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Roland Martin

Publications and source records attributed to Roland Martin.

At least 55 records · Page 3Linked to original sources
PubMed2004

Kinematic specificity of cortical reorganization associated with motor training.

Motor training consisting of repetition of directionally specific voluntary thumb movements elicits a short-term memory trace that encodes the kinematic details of the practiced motions in the primary motor cortex. Here, we studied activation patterns associated with this form of training using functional magnetic resonance imaging under careful monitoring of motor training kinematics and electromyography. We identified task-specific reductions in activation in contralateral motor cortex, a region that controls executive motor output, as well as somatosensory cortex and inferior parietal lobule, regions in charge of monitoring motor training kinematics. Our findings are consistent with the hypothesis that a short training period consisting of repetition of finger motions leads to cortical reorganization characterized by a smaller and more efficient network that is specific for the trained movement direction.

Adult↗
PubMed2004

Research opportunities on human neuroborreliosis.

A workshop, sponsored by the National Institutes of Health, was convened in September 2001 to evaluate the current knowledge in neurological Lyme disease. The meeting was centered into discussion of both clinical and basic aspects of the disease. Participants included researchers from the fields of infectious diseases, neurology, rheumatology, autoimmunity and basic immunology, largely but not exclusively focused on Lyme disease. This report summarizes the presentations made at the meeting.

Animals↗
PubMed2004

Re: GAMES issue.

Explore the source record for details and available documents.

Data Collection↗
PubMed2003

Application of support vector machines for T-cell epitopes prediction.

MOTIVATION: The T-cell receptor, a major histocompatibility complex (MHC) molecule, and a bound antigenic peptide, play major roles in the process of antigen-specific T-cell activation. T-cell recognition was long considered exquisitely specific. Recent data also indicate that it is highly flexible, and one receptor may recognize thousands of different peptides. Deciphering the patterns of peptides that elicit a MHC restricted T-cell response is critical for vaccine development. RESULTS: For the first time we develop a support vector machine (SVM) for T-cell epitope prediction with an MHC type I restricted T-cell clone. Using cross-validation, we demonstrate that SVMs can be trained on relatively small data sets to provide prediction more accurate than those based on previously published methods or on MHC binding. SUPPLEMENTARY INFORMATION: Data for 203 synthesized peptides is available at http://linus.nci.nih.gov/Data/LAU203_Peptide.pdf

Algorithms↗
PubMed2003

Protein microarrays guide tolerizing DNA vaccine treatment of autoimmune encephalomyelitis.

The diversity of autoimmune responses poses a formidable challenge to the development of antigen-specific tolerizing therapy. We developed 'myelin proteome' microarrays to profile the evolution of autoantibody responses in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS). Increased diversity of autoantibody responses in acute EAE predicted a more severe clinical course. Chronic EAE was associated with previously undescribed extensive intra- and intermolecular epitope spreading of autoreactive B-cell responses. Array analysis of autoantigens targeted in acute EAE was used to guide the choice of autoantigen cDNAs to be incorporated into expression plasmids so as to generate tolerizing vaccines. Tolerizing DNA vaccines encoding a greater number of array-determined myelin targets proved superior in treating established EAE and reduced epitope spreading of autoreactive B-cell responses. Proteomic monitoring of autoantibody responses provides a useful approach to monitor autoimmune disease and to develop and tailor disease- and patient-specific tolerizing DNA vaccines.

Animals↗
PubMed2003

Gene expression profile in multiple sclerosis patients and healthy controls: identifying pathways relevant to disease.

Multiple sclerosis (MS) and other T cell-mediated autoimmune diseases develop in individuals carrying a complex susceptibility trait, probably following exposure to various environmental triggers. Owing to the presumed weak influence of single genes on disease predisposition and the recognized genetic heterogeneity of autoimmune disorders in humans, candidate gene searches in MS have been difficult. In an attempt to identify molecular markers indicative of disease status rather than susceptibility genes for MS, we show that gene expression profiling of peripheral blood mononuclear cells by cDNA microarrays can distinguish MS patients from healthy controls. Our findings support the concept that the activation of autoreactive T cells is of primary importance for this complex organ-specific disorder and prompt further investigations on gene expression in peripheral blood cells aimed at characterizing disease phenotypes.

Adult↗
PubMed2003

TCR ligand discrimination is enforced by competing ERK positive and SHP-1 negative feedback pathways.

Functional discrimination between structurally similar self and foreign antigens is a main attribute of adaptive immunity. Here we describe two feedback mechanisms in T lymphocytes that together sharpen and amplify initial signaling differences related to the quality of T cell receptor (TCR) engagement. Weakly binding ligands predominantly trigger a negative feedback loop leading to rapid recruitment of the tyrosine phosphatase SHP-1, followed by receptor desensitization through inactivation of Lck kinase. In contrast, strongly binding ligands efficiently activate a positive feedback circuit involving Lck modification by ERK, preventing SHP-1 recruitment and allowing the long-lasting signaling necessary for gene activation. The characteristics of these pathways suggest that they constitute an important part of the mechanism allowing T cells to discriminate between self and foreign ligands.

Animals↗
PubMed2003

Interleukin 4 treatment of psoriasis: are pleiotropic cytokines suitable therapies for autoimmune diseases?

Many human autoimmune diseases are still treated by a combination of corticosteroids and general immunosuppression. A better understanding of the pathogenesis of these diseases has led to therapies that are more specific than current therapies of some of these disorders. In psoriasis, T helper (Th) cells with a pro-inflammatory phenotype (Th1) are considered essential to the disease process. A recent clinical trial of interleukin 4 in psoriasis has demonstrated that such pleiotropic cytokines can be used safely and effectively to correct imbalances in immune function.

Adjuvants, Immunologic↗
PubMed2003

Glatiramer acetate-reactive peripheral blood mononuclear cells respond to multiple myelin antigens with a Th2-biased phenotype.

One favored mechanism of action of glatiramer acetate (GA) in multiple sclerosis (MS) involves the induction of GA-reactive Th2 cells that are believed to enter the central nervous system and mediate bystander suppression in response to cross-reactive myelin antigens. To test this hypothesis, we examined the proliferative response and cytokine release from peripheral blood mononuclear cells (PBMCs) of 12 MS patients treated with GA, in response to 16 myelin peptides that were previously described as immunodominant or encephalitogenic and a tetanus peptide as a control antigen. Interferon-gamma (IFN-gamma) and IL-5 (markers of Th1 and Th2 responses, respectively) were assayed by enzyme-linked immunosorbent assay (ELISA). GA-stimulated PBMCs from 9 of 12 patients (75%) proliferated to one or more myelin peptides. Among the 16 peptides tested, GA-stimulated PBMCs from the majority of the patients proliferated in response to MOG(21-44). PBMCs from two thirds of the patients produced IL-5 in response to myelin peptides, while half of them produced IFN-gamma. Th1/Th0/Th2 cytokine phenotypes demonstrated that responses from 10 of 12 patients were either Th0- or Th2-biased. Responses from two patients were Th1-biased. Conversely, some myelin-specific T-cell lines (TCLs) responded to GA by proliferation (3 of 21 TCLs), IL-5 release (11 of 21 TCLs), and IFN-gamma release (3 of 21 TCLs). These results indicate that GA-reactive TCLs can respond to a spectrum of myelin peptides in a Th2-biased fashion, which is consistent with the concept of bystander suppression. Furthermore, some myelin-specific TCLs are able to recognize GA, with a tendency to produce more IL-5 than IFN-gamma, which would suggest a systemic modulatory effect of the drug.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2003

Use of combinatorial peptide libraries for T-cell epitope mapping.

T lymphocytes play important roles not only in infectious diseases and autoimmunity, but also in immune responses against tumors. For many of these disorders, the relevant target antigens are not known. Designing effective methods that allow the search for T-cell epitopes is therefore an important goal in the areas of infectious diseases, oncology, vaccine development, and numerous other biomedical specialties. So far, the strategies used to examine T-cell recognition have been based largely on mapping T-cell epitopes with overlapping peptides from known proteins or with entire proteins, e.g., from a specific virus, bacterium, or human tissue. These approaches are tedious and have a number of limitations. It is, for example, almost impossible to isolate T cells that infiltrate an organ or infectious site and identify their specificity unless one already has a concept as to which antigens may be relevant. During recent years, a number of laboratories have developed less biased approaches that employ either the selection of putative T-cell epitopes based on the prediction of binding to certain major histocompatibilty complex (MHC) molecules and peptide or protein libraries that have been generated in expression systems, e.g. phage, or rely on combinatorial peptide chemistry. The latter technique has been refined by a number of laboratories including ours. Bead-bound or, preferably, positional scanning synthetic and soluble combinatorial peptide libraries allow the identification of T-cell epitopes within complex mixtures of proteins even for T cells that have been expanded from an organ infiltrate with a polyclonal stimulus. The practical steps that are involved in the latter method are described in this article.

Amino Acid Sequence↗
PubMed2003

Future immunotherapies in multiple sclerosis.

Immunotherapy of multiple sclerosis (MS) will continue to benefit from an increasing understanding of this disease. This knowledge results in newly defined targets for novel therapies. In this article the development of future immunotherapies will be discussed by classifying the approaches into three main types: (1) antigen-specific therapies; (2) agents with a defined target in pathogenic steps of the MS lesion; and (3) therapies with broad immunomodulatory activity. Success in developing new immunotherapies depends on understanding the underlying complexity and heterogeneity of the disease. The current practice of employing a single therapy across a heterogeneous group of MS patients is in part a likely reason for their modest efficacy. The mechanism of action of a single agent may target the appropriate defect in one individual but not others. The therapy of MS in the future will most likely use a combination of agents that are directed at the underlying disease state and stage in the individual patient.

Adjuvants, Immunologic↗
PubMed2003

Molecular tracking of antigen-specific T cell clones in neurological immune-mediated disorders.

T cells recognizing self or microbial antigens may trigger or reactivate immune-mediated diseases. Monitoring the frequency of specific T cell clonotypes to assess a possible link with the course of disease has been a difficult task with currently available technology. Our goal was to track individual candidate pathogenic T cell clones, selected on the basis of previous extensive studies from patients with immune-mediated disorders of the CNS, including multiple sclerosis, HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) and chronic Lyme neuroborreliosis. We developed and applied a highly specific and sensitive technique to track single CD4(+) and CD8(+) T cell clones through the detection and quantification of T cell receptor (TCR) alpha or beta chain complementarity-determining region 3 transcripts by real-time reverse transcriptase (RT)-PCR. We examined the frequency of the candidate pathogenic T cell clones in the peripheral blood and CSF during the course of neurological disease. Using this approach, we detected variations of clonal frequencies that appeared to be related to clinical course, significant enrichment in the CSF, or both. By integrating clonotype tracking with direct visualization of antigen-specific staining, we showed that a single T cell clone contributed substantially to the overall recognition of the viral peptide/MHC complex in a patient with HAM/TSP. T cell clonotype tracking is a powerful new technology enabling further elucidation of the dynamics of expansion of autoreactive or pathogen-specific T cells that mediate pathological or protective immune responses in neurological disorders.

Adult↗
PubMed2003

Hematopoietic stem cell transplantation for multiple sclerosis: current status and future challenges.

PURPOSE OF REVIEW: This article reviews recent advances in clinical trials of hematopoietic stem cell transplantation as a therapy for multiple sclerosis, and progress in exploring the potential for neural repair of hematopoietic-derived precursors. RECENT FINDINGS: Important recent findings are that hematopoietic stem cell transplantation can completely suppress the inflammatory component of multiple sclerosis, hematopoietic stem cells can migrate into the central nervous systems of rodents and humans, and can differentiate into cells expressing neural and glial markers. Hematopoietic stem cells also have neural and myelin repair potential. The heterogeneity of transplant regimens, the selection of patients at different stages of disease in clinical trials, and the limited duration of follow-up all currently preclude the evaluation of the long-term clinical benefits of hematopoietic stem cell transplantation for multiple sclerosis. SUMMARY: Hematopoietic stem cell transplantation is an experimental treatment that shows strong effects on the inflammatory component of multiple sclerosis. On the basis of experience acquired from initial pilot studies, controlled clinical trials are now being designed to verify long-term clinical efficacy. Selecting patients at high risk in the earlier stages of the disease that is dominated by inflammation, and monitoring objectively disease activity by magnetic resonance imaging will be critically important in these studies. Recent advances on the migratory potential and on the differentiation plasticity of hematopoietic stem cells have opened new opportunities for remyelination and axonal repair strategies for multiple sclerosis.

Hematopoietic Stem Cell Transplantation↗
PubMed2002

Immunization with a cannabinoid receptor type 1 peptide results in experimental allergic meningocerebellitis in the Lewis rat: a model for cell-mediated autoimmune neuropathology.

Neuronal elements are increasingly suggested as primary targets of an autoimmune attack in certain neurological and neuropsychiatric diseases. Type 1 cannabinoid receptors (CB1) were selected as autoimmune targets because they are predominantly expressed on neuronal surfaces in brain and display strikingly high protein levels in striatum, hippocampus, and cerebellum. Female Lewis rats were immunized with N-terminally acetylated peptides (50 or 400 microg per rat) of the extracellular domains of the rat CB1 and killed at various time points. Subsequent evaluation using immunohistochemistry and in situ hybridization showed dense infiltration of immune cells exclusively within the cerebellum, peaking 12-16 days after immunization with the CB1 peptide containing amino acids 9-25. The infiltrates clustered in meninges and perivascular locations in molecular and granular cell layers and were also scattered throughout the CB1-rich neuropil. They consisted primarily of CD4(+) and ED1(+) cells, suggestive of cell-mediated autoimmune pathology. There were no inflammatory infiltrates elsewhere in the brain or spinal cord. The results show that neuronal elements, such as neuronal cell-surface receptors, may be recognized as antigenic targets in a cell-mediated autoimmune attack and, therefore, support the hypothesis of cell-mediated antineuronal autoimmune pathology in certain brain disorders.

Amino Acid Sequence↗
PubMed2002

Findings on T cell specificity revealed by synthetic combinatorial libraries.

Combinatorial libraries and in particular positional scanning synthetic combinatorial libraries (PS-SCL) allow the study of T cell specificity. This is a systematic and unbiased approach that does not require any previous knowledge about the clones to be studied, neither their specificity nor they major histocompatibility complex (MHC) restriction. Two different types of T cell clone ligands can be identified: (1) peptides that do not necessarily correspond to proteins described in the databases, and (2) peptides that are fragments of natural proteins. In this paper, relevant examples of the application of PS-SCL and the deconvolution strategies followed to identify T cell epitopes for clones of known and unknown specificity will be reviewed. Also, important issues like the immunogenicity of such T cell ligands will be discussed.

Animals↗
PubMed2002

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.

Epitopes↗
PubMed2002

T-cell epitope prediction with combinatorial peptide libraries.

T cell receptors (TCR) recognize antigenic peptides in complex with the major histocompatibility complex (MHC) molecules and this trimolecular interaction initiates antigen-specific signaling pathways in the responding T lymphocytes. For the study of autoimmune diseases and vaccine development, it is important to identify peptides (epitopes) that can stimulate a given TCR. The use of combinatorial peptide libraries has recently been introduced as a powerful tool for this purpose. A combinatorial library of n-mer peptides is a set of complex mixtures each characterized by one position fixed to be a specified amino acid and all other positions randomized. A given TCR can be fingerprinted by screening a variety of combinatorial libraries using a proliferation assay. Here, we present statistical models for elucidating the recognition profile of a TCR using combinatorial library proliferation assay data and known MHC binding data.

Combinatorial Chemistry Techniques↗