloid and lymphoid cellular content of omidubicel and potential effect on lymphoid IR.
Methods
Immunophenotyping as conducted using three broad panels examining T, NK, NK-T, B, hematopoietic stem cells, progenitor, and mature myeloid cell population composition. 36 samples from 12 replicated experiments were collected and cryopreserved from the starting UCB and from omidubicel CF and NF. FCS-Expresstm (Denovo Software) FlowSOM and tSNE pipelines were used for data analysis using advanced mass-cytometry analysis.
Results
More than 600 different cell populations were defined and subsequently combined into ~100 consensus clusters. Compared to the UCB starting material, omidubicel manufacturing significantly altered cellular composition. After manufacturing, the CF was almost exclusively comprised of myeloid subpopulations, with significant increases for both total nucleated cells (1.2–1.6-fold) and myeloid lineage enrichment (2.2–3.6-fold). UCB and NF cellular composition were found to be similar in relative composition, with the NF containing 50–70% fewer total cells. High resolution analysis of the CF revealed significant enrichment (25–62-fold increase) of myeloid subpopulations expressing dendritic cell markers (CD11c+/1a+/1c+/HLA-DRhigh). The absence of mature and early lymphoid progenitor cells in the CF and the reduction of those cellular subsets in the NF suggests that post-transplantation IR of lymphoid lineages may be related to the myeloid cell enrichment in the CF. Increased dendritic cell level could indicate possible activation of lymphoid cells in general and T cells in particular.
Conclusions
Omidubicel manufacturing significantly enriches myeloid and dendritic cellular content and provides a possible mechanism for the rapid proliferation of lymphoid populations during the early post-transplant period. Altered omidubicel cell composition associates with shorter lymphopenia period and improved clinical outcomes.
Acknowledgements
Special thanks to Ronit Amiel Tokarsky (Almog Diagnostic & Medical equipment Ltd.), Aviva Blechman Peretz (Almog Diagnostic & Medical equipment Ltd.) for an excellent handling of the flow cytometry raw data acquisition and thorough quality control, and to Andrea Valle (De Novo Software, Dotmatics) for exceptional FCS-express software guidance and outstanding patience.
References
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