Cell culture methods that yield high numbers of functional antigen-specific T cells are crucial to translate adoptive T cell immunotherapy into clinics. In pre-clinical models, early differentiated memory T cell subsets showed superior engraftment, survival and function when compared to late differentiated T cell subsets. We aimed at the specific enrichment and preferential expansion of the distinctly early differentiated memory stem T cell subset (TSCM; CCR7+CD45RA+CD95+). In an explorative way, we established a Cytomegalovirus (CMV)-specific T cell culture system that investigates the influence of cytokine regimes, the addition of CD4+ T cells and the presence of regulatory T cells (TREG) on TSCM-derived T cell expansion. Here, we found that the expansion of antigen-specific TSCM-cells was diminished when bulk peripheral blood mononuclear cells were used as starting material. Specifically, we found that other memory T cell subsets inhibit the expansion of TSCM-cells. By the same token, we established that TSCM-cells expanded best when derived from pre-enriched CCR7+CD45RA+ T cells, cultured in the presence of irradiated bulk CD4+ T cells and distinct doses of IL-7 and IL-15. Surprisingly, depletion of TREG-cells significantly diminished TSCM-expansion irrespective of cytokines applied during culture. Further, post-stimulation CD45RO-selection owing to proliferation-induced CD45-isoform switch (CD45RA to CD45RO) significantly increased the purity and yield of TSCM-derived cultures. Our findings enable direct access to human antigen-specific TSCM-cells from peripheral blood and pave the way for rapid broad clinical application.
Tino Vollmer– Medical Doctoral Student, Institute for Medical Immunology, Charité University Medicine Berlin
Leila Amini– PhD candidate, Charité Universitaetsmedizin Berlin
Petra Reinke– Charité Universitaetsmedizin Berlin
Hans-Dieter Volk– Charité Universitaetsmedizin Berlin
Michael Schmueck-Henneresse– Charité Universitaetsmedizin Berlin