William J. Karpus - US grants

Experimental autoimmune encephalomyelitis (EAE) is a relapsing- remitting demyelinating disease of the central nervous system (CNS) that serves as an animal model for multiple sclerosis (MS). Disease induction is accompanied by CNS histopathology characterized by mononuclear cell infiltrates, consisting of T cells, macrophages, and B cells. The CNS infiltration by macrophages, T cells, and B cells results in chronic relapsing remitting paralysis similar to what has been seen in a subset of MS patients. One o the major goals of this application is to address the role of chemokines and chemokine receptors in PLP-induced EAE, including determining the chemokines that are important in development of active and adoptive EAE, as well as during acute EAE, remission, and relapses of EAE. The relative role of specific chemokines in the CNS recruitment of antigen specific T cells as well as non-specific T cells and macrophages will be investigated. Furthermore, chemokines have been shown to have immune altering effects such as T cell co-stimulation, T cell cytokine expression, and T cell differentiation. Therefore, the role of chemokines in regulating the ongoing immune response in EAE will also be determined. We hypothesize that a temporal CNS expression pattern of selective chemokines and chemokine receptor regulates the immunopathogenesis of acute and relapsing EAE. This regulation includes effects on mononuclear cell chemoattraction as well as immunomodulation of cytokine responses. The following specific aims will be addressed to test our hypothesis: 1) Determination of chemokine regulation of acute and relapsing EAE induction and progression; 2) The role of CC chemokines in the immunomodulation of pro-inflammatory and anti-inflammatory cytokine responses during acute and relapsing EAE. These studies will help to understand the immunopathogenesis of MS and provide a basis for the development of novel chemokine and chemokine receptor therapies designed at targeting molecules involved in the migration of pathogenic lymphocytes into the CNS during the induction and progression of inflammatory demyelinating diseases.

DESCRIPTION (provided by applicant): Theiler's murine encephalomyelitis virus (TMEV) is an endemic murine pathogen that induces a demyelinating disease (TMEV-IDD) of the central nervous system (CNS) in susceptible mouse strains with accompanying CNS histopathology characterized by mononuclear cell infiltrates. TMEV-induced demyelinating disease is initiated by CD4+ T cell immune responses to viral proteins early in disease and self proteins in later disease. In susceptible strains of mice such as SJL, TMEV establishes a persistent infection in macrophages, induces a CNS infiltration of macrophages, T cells, and B cells, which results in chronic progressive paralysis. The chronic paralytic nature of the TMEV-induced clinical disease course as well as the CNS pathology presents as a very good model for the human CNS demyelinating disease, multiple sclerosis (MS). One of the major goals of this proposal is to define the cellular and molecular mechanisms that regulate the immunopathogenesis of this chronic inflammatory CNS demyelinating disease. Mononuclear cells infiltrate tissue sites during inflammatory processes and a family of chemotactic cytokines called chemokines have been implicated in this gradient-induced cell migration. The central hypothesis of this proposal is that chemokines are expressed in the CNS during TMEV-IDD and regulate immune responses including cell migration patterns that are required for demyelinating disease development and progression. This hypothesis will be tested by examining the following specific aims: 1) determination of the mechanisms of chemokine function in the initiation of TMEV-IDD 2) determination of the mechanisms of chemokine function in the progression of TMEV-IDD; and 3) determination of chemokine receptor expression and function in the development of TMEV-IDD. These studies will help to understand the immunopathogenesis of MS and provide a basis for the development of novel therapies designed at targeting molecules involved in the migration and accumulation of pathogenic lymphocytes and monocytes into the CNS during the induction and progression of inflammatory demyelinating diseases.

DESCRIPTION (provided by applicant): The importance of the Notch receptor system in central nervous system (CNS) demyelinating disease has been suggested by experiments where inhibition of ?-secretase and antibody blocking of Delta-Like Ligand (DLL) 1 down-regulated inflammatory T cell cytokine responses. However, we were the first to recently demonstrate that blockade of DLL4 function inhibited the development of clinical experimental autoimmune encephalomyelitis (EAE). Our data suggested that the role of DLL4 was to regulate encephalitogenic T cell chemokine receptor expression and subsequent trafficking to the CNS and not regulation of either Th1 or Th17 responses although DLL4 has been reported to have that function. DLL4 appears to be a significant molecule involved in the pathogenesis of EAE as it has a greater ability than DLL1 or Jagged 1 to regulate T cell activation. That finding together with our preliminary data indicating that T cell activation with anti-CD3, anti-CD28 and recombinant DLL4, but not recombinant DLL1 or Jagged1, up-regulated chemokine receptors provides strong rationale to pursue DLL4- mediated Notch regulation of T cell migration in EAE as a critical element in the pathogenesis of disease. Therefore, our overall hypothesis is that DLL4 regulates EAE development by modulating T cell effector trafficking mechanisms. Three specific aims are proposed to directly test this idea, determine the mechanism behind the original observation and translate these findings into a novel therapy for multiple sclerosis (MS). In specific aim 1 we will determine the mechanism behind DLL4 regulation of T cell chemokine receptor expression. In specific aim 2 we will determine whether endothelial DLL4 engagement with T cell Notch cells to regulate T cell chemokine receptor expression. In specific aim 3 we will determine anti-DLL4 treatment efficacy and the role of DLL4 in epitope spreading as a mechanism of relapsing EAE. The proposed work therefore has high biomedical significance and will introduce conceptual and technical innovations to the area of MS research.