Ex vivo virotherapy with myxoma virus does not impair hematopoietic stem and progenitor cells.

BACKGROUND: Relapsing disease is a major challenge after hematopoietic cell transplantation for hematological malignancies. Myxoma virus (MYXV) is an oncolytic virus that can target and eliminate contaminating cancer cells from auto-transplant grafts. The aims of this study were to examine the impact of MYXV on normal hematopoietic stem and progenitor cells and define the optimal treatment conditions for ex vivo virotherapy. METHODS: Bone marrow (BM) and mobilized peripheral blood stem cells (mPBSCs) from patients with hematologic malignancies were treated with MYXV at various time, temperature and incubation media conditions. Treated BM cells from healthy normal donors were evaluated using flow cytometry for MYXV infection, long-term culture-initiating cell (LTC-IC) assay and colony-forming cell (CFC) assay. RESULTS: MYXV initiated infection in up to 45% of antigen-presenting monocytes, B cells and natural killer cells; however, these infections were uniformly aborted in >95% of all cells. Fresh graft sources showed higher levels of MYXV infection initiation than cryopreserved specimens, but in all cases less than 10% of CD34(+) cells could be infected after ex vivo MYXV treatment. MYXV did not impair LTC-IC colony numbers compared with mock treatment. CFC colony types and numbers were also not impaired by MYXV treatment. MYXV incubation time, temperature or culture media did not significantly change the percentage of infected cells, LTC-IC colony formation or CFC colony formation. CONCLUSIONS: Human hematopoietic cells are non-permissive for MYXV. Human hematopoietic stem and progenitor cells were not infected and thus unaffected by MYXV ex vivo treatment.

Vitamin D effect on umbilical cord blood characteristics: a comparison between African Americans and Caucasians.

BACKGROUND: Umbilical cord blood (UCB) units collected from African Americans (AAs) have lower total nucleated cell (TNC) and CD34+ cell counts and are more likely to disqualify for banking compared to other ethnic groups. Furthermore, AAs have higher prevalence of 25-hydroxyvitamin D (25(OH)D) deficiency. Given the importance of 25(OH)D in hematopoiesis, we examined the racial differences in UCB unit 25(OH)D content and its correlation with UCB cellular characteristics. STUDY DESIGN AND METHODS: A total of 119 UCB units that did not meet the TNC count banking criteria were analyzed. Fifty-one UCB units were collected from AA mothers and 68 from Caucasian mothers. We analyzed UCB volume, hematocrit (Hct), TNCs, mononuclear cells (MNCs), CD34+ cells, plasma 25(OH)D concentration, and progenitor clonogenic capacity measured by colony-forming cell (CFC) assay. RESULTS: Compared to Caucasians, AAs had significantly lower UCB 25(OH)D levels (p<0.0001), TNCs (p=0.002), MNCs (p=0.026), and CD34+ cells (p=0.026). Severe deficiency (25(OH)D<10 ng/mL) was only detected in AAs. No difference in median CFC count/10,000 MNCs was detected between AAs and Caucasians. Independent of race, a significant association was detected between 25(OH)D level and TNCs (r=0.193 p=0.035) and Hct (r=0.196 p=0.033). CONCLUSION: These results indicate the importance of 25(OH)D level as a racially independent predictor of UCB cellular characteristics and support further investigation of bioactive vitamin D and other predictors of hematopoiesis on cord blood quality.

African American adult apheresis donors respond to granulocyte-colony-stimulating factor with neutrophil and progenitor cell yields comparable to those of Caucasian and Hispanic donors.

BACKGROUND: Granulocyte-colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cells (PBPCs) are the most common source of cells used for hematopoietic transplantation. Benign ethnic neutropenia has been found in persons of African descent, affecting circulating white blood cells (WBCs), but not WBC production within marrow. Persons of African descent have reduced neutrophil mobilization after steroid administration, and newborns have fewer nucleated and progenitor cells in their cord blood. STUDY DESIGN AND METHODS: Twenty-two African American (AA) and 12 Hispanic PBPC donors were age, sex, and weight matched with 34 Caucasian donors. Groups were compared based on WBC and neutrophil counts after mobilization and numbers of CD34+ cells collected on Day 5 of G-CSF mobilization. RESULTS: AA donors had significantly lower baseline WBC (6.1±1.1 vs. 7.1±1.7, p=0.04) and neutrophil (3.4±1.1 vs. 4.5±1.3, p=0.01) counts compared to matched Caucasian donors. G-CSF-stimulated AAs had a significantly greater increase in WBC and neutrophil counts compared to matched Caucasians (889±293% vs. 665±230% neutrophils, p=0.02). There was no significant difference in product cell counts when comparing total nucleated, CD3+, CD34+, and mononuclear cells or colony-forming units (CFUs) between Caucasians and Hispanics or AAs and trends to greater numbers of neutrophils in products from AA donors. CONCLUSION: When stimulated by G-CSF, AAs are able to increase WBC and neutrophil counts to a higher degree than Caucasians, achieving similar numbers of neutrophil and progenitor cells in apheresis products despite starting from lower baseline blood counts.

Characteristics of thawed autologous umbilical cord blood.

BACKGROUND: Autologous umbilical cord blood (AutoUCB) has historically been cryopreserved for potential use in hematopoietic transplantation. Increasingly, private AutoUCB banking is performed for therapies unavailable today. A Phase I trial using AutoUCB treatment for early pediatric Type 1 diabetes afforded us an opportunity to analyze characteristics of AutoUCBs. STUDY DESIGN AND METHODS: Twenty AutoUCBs from AABB-accredited private cord blood banks (CBBs) were evaluated for collection, processing, cryopreservation, and thaw characteristics. Using a standardized thaw-wash method, AutoUCBs were assessed for viable total nucleated cells (vTNCs), viable CD34+ (vCD34+), and colony-forming unit-granulocyte-macrophage counts. Postthaw %vTNC recoveries were compared against processing characteristics and analyzed according to processing method, cryopreservation volume, concentration, container, and length of storage. RESULTS: AutoUCB collection volumes (19.9-170 mL), cryopreserved TNC counts (7.6 × 10(7) -3.34 × 10(9)), %TNC processing recoveries (39%-100%), postthaw %vTNC recoveries (58%-100%), and %vCD34+ recoveries (26%-96%) varied widely. Regarding cell dose requirements, only 11% of evaluable AutoUCBs achieved the minimum TNC count of at least 9.0 × 10(8) to meet the National Cord Blood Inventory banking threshold, and only 50% met the minimum of 5.0 × 10(8) TNC count for Food and Drug Administration cord blood licensure eligibility. %vTNC recoveries correlated with %vCD34+ recoveries (R = 0.7; p = 0.03). Length of storage, cryopreservation volume, concentration, and container type did not affect postthaw %vTNC recoveries. CBB processing method, however, was associated with %vTNC postprocessing recoveries, with unmanipulated and plasma-depleted AutoUCBs having the highest postthaw %vTNC recovery, followed by RBC-depleted and density gradient-separated AutoUCBs. CONCLUSION: The high variability and low counts found in AutoUCB banking suggest that further standardization of characterization, collection, and processing procedures is needed.

Expansion of Human Tregs from Cryopreserved Umbilical Cord Blood for GMP-Compliant Autologous Adoptive Cell Transfer Therapy.

Umbilical cord blood is a traditional and convenient source of cells for hematopoietic stem cell transplantation. Thymic regulatory T cells (Tregs) are also present in cord blood, and there is growing interest in the use of autologous Tregs to provide a low-risk, fully human leukocyte antigen (HLA)-matched cell product for treating autoimmune diseases, such as type 1 diabetes. Here, we describe a good manufacturing practice (GMP)-compatible Treg expansion protocol using fluorescence-activated cell sorting, resulting in a mean 2,092-fold expansion of Tregs over a 16-day culture for a median yield of 1.26 × 109 Tregs from single-donor cryopreserved units. The resulting Tregs passed prior clinical trial release criteria for Treg purity and sterility, including additional rigorous assessments of FOXP3 and Helios expression and epigenetic analysis of the FOXP3 Treg-specific demethylated region (TSDR). Compared with expanded adult peripheral blood Tregs, expanded cord blood Tregs remained more naive, as assessed by continued expression of CD45RA, produced reduced IFN-γ following activation, and effectively inhibited responder T cell proliferation. Immunosequencing of the T cell receptor revealed a remarkably diverse receptor repertoire within cord blood Tregs that was maintained following in vitro expansion. These data support the feasibility of generating GMP-compliant Tregs from cord blood for adoptive cell transfer therapies and highlight potential advantages in terms of safety, phenotypic stability, autoantigen specificity, and tissue distribution.