During central nervous system (CNS) viral infections, interactions between leukocytes and glial cells may impact disease pathogenesis. The goal of the proposed research is to elucidate the in vivo dynamic nature of T cell-glial cell interactions during CNS injury and T cell mechanisms that manipulate glial responses. Intracerebral (i.e.) infection of mice with lymphocytic choriomeningitis virus (LCMV) results in fatal meningitis driven by viral specific CD8+ T cells. During disease, decreased blood brain barrier (BBB) integrity is observed. Astrocytes are a critical component of the BBB and, importantly, are targeted and infected by LCMV after i.e. inoculation. Additionally, CTL interactions with astrocytes have been noted in situ. Anticonvulsants delay LCMV induced mortality, indicating that seizures may cause early fatality. Astrocytes, and associated increases in Ca2+ fluxes and glutamate release, have been linked with seizure induction. To determine the in vivo interactions between virus-specific CD8+T cells and infected CNS targets, particularly astrocytes, during acute meningitis, state of the art techniques including viral reverse genetics, fluorescently tagged LCMV specific CD8+T cells and one and two-photon laser scanning microscopy will be employed. Fluorescently tagged LCMV will be used to infect mice that have received naive CFP-labeled LCMV specific CD8+ T cells. One and two-photon laser scanning microscopy will be used to monitor the static and dynamic interactions of LCMV specific CD8+ effector T cells and infected glia, to define the importance of CNS localization and elucidate novel mechanisms of CTL interactions in the CNS. Our hypothesis is that CTL targeting of astrocytic foot processes that comprise the BBB is responsible for the fatal injury observed during LCMV induced meningitis. To identify basic CTL CNS dynamics and novel mechanisms underlying CNS pathogenesis, we will examine real time CTL behavior with infected target cells and glial Ca2+ wave propagation, assess the importance of CTL positioning in the CNS and conduct a gene array to define novel mechanisms of disease. These data should provide insights into how CTL damage the brain during virus induced meningitis. Infection of the central nervous system (CNS) by a variety of viruses, including HIV, HTLV-1 and LCMV, results in immune cell recruitment into this normally immune "privileged" site. Currently, our understanding of how T cell-glial cell interactions impact pathogenesis in the CNS is limited. This work is designed to generate a fundamental knowledge of immune mediated mechanisms that shape neurological disease development after viral infection such that appropriate therapeutic approaches can be evaluated. [unreadable] [unreadable] [unreadable]