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Restoration of exhausted hepatitis B virus (HBV)-specific CD8+ T cells is one of the important strategies for inhibition of viral replication. The role of interleukin (IL)-33 to recovery of CD8+ T cell activity is not fully elucidated. We investigated the effect of IL-33 on viral-specific CD8+ T cell responses in chronic hepatitis B (CHB) patients in vitro by both phenotypic and functional analysis. Plasma IL-33 was downregulated in CHB patients, while effective antiviral therapy rescued IL-33 expression. There was no significant difference of IL-33 receptor mRNA relative level in CD8+ T cells between CHB patients and controls. IL-33 induced the proliferation of HBV-specific CD8+ T cells, and reduced programmed death-1 expression on HBV-specific CD8+ T cells. IL-33 promoted the direct cytolytic activity of CD8+ T cells against HepG2.2.15 cells through boosting perforin and granzyme B production. Furthermore, IL-33 administration increased HBV-specific CD8+ T cell-mediated HBV replication and HBV antigen secretion mainly via enhancement of interferon-γ and tumor necrosis factor-α. IL-33 reinvigorated antiviral activity of HBV-specific CD8+ T cells, revealing that IL-33 might contribute to viral clearance in persistent HBV infection.

ObjectiveThis study aimed to understand the role of mammalian target of rapamycin (mTOR) in CD8+ cells in the pathogenicity of RA and the changes after treatment with biologic drugs.MethodsPeripheral blood mononuclear cells (PBMCs) were isolated from 17 healthy controls and 86 patients with RA. Phosphorylation of mTOR (p-mTOR) and its clinical relevance were evaluated. The role of mTOR in CD8+ cells was also examined in vitro.ResultsPatients with RA who had a moderate or high disease activity, were biologic-naïve, and were refractory to MTX were enrolled in this study. The p-mTOR levels in CD8+ cells were higher in patients with RA than in healthy controls, and they positively correlated with the disease activity in such patients. However, after one year of treatment with TNF inhibitors, the p-mTOR levels in CD8+ cells were suppressed and showed a positive correlation with the treatment response, which was not observed in the abatacept-treatment group. In vitro stimulation of CD8+ cells with anti-CD3 and anti-CD28 antibodies induced mTOR phosphorylation and increased the production of granzyme B, granulysin, TNF-α and IFN-γ but decreased the production of granzyme K. However, on treatment with TNF inhibitors, p-mTOR levels in CD8+ cells and granzyme B production decreased, while granzyme K production increased. The production of granulysin and IFN-γ was not affected by the TNF inhibitors.ConclusionThese results suggested that mTOR activation in CD8+ cells may be a novel evaluation marker for RA disease activity and a predictive marker of therapeutic response to TNF inhibitors.

Invariant NK T (iNKT) cells are innate-like lymphocytes that can recognize the lipid Ag presented by MHC I like molecule CD1d. Distinct tissue distribution of iNKT cells subsets implies a contribution of these subsets to their related tissue regional immunity. iNKT cells are enriched in liver, an organ with unique immunological properties. Whether liver-specific iNKT cells exist and dedicate to the liver immunity remains elusive. Here, a liver-specific CD24+ iNKT subset is shown. Hepatic CD24+ iNKT cells show higher levels of proliferation, glucose metabolism, and mTOR activity comparing to CD24– iNKT cells. Although CD24+ iNKT cells and CD24– iNKT cells in the liver produce similar amounts of cytokines, the hepatic CD24+ iNKT cells exhibit lower granzyme B production. These liver-specific CD24+ iNKT cells are derived from thymus and differentiate into CD24+ iNKT in the liver microenvironment. Moreover, liver microenvironment induces the formation of CD24+ conventional T cells as well, and these cells exhibit higher proliferation ability but lower granzyme B production in comparison with CD24– T cells. The results propose that liver microenvironment might induce the generation of liver-specific iNKT subset that might play an important role in maintaining liver homeostasis.

Negative immune checkpoint blockade immunotherapy has shown potential for multiple malignancies including colorectal cancer (CRC). B7-H5, a novel negative immune checkpoint regulator, is highly expressed in tumor tissues and promotes tumor immune escape. However, the clinical significance of B7-H5 expression in CRC and the role of B7-H5 in the tumor microenvironment (TME) has not been fully clarified. In this study, we observed that high B7-H5 expression in CRC tissues was significantly correlated with the lymph node involvement, AJCC stage, and survival of CRC patients. A significant inverse correlation was also observed between B7-H5 expression and CD8+ T-cell infiltration in CRC tissues. Kaplan−Meier analysis showed that patients with high B7-H5 expression and low CD8+ T-cell infiltration had the worst prognosis in our cohort of CRC patients. Remarkably, both high B7-H5 expression and low CD8+ T infiltration were risk factors for overall survival. Additionally, B7-H5 blockade using a B7-H5 monoclonal antibody (B7-H5 mAb) effectively suppressed the growth of MC38 colon cancer tumors by enhancing the infiltration and Granzyme B production of CD8+ T cells. Importantly, the depletion of CD8+ T cells obviously abolished the antitumor effect of B7-H5 blockade in the MC38 tumors. In sum, our findings suggest that B7-H5 may be a valuably prognostic marker for CRC and a potential target for CRC immunotherapy.

Suxing Liu,1 Di Li,1 Jian Liu,2 Huiyun Wang,1 Ivana Horecny,1 Ru Shen,1 Rumin Zhang,1 Heping Wu,2 Qiyue Hu,3 Peng Zhao,2 Fengqi Zhang,2 Yinfa Yan,2 Jun Feng,4 Linghang Zhuang,2 Jing Li,1 Lianshan Zhang,5 Weikang Tao5 1Department of Biology, Eternity Bioscience Inc., Cranbury, NJ, 08512, USA; 2Department of Chemistry, Eternity Bioscience Inc., Cranbury, NJ, 08512, USA; 3Department of Molecular Modeling, Shanghai Hengrui Pharmaceutical Co. Ltd., Shanghai, 200245, People’s Republic of China; 4Department of Process Chemistry, Shanghai Hengrui Pharmaceutical Co. Ltd., Shanghai, 200245, People’s Republic of China; 5R&D Center, Shanghai Hengrui Pharmaceutical Co. Ltd., Shanghai, 200245, People’s Republic of ChinaCorrespondence: Suxing LiuDepartment of Biology, Eternity Bioscience Inc, 6 Cedarbrook Drive, Cranbury, NJ, 08512, USAEmail lius@eternitybioscience.comIntroduction: CD73 and adenosine support growth-promoting neovascularization, metastasis, and survival in cells, and promote anti-PD-1 mAb therapy-induced immune escape. Consequently, developing a CD73 inhibitor as monotherapy and a potential beneficial combination partner with immune-checkpoint inhibitors needs investigation.Methods: CD73 inhibitors were evaluated in vitro with soluble and membrane-bound CD73 enzymes, as well as its PD biomarker responses in human peripheral blood mononuclear cells (PBMC) by flow cytometry and ELISA. The binding modes of the molecules were analyzed via molecular modeling. The anti-tumor activity and synergistic effect of SHR170008 in combination with anti-PD-1 mAb were evaluated in a syngeneic mouse breast cancer model.Results: SHR170008 was discovered during the initial structural modifications on the link between the ribose and the α-phosphate of AMPCP, which significantly improved the stability of the compound confirmed by the metabolite identification study. Further modifications on the adenine base of AMPCP improved the potency due to forming stronger interactions with CD73 protein. It exhibited potent inhibitory activities on soluble and endogenous membrane-bound CD73 enzymes, and induced IFNγ production, reversed AMP-suppressed CD25+ and CD8+/CD25+ expression, and enhanced granzyme B production on CD8+ T cells in human PBMC. SHR170008 showed dose-dependent anti-tumor efficacy with suppression of adenosine in the tumors in EMT6 mouse breast tumor model. The increase of adenosine in tumor tissue by anti-PD-1 mAb alone was suppressed by SHR170008 in the combination groups. Simultaneous inhibition of CD73 and PD-1 neutralization synergistically enhanced antitumor immunity and biomarkers in response, and exposures of SHR170008 were correlated with the efficacy readouts.Conclusion: Our findings suggest that CD73 may serve as an immune checkpoint by generating adenosine, which suppresses the antitumor activity of anti-PD-1 mAb, and inhibition of CD73 may be a potential beneficial combination partner with immune-checkpoint inhibitors to improve their therapeutic outcomes in general.Keywords: small-molecule inhibitor of CD73, adenosine, anti-PD-1 mAb, checkpoint blockade, immunotherapy, combination therapy

Despite recent advances in cancer immunotherapy, there have been limitations in cancer treatment and patient survival due to a lack of antigen recognition and immunosuppressive tumor microenvironment. To overcome this issue, we have shown that miRNA modified tumor-derived Extracellular Vesicles (mt-EVs) would be an advantageous prospect since they are tumor specific and associated antigen sources which cause increase in maturation and antigen-presenting function of dendritic cells. Also, miRNAs are promising candidates for cancer therapy because of their ability to control several host immune subsets to respond against cancer cells as well as tumor microenvironment remodeling. Here, we report that mt-EVs containing tumor specific antigens loaded with miRNAs (Let-7i, miR-142 and, miR-155) could increase the survival rate of tumor-bearing mice and induce reduction in tumor growth. Importantly, the administration of mt-EVs elicited cytotoxic T cells with increasing in IFNγ and Granzyme B production ability. Notably, intramuscular (IM) injection of let7i, miR142-EVs had a significant effect on dendritic cell (DC) maturation and T cell activation along with tumor shrinkage. Collectively, our findings suggest that administration of miRNA containing EVs may be effective immunotherapy against solid tumors.

Background Cancer-associated fibroblasts (CAFs) in the tumour microenvironment (TME) suppress antitumour immunity, and the tyrosine kinase inhibitor nintedanib has antifibrotic effects. Methods We performed a preclinical study to evaluate whether nintedanib might enhance antitumour immunity by targeting CAFs and thereby improve the response to immune checkpoint blockade (ICB). Results Whereas nintedanib did not suppress the growth of B16-F10 melanoma cells in vitro, it prolonged survival in a syngeneic mouse model of tumour formation by these cells, suggestive of an effect on the TME without direct cytotoxicity. Gene expression profiling indeed showed that nintedanib influenced antitumour immunity and fibrosis. Tumoural infiltration of CD8+ T cells and granzyme B production were increased by nintedanib, and its antitumour activity was attenuated by antibody-mediated depletion of these cells, indicating that nintedanib suppressed tumour growth in a CD8+ T cell-dependent manner. Moreover, nintedanib inhibited the proliferation and activation of fibroblasts. Finally, the combination of nintedanib with ICB showed enhanced antitumour efficacy in B16-F10 tumour-bearing mice. Conclusions Our results suggest that nintedanib targeted CAFs and thereby attenuated the immunosuppressive nature of the TME and promoted the intratumoural accumulation and activation of CD8+ T cells, with these effects contributing to enhanced antitumour activity in combination with ICB.

Abstract This study shows that melanoma-associated fibroblasts (MAFs) suppress cytotoxic T lymphocyte (CTL) activity and reveals a pivotal role played by arginase in this phenomenon. MAFs and normal dermal fibroblasts (DFs) were isolated from surgically resected melanomas and identified as Melan-A-/gp100-/FAP+ cells. CTLs of healthy blood donors were activated in the presence of MAF- and DF-conditioned media (CM). Markers of successful CTL activation, cytotoxic degranulation, killing activity and immune checkpoint regulation were evaluated by flow cytometry, ELISPOT, and redirected killing assays. Soluble mediators responsible for MAF-mediated effects were identified by ELISA, flow cytometry, inhibitor assays, and knock-in experiments. In the presence of MAF-CM, activated/non-naïve CTLs displayed dysregulated ERK1/2 and NF-κB signaling, impeded CD69 and granzyme B production, impaired killing activity, and upregulated expression of the negative immune checkpoint receptors TIGIT and BTLA. Compared to DFs, MAFs displayed increased amounts of VISTA and HVEM, a known ligand of BTLA on T cells, increased l-arginase activity and CXCL12 release. Transgenic arginase over-expression further increased, while selective arginase inhibition neutralized MAF-induced TIGIT and BTLA expression on CTLs. Our data indicate that MAF interfere with intracellular CTL signaling via soluble mediators leading to CTL anergy and modify immune checkpoint receptor availability via l-arginine depletion. Graphic abstract

Significance New strategies are needed to improve efficacy of anti-PD1 therapy in cancer treatment. Ascorbic acid (AA, vitamin C) has been previously shown to cause genome-wide demethylation in multiple malignancies by enhancing the activity of the Ten-Eleven Translocation (TET) enzymes. This study shows that AA treatment 1) increases immunogenicity of lymphoma cells; 2) enhances intratumoral infiltration of CD8+ T cells and macrophages; and 3) synergizes with anti-PD1 checkpoint inhibition in a syngeneic lymphoma mouse model via marked activation of cytotoxic cells (cytotoxic T cells and NK cells) and antigen presenting cells. The data provide a compelling rationale for testing combinations of high-dose AA and anti-PD1 agents in patients with aggressive B cell lymphoma and in preclinical models of other malignancies., Major efforts are underway to identify agents that can potentiate effects of immune checkpoint inhibition. Here, we show that ascorbic acid (AA) treatment caused genomewide demethylation and enhanced expression of endogenous retroviral elements in lymphoma cells. AA also increased 5-hydroxymethylcytosine (5hmC) levels of CD8+ T cells and enhanced their cytotoxic activity in a lymphoma coculture system. High-dose AA treatment synergized with anti-PD1 therapy in a syngeneic lymphoma mouse model, resulting in marked inhibition of tumor growth compared with either agent alone. Analysis of the intratumoral epigenome revealed increased 5hmC with AA treatment, consistent with in vitro findings. Analysis of the tumor immune microenvironment revealed that AA strikingly increased intratumoral infiltration of CD8+ T cells and macrophages, suggesting enhanced tumor immune recognition. The combination treatment markedly enhanced intratumoral infiltration of macrophages and CD8+ T lymphocytes, granzyme B production by cytotoxic cells (cytotoxic T cells and natural killer cells), and interleukin 12 production by antigen-presenting cells compared with single-agent anti-PD1. These data indicate that AA potentiates anti-PD1 checkpoint inhibition through synergistic mechanisms. The study provides compelling rationale for testing combinations of high-dose AA and anti-PD1 agents in patients with aggressive B cell lymphoma as well as in preclinical models of other malignancies.

Liver metastases (LM) remain a major cause of cancer-associated death and a clinical challenge. Here we explore a sexual dimorphism observed in the regulation of the tumor immune microenvironment (TIME) of LM, wherein the accumulation of myeloid-derived suppressor cells (MDSC) and regulatory T cells in colon and lung carcinoma LM is TNFR2-dependent in female, but not in male mice. In ovariectomized mice, a marked reduction is observed in colorectal, lung and pancreatic carcinoma LM that is reversible by estradiol reconstitution. This is associated with reduced liver MDSC accumulation, increased interferon-gamma (IFN-γ) and granzyme B production in CD8+ T cells and reduced TNFR2, IDO2, TDO and Serpin B9 expression levels. Treatment with tamoxifen increases liver cytotoxic T cell accumulation and reduces colon cancer LM. The results identify estrogen as a regulator of a pro-metastatic immune microenvironment in the liver and a potential target in the management of liver metastatic disease., It is known that estrogens can affect the immune response to cancer. Here, the authors show that estrogen depletion through ovariectomy reduces the extent of liver metastasis and that this is accompanied by a decrease in the number and function of immunosuppressive cells in the metastatic microenvironment.

In chronic Hepatitis B Virus (HBV) infections HBV-specific T cells are functionally impaired. Immunotherapy may restore HBV-specific T cell responses essential for sustained disease remission off-treatment and induction of a functional cure. Chimigen® Molecules are fusion proteins of antigen(s) with the Fc fragment of a xenotypic antibody designed to target specific receptors on dendritic cells (DCs). Here we describe the production and pre-clinical evaluation of Chimigen® HBV (C-HBV), containing HBV PreS1 and PreS2 peptide fragments, HBV core and murine Fc, produced in insect cells. C-HBV binding to immature DCs and internalization by endocytosis was FcγRII (CD32) and mannose receptor (CD206) dependent and led to increased MHC I and MHC II surface expression. Upon exposure of human T cells isolated from HBV un-infected healthy and chronically HBV-infected donors to C-HBV-pulsed mature DCs ex vivo, C-HBV induced vigorous T cell proliferation and enhanced expression of IFN-γ, TNF-α, perforin and granzyme B in both CD4+ and CD8+ T cell subsets. Re-stimulation of C-HBV-activated T cells from chronically infected donors with HBV PreS1/PreS2 and core overlapping peptides induced IFN-γ production in both CD4+ and CD8+ populations. C-HBV-activation of peripheral blood mononuclear cells (PBMCs) from chronically HBV-infected patients stimulated granzyme B production by CD4+CD25− T responder (Tresp) cells, accompanied by an increase in Annexin V staining on CD4+CD25+ T regulatory (Treg) cell phenotype, consistent with apoptosis. The observed HBV-specific cellular responses induced by C-HBV ex vivo suggest that C-HBV is a promising immunotherapeutic candidate for the treatment of chronic HBV infections.

Aims/hypothesis Mucosal-associated invariant T (MAIT) cells are innate-like T lymphocytes expressing an αβ T cell antigen receptor that recognises the MHC-related 1 molecule. MAIT cells are altered in children at risk for and with type 1 diabetes, and mouse model studies have shown MAIT cell involvement in type 1 diabetes development. Since several studies support heterogeneity in type 1 diabetes physiopathology according to the age of individuals, we investigated whether MAIT cells were altered in adults with type 1 diabetes. Methods MAIT cell frequency, phenotype and function were analysed by flow cytometry, using fresh peripheral blood from 21 adults with recent-onset type 1 diabetes (2–14 days after disease onset) and 47 adults with long-term disease (>2 years after diagnosis) compared with 55 healthy blood donors. We also separately analysed 17 women with long-term type 1 diabetes and an associated autoimmune disease, compared with 30 healthy women and 27 women with long-term type 1 diabetes. Results MAIT cells from adults with recent-onset type 1 diabetes, compared with healthy adult donors, harboured a strongly activated phenotype indicated by an elevated CD25+ MAIT cell frequency. In adults with long-term type 1 diabetes, MAIT cells displayed an activated and exhausted phenotype characterised by high CD25 and programmed cell death 1 (PD1) expression and a decreased production of proinflammatory cytokines, IL-2, IFN-γ and TNF-α. Even though MAIT cells from these patients showed upregulated IL-17 and IL-4 production, the polyfunctionality of MAIT cells was decreased (median 4.8 vs 13.14% of MAIT cells, p

Background: Chronic Hepatitis B (CHB) remains a major problem for global public health. Viral persistence and immune defects are the two major reasons for CHB, and it was hypothesized that based on a transient clearance of serum viral DNA and HBsAg “window stage”, active immunization against hepatitis B virus (HBV) might initiate effective host immune responses versus HBV to achieve functional cure of CHB. Methods: Two experimental mouse models that mice hydrodynamic injected HBV DNA or infected with recombinant AAV/HBV were used. The “sandwich” therapeutic effect by using a potent human anti-HBsAg neutralizing monoclonal antibody (G12) in combination with antiviral drug tenofovir disoproxil fumarate (TDF), followed by active immunization with HBsAg-HBsAb (mYIC) was evaluated. Findings: A single G12 injection rapidly cleared serum HBsAg in HDI-HBV carrier mice, with a synergistic effect in decreasing viral DNA load when TDF was given orally. When both serum viral DNA and HBsAg load became low or undetectable, mYIC was administered. A more effective clearance of viral DNA and HBsAg was observed and serum HBsAb was developed only in these “sandwich”-treated mice. Efficient intrahepatic anti-HBV immune responses were also observed in these mice, including the formation of aggregates of myeloid cells with CD8+ T cells and increased TNF-α, granzyme B production. Interpretation: The “sandwich” combination therapy not only efficiently decreased HBsAg and HBV DNA levels but also induced effective cellular and humoral immunity, which may result in functional cure of CHB. Keywords: Chronic hepatitis B, HBsAb, TDF, HBsAg-HBsAb immune complex, Liver CD8+ T cells

Respiratory syncytial virus (RSV) is a common cause of childhood lower respiratory tract infections. The recent failure of a vaccine candidate based on recombinant F protein underlines the urgent need to better understand the protective human memory immune response against RSV. Signal transducer and activator of transcription 3 (STAT3) protein is a transcription factor that promotes the maturation of the memory CD8 T cell response in cooperation with IL-10 and IL-21. However, the role of STAT3 in the memory CD8 T cell response during RSV infection remains to be elucidated. We found that in infants with bronchiolitis infected with RSV, the expression of STAT3 detected in nasal washes is reduced when compared to that in infants infected by other viruses. In vitro, RSV impairs STAT3 phosphorylation induced by IL-21 in purified human memory CD8 T cells. In addition, RSV decreases granzyme B production by memory CD8 T cells, reducing its cytotoxic activity against RSV-infected epithelial pulmonary cell lines. Together, these data indicate that RSV modulates the IL-21/STAT3 pathway in human memory CD8 T cells, and this could be a mechanism to be further explored to improve the memory response against the infection.

Wiskott-Aldrich syndrome (WAS) patients are characterized by immunodeficiency and viral infections. T cells derived from WAS patients and WAS protein (WASP)-deficient mice have various defects. However, whether WASP plays a role in immune control of cytomegalovirus (CMV) infection remains unclear. We analyzed the distribution of CD8+ T subsets and the pathological damage to various organs and tissues in MCMV infected Was knockout (KO) mice. A relatively high number of MCMV-specific cytotoxic T cells (CTLs) were observed in the spleen of Was KO mice. In MCMV infected Was KO mice, the late differentiated CD8+ T subset (CD27-CD28-) decreased in lungs, compared with those in the spleen and peripheral blood. Additionally, we found that the most severe pathological lesions occurred in the lungs, the main target organ of MCMV infection. By stimulating the spleen-derived CD8+ T lymphocytes of Was KO mice, we found that IL-2 and granzyme B production declined compared with that in wild- type mice. Moreover, the number of apoptotic CD8+ T cells increased in Was KO mice compared with the number in wild-type mice. Therefore, our results demonstrate that WASP may be involved in regulating cytotoxic function and apoptosis in CD8+ T cells following MCMV infection, which is supported by the distribution and memory compartment of MCMV-specific T cells in MCMV infected WAS mice.

Cytokine-activated T cells (CATs) can be easily expanded and are widely applied to cancer immunotherapy. However, the good efficacy of CATs is rarely reported in clinical applications because CATs have no or very low antigen specificity. The low-efficacy problem can be resolved using T cell antigen receptor-engineered CAT (TCR-CAT). Herein, we demonstrate that NY-ESO-1157-165 HLA-A*02:01-specific high-affinity TCR (HAT)-transduced CATs can specifically kill cancer cells with good efficacy. With low micromolar range dissociation equilibrium constants, HAT-transduced CATs showed good specificity with no off-target killing. Furthermore, the high-affinity TCR-CATs delivered significantly better activation and cytotoxicity than the equivalent TCR-engineered T cells (TCR-Ts) in terms of interferon-γ and granzyme B production and in vitro cancer cell killing ability. TCR-CAT may be a very good alternative to the expensive TCR-T, which is considered an effective personalized cyto-immunotherapy.

Aim. The aim of the study was to evaluate the ability of pMEL-TCI and pMEL-A0201 DNA-constructs encoding artificial polyepitope melanoma antigens to induce antitumor T cell immune response ex vivo. material and methods. Dendritic cells were obtained from peripheral blood mononuclear cells of HLA-A02:01-positive donors; DCs transfected with target DNA vaccine constructions were co-cultured with autologous T lymphocytes to stimulate anti-tumor effector T cells. Specific activity of ex vivo stimulated PBMC was assessed (1) by their ability to cause lysis of human melanoma Mel Is cells, and (2) by the level of their granzyme-producing activity. A recombinant plasmid encoding the full-length MART-1 melanoma antigen was used as a positive control. results. All DNA vaccine constructions as well as positive control construction were found to be able to stimulate specific anti-tumor immune responses of autologous PBMC ex vivo, and these PBMC were found to induce melanoma Mel Is cells lysis. Both the efficiency of induced cytotoxic responses and the level of granzymes production stimulated with DCs transfected with pMel-A0201 significantly exceeded those stimulated with DCs transfected with either pMel-TCI or with DNA construction encoding the full-length MART-1 protein. The cytotoxicity level correlates with the level of granzyme B production in CD8+ T lymphocytes. conclusion. DNA vaccine constructions encoding artificial polypeptides composed of tumor antigen epitopes can stimulate the antitumor cytotoxic response. This approach can be used as the basis for the development of new methods of immunotherapy for cancer.

Gastrointestinal viral infections are a major global cause of disease and mortality in infants. Cytotoxic CD8+ T cells are critical to achieve viral control. However, studies investigating the development of CD8+ T cell immunity in human tissues early in life are lacking. Here, we investigated the maturation of the CD8+ T cell compartment in human fetal, infant and adult intestinal tissues. CD8+ T cells exhibiting a memory phenotype were already detected in fetal intestines and increased after birth. Infant intestines preferentially harbored effector CCR7−CD45RA−CD127−KLRG1+/− CD8+ T cells compared to tissue-resident memory CD69+CD103+CD8+ T cells detected in adults. Functional cytotoxic capacity, including cytokine and granzyme B production of infant intestinal effector CD8+ T cells was, however, markedly reduced compared to adult intestinal CD8+ T cells. This was in line with the high expression of the inhibitory molecule PD-1 by infant intestinal effector CD8+ T cells. Taken together, we demonstrate that intestinal CD8+ T cell responses are induced early in human development, however exhibit a reduced functionality. The impaired CD8+ T cell functionality early in life contributes to tolerance during foreign antigen exposure after birth, however functions as an immune correlate for the increased susceptibility to gastrointestinal viral infections in infancy.

Granzyme B-producing B cells have been reportedly reported to be an important regulatory B cell subset in the pathogenesis of many diseases. However, its role in liver transplant recipients with acute rejection has never been well elucidated. Seventeen liver transplant recipients with acute rejection and 25 controls with stable liver function were enrolled in this study to determine the function of granzyme B-producing B cells via flow cytometry. Liver transplant recipients with acute rejection had higher expression of granzyme B in CD19+B cells when compared with controls. Following rejection, the granzyme B production was even elevated although comparison failed to reach significance. The percentages of CD27+granzyme B+CD19+B cells and CD138+granzyme B+CD19+B cells were lower than those of CD27-granzyme B+CD19+B cells and CD138-granzyme B+CD19+B cells in patients with acute rejection, respectively. While the production of CD27 and CD138 was not different between liver transplant recipients with and without acute rejection but increased expression of the two surface markers was observed following rejection. Furthermore, the frequency of granzyme B+CD19+B cells correlated with the level of alanine aminotransferase instead of tacrolimus. CD19+B cells could produce granzyme B when stimulated with IgG + IgM and CpG in the presence of the supernatant of activated CD4+CD25-T cells. In return, granzyme B+CD19+B cells could suppress the proliferation of CD4+CD25-T cells in a granzyme B- and contact-dependent manner. The increased expression of granzyme B in CD19+B cells from liver transplant recipients with acute rejection might function as a feedback loop for the activation of the CD4+CD25-T cells.

Bronchi from COPD are an area of extensive immune cell infiltration and changes in tissue structures, allowing persistent contacts between resident and immune cells. We investigate whether tissue fibrocytes, recently evidenced around COPD bronchi lung, can interact with CD8+ T cells, and whether the contact between both cell types could alter the balance between tissue repair and destruction. Using co-immunostaining of bronchial specimens, we show that fibrocytes and CD8+ T cells are found within close proximity in distal airways of COPD patients, and that indirect and direct interactions are more frequent in tissue from COPD patients compared to those of control subjects. The density of interacting cells is negatively associated with lung function parameters, such as FEV1/FVC. Transcriptome analysis indicates that the attractive capacity of tissular CD8+ T cells is greater in COPD patients than in control subjects. Using in vitro assay based on autologous co-culture with fibrocytes and CD8+ T cells isolated from blood samples of COPD patients, we demonstrate that direct contact between both cell types trigger CD8+ T cell proliferation in a CD11a-dependent manner, and IFN-ɣ, TNF-α and granzyme B production. From these results, we defined a stochastic and computational model, based on local intercellular interactions, with the objective to predict the distributions of the two cell types, depending on whether the subject is healthy or ill. Altogether, this study reveals that local intercellular interactions between fibrocytes and CD8+ T cells can occur in vivo and could result in increased destruction and inappropriate repair in the lung of COPD patients.

Limitations of checkpoint inhibitor cancer immunotherapy include induction of autoimmune syndromes and resistance of many cancers. Since CD318, a novel CD6 ligand, is associated with the aggressiveness and metastatic potential of human cancers, we tested the effect of an anti-CD6 monoclonal antibody, UMCD6, on killing of cancer cells by human lymphocytes. UMCD6 augmented killing of breast, lung, and prostate cancer cells through direct effects on both CD8+ T cells and NK cells, increasing cancer cell death and lowering cancer cell survival in vitro more robustly than monoclonal antibody checkpoint inhibitors that interrupt the programmed cell death 1 (PD-1)/PD-1 ligand 1 (PD-L1) axis. UMCD6 also augmented in vivo killing by human peripheral blood lymphocytes of a human breast cancer line xenotransplanted into immunodeficient mice. Mechanistically, UMCD6 upregulated the expression of the activating receptor NKG2D and downregulated expression of the inhibitory receptor NKG2A on both NK cells and CD8+ T cells, with concurrent increases in perforin and granzyme B production. The combined capability of an anti-CD6 monoclonal antibody to control autoimmunity through effects on CD4+ lymphocyte differentiation while enhancing killing of cancer cells through distinct effects on CD8+ and NK cells opens a potential new approach to cancer immunotherapy that would suppress rather than instigate autoimmunity.

CD39 and CD73 are ectoenzymes that dephosphorylate ATP into its metabolites; ADP, AMP, and adenosine, and thus are considered instrumental in the development of immunosuppressive microenvironments. We have previously shown that within the CD8+ T cell population, naïve and memory cells express the CD73 ectonucleotidase, while terminally differentiated effector cells are devoid of this enzyme. This evidence suggests that adenosine might exert an autocrine effect on CD8+ T cells during T cell differentiation. To study the possible role of CD73 and adenosine during this process, we compared the expression of the adenosinergic signaling components, the phenotype, and the functional properties between CD73-deficient and WT CD8+ T cells. Upon activation, we observed an upregulation of CD73 expression in CD8+ T cells along with an upregulation of the adenosine A2A receptor. Interestingly, when we differentiated CD8+ T cells to Tc1 cells in vitro, we observed that these cells produce adenosine and that CD73-deficient cells present a higher cytotoxic potential evidenced by an increase in IFN-γ, TNF-α, and granzyme B production. Moreover, CD73-deficient cells presented a increased glucose uptake and higher mitochondrial respiration, indicating that this ectonucleotidase restrict the mitochondrial capacity in CD8+ T cells. In agreement, when adoptively transferred, antigen-specific CD73-deficient CD8+ T cells were more effective in reducing the tumor burden in B16.OVA melanoma-bearing mice and presented lower levels of exhaustion markers than wild type cells. All these data suggest an autocrine effect of CD73-mediated adenosine production, limiting differentiation and cytotoxic T cells’ metabolic fitness.

Mucosal-associated invariant T (MAIT) cells are an invariant T cell subset, which have been reported to play an antimicrobial role in infectious diseases. However, little is known about it in malignant diseases and tumors, especially in gastric cancer (GC). So in this study, we aim to examine the frequency, phenotype, partial functional capacity and clinical relevance of this cells from GC patients’ peripheral blood by flow cytometry. It was shown that the frequency of peripheral blood MAIT cells was negatively correlated with their increasing age in healthy adults. Importantly, comparing to the healthy controls (HC), the frequency and the absolute number of MAIT cells from GC patients’ peripheral blood with or without chemotherapy were both significantly lower than those. For the phenotype, the proportion of CD4−MAIT cell subset in GC patients without chemotherapy was lower than in HC, but higher than in GC patients with chemotherapy. Whereas, the proportion of CD4−CD8+MAIT cell subset in GC patients without chemotherapy was significantly lower than that in HC. Finally, the level of Granzyme-B (GrB), a molecule associated with MAIT cells was markedly lower in GC patients. But the correlation between the serum levels of GC-associated tumor antigens and the percentages of MAIT cells in GC patients was not observed. In conclusion, our study shows the decreased frequency, changed phenotypes and partial potentially impaired function of MAIT cells in GC patients, suggesting a possible MAIT cell-based immunological surveillance of GC.

Drugs targeting immune checkpoint molecules have been found effective in melanoma, lung cancer, and other malignancies treatment. Recent studies on breast cancer demonstrated the significance of inhibitory anti-CTLA-4 and anti-PD-1 in the regulation of disease progression. However, seemingly the same types of breast cancer do not always respond unambiguously to immunotherapy. Thus, here we set out to analyze the in vitro effects of inhibiting CTLA-4 and PD-1 on interactions between co-cultured lymphocytes and two selected breast adenocarcinoma cell lines. Breast cancer cells were co-cultured with lymphocytes to evaluate the effects of CTLA-4 and PD-1 inhibition. Proliferation, cell cycle, and viability assessment were measured in cancer cells. IFN-gamma, IL-10, perforin, granzyme B production, and CTLA-4 and PD-1 expression were analyzed in lymphocytes. We found that administration of anti-CTLA-4 improved the anti-cancer activity of T cells with reduced proliferation and viability of MDA-MB-231. Lack of response was observed in the context of MCF-7. In addition, differential expression of checkpoint proteins was found between studied cancer cells lines. Inhibition of molecules was followed by IL-10 and IFN-gamma decrease in lymphocytes co-cultured with MDA-MB-231, not demonstrated in reference to MCF-7. Furthermore, CTLA-4 blockage was associated with reduction of CTLA-4+ and PD-1+ lymphocytes in MDA-MB-231, with a significant increase in MCF-7, reduced by anti-PD-1. Altogether, our study revealed that anti-CTLA-4 and anti-PD-1 treatment can improve lymphocytes effects on breast cancer cells. Favorable effects seemed to be related to breast cancer cells features as differential responses were reported. Novel blocking antibodies strategies should be tested for more effective cancer inhibition.

Background Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with limited systemic treatment options. RX-5902 is a novel anti-cancer agent that inhibits phosphorylated-p68 and thus attenuates nuclear β-catenin signaling. The purpose of this study was to evaluate the ability of β-catenin signaling blockade to enhance the efficacy of anti-CTLA-4 and anti-PD-1 immune checkpoint blockade in immunocompetent, preclinical models of TNBC. Methods Treatment with RX-5902, anti-PD-1, anti-CTLA-4 or the combination was investigated in BALB/c mice injected with the 4 T1 TNBC cell line. Humanized BALB/c-Rag2nullIl2rγnullSIRPαNOD (hu-CB-BRGS) mice transplanted with a human immune system were implanted with MDA-MB-231 cells. Mice were randomized into treatment groups according to human hematopoietic chimerism and treated with RX-5902, anti-PD-1 or the combination. At sacrifice, bone marrow, lymph nodes, spleen and tumors were harvested for flow cytometry analysis of human immune cells. Results The addition of RX-5902 to CTLA-4 or PD-1 inhibitors resulted in decreased tumor growth in the 4 T1 and human immune system and MDA-MB-231 xenograft models. Immunologic analyses demonstrated a significant increase in the number of activated T cells in tumor infiltrating lymphocytes (TILs) with RX-5902 treatment compared to vehicle (p p Conclusions Conclusions: RX-5902 enhanced the efficacy of nivolumab in a humanized, preclinical model of TNBC. Several changes in immunologic profiles were noted in mice treated with RX-5902 and the combination, including an increase in activated TILs and a decrease in human myeloid populations, that are often associated with immunosuppression in a tumor microenvironment. RX-5902 also was shown to potentiate the effects of checkpoint inhibitors of CTLA4 and the PD-1 inhibitor in the 4 T-1 murine TNBC model. These findings indicate that RX-5902 may have important immunomodulatory, as well as anti-tumor activity, in TNBC when combined with a checkpoint inhibitor.

Background Tebentafusp (IMCgp100) is a bispecific T cell redirector comprised of an affinity-enhanced TCR recognising melanocyte lineage antigen gp100 and a T cell engaging anti-CD3 scFv domain. Tebentafusp has shown activity as monotherapy in advanced cutaneous and uveal melanoma (Middleton et al., ASCO 2019), and we have previously reported that over half of uveal melanoma patients treated with tebentafusp display melanocyte-related adverse events (MRAE). These include vitiligo/skin hypopigmentation, leukotrichia, and hyperpigmentation and, collectively, are associated with better overall survival in uveal patients receiving tebentafusp (Orloff et al, AACR 2020). In this study, we dissected the mechanisms by which tebentafusp may induce MRAE and highlight the potential clinical significance. Methods In vitro studies were conducted to assess the direct and indirect effects of tebentafusp on epidermal melanocytes from healthy donors. Expression of gp100 and the gp100:HLA*02:01 target complex by melanocytes were quantified at the mRNA level and on the cell surface by confocal microscopy, respectively. Melanocytes co-cultured with PBMC and increasing concentrations of tebentafusp were assessed for their susceptibility to lysis and/or ability to stimulate cytokine production. These readouts were compared to gp100-positive and negative melanoma cancer cell lines. Melanin production by melanocytes was quantified and the melanin synthesis pathway interrogated at the mRNA and protein level following exposure to secretomes from tebentafusp-redirected PBMC against melanoma cancer cells. Results Healthy melanocytes expressed 2 to 3-fold lower levels of gp100 peptide-HLA complexes on their surface compared to gp100-positive melanoma cell lines. In the presence of tebentafusp, this lower target expression translated into 3–6 fold lower levels of IFNγ and more than 100 fold lower granzyme B production by redirected T cells and these melanocytes were resistant to direct tebentafusp-induced killing (EC50 for melanocytes greater than 1nM vs EC50 melanoma cell lines of 23–50 pM). Supernatants from T cells activated in response to melanoma cancer cells by tebentafusp downregulated the melanin content of healthy melanocytes (20–30% reduction). Western blotting revealed 30–40% inhibition of two key components of the melanin synthesis pathway; the tyrosinase-related protein (TRP)-1 and TRP-2. This inhibition was reversed by blocking IFNγ in supernatants from activated T cells. Conclusions MRAEs, especially vitiligo, associated with response to tebentafusp, may be explained, at least in part, by the downregulation of melanin biosynthesis pathway genes by IFNγ secreted by tebentafusp-activated T cells. Ethics Approval The study was approved by the South Central - Oxford A Research Ethics Committee (UK), REC reference 13/SC/0226 References Middleton, et al., Relationship between clinical efficacy and AEs of IMCgp100, a novel bispecific TCR–anti-CD3, in patients with advanced melanoma. Journal of Clinical Oncology. 2019. Orloff, et al., Vitiligo and other clinical melanocyte-related adverse events following tebentafusp (IMCgp100) exposure in patients with uveal melanoma. AACR (American Association for Cancer Research), 2020.

Background Cyclic dinucleotides (CDN) – agonists of stimulator of interferon genes – can initiate potent anti-tumor immunity by activating antigen presenting cells which prime CD8+ T cells.1 Recent studies have also highlighted CDN activation of NK cells via IL-15 in T cell-resistant tumors.2 Thus far, limited analysis has been made of the impact of CDN-based therapies on cancer metastasis. We employed a surgical resection model of metastatic mammary carcinoma to examine the effects of surgery – a predominant breast cancer intervention – and lung metastasis on neoadjuvant therapy with CDNs combined with other clinically-relevant immunotherapies including IL-2 and anti-PD-1.3 Methods 4T1-luciferase cells were inoculated in the mammary fat pad, palpable tumors were treated with immunotherapy starting eight days later, any remaining primary tumor was surgically resected on day 17, and metastases were monitored by luciferase imaging. Combinations of intratumoral bisphosphorothioate 2’3’ c-di-AMP (CDN), intraperitoneal (i.p.) albumin-IL2 fusion protein (Alb-IL2), and i.p. anti-PD-1 were tested in this model by measuring primary tumor growth and monitoring overall survival. CD8+ T cells, CD4+ T cells, or NK cells were depleted using anti-CD8 (2.43), anti-CD4 (GK1.5), and anti-asialo-GM1 antibodies, respectively, administered i.p. every 3 days beginning one day prior to treatment initiation. Immunophenotyping of primary tumors and lungs was conducted at several timepoints after starting therapy. Results In mice bearing orthotopic 4T1-luciferase tumors, administration of three doses of CDN resulted in no cures in the absence of surgical resection. When administered prior to surgical resection CDN monotherapy yields a 20% cure rate and enhanced median overall survival compared to untreated mice (median survival 44.5 days vs 38 days, p=0.0026). Combination of CDN with Alb-IL2 and anti-PD-1 substantially improved survival, with 60% of mice surviving long-term. Through cellular depletions we determined that neither CD8+ nor CD4+ T cells were required for efficacy in this neoadjuvant therapy model, while NK cell depletion decreased survival rate by approximately 50%. Lung immunophenotying of CDN/Alb-IL-2/anti-PD-1-treated mice revealed a near doubling of the absolute NK cell count compared to untreated controls. More strikingly, lung infiltrating NK cells in the CDN/Alb-IL2/anti-PD-1 cohort exhibited prolonged granzyme B production compared to CDN monotherapy (6.24x higher after 6 days) and Alb-IL2 monotherapy (25x higher after 6 days) cohorts. Conclusions Our findings suggest that combining intratumoral CDN with systemic Alb-IL2 and anti-PD-1 can delay the growth of primary breast tumors and limit metastatic outgrowth in the lungs. Efficacy is attributed to sustained cytotoxicity of NK cells. Ethics Approval All mouse experiments were approved by MIT’s Committee on Animal Care, protocol #0720-070-23. References Corrales L, et al. Direct activation of STING in the tumor microenvironment leads to potent and systemic tumor regression and immunity. Cell Reports 2015; 11:1018–30. Nicolai CJ, et al. NK cells mediate clearance of CD8+ T cell-resistant tumors in response to STING agonists. Science Immunology 2020; 5:eaaz2738. Al-Sahaf O, et al. Surgical injury enhances the expression of genes that mediate breast cancer metastasis to the lung. Ann Surg 2010; 252:1037–43.

Background Subunit vaccines targeting tumor antigens have shown limited capacity for expanding cytotoxic T-cells against tumors in the clinic. Especially in the case of KRAS-driven tumors, responses elicited by conventional vaccines have been exceedingly weak. For molecular immunogens including peptides and oligonucleotides, inefficient delivery to immune cells residing in the lymphatics is a significant challenge limiting their ability to induce cancer-directed immune responses of sufficient strength and functionality to impact tumors. Improving the targeting of immunogens to lymph nodes (LN), where resident immune cells potently orchestrate immunity, can substantially amplify their ability to induce effective tumor-directed immunity. Here, we demonstrate such an approach for significantly enhancing mKRAS-directed T-cell responses by precisely targeting antigens and adjuvants directly to the draining LN through a simple one-step conjugation to albumin-binding lipids. These amphiphilic conjugates (‘Amphiphiles’, or AMP) then ‘hitch-hike’ on albumin into the LNs where they elicit strong immune responses. LN accumulation of structurally optimized amphiphiles in mice is greatly improved over soluble equivalents. Methods C57BL/6J mice received two or more doses of benchmark or amphiphile-modified vaccines, comprised of mKRAS peptide and CpG adjuvant, subcutaneously injected into the tail base in two-week intervals. Immunological readouts were performed 7 days post dosing. For ELISpot analysis of IFNγ and Granzyme B production and flowcytometric bead array analysis of Th1/2 cytokines, splenocytes were harvested and re-stimulated with antigen overnight. In vivo, cytolytic capabilities of antigen-specific T-cells were evaluated by pulsing CFSE-stained splenocytes from naive mice with mKRAS antigen and injecting these cells intravenously into immunized mice. Recovery of CFSE-labeled target cells from immunized mice was performed 24h later and analyzed flowcytometrically. Results We show robust immune responses that yield strong activation against all common mutations in the mKRAS protein compared to low or undetectable responses generated by soluble or benchmark treatments. Further, this response is composed of CD4+ as well as CD8+ T-cells resulting in the production of high levels of TH1-associated cytokines upon re-stimulation with mKRAS-specific peptides in vitro. In vivo, robust cytolytic function towards mKRAS-presenting targets can be measured in T-cells. Conclusions By targeting immunogens directly and precisely to the LNs, the Amphiphile platform can significantly amplify the potency of subunit vaccines. In the case of mKRAS, substantially improved cytolytic immune responses represent a promising therapeutic strategy for targeting mKRAS-driven tumor growth and survival in a large fraction of human tumors. Furthermore, this platform technology is simple, rapid and scalable for broad clinical application.

Background An effective vaccine that prevents disease caused by hantaviruses is a global public health priority, but up to now, no vaccine has been approved for worldwide use. Therefore, novel vaccines with high prophylaxis efficacy are urgently needed. Methods Herein, we designed and synthesized Hantaan virus (HTNV) linear multi-epitope peptide consisting of HLA-A*02-restricted HTNV cytotoxic T cell (CTL) epitope and pan HLA-DR-binding epitope (PADRE), and evaluated the immunogenicity, as well as effectiveness, of multi-epitope peptides in HLA-A2.1/Kb transgenic mice with interferon (IFN)-γ enzyme-linked immunospot assay, cytotoxic mediator detection, proliferation assay and HTNV-challenge test. Results The results showed that a much higher frequency of specific IFN-γ-secreting CTLs, high levels of granzyme B production, and a strong proliferation capacity of specific CTLs were observed in splenocytes of mice immunized with multi-epitope peptide than in those of a single CTL epitope. Moreover, pre-immunization of multi-epitope peptide could reduce the levels of HTNV RNA loads in the liver, spleen and kidneys of mice, indicating that specific CTL responses induced by multi-epitope peptide could reduce HTNV RNA loads in vivo. Conclusions This study may provide an important foundation for the development of novel peptide vaccines for HTNV prophylaxis.

Infections with respiratory syncytial virus (RSV) occurs repeatedly throughout life because sustained, protective memory responses fail to develop. Why this occurs is not known. During RSV infection the recognition of the virus via the cytosolic RIG-I like receptors and signaling via the adaptor protein MAVS is crucial for mounting an innate immune response. However, if this signaling pathway is important for T cell responses during primary infection and during re-infection is not fully elucidated. We describe a second peak of pro-inflammatory mediators during the primary immune response to RSV that coincides with the arrival of T cells into the lung. This second peak of cytokines/chemokines is regulated differently than the early peak and is largely independent of signaling via MAVS. This was concurrent with Mavs -/- mice mounting a strong T cell response to primary RSV infection, with robust IFN-γ; and Granzyme B production. However, after RSV re-infection, Mavs -/- mice showed fewer CD4+ and CD8+ short term memory T cells and their capacity to produce IFN-γ; and Granzyme B, was decreased. In sum, cytosolic recognition of RSV is important not only for initiating innate anti-viral responses but also for generating or maintaining efficient, short term T cell memory responses.

The induction of exhaustion on effector immune cells is an important limiting factor for cancer immunotherapy efficacy as these cells undergo a hierarchical loss of proliferation and cytolytic activity due to chronic stimulation. Targeting PD-1 has shown unprecedented clinical benefits for many cancers, which have been attributed to the prevention of immune suppression and exhaustion with enhanced anti-tumor responses. In this study, we sought to evaluate the role of the PD-1/PD-L1 pathway in murine natural killer (NK) cell activation, function, and exhaustion. In an in vivo IL-2-dependent exhaustion mouse model, neutralization of the PD-1/PD-L1 pathway improved NK cell activation after chronic stimulation when compared to control-treated mice. These cells displayed higher proliferative capabilities and enhanced granzyme B production. However, the blockade of these molecules during long-term in vitro IL-2 stimulation did not alter the progression of NK cell exhaustion (NCE), suggesting an indirect involvement of PD-1/PD-L1 on NCE. Given the expansion of CD8 T cells and regulatory T cells (Tregs) observed upon acute and chronic stimulation with IL-2, either of these two populations could influence NK cell homeostasis after PD-L1/PD-1 therapy. Importantly, CD8 T cell activation and functional phenotype were indeed enhanced by PD-1/PD-L1 therapy, particularly with anti-PD-1 treatment that resulted in the highest upregulation of CD25 during chronic stimulation and granted an advantage for IL-2 over NK cells. These results indicate a competition for resources between NK and CD8 T cells that arguably delays the onset of NCE rather than improving its activation during chronic stimulation. Supporting this notion, the depletion of CD8 T cells reversed the benefits of PD-1 therapy on chronically stimulated NK cells. These data suggest a bystander effect of anti-PD1 on NK cells, resulting from the global competition that exists between NK and CD8 T cells for IL-2 as a key regulator of these cells' activation. Thus, achieving an equilibrium between these immune cells might be important to accomplish long-term efficacy during anti-PD-1/IL-2 therapy.

Tumor neantigens (TNAs) and tumor-associated antigens (TAAs) are crucial triggers of anticancer immune responses. Through major histocompatibility complex, such antigens activate T cells, which, by releasing interferon gamma (IFN-γ) and granzyme B (GRZB), act as crucial effectors against tumor onset and progression. However, in response to immune pressure, cancer cells use different strategies to favor the establishment of an immunosuppressive tumor microenvironment (TME). Elucidating the dynamics of tumor-host co-evolution provides novel opportunities for personalized cancer immunotherapies. The in sitro (in vitro+in situ) technology is an experimental approach involving the preparation of heterocellular cell suspensions from fresh tumors and their use in vitro. The in sitro experimental setup offers the possibility to (1) analyze immune-related parameters (e.g., quantification of cytokines released in the TME), (2) reveal the mechanism of action of drugs, and (3) unveil crucial cell-intrinsic and cell-extrinsic processes boosting anticancer immune responses. Nonetheless, the in sitro technology does not fully recapitulate the complexity of the tissue "in situ" nor models the patterns of infiltrating immune cell localization, and hence parallel experimentation should be scheduled. In this chapter we discuss in sitro technology to analyze and quantify IFN-γ and GRZB production by T cells either co-cultured with cancer cells in the presence of exogenous adjuvant stimuli (i.e., an antibody targeting the immune checkpoint programmed cell death protein 1, and recombinant calreticulin) and boosting with TAAs (i.e., the model SIINFEKL ovalbumin antigen). Specifically, we describe IFN-γ and GRZB quantification by flow cytometry, ELISA and ELISpot technologies.

Background The effects of the widely used progestin-only injectable contraceptives, medroxyprogesterone acetate (MPA) and norethisterone acetate (NET-A), on host susceptibility to Mycobacterium tuberculosis (Mtb) are unknown. Methods We recruited human immunodeficiency virus–uninfected females, not taking any contraceptives, from Cape Town, South Africa, to evaluate the effect of MPA, NET-A, and dexamethasone on Mtb containment in monocyte-derived macrophages co-incubated with purified protein derivative (PPD)–driven peripheral blood–derived effector cells. Results MPA (P < .005) and dexamethasone (P < .01), but not NET-A, significantly attenuated Mtb containment in Mtb-infected macrophages co-cultured with PPD-driven effector cells at physiologically relevant concentrations and in a dose-dependent manner. Antagonizing the glucocorticoid receptor with mifepristone (RU486) abrogated the reduction in Mtb containment. In PPD-stimulated peripheral blood mononuclear cells, MPA and dexamethasone, but not NET-A, upregulated (median [interquartile range]) regulatory T cells (5.3% [3.1%–18.2%]; P < .05), reduced CD4+ T-cell interferon-γ (21% [0.5%–28%]; P < .05) and granzyme B production (12.6% [7%–13.5%]; P < .05), and reduced CD8+ perforin activity (2.2% [0.1%–7%]; P < .05). RU486 reversed regulatory T-cell up-regulation and the inhibitory effect on Th1 and granzyme/perforin-related pathways. Conclusions MPA, but not NET-A, subverts mycobacterial containment in vitro and downregulates pathways associated with protective CD8+- and CD4+-related host immunity via the glucocorticoid receptor. These data potentially inform the selection and use of injectable contraceptives in tuberculosis-endemic countries., Injectable contraceptive usage is high in tuberculosis (TB)–endemic countries, and their effect on TB pathogenesis in humans has not been investigated. At physiological concentrations, medroxyprogesterone acetate, but not norethisterone acetate, attenuates Mycobacterium tuberculosis containment and antagonizes pathways associated with protective host immunity through glucocorticoid receptor–mediated mechanisms.

The role of mitochondrial biogenesis during naive to effector differentiation of CD8+ T cells remains ill explored. In this study, we describe a critical role for early mitochondrial biogenesis in supporting cytokine production of nascent activated human naive CD8+ T cells. Specifically, we found that prior to the first round of cell division activated naive CD8+ T cells rapidly increase mitochondrial mass, mitochondrial respiration, and mitochondrial reactive oxygen species (mROS) generation, which were all inter-linked and important for CD8+ T cell effector maturation. Inhibition of early mitochondrial biogenesis diminished mROS dependent IL-2 production - as well as subsequent IL-2 dependent TNF, IFN-γ, perforin, and granzyme B production. Together, these findings point to the importance of mitochondrial biogenesis during early effector maturation of CD8+ T cells.

Human regulatory dendritic cells (DCreg) were generated from CD14 immunobead-purified or elutriated monocytes in the presence of vitamin D3 and IL-10. They exhibited similar, low levels of costimulatory CD80 and CD86, but comparatively high levels of co-inhibitory programed death ligand-1 (PD-L1) and IL-10 production compared to control immature DC (iDC). Following Toll-like receptor 4 ligation, unlike control iDC, DCreg resisted phenotypic and functional maturation and further upregulated PD-L1:CD86 expression. Whereas LPS-stimulated control iDC (mature DC; matDC) secreted pro-inflammatory tumor necrosis factor but no IL-10, the converse was observed for LPS-stimulated DCreg. DCreg weakly stimulated naive and memory allogeneic CD4+ and CD8+ T cell proliferation and IFNγ, IL-17A and perforin/granzyme B production in MLR. Their stimulatory function was enhanced however, by blocking PD-1 ligation. High-throughput T cell receptor (TCR) sequencing revealed that, among circulating T cell subsets, memory CD8+ T cells contained the most alloreactive TCR clonotypes and that, while matDC expanded these alloreactive memory CD8 TCR clonotypes, DCreg induced more attenuated responses. These findings demonstrate the feasibility of generating highly-purified GMP-grade DCreg for systemic infusion, their influence on the alloreactive T cell response, and a key mechanistic role of the PD1 pathway.

BackgroundNL-201 is a potent, selective, and long-acting computationally designed alpha-independent agonist of the IL-2 and IL-15 receptors that is being developed as an immunotherapy for cancer. Downregulation of MHC class I (MHC-I) expression by tumors is a well-known mechanism of immune escape, and IFNγ is known to upregulate MHC-I. Here, we investigated whether NL-201 monotherapy can convert a 'cold' tumor microenvironment (TME) to an immunologically 'hot' TME through IFNγ-mediated MHC-I expression. This effect could expand the TCR repertoire for increased antitumor response and improve anti-PD-1 combination therapy.MethodsFor in vitro assays, mouse splenocytes were cultured with Neo-2/15 to assess effector cell function, as well as co-cultured with B16F10 cells to assess IFNγ-induced MHC-I and PD-L1 expression. B16F10 tumors were established in C57BL/6 mice and dosed with NL-201, anti-PD-1, or both to assess in vivo efficacy. B16F10 tumors were excised and dissociated for phenotyping of tumor-infiltrating lymphocytes (TILs) using flow cytometry. For gene expression analysis, RNA and genomic DNA were extracted from tumors and submitted for NanoString Pancancer Immune Profiling and Adaptive ImmunoSEQ analysis, respectively.ResultsIn vitro, Neo-2/15 induced greater CD8+ T cell and NK cell proliferation, as well as granzyme B production and IFNγ-dependent MHC-I upregulation on B16F10 tumor cells, compared to IL-2 or IL-15. In 'cold' B16F10 syngeneic tumors, NL-201 monotherapy reduced tumor growth and induced MHC-I, IFNγ, and granzyme B upregulation. Gene expression analysis of NL-201–treated tumors demonstrated increased TCR repertoire diversity and inflammatory signature at the tumor. In addition, PD-L1 was significantly upregulated on B16F10 cells. While the B16F10 tumors exhibited resistance to anti-PD-1 monotherapy, combination treatment with NL-201 significantly improved anti-PD-1 activity. This may explain the potent anti-tumor activity of NL-201 with anti-PD-1 combination therapy.ConclusionsNL-201 induces potent inflammatory effects on effector cells and is able to turn 'cold' TMEs 'hot'. We demonstrate that NL-201 strongly upregulated MHC-I expression in vitro and in vivo via an IFNγ-dependent pathway. Increased antigen presentation drives TCR diversity while augmenting the inflammatory signature at the tumor. This adaptive response also upregulates PD-L1 expression and results in impressive antitumor activity when NL-201 and PD-1 inhibitors are co-administered. The demonstration that NL-201 can convert 'cold' tumors to immunologically 'hot' tumors may provide a novel therapeutic option for patients unresponsive to current standard of care checkpoint inhibitors. A Phase 1 study of NL-201 in patients with advanced solid tumors is currently underway (NCT04659629).Ethics ApprovalAll experiments were approved by the Institutional Animal Care and Use Committee of Bloodworks Northwest and performed under protocol 5360-03.

Inhibition of specific Akt isoforms in CD8+ T cells promotes favored differentiation into memory versus effector cells, the former of which are superior in mediating antitumor immunity. In this study, we investigated the role of upstream PI3K isoforms in CD8+ T-cell differentiation and assessed the potential use of PI3K isoform–specific inhibitors to favorably condition CD8+ T cells for adoptive cell therapy. The phenotype and proliferative ability of tumor antigen–specific CD8+ T cells was assessed in the presence of PI3K-α, -β, or -δ inhibitors. Inhibition of PI3K-δ, but not PI3K-α or PI3K-β, delayed terminal differentiation of CD8+ T cells and maintained the memory phenotype, thus enhancing their proliferative ability and survival while maintaining their cytokine and granzyme B production ability. This effect was preserved in vivo after ex vivo PI3K-δ inhibition in CD8+ T cells destined for adoptive transfer, enhancing their survival and also the antitumor therapeutic activity of a tumor-specific peptide vaccine. Our results outline a mechanism by which inhibitions of a single PI3K isoform can enhance the proliferative potential, function, and survival of CD8+ T cells, with potential clinical implications for adoptive cell transfer and vaccine-based immunotherapies. Cancer Res; 77(15); 4135–45. ©2017 AACR.

Innate lymphoid cells (ILCs) represent a distinct branch of the lymphoid lineage composed of 3 major subpopulations: ILC1, ILC2, and ILC3. ILCs are mainly described as tissue-resident cells but can be detected at low levels in human blood. However, unlike mouse ILCs, there is still no consistent methodology to purify and culture these cells that enables in-depth analysis of their intrinsic biology. Here, we describe defined culture conditions for ILC2s, which allowed us to dissect the roles of interleukin 2 (IL-2), IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) individually, or in combination, in modulating ILC2 phenotype and function. We show that TSLP is important for ILC2 survival, while ILC2 activation is more dependent on IL-33, especially when in combination with IL-2 or TSLP. We found that activation of ILC2s by IL-33 and TSLP dramatically upregulated their surface expression of c-Kit and downregulated expression of the canonical markers IL-7Rα and CRTH2. IL-2 further amplified ILC2 production of IL-5, IL-13, and granulocyte-macrophage colony-stimulating factor but also induced a more natural killer (NK)-like phenotype in ILC2, with upregulation of granzyme B production by these cells. Furthermore, ILC2 plasticity was observed in serum-free SFEM II media in response to IL-33, IL-25, and TSLP stimulation and independently of IL-12 and IL-1β. This is the first comprehensive report of an in vitro culture system for human ILC2s, without the use of feeder layers, which additionally evaluates the impact of IL-25, IL-33, and TSLP alone or in combination on ILC2 surface phenotype and activation status.

Drug-induced liver injury (DILI) is a growing problem. Diagnostic methods to differentiate DILI caused by an adaptive immune response from liver injury of other causes or to identify the responsible drug in patients receiving multiple drugs, herbals and/or dietary supplements (polypharmacy) have not yet been established. The lymphocyte transformation test (LTT) has been proposed as a diagnostic method to determine if a subject with an apparent hypersensitivity reaction has become sensitized to a specific drug. In this test, peripheral blood mononuclear cells (PBMC) collected from a subject are incubated with drug(s) suspected of causing the reaction. Cell proliferation, measured by the incorporation of [3H]-thymidine into new DNA, is considered evidence of a drug-specific immune response. The objectives of the current studies were to: (1) develop and optimize a modified version of the LTT (mLTT) and (2) investigate the feasibility of using the mLTT for diagnosing DILI associated with an adaptive immune response and identifying the responsible drug. PBMC collected from donors with a history of drug hypersensitivity reactions to specific drugs (manifested as skin rash) were used as positive controls for assay optimization. Following optimization, samples collected from 24 subjects enrolled in the U.S. Drug-Induced Liver Injury Network (DILIN) were tested in the mLTT. Using cytokine and granzyme B production as the primary endpoints to demonstrate lymphocyte sensitization to a specific drug, most samples from the DILIN subjects failed to respond. However, robust positive mLTT responses were observed for two of four samples from three DILIN subjects with hepatitis due to isoniazid (INH). We conclude that the mLTT, as performed here on frozen and thawed PBMC, is not a reliable test for diagnosing DILI caused by all drugs, but that it may be useful for confirming the role of the adaptive immune response in DILI ascribed to INH.

Type I IFNs are key mediators of immune defense against viruses and bacteria. Type I IFNs were also previously implicated in protection against fungal infection, but their roles in antifungal immunity have not been thoroughly investigated. A recent study demonstrated that bacterial and fungal β-glucans stimulate IFN-β production by dendritic cells (DCs) following detection by the Dectin-1 receptor, but the effects of β-glucan–induced type I IFNs have not been defined. We investigated whether type I IFNs regulate CD8 T cell activation by fungal β-glucan particle–stimulated DCs. We demonstrate that β-glucan–stimulated DCs induce CD8 T cell proliferation, activation marker (CD44 and CD69) expression, and production of IFN-γ, IL-2, and granzyme B. Moreover, we show that type I IFNs support robust CD8 T cell activation (proliferation and IFN-γ and granzyme B production) by β-glucan–stimulated DCs in vitro and in vivo due to autocrine effects on the DCs. Specifically, type I IFNs promote Ag presentation on MHC I molecules, CD86 and CD40 expression, and the production of IL-12 p70, IL-2, IL-6, and TNF-α by β-glucan–stimulated DCs. We also demonstrate a role for autocrine type I IFN signaling in bacterial LPS-induced DC maturation, although, in the context of LPS stimulation, this mechanism is not so critical for CD8 T cell activation (promotes IFN-γ production but not proliferation or granzyme B production). This study provides insight into the mechanisms underlying CD8 T cell activation during infection, which may be useful in the rational design of vaccines directed against pathogens and tumors.

The B-cell maturation antigen (BCMA) is an immunotherapy target selectively expressed on multiple myeloma cells (MM). Despite recent success of experimental BCMA CAR-T cell therapy, clinical remissions in MM are often short, in part due to low persistence of the BCMA CAR-T cells. Additionally, immunosuppressive factors, notably TGF-β, are known to be elevated in the peripheral blood and tumor microenvironment in the bone marrow of MM patients, potentially contributing to the lack of durability of CAR-T cell therapy. We aimed to develop a fully-human BCMA CAR with long-term persistence and functional resistance to the suppressive effects of TGF-β. Initially, two fully human single chain variable fragments (scFv) specific for BCMA, derived by biopanning of a yeast display human scFv library, were characterized in a CAR format. Each of the two scFvs was cloned into a lentiviral vector CAR backbone, comprised of the CD8 hinge and transmembrane domain, 4-1BB co-stimulatory domain and CD3ζ signaling domain, and termed BCMA1 and BCMA2, respectively. BCMA2 and BCMA1 T cells, generated by lentiviral vector transduction of primary human T cells, exhibited high CAR expression at multiplicities of infection 10 to 40 (BCMA1: 64-81%; BCMA2: 84-94%), and consistently demonstrated potent cytotoxicity in an overnight co-culture with BCMA+ MM cell lines RPMI-8226 and MM1.S, but not the BCMA- 293T cells. BCMA2 CAR showed robust proliferative capacity in response to repeated, long-term exposure to MM1.S target cells, concordant with the sustained CD4 T-cell subset and high IL-2 production during the course of repeated exposure to target cells. This is in contrast to BCMA1, that showed precipitous decrease in CD4+ T-cell subset upon co-culture with MM cells, resulting in a CAR T-cell population dominated by CD8+ T-cells. Furthermore, the BCMA2 demonstrated prolonged potency in clearing tumor cells compared to BCMA1, even after continuous 20-day exposure to target cells. This was further confirmed in a mouse intradermal RPMI-8226 xenograft tumor model, in which infusion of BCMA2 T-cells resulted in the rapid and complete eradication of tumors, while BCMA1 showed a slower decline in tumor burden. To further improve the efficacy of the BCMA2, specifically within the TGF-β-rich immunosuppressive tumor microenvironment, we developed an armored BCMA2 CAR variant, which co-expresses the dominant negative TGF-β RII bicistronically via a 2A sequence (BCMA2-TbnegCAR). In a 10 day-long co-culture assay with MM1.S targets in the presence of spiked 10 ng/ml TGF-β, BCMA2-TbnegCAR retained high proliferative capacity and potent cytotoxicity, while the unarmored BCMA2 had diminished proliferation and substantially reduced cytokine and granzyme B production. Consistently, in the in vivo intradermal tumor model that utilizes RPMI-8226, which is a MM cell line that endogenously produces TGF-β, we observed that BCMA2-TbnegCAR treatment resulted in higher T-cell counts in the tumors and an earlier decrease of tumor burden compared to infusion with BCMA2, further demonstrating the increased efficacy and potency of the BCMA2-TbnegCAR. In conclusion, we have designed and characterized a new fully-human BCMA2-TbnegCAR, with a novel scFv that exhibits robust proliferative capacity and persistent cytotoxicity, and remains functionally resistant to the immunosuppressive effects of TGF-β. This novel BCMA CAR can potentially improve the effectiveness and durability of the current BCMA CAR-T cell therapy. Disclosures Alabanza: Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Vu:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Wu:Lentigen, a Miltenyi Biotec Company: Current Employment. Zhu:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Dropulic:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties: CAR-T immunotherapy. Schneider:Lentigen, a Miltenyi Biotec Company: Current Employment, Patents & Royalties.

Background Multiple myeloma (MM) is a lymphoid neoplasm characterized by the accumulation of malignant clones of plasma cells, usually within the bone marrow (BM). Despite the increase of T cells expressing inhibitory signal molecules (ISMs) — PD-1, TIM-3 etc. — having been described in MM, the first results of anti-PD-1 therapy for MM remain modest. ISMs are expressed on T cells and modulate the functional activity. A stable expression of ISMs on T cells is associated with T cell exhaustion, the condition of severe decrease of both cytotoxicity and cytokine secretion. At the same time, ISMs are also expressed by activated T cells. We studied the expression of PD-1 and TIM-3 by circulating and bone marrow (BM) T cells as a manifestation of T cell exhaustion treated MM patients. Methods Peripheral blood (PB) and BM samples of 45 MM patients were obtained during routine diagnostic procedures. The expression of PD-1 and TIM-3 by CD4+ and CD8+ T cells, intracellular production of IFNγ and intracellular expression of Ki-67 by T cells and Granzyme B production by CD8+ T cells were assessed using flow cytometry. Results Relative counts of PD-1+ subset of CD8+ T cells and both PD-1+ and TIM-3+ subsets of CD4+ T cells were higher in BM compared with PB. BM samples also contained higher amounts of double-positive PD-1+TIM-3+ subsets of CD8+ and CD4+ T cells compared with PB. Percentage of PB CD8+PD-1+, CD4+PD-1+, CD4+TIM-3+, CD8+PD-1+TIM-3+ and CD4+PD-1+TIM-3+ T cells correlated with the content of respective subsets in BM. Both PB and BM CD8+PD-1+ and CD4+PD-1+ T cells of MM patients retain a cytotoxic, proliferative and cytokine-producing potential appropriate to PD-1-negative subsets. On the contrary, the functional activity of CD8+PD-1+TIM-3+ and CD4+PD-1+TIM-3+ T cells was significantly reduced compared with PD-1- and TIM-3-negative subsets. Conclusion PD-1+ T cells in MM patients are related to activated rather than exhausted populations. T cell exhaustion is associated with cells co-expressing PD-1 and TIM-3. It is recommended to evaluate T cell subsets co-expressing PD-1, TIM-3 and other ISMs, and to study their functional properties. Legal entity responsible for the study The authors. Funding The Russian Science Foundation (grant no. 18-75-00050). Disclosure All authors have declared no conflicts of interest.

On the basis of the autologous tumor-infiltrating lymphocytes (TILs) or genetically modified TILs for adoptive cell therapy have received more attention. Programmed cell death protein 1 (PD-1) expression on the T cells exert complex response during the tumor immune response. But the composition and function of PD-1T-cell subsets in TILs from human lung cancer still limited. In blood and TILs from human lung cancer patients, we confirmed that PD-1 is expressed in higher levels in CD4T-cell subsets than in CD8T-cell subsets. To further analyze the function of PD-1T cells in TILs, we observed the cytokine production in different T-cell subsets. We found that higher interferon-γ and granzyme B production in CD4/CD8PD-1T-cell subsets in TILs than in peripheral blood mononuclear cells (PBMCs); except for PD-1Tscm, higher tumor necrosis factor-α production was observed in PD-1T-cell subsets in TILs than in PBMCs; the expression level of interleukin-17 were lower in PD-1T cells in TILs than in PBMCs; and perforin expression was significantly reduced in CD4PD-1T cells subsets in TILs compared with peripheral blood. Clarify elucidating the composition and function of PD-1T-cell subsets in TILs will have great value in clinical application for evaluating the sensitivity to PD-1 blockade and selecting the promising candidate T-cell subsets in TILs for combination immunotherapy in human lung cancer.

Multiple Myeloma (MM) is preceded by the clinically stable condition monoclonal gammopathy of undetermined significance (MGUS). Critical immune events that discriminate MGUS from newly diagnosed MM (ND)MM patients remain unknown, but may involve changes in the regulatory T cell (Treg) compartment that favor myeloma growth. To address this possibility, we used mass cytometry and the unsupervised clustering algorithm Flow self-organizing map (FlowSOM) to interrogate the distribution of multiple subsets within CD25+CD127low/negTreg in matched bone marrow (BM) and peripheral blood (PB) of MGUS and NDMM patients. Both mass cytometry and flow cytometry confirmed a trend toward prevalence of CD39-Treg within the Treg compartment in BM and PB of NDMM patients compared to CD39-Treg in MGUS patients. FlowSOM clustering displayed a phenotypic organization of Treg into 25 metaclusters that confirmed Treg heterogeneity. It identified two subsets which emerged within CD39-Treg of NDMM patients that were negligible or absent in CD39-Treg of MGUS patients. One subset was found in both BM and PB which phenotypically resembled activated Treg based on CD45RO, CD49d, and CD62L expression; another subset resembled BM-resident Treg based on its tissue-resident CD69+CD62L-CD49d- phenotype and restricted location within the BM. Both subsets co-expressed PD-1 and TIGIT, but PD-1 was expressed at higher levels on BM-resident Treg than on activated Treg. Within BM, both subsets had limited Perforin and Granzyme B production, whilst activated Treg in PB acquired high Perforin and Granzyme B production. In conclusion, the use of mass cytometry and FlowSOM clustering discovered two discrete subsets of CD39-Treg which are discordant in MGUS and NDMM patients and may be permissive of myeloma growth which warrants further study. Understanding the regulatory properties of these subsets may also advance MGUS and MM diagnosis, prognosis, and therapeutic implications for MM patients.

Mucosal associated invariant T (MAIT) cells are abundant unconventional T cells which can be stimulated either via their T cell receptor (TCR) or by innate cytokines. The MAIT cell TCR recognises a pyrimidine ligand, derived from riboflavin synthesising bacteria, bound to MR1. In infection, bacteria not only provide the pyrimidine ligand but also co-stimulatory signals, such as Toll-like receptor agonists, that can modulate TCR-mediated activation. Recently, type I interferons (T1-IFNs) have been identified as contributing to cytokine-mediated MAIT cell activation. However, it is unknown whether T1-IFNs also have a role during TCR-mediated MAIT cell activation. In this study, we investigated the co-stimulatory role of T1-IFNs during TCR-mediated activation of MAIT cells by the MR1 ligand 5-amino-6-D-ribitylaminouracil/methylglyoxal (5-A-RU/MG). We found that T1-IFNs were able to boost interferon-γ and granzyme B production in 5-A-RU/MG-stimulated MAIT cells. Similarly, influenza virus-induced T1-IFNs enhanced TCR-mediated MAIT cell activation. An essential role of T1-IFNs in regulating MAIT cell activation by riboflavin synthesising bacteria was also demonstrated. The co-stimulatory role of T1-IFNs was confirmed using liver-derived MAIT cells. T1-IFNs acted directly on MAIT cells to enhance their response to TCR stimulation. Overall, our findings establish an important immunomodulatory role of T1-IFNs during TCR-mediated MAIT cell activation.

Abstract Interleukin-15 (IL-15) is a cytokine critical for maintenance of intestinal intra-epithelial lymphocytes (IELs), especially CD8αα + IELs (CD8αα IELs). In the intestine, IL-15 is produced by intestinal epithelial cells (IECs), blood vascular endothelial cells (BECs) and hematopoietic cells. However, the precise role of intestinal IL-15 on IELs is still unknown. To address the question, we generated two kinds of IL-15 conditional knockout (IL-15cKO) mice: villin-Cre (Vil-Cre) and Tie2-Cre IL-15cKO mice. IEC-derived IL-15 was specifically deleted in Vil-Cre IL-15cKO mice, whereas IL-15 produced by BECs and hematopoietic cells was deleted in Tie2-Cre IL-15cKO mice. The cell number and frequency of CD8αα IELs and NK IELs were significantly reduced in Vil-Cre IL-15cKO mice. By contrast, CD8αα IELs were unchanged in Tie2-Cre IL-15cKO mice, indicating that IL-15 produced by BECs and hematopoietic cells is dispensable for CD8αα IELs. Expression of an anti-apoptotic factor, Bcl-2, was decreased, whereas Fas expression was increased in CD8αα IELs of Vil-Cre IL-15cKO mice. Forced expression of Bcl-2 by a Bcl-2 transgene partially restored CD8αα IELs in Vil-Cre IL-15cKO mice, suggesting that some IL-15 signal other than Bcl-2 is required for maintenance of CD8αα IELs. Furthermore, granzyme B production was reduced, whereas PD-1 expression was increased in CD8αα IELs of Vil-Cre IL-15cKO mice. These results collectively suggested that IEC-derived IL-15 is essential for homeostasis of IELs by promoting their survival and functional maturation.

Mucosal associated invariant T (MAIT) cells are abundant unconventional T cells that can be stimulated either via their TCR or by innate cytokines. The MAIT cell TCR recognises a pyrimidine ligand, derived from riboflavin synthesising bacteria, bound to MR1. In infection, bacteria not only provide the pyrimidine ligand but also co-stimulatory signals, such as TLR agonists, that can modulate TCR-mediated activation. Recently, type I interferons (T1-IFNs) have been identified as contributing to cytokine-mediated MAIT cell activation. However, it is unknown whether T1-IFNs also have a role during TCR-mediated MAIT cell activation. In this study, we investigated the co-stimulatory role of T1-IFNs during TCR-mediated activation of MAIT cells by the MR1 ligand 5-amino-6-d-ribitylaminouracil/methylglyoxal. We found that T1-IFNs were able to boost interferon-γ and granzyme B production in 5-amino-6-d-ribitylaminouracil/methylglyoxal-stimulated MAIT cells. Similarly, influenza virus-induced T1-IFNs enhanced TCR-mediated MAIT cell activation. An essential role of T1-IFNs in regulating MAIT cell activation by riboflavin synthesising bacteria was also demonstrated. The co-stimulatory role of T1-IFNs was also evident in liver-derived MAIT cells. T1-IFNs acted directly on MAIT cells to enhance their response to TCR stimulation. Overall, our findings establish an important immunomodulatory role of T1-IFNs during TCR-mediated MAIT cell activation.

Apart from their activity in combating infections, neutrophils play an important role in regulating the tumor microenvironment. Neutrophils can directly kill (antibody-coated) cancer cells, and support other immune anti-tumoral strategies. On the other hand, neutrophils can also exert pro-tumorigenic activities via the production of factors which promote cancer growth, angiogenesis and metastasis formation. The balance of anti- and pro-cancer activity is influenced by the particularly delicate interplay that exists between neutrophils and T lymphocytes. In murine models, it has been reported that γδ T cells are a major source of IL-17 that drives the recruitment and pro-tumorigenic differentiation of neutrophils. This, however, contrasts with the well-studied anti-tumor activity of γδ T cells in experimental models and the anti-tumor activity of human γδ T cells. In this article, we first review the reciprocal interactions between neutrophils, tumor cells and T lymphocytes with a special focus on their interplay with γδ T cells, followed by the presentation of our own recent results. We have previously shown that zoledronic acid (ZOL)-activated neutrophils inhibit γδ T-cell proliferation due to the production of reactive oxygen species, arginase-1 and serine proteases. We now demonstrate that killing of ductal pancreatic adenocarcinoma (PDAC) cells by freshly isolated resting human γδ T cells was reduced in the presence of neutrophils and even more pronounced so after activation of neutrophils with ZOL. In contrast, direct T-cell receptor-dependent activation by γδ T cell-specific pyrophosphate antigens or by bispecific antibodies enhanced the cytotoxic activity and cytokine/granzyme B production of resting human γδ T cells, thereby overriding the suppression by ZOL-activated neutrophils. Additionally, the coculture of purified neutrophils with autologous short-term expanded γδ T cells enhanced rather than inhibited γδ T-cell cytotoxicity against PDAC cells. Purified neutrophils alone also exerted a small but reproducible lysis of PDAC cells which was further enhanced in the presence of γδ T cells. The latter set-up was associated with improved granzyme B and IFN-γ release which was further increased in the presence of ZOL. Our present results demonstrate that the presence of neutrophils can enhance the killing capacity of activated γδ T cells. We discuss these results in the broader context of regulatory interactions between neutrophils and T lymphocytes.

B lymphocytes with regulatory or effector functions synthesize granzyme B (GZMB). We investigated the frequency and phenotype of GZMB-producing B cells in breast tumor-draining lymph nodes (TDLNs). Mononuclear cells were isolated from 48 axillary lymph nodes and were stimulated with anti-BCR (B cell receptor), recombinant interleukin (IL)-21 and CD40 L alone or in combination. Flow cytometry was used to evaluate the expression of GZMB in B cells, and in 4 samples the phenotype of GZMB+ B cells was determined. B cells produced GZMB only when stimulated with a combination of IL-21 and anti-BCR for at least 16 h. Adding CD40 L to IL-21 and anti-BCR stimuli resulted in lower GZMB production in B cells. A small fraction of B cells was able to produce perforin in all stimulation conditions, and the majority of GZMB+ B cells were perforin-negative. Both naive (CD24lowCD27−) and active/memory (CD24hiCD27+) B cells expressed GZMB. In patients with invasive ductal carcinoma, the frequency of GZMB+ B cells was significantly lower in metastatic compared to non-metastatic lymph nodes. The frequency of GZMB+ B cells did not significantly correlate with prognostic factors such as stage, tumor size or Her2 expression. In summary, a subpopulation of both naive and memory B cells expressed GZMB in breast TDLNs. Our findings underscore the need to investigate the function of GZMB+ B cells in breast tumor immunity.

The E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but their regulation in this disease remains largely unknown; thus, we studied the function of CBL-B in atherogenesis.The expression of CBL-B in human atherosclerotic plaques was lower in advanced lesions compared with initial lesions and correlated inversely with necrotic core area. Twenty weeks old Cblb−/−Apoe−/− mice showed a significant increase in plaque area in the aortic arch, where initial plaques were present. In the aortic root, a site containing advanced plaques, lesion area rose by 40%, accompanied by a dramatic change in plaque phenotype. Plaques contained fewer macrophages due to increased apoptosis, larger necrotic cores, and more CD8+ T cells. Cblb−/−Apoe−/− macrophages exhibited enhanced migration and increased cytokine production and lipid uptake. Casitas B-cell lymphoma-B deficiency increased CD8+ T cell numbers, which were protected against apoptosis and regulatory T cell-mediated suppression. IFNγ and granzyme B production was enhanced in Cblb−/−Apoe−/− CD8+ T cells, which provoked macrophage killing. Depletion of CD8+ T cells in Cblb−/−Apoe−/− bone marrow chimeras rescued the phenotype, indicating that CBL-B controls atherosclerosis mainly through its function in CD8+ T cells. Casitas B-cell lymphoma-B expression in human plaques decreases during the progression of atherosclerosis. As an important regulator of immune responses in experimental atherosclerosis, CBL-B hampers macrophage recruitment and activation during initial atherosclerosis and limits CD8+ T cell activation and CD8+ T cell-mediated macrophage death in advanced atherosclerosis, thereby preventing the progression towards high-risk plaques.