Progressively Enhancing Stemness of Adoptively Transferred T Cells with PI3Kδ Blockade Improves Metabolism and Antitumor Immunity.

Generating stem-like memory T cells (TSCM) is a potential strategy to improve adoptive immunotherapy. Elucidating optimal ways to modulate signaling pathways that enrich TSCM properties could identify approaches to achieve this goal. We discovered herein that blocking the PI3Kδ pathway pharmaceutically to varying degrees can generate T cells with increasingly heightened stemness properties, based on the progressive enrichment of the transcription factors Tcf1 and Lef1. T cells with enhanced stemness features exhibited metabolic plasticity, marked by improved mitochondrial function and glucose uptake after tumor recognition. Conversely, T cells with low or medium stemness were less metabolically dynamic, vulnerable to antigen-induced cell death, and expressed more inhibitory checkpoint receptors. Only T-cell receptor-specific or chimeric antigen receptor (CAR)-specific T cells with high stemness persisted in vivo and mounted protective immunity to tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor-infiltrating lymphocytes and CAR T cells with elevated stemness properties, in turn bolstering their capacity to regress human solid tumors. The stemness level of T cells in vitro was important, ultimately impacting their efficacy in mice bearing three distinct solid tumors. Lef1 and Tcf1 sustained antitumor protection by donor high CD8+ TSCM or CD4+ Th17SCM, as deletion of either one compromised the therapeutic efficacy. Collectively, these findings highlight the importance of strategic modulation of PI3Kδ signaling in T cells to induce stemness and lasting protective responses to solid tumors. SIGNIFICANCE: Elevating T-cell stemness by progressively blocking PI3Kδ signaling during ex vivo manufacturing of adoptive cell therapies alters metabolic and functional properties to enhance antitumor immunity dependent on Tcf1 and Lef1.

mWTX-330, an IL-12 INDUKINE Molecule, Activates and Reshapes Tumor-Infiltrating CD8+ T and NK Cells to Generate Antitumor Immunity.

IL-12 is a pleotropic inflammatory cytokine, which has broad stimulatory effects on various immune cell populations, making it an attractive target for cancer immunotherapy. However, despite generating robust antitumor activity in syngeneic murine tumor models, clinical administration of IL-12 has been limited by severe toxicity. mWTX-330 is a selectively inducible INDUKINE molecule comprised of a half-life extension domain and an inactivation domain linked to chimeric IL-12 by tumor protease-sensitive linkers. Systemic administration of mWTX-330 in mice was well tolerated, resulted in robust antitumor immunity in multiple tumor models, and preferentially activated tumor-infiltrating immune cells rather than immune cells present in peripheral tissues. Antitumor activity was dependent on in vivo processing of the protease cleavable linkers and required CD8+ T cells for full efficacy. Within the tumor, mWTX-330 increased the frequency of cross-presenting dendritic cells (DC), activated natural killer (NK) cells, skewed conventional CD4+ T cells toward a T helper 1 (TH1) phenotype, drove regulatory T cells (Treg) fragility, and increased the frequency of polyfunctional CD8+ T cells. mWTX-330 treatment also increased the clonality of tumor-infiltrating T cells by expanding underrepresented T-cell receptor (TCR) clones, drove CD8+ T and NK cells towards increased mitochondrial respiration and fitness, and decreased the frequency of TOX+ exhausted CD8+ T cells within the tumor. A fully human version of this INDUKINE molecule was stable in human serum, was reliably and selectively processed by human tumor samples, and is currently in clinical development.

The degree of T cell stemness differentially impacts the potency of adoptive cancer immunotherapy in a Lef-1 and Tcf-1 dependent manner.

Generating stem memory T cells (T SCM ) is a key goal for improving cancer immunotherapy. Yet, the optimal way to modulate signaling pathways that enrich T SCM properties remains elusive. Here, we discovered that the degree to which the PI3Kδ pathway is blocked pharmaceutically can generate T cells with differential levels of stemness properties. This observation was based on the progressive enrichment of transcriptional factors of stemness (Tcf-1 and Lef-1). Additional investigation revealed that T cells with high stemness features had enhanced metabolic plasticity, marked by heightened mitochondrial function and glucose uptake. Conversely, T cells with low or medium features of stemness expressed more inhibitory checkpoint receptors (Tim-3, CD39) and were vulnerable to antigen-induced cell death. Only TCR-antigen specific T cells with high stemness persisted following adoptive transfer in vivo and mounted protective immunity to melanoma tumors. Likewise, the strongest level of PI3Kδ blockade in vitro generated human tumor infiltrating lymphocytes (TILs) and CAR T cells with heightened stemness properties, in turn bolstering their capacity to regress human mesothelioma tumors. We find that the level of stemness T cells possess in vitro differentially impacts their potency upon transfer in three tumor models. Mechanistically, both Lef-1 and Tcf-1 sustain anti-tumor protection by high T SCM , as deletion of either one compromised cellular therapy. Collectively, these findings highlight the therapeutic potential of carefully modulating PI3Kδ signaling in T cells to confer high stemness and mediate protective responses to solid tumors.

B cells imprint adoptively transferred CD8+ T cells with enhanced tumor immunity.

BACKGROUND: Adoptive T cell transfer (ACT) therapy improves outcomes in patients with advanced malignancies, yet many individuals relapse due to the infusion of T cells with poor function or persistence. Toll-like receptor (TLR) agonists can invigorate antitumor T cell responses when administered directly to patients, but these responses often coincide with toxicities. We posited that TLR agonists could be repurposed ex vivo to condition T cells with remarkable potency in vivo, circumventing TLR-related toxicity. METHODS: In this study we investigated how tumor-specific murine CD8+ T cells and human tumor infiltrating lymphocytes (TILs) are impacted when expanded ex vivo with the TLR9 agonist CpG. RESULTS: Herein we reveal a new way to reverse the tolerant state of adoptively transferred CD8+ T cells against tumors using TLR-activated B cells. We repurposed the TLR9 agonist, CpG, commonly used in the clinic, to bolster T cell-B cell interactions during expansion for ACT. T cells expanded ex vivo from a CpG-treated culture demonstrated potent antitumor efficacy and prolonged persistence in vivo. This antitumor efficacy was accomplished without in vivo administration of TLR agonists or other adjuvants of high-dose interleukin (IL)-2 or vaccination, which are classically required for effective ACT therapy. CpG-conditioned CD8+ T cells acquired a unique proteomic signature hallmarked by an IL-2RαhighICOShighCD39low phenotype and an altered metabolic profile, all reliant on B cells transiently present in the culture. Likewise, human TILs benefitted from expansion with CpG ex vivo, as they also possessed the IL-2RαhighICOShighCD39low phenotype. CpG fostered the expansion of potent CD8+ T cells with the signature phenotype and antitumor ability via empowering a direct B-T cell interaction. Isolated B cells also imparted T cells with the CpG-associated phenotype and improved tumor immunity without the aid of additional antigen-presenting cells or other immune cells in the culture. CONCLUSIONS: Our results demonstrate a novel way to use TLR agonists to improve immunotherapy and reveal a vital role for B cells in the generation of potent CD8+ T cell-based therapies. Our findings have immediate implications in the clinical treatment of advanced solid tumors.

Modeling ex vivo tumor-infiltrating lymphocyte expansion from established solid malignancies.

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) elicits the regression of metastatic malignancies, yet a low proportion of patients achieve complete durable responses. The high incidence of relapse in these patients highlights the need to better understand mechanisms of tumor escape from T cell control. While melanoma has provided the foundation for developing TIL therapy, much less is known about TIL efficacy and relapse in other malignancies. We sought to investigate TIL characteristics in mouse tumors which have not been studied in this setting. Here, we expanded murine TIL ex vivo in IL-2 from fragments of multiple tumor models, including oral cavity cancer models of varying immunogenicity. Additionally, TIL was expanded from pmel-1 mice bearing B16F10 melanoma, yielding an enriched population of tumor-infiltrating TCR transgenic T cells. Murine TIL are similar to human TIL in that they express high levels of inhibitory receptors (PD-1, Tim-3, etc.) and can be expanded ex vivo in IL-2 extensively. Of clinical relevance, we draw parallels between murine and human oral cavity cancer TIL, evaluating relationships between inhibitory receptor expression and function. This platform can be used by labs even in the absence of clinical specimens or clean cell facilities and will be important to more broadly understand TIL phenotypes across many different malignancies.

Alterations of lipid metabolism provide serologic biomarkers for the detection of asymptomatic versus symptomatic COVID-19 patients.

COVID-19 pandemic exerts a health care emergency around the world. The illness severity is heterogeneous. It is mostly unknown why some individuals who are positive for SARS-CoV-2 antibodies stay asymptomatic while others show moderate to severe disease symptoms. Reliable biomarkers for early detection of the disease are urgently needed to attenuate the virus's spread and help make early treatment decisions. Bioactive sphingolipids play a crucial role in the regulation of viral infections and pro-inflammatory responses involved in the severity of COVID-19. However, any roles of sphingolipids in COVID-19 development or detection remain unknown. In this study, lipidomics measurement of serum sphingolipids demonstrated that reduced sphingosine levels are highly associated with the development of symptomatic COVID-19 in the majority (99.24%) SARS-CoV-2-infected patients compared to asymptomatic counterparts. The majority of asymptomatic individuals (73%) exhibited increased acid ceramidase (AC) in their serum, measured by Western blotting, consistent with elevated sphingosine levels compared to SARS-CoV-2 antibody negative controls. AC protein was also reduced in almost all of the symptomatic patients' serum, linked to reduced sphingosine levels, measured in longitudinal acute or convalescent COVID-19 samples. Thus, reduced sphingosine levels provide a sensitive and selective serologic biomarker for the early identification of asymptomatic versus symptomatic COVID-19 patients.

Comparative analysis of antibodies to SARS-CoV-2 between asymptomatic and convalescent patients.

The SARS-CoV-2 viral pandemic has induced a global health crisis, which requires more in-depth investigation into immunological responses to develop effective treatments and vaccines. To understand protective immunity against COVID-19, we screened over 60,000 asymptomatic individuals in the Southeastern United States for IgG antibody positivity against the viral Spike protein, and approximately 3% were positive. Of these 3%, individuals with the highest anti-S or anti-RBD IgG level showed a strong correlation with inhibition of ACE2 binding and cross-reactivity against non-SARS-CoV-2 coronavirus S-proteins. We also analyzed samples from 94 SARS-CoV-2 patients and compared them with those of asymptomatic individuals. SARS-CoV-2 symptomatic patients had decreased antibody responses, ACE2 binding inhibition, and antibody cross-reactivity. Our study shows that healthy individuals can mount robust immune responses against SARS-CoV-2 without symptoms. Furthermore, IgG antibody responses against S and RBD may correlate with high inhibition of ACE2 binding in individuals tested for SARS-CoV-2 infection or post vaccination.

Fundamentals of T Cell Metabolism and Strategies to Enhance Cancer Immunotherapy.

Emerging reports show that metabolic pathways can be targeted to enhance T cell-mediated immunity to tumors. Yet, tumors consume key metabolites in the host to survive, thus robbing T cells of these nutrients to function and thrive. T cells are often deprived of basic building blocks for energy in the tumor, including glucose and amino acids needed to proliferate or produce cytotoxic molecules against tumors. Immunosuppressive molecules in the host further compromise the lytic capacity of T cells. Moreover, checkpoint receptors inhibit T cell responses by impairing their bioenergetic potential within tumors. In this review, we discuss the fundamental metabolic pathways involved in T cell activation, differentiation and response against tumors. We then address ways to target metabolic pathways to improve the next generation of immunotherapies for cancer patients.

Persistent IL-2 Receptor Signaling by IL-2/CD25 Fusion Protein Controls Diabetes in NOD Mice by Multiple Mechanisms.

Low-dose interleukin-2 (IL-2) represents a new therapeutic approach to regulate immune homeostasis to promote immune tolerance in patients with autoimmune diseases, including type 1 diabetes. We have developed a new IL-2-based biologic, an IL-2/CD25 fusion protein, with greatly improved pharmacokinetics and pharmacodynamics when compared with recombinant IL-2 to enhance this type of immunotherapy. In this study, we show that low-dose mouse IL-2/CD25 (mIL-2/CD25), but not an equivalent amount of IL-2, prevents the onset of diabetes in NOD mice and controls diabetes in hyperglycemic mice. mIL-2/CD25 acts not only to expand regulatory T cells (Tregs) but also to increase their activation and migration into lymphoid tissues and the pancreas. Lower incidence of diabetes is associated with increased serum levels of IL-10, a cytokine readily produced by activated Tregs. These effects likely act in concert to lower islet inflammation while increasing Tregs in the remaining inflamed islets. mIL-2/CD25 treatment is also associated with lower anti-insulin autoantibody levels in part by inhibition of T follicular helper cells. Thus, long-acting mIL-2/CD25 represents an improved IL-2 analog that persistently elevates Tregs to maintain a favorable Treg/effector T cell ratio that limits diabetes by expansion of activated Tregs that readily migrate into lymphoid tissues and the pancreas while inhibiting autoantibodies.

IL6 Fuels Durable Memory for Th17 Cell-Mediated Responses to Tumors.

The accessibility of adoptive T-cell transfer therapies (ACT) is hindered by the cost and time required for product development. Here we describe a streamlined ACT protocol using Th17 cells expanded only 4 days ex vivo. While shortening expansion compromised cell yield, this method licensed Th17 cells to eradicate large tumors to a greater extent than cells expanded longer term. Day 4 Th17 cells engrafted, induced release of multiple cytokines including IL6, IL17, MCP-1, and GM-CSF in the tumor-bearing host, and persisted as memory cells. IL6 was a critical component for efficacy of these therapies via its promotion of long-term immunity and resistance to tumor relapse. Mechanistically, IL6 diminished engraftment of FoxP3+ donor T cells, corresponding with robust tumor infiltration by donor effector over regulatory cells for the Day 4 Th17 cell product relative to cell products expanded longer durations ex vivo. Collectively, this work describes a method to rapidly generate therapeutic T-cell products for ACT and implicates IL6 in promoting durable immunity of Th17 cells against large, established solid tumors. SIGNIFICANCE: An abbreviated, 4-day ex vivo expansion method licenses Th17 cells to confer long-lived immunity against solid malignancies via induction of systemic IL6 in the host.See related commentary by Fiering and Ho, p. 3795.

Ex vivo blockade of PI3K gamma or delta signaling enhances the antitumor potency of adoptively transferred CD8+ T cells.

Adoptive T cell transfer therapy induces objective responses in patients with advanced malignancies. Despite these results, some individuals do not respond due to the generation of terminally differentiated T cells during the expansion protocol. As the gamma and delta catalytic subunits in the PI3K pathway are abundant in leukocytes and involved in cell activation, we posited that blocking both subunits ex vivo with the inhibitor IPI-145 would prevent their differentiation, thereby increasing antitumor activity in vivo. However, IPI-145 treatment generated a product with reduced antitumor activity. Instead, T cells inhibited of PI3Kγ (IPI-549) or PI3Kδ (CAL-101 or TGR-1202) alone were more potent in vivo. While T cells coinhibited of PI3Kγ and PI3Kδ were less differentiated, they were functionally impaired, indicated by reduced production of effector cytokines after antigenic re-encounter and decreased persistence in vivo. Human CAR T cells expanded with either a PI3Kγ or PI3Kδ inhibitor possessed a central memory phenotype compared to vehicle cohorts. We also found that PI3Kδ-inhibited CARs lysed human tumors in vitro more effectively than PI3Kγ-expanded or traditionally expanded CAR T cells. Our data imply that sole blockade of PI3Kγ or PI3Kδ generates T cells with remarkable antitumor properties, a discovery that has substantial clinical implications.

Fueling Cancer Immunotherapy With Common Gamma Chain Cytokines.

Adoptive T cell transfer therapy (ACT) using tumor infiltrating lymphocytes or lymphocytes redirected with antigen receptors (CAR or TCR) has revolutionized the field of cancer immunotherapy. Although CAR T cell therapy mediates robust responses in patients with hematological malignancies, this approach has been less effective for treating patients with solid tumors. Additionally, toxicities post T cell infusion highlight the need for safer ACT protocols. Current protocols traditionally expand T lymphocytes isolated from patient tumors or from peripheral blood to large magnitudes in the presence of high dose IL-2 prior to infusion. Unfortunately, this expansion protocol differentiates T cells to a full effector or terminal phenotype in vitro, consequently reducing their long-term survival and antitumor effectiveness in vivo. Post-infusion, T cells face further obstacles limiting their persistence and function within the suppressive tumor microenvironment. Therapeutic manipulation of T cells with common γ chain cytokines, which are critical growth factors for T cells, may be the key to bypass such immunological hurdles. Herein, we discuss the primary functions of the common γ chain cytokines impacting T cell survival and memory and then elaborate on how these distinct cytokines have been used to augment T cell-based cancer immunotherapy.

CAR T Cells in Solid Tumors: Blueprints for Building Effective Therapies.

Genetic redirection of T lymphocytes with chimeric antigen receptors (CARs) has soared from treating cancers preclinically to FDA approval for hematologic malignancies and commercial-grade production scale in under 30 years. To date, solid tumors are less susceptible to CAR therapies and instead have been treated more successfully with immune checkpoint blockade or tumor-infiltrating lymphocyte therapy. Here, we discuss the current challenges in treating solid tumors with CAR T cells, and the obstacles within the host and tumor microenvironment hindering their efficacy. We present a novel three-pronged approach for enhancing the efficacy of CAR T cells whereby a single infusion product can synergize the power of an optimal CAR construct, a highly potent T cell subset, and rejuvenate the endogenous immune response to conquer therapeutically-resistant solid tumors.

When worlds collide: Th17 and Treg cells in cancer and autoimmunity.

The balance between Th17 cells and regulatory T cells (Tregs) has emerged as a prominent factor in regulating autoimmunity and cancer. Th17 cells are vital for host defense against pathogens but have also been implicated in causing autoimmune disorders and cancer, though their role in carcinogenesis is less well understood. Tregs are required for self-tolerance and defense against autoimmunity and often correlate with cancer progression. This review addresses the importance of a functional homeostasis between these two subsets in health and the consequences of its disruption when these forces collide in disease. Importantly, we discuss the ability of Th17 cells to mediate cancer regression in immunotherapy, including adoptive transfer and checkpoint blockade therapy, and the therapeutic possibilities of purposefully offsetting the Th17/Treg balance to treat patients with cancer as well as those with autoimmune diseases.

Altered homeostasis and development of regulatory T cell subsets represent an IL-2R-dependent risk for diabetes in NOD mice.

The cytokine interleukin-2 (IL-2) is critical for the functions of regulatory T cells (Tregs). The contribution of polymorphisms in the gene encoding the IL-2 receptor α subunit (IL2RA), which are associated with type 1 diabetes, is difficult to determine because autoimmunity depends on variations in multiple genes, where the contribution of any one gene product is small. We investigated the mechanisms whereby a modest reduction in IL-2R signaling selectively in T lymphocytes influenced the development of diabetes in the NOD mouse model. The sensitivity of IL-2R signaling was reduced by about two- to threefold in Tregs from mice that coexpressed wild-type IL-2Rß and a mutant subunit (IL-2RßY3) with reduced signaling (designated NOD-Y3). Male and female NOD-Y3 mice exhibited accelerated diabetes onset due to intrinsic effects on multiple activities in Tregs Bone marrow chimera and adoptive transfer experiments demonstrated that IL-2RßY3 Tregs resulted in impaired homeostasis of lymphoid-residing central Tregs and inefficient development of highly activated effector Tregs and that they were less suppressive. Pancreatic IL-2RßY3 Tregs showed impaired development into IL-10-secreting effector Tregs The pancreatic lymph nodes and pancreases of NOD-Y3 mice had increased numbers of antigen-experienced CD4+ effector T cells, which was largely due to impaired Tregs, because adoptively transferred pancreatic autoantigen-specific CD4+ Foxp3- T cells from NOD-Y3 mice did not accelerate diabetes in NOD.SCID recipients. Our study indicates that the primary defect associated with chronic, mildly reduced IL-2R signaling is due to impaired Tregs that cannot effectively produce and maintain highly functional tissue-seeking effector Treg subsets.

The Lower Limit of Regulatory CD4+ Foxp3+ TCRß Repertoire Diversity Required To Control Autoimmunity.

The TCR repertoire of regulatory T cells (Tregs) is highly diverse. The relevance of this diversity to maintain self-tolerance remains unknown. We established a model where the TCR repertoire of normal polyclonal Tregs was limited by serial transfers into IL-2Rß-/- mice, which lack functional Tregs. After a primary transfer, the donor Treg TCR repertoire was substantially narrowed, yet the recipients remained autoimmune-free. Importantly, upon purification and transfer of donor-derived Tregs from an individual primary recipient into neonatal IL-2Rß-/- mice, the secondary recipients developed autoimmunity. In this study, the Treg TCRß repertoire was reshaped and further narrowed. In contrast, secondary IL-2Rß recipients showed fewer symptoms of autoimmunity when they received donor Tregs that were premixed from several primary recipients to increase their TCRß repertoire diversity. About 8-11% of the Treg TCRß repertoire was estimated to be the minimum required to establish and maintain tolerance in primary IL-2Rß-/- recipients. Collectively, these data quantify where limitations imposed on the Treg TCRß repertoire results in a population of Tregs that cannot fully suppress polyclonal autoreactive T cells. Our data favor a model where the high diversity of the Treg TCR provides a mechanism for Tregs to actively adapt and effectively suppress autoreactive T cells, which are not fixed, but are evolving as they encounter self-antigens.

Promoting Immune Regulation in Type 1 Diabetes Using Low-Dose Interleukin-2.

Dysregulation of the immune system contributes to the breakdown of immune regulation, leading to autoimmune diseases, such as type 1 diabetes (T1D). Current therapies for T1D include daily insulin, due to pancreatic ß-cell destruction to maintain blood glucose levels, suppressive immunotherapy to decrease the symptoms associated with autoimmunity, and islet transplantation. Genetic risks for T1D have been linked to IL-2 and IL-2R signaling pathways that lead to the breakdown of self-tolerance mechanisms, primarily through altered regulatory T cell (Treg) function and homeostasis. In attempt to correct such deficits, therapeutic administration of IL-2 at low doses has gained attention due to the capacity to boost Tregs without the unwanted stimulation of effector T cells. Preclinical and clinical studies utilizing low-dose IL-2 have shown promising results to expand Tregs due to their high selective sensitivity to respond to IL-2. These results suggest that low-dose IL-2 therapy represents a new class of immunotherapy for T1D by promoting immune regulation rather than broadly suppressing unwanted and beneficial immune responses.