The human T lymphotropic virus type I (HTLV-I) is the etiologic agent of a chronic progressive myelopathy known as HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP), a disease clinically similar to the chronic progressive form of multiple sclerosis (MS). While many viruses have been associated with MS, particular attention has recently focused on the human herpes virus type 6 (HHV-6). An understanding of the pathogenesis of a neurologic disease with a known viral etiology (HTLV-I and HAM/TSP) will aid in defining similar mechanisms of pathogenesis in MS, a disease of unknown etiology in which viruses have been suspected to play a role. Areas of research addressing these neurovirological and neuroimmunological issues include: I) The host immune response to viruses from patients with HAM/TSP and MS with particular focus on virus-specific CD8+; II) The role of HHV-6 in the pathogenesis of MS and other chronic neurological disorders of the central nervous system; III) Immunotherapeutic strategies for the treatment of HAM/TSP. The major findings of these studies are: 1) Increased HTLV-I specific CD8+ cells have been shown to be elevated in the peripheral blood and CSF of HAM/TSP patients and directly proportional to the amount of HTLV-I proviral DNA and RNA. These antigen-specific T cells are considered to be immunopathogenic and may be directly involved in virus-host interactions in the CNS. A more complete understanding of the maturation and activation of these cells will better aid in the development of therapeutic strategies that target this population of effectors. 2) The immunology of HAM/TSP, in particular the persistent expansion of these antigen-specific memory CD8+ T cells, offers unique opportunities to study antigen-specific immune response in humans. Recently, dysregulation of the newly described cytokine, interleukin-15 (IL-15), has been implicated in the pathogenesis of a number of immune mediated diseases including HAM/TSP. Collaborative research by the Viral Immunology Section, NINDS and the Metabolism Branch, NCI suggests that up-regulation of IL-15 may sustain the persistent expansion of virus-specific CD8+ T cells in HAM/TSP. The recent development of a monoclonal antibody that blocks the action of IL-15, Hu MiK-beta-1, offers the unique opportunity to study the maintenance and dysregulation of long-term immunologic memory in a human immune mediated disease. We have approval for the application of Hu MiK-beta-1 as a proof-of-principle clinical trial in patients with HAM/TSP. We will assess the effects of intravenously administered Hu-MiK-?-1 on the cellular immune response in patients with HAM/TSP, with particular focus on virus-specific memory CD8+ T cells. Secondary outcomes to be measured will be clinical responses, including toxicity. As IL-15 over expression has been demonstrated in patients in a wide variety of autoimmune disorders including, rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis and psoriasis, the successful application of Hu MiK-beta-1 in HAM/TSP has significant and broad therapeutic implications. 3) Prevention of HTLV-I entry and spreading is also under investigation as a therapeutic approach in patients with HAM/TSP. Therefore, we wish to understand the distribution and function of HTLV-I surface glycoprotein (SU) binding protein(s) including the recently identified cellular receptor for this virus, glucose transporter type 1 (GluR1). We have demonstrated that over-expression of GluR1 facilities HTLV-I binding and infection and are defining regions of HTLV-I that bind this receptor. Novel photolabelling strategies are being developed that target GluR1 with the expectation to quantify the levels of receptor in HTLV-I infected individuals with and without disease. 4) CD4+CD25+ regulatory T cells are important in the maintenance of immunological self-tolerance and in the prevention of autoimmune diseases. We have demonstrated that in HTLV-I infected CD4+CD25+ T cells of patients with HAM/TSP the expression of the forkhead transcription factor Foxp3, a specific marker of regulatory T cells, was lower than that of healthy individuals. HTLV-I tax had a direct inhibitory effect for the Foxp3 expression and inhibited the regulatory function of. This is the first report demonstrating the role of a specific viral gene product (HTLV-I tax) on the expression of molecules associated with T regulatory cells (FoxP3) resulting in inhibition of regulatory T cell function. These results suggest that direct human retroviral infection of CD4+CD25+ T cells may be associated with the pathogenesis of HTLV-I associated neurologic disease through the dysregulation of CD4+CD25+ regulatory T cells. 5) We have defined phenotypic protein changes within HTLV-1-infected sera. We will test our working hypothesis that discrete phenotypic protein profiles, reflective of disease state, will characterize infection with HTLV-I. These protein ?fingerprint? changes can be used for diagnostics, prognostics and early detection of disease. Our approach to generating disease specific protein profiles utilizes a Surface Enhanced Laser Desorption Ionization Time-Of-Flight Mass Spectroscopy (SELDI) centered process. We have developed methodology for protein expression profiling of human sera and will use this approach to establish a protein expression profiles. The development of the diagnostic profiling for virus associated disoders will also result in the mass identities of key disease-specific biomarker proteins known to be present in the blood. The identification of these proteins will allow for future development of immunoassays as well as insight into disease development. These studies will provide a tool for diagnosis/prediction of virus associted neurologic and hematologic disease and will provide the groundwork for similar approaches in other chronic, demyleinating disorders such as MS. 6) We continue to extend our work from brain resections of patients with mesial temporal lobe epilepsy that demonstrate HHV-6 in affected CNS tissue. We postulate that virus infection of astrocytes may be associated with a dysregulation of glutamate. We have successfully infected human progenitor derived astrocytes and primary human glial cells with HHV-6 and can show an increase in glutamate uptake in cells infected with the HHV-6A strain. By contrast, the HHV-6B strain appears to be associated with a more persistent type of infection associated with a decrease in glutamate uptake. Collectively, these results continue to define the role of human viruses that are associated with chronic progressive neurologic disease. 7) We have developed a novel virus chip containing the complete open reading frames of 8 divergent viruses. We have defined the specificity and sensitivity of this chip and successfully used this new methodology to detect the expression of viral gene products from the CNS of a patient who died from encephalitis of unknown cause. In addition, we have shown the utility of this virus chip to temporally map the virus gene expression profile of HHV-6 in vitro. The goal of these studies is to explore the possibility of using such technology to search for virus related sequences in biological material from patients with chronic progressive neurologic disease in which viruses have been suggested to play a role.
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