Effector Cell Differentiation Research Articles

Lymphedema-Associated Fibroblasts Are Related to Fibrosis and Stage Progression in Patients and a Murine Microsurgical Model.

The driver of secondary lymphedema (SL) progression is chronic inflammation, which promotes fibrosis. Despite advances in preclinical research, a specific effector cell subpopulation as a biomarker for therapy response or stage progression is still missing for SL. Whole skin samples of 35 murine subjects of a microsurgically induced SL model and 12 patients with SL were collected and their fibroblasts were isolated. These lymphedema-associated fibroblasts (LAFs) were cultured in a collagen I-poly-D-lysine 3-dimensional hydrogel to mimic skin conditions. Fibroblasts from nonlymphedema skin were used as negative control and transforming growth factor β (TGF-β)-stimulated fibroblasts were used to recreate profibrotic myofibroblasts. Quantitative immunocytofluorescence confocal microscopy analysis and invasion functional assays were performed in all subpopulations and statistically compared. In contrast to normal skin fibroblasts, LAFs exhibit α-smooth muscle actin-positive stress fibers and a reduced number of tight junctions in 3-dimensional hydrogel conditions. The switch from normal E-cadherin high phenotype to an N-cadherin high -E-cadherin low morphology suggests epithelial-to-mesenchymal transition for expansion and proliferation. This pathologic behavior of LAF was confirmed by live cell imaging analysis of invasion assays. The significant activation of markers of the TGF-β receptor 2-Smad pathway and collagen synthesis (HSP-47 [heat shock protein 47]) in LAFs supports epithelial-to-mesenchymal transition phenotypic changes and previous findings relating to TGF-β1 and fibrosis with lymphedema. A characteristic SL myofibroblast subpopulation was identified and translationally related to fibrosis and TGF-β1-associated stage progression. This SL-related subpopulation was termed LAFs. A comprehensive stage-related characterization is required to validate LAFs as a reliable biomarker for SL disease progression. The authors identify a cellular effector for fibrosis and stage progression of secondary lymphedema as a possible biomarker for surgical indication and therapy response.

Overcoming lung cancer immunotherapy resistance by combining nontoxic variants of IL-12 and IL-2.

Engineered cytokine-based approaches for immunotherapy of cancer are poised to enter the clinic, with IL-12 being at the forefront. However, little is known about potential mechanisms of resistance to cytokine therapies. We found that orthotopic murine lung tumors were resistant to systemically delivered IL-12 fused to murine serum albumin (MSA, IL12-MSA) because of low IL-12 receptor (IL-12R) expression on tumor-reactive CD8+ T cells. IL2-MSA increased binding of IL12-MSA by tumor-reactive CD8+ T cells, and combined administration of IL12-MSA and IL2-MSA led to enhanced tumor-reactive CD8+ T cell effector differentiation, decreased numbers of tumor-infiltrating CD4+ regulatory T cells, and increased survival of lung tumor-bearing mice. Predictably, the combination of IL-2 and IL-12 at therapeutic doses led to significant dose-limiting toxicity. Administering IL-12 and IL-2 analogs with preferential binding to cells expressing Il12rb1 and CD25, respectively, led to a significant extension of survival in mice with lung tumors while abrogating dose-limiting toxicity. These findings suggest that IL-12 and IL-2 represent a rational approach to combination cytokine therapy whose dose-limiting toxicity can be overcome with engineered cytokine variants.

Single-cell analysis of the CD8+ T-cell compartment in multiple myeloma reveals disease specific changes are chiefly restricted to a CD69- subset suggesting potent cytotoxic effectors exist within the tumor bed.

Multiple myeloma (MM) is an incurable disease of the bone marrow (BM) characterized by the uncontrolled proliferation of neoplastic plasma cells. While CD8+ T cells have an established role in disease control, few studies have focused on these cells within the MM tumor microenvironment (TME). We analyzed CD8+ T cells in the BM and peripheral blood (PB) of untreated patients with MM and non-myeloma controls using flow cytometry, mass cytometry and single-cell RNA sequencing, using several novel bioinformatics workflows. Inter-tissue differences were most evident in the differential expression of Granzymes B and K, which were strongly associated with two distinct subsets of CD8+ T cells delineated by the expression of CD69, accounting for roughly 50% of BM-CD8+ T cells of all assessed cohorts. While few differences were observable between health and disease in the BM-restricted CD8CD69+ T-cell subset, the CD8+CD69- T-cell subset in the BM of untreated MM patients demonstrated increased representation of highly differentiated effector cells and evident compositional parallels between the PB, absent in age-matched controls, where a marked reduction of effector cells was observed. We demonstrate the transcriptional signature of BM-CD8+ T cells from patients with MM more closely resembles TCR-activated CD8+ T cells from age-matched controls than their resting counterparts.

Reciprocal transmission of activating and inhibitory signals and cell fate in regenerating T cells

The ability of activated progenitor Tcells to self-renew while producing differentiated effector cell descendants may underlie immunological memory and persistent responses to ongoing infection. The nature of stem-like Tcells responding to cancer and during treatment with immunotherapy is not clear. The subcellular organization of dividing progenitor CD8+ Tcells from mice challenged with syngeneic tumors is examined here. Three-dimensional microscopy reveals an activating hub composed of polarized CD3, CD28, and phosphatidylinositol 3-kinase (PI3K) activity at the putative immunological synapse with an inhibitory hub composed of polarized PD-1 and CD73 at the opposite pole of mitotic blasts. Progenitor Tcells from untreated and inhibitory checkpoint blockade-treated mice yield a differentiated TCF1- daughter cell, which inherits the PI3K activation hub, alongside a discordantly fated, self-renewing TCF1+ sister cell. Dynamic organization of opposite activating and inhibitory signaling poles in mitotic lymphocytes may account for the enigmatic durability of specific immunity.

A Dual-Antioxidative Coating on Transmucosal Component of Implant to Repair Connective Tissue Barrier for Treatment of Peri-Implantitis.

Since the microgap between implant and surrounding connective tissue creates the pass for pathogen invasion, sustained pathological stimuli can accelerate macrophage-mediated inflammation, therefore affecting peri-implant tissue regeneration and aggravate peri-implantitis. As the transmucosal component of implant, the abutment therefore needs to be biofunctionalized to repair the gingival barrier. Here, a mussel-bioinspired implant abutment coating containing tannic acid (TA), cerium and minocycline (TA-Ce-Mino) is reported. TA provides pyrogallol and catechol groups to promote cell adherence. Besides, Ce3+ /Ce4+ conversion exhibits enzyme-mimetic activity to remove reactive oxygen species while generating O2 , therefore promoting anti-inflammatory M2 macrophage polarization to help create a regenerative environment. Minocycline isinvolved on the TA surface to create local drug storage for responsiveantibiosis. Moreover, the underlying therapeutic mechanism is revealed whereby the coating exhibits exogenous antioxidation from the inherent properties of Ce and TA and endogenous antioxidation through mitochondrial homeostasis maintenance and antioxidases promotion. In addition, it stimulates integrin to activate PI3K/Akt and RhoA/ROCK pathways to enhance VEGF-mediated angiogenesis and tissue regeneration. Combining the antibiosis and multidimensional orchestration, TA-Ce-Mino repairs soft tissue barriers and effector cell differentiation, thereby isolating the immune microenvironment from pathogen invasion. Consequently, this study provides critical insight into the design and biological mechanism of abutment surface modification to prevent peri-implantitis.

Distribution modeling quantifies collective TH cell decision circuits in chronic inflammation.

Immune responses are tightly regulated by a diverse set of interacting immune cell populations. Alongside decision-making processes such as differentiation into specific effector cell types, immune cells initiate proliferation at the beginning of an inflammation, forming two layers of complexity. Here, we developed a general mathematical framework for the data-driven analysis of collective immune cell dynamics. We identified qualitative and quantitative properties of generic network motifs, and we specified differentiation dynamics by analysis of kinetic transcriptome data. Furthermore, we derived a specific, data-driven mathematical model for T helper 1 versus T follicular helper cell-fate decision dynamics in acute and chronic lymphocytic choriomeningitis virus infections in mice. The model recapitulates important dynamical properties without model fitting and solely by using measured response-time distributions. Model simulations predict different windows of opportunity for perturbation in acute and chronic infection scenarios, with potential implications for optimization of targeted immunotherapy.

PD-1 blockade increases the self-renewal of stem-like CD8 T cells to compensate for their accelerated differentiation into effectors.

PD-1+TCF-1+ stem-like CD8 T cells act as critical resource cells for maintaining T cell immunity in chronic viral infections and cancer. In addition, they provide the proliferative burst of effector CD8 T cells after programmed death protein 1 (PD-1)-directed immunotherapy. However, it is not known whether checkpoint blockade diminishes the number of these stem-like progenitor cells as effector cell differentiation increases. To investigate this, we used the mouse model of chronic lymphocytic choriomeningitis virus (LCMV) infection. Treatment of chronically infected mice with either αPD-1 or αPD-L1 antibody not only increased effector cell differentiation from the virus-specific stem-like CD8 T cells but also increased their proliferation so their numbers were maintained. The increased self-renewal of LCMV-specific stem-like CD8 T cells was mTOR dependent. We used microscopy to understand the division of these progenitor cells and found that after PD-1 blockade, an individual dividing cell could give rise to a differentiated TCF-1- daughter cell alongside a self-renewing TCF-1+ sister cell. This asymmetric division helped to preserve the number of stem-like cells. Moreover, we found that the PD-1+TCF-1+ stem-like CD8 T cells retained their transcriptional program and their in vivo functionality in terms of responding to viral infection and to repeat PD-1 blockade. Together, our results demonstrate that PD-1 blockade does not deplete the stem-like population despite increasing effector differentiation. These findings have implications for PD-1-directed immunotherapy in humans.

Exogenous catalase treatment enhances CD8+ T cell functionality and hinders T cell exhaustion

Abstract ROS are small short-lived oxygen-containing molecules which are highly chemically reactive and involved in the regulation of biological processes like T cell activation and proliferation. The tumor microenvironment (TME) is a metabolically hostile environment with a deficiency in nutrients like glucose and glutamine, accumulation of tumor-driven metabolic waste, and extreme hypoxia. Hypoxia results in impaired mitochondrial function and generation of excess levels of ROS, which have been known to promote T cell exhaustion. Here, we investigated how exogenous treatment of antioxidant catalase altered CD8+ T cell effector responses and T cell exhaustion using OT-I TCR transgenic mice. During CD8+ T cell effector differentiation in vitro by stimulation with cognate antigen followed by culture with IL-2, addition of catalase significantly enhanced T cell activation and effector differentiation. Catalase-treated effector cells had higher expression of critical activation markers including CD69 and CD25, increased expression of the stemness marker TCF-1, and enhanced secretion of effector cytokines IFNγ and TNFα. During induction of T cell exhaustion in vitro by co-culture with B16 melanoma expressing ovalbumin (B16-Ova), catalase-treated OT-I T cells had significantly increased cytotoxic activity, enhanced expression of CD25 and lower co-expression of PD-1 and TIM-3 relative to non-treated OT-I T cells. Our findings uncover a new role for catalase in altering the fate of CD8+ effector T cells and potentially a new therapeutic tool for managing T cell exhaustion. NIH (R01 CA212605)

Stem-like CD4 T differentiation controls CD8 T cell immunity or tolerance in cancer

Abstract In this work we wanted to understand how CD4 T cell differentiation shapes the CD8 T cell response in cancer. We identified a population of tumor specific CD4 T cells that maintain an activated, undifferentiated phenotype throughout the cancer response. These CD4 T cells were the dominant population within tumor draining lymph nodes (TDLNs), characterized by high expression of TCF1 and little to no expression of other lineage defining transcription factors. Tumor specific TCF1+ CD4s exhibited functional stem-like properties, as they self-renewed and differentiated almost exclusively into Tregs in tumor bearing mice. These cells, however, were not limited to Treg differentiation, as sorted TCF1+ CD4s from a 5-week tumor response expanded and gave rise to TH1 and TFH effectors in response to LCMV Armstrong infection. Interestingly, we also found a similar population of activated PD1+ TCF1+ CD4s with stem-like capabilities infiltrating various human tumors, indicating this phenotype of CD4s is comparable in human cancer and mouse models. Importantly, the choice of lineage differentiation of TCF1+ CD4s regulated the quality of the CD8 T cell anti-tumor response. When Tregs were selectively depleted, TCF1+ CD4s differentiated into TH1s, which enhanced tumor specific CD8 T cell effector differentiation in both tumor and TDLNs, resulting in reduced tumor burden. Using a bone marrow chimeric CRISPR-Cas9 approach, we found that IFNg from TH1s was intrinsically required for CD8 stem to effector differentiation within TDLNs, promoting an improved anti-tumor response. Overall, this work shows that CD4 differentiation dictates tolerance or immunity in cancer by regulating the phenotype and magnitude of the effector CD8 T cell response.

Virus-infected mast cells activate virus-specific CD8+ T cells.

Efficient anti-viral responses of CD8+ T cells require signals that promote their effector cell differentiation, that are mainly provided by dendritic cells (DCs). Mast cells (MCs) are key drivers of DC maturation, but also influence their migration and antigen presenting properties and therefore indirectly mediate CD8+ T cell activation. MCs initiate innate immune responses at pathogen entry sites, promote the development of adaptive immune responses after infection, and release mediators including chemokines that recruit and activate immune cells including T cells during viral infections. However, whether MCs can directly activate virus-specific CD8+ T cells remains largely unknown. Here, we used an in vitro viral infection model with lymphocytic choriomeningitis virus (LCMV)-infected MCs or DCs co-cultured with either LCMV-specific CD8+ T cells or with WT (unspecific) CD8+ T cells. Similar to LCMV-infected DCs, LCMV-infected MCs clustered with virus-specific CD8+ T cells and induced their activation and production of antiviral cytokines. In addition, the co-stimulatory molecules CD86 and OX40L, but not CD80, were upregulated on MCs and an increased production of IL-6 and type I interferons after LCMV infection was shown. Our findings suggest that MCs can promote CD8+ T cell activation during viral infections. MC-mediated CD8+ T cell activation might be especially important within infected tissues where direct cellular interaction can take place. A better understanding of anti-viral functions of MCs may help developing new strategies to better treat viral infections.

Translation inhibitor PDCD4 promotes CD8+ T cell proliferation during antiviral response

Abstract CD8+ T cell clonal expansion is critical for controlling intracellular infections and tumors. Thus, unravelling the mechanisms that regulate CD8+ T cell proliferation are imperative to improve vaccine design and immunotherapy. However, the molecular mechanisms that govern CD8+ T cell proliferation are still not fully understood. PDCD4 (Programmed cell death 4) was shown to inhibit translation by sequestering mRNA helicase eIF4A, which leads to translation inhibition of genes involved in cell proliferation. Despite the well-characterized anti-proliferative role of PDCD4, our studies suggest that PDCD4 promotes CD8+ T cell proliferation during the expansion phase of acute LCMV infection. We find that PDCD4 over-expressed Ag-specific CD8+ T cells have higher proliferation rate which leads to increased cell number compared to control Ag-specific CD8+ T cells. Consistent with the over-expression results, PDCD4 knocking-down Ag-specific CD8+ T cells undergo less cell proliferation, resulting in reduced clonal expansion compared to controls. Interestingly, contrary to the paradigm that increased proliferation generates more short-lived effector cells, CD8+ T cell proliferation mediated by PDCD4 does not skew the differentiation of short-lived and memory precursor effector cells. This PDCD4 mediated CD8+ T cell proliferation is also confirmed by over-expression of a constitutively active form of PDCD4 which resists degradation by CD8+ T cell endogenous ubiquitin pathway. In conclusion, our work has identified a novel pro-proliferative role of PDCD4 during CD8+ T cell response. Supported by grants from NIH (R01 AI139675)

Dominant interfering CARD11 variants disrupt JNK signaling in T cells and impaired CARD11-JNK signaling increases expression of GATA3

Abstract Although prior research implicated c-Jun N-terminal kinase (JNK) in helper CD4 +T cell differentiation, mechanisms governing JNK signaling and function in human lymphocytes remain nebulous. CARD11 is a lymphocyte-specific scaffold protein connecting antigen receptor (AgR) engagement to transcriptional programs necessary for effector cell survival, proliferation, and differentiation. In addition to NF-κB, CARD11 is also required for AgR-induced mTORC1 and JNK2 signaling. We sought to define the impact of dominant interfering (DI) CARD11 variants on JNK signaling and elucidate transcriptomic changes governed by CARD11-dependent JNK activation in T cells. We transfected WT and CARD11 knockout (KO) Jurkat T cells with plasmids expressing WT or DI CARD11 variants to assess effects on CARD11-dependent JNK signaling and performed RNA sequencing on mitogen-activated WT and CARD11 KO Jurkat T cells ± JNK inhibition. Our results revealed that AgR-dependent JNK1 andJNK2 activation are CARD11-dependent. Additionally, heterozygous DI CARD11 mutations derived from patients with CARD11-associated atopy with dominant interference of NF-κB signaling (CADINS) disease disrupted AgR-dependent JNK1/2 phosphorylation, c-Jun accumulation, and AP-1 transcriptional activity with variable potency, mirroring the extent of impaired NF-κB activation. Intriguingly, JNK inhibition in Jurkat and primary CD4 +T cells enhanced AgR-induced expression of GATA3, the master transcriptional regulator of Th2 cell differentiation. Our novel findings suggest that defects in CARD11-dependent JNK signaling in CD4 +T cells may contribute to severe allergic disease noted in CADINS patients, unveiling a new potential therapeutic target. Supported by funding from the Jeffrey Modell Specific Defect Research Program (ALS) and the Henry M. Jackson Foundation for the Advancement of Military Medicine (BMB).

The possible role of Wnt/β-catenin signalling in vitiligo treatment.

Vitiligo is a common chronic skin disease which has an adverse impact on patients' life. Its pathogenesis is complex, involving autoimmunity and oxidative stress (OS). Autoimmunity leads to the loss of epidermal melanocytes and the formation of the depigmented patches of the disease. Treatment of vitiligo should control the exaggerated immune response to arrest the progress of active disease, and then promote melanocytes to repigmentation. Wnt/β-catenin signalling pathway has been of recent interest in vitiligo. Wnt/β-catenin signalling pathway is downregulated in vitiligo. Upregulation of Wnt/β-catenin signalling possibly control vitiligo autoimmune response by protecting melanocyte from OS damage, inhibiting CD8+ T cell effector cell differentiation and enhancing Treg. Wnt/β-catenin signalling plays a critical role in the melanocyte regeneration by driving the differentiation of melanocyte stem cells (McSCs) into melanocytes. Promoting Wnt/β-catenin signalling can not only arrest the progress of active disease of vitiligo but also promote repigmentation. Some of the main effective therapies for vitiligo are likely to work by activating Wnt/β-catenin signalling. Agents that can enhance the effect of Wnt/β-catenin signalling may become potential candidates for the development of new drugs for vitiligo treatment.

NK-like CD8+ γδ T cells are expanded in persistent Mycobacterium tuberculosis infection.

The response of gamma delta (γδ) T cells in the acute versus chronic phases of the same infection is unclear. How γδ T cells function in acute Mycobacterium tuberculosis (Mtb) infection is well characterized, but their response during persistent Mtb infection is not well understood, even though most infections with Mtb manifest as a chronic, clinically asymptomatic state. Here, we analyze peripheral blood γδ T cells from a South African adolescent cohort and show that a unique CD8+ γδ T cell subset with features of "memory inflation" expands in chronic Mtb infection. These cells are hyporesponsive to T cell receptor (TCR)-mediated signaling but, like NK cells, can mount robust CD16-mediated cytotoxic responses. These CD8+ γδ T cells comprise a highly focused TCR repertoire, with clonotypes that are Mycobacterium specific but not phosphoantigen reactive. Using multiparametric single-cell pseudo-time trajectory analysis, we identified the differentiation paths that these CD8+ γδ T cells follow to develop into effectors in this infection state. Last, we found that circulating CD8+ γδ T cells also expand in other chronic inflammatory conditions, including cardiovascular disease and cancer, suggesting that persistent antigenic exposure may drive similar γδ T cell effector programs and differentiation fates.

Themis suppresses the effector function of CD8+ T cells in acute viral infection.

CD8+ T cells play a central role in antiviral immune responses. Upon infection, naive CD8+ T cells differentiate into effector cells to eliminate virus-infected cells, and some of these effector cells further differentiate into memory cells to provide long-term protection after infection is resolved. Although extensively investigated, the underlying mechanisms of CD8+ T-cell differentiation remain incompletely understood. Themis is a T-cell-specific protein that plays critical roles in T-cell development. Recent studies using Themis T-cell conditional knockout mice also demonstrated that Themis is required to promote mature CD8+ T-cell homeostasis, cytokine responsiveness, and antibacterial responses. In this study, we used LCMV Armstrong infection as a probe to explore the role of Themis in viral infection. We found that preexisting CD8+ T-cell homeostasis defects and cytokine hyporesponsiveness do not impair viral clearance in Themis T-cell conditional knockout mice. Further analyses showed that in the primary immune response, Themis deficiency promoted the differentiation of CD8+ effector cells and increased their TNF and IFNγ production. Moreover, Themis deficiency impaired memory precursor cell (MPEC) differentiation but promoted short-lived effector cell (SLEC) differentiation. Themis deficiency also enhanced effector cytokine production in memory CD8+ T cells while impairing central memory CD8+ T-cell formation. Mechanistically, we found that Themis mediates PD-1 expression and its signaling in effector CD8+ T cells, which explains the elevated cytokine production in these cells when Themis is disrupted.

CLASH of the Titans: How CAR-T Cells Can Triumph Over Tumors.

CLASH of the Titans: How CAR-T Cells Can Triumph Over Tumors.

Regulatory effects of IRF4 on immune cells in the tumor microenvironment.

The tumor microenvironment (TME) is implicated in tumorigenesis, chemoresistance, immunotherapy failure and tumor recurrence. Multiple immunosuppressive cells and soluble secreted cytokines together drive and accelerate TME disorders, T cell immunodeficiency and tumor growth. Thus, it is essential to comprehensively understand the TME status, immune cells involved and key transcriptional factors, and extend this knowledge to therapies that target dysfunctional T cells in the TME. Interferon regulatory factor 4 (IRF4) is a unique IRF family member that is not regulated by interferons, instead, is mainly induced upon T-cell receptor signaling, Toll-like receptors and tumor necrosis factor receptors. IRF4 is largely restricted to immune cells and plays critical roles in the differentiation and function of effector cells and immunosuppressive cells, particularly during clonal expansion and the effector function of T cells. However, in a specific biological context, it is also involved in the transcriptional process of T cell exhaustion with its binding partners. Given the multiple effects of IRF4 on immune cells, especially T cells, manipulating IRF4 may be an important therapeutic target for reversing T cell exhaustion and TME disorders, thus promoting anti-tumor immunity. This study reviews the regulatory effects of IRF4 on various immune cells in the TME, and reveals its potential mechanisms, providing a novel direction for clinical immune intervention.

TRAF3: Guardian of T lymphocyte functions.

Tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) is an adapter protein with many context-specific functions. Early studies of lymphocyte TRAF3 hinted at TRAF3's importance for T cell function, but elucidation of specific mechanisms was delayed by early lethality of globally TRAF3-/- mice. Development of a conditional TRAF3-deficient mouse enabled important descriptive and mechanistic insights into how TRAF3 promotes optimal T cell function. Signaling through the T cell antigen receptor (TCR) fails to induce normal proliferation and survival in TRAF3 -/- T cells, and TCR-activated cells in vitro and in vivo have deficient cytokine production. These defects can be traced to incorrect localization and function of negative regulatory phosphatases acting at different parts of the signaling cascade, as can dysregulated effector responses and memory T cell homeostasis in vivo and an enlarged regulatory T cell (Treg) compartment. The important regulatory activity of TRAF3 is also evident at members of the TNFR superfamily and cytokine receptors. Here, we review significant advances in mechanistic understanding of how TRAF3 regulates T cell differentiation and function, through modulation of signaling through the TCR, costimulatory receptors, and cytokine receptors. Finally, we briefly discuss the recent identification of families carrying single allele loss-of-function mutations in TRAF3, and compare the findings in their T cells with the T cell defects identified in mice whose T cells completely lack T cell TRAF3. Together, the body of work describing TRAF3-mediated regulation of T cell effector function and differentiation frame TRAF3 as an important modulator of T cell signal integration.

Tumor infiltrating T cell states and checkpoint inhibitor expression in hepatic and pancreatic malignancies.

Hepato-pancreatico-biliary (HPB) malignancies are difficult-to-treat and continue to to have a high mortality and significant therapeutic resistance to standard therapies. Immune oncology (IO) therapies have demonstrated efficacy in several solid malignancies when combined with chemotherapy, whereas response rates in pancreatic ductal adenocarcinoma (PDA) are poor. While promising in hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), there remains an unmet need to fully leverage IO therapies to treat HPB tumors. We therefore defined T cell subsets in the tumor microenvironment of HPB patients utilizing a novel, multiparameter flow cytometry and bioinformatics analysis. Our findings quantify the T cell phenotypic states in relation to checkpoint receptor expression. We demonstrate the presence of CD103+ tissue resident memory T cells (TRM), CCR7+ central memory T cells, and CD57+ terminally differentiated effector cells across all HPB cancers, while the anti-tumor function was dampened by expression of multiple co-inhibitory checkpoint receptors. Terminally exhausted T cells lacking co-stimulatory receptors were more prevalent in PDA, whereas partially exhausted T cells expressing both co-inhibitory and co-stimulatory receptors were most prevalent in HCC, especially in early stage. HCC patients had significantly higher TRM with a phenotype that could confer restored activation in response to immune checkpoint therapies. Further, we found a lack of robust alteration in T cell activation state or checkpoint expression in response to chemotherapy in PDA patients. These results support that HCC patients might benefit most from combined checkpoint therapies, whereas efforts other than cytotoxic chemotherapy will likely be necessary to increase overall T cell activation in CCA and PDA for future clinical development.

P577 A Phase 1b Study to Evaluate Safety, Tolerability, Pharmacokinetics and Clinical Efficacy of the Nucleotide-binding oligomerization domain, Leucine rich Repeat containing X1 (NLRX1) agonist NX-13 in Ulcerative Colitis

Abstract Background NLRX1 is a mitochondrial membrane protein whose activation reduces oxidative stress and decreases effector cell differentiation and cytokine release. NX-13 is a first-in-class, orally active, gut selective NLRX1 agonist with low systemic exposure. In preclinical studies of IBD, NX-13 effectively reduced inflammatory responses and disease severity. A phase 1a study (healthy subjects) showed NX-13 to be well tolerated with low systemic drug exposure suggesting a gut-selective drug delivery. We report the results of a phase 1b study in patients with Ulcerative colitis (UC) on the safety, target engagement and clinical efficacy of NX-13. Methods In this double-blind trial, 36 patients with active UC (Total Mayo Score [MCS] 4-10; Mayo endoscopic subscore [MES] 2-3) were randomly assigned to NX-13 250mg Immediate Release (IR), 500mg IR, 500mg Modified Release (MR) or Placebo to be taken QD for 4 weeks (safety visit at week 5). Biologic exposed patients, stable 5’ASAs dose and corticosteroids (oral ≤20mg/day prednisone or equivalent) were permitted. IV or topical corticosteroids use was prohibited. Primary endpoints were safety and pharmacokinetic (PK) analysis. The study was not powered for clinical efficacy, however MCS, histopathologic Geboes score, and NLRX1, cytokine, and gene expression were obtained at baseline and day 28 in exploratory analyses (Table 1). Results During the 5-week observation period, no serious adverse events (AEs) were reported. All AEs were classified as mild or moderate and were most common in the 500mg MR group. One patient was withdrawn before week 5 due to a flare of UC. IR dose plasma PK levels peaked at 1hour, while the MR dose was absorbed later and maintained a low exposure longer. Qualitative immunohistochemical analysis showed target engagement as indicated by increase of NLRX1 at all doses. Symptomatic efficacy was seen in 8/11 patients in the 250mg group with a PRO (RB+SF) score of 0 at week 4. The decrease in MCS was 2.1-3.4 in the NX-13 arms vs 1 point with placebo (Fig 1A) while clinical response rates ranged from 27-72% amongst the active arms with no placebo responders, though no dose-response relationship was observed (Fig 1B). Endoscopic response ranged from 27-40% (Fig 1C), with 5/32 dosed patients being in endoscopic remission. Histologic remission largely paralleled endoscopic response and cytokine and mRNA levels support target engagement. Conclusion In patients with active UC, NX-13 was well-tolerated and target engagement was achieved. The exploratory efficacy endpoints indicated rapid clinical, endoscopic, and histologic improvement at week 4, relative to placebo. This novel mechanism of action will be further evaluated in a phase 2 study.