Bet v 1–specific T-cell receptor/forkhead box protein 3 transgenic T cells suppress Bet v 1–specific T-cell effector function in an activation-dependent manner

Background Regulatory T (Treg) cells establish and maintain tolerance to self-antigens and many foreign antigens, such as allergens, by suppressing effector T-cell proliferation and function. We have previously shown that human T-cell receptor (TCR) αβ-chains specific for allergen-derived epitopes confer allergen specificity on peripheral blood T cells of individuals with and without allergy. Objective To study the feasibility of generating allergen-specific human Treg cells by retroviral transduction of a transcription unit encoding forkhead box protein 3 (FOXP3) and allergen-specific TCR αβ- chains. Methods cDNAs encoding the α and β −chains of a Bet v 1142-153 −specific TCR (TCR alpha variable region 6/TCR beta variable region 20) and human FOXP3 were linked via picornaviral 2A sequences and expressed as single translational unit from an internal ribosomal entry site—green fluorescence protein−containing retroviral vector. Retrovirally transduced peripheral blood T cells were tested for expression of transgenes, Treg phenotype, and regulatory capacity toward allergen-specific effector T cells. Results Transduced T cells displayed a Treg phenotype with clear-cut upregulation of CD25, CD39, and cytotoxic T-lymphocyte antigen 4. The transduced cells were hyporesponsive in cytokine production and secretion and, like naturally occurring Treg cells, did not proliferate after antigen-specific or antigen-mimetic stimulation. However, proliferation was inducible upon exposure to exogenous IL-2. In coculture experiments, TRAV6+ TRBV20+ FOXP3+ transgenic T cells, unlike FOXP3+ single transgenic T cells or naturally occurring Treg cells, highly significantly suppressed T cell cytokine production and proliferation of corresponding allergen-specific effector T cells in an allergen-specific, dose-dependent manner. Conclusion We demonstrate a transgenic approach to engineer human allergen-specific Treg cells that exert their regulatory function in an activation-dependent manner. Customized Treg cells might become useful for tolerance induction therapies in individuals with allergic and other immune-mediated diseases.