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My dissertation project in the lab of Dr. Stanley Perlman is to determine the basis of heteroclitic immunity and to use this information to facilitate virus clearance from the infected central nervous system and for vaccine development. Virus persistence and recrudescence in the central nervous system (CNS) of C57BL/6 (B6) mice infected with a neurotropic strain of mouse hepatitis virus (JHMV) is augmented by the selection of viral variants mutated in an immunodominant CD8 T cell epitope S510. Two CD8 T cell epitopes are recognized in B6 mice, but only one of them (epitope S510) undergoes cytotoxic lymphocyte (CTL) escape. The second epitope (epitope S598) exhibits lower functional avidity and is not protective when escape occurs at the first epitope. The second, weaker epitope can be modified so it exhibits greater functional avidity. Immunization with this “improved” epitope results in a stronger and more protective immune response to the native S598 epitope (‘heteroclitic epitope’). The first goal of my project will be to identify other changes in the S598 epitope that result in a heteroclitic response and verify their role in preventing CTL escape in the infected CNS. The second major goal will be to isolate CD8 T cells that recognize the S598 epitope after immunization with either the native epitope, which results in a weak response or the heteroclitic S598 epitope, which results in a stronger response to the original epitope. I will then express the T cell receptor with the ultimate goal of determining the structure of each T cell receptor co-crystallized with the MHC class I/peptide S598 complex. In a second project, I will develop a recombinant attenuated JHMV that expresses the heteroclitic epitope using reverse genetics. The recombinant attenuated JHMV rarely causes acute encephalitis, but has a strong tropism for oligodendrocytes and therefore causes demyelination. This recombinant virus will be used to assess the effect of the heteroclitic epitope on demyelination. In a third project, I will investigate a downstream effect of CTL escape-macrophage recruitment into the infected central nervous system, with subsequent myelin destruction. For this project, we have obtained mice that overexpress a macrophage chemoattractant. These transgenic mice will be used to investigate the mechanism of macrophage-mediated destruction of myelin and may lead to novel approaches to preventing this process.
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