Multiple sclerosis (MS) is a human demyelinating disease characterized by multifocal regions of inflammation, progressive myelin loss within the central nervous system (CNS), and eventual failure to remyelinate damaged axons. These problems suggest deficiencies in recruiting and/or maturation of oligodendrocyte progentior cells (OPCs) and highlight cell replacement therapies to promote remyelination. We have used a model of viral-induced demyelination to characterize signaling cues associated with positional migration of transplanted remyelination-competent cells. Although successful transplantation of rodent-derived glial cell types into models of MS has been performed, the mechanisms by which these cells navigate within an inflammatory environment created by a persistent virus has not been defined. Infection of the mouse CNS with the neurotropic JHM strain of mouse hepatitis virus (JHMV) results in an immune-mediated demyelinating disease with clinical and histologic similarities to MS. Surgical engraftment of GFP+ neural stem cells (NSCs) into spinal cords of JHMV-infected mice with established demyelination results in migration, proliferation, and differentiation of the cells into OPCs and mature oligodendrocytes that is associated with increased axonal remyelination. Treatment with anti-CXCL12 [stromal derived factor-1α, (SDF-1α)] blocking serum resulted in a marked impairment in migration and proliferation of engrafted stem cells. Moreover, small molecule-mediated antagonism of CXCR4, but not CXCR7, impaired migration and proliferation, to an extent similar to that with anti-CXCL12 treatment. These data highlight the importance of the CXCL12:CXCR4 pathway in regulating homing of engrafted stem cells to sites of tissue damage within the CNS of mice persistently infected with a neurotropic virus undergoing immune-mediated demyelination.chemokine receptors | chemokines | demyelination | trafficking | glia

Chronic expression of CXC chemokine ligand 10 (CXCL10) in the central nervous system (CNS) following infection with the neurotropic JHM strain of mouse hepatitis virus (JHMV) is associated with an immune-mediated demyelinating disease. Treatment of mice with anti-CXCL10 neutralizing antibody results in limited CD4+ T cell infiltration into the CNS accompanied by a reduction in white matter damage. The current study determines the antigen-specificity of the T lymphocytes present during chronic disease and evaluates how blocking CXCL10 signaling affects retention of virusspecific T cells within the CNS. CXCL10 neutralization selectively reduced accumulation and/or retention of virus-specific CD4+ T cells, yet exhibited limited effect on virus-specific CD8+ T cells. The response of CXCL10 neutralization on virus-specific T cell subsets is not due to differential expression of the CXCL10 receptor CXCR3 on T cells as there was no appreciable difference in receptor expression on virus-specific T cells during either acute or chronic disease. These findings emphasize the importance of virus-specific CD4+ T cells in amplifying demyelination in JHMVinfected mice. In addition, differential signals are required for trafficking and retention of virusspecific CD4+ and CD8+ T cells during chronic demyelination in JHMV-infected mice.

The role of the CXC chemokine ligand 9 (CXCL9) in host defense following infection with mouse hepatitis virus (MHV) was determined. Inoculation of the central nervous system (CNS) of CXCL9−/− mice with MHV resulted in accelerated and increased mortality compared to wildtype mice supporting an important role for CXCL9 in antiviral defense. In addition, infection of RAG1−/− or CXCL9−/− mice with a recombinant MHV expressing CXCL9 (MHV-CXCL9) resulted in protection from disease that correlated with reduced viral titers within the brain and NK cell-mediated protection in the liver. Survival in MHV-CXCL9-infected CXCL9−/− mice was associated with reduced viral burden within the brain that coincided with increased T cell infiltration. Similarly, viral clearance from the livers of MHV-CXCL9-infected mice was accelerated but independent of increased T cell or NK cell infiltration. These observations indicate that CXCL9 promotes protection from coronavirus-induced neurological and liver disease.