HR-04. CD45RA– fraction reinfusion impact on the T-cell subpopulations of the bone marrow in patients after allogeneic hematopoietic stem cell transplantation from a haploidentical donor with TCRαβ depletion

Summary

Introduction

Given the limited number of donor registries in the Russian Federation, it is becoming increasingly common to use a haploidentical transplantation. Currently, there are several approaches, including the TCRαβ depletion method (Maschan M.A., et al), which has come from paediatric practice, when performing haploidentical transplantation. One of the features of this procedure is a scheduled reinfusion of CD45RA fraction on days 0, +30, +60, +90 after the transplant. Despite its effectiveness shown in some works, the impact of this reinfusion upon reconstitution and structural composition of bone marrow in adults and children remains unclear. The purpose of the present work was to evaluate the impact of CD45RA^– reinfusion upon the marrow T-cell composition in the patients after haploidentic transplantation.

Materials and methods

Nineteen patients were included in the study. All the patients were transplanted from related haploidentical donors. Ex vivo TCRαβ depletion with CD45RA^– reinfusion was performed in seven cases on the day 0, +30, +60, +90 (dose of CD45RA^– was 50*10⁴/kg), and 12 patients were also transplanted with TCRαβ depletion, without infusion of CD45RA fraction. Clinical characteristics of the patients are presented in Table 1. All the patients included into the study exhibited primary engraftment of the hematopoietic transplant. The subpopulation composition of CD4+ and CD8+ T-cells was studied in bone marrow samples on the day +30, +90 (before CD45RA^– reinfusion), +180 and +365 using flow cytometry (BD FACS Canto II, Becton Dickinson, USA). The following subpopulations were studied: T-naïve and stem memory cells (Tnv+Tscm) – CD45R0^–CCR7⁺CD28⁺; T cells of central memory (Tcm) – CD45R0⁺CCR7⁺CD28⁺; transition memory T cells (Ttm) – CD45R0⁺CCR7^–CD28⁺; T-cells of effector memory (Tem) – CD45R0⁺CCR7^–CD28^-; T-terminal effectors (Tte) – CD45R0^–CCR7^–CD28^–. Statistical analysis of data was carried out using IBM SPSS v.23 statistical software (USA). Shapiro-Wilk criterion was used to check the normal distribution of the samples under study. Due to abnormal data distribution, The Mann-Whitney U-criterion was used in analysis between the two independent samples. The p-value <0.05 was considered statistically significant.

Results

The effects of CD45RA^- fraction reinfusion upon bone marrow structure in patients after haploidentic transplantation are shown in Fig. 1 and 2. No significant differences were found between patients with CD45RA fraction reinfusion and patients without it. Thus, according to our data, the CD45RA^– fraction reinfusion on the days 0, +30, +60, +90 at a dose of 50*10⁴/kg does not significantly affect the bone marrow composition in the patients after haplo-SCT.

Conclusion

According to our previously published data, only 2.24% of transfused CD45RA cells are represented by the cells with Tcm phenotype (i.e., about 11200 transfused cells per kg of body weight). This dose is probably suboptimal to affect the structure of the bone marrow in any significant way. Although CD45RA^– reinfusion is a safe and, according to some publications, an effective method of preventing undesirable events after transplantation, the immunological effects of this intervention have yet to be evaluated with respect to further adjustment of this method for adult patients.

Keywords

Hematopoietic stem cell transplantation, haploidentical, TCR αβ-depletion, CD45RA^– reinfusion.