Impaired Functionality of Antiviral T Cells in G-CSF Mobilized Stem Cell Donors: Implications for the Selection of CTL Donor

Carola E Bunse,Lilia Goudeva,Ulrike Köhl,Ulrich Kalinke,Pavankumar R Varanasi,Britta Eiz-Vesper,Constança Figueiredo,Britta Maecker-Kolhoff,Sabine Tischer,Arnold Ganser,Sylvia Borchers,Eva M Weissinger,Rainer Blasczyk,Stephan Immenschuh,Simona Stager

doi:10.1371/journal.pone.0077925

Abstract

Adoptive transfer of antiviral T cells enhances immune reconstitution and decreases infectious complications after stem cell transplantation. Information on number and function of antiviral T cells in stem cell grafts is scarce. We investigated (1) immunomodulatory effects of G-CSF on antiviral T cells, (2) the influence of apheresis, and (3) the optimal time point to collect antiviral cells.CMV-, EBV- and ADV-specific T cells were enumerated in 170 G-CSF-mobilized stem cell and 24 non-mobilized platelet donors using 14 HLA-matched multimers. T-cell function was evaluated by IFN-γ ELISpot and granzyme B secretion. Immunophenotyping was performed by multicolor flow cytometry.G-CSF treatment did not significantly influence frequency of antiviral T cells nor their in vitro expansion rate upon antigen restimulation. However, T-cell function was significantly impaired, as expressed by a mean reduction in secretion of IFN-γ (75% in vivo, 40% in vitro) and granzyme B (32% target-independent, 76% target-dependent) as well as CD107a expression (27%). Clinical follow up data indicate that the first CMV-reactivation in patients and with it the need for T-cell transfer occurs while the donor is still under the influence of G-CSF.To overcome these limitations, T-cell banking before mobilization or recruitment of third party donors might be an option to optimize T-cell production.

Highlights

Peripheral blood stem cells (PBSCs), which can be collected after granulocyte colony-stimulating factor (G-CSF) treatment, have been increasingly used for allogeneic stem cell transplantation in recent years [1]
To further clarify the effects of G-CSF on donor T cells, we addressed the questions of whether (1) multimer monitoring and detection of interferon-gamma (IFN-c)-secreting cells by enzymelinked immunospot (ELISpot)-based technique after short-term antigen stimulation are suitable tools to evaluate antiviral cytotoxic T lymphocytes (CTLs) in various samples from stem cell donors, (2) G-CSF mobilization and apheresis influence antiviral T-cell levels, and (3) G-CSF treatment influences the functional activity of CTLs both in vivo and in vitro
Our results demonstrate that antiviral T-cell function is impaired after in vivo G-CSF treatment

Summary

Introduction

Peripheral blood stem cells (PBSCs), which can be collected after granulocyte colony-stimulating factor (G-CSF) treatment, have been increasingly used for allogeneic stem cell transplantation in recent years [1]. Apart from GvHD, infectious complications of persistent viruses like cytomegalovirus (CMV), Epstein-Barr virus (EBV) and adenovirus (ADV) remain a problem [6]. Several studies have employed adoptive transfer of antiviral CTLs against CMV [10,11,12,13], EBV [14,15,16] and ADV [17] and good treatment outcomes were achieved. The main problem of this approach is the source for virus-reactive T cells, as the patients at highest risk of viral complications are those transplanted from seronegative donors [18]. Apart from determining the patient’s and donor’s serostatus, multimer-based monitoring of antiviral T cells helps to identify high-risk patients in need of adoptive therapies [18,20,21]. The number of virus-specific donor T cells transferred with the stem cell graft may play a role in patients with seropositive donors by providing early protection against

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