Th 17 Polarization and Trafficking in Multiple Sclerosis

Benjamin M. Segal, M.D.

University of Michigan

Funded in September, 2007: $200000 for 3 years
LAY SUMMARY . ABSTRACT . BIOGRAPHY .

LAY SUMMARY

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Developing Potential Biomarkers to Predict or Reveal Immune Attacks in Autoimmune Multiple Sclerosis

The investigators will use MRI imaging in multiple sclerosis (MS) patients to see whether they can correlate active periods of central nervous system (CNS) inflammation with specific immune inflammatory chemicals found in the patients’ bloodstream.

MS is an autoimmune inflammatory disease in which adaptive immune T cells produce chemicals that inflame and damage the CNS.  Prior studies of the animal model of MS called EAE (experimental allergic encephalomyelitis) suggest that a subset of immune T cells secrete a pro-inflammatory chemical called interleukin (IL-17) that may be involved in this inflammatory process.  The researchers plan to determine whether IL-17, or one of several other such chemicals, may produce the epidodes of CNS inflammation that characterize periods of active disease in MS patients.  They also plan to determine whether this is a circular process, in which acute the CNS inflammation is associated with the production of factors in the bloodstream that drive further development of the implicated immune T cells.  

They will test the first hypothesis by conducting laboratory studies of blood samples from MS patients and healthy volunteers. They will see whether any T cell subsets and the chemicals they produce (when stimulated) from MS patients, but not from healthy volunteers, infiltrate CNS tissue cultures and produce inflammation. The researchers suspect that IL-17 may be a causative chemical, and that the T cell subset that produces it has a distinctive array of molecules on the surface, enabling IL-17 to leave the circulating blood and enter into the CNS. They then will use MRI imaging of MS patients, in combination with patients’ blood samples, to test their second hypothesis and determine whether periods of active CNS inflammation correlate with increased blood levels of the implicated T cell subset, If so, the presence of high levels of these T cells in the blood could serve as a biomarker for CNS inflammation in MS.

Significance: The study could result in the development of the first biomarker of active inflammation  in the CNS of MS patients.  The biomarker could be used to monitor MS patients, and gauge their response to medications through this simple blood test.

ABSTRACT

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Th 17 Polarization and Trafficking in Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that is widely believed to be mediated by myelin-specific CD4+ T cells.  Th17 cells, a recently defined subset of CD4+ T cells that secrete the cytokine IL-17 upon antigenic activation, have been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), widely used as an animal  model of MS.  Upon commitment to the Th17 lineage, myelin-specific T cells acquire potent pathogenic properties and are readily recruited across the blood-brain-barrier following injection into naive syngeneic hosts.  Furthermore, IL-17 transcripts have been detected in MS lesions but not normal appearing white matter.

In Aim 1 of this proposal we will expand upon preliminary data demonstrating that myelin-specific Th17 cells express a distinctive panel of chemokine receptors (ie, CXCR4, CCR6 and CXCR5) and adhesion molecules (such as α4β7 integrin) that could potentially facilitate their homing to the CNS.  Specifically, we will polarize both murine and human myelin-specific T cells lines (the latter derived from patients with MS in addition to age and sex matched healthy controls) to either a Th17, Th1 or Th2 lineage and compare them among themselves, as well as to uncommitted memory cells, for expression of candidate homing molecules by real time RT-PCR and flow cytometric analyses.  Based on the results of these experiments, we will determine which cell surface molecules are critical for the infiltration of the CNS by murine Th17 cells in the context of the EAE model.  To do so, we will park CFSE-labeled myelin-specific Th17 cells into CD45.1 congenic, myelin-sensitized hosts and track their activation, expansion, and migration patterns in the presence or absence of antibodies that block selected chemokine or adhesion pathways. 

In Aim 2 we will test our hypothesis that progressive CNS damage in MS (as documented by magnetic resonance/ diffusion tensor imaging) is associated with a cytokine milieu that favors the differentiation and expansion of Th17 cells.  We have been monitoring chronic MS patients, off immunomodulatory medications, for evidence of acute inflammatory activity (by MRI with triple dose gadolinium) and for incremental tissue loss/ demyelination in the corpus callosum (via diffusion tensor imaging) on a bimonthly basis over the course of one year. We propose to measure levels of Th17 polarizing factors in peripheral blood mononuclear cells, collected from these same subjects over the same time frame, by real time RT-PCR and Elispot analyses. We predict that IL-6, TGF-β and IL-1α, which collectively act as a potent Th17 inducing stimulus, will be upregulated during, or immediately prior to, the formation of gadolinium enhancing lesions.  Furthermore, we predict that those patients who develop enhancing lesions and exhibit cytokine dysregulation will be more likely to experience ongoing tissue loss/damage throughout the observation period.

We are hopeful that the data generated by the proposed studies will help identify novel radiological and cellular surrogate markers that are predictive of, or coincident with, MS disease activity, and provide insights into novel therapies designed to inhibit the development and/or CNS homing of encephalitogenic Th17 cells in patients with MS.

INVESTIGATOR BIOGRAPHIES

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Benjamin M. Segal, M.D.

Benjamin M. Segal, M.D.,  is the Holtom-Garret Professor of Neurology and director of the Multiple Sclerosis Program at the University of Michigan in Ann Arbor.  He is a graduate of the Program in Medicine at Brown University, magna cum laude.  Dr. Segal did his intership in Internal Medicine at the University of Chicago and his residency in Neurology at Cornell University (the New York Hospital and Memorial Sloan Kettering Cancer Institute).  He was then a clinical associate in the Neuroimmunology Branch, NINDS, and postdoctoral fellow in the Laboratory of Immunology, NIAID, at the National Institutes of Health.  Prior to assuming his position in Ann Arbor, he was on faculty at the University of Rochester.  Dr. Segal is a former Harry Weaver Neurosciences Scholar of the National Multiple Sclerosis Society (NMSS).  He is currently a member of the scientific advisory board of the NMSS and director of a Collaborative MS Research Center awarded by the NMSS.  In 2006 he was elected to the Henry Kunkel Society, an honorary organization of  immunologists engaged in translational research. 

Dr. Segal’s laboratory studies interactions between the immune and nervous systems in the context of autoimmune demyelinating disease. He is interested in the influence of the CNS microenvironment on the development of local inflammatory responses and, conversely, the influence of immune mediators on neuronal and glial survival and regeneration/repair. One part of the laboratory is devoted to human immunological studies (involving the analysis of peripheral blood and cerebrospinal fluid mononuclear cells that are collected from patients with MS or other neurological diseases and from healthy controls). Currently, the lab is investigating the relationship between the expression of selected cytokines (such as IL-23 and IL-17) and CNS inflammatory disease activity, as detected by advanced MRI techniques, in individuals with progressive multiple sclerosis. A complementary division of the laboratory is dedicated to animal studies. Ongoing projects aim to elucidate the mechanisms by which leukocyte subsets, chemokines, and cytokines act together to induce demyelination and neuronal loss. Other studies address the effects of cytokines and chemokines on CNS progenitor cells and axonal regrowth pathways that could affect attempts to repair damaged CNS tissues.