ISSN 1866-8836
Клеточная терапия и трансплантация

PO-08. Transplantation of TCRαβ+/CD19+ depleted hematopoietic stem cells: prediction and management of depletion depth

Alexander I. Ponomarev1,2,3, Grigory A. Tsaur1,2,3, Tatyana Yu. Verzhbitskaya1,2, Jean V. Permikin1,3, Larisa V. Vakhonina1,2, Anna A. Vlasova1, Larisa G. Fechina1,2

1 Regional Children’s Hospital, Ekaterinburg, Russia
2 Institute for Medical Cell Technologies, Ekaterinburg, Russia
3 Ural State Medical University, Ekaterinburg, Russia


Contact: Dr. Alexander I. Ponomarev, e-mail: Ponomareff@yandex.ru

doi 10.18620/ctt-1866-8836-2023-12-3-1-176

Summary

Ex vivo depletion of TCRαβ+ cells using CliniMACS plus (Miltenyi Biotec, Germany) is a widely employed procedure in haploidentical and, in certain cases, unrelated hematopoietic stem cell transplantation (HSCT). The depletion depth (TCRαβ+ lg) represents a crucial yet challenging-to-predict parameter. The aim of the study was to train and validate a predictive model for estimating the depth of TCRαβ depletion.

Patients and methods

We investigated the outcomes of 92 TCRαβ/CD19-depleted peripheral blood HSCT, performed at the Regional Children’s Hospital (Ekaterinburg, Russia) between 2017 and 2023. Patients were divided into two groups: (1) TCRαβ/CD19 depletion using Clinimacs PBS/EDTA buffer at +4°C with centrifugation at +4°C (Experimental group, n=39), and (2) conventional TCRαβ/CD19 depletion, when Clinimacs PBS/EDTA buffer was applied at room temperature and centrifugation was performed at +22°C (Control group, n=53).

Results

The recovery of post-processed CD34+ cells did not show significant difference between groups (94.4±15.1% and 93.0±11.2%, p>0.05). Conversely, TCRαβ+ lg demonstrated significant differences (p<0.0001) with values of 4.95±0.76 and 4.12±0.66 for the Experimental and Control groups, respectively. A model was fitted using all predictors, including total leukocyte count, leukapheresis product volume, absolute quantity and percentage of lymphocytes subpopulations, granulocytes, platelets (Fig. 1). Statistically significant parameters were percentage of TCRαβ+ (p=0.01) and CD19+ cells (p<0.0001), the “cold” depletion (p<0.0001). All coefficients positively correlated with TCRαβ+ lg. The model exhibited an accuracy of 97.5% (R^2=0.47) within the prediction range of 2.3 lg, completely satisfying validation requirements. The graphical representation of the model is shown in Figure 1. OS, engraftment time, probabilities of relapse, graft failure, acute and chronic GvHD, viral reactivation did not differ between groups. Examination the in vitro colony-forming activity of CD34+ cells in the methylcellulose revealed some inhibiting effect in the Experimental group across all differentiation directions (CFU/BFU-E, CFU-GM, CFU-GEMM); however, this effect did not show statistical significance compared to the Control group.

Conclusion

The proposed method for predicting and managing depletion depth, along with conducting the entire procedure at +4°C, could be advantageous in scenarios where the product’s quality post-TCRαβ+ depletion is crucial, such as in infants and young children with low body mass. However, the wide range of predictions and moderate determination coefficient in our model suggest for further exploration of additional predictors.

Keywords

Haploidentical HSCT, allogeneic TCRαβ+/CD19+ depletion.



Ponomarev-fig01.jpg

Figure 1. The Model nomogram for calculating the depth of TCRαβ+ lg depletion based on the relative content of TCRαβ+ and CD19+ cells, and the “cold” processing option

Figure Navigation: Calculate the sum of points by projecting individual vertical lines connecting the percentages of TCRαβ+ and CD19+ to the outermost upper line considering means of “cold” processing option. Prediction confidence intervals (90%) are highlighted in blue separately for each predictor and the total sum of points.
Points: Points assigned for summation estimation. TCRαβ+,%: Percentage of TCRαβ+ cells in the leukapheresis product. CD19+,%: Percentage of CD19+ cells in the leukapheresis product. “Cold” processing: option for “Cold” depletion. Total Points: Resulting sum of points estimated for all predictors. TCR αβ+ depletion,lg: Predicted depth of TCRαβ+ cell depletion, expressed in lg.

Supplement 12-3
09/30/2023

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doi 10.18620/ctt-1866-8836-2023-12-3-1-176

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