Heterogeneity of T-cell receptor alpha-chain complementarity-determining region 3 in myelin basic protein-specific T cells increases with severity of multiple sclerosis

Analysis of TCR antagonism and molecular mimicry of an HLA-A0201-restricted CTL epitope in primary biliary cirrhosis

Although the etiology and mechanism of primary biliary cirrhosis (PBC) is unknown, growing evidence suggests a major role for T cells. We have recently identified the first CD8 T-cell epitope, amino acid 159-167 of the E2 component of pyruvate dehydrogenase complexes (PDC-E2). To seek for analogue peptide-antagonizing effector function of CTLs specific for this autoantigen, we examined the effector functions of the PDC-E2-specific CTLs against alanine substituted peptides. Furthermore, because molecular mimicry has been postulated as a possible cause of initiating PBC, we carried out studies aimed at identifying naturally occurring peptides for the 159-167 peptide of PDC-E2 that may serve as agonists. An alanine substitution at position 5 of this epitope significantly reduced peptide-specific effector functions of CTLs. Moreover, this analogue peptide inhibited effector functions of the CTLs to the prototype peptide, including cytotoxicity and IFN-gamma production. We also identified a peptide derived from Pseudomonas aeruginosa, which showed a higher binding affinity to the HLA-A*0201 than the prototype peptide. This homologous peptide was recognized by CTLs specific for the prototype epitope on PDC-E2. In conclusion, a modification of the immunodominant autoepitope can be utilized to manipulate the CD8 T-cell responses against the autoantigen PDC-E2. Our finding also supports the thesis that molecular mimicry may be implicated in the initiation of the autoreactive CD8 T-cell responses and has implications for the use of such peptides for immunotherapy.

Selected cytotoxic T lymphocytes with high specificity for HTLV-I in cerebrospinal fluid from a HAM/TSP patient

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic inflammatory disease of the spinal cord in which HTLV-I Tax-specific cytotoxic T lymphocytes (CTL) have been suggested to be immunopathogenic. However, it is unknown whether the HTLV-I-specific CTL in the central nervous system differ from those in the periphery. We investigated functional T-cell receptor diversity in HTLV-I Tax11-19-specific CTL clones derived from peripheral blood and cerebrospinal fluid (CSF) of a HAM/TSP patient using analogue peptides of the viral antigen. CTL responses to the analogue peptides varied between T-cell clones, however, CTL clones from CSF showed limited recognition of the peptides when compared to those from peripheral blood. This suggests that CTL with highly focused specificity for HTLV-I Tax accumulate in the CSF and may contribute to the pathogenesis of HAM/TSP. Furthermore, this study provides a rationale for analogue peptide-based immunotherapeutic strategies focusing on the immunopathogenic T-cells in HTLV-I-associated neurologic disease.

Dominant lesional T cell receptor rearrangements persist in relapsing psoriasis but are absent from nonlesional skin: evidence for a stable antigen-specific pathogenic T cell response in psoriasis vulgaris

In a previous study we reported that clonally expanded T cell receptor beta-chain rearrangements characterized the T cell receptor usage in skin lesions of psoriasis vulgaris and indicated antigen-specific T cell selection. To assess the relevance of clonal T cell expansion for disease progression, we now determined if select clonal T cell receptor rearrangements persisted over time and were present in nonlesional skin. Sequential biopsies were taken from psoriatic skin lesions of two patients. V-D-J junctional regions of T cell receptor beta-chain variable region gene families 2, 3, 6, 13S1, and BV17 were cloned and sequenced, as these particular BV gene families are preferentially selected in psoriatic skin lesions. The lesional T cell receptor rearrangements were compared with the T cell receptor usage in nonlesional skin and in blood. Several T cell receptor beta-chain rearrangements with high transcript frequency in the first lesional biopsy were again found in sequential lesional biopsies taken as much as 3 y later from psoriasis relapses. Only T cell receptor beta-chain rearrangements with low transcript abundance showed variability in that several clones appeared for the first time or disappeared. Although nonlesional skin also exhibited a restricted T cell receptor usage with clonal T cell receptor rearrangements, the T cell receptor usage in lesional and nonlesional skin differed nearly completely. The select lesional recurrence of identical T cell receptor rearrangements reveals that inflammation in psoriasis involves the same clonally expanded T cell populations and the same antigens over prolonged periods of time. It hereby suggests that specifically recruited and locally expanded T cell clones are permanently involved in psoriatic inflammation and may play a crucial part in disease perpetuation.

An altered peptide ligand antagonizes antigen-specific T cells of patients with human T lymphotropic virus type I-associated neurological disease

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease associated with HTLV-I infection, in which chronically activated, HTLV-I-specific CD8+ CTL have been suggested to be immunopathogenic. In HLA-A2 HAM/TSP patients, CD8+ HTLV-I-specific CTLs recognize an immunodominant peptide of the HTLV-I Tax protein, Tax11-19. We examined the functional outcome on activation of both cloned peripheral blood and cerebrospinal spinal fluid-derived CTL and bulk PBMC from HAM/TSP patients by altered peptide ligands (APL) derived from HTLV-I Tax11-19. In CTL clones generated from PBMC and CSF of HLA-A2 HAM/TSP patients, an APL substituted at position 5 significantly decreased CTL responses when compared with the native peptide. Moreover, these ligands were also shown to inhibit CTL responses to the native peptide in bulk PBMC of HLA-A2 HAM/TSP patients. These data suggest that a modification of an antigenic peptide at the central position can manipulate the T cell responses in bulk PBMC from different individuals with an inflammatory disease. Additionally, these results have implications for the potential use of APL-based immunotherapy in this T cell-mediated CNS disease.

T-cell responses to myelin antigens in multiple sclerosis; relevance of the predominant autoimmune reactivity to myelin oligodendrocyte glycoprotein

Until recently, the search for the 'culprit' autoantigen towards which deleterious autoimmunity is directed in multiple sclerosis (MS) centered mostly on myelin basic protein (MBP) and proteolipid (PLP), the two most abundant protein components of central nervous system (CNS) myelin, the target tissue for the autoimmune attack in MS. Although such research has yielded important data, furthering our understanding of the disease and opening avenues for possible immune-specific therapeutic approaches, attempts to unequivocally associate MS with MBP or PLP as primary target antigens in the disease have not been successful. This has led in recent years to a new perspective in MS research, whereby different CNS antigens are being investigated for their possible role in the initiation or progression of MS. Interesting studies in laboratory animals show that T-cells directed against certain non-myelin-specific CNS antigens are able to cause inflammation of the CNS, albeit without expression of clinical disease. However, reactivity to these antigens by MS T-cells has not been demonstrated. Conversely, reactivity by MS T-cells to non-myelin-specific antigens such as heat shock proteins, could be observed, but the pathogenic potential of such reactivity has not been corroborated with the encephalitogenicity of the antigen. More relevant to MS pathogenesis may be, as we outlined in this review, the autoimmune reactivity directed against minor myelin proteins, in particular the CNS-specific myelin oligodendrocyte glycoprotein (MOG). Here, we review the current knowledge gathered on T-cell reactivity to possible target antigens in MS in the context of their encephalitogenic potential, and underline the facets which make MOG a highly relevant contender as primary target antigen in MS, albeit not necessarily the only one.

Myelin reactive T cells in the autoimmune pathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) leading to demyelination. Although it is widely accepted that demyelination in MS results from an active inflammatory process, the cause of the inflammation is still not completely resolved. Findings in experimental autoimmune encephalomyelitis (EAE), an animal model of MS, and observations in human MS have led to the hypothesis that MS is an autoimmune disease mediated by autoreactive T cells with specificity for myelin antigens. The identity of the brain antigen(s) which is (are) the primary target(s) of the autoimmune process is not known, but current evidence indicates that myelin basic protein (MBP) is a likely candidate. In this paper we will overview some of the experimental evidence suggesting that MBP reactive T cells hold a central position in the pathogenesis of MS, and discuss some of the currently tested therapeutic strategies in MS which are directed towards the pathogenic MBP reactive T cells. Although there appears to be no direct correlation between anti-MBP T cell responses and clinical disease activity, some recent observations suggest that monitoring of anti-MBP T cell responses could be helpful to study immunological efficacy of experimental immunotherapies in MS.

A restricted T cell response to myelin basic protein (MBP) is stable in multiple sclerosis (MS) patients

The close resemblance of MS to the animal model experimental autoimmune encephalomyelitis (EAE) has provided compelling data sustaining a pathogenic role of circulating T cells reactive against MBP. T cell antigen receptor (TCR) usage in EAE is commonly considered restricted; nevertheless, dynamic changes of TCR usage correlate with the course of EAE, resulting in a limited repertoire during early stages of disease activity followed by the recruitment of other T cells reactive against new determinants. Although a broader TCR repertoire mediates the response to MBP in humans, a restricted intraindividual heterogeneity may occur in some MS patients. In the present study we characterize the response to MBP in MS subjects with relapsing remitting disease from two sampling time points 12 months apart. MBP-specific T cell lines (TCL) were first generated from eight MS individuals and two healthy subjects. New TCL were obtained after 12 months from one control and three MS patients whose response, at the first time point, was directed against a single epitope. Interestingly, these three subjects had a stable and mild disease. Few TCL obtained at two time points from the MS individuals recognized the same immunodominant epitope and shared identical TCR Vbeta sequences. In the control we could not detect a restriction of the repertoire. These findings suggest that in some MS patients with benign disease a predominant T cell response to a single determinant may be detectable at different moments and is mediated by clonally expanded populations.

Identification of multiple sclerosis-associated genes

Multiple sclerosis (MS) is a complex genetic trait. Analyses to identify genetic variants that increase susceptibility to MS have primarily focused on candidate genes, either in family linkage investigations or in association (linkage disequilibrium) studies in sporadic cases and control subjects. Most of the candidate genes considered to date either influence immune function or encode structural myelin proteins. Recently, three preliminary whole genomic surveys were completed, and they reveal multiple loci of possible genetic linkage that are worthy of further study. No convincing evidence for a single strong locus has emerged from analysis of the three studies. Linkage promises to focus the future choice of candidate genes for further investigation.

Therapeutic potential of phosphodiesterase type 4 inhibition in chronic autoimmune demyelinating disease

It was recently demonstrated that selective phosphodiesterase type 4 (PDE4) inhibition suppresses the clinical manifestations of acute experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), and inhibits the production of tumor necrosis factor-alpha (TNF-alpha), a pathogenetically central cytokine. Since the most common presentation of MS in humans is a relapsing-remitting course, we investigated the therapeutic potential of PDE4 inhibition in the relapsing-remitting EAE model of the SJL mouse. Administration of rolipram, the prototypic PDE4 inhibitor, reduced the clinical signs of EAE during both the initial episode of disease and subsequent relapses. In parallel, there was marked reduction of demyelination and also less inflammation throughout the central nervous system (CNS) of rolipram-treated animals. Gene expression of proinflammatory cytokines in the CNS was reduced in most of the rolipram-treated animals. Additional experiments demonstrated that PDE4 inhibition acted principally by inhibiting the secretion of Th1 cytokines, however, the encephalitogenic potential of myelin basic protein-specific T cells was not impaired. Our findings suggest that PDE4 inhibitors are a promising cytokine-directed therapy in chronic demyelinating disease.

Longitudinal study of myelin basic protein-specific T-cell receptors during the course of multiple sclerosis

This study analyzed the stability of the myelin basic protein (MBP)-specific T-cell receptor (TCR) repertoire during the course of multiple sclerosis (MS) in three patients who were monitored for three years by gadolinium-enhanced magnetic resonance imaging. Bulk-culture T-cell lines (TCLs) were generated from 3-4 time points for each patient, including times of active and quiescent disease. TCR analysis of these TCLs indicated that both the V alpha and V beta usage was similar over time for each patient. Sequencing of TCRs demonstrated conserved complementarity-determining region 3 (CDR3) sequences within TCLs that expressed the same V alpha segment over time, although the J alpha usage was different for each TCR. This indicates that the population of MBP-reactive T-cells is changing during the course of MS, but that host and/or environmental factors may be selecting T-cells with particular MHC/peptide binding domains.

Acquired resistance to experimental autoimmune encephalomyelitis is independent of V beta usage

In Lewis rats, activated encephalitogenic T-helper cells elicit a single bout of experimental autoimmune encephalomyelitis (EAE). Recovery from EAE is marked by reduced susceptibility to disease reinduction. The purpose of this study was to determine whether a dominant expression of V beta gene segments by encephalitogenic T cells was required for development of recovery-associated resistance. Several polyclonal and monoclonal T cell lines were derived from Lewis rats sensitized with R72-86, a synthetic peptide representing the 72- to 86-amino-acid sequence of rat myelin basic protein (RMBP). The results revealed broad heterogeneity among encephalitogenic T cells specific for R72-86 in regard to V beta expression and CDR3 sequence. Encephalitogenic clones exclusively bearing either V beta 4 or V beta 10 TCR or polyclonal T cells bearing heterogeneous TCR transferred EAE to recipient rats and elicited resistance to EAE as revealed by subsequent challenge with guinea pig (GP)MBP in complete Freund's adjuvant (CFA). Nonpathogenic V beta 3+ and V beta 8.6+ clones specific for the 68-86 and 55-66 regions of MBP, respectively, did not elicit effective protection from EAE. These data indicate that induction of postrecovery resistance to EAE does not depend upon a particular V beta usage.

2',3'-cyclic nucleotide 3'-phosphodiesterase: a novel candidate autoantigen in demyelinating diseases

Autoaggressive T-cells specific for myelin proteins like proteolipid protein (PLP) and myelin basic protein (MBP) are thought to play a major role in the pathogenesis of demyelinating diseases of the central nervous system (CNS). 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) is the third most abundant myelin protein in the CNS. Due to lack of supply with enough CNPase of sufficient purity its immunologic properties have not been studied yet. We subcloned a human CNPase cDNA and expressed human recombinant CNPase (rh-CNPase) in E. coli. Purification of the protein was achieved by Ni(2+)-chelating chromatography. Furthermore we describe for the first time several rh-CNPase specific T-cell lines from a multiple sclerosis patient and a healthy control.

Analysis of T-cell receptor Vbeta repertoire in liver-infiltrating lymphocytes in chronic hepatitis C

BACKGROUND/AIMS

To examine the T-cell repertoire which is involved in the immunopathogenesis of chronic hepatitis, we analyzed the T-cell receptor Vbeta gene usage in liver-infiltrating lymphocytes by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical technique.

METHODS

Complementary DNA was synthesized from RNA which was extracted from 26 liver biopsy specimens and from peripheral blood lymphocytes from eight subjects, and amplified by RT-PCR. Radioactivity of each amplified product using 32P-labeled primers was measured and the percentage of each Vbeta expression was calculated.

RESULTS

The mean frequency of Vbeta5.1 (11.1%) in liver-infiltrating lymphocytes of chronic hepatitis C was highest among those of all Vbeta regions, and was significantly higher than that in both peripheral blood lymphocytes of chronic hepatitis C and liver-infiltrating lymphocytes of chronic hepatitis B. In the immunohistochemical analysis, Vbeta5.1-positive cells were mostly observed in portal areas where inflammatory reactions occurred. The sequences of the complementarity determining region (CDR)3 on T-cell receptor expressing Vbeta5.1 were examined in six patients with chronic hepatitis C. The sequences were similar to each other and all had one common amino acid (valine) irrespective of different HLA haplotype.

CONCLUSIONS

These data suggest that Vbeta5.1-positive cells are preferentially accumulated in the liver of chronic hepatitis C and are involved in the immunopathogenesis of the disease. Sequence analysis showed that Vbeta5.1-positive cells recognize a common conventional antigen and valine recognized at the same position of the CDR3 may be a key residue in determining an antigen/major histocompatibility complex contact point.

Immunological aspects of experimental allergic encephalomyelitis and multiple sclerosis and their application for new therapeutic strategies

The etiology of multiple sclerosis (MS), a demyelinating disorder of the central nervous system (CNS), is not yet known. Immunological, clinical and pathological studies suggest, however, that T lymphocytes directed against myelin antigens are involved in the pathogenesis of MS. The examination of an experimental animal model for MS, experimental allergic encephalomyelitis (EAE), demonstrated that myelin basic protein-(MBP) or proteolipidprotein-(PLP) specific T cells mediate the destruction of CNS myelin. In recent years, elegant studies in EAE showed that encephalitogenic T cells recognize short peptides of MBP or PLP in the context of MHC/HLA-class II molecules, express a restricted number of T cell receptor (TCR) molecules and secrete interferon-gamma and tumor necrosis factor-alpha/beta. Understanding the pathogenetic steps of demyelination at the molecular level led to highly specific immunotherapies of EAE targeting each individual molecule. MBP- and PLP-specific T cells with similar properties could also be isolated from MS patients and control individuals. Due to their heterogeneity in terms of specificity, function and TCR usage, it was difficult, however, to draw definite conclusions from these results, so far. The recent approval of interferon-beta, a cytokine that antagonizes a number of the effects of interferon-gamma, for the treatment of MS has raised great interest in examining novel strategies for immunotherapies in MS. The basic concepts as well as the current candidates for such new immunotherapies will be outlined in this brief article.

Restricted T cell receptor repertoire for acetylcholine receptor in murine myasthenia gravis

Immunization of C57BL/6 mice with AChR provokes symptoms similar to those seen in the disease myasthenia gravis. To elucidate the structural requirements for T cell recognition of AChR and to identify TcR features which might provide targets for immunotherapy, a panel of T cell hybridomas was generated after immunization of mice with the immunodominant peptide of the AChR alpha chain. The TcR genes expressed by these hybridomas were sequenced. TcR-V beta 6 was preferentially employed, but other V beta genes were also observed. A conserved acidic residue was present in all CDR3 regions, regardless of the V beta. The TcR-V alpha repertoire was somewhat skewed with three V alpha families accounting for 82% of the sequences. The utilization of multiple T cell receptor V beta genes may contribute to the inability to inhibit EAMG by elimination of V beta 6+ T cells.

Differential activation of human autoreactive T cell clones by altered peptide ligands derived from myelin basic protein peptide (87-99)

We have examined the functional consequences induced by interaction of DR2a-restricted myelin basic protein (MBP) (87-99)-specific T cell clones (TCC) with altered peptide ligands (APL) derived from MBP peptide (87-99). The immunodominant MBP peptide (87-99) has been implicated as a candidate antigen in multiple sclerosis (MS) by several lines of evidence. In the present study, we have defined the T cell receptor (TCR) contact residues for DR2a-restricted, (87-99)-specific T helper type 1 T cells to design APL suitable to modify the functions of such T cells potentially relevant for the pathogenesis of MS. We show that neutral (L-alanine substitutions) or conservative exchanges of the primary and secondary TCR contact residues lead to various alterations of T cell function, ranging from differences in interleukin-2 receptor up-regulation to anergy induction and TCR antagonism. The potential usefulness of APL as an immunomodulating therapy for DR2+ MS patients is discussed.

Experimental immunotherapies for multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease affecting the central nervous system (CNS) principally in young adults. Although its etiology is as yet unknown current evidence suggests that tissue damage is mediated by autoimmune T cells. The examination of an experimental animal model for MS, experimental allergic encephalomyelitis (EAE), has demonstrated that myelin basic protein (MBP)- or proteolipid protein (PLP)-specific T cells mediate the destruction of CNS myelin. In recent years, elegant studies in EAE have shown that encephalitogenic T cells recognize short peptides of MBP or PLP in the context of MHC/HLA-class II molecules, express a restricted number of T cell receptor (TCR) molecules and secrete interferon-gamma and tumor necrosis factor-alpha/beta. Understanding the pathogenetic steps in lesion development at the molecular level led to highly specific immunotherapies for EAE targeting each individual molecule. It has been the hope of many investigators that immunological events resembling those in EAE can be found in patients with MS and that the specific immunotherapies effective in EAE could also be applied to MS. However, to date, the evidence for a unique immunological abnormality in MS is not strong. Although MBP- and PLP-specific T cells with properties similar to those that are encephalitogenic in animals can be isolated from patients, they are not specific for MS and occur with similar frequency in controls. In addition, the variability in specificity and TCR usage has raised questions regarding the relevance of these cells in patients. The importance of the T cell responses to myelin antigens in MS may not be established until the effects of abrogating their activity through specific therapies targeting the trimolecular complex (TMC) have been demonstrated. Consequently, attention has begun to focus on modifying the biology of the MS lesion rather than targeting the initiating event at the level of the TMC, and the success of this approach is reflected by the effect of interferon-beta on lesion development in MS. The recent approval for the use of interferon-beta for the treatment of relapsing-remitting MS has raised great interest in examining novel strategies for immunotherapies in MS. The basic concepts as well as the current candidates for such new immunotherapies will be outlined in this short review.

Mechanisms of the pathogenic autoimmune response in lupus: prospects for specific immunotherapy

A major step towards understanding the basic mechanism of systemic lupus erythematosus (SLE), the prototypic autoimmune disease that develops spontaneously, has been the identification of nucleosomes as a primary immunogen in this disease. The production of pathogenic autoantibodies in SLE results from an MHC class-II-restricted, cognate interaction between select populations of T helper cells and B cells that are specific for nucleosomal components. These observations pave the way for specific immunotherapy that blocks this pathogenic T and B cell interaction.

Structure and specificity of T cell receptors expressed by potentially pathogenic anti-DNA autoantibody-inducing T cells in human lupus

The production of potentially pathogenic anti-DNA autoantibodies in SLE is driven by special, autoimmune T helper (Th) cells. Herein, we sequenced the T cell receptor (TCR) alpha and beta chain genes expressed by 42 autoimmune Th lines from lupus patients that were mostly CD4+ and represented the strongest inducers of such autoantibodies. These autoimmune TCRs displayed a recurrent motif of highly charged residues in their CDR3 loops that were contributed by N-nucleotide additions and also positioned there by the recombination process. Furthermore, Th lines from four of the five patients showed a marked increase in the usage of the V alpha 8 gene family. Several independent Th lines expressed identical TCR alpha and/or beta chain sequences indicating again antigenic selection. 10 of these Th lines could be tested further for antigenic specificity. 4 of the 10 pathogenic anti-DNA autoantibody-inducing Th lines responded to the non-histone chromosomal protein HMG and two responded to nucleosomal histone proteins; all presented by HLA-DR molecules. Another Th line responded to purified DNA more than nucleosomes. Thus, these autoimmune Th cells of lupus patients respond to charged epitopes in various DNA-binding nucleoproteins that are probably processed and presented by the anti-DNA B cells they selectively help.

T-cell antigen receptors in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic disease of unknown etiology characterized by chronic inflammation mainly in the joints. Several lines of evidence suggest that T cells are involved in the pathogenesis of the disease. RA is associated with certain HLA-DR alleles. Studies analyzing T-cell receptor transcripts in RA have found biased or preferential usage of certain V alpha and/or V beta gene segments by T cells infiltrating the synovial membrane or extravasating into the synovial fluid compared to peripheral blood. In certain patients few T-cell antigen receptor (TCR) clones dominated the infiltrating T cells, suggesting that T cells from the synovial membrane or the synovial fluid comprise oligoclonal populations of T cells. However, other studies have found a polyclonal population of T cells. In interpreting these results the phase of the disease (early vs. late RA), the source of T cells and the limitations of the methods used in these studies should be taken into consideration. However, it appears that synovial T cells comprise oligoclonal populations of T cells and that there is a bias towards particular TCR gene segments, although a specific TCR gene segment in RA has not emerged.