A Novel Strategy for Generation of Human Tumor-Specific T Cell Clones for Adoptive Transfer.

Adoptive T-cell therapy using donor lymphocyte infusions is a promising approach for treating hematological malignancies. But, efficacy is limited by the induction of graft-versus-host disease. Transfer of tumor-specific T-cell clones could enhance the graft-versus-tumor effect and eliminate graft-versus-host disease. However, isolating antigen-specific T-cell clones by the traditional limiting dilution approach is a time-consuming and laborious process. Here, we describe a novel strategy for rapidly cloning tumor-specific T cells. Lymphoma-specific T-cell lines were generated from two follicular lymphoma patients by repeated in vitro stimulation of lymphocytes isolated from tumor or blood with autologous soluble CD40 ligand-activated tumor cells. After four in vitro stimulations at 10-day intervals in the presence of IL-2 and IL-15, T-cell lines were found to be predominantly CD4⁺ T cells and produced significant amounts of TNF-a, GM-CSF, and IFN-γ in response to autologous tumor cells. The tumor reactivity was MHC class II restricted suggesting that it was mediated by CD4⁺ T cells. Staining with a TCR Vb antibody panel, a set of monoclonal antibodies against 24 human TCR Vb families, revealed that certain Vb families were overrepresented in each CD4⁺ T-cell line. In patient 1, 51% of CD4⁺ T cells were Vb1 positive, and in patient 2, 27% of CD4⁺ T cells were Vb8 positive. To clone lymphoma-specific T cells, CD4⁺ T-cell lines were labeled with CFSE and stimulated with autologous tumor cells. After 9 days of in vitro expansion in the presence of IL-2 and IL-15, CD4⁺ T-cell lines were stained with an anti-human CD4-APC monoclonal antibody and an anti-human TCR Vb-PE monoclonal antibody for each CD4⁺ T-cell line. Proliferating Vb1 cells from patient 1 and Vb8 cells from patient 2 were identified by their reduction in CFSE staining, and CD4⁺TCRV b ⁺CFSE^dim cells were sorted by flow cytometer. Monoclonality of the sorted cells was confirmed by PCR using a panel of optimized primers specific for 24 TCR Vb families, by TCR Vb spectratype analysis, and finally, by sequencing the TCR Vb gene used by each T-cell clone. Sorted tumor-specific T-cell clones could be expanded to large numbers using a 14-day rapid expansion protocol with allofeeder PBMCs, and confirmed to retain specificity against autologous tumor cells in a cytokine induction assay. This approach was also successfully used to isolate melanoma-specific CD8⁺ T-cell clones from two patients. We conclude that this approach is highly reproducible, rapid, and efficient for generating antigen-specific T-cell clones for adoptive T-cell therapy against human malignancies in the autologous or allogeneic setting.