In a previous study, we demonstrated that myelin oligodendrocyte glycoprotein (MOG)-35-55 peptide could induce severe chronic experimental autoimmune encephalomyelitis (EAE) in HLA-DR2+ transgenic mice lacking all mouse MHC class II genes. We used this model to evaluate clinical efficacy and mechanism of action of a novel recombinant TCR ligand (RTL) comprised of the α1 and β1 domains of DR2 (DRB1*1501) covalently linked to the encephalitogenic MOG-35-55 peptide (VG312). We found that the MOG/DR2 VG312 RTL could induce long-term tolerance to MOG-35-55 peptide and reverse clinical and histological signs of EAE in a dose- and peptide-dependent manner. Some mice treated with lower doses of VG312 relapsed after cessation of daily treatment, but the mice could be successfully re-treated with a higher dose of VG312. Treatment with VG312 strongly reduced secretion of Th1 cytokines (TNF-α and IFN-γ) produced in response to MOG-35-55 peptide, and to a lesser degree purified protein derivative and Con A, but had no inhibitory effect on serum Ab levels to MOG-35-55 peptide. Abs specific for both the peptide and MHC moieties of the RTLs were also present after treatment with EAE, but these Abs had only a minor enhancing effect on T cell activation in vitro. These data demonstrate the powerful tolerance-inducing therapeutic effects of VG312 on MOG peptide-induced EAE in transgenic DR2 mice and support the potential of this approach to inhibit myelin Ag-specific responses in multiple sclerosis patients.

Our previous studies demonstrated that oligomeric recombinant TCR ligands (RTL) can treat clinical signs of experimental autoimmune encephalomyelitis (EAE) and induce long-term T cell tolerance against encephalitogenic peptides. In the current study, we produced a monomeric I-As/PLP 139-151 peptide construct (RTL401) suitable for use in SJL/J mice that develop relapsing disease after injection of PLP 139-151 peptide in CFA. RTL401 given i.v. or s.c. but not empty RTL400 or free PLP 139-151 peptide prevented relapses and significantly reduced clinical severity of EAE induced by PLP 139-151 peptide in SJL/J or (C57BL/6 × SJL)F1 mice, but did not inhibit EAE induced by PLP 178-191 or MBP 84-104 peptides in SJL/J mice, or MOG 35-55 peptide in (C57BL/6 × SJL/J)F1 mice. RTL treatment of EAE caused stable or enhanced T cell proliferation and secretion of IL-10 in the periphery, but reduced secretion of inflammatory cytokines and chemokines. In CNS, there was a modest reduction of inflammatory cells, reduced expression of very late activation Ag-4, lymphocyte function-associated Ag-1, and inflammatory cytokines, chemokines, and chemokine receptors, but enhanced expression of Th2-related factors, IL-10, TGF-β3, and CCR3. These results suggest that monomeric RTL therapy induces a cytokine switch that curbs the encephalitogenic potential of PLP 139-151-specific T cells without fully preventing their entry into CNS, wherein they reduce the severity of inflammation. This mechanism differs from that observed using oligomeric RTL therapy in other EAE models. These results strongly support the clinical application of this novel class of peptide/MHC class II constructs in patients with multiple sclerosis who have focused T cell responses to known encephalitogenic myelin peptides.

Introduction: Chronic autoimmune uveitis is a major cause of vision loss from intraocular inflammation in humans. In this study we report that a recombinant TCR ligand (RTL220) composed of the α1 and β1 domains of MHC class II molecules linked to the uveitogenic interphotoreceptor retinoid-binding protein (IRBP) 1177–1191 peptide is effective in the suppression of acute and recurrent experimental autoimmune uveitis (EAU). Material and Methods: EAU was induced with IRBP1177–1191 peptide or by adoptive transfer of specific T cells in Lewis rats. The rats received 5 doses of RTL220 subcutaneously every other day starting at the onset of clinic signs of EAU. Results: The administration of RTL220 resulted in a delayed onset and a significant amelioration of the disease severity at clinical levels and showed protection of the retina from inflammatory damage at histological levels. In treatment of recurrent EAU, RTL220 administrated at the first or second onset of clinical disease significantly inhibited EAU, modulated immune responses and provided protection from relapses of uveitis. The systemic and local proinflammatory cytokines were significantly reduced, including IL-17. There was local and systemic increase in IL-10 and reduction in the expression of the proinflammatory chemokines CCL2, CCL3 and CCL5. Conclusions: Our studies demonstrate a successful treatment of acute and recurrent EAU with RTL220, which effectively suppressed the recurrence of inflammation and reversed clinical and histological EAU by altering cytokine and chemokine expression. These findings strongly support a possible clinical application of this novel class of peptide/MHC class II drugs for patients with autoimmune uveitis.