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Apoptosis-regulated low avidity cancer-specific CD8+ T cells can be rescued to eliminate HER-2/neu expressing tumors by costimulatory agonists in tolerized mice

ABSTRACT: A major barrier of vaccines as cancer treatment is their failure to activate and maintain a complete cancer-specific CD8+ effector T cell repertoire. Low avidity T cells are more likely to escape clonal deletion in the thymus when compared to higher avidity T cells, and therefore comprise the major population of effector T cells available for activation in cancer patients. However, low avidity T cells fail to traffic into the tumor microenvironment and function in eradicating tumor under optimal vaccination conditions as opposed to higher avidity T cells that escape clonal deletion and do function in tumor killing. We utilized high and low avidity TCR transgenic CD8+ T cells specific for the immunodominant epitope of HER-2/neu (RNEU420-429) to identify signaling pathways responsible for the inferior activity of low avidity T cells. Adoptive transfer of these cells into tumor-bearing vaccinated mice identified members of apoptosis pathways as being upregulated in low avidity T cells. The increased expression of pro-apoptotic proteins by low avidity T cells promoted their own cell death and also that of other tumor-specific CD8+ T cells within their local environment. Importantly, this pro-apoptotic effect was overcome using a strong costimulatory signal that prevents activation-induced cell death and enables low avidity T cells to traffic into the tumor and assist in tumor clearance. These findings identify new therapeutic opportunities for activating the most potent anticancer T cell responses.

ORGANISM(S): Mus musculus

PROVIDER: GSE54020 | GEO | 2014/01/14

SECONDARY ACCESSION(S): PRJNA234368

REPOSITORIES: GEO

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Project description:The avidity of the T-cell receptor (TCR) for antigenic peptides presented by the MHC (pMHC) on cells is an essential parameter for efficient T cell-mediated immunity. Yet, whether the TCR-ligand avidity can drive the clonal evolution of virus antigen-specific CD8 T cells, and how this process is determined in latent Cytomegalovirus (CMV)- against Epstein-Barr virus (EBV)-mediated infection remains largely unknown. Here, we quantified monomeric TCR-pMHC dissociation rates on CMV- and EBV-specific individual TCR-alpha-beta clonotypes and polyclonal CD8 T cell populations in healthy donors over a follow-up time of 15-18 years. Within CMV/pp65-specific T cell repertoires, a progressive contraction of clonotypes with high TCR-pMHC avidity and low CD8 binding dependency was observed, leading to an overall avidity decline during long-term antigen exposure. We identified a unique transcriptional signature preferentially expressed by high-avidity CMV/pp65-specific T cell clonotypes, including the inhibitory receptor LILRB1. Interestingly, T cell clonotypes of high-avidity showed higher LILRB1 expression than the low-avidity ones and LILRB1 blockade moderately increased T cell proliferation. Similar findings were made for CD8 T cell repertoires specific for the CMV/IE-1 epitope. There was a gradual in vivo loss of high-avidity T cells with time for both CMV specificities, corresponding to virus-specific CD8 T cells expressing enhanced LILRB1 levels. In sharp contrast, the EBV/BMFL1-specific T cell clonal composition and distribution, once established, displayed an exceptional stability, unrelated to TCR-pMHC binding avidity or LILRB1 expression. Together, these findings reveal an overall long-term avidity decline of CMV- but not EBV-specific T cell clonal repertoires, highlighting the differing role played by TCR-ligand avidity over the course of these two latent herpesvirus infections. Our data suggest that the inhibitor receptor LILRB1 potentially restricts the clonal expansion of high-avidity CMV-specific T cell clonotypes during latent infection. We propose that the mechanisms regulating the long-term outcome of CMV- and EBV-specific memory CD8 T cell clonotypes in humans are distinct.

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Apoptosis-regulated low avidity cancer-specific CD8+ T cells can be rescued to eliminate HER-2/neu expressing tumors by costimulatory agonists in tolerized mice

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