CD8+ T cells controlling pathogens or tumors must function at sites where oxygen tension is frequently low, and never as high as under atmospheric culture conditions. However, T-cell function in vivo is generally analyzed indirectly, or is extrapolated from in vitro studies under nonphysiologic oxygen tensions. In this study, we delineate the role of physiologic and pathologic oxygen tension in vitro during reactivation and differentiation of tumor-specific CD8 + T cells. Using CD8 + T cells from pmel-1 mice, we observed that the generation of CTLs under 5% O 2 , which corresponds to physioxia in lymph nodes, gave rise to a higher effector signature than those generated under atmospheric oxygen fractions (21% O 2 ). Hypoxia (1% O 2 ) did not modify cytotoxicity, but decreasing O 2 tensions during CTL and CD8 + tumor-infiltrating lymphocyte reactivation dose-dependently decreased proliferation, induced secretion of the immunosuppressive cytokine IL-10, and upregulated the expression of CD137 (4-1BB) and CD25. Overall, our data indicate that oxygen tension is a key regulator of CD8 + T-cell function and fate and suggest that IL-10 release may be an unanticipated component of CD8 + T cell-mediated immune responses in most in vivo microenvironments. Keywords: CD8+ T cell r Oxygen r Hypoxia r IL-10 r T-cell reactivation Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionIn a healthy physiologic context, oxygen tensions in mammalian tissues are tightly regulated, but still show significant variation both between tissues and within the same tissue (Supporting Information Fig. 1A) [1][2][3]. However, oxygen tensions are far below physiologic values in different pathologic conditions, mostly involving inflammation [4], solid tumors [5,6], and infections [7]. In contrast to sufficient oxygen supply (i.e. normoxia), oxygen deprivation (i.e. hypoxia) leads to cellular responses involving Correspondence: Dr. Paul R. Walker e-mail: Paul.Walker@hcuge.ch stabilization of HIFs (hypoxia-inducible factors), transcription factors that are composed of an inducible α-subunit (i.e. HIF-1α, HIF-2α, or HIF-3α) together with a constitutive β-subunit (i.e. HIF-1β, HIF-2β, or HIF-3β) [8]. Upon stabilization, HIFs transcribe various genes with HIF-responsive elements in their promoter; these include those that increase angiogenesis (e.g. VEGF) and glucose metabolism (e.g. glucose transporters) [9]. Interestingly, HIF-1α and HIF-2α can have unique, redundant, or opposing roles [9,10]. Furthermore, while HIF-1α is described to be stabilized and active below 2% O 2 in an acute manner, HIF-2α has been shown to be stable below 5% O 2 in a chronic manner [11,12]. However, although HIFs are central to many hypoxia responses, certain effects have been shown to be HIF-independent [13][14][15]. Intriguingly, HIF-1α can also be involved in immune cell activation Eur. J. Immunol. 2015Immunol. . 45: 2263Immunol. -2275 under atmospheric oxygen fractions (AtO 2 ; i.e. 21%), as rep...

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Vaccines that can coordinately induce multi-epitope T cellmediated immunity, T helper functions, and immunologic memory may offer effective tools for cancer immunotherapy. Here, we report the development of a new class of recombinant protein cancer vaccines that deliver different CD8 þ and CD4 þ T-cell epitopes presented by MHC class I and class II alleles, respectively. In these vaccines, the recombinant protein is fused with Z12, a novel cell-penetrating peptide that promotes efficient protein loading into the antigen-processing machinery of dendritic cells. Z12 elicited an integrated and multi-epitopic immune response with persistent effector T cells. Therapy with Z12-formulated vaccines prolonged survival in three robust tumor models, with the longest survival in an orthotopic model of aggressive brain cancer. Analysis of the tumor sites showed antigen-specific T-cell accumulation with favorable modulation of the balance of the immune infiltrate. Taken together, the results offered a preclinical proof of concept for the use of Z12-formulated vaccines as a versatile platform for the development of effective cancer vaccines. Cancer Res; 75(15);

In the context of adoptive T cell transfer (ACT) for cancer treatment, it is crucial to generate in vitro large amounts of tumor-specific CD8 T cells with high potential to persist in vivo. PD-1, Tim3, and CD39 have been proposed as markers of tumor-specific tumor-infiltrating CD8 T lymphocytes (CD8 TILs). However, these molecules are highly expressed by terminally differentiated exhausted CD8 T cells (Tex) that lack proliferation potential. Therefore, optimized strategies to isolate tumor-specific TILs with high proliferative potential, such as Tcf1+ precursor exhausted T cells (Tpe) are needed to improve in vivo persistence of ACT. Here we aimed at defining cell surface markers that would unequivocally identify Types for precision cell sorting increasing the purity of tumor-specific PD-1+ Tcf1+ Tpe from total TILs. Transcriptomic analysis of Tpe vs. Tex CD8 TIL subsets from B16 tumors and primary human melanoma tumors revealed that Tpes are enriched in Slamf6 and lack Entpd1 and Havcr2 expression, which encode Slamf6, CD39, and Tim3 cell surface proteins, respectively. Indeed, we observed by flow cytometry that CD39-Tim3-Slamf6+ PD-1+ cells yielded maximum enrichment for tumor specific PD-1+ Tcf1+ OT1 TILs in B16.OVA tumors. Moreover, this population showed higher re-expansion capacity upon an acute infection recall response compared to the CD39+ counterparts or bulk PD-1+ TILs. Hence, we report an enhanced sorting strategy (CD39-Tim3-Slamf6+ PD-1+) of Tpes. In conclusion, we show that optimization of CD8 TIL cell sorting strategy is a viable approach to improve recall capacity and in vivo persistence of transferred cells in the context of ACT.