Targeting human acute myeloid leukemia with multi-epitope specific naïvederived anti-tumor CD4+ T cells

Abstract

Abstract Little is known about the anti-tumor potential of human CD4+ T cells. Hematological malignancies constitutively expressing MHC class II could be a target for tumor-specific CD4+ T cells. We studied antigen-specific human CD4+ T cells targeting leukemia associated antigens (LAA) WT-1, PRAME, MAGEA A3 and Ny-ESO1 in vitro and in a humanized NSG mouse acute myeloid leukemia (AML) model. We hypothesized that naïve CD4+ T cells are an important source of anti-tumor T cells. Bulk and naïve CD4+ T cells isolated from the blood of normal donors were stimulated with autologous dendritic cells pulsed with overlapping 15mer peptides spanning the entire protein. After culture, naïve-derived Th cells robustly recognized LAA in most donors, while bulk-derived CD4+ T cells had negligible activity, suggesting that pre-exiting memory Th cells have a competitive advantage over LAA-specific precursors. Addition of inflammatory cytokines (IL-1, 6, 7, 21, 23 and TGF-β) further enhanced reactivity. Naïve-derived donor LAA-specific Th cells (but not control CMV pp65-specific Th cells) specifically recognized HLA-matched sibling AML blasts. After adoptive transfer LAA-specific T cells significantly reduced leukemic burden in NSG mice bearing fully-HLA matched AML. Thus, it is feasible to generate naïve-derived multi-epitope specific anti-leukemia CD4+ T cells from normal donors. Removal of competing memory Th cells and culture in inflammatory cytokines unmasks strong LAA-specific reactivity. These Th cells demonstrate highly specific recognition of naturally processed LAA in HLA-matched leukemic blasts and can control AML in vivo, establishing a foundation for CD4+ T cell immunotherapy for hematological malignancies.