The broad objective of this proposal is to understand the molecular mechanisms that regulate the activation status and function of low versus high avidity tumor-antigen specific T cells in non-tolerized and tolerized mice. Identification of these mechanisms is the first step toward developing approaches that can allow for more effective activation of T cells with a range of avidities specific for cancer antigens. The success of immunization against many viruses is in part due to the induction of a virus specific, high avidity CD8+ T cell repertoire with a sufficient memory T cell compartment in healthy hosts. In contrast, successful vaccination in cancer bearing hosts requires bypassing multiple mechanisms of immune tolerance. Many of the known tumor antigens are over-expressed tissue- specific antigens. Mechanisms of T cell tolerance must exist to prevent autoimmunity against self- antigens. These same mechanisms that establish and maintain self-tolerance are likely contributors to the lack of effectiveness of T cells in vivo that is often observed in cancer patients. The implications of tolerance induction are that cancer-specific high avidity T cell populations are deleted or suppressed, and that cancer vaccines must either break tolerance in anergic T cells or activate populations of low avidity T cells which, based on their weak reactivity, may escape active tolerance induction. Until recently, the tools to understand the fate of the high avidity and low avidity cancer specific CD8+ T cell repertoires in cancer bearing hosts were not available. The HER-2/neu transgenic (neu-N) mouse model of spontaneous mammary tumors provides the opportunity to evaluate this issue using a natural tumor antigen, HER-2/neu (neu). In vaccinated parental FVB/N mice, the majority of CD8+ T cells are of high avidity and directed against an immunodominant antigen, RNEU420-429. In contrast, in vaccinated neu-N mice, most T cell responses are weak, of low avidity, and directed against multiple epitopes. To understand the mechanisms that regulate the activation and function of CD8+ T cells of both low and high avidity, we have developed high and low avidity RNEU420-429-specific TCR transgenic mice.
In aim 1 we will compare and characterize the fate of the high avidity versus the low avidity RNEU420-429-specific CD8+ T cells in vivo, and determine the role regulatory T cells (Tregs) play in controlling the function of activated and memory high avidity versus low avidity T cells in vivo.
In aim 2, we will evaluate the role of microRNA (miRNA) as post- transcriptional regulators of T cell function in the high avidity versus low avidity RNEU420-429-specific CD8+ T cells.
In aim 3, we will evaluate the high avidity versus low avidity RNEU420-429-specific CD8+ TCR transgenic T cells for changes in T cell signaling pathways.

Public Health Relevance

The broad objective of this proposal is to understand the molecular mechanisms that regulate the activation status and function of low versus high avidity tumor-antigen specific T cells in non-tolerized and tolerized mice. Specifically, we will evaluate a number of mechanisms that may differentially regulate low versus high avidity T cells including: regulatory T cells, T cell signaling pathways, and post-transcriptional regulation.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Cancer Immunopathology and Immunotherapy Study Section (CII)
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Mccarthy, Susan A
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Johns Hopkins University
Internal Medicine/Medicine
Schools of Medicine
United States
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