Recombinant TCR Ligand Induces Early TCR Signaling and a Unique Pattern of Downstream Activation

Abstract

Recombinant TCR ligands (RTLs) consisting of covalently linked α1 and β1 domains of MHC class II molecules tethered to specific antigenic peptides represent minimal TCR ligands. In a previous study we reported that the rat RTL201 construct, containing RT1.B MHC class II domains covalently coupled to the encephalitogenic guinea pig myelin basic protein (Gp-MBP72–89) peptide, could prevent and treat actively and passively induced experimental autoimmune encephalomyelitis in vivo by selectively inhibiting Gp-MBP72–89 peptide-specific CD4+ T cells. To evaluate the inhibitory signaling pathway, we tested the effects of immobilized RTL201 on T cell activation of the Gp-MBP72–89-specific A1 T cell hybridoma. Activation was exquisitely Ag-specific and could not be induced by RTL200 containing the rat MBP72–89 peptide that differed by a threonine for serine substitution at position 80. Partial activation by RTL201 included a CD3ζ p23/p21 ratio shift, ZAP-70 phosphorylation, calcium mobilization, NFAT activation, and transient IL-2 production. In comparison, anti-CD3ε treatment produced stronger activation of these cellular events with additional activation of NF-κB and extracellular signal-regulated kinases as well as long term increased IL-2 production. These results demonstrate that RTLs can bind directly to the TCR and modify T cell behavior through a partial activation mechanism, triggering specific downstream signaling events that deplete intracellular calcium stores without fully activating T cells. The resulting Ag-specific activation of the transcription factor NFAT uncoupled from the activation of NF-κB or extracellular signal-regulated kinases constitutes a unique downstream activation pattern that accounts for the inhibitory effects of RTL on encephalitogenic CD4+ T cells.

A Promising Therapeutic Approach for Multiple Sclerosis: Recombinant T-Cell Receptor Ligands Modulate Experimental Autoimmune Encephalomyelitis by Reducing Interleukin-17 Production and Inhibiting Migration of Encephalitogenic Cells into the CNS

“…RTLs were shown to signal directly through the T-cell receptor (TCR) as a partial agonist and could prevent and treat active or passive myelin basic protein (MBP)-induced monophasic EAE in Lewis rats (Burrows et al, 1998;Wang et al, 2003), myelin oligodendrocyte glycoprotein (MOG)-induced chronic EAE in DR2 transgenic mice , and proteolipid protein (PLP)-induced relapsing EAE in SJL/J mice. RTL constructs derived from DR2 (Haines et al, 1996) inhibited activation but induced interleukin-10 (IL-10) secretion in human DR2-restricted T-cell clones specific for MBP-85-99 or cABL (BCR-ABL b3a2) peptides Chang et al, 2001).…”

Synthetic Peptide Dendrimers Block the Development and Expression of Experimental Allergic Encephalomyelitis

“…Both of these reagents have been suggested to alter the course of EAE by interacting directly at the cell surface of either the effector T cell or the APC. RTLs are proposed to act directly with specific TCR (17), whereas the linear multiple peptides may exert their effect by directly cross-linking MHC class II molecules on the surface of APCs (14,18).…”

Monomeric Recombinant TCR Ligand Reduces Relapse Rate and Severity of Experimental Autoimmune Encephalomyelitis in SJL/J Mice through Cytokine Switch

“…These constructs signal directly through the TCR as a partial agonist (10), prevented and treated MBPinduced monophasic EAE in Lewis rats (11,12), inhibited activation but induced IL-10 secretion in human DR2-restricted T cell clones specific for MBP 85-99 or cABL peptides (13,14), and reversed chronic clinical and histological EAE induced by MOG 35-55 peptide in DR2 transgenic mice (15). To further evaluate the therapeutic properties of recombinant TCR ligands (RTLs), we designed and tested an RTL for use in SJL mice that develop a relapsing form of EAE after injection with PLP 139-151 peptide in CFA.…”