Rebuilding human leukocyte antigen class II-restricted minor histocompatibility antigen specificity in recall antigen-specific T cells by adoptive T cell receptor transfer: Implications for adoptive immunotherapy

Purpose: Donor T cells directed to hematopoietic minor histocompatibility antigens (mHag) are appealing tools for adoptive immunotherapy of hematological malignancies after allogeneic stem cell transplantation (allo-SCT). Toward the development of a convenient strategy for ex vivo generation of human leukocyte antigen (HLA) class II-restricted mHag-specific T cells, we evaluated the feasibility of rebuilding mHag-specific T cell functions in donor-derived recall antigen-specific T cells via T cell receptor (TCR) transfer. Experimental Design: TCR α- and β-chains of an HLA-DPB1 *0401-restricted T-cell clone recognizing a multiple myeloma-associated mHag were retrovirally transferred into a tetanus toxoid (TT)-specific clone derived from the original stem cell donor. TCR double-transduced cells were compared with the parent mHag- and TT-specific clones for antigen specificity, cytokine secretion, and cytotoxic activity and were analyzed for their in vitro expansion capacity in a TT- or mHag-specific fashion. Results: mHag-TCR-transduced TT-specific cells displayed both TT and mHag specificity. Similar to the parent cells, they secreted Th-1 cytokines and exerted significant cytotoxic activity against TT-pulsed or mHag⁺ target cells, including multiple myeloma cells. A 4-week expansion of TCR-transduced cells via the TT-specific TCR had no negative influence on the mHag-specific cytotoxic activity and resulted in 10- to 100-fold better cell yields as compared with mHag-specific expansion. Conclusions: HLA class II-restricted, mHag-specific effector functions can be successfully reconstructed in donor-derived TT-specific T cells via TCR transfer. Effective expansion of these T cells via TT-specific TCRs illustrate the suitability of this strategy for ex vivo expansion and possibly for in vivo TT-specific reboosting of HLA class II-restricted immunotherapeutic T cells.