Abstract
Clinical scale depletion of CD45RA+ naïve T cells from leukapheresis collections can be achieved using CliniMACS (Bone Marrow Transplant. 2013, 1-7). In this study, PBSC collections depleted of CD45RA+ cells were infused as part of CT treatment protocols for pediatric patients with hematologic malignancies and solid tumors in 2 separate clinical trials. Between Sep 2012 and May 2014, a total of 25 CD45RA+ cell depletion procedures was performed for 25 patients. Mobilized PBSC leukapheresis units were collected (using Spectra) from HLA haplo-identical donors and held overnight in cold prior to cell selection. Characterization of the products before and after CD45RA+ cell depletion is shown in Table 1. Depletion of all CD45RA+ cell averaged to 3.39-log while depletion of CD3+CD45RA+ T cells was > 3.76-log, as this subset of cells became undetectable in 8 (out of 25) final products. CD34+ cell recovery was 65.4%, similar to that of CD3+CD45RO+ T cells (65.1%), which constituted > 99% of all T cells after depletion. From the PBSC collection, each patient received a median dose of 0.009 x 106 CD3+CD45RA+ cells/kg and 11.1 x 106 CD34+ cells/kg. The final product contained a substantial amount of CD14+ monocytes (median = 22.0%, range: 7.0 – 46.4), few CD56+ NK cells (3.1%, range: 1.3 – 8.1) and almost no CD19+ B cells (0.04%, range: 0.01 – 0.30). After processing the cells were resuspended in Plasmalyte + 5% human serum albumin and infused as soon as possible. There was no reported contamination (growth of bacteria – aerobic or anaerobic and fungus) in the final cell products and no infusion related adverse events were observed. In conclusion, we have demonstrated clinical scale depletion of naïve T cells can be achieved consistently and the final cell product can be safely infused into patients as part of HSCT and / or CT program.
Cell Populations (Median & ranges) Before and After CD45+ Cell Depletion
| . | Before Depletion . | After Depletion . |
|---|---|---|
| Total Nucleated Cells | 3.97 x 1010 (1.55 – 6.60) | 1.47 x 1010 (0.43 – 2.92) |
| % CD34+ Cells | 0.85% (0.29 – 2.30) | 1.45% (0.32 – 4.63) |
| % CD3+ T Cells | 22.8% (11.5 – 50.9) | 13.1% (3.9 – 37.7) |
| % CD45RA+ Cells | 39.6% (27.2 – 64.1) | 0.05% (0.01 – 0.79) |
| % CD3+ CD45RA+ Naïve T Cells | 12.3% (4.3 – 29.2) | 0.01% (0 – 3.42) |
| % CD3+ CD45RO+ Memory T Cells | 6.5% (2.0 – 15.6) | 13.0% (3.9 – 37.5) |
| . | Before Depletion . | After Depletion . |
|---|---|---|
| Total Nucleated Cells | 3.97 x 1010 (1.55 – 6.60) | 1.47 x 1010 (0.43 – 2.92) |
| % CD34+ Cells | 0.85% (0.29 – 2.30) | 1.45% (0.32 – 4.63) |
| % CD3+ T Cells | 22.8% (11.5 – 50.9) | 13.1% (3.9 – 37.7) |
| % CD45RA+ Cells | 39.6% (27.2 – 64.1) | 0.05% (0.01 – 0.79) |
| % CD3+ CD45RA+ Naïve T Cells | 12.3% (4.3 – 29.2) | 0.01% (0 – 3.42) |
| % CD3+ CD45RO+ Memory T Cells | 6.5% (2.0 – 15.6) | 13.0% (3.9 – 37.5) |
No relevant conflicts of interest to declare.
Author notes
Asterisk with author names denotes non-ASH members.
