? Sindbis Virus (SV) is an alphavirus that induces an immune response in the central nervous system (CNS) of infected mice. In this model, SV preferentially replicates in neurons of the CNS and not in astrocytes or microglia, collectively referred to as glial cells. Upon initiation of neuronal damage in other models, both astrocytes and microglia have been shown to play a role in the elicited immune response, primarily by the release of chemokines that recruit activated leukocytes to the site of secretion via a chemotactic gradient. There is some evidence that neurons also express a unique chemokine, fractalkine that may be involved in activating glia. Our preliminary studies have demonstrated that mRNA specific for monocyte chemoattractant protein-1 (MCP-1) is upregulated in the brains of SV-infected but not mock-infected (PBS), or uninfected controls by Rnase Protection Assay. We propose to exploit the imperviousness of astrocytes and microglia to SV replication in order to study the initiation of inflammation within the CNS of infected mice by the following aims: 1) to determine which resident cells in the CNS are responsible for the expression of MCP-1 following infection with SV by in situ hybridization and immunohistochemistry 2) to use primary cultures of cortical neurons, astrocytes, and microglia in order to study their ability to express MCP-1 in vitro when exposed to SV 3) to determine if MCP-1 plays a role in eliciting inflammation in the CNS using MCP-1 knock-out mice and 4) to assess whether SV-infected neurons signal glia via fractalkine to initiate the immune response. ? ? ?
