Induction and suppression of an autoimmune disease by oligomerized T cell epitopes: enhanced in vivo potency of encephalitogenic peptides

T cell epitope peptides derived from proteolipid protein (PLP139-151) or myelin basic protein (MBP86-100) induce experimental autoimmune encephalomyelitis (EAE) in "susceptible" strains of mice (e.g., SJL/J). In this study, we show that the encephalitogenic effect of these epitopes when injected subcutaneously in complete Freund's adjuvant was significantly enhanced if administered to the animal in a multimerized form as a T cell epitope oligomer (i.e., as multiple repeats of the peptide epitope, such as 16-mers). Oligomer-treated SJL/J mice developed EAE faster and showed a more severe progression of the disease than animals treated with peptide alone. In addition, haplotype-matched B10.S mice, "resistant" to EAE induction by peptide, on injection of 16-mers developed a severe form of EAE. Even more striking, however, was the dramatic suppression of incidence and severity of the disease, seen after single intravenous injections of only 50 microg of the PLP139-151 16-mer, administered to SJL/J mice 7 d after the induction of the disease. Although relapse occurred at about day 45, an additional injection several days before that maintained the suppression. Importantly, the specific suppressive effect of oligomer treatment was also evident if EAE was induced with spinal cord homogenate instead of the single peptide antigen. By contrast, the PLP139-151 peptide accelerated rather than retarded the progression of disease

Immune modulation and prevention of autoimmune disease by repeated sequences from parasites linked to self antigens

Parasite proteins containing repeats are essential invasion ligands, important for their ability to evade the host immune system and to induce immunosuppression. Here, the intrinsic suppressive potential of repetitive structures within parasite proteins was exploited to induce immunomodulation in order to establish self-tolerance in an animal model of autoimmune neurological disease. We tested the tolerogenic potential of fusion proteins containing repeat sequences of parasites linked to self-antigens. The fusion constructs consist of a recombinant protein containing repeat sequences derived from the S-antigen protein (SAg) of Plasmodium falciparum linked to a CD4 T cell epitope of myelin. They were tested for their efficacy to control the development of experimental autoimmune encephalomyelitis (EAE), In addition, we used the DO11.10 transgenic mouse model to study the immune mechanisms involved in tolerance induced by SAg fusion proteins. We found that repeated sequences of P. falciparum SAg protein linked to self-epitopes markedly protected mice from EAE. These fusion constructs were powerful tolerizing agents not only in a preventive setting but also in the treatment of ongoing disease. The tolerogenic effect was shown to be antigen-specific and strongly dependent on the physical linkage of the T cell epitope to the parasite structure and on the action of anti-inflammatory cytokines like IL-10 and TGF-{beta}. Other mechanisms include down-regulation of TNF-{alpha} accompanied by increased numbers of FoxP3(+) cells. This study describes the use of repetitive structures from parasites linked to defined T cell epitopes as an effective method to induce antigen-specific tolerance with potential applicability for the treatment and prevention of autoimmune diseases

Design of protease-resistant myelin basic protein-derived peptides by cleavage site directed amino acid substitutions

Multiple Sclerosis (MS) is considered to be a T cell-mediated autoimmune disease. An attractive strategy to prevent activation of autoaggressive T cells in MS, is the use of altered peptide ligands (APL), which bind to major histocompatibility complex class II (MHC II) molecules. To be of clinical use, APL must be capable of resisting hostile environments including the proteolytic machinery of antigen presenting cells (APC). The current design of APL relies on cost- and labour-intensive strategies. To overcome these major drawbacks, we used a deductive approach which involved modifying proteolytic cleavage sites in APL. Cleavage site-directed amino acid substitution of the autoantigen myelin basic protein (MBP) resulted in lysosomal protease-resistant, high-affinity binding peptides. In addition, these peptides mitigated T cell activation in a similar fashion as conventional APL. The strategy outlined allows the development of protease-resistant APL and provides a universal design strategy to improve peptide-based immunotherapeutics

Origin, structure and motifs of naturally processed MHC class II ligands

In the past few years a considerable number of naturally processed MHC class II ligands have been identified and sequenced. Most of them derive from endogenous sources, predominantly from plasma membrane proteins. Generally, they display variability in length but exhibit characteristic patterns of invariant amino acid positions, which reflect the allele-specific binding requirements. As a general feature, class II ligands also often contain a pattern of proline residues interpreted as a 'processing motif'

Aenderung des Beladungszustandes von MHC-Molekuelen [Change of the load state of MHC molecules]

The invention relates to a method for changing the load state of MHC molecules with ligands, whereby the change of the load state is catalyzed by a compound of the formulae (I), (IA), (II), (III) or (IV1) to (IV3). The invention also relates to the use of the compounds of formulae (I), (IA), (II), (III) or (IV1) to (IV3) or to the use of MHC molecules that are loaded with ligands, which are obtained by the inventive method, for treating diseases or conditions that are linked with various pathologically exuberant or absent immune responses, and for triggering tumor-specific, pathogen-specific or autoreactive immune responses. The invention also relates to the use of these compounds in the treatment and diagnosis of cancer, infectious diseases, autoimmune diseases and for attenuating aggressive immune reactions, and to the production of a vaccine or a pharmaceutical composition for treating the aforementioned diseases or conditions

Peptides naturally presented by MHC class I molecules

MHC class I molecules are peptide receptors of stringent specificity which however still allow millions of different ligands. This is achieved by the following specificity characteristics summarized as allele specific peptide motifs: Peptides are of defined length, depending on the class I allele (either 8 or 9 residues; exceptions have been observed). Typically, 2 of the 8 or 9 positions are anchors that can only be occupied by a single amino acid residue, or by residues with closely related side chains. Location and characteristics of anchors vary with class I alleles. The C terminus of the peptide ligands is frequently an aliphatic or charged residue. Such allele-specific class I peptide ligand motifs, known so far for H-2Kd, Kb, Kk, Kkm1, Db, HLA-A*0201, A*0205, and B*2705, are useful to predict natural T cell epitopes. The latter can be determined by extraction from cells recognized by the T cell of interest. It is not known how the class I ligands are produced in the cell, although speculative models exist. The peptide specificity of class I molecules and experimental evidence indicate that T cells are tolerant to only a small fraction of the expressed genomic sequences and are not tolerant to the remainder. The function of class I molecules is to present a collection of self-peptide samples at the cell surface for surveillance by T cells