Human regulatory CD4+ T cells (Tregs) are potent immunosuppressive lymphocytes responsible for immune tolerance and homeostasis. Since the seminal reports identifying Tregs, vast research has been channeled into understanding their genesis, signature molecular markers, mechanisms of suppression, and role in disease. This research has opened the doors for Tregs as a potential therapeutic for diseases and disorders such as multiple sclerosis, type I diabetes, transplantation, and immune responses to protein therapeutics, like factor VIII. Seminal clinical trials have used polyclonal Tregs, but the frequency of antigen-specific Tregs among polyclonal populations is low, and polyclonal Tregs may risk non-specific immunosuppression. Antigen-specific Treg therapy, which uses genetically modified Tregs expressing receptors specific for target antigens, greatly mitigates this risk. Building on the principles of T-cell receptor cloning, chimeric antigen receptors (CARs), and a novel CAR derivative, called B-cell antibody receptors, our lab has developed different types of antigen-specific Tregs. This review discusses the current research and optimization of gene-modified antigen-specific human Tregs in our lab in several disease models. The preparations and considerations for clinical use of such Tregs also are discussed.
The role of the T cell receptor (TCR) in antigen recognition and activation of T lymphocytes is well established. However, how the TCR affects T-helper differentiation/skewing is less well understood, particularly for human CD4+ (CD4) T cell subsets. Here we investigate the role of TCR specific antigen avidity in differentiation and maintenance of human Th1, Th2 and Th17 subsets. Two human TCRs, both specific for the same peptide antigen but with different avidities, were cloned and expressed in human CD4 T cells. These TCR engineered cells were then stimulated with specific antigen in unskewed and T-helper skewed conditions. We show that TCR avidity can control the percentage of IL-4 and IFN-γ co-expression in unskewed TCR engineered cells, that effector function can be maintained in a TCR avidity-dependent manner in skewed TCR engineered cells, and that increased TCR avidity can accelerate Th1 skewing of TCR engineered cells.
We recently demonstrated that expanded human CD4 T cells can be transduced to express TCRs specific for a given epitope. These cells proliferate and secrete cytokines in response to their cognate peptide/MHC. Herein, we examined whether TCR- transduced cells could be skewed to different T-helper subsets, or alternatively if previously skewed T cells could be modulated after transduction. Two HLA DR1-restricted TCRs were cloned from Th2 and Th17/Th1-type CD4+ T-cell clones specific for a coagulation factor VIII peptide (pC2). Engineered CD4+ T cells expressing these TCRs exhibited different proliferation kinetics during titration with pC2. All pC2-stimulated cells expressed IFN-g, IL-4, and IL-2 intracellularly but did not express cytokine signatures characteristic of their parental Th2 and Th17/Th1 clones. CD45RA+ and CD45RA- T cells were skewed to Th1, Th2 or Th17 and then transduced with each of the 2 TCRs. The higher-avidity TCR cells that were skewed to Th2 and then stimulated with low [pC2] maintained a Th2 cytokine signature, whereas the same cells stimulated with higher [pC2] expressed lower levels of IL-4 and GATA3. In contrast, Th1, Th17 and Th0-skewed cells transduced with the same TCR expressed their respective cytokines at all pC2 doses. Differences between the low-avidity TCR-engineered cells were less pronounced. These studies will inform our strategies for designing novel T-helper cellular therapies.
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