Human Tregs Made Antigen Specific by Gene Modification: The Power to Treat Autoimmunity and Antidrug Antibodies with Precision

Abstract

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.

Keywords: B cell antibody receptors; Tregs; antigen-specific Tregs; chimeric antigen receptor; experimental autoimmune encephalomyelitis; hemophilia A; human regulatory CD4+ T cells.

Figure 1

Types of gene-modified antigen-specific human regulatory CD4⁺ T cells (Tregs). Antigen-specific (A) T-cell receptor (TCR), (B) chimeric antigen receptor (CAR), and (C) B-cell antibody receptor (BAR) Tregs have been designed by the Scott lab as potential therapeutics to ameliorate autoimmune diseases and/or immune responses to biotherapeutics in monogenic diseases, for example. TCR, CAR, and BAR Tregs each have unique properties that can be exploited as treatments geared to the different pathophysiologies of such diseases and/or adverse immune responses. The structure and targeting moieties/cells of TCR, CAR, and BAR Tregs are briefly described and depicted.

Figure 2

Overview of gene-modified antigen-specific human Treg therapy. Patient (or normal donor) blood is collected, and Tregs are sorted from buffy coat, and virally transduced to express specific receptors [T-cell receptor (TCR), chimeric antigen receptor, or B-cell antibody receptor]. The antigen-specific Tregs are then sorted and expanded in the presence of autologous peripheral blood mononuclear cells (PBMCs), anti-CD3, and oligodeoxynucleotides (ODN), which stabilize Treg functional characteristics during expansion. The antigen-specific Tregs that meet robust GMP standards and Treg phenotype are then infused back into the patient tracking of the Tregs in vivo can be performed by deuterium labeling or GFP expression. Safety constructs that trigger the ablation or death of the infused antigen-specific Tregs can also be integrated, and gene editing by CRISPR/Cas9, e.g., used to remove endogenous TCRs or MHC to avoid graft versus host disease or rejection, respectively, of generic donor T cells.