Anti-regulatory T cells

State-Of-The-Art Advancements on Cancer Vaccines and Biomarkers

The origins of cancer vaccines date back to the 1800s. Since then, there have been significant efforts to generate vaccines against solid and hematologic malignancies using a variety of platforms. To date, these efforts have generally been met with minimal success. However, in the era of improved methods and technological advancements, supported by compelling preclinical and clinical data, a wave of renewed interest in the field offers the promise of discovering field-changing paradigms in the management of established and resected disease using cancer vaccines. These include novel approaches to personalized neoantigen vaccine development, as well as innovative immune-modulatory vaccines (IMVs) that facilitate activation of antiregulatory T cells to limit immunosuppression caused by regulatory immune cells. This article will introduce some of the limitations that have affected cancer vaccine development over the past several decades, followed by an introduction to the latest advancements in neoantigen vaccine and IMV therapy, and then conclude with a discussion of some of the newest technologies and progress that are occurring across the cancer vaccine space. Cancer vaccines are among the most promising frontiers for breakthrough innovations and strategies poised to make a measurable impact in the ongoing fight against cancer.

Arginase-1 specific CD8+ T cells react toward malignant and regulatory myeloid cells

Arginase-1 (Arg1) is expressed by regulatory myeloid cells in the tumor microenvironment (TME), where they play a pro-tumorigenic and T-cell suppressive role. Arg1-specific CD4+ and CD8+ memory T cells have been observed in both healthy individuals and cancer patients. However, while the function of anti-regulatory Arg1-specific CD4+ T cells has been characterized, our knowledge of CD8+ Arg1-specific T cells is only scarce. In the current study, we describe the immune-modulatory capabilities of CD8+ Arg1-specific T cells. We generated CD8+ Arg1-specific T cell clones to target Arg1-expressing myeloid cells. Our results demonstrate that these T cells recognize both malignant and nonmalignant regulatory myeloid cells in an Arg1-expression-dependent manner. Notably, Arg1-specific CD8+ T cells possess cytolytic effector capabilities. Immune modulatory vaccines (IMVs) represent a novel treatment modality for cancer. The activation of Arg1-specific CD8+ T cells through Arg1-based IMVs can contribute to the modulatory effects of this treatment strategy.

Pre-existing TGF-β-specific T-cell immunity in patients with pancreatic cancer predicts survival after checkpoint inhibitors combined with radiotherapy

BACKGROUND

Circulating transforming growth factor-β (TGF-β)-specific T cells that recognize TGF-β-expressing immune regulatory cells have been described in patients with cancer. TGF-β-derived peptide vaccination modulates the tumor microenvironment and has shown clinical effects in animal models of pancreatic cancer (PC). TGF-β-expressing regulatory cells are especially elevated in PC and may prevent the clinical response to immune checkpoint inhibitors (ICIs). Thus, in the present study we investigated the significance of TGF-β-specific T-cell immunity in patients with PC treated with ICI combined with radiotherapy in a randomized phase 2 study (CheckPAC).

METHODS

Immune responses to a TGF-β-derived epitope entitled TGF-β-15 as well as epitopes from Clostridium tetani (tetanus) and influenza were measured in peripheral blood mononuclear cells (PBMCs) with interferon-ɣ enzyme-linked immunospot assays. PBMCs were isolated before and after treatment. Correlations between immune response data and clinical data were evaluated with parametric and non-parametric statistical methods. Survival was analyzed with univariate and multivariate Cox-regression. TGF-β-15 specific T cells were isolated and expanded and examined for recognition of autologous regulatory immune cells by flow cytometry.

RESULTS

PBMCs from 32 patients were analyzed for immune responses to the TGF-β-derived epitope entitled TGF-β-15. Patients with a strong TGF-β-specific immune response at treatment initiation had longer progression-free and overall survival, compared with patients with a weak or no TGF-β-specific immune response. This remained significant in multivariate analysis. Patients with weak and strong TGF-β-specific responses displayed similar responses towards viral antigens. Furthermore, we show that TGF-β-specific T cells from a clinical responder specifically reacted to and lysed autologous, regulatory immune cells. Finally, mimicking a TGF-β-15 vaccination, we showed that repeated stimulations with the TGF-β-15 epitope in vitro enhanced the immune response to TGF-β-15.

CONCLUSION

A strong TGF-β-15 specific immune response was associated with clinical benefit and improved survival after ICI/radiotherapy for patients with PC. Importantly, the lack of TGF-β-specific T cells in some patients was not caused by a general immune dysfunction. TGF-β-specific T cells recognized regulatory immune cells and could be introduced in vitro in patients without spontaneous responses. Taken together, our data suggest that combining TGF-β-based vaccination with ICI/radiotherapy will be beneficial for patients with PC.

An arginase1- and PD-L1-derived peptide-based vaccine for myeloproliferative neoplasms: A first-in-man clinical trial

Introduction

Arginase-1 (ARG1) and Programed death ligand-1 (PD-L1) play a vital role in immunosuppression in myeloproliferative neoplasms (MPNs) and directly inhibit T-cell activation and proliferation. We previously identified spontaneous T-cell responses towards PD-L1 and ARG1 derived peptide epitopes in patients with MPNs. In the present First-in-Man study we tested dual vaccinations of ARG1- derived and PD-L1-derived peptides, combined with Montanide ISA-51 as adjuvant, in patients with Janus Kinase 2 (JAK2) V617F-mutated MPN.

Methods

Safety and efficacy of vaccination with ARG1- derived and PD-L1-derived peptides with montanide as an adjuvant was tested in 9 patients with MPN The primary end point was safety and toxicity evaluation. The secondary end point was assessment of the immune response to the vaccination epitope (www.clinicaltrials.gov identifier NCT04051307).

Results

The study included 9 patients with JAK2-mutant MPN of which 8 received all 24 planned vaccines within a 9-month treatment period. Patients reported only grade 1 and 2 vaccine related adverse events. No alterations in peripheral blood counts were identified, and serial measurements of the JAK2V617F allelic burden showed that none of the patients achieved a molecular response during the treatment period. The vaccines induced strong immune responses against both ARG1 and PD-L1- derived epitopes in the peripheral blood of all patients, and vaccine-specific skin-infiltrating lymphocytes from 5/6 patients could be expanded in vitro after a delayed-type hypersensitivity test. In two patients we also detected both ARG1- and PD-L1-specific T cells in bone marrow samples at the end of trial. Intracellular cytokine staining revealed IFNγ and TNFγ producing CD4+- and CD8+- T cells specific against both vaccine epitopes. Throughout the study, the peripheral CD8/CD4 ratio increased significantly, and the CD8+ TEMRA subpopulation was enlarged. We also identified a significant decrease in PD-L1 mRNA expression in CD14+ myeloid cells in the peripheral blood in all treated patients and a decrease in ARG1 mRNA expression in bone marrow of 6 out of 7 evaluated patients.

Conclusion

Overall, the ARG1- and PD-L1-derived vaccines were safe and tolerable and induced strong T-cell responses in all patients. These results warrant further studies of the vaccine in other settings or in combination with additional immune-activating treatments.

A Brief Overview of Cancer Vaccines

ABSTRACT

Vaccine strategies for cancer differ from infectious disease in focusing mainly on clearing rather than preventing disease. Here we survey general vaccine strategies and combination therapy concepts being investigated for cancer treatment, with a focus on tumor antigens rather than cancer-inducing viruses or microorganisms. Many tumor antigens are "altered-self" and tend to arouse weaker immune responses than "foreign" antigens expressed by infectious agents. Further, unlike an infectious disease patient, a cancer patient's immune system is damaged, suppressed, or senescent and mainly tolerant of their disease. Thus, vaccine efficacy in a cancer patient will rely upon adjuvant or combination treatments that correct the inflammatory tumor microenvironment and degrade tumoral immunosuppression that dominates patient immunity. This brief overview is aimed at new researchers in cancer immunology seeking an overview of vaccine concepts to eradicate malignancy by provoking a selective immune attack.

TGFβ-derived immune modulatory vaccine: targeting the immunosuppressive and fibrotic tumor microenvironment in a murine model of pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is associated with very poor survival, making it the third and fourth leading cause of all cancer-related deaths in the USA and European Union, respectively. The tumor microenvironment (TME) in PDAC is highly immunosuppressive and desmoplastic, which could explain the limited therapeutic effect of immunotherapy in PDAC. One of the key molecules that contributes to immunosuppression and fibrosis is transforming growth factor-β (TGFβ). The aim of this study was to target the immunosuppressive and fibrotic TME in PDAC using a novel immune modulatory vaccine with TGFβ-derived peptides in a murine model of pancreatic cancer.

METHODS

C57BL/6 mice were subcutaneously inoculated with Pan02 PDAC cells. Mice were treated with TGFβ1-derived peptides (major histocompatibility complex (MHC)-I and MHC-II-restricted) adjuvanted with Montanide ISA 51VG. The presence of treatment-induced TGFβ-specific T cells was assessed by ELISpot (enzyme-linked immunospot). Changes in the immune infiltration and gene expression profile in tumor samples were characterized by flow cytometry, reverse transcription-quantitative PCR (RT-qPCR), and bulk RNA sequencing.

RESULTS

Treatment with immunogenic TGFβ-derived peptides was safe and controlled tumor growth in Pan02 tumor-bearing mice. Enlargement of tumor-draining lymph nodes in vaccinated mice positively correlated to the control of tumor growth. Analysis of immune infiltration and gene expression in Pan02 tumors revealed that TGFβ-derived peptide vaccine increased the infiltration of CD8⁺ T cells and the intratumoral M1/M2 macrophage ratio, it increased the expression of genes involved in immune activation and immune response to tumors, and it reduced the expression of myofibroblast-like cancer-associated fibroblast (CAF)-related genes and genes encoding fibroblast-derived collagens. Finally, we confirmed that TGFβ-derived peptide vaccine actively modulated the TME, as the ability of T cells to proliferate was restored when exposed to tumor-conditioned media from vaccinated mice compared with media from untreated mice.

CONCLUSION

This study demonstrates the antitumor activity of TGFβ-derived multipeptide vaccination in a murine tumor model of PDAC. The data suggest that the vaccine targets immunosuppression and fibrosis in the TME by polarizing the cellular composition towards a more pro-inflammatory phenotype. Our findings support the feasibility and potential of TGFβ-derived peptide vaccination as a novel immunotherapeutic approach to target immunosuppression in the TME.

Arginase-2-specific cytotoxic T cells specifically recognize functional regulatory T cells

Background

High expression of the metabolic enzyme arginase-2 (ARG2) by cancer cells, regulatory immune cells, or cells of the tumor stroma can reduce the availability of arginine (L-Arg) in the tumor microenvironment (TME). Depletion of L-Arg has detrimental consequences for T cells and leads to T-cell dysfunction and suppression of anticancer immune responses. Previous work from our group has demonstrated the presence of proinflammatory ARG2-specific CD4 T cells that inhibited tumor growth in murine models on activation with ARG2-derived peptides. In this study, we investigated the natural occurrence of ARG2-specific CD8 T cells in both healthy donors (HDs) and patients with cancer, along with their immunomodulatory capabilities in the context of the TME.

Materials and methods

A library of 15 major histocompatibility complex (MHC) class I-restricted ARG2-derived peptides were screened in HD peripheral blood mononuclear cells using interferon gamma (IFN-γ) ELISPOT. ARG2-specific CD8 T-cell responses were identified using intracellular cytokine staining and ARG2-specific CD8 T-cell cultures were established by enrichment and rapid expansion following in vitro peptide stimulation. The reactivity of the cultures toward ARG2-expressing cells, including cancer cell lines and activated regulatory T cells (Tregs), was assessed using IFN-γ ELISPOT and a chromium release assay. The Treg signature was validated based on proliferation suppression assays, flow cytometry and quantitative reverse transcription PCR (RT-qPCR). In addition, vaccinations with ARG2-derived epitopes were performed in the murine Pan02 tumor model, and induction of ARG2-specific T-cell responses was evaluated with IFN-γ ELISPOT. RNAseq and subsequent GO-term and ImmuCC analysis was performed on the tumor tissue.

Results

We describe the existence of ARG2-specific CD8⁺ T cells and demonstrate these CD8⁺ T-cell responses in both HDs and patients with cancer. ARG2-specific T cells recognize and react to an ARG2-derived peptide presented in the context of HLA-B8 and exert their cytotoxic function against cancer cells with endogenous ARG2 expression. We demonstrate that ARG2-specific T cells can specifically recognize and react to activated Tregs with high ARG2 expression. Finally, we observe tumor growth suppression and antitumorigenic immunomodulation following ARG2 vaccination in an in vivo setting.

Conclusion

These findings highlight the ability of ARG2-specific T cells to modulate the immunosuppressive TME and suggest that ARG2-based immunomodulatory vaccines may be an interesting option for cancer immunotherapy.

Tumor microenvironment antigens

The identification and characterization of tumor antigens are central objectives in developing anti-cancer immunotherapy. Traditionally, tumor-associated antigens (TAAs) are considered relatively restricted to tumor cells (i.e., overexpressed proteins in tumor cells), whereas tumor-specific antigens (TSAs) are considered unique to tumor cells. Recent studies have focused on identifying patient-specific neoantigens, which might be highly immunogenic because they are not expressed in normal tissues. The opposite strategy has emerged with the discovery of anti-regulatory T cells (anti-Tregs) that recognize and attack many cell types in the tumor microenvironment, such as regulatory immune cells, in addition to tumor cells. The term proposed in this review is "tumor microenvironment antigens" (TMAs) to describe the antigens that draw this attack. As therapeutic targets, TMAs offer several advantages that differentiate them from more traditional tumor antigens. Targeting TMAs leads not only to a direct attack on tumor cells but also to modulation of the tumor microenvironment, rendering it immunocompetent and tumor-hostile. Of note, in contrast to TAAs and TSAs, TMAs also are expressed in non-transformed cells with consistent human leukocyte antigen (HLA) expression. Inflammation often induces HLA expression in malignant cells, so that targeting TMAs could additionally affect tumors with no or very low levels of surface HLA expression. This review defines the characteristics, differences, and advantages of TMAs compared with traditional tumor antigens and discusses the use of these antigens in immune modulatory vaccines as an attractive approach to immunotherapy. Different TMAs are expressed by different cells and could be combined in anti-cancer immunotherapies to attack tumor cells directly and modulate local immune cells to create a tumor-hostile microenvironment and inhibit tumor angiogenesis. Immune modulatory vaccines offer an approach for combinatorial therapy with additional immunotherapy including checkpoint blockade, cellular therapy, or traditional cancer vaccines. These combinations would increase the number of patients who can benefit from such therapeutic measures, which all have optimal efficiency in inflamed tumors.

Autoimmune Responses in Oncology: Causes and Significance

Specific anti-tumor immune responses have proven to be pivotal in shaping tumorigenesis and tumor progression in solid cancers. These responses can also be of an autoimmune nature, and autoantibodies can sometimes be present even before the onset of clinically overt disease. Autoantibodies can be generated due to mutated gene products, aberrant expression and post-transcriptional modification of proteins, a pro-immunogenic milieu, anti-cancer treatments, cross-reactivity of tumor-specific lymphocytes, epitope spreading, and microbiota-related and genetic factors. Understanding these responses has implications for both basic and clinical immunology. Autoantibodies in solid cancers can be used for early detection of cancer as well as for biomarkers of prognosis and treatment response. High-throughput techniques such as protein microarrays make parallel detection of multiple autoantibodies for increased specificity and sensitivity feasible, affordable, and quick. Cancer immunotherapy has revolutionized cancer treatments and has made a considerable impact on reducing cancer-associated morbidity and mortality. However, immunotherapeutic interventions such as immune checkpoint inhibition can induce immune-related toxicities, which can even be life-threatening. Uncovering the reasons for treatment-induced autoimmunity can lead to fine-tuning of cancer immunotherapy approaches to evade toxic events while inducing an effective anti-tumor immune response.

Canonical Secretomes, Innate Immune Caspase-1-, 4/11-Gasdermin D Non-Canonical Secretomes and Exosomes May Contribute to Maintain Treg-Ness for Treg Immunosuppression, Tissue Repair and Modulate Anti-Tumor Immunity via ROS Pathways

We performed a transcriptomic analyses using the strategies we pioneered and made the following findings: 1) Normal lymphoid Tregs, diseased kidney Tregs, splenic Tregs from mice with injured muscle have 3, 17 and 3 specific (S-) pathways, respectively; 2) Tumor splenic Tregs share 12 pathways with tumor Tregs; tumor splenic Tregs and tumor Tregs have 11 and 8 S-pathways, respectively; 3) Normal and non-tumor disease Tregs upregulate some of novel 2641 canonical secretomic genes (SGs) with 24 pathways, and tumor Tregs upregulate canonical secretomes with 17 pathways; 4) Normal and non-tumor disease tissue Tregs upregulate some of novel 6560 exosome SGs with 56 exosome SG pathways (ESP), tumor Treg ESP are more focused than other Tregs; 5) Normal, non-tumor diseased Treg and tumor Tregs upregulate some of novel 961 innate immune caspase-1 SGs and 1223 innate immune caspase-4 SGs to fulfill their tissue/SG-specific and shared functions; 6) Most tissue Treg transcriptomes are controlled by Foxp3; and Tumor Tregs had increased Foxp3 non-collaboration genes with ROS and 17 other pathways; 7) Immune checkpoint receptor PD-1 does, but CTLA-4 does not, play significant roles in promoting Treg upregulated genes in normal and non-tumor disease tissue Tregs; and tumor splenic and tumor Tregs have certain CTLA-4-, and PD-1-, non-collaboration transcriptomic changes with innate immune dominant pathways; 8) Tumor Tregs downregulate more immunometabolic and innate immune memory (trained immunity) genes than Tregs from other groups; and 11) ROS significantly regulate Treg transcriptomes; and ROS-suppressed genes are downregulated more in tumor Tregs than Tregs from other groups. Our results have provided novel insights on the roles of Tregs in normal, injuries, regeneration, tumor conditions and some of canonical and innate immune non-canonical secretomes via ROS-regulatory mechanisms and new therapeutic targets for immunosuppression, tissue repair, cardiovascular diseases, chronic kidney disease, autoimmune diseases, transplantation, and cancers.

Therapeutic Cancer Vaccination With a Peptide Derived From the Calreticulin Exon 9 Mutations Induces Strong Cellular Immune Responses in Patients With CALR-Mutant Chronic Myeloproliferative Neoplasms

Background

The calreticulin (CALR) exon 9 mutations that are identified in 20% of patients with Philadelphia chromosome negative chronic myeloproliferative neoplasms (MPN) generate immunogenic antigens. Thus, therapeutic cancer vaccination against mutant CALR could be a new treatment modality in CALR-mutant MPN.

Methods

The safety and efficacy of vaccination with the peptide CALRLong36 derived from the CALR exon 9 mutations was tested in a phase I clinical vaccination trial with montanide as adjuvant. Ten patients with CALRmut MPN were included in the trial and received 15 vaccines over the course of one year. The primary end point was evaluation of safety and toxicity of the vaccine. Secondary endpoint was assessment of the immune response to the vaccination epitope (www.clinicaltrials.gov identifier NCT03566446).

Results

Patients had a median age of 59.5 years and a median disease duration of 6.5 years. All patients received the intended 15 vaccines, and the vaccines were deemed safe and tolerable as only two grade three AE were detected, and none of these were considered to be related to the vaccine. A decline in platelet counts relative to the platelets counts at baseline was detected during the first 100 days, however this did not translate into neither a clinical nor a molecular response in any of the patients. Immunomonitoring revealed that four of 10 patients had an in vitro interferon (IFN)-γ ELISPOT response to the CALRLong36 peptide at baseline, and four additional patients displayed a response in ELISPOT upon receiving three or more vaccines. The amplitude of the immune response increased during the entire vaccination schedule for patients with essential thrombocythemia. In contrast, the immune response in patients with primary myelofibrosis did not increase after three vaccines.

Conclusion

Therapeutic cancer vaccination with peptide vaccines derived from mutant CALR with montanide as an adjuvant, is safe and tolerable. The vaccines did not induce any clinical responses. However, the majority of patients displayed a marked T-cell response to the vaccine upon completion of the trial. This suggests that vaccines directed against mutant CALR may be used with other cancer therapeutic modalities to enhance the anti-tumor immune response.

Tissue Treg Secretomes and Transcription Factors Shared With Stem Cells Contribute to a Treg Niche to Maintain Treg-Ness With 80% Innate Immune Pathways, and Functions of Immunosuppression and Tissue Repair

We used functional -omics angles and examined transcriptomic heterogeneity in CD4⁺Foxp3⁺ regulatory T cells (Treg) from spleen (s-Treg), lymph nodes (LN-Treg), intestine (int-Treg), and visceral adipose tissue (VAT-Treg), and made significant findings: 1) Five new shared Treg genes including NIBAN, TNFRSF1b, DUSP4,VAV2, and KLRG1, and 68 new signatures are identified. Among 27 signaling pathways shared in four tissue Treg, 22 pathways are innate immune pathways (81.5%); 2) s-Treg, LN-Treg, int-Treg, and VAT-Treg have zero, 49, 45, and 116 upregulated pathways, respectively; 3) 12, 7, and 15 out of 373 CD markers are identified as specific for LN-Treg, int-Treg, and VAT-Treg, respectively, which may initiate innate immune signaling; 4) 7, 49, 44, and 79 increased cytokines out of 1176 cytokines are identified for four Treg, respectively, suggesting that Treg have much more secretory proteins/cytokines than IL-10, TGF-β, and IL-35; 5) LN-Treg, int-Treg, and VAT-Treg have 13 additional secretory functions more than s-Treg, found by analyzing 1,706 secretomic genes; 6) 2, 20, 25, and 43 increased transcription factors (TFs) out of 1,496 TFs are identified four Treg, respectively; 7) LN-Treg and int-Treg have increased pyroptosis regulators but VAT-Treg have increased apoptosis regulators; 8) 1, 15, 19, and 31 increased kinases out of 661 kinome are identified for s-Treg, LN-Treg, int-Treg, and VAT-Treg, respectively; 9) comparing with that of s-Treg, LN-Treg, int-Treg, and VAT-Treg increase activated cluster (clusters 1–3) markers; and decrease resting cluster (clusters 4–6) markers; and 10) Treg promote tissue repair by sharing secretomes and TFs AHR, ETV5, EGR1, and KLF4 with stem cells, which partially promote upregulation of all the groups of Treg genes. These results suggest that stem cell-shared master genes make tissue Treg as the first T cell type using a Treg niche to maintain their Treg-ness with 80% innate immune pathways, and triple functions of immunosuppression, tissue repair, and homeostasis maintenance. Our results have provided novel insights on the roles of innate immune pathways on Treg heterogeneity and new therapeutic targets for immunosuppression, tissue repair, cardiovascular diseases, chronic kidney disease, autoimmune diseases, transplantation, and cancers.

Cytotoxic T cells isolated from healthy donors and cancer patients kill TGFβ-expressing cancer cells in a TGFβ-dependent manner

Transforming growth factor-beta (TGFβ) is a highly potent immunosuppressive cytokine. Although TGFβ is a tumor suppressor in early/premalignant cancer lesions, the cytokine has several tumor-promoting effects in advanced cancer; abrogation of the antitumor immune response is one of the most important tumor-promoting effects. As several immunoregulatory mechanisms have recently been shown to be targets of specific T cells, we hypothesized that TGFβ is targeted by naturally occurring specific T cells and thus could be a potential target for immunomodulatory cancer vaccination. Hence, we tested healthy donor and cancer patient T cells for spontaneous T-cell responses specifically targeting 38 20-mer epitopes derived from TGFβ1. We identified numerous CD4+ and CD8+ T-cell responses against several epitopes in TGFβ. Additionally, several ex vivo responses were identified. By enriching specific T cells from different donors, we produced highly specific cultures specific to several TGFβ-derived epitopes. Cytotoxic CD8+ T-cell clones specific for both a 20-mer epitope and a 9-mer HLA-A2 restricted killed epitope peptide were pulsed in HLA-A2+ target cells and killed the HLA-A2+ cancer cell lines THP-1 and UKE-1. Additionally, stimulation of THP-1 cancer cells with cytokines that increased TGFβ expression increased the fraction of killed cells. In conclusion, we have shown that healthy donors and cancer patients harbor CD4+ and CD8+ T cells specific for TGFβ-derived epitopes and that cytotoxic T cells with specificity toward TGFβ-derived epitopes are able to recognize and kill cancer cell lines in a TGFβ-dependent manner.

A narrative review of the roles of indoleamine 2,3-dioxygenase and tryptophan-2,3-dioxygenase in liver diseases

Indoleamine 2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) are induced by several immune factors, such as interferon-γ, and act as intracellular enzymes that catabolize essential amino acid tryptophan into kynurenine and other downstream metabolites, including kynurenic acid (KYNA), xanthurenic acid (XA) and so on. IDO and TDO work as a double-edge sword. On one hand, they exert the immunomodulatory effects, especially immunosuppressive effects on the microenvironment including infections, pregnancy, tumor cells escape and transplantation. TDO plays the major role under basal conditions, while IDO comes into play under different circumstances of immune activation, thus IDO has a wider spectrum of immune regulation. On the other hand, these enzymes also inhibit pathogens such as Chlamydia pneumoniae, Staphylococcus aureus, Toxoplasma gondii and so on. Moreover, IDO regulates metabolic health through shaping intestinal microbiota. Recently, these enzymes have attracted more and more attention in liver diseases. Several studies have indicated that IDO and TDO can modulate viral hepatitis, autoimmune liver diseases, non-alcoholic fatty liver disease (NAFLD), liver cirrhosis, liver cancer even liver transplantation. Targeting them or their antagonists may provide novel therapeutic treatments for liver diseases. In this review, we will discuss the exact roles that IDO and TDO play in diverse hepatic diseases.

The Changing Landscape of Therapeutic Cancer Vaccines-Novel Platforms and Neoantigen Identification

Therapeutic cancer vaccines, an exciting development in cancer immunotherapy, share the goal of creating and amplifying tumor-specific T-cell responses, but significant obstacles still remain to their success. Here, we briefly outline the principles underlying cancer vaccine therapy with a focus on novel vaccine platforms and antigens, underscoring the renewed optimism. Numerous strategies have been investigated to overcome immunosuppressive mechanisms of the tumor microenvironment (TME) and counteract tumor escape, including improving antigen selection, refining delivery platforms, and use of combination therapies. Several new cancer vaccine platforms and antigen targets are under development. In an effort to amplify tumor-specific T-cell responses, a heterologous prime-boost antigen delivery strategy is increasingly used for virus-based vaccines. Viruses have also been engineered to express targeted antigens and immunomodulatory molecules simultaneously, to favorably modify the TME. Nanoparticle systems have shown promise as delivery vectors for cancer vaccines in preclinical research. T-win is another platform targeting both tumor cells and the TME, using peptide-based vaccines that engage and activate T cells to target immunoregulatory molecules expressed on immunosuppressive and malignant cells. With the availability of next-generation sequencing, algorithms for neoantigen selection are emerging, and several bioinformatic platforms are available to select therapeutically relevant neoantigen targets for developing personalized therapies. However, more research is needed before the use of neoepitope prediction and personalized immunotherapy becomes commonplace. Taken together, the field of therapeutic cancer vaccines is fast evolving, with the promise of potential synergy with existing immunotherapies for long-term cancer treatment.

Cancer Immune Therapy for Philadelphia Chromosome-Negative Chronic Myeloproliferative Neoplasms

Philadelphia chromosome-negative chronic myeloproliferative neoplasms (MPN) are neoplastic diseases of the hematopoietic stem cells in the bone marrow. MPN are characterized by chronic inflammation and immune dysregulation. Of interest, the potent immunostimulatory cytokine interferon-α has been used to treat MPN for decades. A deeper understanding of the anti-cancer immune response and of the different immune regulatory mechanisms in patients with MPN has paved the way for an increased perception of the potential of cancer immunotherapy in MPN. Therapeutic vaccination targeting the driver mutations in MPN is one recently described potential new treatment modality. Furthermore, T cells can directly react against regulatory immune cells because they recognize proteins like arginase and programmed death ligand 1 (PD-L1). Therapeutic vaccination with arginase or PD-L1 therefore offers a novel way to directly affect immune inhibitory pathways, potentially altering tolerance to tumor antigens like mutant CALR and mutant JAK2. Other therapeutic options that could be used in concert with therapeutic cancer vaccines are immune checkpoint-blocking antibodies and interferon-α. For more advanced MPN, adoptive cellular therapy is a potential option that needs more preclinical investigation. In this review, we summarize current knowledge about the immune system in MPN and discuss the many opportunities for anti-cancer immunotherapy in patients with MPN.

Mechanisms of Epstein-Barr virus nuclear antigen 1 favor Tregs accumulation in nasopharyngeal carcinoma

Background

Documented reports proved that Epstein‐Barr virus (EBV) infection increased infiltration of Tregs in malignancy. However, the mechanism of EBV recruitment Tregs into nasopharyngeal carcinoma (NPC) tissues has not been detailed discussion.

Methods

Expression of EBV nuclear antigen 1 (EBNA1) and Foxp3 in NPC tissue samples was detected by immunohistochemistry. EBNA1+ NPC cell lines were used to coculture with PBMC, naïve T cells, Tregs, and monocytes. Percent of Treg was detected by flow cytometry.

Results

EBNA1 protein was overexpressed in NPC tissues, and was associated with a number of infiltrated Tregs. EBNA1+ NPC cells converted naïve T cells into Tregs by up‐regulated TGF‐β1. Enhanced CCL20 production in EBNA1‐expressed tumor cells increased Tregs migration. Polarized‐M2 macrophages by EBNA1 expression cells converted naïve T cells into Tregs.

Conclusions

EBNA1 favors accumulation of Tregs in NPC through: (a) upregulated TGF‐β1 converted naïve T cell into Treg; (b) upregulated CCL20 increased Treg migration; and (c) polarized‐M2 macrophage converted naïve T cell into Treg.

Arginase-1-based vaccination against the tumor microenvironment: the identification of an optimal T-cell epitope

L-arginine depletion by regulatory cells and cancer cells expressing arginase-1 (Arg-1) is a vital contributor to the immunosuppressive tumor microenvironment in patients with cancer. We have recently described the existence of pro-inflammatory effector T cells that recognize Arg-1. Hence, Arg-1-specific self-reactive T cells are a naturally occurring part of the memory T-cell repertoire of the human immune system. Here, we further characterize a highly immunogenic epitope from Arg-1. We describe frequent T-cell-based immune responses against this epitope in patients with cancer, as well as in healthy donors. Furthermore, we show that Arg-1-specific T cells expand in response to the T_H2 cytokine interleukin (IL)-4 without any specific stimulation. Arg-1-specific memory T_H1 cells that respond to increased IL-4 concentration may, therefore, drive the immune response back into the T_H1 pathway. Arg-1-specific T cells thus appear to have an important function in immune regulation. Because Arg-1 plays an important role in the immunosuppressive microenvironment in most cancers, an immune modulatory vaccination approach can readily be employed to tilt the balance away from immune suppression in these settings.

Nicotinamide and Demographic and Disease transitions: Moderation is Best

Good health and rapid progress depend on an optimal dose of nicotinamide. Too little meat triggers the neurodegenerative condition pellagra and tolerance of symbionts such as tuberculosis (TB), risking dysbioses and impaired resistance to acute infections. Nicotinamide deficiency is an overlooked diagnosis in poor cereal-dependant economies masquerading as 'environmental enteropathy' or physical and cognitive stunting. Too much meat (and supplements) may precipitate immune intolerance and autoimmune and allergic disease, with relative infertility and longevity, via the tryptophan-nicotinamide pathway. This switch favours a dearth of regulatory T (Treg) and an excess of T helper cells. High nicotinamide intake is implicated in cancer and Parkinson's disease. Pro-fertility genes, evolved to counteract high-nicotinamide-induced infertility, may now be risk factors for degenerative disease. Moderation of the dose of nicotinamide could prevent some common diseases and personalised doses at times of stress or, depending on genetic background or age, may treat some other conditions.

Novel Strategies for Peptide-Based Vaccines in Hematological Malignancies

Peptides vaccination is an interesting approach to activate T-cells toward desired antigens in hematological malignancies. In addition to classical tumor associated antigens, such as cancer testis antigens, new potential targets for peptide vaccination comprise neo-antigens including JAK2 and CALR mutations, and antigens from immune regulatory proteins in the tumor microenvironment such as programmed death 1 ligands (PD-L1 and PD-L2). Immunosuppressive defenses of tumors are an important challenge to overcome and the T cell suppressive ligands PD-L1 and PD-L2 are often present in tumor microenvironments. Thus, PD-L1 and PD-L2 are interesting targets for peptide vaccines in diseases where the tumor microenvironment is known to play an essential role such as multiple myeloma and follicular lymphoma. In myelodysplastic syndromes the drug azacitidine re-exposes tumor associated antigens, why vaccination with related peptides would be an interesting addition. In myeloproliferative neoplasms the JAK2 and CALR mutations has proven to be immunogenic neo-antigens and thus possible targets for peptide vaccination. In this mini review we summarize the basis for these novel approaches, which has led to the initiation of clinical trials with various peptide vaccines in myelodysplastic syndromes, myeloproliferative neoplasms, multiple myeloma, and follicular lymphoma.

Cancer immune therapy for myeloid malignancies: present and future

The myelodysplastic syndromes, the chronic myeloproliferative neoplasms, and the acute myeloid leukemia are malignancies of the myeloid hematopoietic stem cells of the bone marrow. The diseases are characterized by a dysregulation of the immune system as both the cytokine milieu, immune phenotype, immune regulation, and expression of genes related to immune cell functions are deregulated. Several treatment strategies try to circumvent this deregulation, and several clinical and preclinical trials have shown promising results, albeit not in the same scale as chimeric antigen receptor T cells have had in the treatment of refractory lymphoid malignancies. The use of immune checkpoint blocking antibodies especially in combination with hypomethylating agents has had some success-a success that will likely be enhanced by therapeutic cancer vaccination with tumor-specific antigens. In the chronic myeloproliferative neoplasms, the recent identification of immune responses against the Januskinase-2 and calreticulin exon 9 driver mutations could also be used in the vaccination setting to enhance the anti-tumor immune response. This immune response could probably be enhanced by the concurrent use of immune checkpoint inhibitors or by vaccination with epitopes from immune regulatory proteins such as arginase-1 and programmed death ligand-1. Herein, we provide an overview of current cancer immune therapeutic treatment strategies as well as potential future cancer immune therapeutic treatment options for the myeloid malignancies.

The T-win® technology: immune-modulating vaccines

The T-win® technology is an innovative investigational approach designed to activate the body's endogenous anti-regulatory T cells (anti-Tregs) to target regulatory as well as malignant cells. Anti-Tregs are naturally occurring T cells that can directly react against regulatory immune cells because they recognize proteins that these targets express, including indoleamine 2,3-dioxygenase (IDO), tryptophan 2,6-dioxygenase, arginase, and programmed death ligand 1 (PD-L1). The T-win® technology is characterized by therapeutic vaccination with long peptide epitopes derived from these antigens and therefore offers a novel way to target genetically stable cells with regular human leukocyte antigen expression in the tumor microenvironment. The T-win® technology thus also represents a novel way to attract pro-inflammatory cells to the tumor microenvironment where they can directly affect immune inhibitory pathways, potentially altering tolerance to tumor antigens. The modification of an immune regulatory environment into a pro-inflammatory milieu potentiates effective anti-tumor T cell responses. Many regulatory immune cells may be reverted into effector cells given the right stimulus. Because T-win® technology is based on the immune-modulatory function of the vaccines, the vaccines activate both CD4 and CD8 anti-Tregs. Of importance, in clinical trials, vaccinations against IDO or PD-L1 to potentiate anti-Tregs have so far proved to be safe, with minimal toxicity.

GATA3, HDAC6, and BCL6 Regulate FOXP3+ Treg Plasticity and Determine Treg Conversion into Either Novel Antigen-Presenting Cell-Like Treg or Th1-Treg

We conducted an experimental database analysis to determine the expression of 61 CD4+ Th subset regulators in human and murine tissues, cells, and in T-regulatory cells (Treg) in physiological and pathological conditions. We made the following significant findings: (1) adipose tissues of diabetic patients with insulin resistance upregulated various Th effector subset regulators; (2) in skin biopsy from patients with psoriasis, and in blood cells from patients with lupus, effector Th subset regulators were more upregulated than downregulated; (3) in rosiglitazone induced failing hearts in ApoE-deficient (KO) mice, various Th subset regulators were upregulated rather than downregulated; (4) aortic endothelial cells activated by proatherogenic stimuli secrete several Th subset-promoting cytokines; (5) in Treg from follicular Th (Tfh)-transcription factor (TF) Bcl6 KO mice, various Th subset regulators were upregulated; whereas in Treg from Th2-TF GATA3 KO mice and HDAC6 KO mice, various Th subset regulators were downregulated, suggesting that Bcl6 inhibits, GATA3 and HDAC6 promote, Treg plasticity; and (6) GATA3 KO, and Bcl6 KO Treg upregulated MHC II molecules and T cell co-stimulation receptors, suggesting that GATA3 and BCL6 inhibit Treg from becoming novel APC-Treg. Our data implies that while HDAC6 and Bcl6 are important regulators of Treg plasticity, GATA3 determine the fate of plastic Tregby controlling whether it will convert in to either Th1-Treg or APC-T-reg. Our results have provided novel insights on Treg plasticity into APC-Treg and Th1-Treg, and new therapeutic targets in metabolic diseases, autoimmune diseases, and inflammatory disorders.

Frequent adaptive immune responses against arginase-1

The enzyme arginase-1 reduces the availability of arginine to tumor-infiltrating immune cells, thus reducing T-cell functionality in the tumor milieu. Arginase-1 is expressed by some cancer cells and by immune inhibitory cells, such as myeloid-derived suppressor cells (MDSCs) and tumor-associated macrophages (TAMs), and its expression is associated with poor prognosis. In the present study, we divided the arginase-1 protein sequence into overlapping 20-amino-acid-long peptides, generating a library of 31 peptides covering the whole arginase-1 sequence. Reactivity towards this peptide library was examined in PBMCs from cancer patients and healthy individuals. IFNγ ELISPOT revealed frequent immune responses against multiple arginase-1-derived peptides. We further identified a hot-spot region within the arginase-1 protein sequence containing multiple epitopes recognized by T cells. Next, we examined in vitro-expanded tumor-infiltrating lymphocytes (TILs) isolated from melanoma patients, and detected arginase-1-specific T cells that reacted against epitopes from the hot-spot region. Arginase-1-specific CD4+T cells could be isolated and expanded from peripheral T cell pool of a patient with melanoma, and further demonstrated the specificity and reactivity of these T cells. Overall, we showed that arginase-1-specific T cells were capable of recognizing arginase-1-expressing cells. The activation of arginase-1-specific T cells by vaccination is an attractive approach to target arginase-1-expressing malignant cells and inhibitory immune cells. In the clinical setting, the induction of arginase-1-specific immune responses could induce or increase Th1 inflammation at the sites of tumors that are otherwise excluded due to infiltration with MDSCs and TAMs.

The inhibitory checkpoint, PD-L2, is a target for effector T cells: Novel possibilities for immune therapy

Cell surface molecules of the B7/CD28 family play an important role in T-cell activation and tolerance. The relevance of the PD-1/PD-L1 pathway in cancer has been extensively studied whereas PD-L2 has received less attention. However, recently the expression of PD-L2 was described to be independently associated with clinical response in anti-PD1-treated cancer patients. Here, we investigated whether PD-L2 might represent a natural target that induces specific T cells. We identified spontaneous specific T-cell reactivity against two epitopes located in the signal peptide of PD-L2 from samples from patients with cancer as well as healthy individuals ex vivo. We characterized both CD8⁺ and CD4⁺ PD-L2-specific T cells. Interestingly, the epitope in PD-L2 that elicited the strongest response was equivalent to a potent HLA-A2-restricted epitope in PD-L1. Importantly, PD-L1-specific and PD-L2-specific T cells did not cross-react; therefore, they represent different T-cell antigens. Moreover, PD-L2-specific T cells reacted to autologous target cells depending on PD-L2 expression. These results suggested that activating PD-L2 specific T cells (e.g., by vaccination) might be an attractive strategy for anti-cancer immunotherapy. Accordingly, PD-L2 specific T cells can directly support anti-cancer immunity by killing of target cells, as well as, indirectly, by releasing pro-inflammatory cytokines at the microenvironment in response to PD-L2-expressing immune supressive cells.

Mesenchymal stem cells inhibit T cell activation by releasing TGF-β1 from TGF-β1/GARP complex

Intervention with mesenchymal stem cells (MSCs) reveals a promising therapeutic tool to treat transplantation and autoimmune disease due to their immunoregulation capability. But the mechanisms of action are not fully investigated yet. Transforming growth factor-β1 (TGF-β1) exhibit multiple effects in migration, differentiation, and immunomodulation of MSCs. Glycoprotein A repetitions predominant (GARP) is an important marker of activated Treg (regulatory T cells). GARP binds latent TGF-β1 to regulate its activation, which is the indispensable step in Treg suppressing effector T cells. So far we don't know whether GARP present on MSCs and its association with MSCs function. Our study show that MSCs express GARP which binds latent TGF-β1 on their cell surface. We also found that TGF-β1+/- MSCs produce less TGF-β1 and exhibit reduced capacity in inhibiting T cells. When TGF-β1 signaling pathway was blocked, MSCs show decreased activity in inhibiting T cells. Importantly, silencing GARP expression distinctively damaged the capacity of MSCs to inhibit IFN-γ production. These findings indicated the expression of GARP on MSCs and its functionality in activating LAP, thus demonstrating GARP as a novel biomarker and new target to improve the therapeutic efficacy of MSCs.

Immunomodulatory Monoclonal Antibodies in Combined Immunotherapy Trials for Cutaneous Melanoma

In the last few years, there has been a twist in cancer treatment toward immunotherapy thanks to the impressive results seen in advanced patients from several tumor pathologies. Cutaneous melanoma is a highly mutated and immunogenic tumor that has been a test field for the development of immunotherapy. However, there is still a way on the road to achieving complete and long-lasting responses in most patients. It is desirable that immunotherapeutic strategies induce diverse immune reactivity specific to tumor antigens, including the so-called neoantigens, as well as the blockade of immunosuppressive mechanisms. In this review, we will go through the role of promising monoclonal antibodies in cancer immunotherapy with immunomodulatory function, especially blocking of the inhibitory immune checkpoints CTLA-4 and PD-1, in combination with different immunotherapeutic strategies such as vaccines. We will discuss the rational basis for these combinatorial approaches as well as different schemes currently under study for cutaneous melanoma in the clinical trials arena. In this way, the combination of "push and release" immunomodulatory therapies can contribute to achieving a more robust and durable antitumor immune response in patients.

The JAK2V617F and CALR exon 9 mutations are shared immunogenic neoantigens in hematological malignancy

Approximately 90% of patients with the hematological malignancies termed the chronic myeloproliferative neoplasms harbor either the JAK2V617F-mutation or CALR exon 9 mutation. Both of these are recognized by T-cells, which make the mutations ideal targets for cancer immune therapy as they are shared antigens.