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The promise of adaptive cancer immunotherapy in treating highly malignant tumors such as glioblastoma multiforme (GBM) can only be realized through expanding its benefits to more patients. Alleviating various modes of immune suppression has so far failed to achieve such expansion, but exploiting endogenous immune enhancers among mutated cancer genes could represent a more direct approach to immunotherapy improvement. We found that Isocitrate Dehydrogenase-1 (IDH1), which is commonly mutated in gliomas, enhances glioma vaccine efficacy in mice and discerns long from short survivors after vaccine therapy in GBM patients. Extracellular IDH1 directly enhanced T cell responses to multiple tumor antigens, and prolonged experimental glioma cell lysis. Moreover, IDH1 specifically bound to and exhibited sialidase activity against CD8. By contrast, mutant IDH1R132H lacked sialidase activity, delayed killing in glioma cells, and decreased host survival after immunotherapy. Overall, our findings identify IDH1 as an immunotherapeutic enhancer that mediates the known T cell-enhancing reaction of CD8 desialylation. This uncovers a new axis for immunotherapeutic improvement in GBM and other cancers, reveals novel physiological and molecular functions of IDH1, and hints at an unexpectedly direct link between lytic T cell function and metabolic activity in target cells.

Sporadic Alzheimer’s disease, the most common neurodegenerative disorder of aging, is characterized by cerebral plaques and neurofibrillary tangles. Experimental rodents develop plaques but neither tangles nor substantial neurodegeneration under conditions that guarantee Alzheimer’s in humans, suggesting rodents lack critical co-initiation factors. Accumulation of antigen-reactive memory CD8 T cells increases with aging, and was recently revealed as a hallmark of human Alzheimer’s. The impact of this process on disease initiation, however, has not been established because age-related T cell changes are muted in rodents. We developed a mouse model of human-like CD8 T cell aging that promotes antigen-reactive memory CD8 T cell accumulation. Here we show that these “hiT” mice develop all major hallmarks of Alzheimer’s with aging, including tangle-like inclusions and substantial neurodegeneration. Antigen-reactive CD8 T cells analogous to those in hiT mice increased in Alzheimer’s brain, but decreased earlier in blood, where their loss effectively distinguished the Alzheimer’s continuum from aging controls. Our findings establish a clinically relevant mouse model for sporadic Alzheimer’s and show that age-related immune dysfunction critically contributes to its initiation. They also identify useful immune-based targets to track and potentially treat human Alzheimer’s, while validating a model system to examine age-related disease immuno-biology more generally.

Mitigating effects of aging on human health remains elusive because aging impacts multiple systems simultaneously, and because experimental animals exhibit critical aging differences relative to humans. Separation of aging into discrete processes may identify targetable drivers of pathology, particularly when applied to human-specific features. Gradual homeostatic expansion of CD8 T cells dominantly alters their function in aging humans but not in mice. Injecting T cells into athymic mice induces rapid homeostatic expansion, but its relevance to aging remains uncertain. We hypothesized that homeostatic expansion of T cells injected into T-deficient hosts models physiologically relevant CD8 T cell aging in young mice, and aimed to analyze age-related T cell phenotype and tissue pathology in such animals. Indeed, we found that such injection conferred uniform age-related phenotype, genotype, and function to mouse CD8 T cells, heightened age-associated tissue pathology in young athymic hosts, and humanized amyloidosis after brain injury in secondary wild-type recipients. This validates a model conferring a human-specific aging feature to mice that identifies targetable drivers of tissue pathology. Similar examination of independent aging features should promote systematic understanding of aging and identify additional targets to mitigate its effects on human health.

Cancer vaccines reproducibly cure laboratory animals and reveal encouraging trends in brain tumor (glioma) patients. Identifying parameters governing beneficial vaccine-induced responses may lead to the improvement of glioma immunotherapies. CD103(+) CD8 T cells dominate post-vaccine responses in human glioma patients for unknown reasons, but may be related to recent thymic emigrant (RTE) status. Importantly, CD8 RTE metrics correlated with beneficial immune responses in vaccinated glioma patients.We show by flow cytometry that murine and human CD103(+) CD8 T cells respond better than their CD103(-) counterparts to tumor peptide-MHC I (pMHC I) stimulation in vitro and to tumor antigens on gliomas in vivo.Glioma responsive T cells from mice and humans both exhibited intrinsic de-sialylation-affecting CD8 beta. Modulation of CD8 T cell sialic acid with neuraminidase and ST3Gal-II revealed de-sialylation was necessary and sufficient for promiscuous binding to and stimulation by tumor pMHC I. Moreover, de-sialylated status was required for adoptive CD8 T cells and lymphocytes to decrease GL26 glioma invasiveness and increase host survival in vivo. Finally, increased tumor ST3Gal-II expression correlated with clinical vaccine failure in a meta-analysis of high-grade glioma patients.Taken together, these findings suggest that de-sialylation of CD8 is required for hyper-responsiveness and beneficial anti-glioma activity by CD8 T cells. Because CD8 de-sialylation can be induced with exogenous enzymes (and appears particularly scarce on human T cells), it represents a promising target for clinical glioma vaccine improvement.

Dendritic cell (DC) vaccines for glioblastoma (GBM) can effectively extend overall patient survival, but they are not curative. Younger patients responded poorly to vaccination in ours and other trials. Mutations in isocitrate dehydrogenase 1 (IDH1) are commonly found in younger patients, encouraging the hypothesis that IDH1 mutation may subvert the clinical benefits of DC vaccination. Sequencing IDH1-mutated human GBM samples revealed an increase in IDH1 mutated tumor tissue after vaccination, consistent with this hypothesis. This led us to consider whether CTL recognition might be functionally altered by IDH1 and/or its mutation. Indeed, alloreactive CD8+ hybridoma cells exhibited significantly delayed lysis of GL26 cells expressing mutant IDH1 relative to untransfected GL26, but significantly increased lysis of GL26 transfected with unmutated IDH1. In contrast, wild-type and mutant IDH1 transfectants of GL26 exhibited identical sensitivity to imidazole-induced cell death, as well as identical MHC I expression. Moreover, preliminary studies suggest that wild-type and mutant IDH1 transfectants of GL26 are differentially sensitive to DC vaccination, with mutant IDH1 abrogating the longer survival conferred by such treatment. We therefore examined the possibility that these observed differences were mediated by a novel, immune-specific property of IDH1. Generalized sialidase activity can de-sialylate the CD8 coreceptor on T cells, and such modification enhances CD8 binding to MHC I, thereby modulating T cell responsiveness to MHC I-bound peptides. As the IDH1 catalytic site is structurally similar to microbial sialidase, we hypothesized that IDH1 possesses CD8-directed sialidase activity capable of enhancing CTL lysis, and that IDH1mutation critically diminishes this activity. Accordingly, IDH1 treatment increased binding to tumor pHLA multimers and to PNA lectin by human CD8 T cells, with the pHLA binding inhibited by either free sialic acid prior to treatment, or by anti-CD3 antibody after treatment. In addition, IDH1 treatment increased binding to several tumor pMHCI multimers by mouse CD8 T cells, and markedly increased IFN-γ production in response to stimulation by such multimers. Finally, labeled IDH1 bound to the surface of spleen cells, and physiologic concentrations of IDH1 specifically associated with a putative surface heterodimer resembling the CD8 coreceptor in murine T cell lysates. Together, these results suggest that wild-type IDH1possesses immune-specific sialidase function that enhances CTL lysis. In contrast, mutant IDH1 appears to delay immune lysis of tumor cells expressing it, and abrogates vaccine benefits, potentially by diminishing its immune-specific sialidase function. Citation Format: Ryan Cordner, Michelle Jhun, Akanksha Panwar, HongQiang Wang, Nicole Yeager, Joseph McAbee, Armen Mardiros, Akane Takei, Xuemo Fan, Emmaunel Jouanneau, Keith Black, Christopher Wheeler. IDH1 modulates the immune response to glioblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-333. doi:10.1158/1538-7445.AM2013-LB-333