In Vivo Induction of Regulatory T Cells Via CTLA‐4 Signaling Peptide to Control Autoimmune Encephalomyelitis and Prevent Disease Relapse

Abstract

Regulatory T cells play a key role in immune tolerance to self-antigens, thereby preventing autoimmune diseases. However, no drugs targeting Treg cells have been approved for clinical trials yet. Here, a chimeric peptide is generated by conjugation of the cytoplasmic domain of CTLA-4 (ctCTLA-4) with dNP2 for intracellular delivery, dNP2-ctCTLA-4, and evaluated Foxp3 expression during Th0, Th1, Treg, and Th17 differentiation dependent on TGF-. The lysine motif of ctCTLA-4, not tyrosine motif, is required for Foxp3 expression for Treg induction and amelioration of experimental autoimmune encephalomyelitis (EAE). Transcriptome analysis reveals that dNP2-ctCTLA-4-treated T cells express Treg transcriptomic patterns with properties of suppressive functions. In addition, the molecular interaction between the lysine motif of ctCTLA-4 and PKC-is critical for Foxp3 expression. Although both CTLA-4-Ig and dNP2-ctCTLA-4 treatment in vivo ameliorated EAE progression, only dNP2-ctCTLA-4 requires Treg cells for inhibition of disease progression and prevention of relapse. Furthermore, the CTLA-4 signaling peptide is able to induce human Tregs in vitro and in vivo as well as from peripheral blood mononuclear cells (PBMCs) of multiple sclerosis patients. These results collectively suggest that the chimeric CTLA-4 signaling peptide can be used for successful induction of regulatory T cells in vivo to control autoimmune diseases, such as multiple sclerosis.

Current Understanding of Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) Signaling in T-Cell Biology and Disease Therapy

“…Another report showed that Ctla-4 KO naïve T cells had reduced Treg-cell differentiation compared with WT T cells ( Verhagen et al, 2014 ). A peptide in the signaling motif of CTLA-4 increased Treg-cell differentiation in vitro and in EAE mice, whereas a lysine motif mutant peptide did not increase the differentiation of Treg cells ( Kim et al, 2021a ). This peptide induces nuclear translocation of mothers against decapentaplegic homolog 2/3 (SMAD2/3) by inhibiting phosphorylation of the SMAD2/3 linker region through binding to PKC-η, leading to FOXP3 induction.…”

“…It also inhibited human T-cell activation and controlled human skin graft rejection in SCID mice ( Lim et al, 2018 ). Moreover, a synthetic peptide containing the CTLA-4 cytoplasmic domain conjugated to a cell-penetrating peptide increased the differentiation of Treg cells and prevented disease relapse in EAE ( Kim et al, 2021a ). Regarding the differences between CTLA-4-Ig and the cytoplasmic domain of CTLA-4, in terms of effects on Treg-cell numbers and functions, CTLA-4-Ig has the disadvantage of sustaining immune tolerance in disease due to its reduction of Treg-cell numbers; however, CTLA-4 signaling peptide increases Treg-cell numbers, revealing a distinct mechanism for disease modulation.…”

Ozone Pollution, Oxidative Stress, Regulatory T Cells and Antioxidants

“…Treg cells are usually found decreased in autoimmune processes such as RA and systemic lupus erythematosus (SLE) [ 43 ] and due to their immunosuppressive capacity, they have become the object of study for the development of autoimmunity [ 44 ]. Much research has focused on the mechanisms to promote the induction of these cells such as the in vivo induction of Treg cells, through a chimeric peptide of CTLA-4, a critical protein for the maintenance of immunological tolerance expressed by Treg cells, resulting in the decrease in the progression of experimental autoimmune encephalitis [ 45 ]. On the other hand, the cytokine pathways involved in the proliferation and maintenance of T cells have also been explored.…”

The Role of Cytotoxic T-Lymphocyte Antigen 4 in the Pathogenesis of Multiple Sclerosis

“…Moreover, Kim et al have shown that the synthetic chimeric peptide dNP2-ctCTLA-4 induced Foxp3 + Tregs in mouse and human PBMC, and it can attenuate EAE progression with long-term regulation and prevent relapse [ 108 ]. In particular, dNP2-ctCTLA-4 can control TGF-β signaling to augment Foxp3 expression during the Th1 or Th17 differentiation and expression of functional molecules, including CTLA-4 [ 108 ]. Therefore, this peptide seems to be an interesting potential drug to raise the number of Tregs in autoimmune disorders, including MS.…”

“…Therefore, this peptide seems to be an interesting potential drug to raise the number of Tregs in autoimmune disorders, including MS. Female animals were used for the experiments [ 108 ].…”