Synthetic peptides that inhibit binding of the collagen type II 261-273 epitope to rheumatoid arthritis-associated HLA-DR1 and -DR4 molecules and collagen-specific T-cell responses

A cell-based high-throughput screening assay system for inhibitor compounds of antigen presentation by HLA class II molecule

A number of autoimmune diseases are associated with the genotypes of human leukocyte antigen class II (HLA), some of which present peptides derived from self-proteins, resulting in clonal expansion of self-reactive T cells. Therefore, selective inhibition of self-peptide loading onto such disease-associated HLA could ameliorate the diseases. To effectively identify such compounds, in this study, we established, for the first time, a cell- and 96-well microplate-based high-throughput screening system for inhibitors of antigen presentation. A panel of DRB1 genes plus DRA*01:01 gene were expressed in HEK293T cells and in 3T3 cells, and their binding with biotinylated known self-antigen peptides was measured by flow cytometry. HLA-DR1 (DRB1*01:01) and DR15 (DRB1*15:01) showed a high affinity with myelin basic protein peptide (MBP83-98). Therefore, in 96-well plate wells, MBP83-99 was allowed to bind to DR1 or DR15 on 3T3 cells in competition with a test compound, and the HLA-bound peptide was detected by streptavidin-conjugated β-galactosidase, thereby identifying inhibitor compounds for rheumatoid arthritis or multiple sclerosis. Our assay system has a potential for broad applications, including designing peptide vaccines.

Design of peptide immunotherapies for MHC Class-II-associated autoimmune disorders

Autoimmune disorders, that occur when autoreactive immune cells are induced to activate their responses against self-tissues, affect one percent of the world population and represent one of the top 10 leading causes of death. The major histocompatibility complex (MHC) is a principal susceptibility locus for many human autoimmune diseases, in which self-tissue antigens providing targets for pathogenic lymphocytes are bound to HLA molecules encoded by disease-associated alleles. In spite of the attempts to design strategies for inhibition of antigen presentation targeting the MHC-peptide/TCR complex via generation of blocking antibodies, altered peptide ligands (APL), or inhibitors of costimulatory molecules, potent therapies with minimal side effects have yet to be developed. Copaxone (glatiramer acetate, GA) is a random synthetic amino acid copolymer that reduces the relapse rate by about 30% in relapsing-remitting multiple sclerosis (MS) patients. Based on the elucidated binding motifs of Copaxone and of the anchor residues of the immunogenic myelin basic protein (MBP) peptide to HLA-DR molecules, novel copolymers have been designed and proved to be more effective in suppressing MS-like disease in mice. In this report, we describe the rationale for design of second-generation synthetic random copolymers as candidate drugs for a number of MHC class-II-associated autoimmune disorders.

Emerging opportunities for site-specific molecular and cellular interventions in autoimmune hepatitis

Current corticosteroid-based treatments of autoimmune hepatitis frequently have incomplete or unsatisfactory outcomes, side effects, and excessive immune suppression. The goal of this review is to describe the advances in developing animal models of autoimmune hepatitis and in treating diverse immune-mediated diseases that make pursuit of site-specific molecular and cellular inventions in autoimmune hepatitis feasible. Prime source and review articles in English were selected by a Medline search through October 2009. A murine model infected with an adenovirus expressing human CYP2D6 is a resource for evaluating new therapies because of its histological and serological features, persistence, and progressive hepatic fibrosis. Synthetic analog peptides that block autoantigen expression, a dimeric recombinant human fusion protein of cytotoxic T lymphocyte antigen-4, monoclonal antibodies against tumor necrosis factor-alpha, recombinant interleukin 10, tolerization techniques for disease-triggering autoantigens, T regulatory cell transfer, vaccination against antigen-specific cytotoxic CD8+ T cells, and gene silencing methods using small inhibitory RNAs are feasible interventions to explore. Treatments directed at dampening immunocyte activation with soluble cytotoxic T lymphocyte antigen-4, inhibiting immunocyte differentiation with recombinant interleukin 10, and improving immunosuppressive activity with regulatory T cell modulation have the most immediate promise. Progress in the development of an animal model of autoimmune hepatitis and experiences in other immune-mediated diseases justify the evaluation of site-specific molecular and cellular interventions in this disease.

Animal models of autoimmune hepatitis

Animal models of autoimmune hepatitis have been important in defining pathogenic mechanisms, and they promise to aid in the evaluation of new molecular and cellular treatments. They have evolved from models based on crude liver homogenates that produced a transient hepatitis to models that express antibodies to human antigens, manifest liver-infiltrating T cells, persist for at least 3 months and develop fibrosis. Animal models allow the study of autoimmune hepatitis from its inception, and they can detail the progression of pathological events. Key imbalances in counter-regulatory mechanisms can be isolated and manipulated. Models can be humanized by the insertion of human genetic promoters and the expression of human antigens. Genetic engineering and preconditioning have been milestones in the evolution of animal models. Vaccination or infection of murine models with viral vectors carrying human antigens are the most recent developments. Animal models promise to extend the knowledge of etiological agents and improve treatment algorithms.

Modeling the ternary complex TCR-Vbeta/CollagenII(261-273)/HLA-DR4 associated with rheumatoid arthritis

Background

It is known that genetic predisposition to rheumatoid arthritis (RA) is associated with the MHC class II allele HLA-DR4 and that residues 261–273 of type II collagen (huCollp261) represent an immunodominant T cell epitope restricted by the DR4 molecule. Despite recent advances in characterization of MHC and T cell receptor (TCR) contacts to this epitope, the atomic details of TCR/huCollp261/HLA-DR4 ternary complex are not known.

Methodology/Principal Findings

Here we have used computational modeling to get insight into this interaction. A three-dimensional model of the TCR Vβ domain from a DR4⁺ patient affected by RA has been derived by homology modeling techniques. Subsequently, the structure of the TCR Vβ domain in complex with huCollp261/HLA-DR4 was obtained from a docking approach in conjunction with a filtering procedure based on biochemical information. The best complex from the docking experiments was then refined by 20 ns of molecular dynamics simulation in explicit water. The predicted model is consistent with available experimental data. Our results indicate that residues 97–101 of CDR3β are critical for recognition of huCollp261/HLA-DR4 by TCR. We also show that TCR contacts on p/MHC surface affect the conformation of the shared epitope expressed by DR alleles associated with RA susceptibility.

Conclusions/Significance

This work presents a three-dimensional model for the ternary complex TCR-Vβ/collagenII(261–273)/HLA-DR4 associated with rheumatoid arthritis that can provide insights into the molecular mechanisms of self reactivity.

Current and future treatments of autoimmune hepatitis

Corticosteroid therapy induces clinical, laboratory and histological improvements in 80% of patients with autoimmune hepatitis. Prednisone, alone or at a lower dose in combination with azathioprine, increases the 20-year life expectancy to 80% and prevents or reduces hepatic fibrosis in 79% of patients. The combination regimen is preferred and treatment should be considered in all patients with active disease. The duration of therapy is finite and the medication should be discontinued after resolution of all manifestations of inflammatory activity, including the histological changes. Relapse after drug withdrawal occurs in 50-79% of patients, and it should be treated with long-term azathioprine (2 mg/kg daily). Salvage therapies for individuals intolerant of or refractory to the conventional regimens include high-dose corticosteroids, with or without high-dose azathioprine, 6-mercaptopurine, mycophenolate mofetil, tacrolimus or ciclosporin. Liver transplantation should be considered in patients with hepatic failure unresponsive to corticosteroid treatment, decompensated cirrhosis with a Model for End-Stage Liver Disease score of at least 15 points, or hepatocellular carcinoma that meets transplantation criteria. Autoimmune hepatitis recurs after transplantation in at least 17% of patients, and it typically improves after adjustments in the immunosuppressive regimen. Future therapies are likely to include mesenchymal stem cell transplantation, adoptive transfer of T regulatory cells, and cytokine manipulation. The emergence of new treatments will require the development of a collaborative network of clinical and basic investigators, as the complexity and specificity of current management problems require solutions that exceed the capabilities of single institutions.

Non-classical phenotypes of autoimmune hepatitis and advances in diagnosis and treatment

Non-classical manifestations of autoimmune hepatitis can delay diagnosis and treatment. Our aims were to describe the clinical phenotypes that can confound the diagnosis, detail scoring systems that can ensure their recognition, and outline advances in treatment that can improve their outcome. Prime source and review articles in English were selected through Medline from 1970-2008 and assimilated into personal libraries spanning 32 years. Acute severe or asymptomatic presentations and atypical histological findings, including centrilobular zone 3 necrosis and concurrent bile duct changes, are compatible with the diagnosis. Cholangiographic abnormalities may be present in children and adults with the disease, and autoimmune hepatitis must be considered in patients without autoantibodies or with antimitochondrial antibodies and no other cholestatic features. Asymptomatic patients frequently become symptomatic; mild disease can progress; and there are no confident indices that justify withholding treatment. Two diagnostic scoring systems with complementary virtues have been developed to evaluate patients with confusing features. Normal liver tests and tissue constitute the optimal end point of treatment, and the first relapse is an indication for long-term azathioprine therapy. Cyclosporine, tacrolimus and mycophenolate mofetil are promising salvage therapies, and budesonide with azathioprine may be a superior frontline treatment. We conclude that the non-classical phenotypes of autoimmune hepatitis can be recognized promptly, diagnosed accurately, and treated effectively.

Functional recombinant MHC class II molecules and high-throughput peptide-binding assays

BACKGROUND

Molecules of the class II major histocompability complex (MHC-II) specifically bind and present exogenously derived peptide epitopes to CD4+ T helper cells. The extreme polymorphism of the MHC-II hampers the complete analysis of peptide binding. It is also a significant hurdle in the generation of MHC-II molecules as reagents to study and manipulate specific T helper cell responses. Methods to generate functional MHC-II molecules recombinantly, and measure their interaction with peptides, would be highly desirable; however, no consensus methodology has yet emerged.

RESULTS

We generated alpha and beta MHC-II chain constructs, where the membrane-spanning regions were replaced by dimerization motifs, and the C-terminal of the beta chains was fused to a biotinylation signal peptide (BSP) allowing for in vivo biotinylation. These chains were produced separately as inclusion bodies in E. coli , extracted into urea, and purified under denaturing and non-reducing conditions using conventional column chromatography. Subsequently, diluting the two chains into a folding reaction with appropriate peptide resulted in efficient peptide-MHC-II complex formation. Several different formats of peptide-binding assay were developed including a homogeneous, non-radioactive, high-throughput (HTS) binding assay. Binding isotherms were generated allowing the affinities of interaction to be determined. The affinities of the best binders were found to be in the low nanomolar range. Recombinant MHC-II molecules and accompanying HTS peptide-binding assay were successfully developed for nine different MHC-II molecules including the DPA1*0103/DPB1*0401 (DP401) and DQA1*0501/DQB1*0201, where both alpha and beta chains are polymorphic, illustrating the advantages of producing the two chains separately.

CONCLUSION

We have successfully developed versatile MHC-II resources, which may assist in the generation of MHC class II -wide reagents, data, and tools.

HLA-DM negatively regulates HLA-DR4-restricted collagen pathogenic peptide presentation and T cell recognition

Rheumatoid arthritis, an autoimmune disease, is significantly associated with the HLA class II allele HLA-DR4. While the etiology of rheumatoid arthritis remains unknown, type II collagen (CII) is a candidate autoantigen. An immunodominant pathogenic epitope from this autoantigen, CII(261-273), which binds to HLA-DR4 and activates CD4+ T cells, has been identified. The non-classical class II antigen, HLA-DM, is also a key component of class II antigen presentation pathways influencing peptide presentation by HLA-DR molecules expressed on professional antigen-presenting cells (APC). Here, we investigated whether the HLA-DR4-restricted presentation of the pathogenic CII(261-273) epitope was regulated by HLA-DM expression in APC. We show that APC lacking HLA-DM efficiently display the CII(261-273) peptide/epitope to activate CD4+ T cells, and that presentation of this peptide is modulated dependent on the level of HLA-DM expression in APC. Mechanistic studies demonstrated that the CII(261-273) peptide is internalized by APC and edited by HLA-DM molecules in the recycling pathway, inhibiting peptide presentation and T cell recognition. These findings suggest that HLA-DM expression in APC controls class II-mediated CII(261-273) peptide/epitope presentation and regulates CD4+ T cell responses to this self epitope, thus potentially influencing CII-dependent autoimmunity.

Safety issues in the management of autoimmune hepatitis

BACKGROUND

Prednisone and azathioprine are effective in the treatment of autoimmune hepatitis, but diverse side effects can diminish their net benefit.

OBJECTIVES

Describe the frequency and nature of these side effects and propose management strategies to minimize their impact.

METHODS

Pertinent articles published from 1970 to 2007 were identified by Medline search and through a personal library.

RESULTS

Medication is prematurely discontinued in 13% of patients mainly because of cosmetic changes, cytopenia, or osteopenia. Populations at high risk are the elderly, those with pre-existent co-morbidities, patients with near-zero thiopurine methyltransferase activity, individuals who are treatment-dependent, pregnant women, and asymptomatic patients who are over-treated.

CONCLUSIONS

Proper patient selection, effective pre-treatment counseling, preemptive protective measures, realistic treatment objectives, and early identification of problematic patients can reduce complications. Individualized dosing schedules and the emergence of non-steroidal medications are realistic expectations.

Current therapy for autoimmune hepatitis

The treatment of autoimmune hepatitis is evolving as the pathogenic pathways that underlie the disease are defined, new immunosuppressive agents are tested, and site-specific molecular interventions become feasible. Prednisone alone or at a reduced dose combined with azathioprine is the conventional treatment. Patients with HLA genotype DRB1*0301 have a poorer treatment response and a more frequent need for liver transplantation than those with HLA genotype DRB1*0401. Therapy to the point when liver test results and histological findings are normal reduces, but does not eliminate, the occurrence of relapse. Treatment failure warrants reassessment with regard to the accuracy of the original diagnosis and the exclusion of variant forms of hepatitis or concomitant alternative diseases. Ciclosporin might be effective as short-term, front-line therapy in infants and adults, and calcineurin inhibitors might salvage patients who are refractory to corticosteroid regimens. Mycophenolate mofetil can induce an improvement in laboratory test results and reduce the requirement for corticosteroids. Sirolimus is effective for treatment of de novo autoimmune hepatitis that develops after liver transplantation. Synthetic peptides that block autoantigen presentation, cytokine manipulations, oral tolerance regimens, T-cell vaccination, and gene therapy are all interventions that will be able to emerge after a reliable animal model of the human disease has been developed.

Altered peptide ligands control type II collagen-reactive T cells from rheumatoid arthritis patients

We previously reported that peripheral blood mononuclear cells from HLA-DRB1*0101 Japanese patients with rheumatoid arthritis (RA) were highly reactive to 256-271 peptide of type II collagen (CII). In this report, we tried to regulate the CII reactivity of T cells from RA patients with HLA-DRB1*0101 by altered peptide ligand (APL), which is a single amino acid substitution of the T-cell epitope on CII 256-271 peptide. Antagonistic activity of 21 APLs was assessed using three different T-cell lines. Results showed that 262 (G-->A) APL of CII 256-271 exhibited antagonistic activity in all T-cell lines and it was suggested that the application of CII APL might be a new therapeutic strategy in the regulation of RA.

Inhibition of T-cell activation with HLA-DR1/DR4 restricted Non-T-cell stimulating peptides

It has been reported that collagen II (CII) derived peptide CII263-272 induced T-cell activation via its amino acids responsible for T-cell receptor (TCR) recognition. The impact of substitution of the TCR contacting amino acids of CII263-272 on T-cell activation was evaluated in this study using a panel of altered CII263-272 peptides. Computer modeling revealed that the side chains of 263F and 266E in CII263-272 were coupled with amino acids on alpha1 and beta1 chains of HLA-DR1 or -DR4, mainly via hydrogen bonds, whereas the side chains of 267Q and 270K protrude out of the cleft and might be recognized by TCR. Intracellular delivery of the altered peptides, and their binding to HLA-DR1 and -DR4 molecules on cell surface, were demonstrated by confocal microscopy and flow cytometry. The results also revealed that the substitution of 267Q, 268G, 269P, and 270K individually or consecutively by alanine (A) or glycine (G) led to weak or non-T-cell responses. Furthermore, the altered peptides with 270K substitution (270A) or with consecutive substitution of 268G, 269P, and 270K (sub268-270) dramatically inhibited T-cell activation. It is suggested that the altered peptides derived from CII263-272 with substitution of amino acids responsible for TCR contact might be of inhibitory effect on T-cell responses.

Synthetic peptides that inhibit binding of the myelin basic protein 85-99 epitope to multiple sclerosis-associated HLA-DR2 molecules and MBP-specific T-cell responses

Copolymer 1 (Cop 1, poly [Y, E, A, K]) is a random synthetic amino acid copolymer effective in the treatment of relapsing forms of multiple sclerosis (MS), a disease that is linked to HLA-DR2 (DRB1*1501). In the present study various peptides, synthesized according to the binding motifs for both the immunodominant epitope of myelin basic protein (MBP) 85-99, a candidate autoantigen in MS, and Cop 1, differentially inhibited binding of these antigens to disease-associated HLA-DR2 (DRB1*1501) molecules. In particular, two peptides with residue K at position P-1, as referred to MBP 85-99, inhibited effectively the binding of both biotinylated MBP 85-99 and Cop 1 to HLA-DR2 molecules as well as IL-2 production by two MBP-specific HLA-DR2-restricted T-cell clones. These findings suggest the possible utility of these compounds or their more stable derivatives in treatment of MS.