Adenovirus-specific T-cell Subsets in Human Peripheral Blood and After IFN-γ Immunomagnetic Selection

Adoptive antiviral cellular immunotherapy by infusion of virus-specific T cells (VSTs) is becoming an alternative treatment for viral infection after hematopoietic stem cell transplantation. The T memory stem cell (T-SCM) subset was recently described as exhibiting self-renewal and multipotency properties which are required for sustained efficacy in vivo. We wondered if such a crucial subset for immunotherapy was present in VSTs. We identified, by flow cytometry, T-SCM in adenovirus (ADV)-specific interferon (IFN)-gamma + T cells before and after IFN-gamma-based immunomagnetic selection, and analyzed the distribution of the main T-cell subsets in VSTs: naive T cells (T-N), T-SCM, T central memory cells (T-CM), T effector memory cell (T-EM), and effector T cells (T-EFF). In this study all of the different T-cell subsets were observed in the blood sample from healthy donor ADV-VSTs, both before and after IFN-gamma-based immunomagnetic selection. As the IFN-gamma-based immunomagnetic selection system sorts mainly the most differentiated T-cell subsets, we observed that T-EM was always the major T-cell subset of ADV-specific T cells after immunomagnetic isolation and especially after expansion in vitro. Comparing T-cell subpopulation profiles before and after in vitro expansion, we observed that in vitro cell culture with interleukin-2 resulted in a significant expansion of TN-like, T-CM, T-EM, and T-EFF subsets in CD4(+)IFN-gamma(+) T cells and of T-CM and T-EM subsets only in CD8(+)IFN-gamma(+) T cells. We demonstrated the presence of all T-cell subsets in IFN-gamma(+) VSTs including the T-SCM subpopulation, although this was weakly selected by the IFN-gamma-based immunomagnetic selection system.