BackgroundMultiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS). One potential therapeutic strategy for MS is to induce regulatory cells that mediate immunological tolerance. Probiotics, including lactobacilli, are known to induce immunomodulatory activity with promising effects in inflammatory diseases. We tested the potential of various strains of lactobacilli for suppression of experimental autoimmune encephalomyelitis (EAE), an animal model of MS.Methodology/Principal FindingsThe preventive effects of five daily-administered strains of lactobacilli were investigated in mice developing EAE. After a primary screening, three Lactobacillus strains, L. paracasei DSM 13434, L. plantarum DSM 15312 and DSM 15313 that reduced inflammation in CNS and autoreactive T cell responses were chosen. L. paracasei and L. plantarum DSM 15312 induced CD4+CD25+Foxp3+ regulatory T cells (Tregs) in mesenteric lymph nodes (MLNs) and enhanced production of serum TGF-β1, while L. plantarum DSM 15313 increased serum IL-27 levels. Further screening of the chosen strains showed that each monostrain probiotic failed to be therapeutic in diseased mice, while a mixture of the three lactobacilli strains suppressed the progression and reversed the clinical and histological signs of EAE. The suppressive activity correlated with attenuation of pro-inflammatory Th1 and Th17 cytokines followed by IL-10 induction in MLNs, spleen and blood. Additional adoptive transfer studies demonstrated that IL-10 producing CD4+CD25+ Tregs are involved in the suppressive effect induced by the lactobacilli mixture.Conclusions/SignificanceOur data provide evidence showing that the therapeutic effect of the chosen mixture of probiotic lactobacilli was associated with induction of transferable tolerogenic Tregs in MLNs, but also in the periphery and the CNS, mediated through an IL-10-dependent mechanism. Our findings indicate a therapeutic potential of oral administration of a combination of probiotics and provide a more complete understanding of the host-commensal interactions that contribute to beneficial effects in autoimmune diseases.

Type II collagen (CII) is a target for autoreactive T cells in both rheumatoid arthritis and the murine model collagen-induced arthritis. The determinant core of CII has been identified as CII260-270, and the alteration of this T cell epitope by posttranslational modifications is known to be critical for development of arthritis in mice. Using CIIspecific T cell hybridomas we have now shown that the immunodominant T cell epitope in the normal (healthy) human and rat joint cartilage is O-glycosylated at the critical T cell receptor recognition position 264 with a mono-or di-saccharide attached to a hydroxylysine. In contrast, in the arthritic human and rat joint cartilage there are both glycosylated and non-glycosylated CII forms. Glycosylated CII from normal cartilage could not be recognized by T cells reactive to peptides having only lysine or hydroxylysine at position 264, showing that antigen-presenting cells could not degrade the O-linked carbohydrate. Thus, the variable forms of the glycosylated epitope are determined by the structures present in cartilage, and these vary during the disease course. We conclude that the chondrocyte determines the structures presented to the immune system and that these structures are different in normal versus arthritic states.

In both collagen-induced arthritis (CIA) and rheumatoid arthritis, T cells recognize a galactosylated peptide from type II collagen (CII). In this study, we demonstrate that the CII259–273 peptide, galactosylated at lysine 264, in complex with Aq molecules prevented development of CIA in mice and ameliorated chronic relapsing disease. In contrast, nonglycosylated CII259–273/Aq complexes had no such effect. CIA dependent on other MHC class II molecules (Ar/Er) was also down-regulated, indicating a bystander vaccination effect. T cells could transfer the amelioration of CIA, showing that the protection is an active process. Thus, a complex between MHC class II molecules and a posttranslationally modified peptide offers a new possibility for treatment of chronically active autoimmune inflammation such as rheumatoid arthritis.

T cells obtained in a mouse model for rheumatoid arthritis are activated by a glycopeptide fragment from rat type II collagen (CII) bound to the class II major histocompatibility complex Aq molecule. We report a comparative model of Aq in complex with the glycopeptide CII260-267. This model was used in a structure-based design approach where the amide bond between Ala261 and Gly262 in the glycopeptide was selected for replacement with psi[COCH2], psi[CH2NH2+], and psi[(E)-CH=CH] isosteres. Ala-Gly isostere building blocks were then synthesized and introduced in CII260-267 and CII259-273 glycopeptides. The modified glycopeptides were evaluated for binding to the Aq molecule, and the results were interpreted in view of the Aq/glycopeptide model. Moreover, recognition by a panel of T-cell hybridomas revealed high sensitivity for the backbone modifications. These studies contribute to the understanding of the interactions in the ternary Aq/glycopeptide/T-cell receptor complexes that activate T cells in autoimmune arthritis and suggest possibilities for new vaccination approaches.