Expression of the interleukin-7 receptor alpha chain (CD127) on virus-specific CD8+ T cells identifies functionally and phenotypically defined memory T cells during acute resolving hepatitis B virus infection

Gluten-Free Diet Induces Rapid Changes in Phenotype and Survival Properties of Gluten-Specific T Cells in Celiac Disease

BACKGROUND & AIMS

The treatment of celiac disease (CeD) with gluten-free diet (GFD) normalizes gut inflammation and disease-specific antibodies. CeD patients have HLA-restricted, gluten-specific T cells persisting in the blood and gut even after decades of GFD, which are reactivated and disease driving upon gluten exposure. Our aim was to examine the transition of activated gluten-specific T cells into a pool of persisting memory T cells concurrent with normalization of clinically relevant biomarkers during the first year of treatment.

METHODS

We followed 17 CeD patients during their initial GFD year, leading to disease remission. We assessed activation and frequency of gluten-specific CD4+ blood and gut T cells with HLA-DQ2.5:gluten tetramers and flow cytometry, disease-specific serology, histology, and symptom scores. We assessed gluten-specific blood T cells within the first 3 weeks of GFD in 6 patients and serology in an additional 9 patients.

RESULTS

Gluten-specific CD4+ T cells peaked in blood at day 14 while up-regulating Bcl-2 and down-regulating Ki-67 and then decreased in frequency within 10 weeks of GFD. CD38, ICOS, HLA-DR, and Ki-67 decreased in gluten-specific cells within 3 days. PD-1, CD39, and OX40 expression persisted even after 12 months. IgA-transglutaminase 2 decreased significantly within 4 weeks.

CONCLUSIONS

GFD induces rapid changes in the phenotype and number of gluten-specific CD4+ blood T cells, including a peak of nonproliferating, nonapoptotic cells at day 14. Subsequent alterations in T-cell phenotype associate with the quiescent but chronic nature of treated CeD. The rapid changes affecting gluten-specific T cells and disease-specific antibodies offer opportunities for clinical trials aiming at developing nondietary treatments for patients with newly diagnosed CeD.

Single-cell landscape of functionally cured chronic hepatitis B patients reveals activation of innate and altered CD4-CTL-driven adaptive immunity

BACKGROUND & AIMS

Hepatitis B surface antigen (HBsAg) loss or functional cure (FC) is considered the optimal therapeutic outcome for patients with chronic hepatitis B (CHB). However, the immune-pathological biomarkers and underlying mechanisms of FC remain unclear. In this study we comprehensively interrogate disease-associated cell states identified within intrahepatic tissue and matched PBMCs (peripheral blood mononuclear cells) from patients with CHB or after FC, at the resolution of single cells, to provide novel insights into putative mechanisms underlying FC.

METHODS

We combined single-cell transcriptomics (single-cell RNA sequencing) with multiparametric flow cytometry-based immune phenotyping, and multiplexed immunofluorescence to elucidate the immunopathological cell states associated with CHB vs. FC.

RESULTS

We found that the intrahepatic environment in CHB and FC displays specific cell identities and molecular signatures that are distinct from those found in matched PBMCs. FC is associated with the emergence of an altered adaptive immune response marked by CD4 cytotoxic T lymphocytes, and an activated innate response represented by liver-resident natural killer cells, specific Kupffer cell subtypes and marginated neutrophils. Surprisingly, we found MHC class II-expressing hepatocytes in patients achieving FC, as well as low but persistent levels of covalently closed circular DNA and pregenomic RNA, which may play an important role in FC.

CONCLUSIONS

Our study provides conceptually novel insights into the immuno-pathological control of HBV cure, and opens exciting new avenues for clinical management, biomarker discovery and therapeutic development. We believe that the discoveries from this study, as it relates to the activation of an innate and altered immune response that may facilitate sustained, low-grade inflammation, may have broader implications in the resolution of chronic viral hepatitis.

IMPACT AND IMPLICATIONS

This study dissects the immuno-pathological cell states associated with functionally cured chronic hepatitis B (defined by the loss of HBV surface antigen or HBsAg). We identified the sustained presence of very low viral load, accessory antigen-presenting hepatocytes, adaptive-memory-like natural killer cells, and the emergence of helper CD4 T cells with cytotoxic or effector-like signatures associated with functional cure, suggesting previously unsuspected alterations in the adaptive immune response, as well as a key role for the innate immune response in achieving or maintaining functional cure. Overall, the insights generated from this study may provide new avenues for the development of alternative therapies as well as patient surveillance for better clinical management of chronic hepatitis B.

Multifactoral immune modulation potentiates durable remission in multiple models of aggressive malignancy

Tumors typically lack canonical danger signals required to activate adaptive immunity and also frequently employ substantial immunomodulatory mechanisms that downregulate adaptive responses and contribute to escape from immune surveillance. Given the variety of mechanisms involved in shielding tumors from immune recognition, it is not surprising that single-agent immunomodulatory approaches have been largely unsuccessful in generating durable antitumor responses. Here we report a unique combination of immunomodulatory and cytostatic agents that recondition the tumor microenvironment and eliminate complex and/or poor-prognosis tumor types including the non-immunogenic 4T-1 model of TNBC, the aggressive MOC-2 model of HNSCC, and the high-risk MYCN-amplified model of neuroblastoma. A course of therapy optimized for TNBC cured a majority of tumors in both ectopic and orthotopic settings and eliminated metastatic spread in all animals tested at the highest doses. Immune responses were transferable between therapeutic donor and naïve recipient through adoptive transfer, and a sizeable abscopal effect on distant, untreated lesions could be demonstrated experimentally. Similar results were observed in HNSCC and neuroblastoma models, with characteristic remodeling of the tumor microenvironment documented in all model systems. scRNA-seq analysis implicated upregulation of innate immune responses and antigen presentation in tumor cells and the myeloid cell compartment as critical early events. This analysis also highlighted the potential importance of the autonomic nervous system in the governance of inflammatory processes. The data indicate that the targeting of multiple pathways and mechanisms of action can result in substantial synergistic antitumor effects and suggest follow-up in the neoadjuvant setting may be warranted.

IL-7 producing immunotherapy improves ex vivo T cell functions of immunosenescent patients, especially post hip fracture

Following acute stress such as trauma or sepsis, most of critically ill elderly patients become immunosuppressed and susceptible to secondary infections and enhanced mortality. We have developed a virus-based immunotherapy encoding human interleukin-7 (hIL-7) aiming at restoring both innate an adaptative immune homeostasis in these patients. We assessed the impact of this encoded hIL-7 on the ex vivo immune functions of T cells from PBMC of immunosenescent patients with or without hip fracture. T-cell ex vivo phenotyping was characterized in terms of senescence (CD57), IL-7 receptor (CD127) expression, and T cell differentiation profile. Then, post stimulation, activation status, and functionality (STAT5/STAT1 phosphorylation and T cell proliferation assays) were evaluated by flow cytometry. Our data show that T cells from both groups display immunosenescence features, express CD127 and are activated after stimulation by virotherapy-produced hIL-7-Fc. Interestingly, hip fracture patients exhibit a unique functional ability: An important T cell proliferation occurred compared to controls following stimulation with hIL-7-Fc. In addition, stimulation led to an increased naïve T cell as well as a decreased effector memory T cell proportions compared to controls. This preliminary study indicates that the produced hIL-7-Fc is well recognized by T cells and initiates IL-7 signaling through STAT5 and STAT1 phosphorylation. This signaling efficiently leads to T cell proliferation and activation and enables a T cell "rejuvenation." These results are in favor of the clinical development of the hIL-7-Fc expressing virotherapy to restore or induce immune T cell responses in immunosenescent hip fracture patients.

Upregulation of PD-1 Expression and High sPD-L1 Levels Associated with COVID-19 Severity

COVID-19 has several mechanisms that can lead to lymphocyte depletion/exhaustion. The checkpoint inhibitor molecule programmed death protein 1 (PD-1) and its programmed death-ligand 1 (PDL-1) play an important role in inhibiting cellular activity as well as the depletion of these cells. In this study, we evaluated PD-1 expression in TCD4+, TCD8+, and CD19+ lymphocytes from SARS-CoV-2-infected patients. A decreased frequency of total lymphocytes and an increased PD-1 expression in TCD4+ and CD19+ lymphocytes were verified in severe/critical COVID-19 patients. In addition, we found a decreased frequency of total monocytes with an increased PD-1 expression on CD14+ monocytes in severe/critical patients in association with the time of infection. Moreover, we observed an increase in sPD-L1 circulant levels associated with the severity of the disease. Overall, these data indicate an important role of the PD-1/PDL-1 axis in COVID-19 and may provide a severity-associated biomarker and therapeutic target during SARS-CoV-2 infection.

Lifelong cytomegalovirus and early-LIFE irradiation synergistically potentiate age-related defects in response to vaccination and infection

While whole-body irradiation (WBI) can induce some hallmarks of immune aging, (re)activation of persistent microbial infection also occurs following WBI and may contribute to immune effects of WBI over the lifespan. To test this hypothesis in a model relevant to human immune aging, we examined separate and joint effects of lifelong latent murine cytomegalovirus (MCMV) and of early-life WBI over the course of the lifespan. In late life, we then measured the response to a West Nile virus (WNV) live attenuated vaccine, and lethal WNV challenge subsequent to vaccination. We recently published that a single dose of non-lethal WBI in youth, on its own, was not sufficient to accelerate aging of the murine immune system, despite widespread DNA damage and repopulation stress in hematopoietic cells. However, 4Gy sub-lethal WBI caused manifest reactivation of MCMV. Following vaccination and challenge with WNV in the old age, MCMV-infected animals experiencing 4Gy, but not lower, dose of sub-lethal WBI in youth had reduced survival. By contrast, old irradiated mice lacking MCMV and MCMV-infected, but not irradiated, mice were both protected to the same high level as the old non-irradiated, uninfected controls. Analysis of the quality and quantity of anti-WNV immunity showed that higher mortality in MCMV-positive WBI mice correlated with increased levels of MCMV-specific immune activation during WNV challenge. Moreover, we demonstrate that infection, including that by WNV, led to MCMV reactivation. Our data suggest that MCMV reactivation may be an important determinant of increased late-life mortality following early-life irradiation and late-life acute infection.

Induction of memory-like CD8+ T cells and CD4+ T cells from human naive T cells in culture

Memory T cells are crucial players in vertebrate adaptive immunity but their development is incompletely understood. Here, we describe a method to produce human memory-like T cells from naive human T cells in culture. Using commercially available human T-cell differentiation kits, both purified naive CD8⁺ T cells and purified naive CD4⁺ T cells were activated via T-cell receptor signaling and appropriate cytokines for several days in culture. All the T-cell activators were then removed from the medium and the cultures were continued in hypoxic condition (1% O₂ atmosphere) for several more days; during this period, most of the cells died, but some survived in a quiescent state for a month. The survivors had small round cell bodies, expressed differentiation markers characteristic of memory T cells and restarted proliferation when the T-cell activators were added back. We could also induce memory-like T cells from naive human T cells without hypoxia, if we froze the activated T cells or prepared the naive T cells from chilled filter buffy coats.

Selective dependence on IL-7 for antigen-specific CD8 T cell responses during airway influenza infection

Interleukin-7 (IL-7) is a cytokine known for its importance in T cell development and survival. How IL-7 shapes CD8 T cell responses during an acute viral infection is less understood. We had previously shown that IL-7 signaling deficient mice have reduced accumulation of influenza-specific CD8 T cells following influenza infection. We sought to determine whether IL-7 affects early CD8 T cell expansion in the mediastinal lymph node and effector function in the lungs. Using IL-7Rα signaling deficient mice, we show that IL-7 is required for a normal sized mediastinal lymph node and the early clonal expansion of influenza-specific CD8 T cells therein. We show that IL-7 plays a cell-intrinsic role in the accumulation of NP366-374 and PA224-233-specific CD8 T cells in the lymph node. We also found that IL-7 shapes terminal differentiation, degranulation and cytokine production to a greater extent in PA224-233-specific than NP366-374-specific CD8 T cells. We further demonstrate that IL-7 is induced in the lung tissue by viral infection and we characterize multiple cellular sources that contribute to IL-7 production. Our findings on IL-7 and its effects on lower respiratory diseases will be important for expanding the utility of therapeutics that are currently available.

Pre-existing immunity and vaccine history determine hemagglutinin-specific CD4 T cell and IgG response following seasonal influenza vaccination

Effectiveness of seasonal influenza vaccination varies between individuals and might be affected by vaccination history among other factors. Here we show, by monitoring frequencies of CD4 T cells specific to the conserved hemagglutinin epitope HA118-132 and titres of IgG against the corresponding recombinant hemagglutinin protein, that antigen-specific CD4 T cell and antibody responses are closely linked to pre-existing immunity and vaccine history. Upon immunization, a strong early reaction is observed in all vaccine naïve participants and also in vaccine experienced individuals who have not received the respective seasonal vaccine in the previous year. This response is characterized by HA118-132 specific CD4 T cells with a follicular helper T cell phenotype and by ascending titers of hemagglutinin-specific antibodies from baseline to day 28 following vaccination. This trend was observed in only a proportion of those participants who received the seasonal vaccine the year preceding the study. Regardless of history, levels of pre-existing antibodies and CD127 expression on CD4 T cells at baseline were the strongest predictors of robust early response. Thus, both pre-existing immunity and vaccine history contribute to the response to seasonal influenza vaccines.

Yin and yang of immunological memory in controlling infections: Overriding self defence mechanisms

Immunological memory is critical for host immunity and decisive for individual to respond exponentially to previously encountered infection. Both T and B cell memory are known to orchestrate immunological memory with their central and effector memory arms contributing in prolonged immunity/defence mechanisms of host. While central memory helps in maintaining prolonged immunity for a particular infection, effector memory helps in keeping local/seasonal infection in control. In addition to this, generation of long-lived plasma cells is pivotal for generating neutralizing antibodies which can enhance recall and B cell memory to control re-infection. In view of this, scaling up memory response is one of the major objectives for the expected outcome of vaccination. In this line, this review deals with the significance of memory cells, molecular pathways of their development, maintenance, epigenetic regulation and negative regulation in various infections. We have also highlighted the significance of both T and B cell memory responses in the vaccination approaches against range of infections which is not fully explored so far.[Box: see text].

Lymphocyte Landscape after Chronic Hepatitis C Virus (HCV) Cure: The New Normal

Chronic HCV (CHC) infection is the only chronic viral infection for which curative treatments have been discovered. These direct acting antiviral (DAA) agents target specific steps in the viral replication cycle with remarkable efficacy and result in sustained virologic response (SVR) or cure in high (>95%) proportions of patients. These treatments became available 6–7 years ago and it is estimated that their real impact on HCV related morbidity, including outcomes such as cirrhosis and hepatocellular carcinoma (HCC), will not be known for the next decade or so. The immune system of a chronically infected patient is severely dysregulated and questions remain regarding the immune system’s capacity in limiting liver pathology in a cured individual. Another important consequence of impaired immunity in patients cleared of HCV with DAA will be the inability to generate protective immunity against possible re-infection, necessitating retreatments or developing a prophylactic vaccine. Thus, the impact of viral clearance on restoring immune homeostasis is being investigated by many groups. Among the important questions that need to be answered are how much the immune system normalizes with cure, how long after viral clearance this recalibration occurs, what are the consequences of persisting immune defects for protection from re-infection in vulnerable populations, and does viral clearance reduce liver pathology and the risk of developing hepatocellular carcinoma in individuals cured with these agents. Here, we review the recent literature that describes the defects present in various lymphocyte populations in a CHC patient and their status after viral clearance using DAA treatments.

Role of Immunomodulators in Functional Cure Strategies for HBV

Purpose of Review

Chronic Hepatitis B Virus (HBV) Infection is a major global health burden. Currently, a curative therapy does not exist; thus, there is an urgent need for new therapeutical options. Viral elimination in the natural course of infection results from a robust and multispecific T and B cell response that, however, is dysfunctional in chronically infected patients. Therefore, immunomodulatory therapies that strengthen the immune responses are an obvious approach trying to control HBV infection. In this review, we summarize the rationale and current options of immunological cure of chronic HBV infection.

Recent Findings

Recently, among others, drugs that stimulate the innate immune system or overcome CD8+ T cell exhaustion by checkpoint blockade, and transfer of HBV-specific engineered CD8+ T cells emerged as promising approaches.

Summary

HBV-specific immunity is responsible for viral control, but also for immunopathogenesis. Thus, the development of immunomodulatory therapies is a difficult process on a thin line between viral control and excessive immunopathology. Some promising agents are under investigation. Nevertheless, further research is indispensable in order to optimally orchestrate immunostimulation.

Immunometabolism and HIV-1 pathogenesis: food for thought

Antiretroviral therapies efficiently block HIV-1 replication but need to be maintained for life. Moreover, chronic inflammation is a hallmark of HIV-1 infection that persists despite treatment. There is, therefore, an urgent need to better understand the mechanisms driving HIV-1 pathogenesis and to identify new targets for therapeutic intervention. In the past few years, the decisive role of cellular metabolism in the fate and activity of immune cells has been uncovered, as well as its impact on the outcome of infectious diseases. Emerging evidence suggests that immunometabolism has a key role in HIV-1 pathogenesis. The metabolic pathways of CD4⁺ T cells and macrophages determine their susceptibility to infection, the persistence of infected cells and the establishment of latency. Immunometabolism also shapes immune responses against HIV-1, and cell metabolic products are key drivers of inflammation during infection. In this Review, we summarize current knowledge of the links between HIV-1 infection and immunometabolism, and we discuss the potential opportunities and challenges for therapeutic interventions.

The Construction and Immunoadjuvant Activities of the Oral Interleukin-17B Expressed by Lactobacillus plantarum NC8 Strain in the Infectious Bronchitis Virus Vaccination of Chickens

Interleukin-17B (IL-17B) is a protective cytokine of the IL-17 family and plays an essential role in the regulation of mucosal inflammation. However, little is known about the role of IL-17B in the control of viral infections. In this study, a recombinant Lactobacillus plantarum, designated as NC8-ChIL17B, was constructed to express the chicken IL-17B (ChIL-17B) gene. The recombinant ChIL17B (rChIL17B) protein was about 14 kDa and was anchored to the surface of NC8 cells. In vitro, it was found that the rChIL17B protein inhibited the proliferation of the infectious bronchitis virus (IBV) through activation of nuclear factor kappa B (NF-κB) and the JAK (Janus kinase)-STAT (signal transducers and activators of transcription) signaling. Moreover, to evaluate the immunoadjuvant activities of NC8-ChIL17B, 40 three-day-old specific pathogen-free (SPF) chickens were divided into four groups. Three groups were orally vaccinated with fresh NC8, NC8-ChIL17B, and phosphate buffered saline (PBS), along with the infectious bronchitis virus vaccine, and the other group was the PBS-negative control. The results of the IBV-specific antibody titer and the concentration of the cytokines IL-2, IL-4, IL-6, and interferon gamma (IFN-γ) in sera, as well as the concentration of secretory immunoglobulin A (sIgA) in the tracheal and small intestinal mucosa, the number of cluster of differentiation 4 positive (CD4⁺) and cluster of differentiation 8 positive (CD8⁺) T cells in the blood, and the expression of immune-related genes all indicated that NC8-ChIL17B efficiently enhanced the humoral and cellular immune responses to IBV vaccine. Moreover, the viral loads in the NC8-ChIL17B- and IBV-vaccinated group were significantly lower than in the control groups, suggesting a significant promotion of the immunoprotection of IBV vaccination against the virulent IBV strain. Therefore, ChIL-17B is a promising, effective adjuvant candidate for chicken virus vaccines.

Pathogenetic Mechanisms of T Cell Dysfunction in Chronic HBV Infection and Related Therapeutic Approaches

A great effort of research has been devoted in the last few years to developing new anti-HBV therapies of finite duration that also provide effective sustained control of virus replication and antigen production. Among the potential therapeutic strategies, immune-modulation represents a promising option to cure HBV infection and the adaptive immune response is a rational target for novel therapeutic interventions, in consideration of the key role played by T cells in the control of virus infections. HBV-specific T cells are severely dysfunctional in chronic HBV infection as a result of several inhibitory mechanisms which are simultaneously active within the chronically inflamed liver. Indeed, the liver is a tolerogenic organ harboring different non-parenchymal cell populations which can serve as antigen presenting cells (APC) but are poorly efficient in effector T cell priming, with propensity to induce T cell tolerance rather than T cell activation, because of a poor expression of co-stimulatory molecules, up-regulation of the co-inhibitory ligands PD-L1 and PD-L2 upon IFN stimulation, and production of immune regulatory cytokines, such as IL10 and TGF-β. They include resident dendritic cells (DCs), comprising myeloid and plasmacytoid DCs, liver sinusoidal endothelial cells (LSECs), Kupffer cells (KCs), hepatic stellate cells (HSCs) as well as the hepatocytes themselves. Additional regulatory mechanisms which contribute to T cell attrition in the chronically infected liver are the high levels of soluble mediators, such as arginase, indoleamine 2,3-dioxygenase (IDO) and suppressive cytokines, the up-regulation of inhibitory checkpoint receptor/ligand pairs, the expansion of regulatory cells, such as CD4+FOXp3+ Treg cells, myeloid-derived suppressor cells and NK cells. This review will deal with the interactions between immune cells and liver environment discussing the different mechanisms which contribute to T cell dysfunction in chronic hepatitis B, some of which are specifically activated in HBV infection and others which are instead common to chronic inflammatory liver diseases in general. Therapeutic interventions targeting dysregulated pathways and cellular functions will be also delineated.

Programmed cell death protein 1 (PD-1) in infection

Exhausted and dysfunctional T cells triggered by infection and cancer render the immune system unable to eliminate these pathogens. Pharmacologic blockade of the surface receptors that inhibit T-cell function has shown remarkable success in patients with various malignancies. In this Review, we discuss the emerging evidence of inhibiting checkpoint pathways as a potential role in controlling or clearing infectious diseases. Though interesting tendencies, much work is still needed in order to develop safe strategies that can be translated into clinically relevant outcomes in patients with infections.

Checkpoint Inhibitors and Therapeutic Vaccines for the Treatment of Chronic HBV Infection

Treatment of chronic hepatitis B virus (HBV) infection is highly effective in suppressing viral replication, but complete cure is rarely achieved. In recent years, substantial progress has been made in the development of immunotherapy to treat cancer. Applying these therapies to improve the management of chronic HBV infection is now being attempted, and has become an area of active research. Immunotherapy with vaccines and checkpoint inhibitors can boost T cell functions in vitro, and therefore may be used to reinvigorate the impaired HBV-specific T cell response. However, whether these approaches will suffice and restore antiviral T cell immunity to induce long-term HBV control remains an open question. Recent efforts have begun to describe the phenotype and function of HBV-specific T cells on the single epitope level. An improved understanding of differing T cell specificities and their contribution to HBV control will be instrumental for advancement of the field. In this review, we outline correlates of successful versus inadequate T cell responses to HBV, and discuss the rationale behind therapeutic vaccines and checkpoint inhibitors for the treatment of chronic HBV infection.

Hepatitis B virus-triggered PTEN/β-catenin/c-Myc signaling enhances PD-L1 expression to promote immune evasion

Hepatitis B virus (HBV) exploits multiple strategies to evade host immune surveillance. Programmed cell death 1 (PD-1)/programmed death ligand 1 (PD-L1) signaling plays a critical role in regulating T cell homeostasis. However, it remains largely unknown as to how HBV infection elevates PD-L1 expression in hepatocytes. A mouse model of HBV infection was established by hydrodynamic injection with a vector containing 1.3-fold overlength HBV genome (pHBV1.3) via the tail vein. Coculture experiments with HBV-expressing hepatoma cells and Jurkat T cells were established in vitro. We observed significant decrease in the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and increase in β-catenin/PD-L1 expression in liver tissues from patients with chronic hepatitis B and mice subjected to pHBV1.3 hydrodynamic injection. Mechanistically, decrease in PTEN enhanced β-catenin/c-Myc signaling and PD-L1 expression in HBV-expressing hepatoma cells, which in turn augmented PD-1 expression, lowered IL-2 secretion, and induced T cell apoptosis. However, β-catenin disruption inhibited PTEN-mediated PD-L1 expression, which was accompanied by decreased PD-1 expression, and increased IL-2 production in T cells. Luciferase reporter assays revealed that c-Myc stimulated transcriptional activity of PD-L1. In addition, HBV X protein (HBx) and HBV polymerase (HBp) contributed to PTEN downregulation and β-catenin/PD-L1 upregulation. Strikingly, PTEN overexpression in hepatocytes inhibited β-catenin/PD-L1 signaling and promoted HBV clearance in vivo. Our findings suggest that HBV-triggered PTEN/β-catenin/c-Myc signaling via HBx and HBp enhances PD-L1 expression, leading to inhibition of T cell response, and promotes HBV immune evasion.NEW & NOTEWORTHY This study demonstrates that during HBV infection, HBV can increase PD-L1 expression via PTEN/β-catenin/c-Myc signaling pathway, which in turn inhibits T cell response and ultimately promotes HBV immune evasion. Targeting this signaling pathway is a potential strategy for immunotherapy of chronic hepatitis B.

Programmed cell death protein 1 promotes hepatitis B virus transmission through the regulation of ERK1/2-mediated trophoblasts differentiation

PURPOSE

The purpose of our research is to evaluate the mechanism of PD-1 in the promotion of HBV transmission.

METHODS

HBV was used to infect two human choriocarcinoma cell line, including JEG-3, as well as BeWo. We used PCR and western blotting to detect PD-1 gene and protein expression levels in cells. Stable knockdown of the PD-1 gene in JEG-3 cells was obtained by lentiviral transfection. Trophoblast cell proliferation was evaluated using CCK8 and flow cytometry. The concentration of HBV antibody in the cell supernatant was measured by ELISA. DNA was then extracted from the cells and the copy number of the HBV virus was detected by PCR. Finally, ERK1/2 expression was detected by western blot.

RESULTS

High PD-1 gene expression in HBV-infected trophoblasts and the knockdown of PD-1 gene can, respectively, improve the proliferation of HBV-infected trophoblasts and reduce viral replication in trophoblasts. In addition, PD-1 and ERK1/2 proteins were co-expressed in HBV-infected trophoblasts and inhibited the activation of ERK1/2 pathway in HBV-infected trophoblasts. ERK1/2 expression significantly increased after PD-1 knockdown. Therefore, PD-1 might be an important protein in trophoblast cells infected with HBV.

CONCLUSIONS

PD-1 promoted HBV transmission through regulating ERK1/2-mediated trophoblasts differentiation. Therefore, our research may provide new ideas and methods for preventing mother-to-child transmission of HBV infection during pregnancy.

CCL19 and CCR7 Expression, Signaling Pathways, and Adjuvant Functions in Viral Infection and Prevention

Chemokine (C–C motif) ligand 19 (CCL19) is a critical regulator of the induction of T cell activation, immune tolerance, and inflammatory responses during continuous immune surveillance, homeostasis, and development. Migration of CC-chemokine receptor 7 (CCR7)-expressing cells to secondary lymphoid organs is a crucial step in the onset of adaptive immunity, which is initiated by a complex interaction between CCR7 and its cognate ligands. Recent advances in knowledge regarding the response of the CCL19-CCR7 axis to viral infections have elucidated the complex network of interplay among the invading virus, target cells and host immune responses. Viruses use various strategies to evade or delay the cytokine response, gaining additional time to replicate in the host. In this review, we summarize the impacts of CCL19 and CCR7 expression on the regulation of viral pathogenesis with an emphasis on the corresponding signaling pathways and adjuvant mechanisms. We present and discuss the expression, signaling adaptor proteins and effects of CCL19 and CCR7 as these molecules differentially impact different viral infections and viral life cycles in host homeostatic strategies. The underlying mechanisms discussed in this review may assist in the design of novel agents to modulate chemokine activity for viral prevention.

Ex vivo Detection and Characterization of Hepatitis B Virus-Specific CD8+ T Cells in Patients Considered Immune Tolerant

In this study, we aimed to detect and characterize ex vivo virus-specific CD8⁺ T cells in patients with immune-tolerant hepatitis B virus (HBV) infection. We investigated a Korean chronic hepatitis B cohort composed of 15 patients in the immune-tolerant phase, 17 in the immune-active phase, and 13 under antiviral treatment. We performed enzyme-linked immunospot (ELISpot) assays ex vivo and intracellular cytokine staining after in vitro culture. We also performed ex vivo multimer staining assays and examined the expression of programmed death-1 (PD-1) and CD127 in pentamer-positive cells. Ex vivo ELISpot revealed that HBV-specific T cell function was weaker in immune-tolerant patients than in those under antiviral treatment. In vitro culture of peripheral blood mononuclear cells for 10 days revealed that HBV-specific CD8⁺ T cells produced interferon-γ in some immune-tolerant patients. We detected HBV-specific CD8⁺ T cells ex vivo (using the HBV core_18-27 pentamer) in patients from all three groups. The PD-1⁺ subset of pentamer⁺ CD8⁺ T cells was smaller ex vivo in the immune-tolerant phase than in the immune-active phase or under antiviral treatment. Interestingly, the proportion of PD-1⁺ CD8⁺ T cells in HBV-specific CD8⁺ T cells correlated with patient age when all enrolled patients were analyzed. Overall, HBV-specific CD8⁺ T cells are present in patients considered as immune-tolerant, although their ex vivo functionality is significantly weaker than that in patients under antiviral treatment (P < 0.05). Despite the high viral load, the proportion of PD-1 expression in HBV-specific CD8⁺ T cells is lower in the immune-tolerant phase than in other phases. Our results indicate appropriate stimulation may enhance the effector function of HBV-specific CD8⁺ T cells in patients considered as being in the immune-tolerant phase.

Phenotype and function of HBV-specific T cells is determined by the targeted epitope in addition to the stage of infection

OBJECTIVE

Chronic HBV infection affects more than 250 million people worldwide and remains a global healthcare problem in part because we lack curative treatment. Sustained viral control requires HBV-specific T cells, but these become functionally impaired in chronic infection. Clinical evidence indicates that functional cure of HBV infection by the host immune response is feasible. Developing T cell-based therapies able to achieve functional cure will require identification of the requirements for a successful T cell response against HBV and the relative contribution of individual T cell specificities to HBV control.

DESIGN

The phenotype and function of HBV-specific T cells were studied directly ex vivo using fluorochrome-labelled multimers. We studied multiple HBV-specific T cell specificities targeting different HBV proteins in individuals with either an acute self-limiting or chronic HBV infection.

RESULTS

We detected strong T cell responses targeting multiple HBV viral proteins in acute self-limiting and low-frequency core and polymerase-specific T cells in chronic infection. Expression of the T cell inhibitory receptor PD-1, as well as T cell differentiation, T cell function and T cell regulation differed by stages and outcomes of infection. In addition, these features differed significantly between T cells targeting different HBV specificities.

CONCLUSION

HBV-specific T cells with different target specificities are characterised by distinct phenotypical and functional profiles. These results have direct implications for the design of immunological studies in HBV infection, and are potentially relevant for informing immunotherapeutic approaches to induce functional cure.

Human breast tumor-infiltrating CD8+ T cells retain polyfunctionality despite PD-1 expression

Functional CD8⁺ T cells in human tumors play a clear role in clinical prognosis and response to immunotherapeutic interventions. PD-1 expression in T cells involved in chronic infections and tumors such as melanoma often correlates with a state of T-cell exhaustion. Here we interrogate CD8⁺ tumor-infiltrating lymphocytes (TILs) from human breast and melanoma tumors to explore their functional state. Despite expression of exhaustion hallmarks, such as PD-1 expression, human breast tumor CD8⁺ TILs retain robust capacity for production of effector cytokines and degranulation capacity. In contrast, melanoma CD8⁺ TILs display dramatic reduction of cytokine production and degranulation capacity. We show that CD8⁺ TILs from human breast tumors can potently kill cancer cells via bi-specific antibodies. Our data demonstrate that CD8⁺ TILs in human breast tumors retain polyfunctionality, despite PD-1 expression, and suggest that they may be harnessed for effective immunotherapies.

Expression of the checkpoint molecule programmed cell death protein 1 (PD-1) is considered a marker of T cells exhaustion. Here the authors show that CD8T cells isolated from breast cancer patients are perfectly functional despite PD-1 expression while those isolated from melanoma patients are not.

Description of CD8+ Regulatory T Lymphocytes and Their Specific Intervention in Graft-versus-Host and Infectious Diseases, Autoimmunity, and Cancer

Gershon and Kondo described CD8⁺ Treg lymphocytes as the first ones with regulating activity due to their tolerance ability to foreign antigens and their capacity to inhibit the proliferation of other lymphocytes. Regardless, CD8⁺ Treg lymphocytes have not been fully described-unlike CD4⁺ Treg lymphocytes-because of their low numbers in blood and the lack of specific and accurate population markers. Still, these lymphocytes have been studied for the past 30 years, even after finding difficulties during investigations. As a result, studies have identified markers that define their subpopulations. This review is focused on the expression of cell membrane markers as CD25, CD122, CD103, CTLA-4, CD39, CD73, LAG-3, and FasL as well as soluble molecules such as FoxP3, IFN-γ, IL-10, TGF-β, IL-34, and IL-35, in addition to the lack of expression of cell activation markers such as CD28, CD127 CD45RC, and CD49d. This work also underlines the importance of identifying some of these markers in infections with several pathogens, autoimmunity, cancer, and graft-versus-host disease as a strategy in their prevention, monitoring, and cure.

Drugs in Development for Hepatitis B

With high morbidity and mortality worldwide, there is great interest in effective therapies for chronic hepatitis B (CHB) virus. There are currently several dozen investigational agents being developed for treatment of CHB. They can be broadly divided into two categories: (1) direct-acting antivirals (DAAs) that interfere with a specific step in viral replication; and (2) host-targeting agents that inhibit viral replication by modifying host cell function, with the latter group further divided into the subcategories of immune modulators and agents that target other host functions. Included among the DAAs being developed are RNA interference therapies, covalently closed circular DNA (cccDNA) formation and transcription inhibitors, core/capsid inhibitors, reverse transcriptase inhibitors, hepatitis B surface antigen (HBsAg) release inhibitors, antisense oligonucleotides, and helioxanthin analogues. Included among the host-targeting agents are entry inhibitors, cyclophilin inhibitors, and multiple immunomodulatory agents, including Toll-like receptor agonists, immune checkpoint inhibitors, therapeutic vaccines, engineered T cells, and several cytokine agents, including recombinant human interleukin-7 (CYT107) and SB 9200, a novel therapy that is believed to both have direct antiviral properties and to induce endogenous interferon. In this review we discuss agents that are currently in the clinical stage of development for CHB treatment as well as strategies and agents currently at the evaluation and discovery phase and potential future targets. Effective approaches to CHB may require suppression of viral replication combined with one or more host-targeting agents. Some of the recent research advances have led to the hope that with such a combined approach we may have a functional cure for CHB in the not distant future.

Overcoming immune tolerance in chronic hepatitis B by therapeutic vaccination

The currently used nucleoside analogs (i.e. entecavir and tenofovir) with high barrier-to-resistance efficiently suppress viral replication, limit inflammation and reduce the sequelae of chronic hepatitis B, but cannot cure the disease and thus have to be applied long-term. Therapeutic vaccination as an approach to cure chronic hepatitis B has shown promising pre-clinical results, nevertheless the proof of its efficacy in clinical trials is still missing. This may be partially due to suboptimal vaccine design. A main obstacle in chronic hepatitis B, however, is the high load of viral antigens expressed and secreted, which has been proposed to cause antigen-specific immune tolerance. Reduction of the viral antigen load is therefore considered a key factor for success of immune-based therapies. Although nucleoside analogs do not reduce viral antigen expression, new antiviral strategies are becoming available. Targeting viral translation by siRNA or targeting release of HBsAg from infected hepatocytes by nucleic acid polymers both reduce the antigen load. They may be considered as pre-treatment for therapeutic vaccination to increase the potential to elicit an HBV-specific immune response able to control and cure chronic HBV infection.

Immune checkpoint receptors: homeostatic regulators of immunity

Alcoholic liver disease (ALD) is an escalating global problem accounting for more than 3 million deaths annually. Bacterial infections are diagnosed in 25-47% of hospitalized patients with cirrhosis and represent the most important trigger for acute decompensation, multi-organ failure, septic shock and death. Current guidelines recommend intensive antibiotic therapy, but this has led to the emergence of multi-drug resistant bacteria, which are associated with increased morbidity and mortality rates. As such, there is a pressing need to explore new paradigms for anti-infective therapy and host-directed immunomodulatory therapies are a promising approach. Paradoxically, cirrhotic patients are characterised by heightened immune activity and exacerbated inflammatory processes but are unable to contend with bacterial infection, demonstrating that whilst immune effector cells are primed, their antibacterial effector functions are switched-off, reflecting a skewed homeostatic balance between anti-pathogen immunity and host-induced immunopathology. Preservation of this equilibrium physiologically is maintained by multiple immune-regulatory checkpoints and these feedback receptors serve as pivotal regulators of the host immunity. Checkpoint receptor blockade is proving to be effective at rescuing deranged/exhausted immunity in pre-clinical studies for chronic viral infection and sepsis. This approach has also obtained FDA approval for restoring anti-tumor immunity, with improved response rates and good safety profiles. To date, no clinical studies have investigated checkpoint blockade in ALD, highlighting an area for development of host-targeted immunotherapeutic strategies in ALD, for which there are no current specific treatment options. This review aims at framing current knowledge on immune checkpoints and the possibility of their therapeutic utility in ALD-associated immune dysfunctions.

Precursors of human CD4+ cytotoxic T lymphocytes identified by single-cell transcriptome analysis

CD4+ cytotoxic T lymphocytes (CD4-CTLs) have been reported to play a protective role in several viral infections. However, little is known in humans about the biology of CD4-CTL generation, their functional properties, and heterogeneity, especially in relation to other well-described CD4+ memory T cell subsets. We performed single-cell RNA sequencing in more than 9000 cells to unravel CD4-CTL heterogeneity, transcriptional profile, and clonality in humans. Single-cell differential gene expression analysis revealed a spectrum of known transcripts, including several linked to cytotoxic and costimulatory function that are expressed at higher levels in the TEMRA (effector memory T cells expressing CD45RA) subset, which is highly enriched for CD4-CTLs, compared with CD4+ T cells in the central memory (TCM) and effector memory (TEM) subsets. Simultaneous T cell antigen receptor (TCR) analysis in single cells and bulk subsets revealed that CD4-TEMRA cells show marked clonal expansion compared with TCM and TEM cells and that most of CD4-TEMRA were dengue virus (DENV)-specific in donors with previous DENV infection. The profile of CD4-TEMRA was highly heterogeneous across donors, with four distinct clusters identified by the single-cell analysis. We identified distinct clusters of CD4-CTL effector and precursor cells in the TEMRA subset; the precursor cells shared TCR clonotypes with CD4-CTL effectors and were distinguished by high expression of the interleukin-7 receptor. Our identification of a CD4-CTL precursor population may allow further investigation of how CD4-CTLs arise in humans and, thus, could provide insights into the mechanisms that may be used to generate durable and effective CD4-CTL immunity.

Use of Current and New Endpoints in the Evaluation of Experimental Hepatitis B Therapeutics

New hepatitis B virus (HBV) therapies are expected to have breakthrough benefit for patients. HBV functional cure is sustained hepatitis B surface antigen loss and anti-HBs gain, with normalization of serum aminotransferases off therapy. Virologic or complete cure additionally includes loss of HBV covalently closed circular DNA. Currently available endpoints of therapy are inadequate to evaluate the efficacy of many of the new therapeutics. Therefore, either new ways of using the existing virologic endpoints and laboratory values or entirely new biomarkers are needed. In this review, we discuss the currently used endpoints, potential new endpoints, as well as what new markers are needed to assess the ability of HBV therapeutics to achieve functional and virologic cure in various phases of HBV infection. In addition, we discuss how patient selection from differing phases of HBV impacts the choice of HBV drug(s) needed to achieve cure.

Dynamics of the Immune Response in Acute Hepatitis B Infection

Background

Acute hepatitis B virus infection in adults is generally self-limiting but may lead to chronicity in a minority of patients.

Methods

We included 9 patients with acute hepatitis B virus (HBV) infection and collected longitudinal follow-up samples. Natural killer (NK) cell characteristics were analyzed by flowcytometry. HBV-specific T-cell function was analyzed by in vitro stimulation with HBV peptide pools and intracellular cytokine staining.

Results

Median baseline HBV DNA load was 5.12 log IU/mL, and median ALT was 2652 U/mL. Of 9 patients, 8 cleared HBsAg within 6 months whereas 1 patient became chronically infected. Early time points after infection showed increased CD56^bright NK cells and an increased proportion of cells expressing activation markers. Most of these had normalized at week 24, while the proportion of TRAIL-positive CD56^bright NK cells remained high in the chronically infected patient. In patients who cleared HBV, functional HBV-specific CD8+ and CD4+ responses could be observed, whereas in the patient who developed chronic infection, only low HBV-specific T-cell responses were observed.

Conclusions

NK cells are activated early in the course of acute HBV infection. Broad and multispecific T-cell responses are observed in patients who clear acute HBV infection, but not in a patient who became chronically infected.

Conventional CD4+ T cells present bacterial antigens to induce cytotoxic and memory CD8+ T cell responses

Bacterial phagocytosis and antigen cross-presentation to activate CD8⁺ T cells are principal functions of professional antigen presenting cells. However, conventional CD4⁺ T cells also capture and kill bacteria from infected dendritic cells in a process termed transphagocytosis (also known as transinfection). Here, we show that transphagocytic T cells present bacterial antigens to naive CD8⁺ T cells, which proliferate and become cytotoxic in response. CD4⁺ T-cell-mediated antigen presentation also occurs in vivo in the course of infection, and induces the generation of central memory CD8⁺ T cells with low PD-1 expression. Moreover, transphagocytic CD4⁺ T cells induce protective anti-tumour immune responses by priming CD8⁺ T cells, highlighting the potential of CD4⁺ T cells as a tool for cancer immunotherapy.

Antigen presentation is generally considered the domain of innate immune cells, but CD4⁺ T cells can transphagocytose bacteria from infected dendritic cells. Here the authors show CD4⁺ T cells can transphagocytose bacterial and tumour antigens and present them to CD8⁺ T cells to activate memory and cytotoxic functions.

Telomere Dynamics in Immune Senescence and Exhaustion Triggered by Chronic Viral Infection

The progressive loss of immunological memory during aging correlates with a reduced proliferative capacity and shortened telomeres of T cells. Growing evidence suggests that this phenotype is recapitulated during chronic viral infection. The antigenic volume imposed by persistent and latent viruses exposes the immune system to unique challenges that lead to host T-cell exhaustion, characterized by impaired T-cell functions. These dysfunctional memory T cells lack telomerase, the protein capable of extending and stabilizing chromosome ends, imposing constraints on telomere dynamics. A deleterious consequence of this excessive telomere shortening is the premature induction of replicative senescence of viral-specific CD8+ memory T cells. While senescent cells are unable to expand, they can survive for extended periods of time and are more resistant to apoptotic signals. This review takes a closer look at T-cell exhaustion in chronic viruses known to cause human disease: Epstein–Barr virus (EBV), Hepatitis B/C/D virus (HBV/HCV/HDV), human herpesvirus 8 (HHV-8), human immunodeficiency virus (HIV), human T-cell leukemia virus type I (HTLV-I), human papillomavirus (HPV), herpes simplex virus-1/2 (HSV-1/2), and Varicella–Zoster virus (VZV). Current literature linking T-cell exhaustion with critical telomere lengths and immune senescence are discussed. The concept that enduring antigen stimulation leads to T-cell exhaustion that favors telomere attrition and a cell fate marked by enhanced T-cell senescence appears to be a common endpoint to chronic viral infections.

Coinhibitory Receptor Expression and Immune Checkpoint Blockade: Maintaining a Balance in CD8+ T Cell Responses to Chronic Viral Infections and Cancer

In cancer and chronic viral infections, T cells are exposed to persistent antigen stimulation. This results in expression of multiple inhibitory receptors also called “immune checkpoints” by T cells. Although these inhibitory receptors under normal conditions maintain self-tolerance and prevent immunopathology, their sustained expression deteriorates T cell function: a phenomenon called exhaustion. Recent advances in cancer immunotherapy involve blockade of cytotoxic T lymphocyte antigen-4 and programmed cell death 1 in order to reverse T cell exhaustion and reinvigorate immunity, which has translated to dramatic clinical remission in many cases of metastatic melanoma and lung cancer. With the paucity of therapeutic vaccines against chronic infections such as HIV, HPV, hepatitis B, and hepatitis C, such adjunct checkpoint blockade strategies are required including the blockade of other inhibitory receptors such as T cell immunoreceptor with immunoglobulin (Ig) and immunoreceptor tyrosine-based inhibitory motif domains, T cell Ig and mucin-domain containing-3, lymphocyte activation gene 3, and V-domain Ig-containing suppressor of T cell activation. The nature of different chronic viral infections and cancers is likely to influence the level, composition, and pattern of inhibitory receptors expressed by responding T cells. This will have implications for checkpoint antibody blockade strategies employed for treating tumors and chronic viral infections. Here, we review recent advances that provide a clearer insight into the role of coinhibitory receptor expression in T cell exhaustion and reveal novel antibody-blockade therapeutic targets for chronic viral infections and cancer. Understanding the mechanism of T cell exhaustion in response to chronic virus infections and cancer as well as the nature of restored T cell responses will contribute to further improvement of immune checkpoint blockade strategies.

Programmed Cell Death 1 (PD-1) and Cytotoxic T Lymphocyte-Associated Antigen 4 (CTLA-4) in Viral Hepatitis

Virus-specific cluster of differentiation 8 (CD8+) cytotoxic T cells (CTL) recognize viral antigens presented on major histocompatibility complex (MHC) class I chains on infected hepatocytes, with help from CD4+ T cells. However, this CTL response is frequently weak or undetectable in patients with chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. Programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) are receptors in the CD28 family of costimulatory molecules, providing inhibitory signals to T cells. The overexpressions of PD-1 and CTLA-4 in patients with viral infection have been shown to associate with functional impairment of virus-specific T cells. In acute viral hepatitis, PD-1 and CTLA-4 are up-regulated during the symptomatic phase, and then down-regulated after recovery. These findings suggest that PD-1 and CTLA-4 have protective effects as inhibitory molecules to suppress cytotoxic T cells which induce harmful destruction of viral infected hepatocytes in self-limited viral hepatitis. In chronic viral hepatitis, the extended upregulations of PD-1 and CTLA-4 are associated with T cell exhaustion and persistent viral infection, suggesting positive correlations between expression of immune inhibitory factors and the chronicity of viral disease. In this review, we summarize recent literature relating to PD-1, CTLA-4, and other inhibitory receptors in antigen-specific T cell exhaustion in viral hepatitis, including hepatitis A, B, C, and others.

The PD-1: PD-L1 pathway promotes development of brain-resident memory T cells following acute viral encephalitis

Background

Previous work from our laboratory has demonstrated that during acute viral brain infection, glial cells modulate antiviral T cell effector responses through the PD-1: PD-L1 pathway, thereby limiting the deleterious consequences of unrestrained neuroinflammation. Here, we evaluated the PD-1: PD-L1 pathway in development of brain-resident memory T cells (bT_RM) following murine cytomegalovirus (MCMV) infection.

Methods

Flow cytometric analysis of immune cells was performed at 7, 14, and 30 days post-infection (dpi) to assess the shift of brain-infiltrating CD8⁺ T cell populations from short-lived effector cells (SLEC) to memory precursor effector cells (MPEC), as well as generation of bT_RMs.

Results

In wild-type (WT) animals, we observed a switch in the phenotype of brain-infiltrating CD8⁺ T cell populations from KLRG1⁺ CD127⁻ (SLEC) to KLRG1⁻ CD127⁺ (MPEC) during transition from acute through chronic phases of infection. At 14 and 30 dpi, the majority of CD8⁺ T cells expressed CD127, a marker of memory cells. In contrast, fewer CD8⁺ T cells expressed CD127 within brains of infected, PD-L1 knockout (KO) animals. Notably, in WT mice, a large population of CD8⁺ T cells was phenotyped as CD103⁺ CD69⁺, markers of bT_RM, and differences were observed in the numbers of these cells when compared to PD-L1 KOs. Immunohistochemical studies revealed that brain-resident CD103⁺ bT_RM cells were localized to the parenchyma. Higher frequencies of CXCR3 were also observed among WT animals in contrast to PD-L1 KOs.

Conclusions

Taken together, our results indicate that bT_RMs are present within the CNS following viral infection and the PD-1: PD-L1 pathway plays a role in the generation of this brain-resident population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0860-3) contains supplementary material, which is available to authorized users.

The Balance between CD8+ T Cell-Mediated Clearance of AAV-Encoded Antigen in the Liver and Tolerance Is Dependent on the Vector Dose

The liver continuously receives antigens from circulation and the gastrointestinal tract. A complex immune regulatory system has evolved in order to both limit inflammation and promote tolerance in the liver. Although in situ immune tolerance mechanisms enable successful gene therapy and liver transplantation, at the same time they facilitate chronic infections by pathogens such as hepatitis viruses. It is, however, poorly understood why hepatocytes infected with hepatitis viruses or transduced with adeno-associated virus (AAV)-based vectors may be rejected by CD8⁺ T cells several months later. We found that hepatic transfer of limited doses of an AAV-ovalbumin vector rapidly induced antigen-specific CD8⁺ T cells that only became functionally competent after >2 months. At this time, CD8⁺ T cells had downregulated negative checkpoint markers, e.g., the programmed death 1 [PD-1] receptor, and upregulated expression of relevant cytokines. At further reduced vector dose, only intrahepatic rather than systemic CD8⁺ T cell responses occurred, showing identical delay in antigen clearance. In contrast, PD-1-deficient mice rapidly cleared ovalbumin. Interestingly, higher vector dose directed sustained transgene expression without CD8⁺ T cell responses. Regulatory T cells, IL-10 expression, and Fas-L contributed to high-dose tolerance. Thus, viral vector doses profoundly impact CD8⁺ T cell responses.

PD-1 mRNA expression in peripheral blood cells and its modulation characteristics in cancer patients

Immune checkpoint inhibitors that block the PD-1/PD-L1 signaling pathway have been used to treat a wide variety of cancers. Although results have been promising, significant inter-individual and inter-tumor variability has been observed. It is believed that better clinical outcome could be achieved if the treatment was individually designed based on the functional status of the PD-1/PD-L1 signaling and the cellular immunity. In this study, we analyzed the mRNA expression of PD-1 and other immunomodulatory genes in peripheral blood from cancer patients, and immunomodulatory gene expression during radiotherapy and immunomodulation therapy with cytokines. Our results show that the PD-1 mRNA expression is significantly increased in peripheral blood in cancer patients. Anti-cancer treatments can significantly modulate the PD-1 expression, but this is largely dependent on the initial immune status. Moreover, the PD-1 expression on peripheral lymphocytes can be immunoactivation-derived. These results suggest that the regulation and expression pattern of PD-1/PD-L1 signal is complicated which will influence the effect of blockade of the PD-1/PD-L1 signaling pathway for cancer treatment. Through combined analysis of PD-1, CTLA-4, and other immune markers in peripheral blood, we may accurately evaluate the functional status of PD-1/PD-L1 signaling and cellular immunity, thereby providing clues for guiding anti-PD-1 or anti-PD-L1 treatment.

Grating coupled SPR microarray analysis of proteins and cells in blood from mice with breast cancer

Biomarker discovery for early disease diagnosis is highly important. Of late, much effort has been made to analyze complex biological fluids in an effort to develop new markers specific for different cancer types. Recent advancements in label-free technologies such as surface plasmon resonance (SPR)-based biosensors have shown promise as a diagnostic tool since there is no need for labeling or separation of cells. Furthermore, SPR can provide rapid, real-time detection of antigens from biological samples since SPR is highly sensitive to changes in surface-associated molecular and cellular interactions. Herein, we report a lab-on-a-chip microarray biosensor that utilizes grating-coupled surface plasmon resonance (GCSPR) and grating-coupled surface plasmon coupled fluorescence (GCSPCF) imaging to detect circulating tumor cells (CTCs) from a mouse model (FVB-MMTV-PyVT). GCSPR and GCSPCF analysis was accomplished by spotting antibodies to surface cell markers, cytokines and stress proteins on a nanofabricated GCSPR microchip and screening blood samples from FVB control mice or FVB-MMTV-PyVT mice with developing mammary carcinomas. A transgenic MMTV-PyVT mouse derived cancer cell line was also analyzed. The analyses indicated that CD24, CD44, CD326, CD133 and CD49b were expressed in both cell lines and in blood from MMTV-PyVT mice. Furthermore, cytokines such as IL-6, IL-10 and TNF-α, along with heat shock proteins HSP60, HSP27, HSc70(HSP73), HSP90 total, HSP70/HSc70, HSP90, HSP70, HSP90 alpha, phosphotyrosine and HSF-1 were overexpressed in MMTV-PyVT mice.

Characterization of the Specificity, Functionality, and Durability of Host T-Cell Responses Against the Full-Length Hepatitis E Virus

The interplay between host antiviral immunity and immunopathology during hepatitis E virus (HEV) infection determines important clinical outcomes. We characterized the specificity, functionality, and durability of host T-cell responses against the full-length HEV virus and assessed a novel "Quantiferon" assay for the rapid diagnosis of HEV infection. Eighty-nine volunteers were recruited from Oxford, Truro (UK), and Toulouse (France), including 44 immune-competent patients with acute HEV infection, 18 HEV-exposed immunosuppressed organ-transplant recipients (8 with chronic HEV), and 27 healthy volunteers. A genotype 3a peptide library (616 overlapping peptides spanning open reading frames [ORFs] 1-3) was used in interferon-gamma (IFN-γ) T-cell ELISpot assays. CD4⁺ /CD8⁺ T-cell subsets and polyfunctionality were defined using ICCS and SPICE analysis. Quantification of IFN-γ used whole-blood stimulation with recombinant HEV-capsid protein in the QuantiFERON kit. HEV-specific T-cell responses were detected in 41/44 immune-competent HEV exposed volunteers (median magnitude: 397 spot-forming units/10⁶ peripheral blood mononuclear cells), most frequently targeting ORF2. High-magnitude, polyfunctional CD4 and CD8⁺ T cells were detected during acute disease and maintained to 12 years, but these declined over time, with CD8⁺ responses becoming more monofunctional. Low-level responses were detectable in immunosuppressed patients. Twenty-three novel HEV CD4⁺ and CD8⁺ T-cell targets were mapped predominantly to conserved genomic regions. QuantiFERON testing demonstrated an inverse correlation between IFN-γ production and the time from clinical presentation, providing 100% specificity, and 71% sensitivity (area under the receiver operator characteristic curve of 0.86) for HEV exposure at 0.3 IU/mL.

CONCLUSION

Robust HEV-specific T-cell responses generated during acute disease predominantly target ORF2, but decline in magnitude and polyfunctionality over time. Defining HEV T-cell targets will be important for the investigation of HEV-associated autoimmune disease. (Hepatology 2016;64:1934-1950).

Evolution in Our Understanding of Hepatitis B Virus Virology and Immunology

Hepatitis B virus (HBV) infection is a major global health challenge. HBV can cause significant morbidity and mortality by establishing acute and chronic hepatitis. Approximately 250 million people worldwide are chronically infected, and more than 2 billion people have been exposed to HBV. Since the discovery of HBV, the advances in our understanding of HBV virology and immunology have translated into effective vaccines and therapies for HBV infection. Although current therapies successfully suppress viral replication but rarely succeed in viral eradication, recent discoveries in HBV virology and immunology provide exciting rationales for novel treatment strategies aiming at HBV cure.

Hepatic expansion of virus-specific CD8+BTLA+ T cells with regulatory properties in chronic hepatitis B virus infection

Similar to programmed death-1 (PD-1), B and T lymphocyte attenuator (BTLA) is a co-inhibitory molecule of the CD28 family. PD-1 is involved in T cell exhaustion during chronic viral infection. However, the role of BTLA in virus-specific T cells is poorly defined. Here we investigated the expression and function of BTLA in T cells from patients with chronic hepatitis B virus (HBV) infection. The phenotype of peripheral and intrahepatic HBV-specific T cells from 43 patients with chronic HBV infection was assessed by flow cytometry. Functional evaluation was analyzed by T cell expansion and cytokine secretion after different treatments. In chronic HBV patients, a subset of inefficient interferon-γ producing antigen-specific CD8⁺ T cells recruited to the liver expressed high BTLA levels. The BTLA⁺ HBV-specific CD8⁺ T cell suppressive function was antigen-specific, at least in the induction phase, because they were only activated by a pool of HBV peptides but not with a pool of unrelated peptides. Suppression of T cell responses was restored by a BTLA signaling blockade and neutralizing IL-10, indicating that BTLA signaling-mediated IL-10 secretion plays a key role in suppression. This study provides important evidence that there is a subset of liver infiltrated virus-specific CD8⁺BTLA⁺ regulatory T cells in patients with chronic HBV infection. This subset of cells plays a pivotal role in controlling hepatic effector CD8⁺ T cell responses through BTLA signaling mediated regulatory factor IL-10 production.

Enhancement of Programmed Death Ligand 2 on Hepatitis C Virus Infected Hepatocytes by Calcineurin Inhibitors

Post orthotopic liver transplantation (OLT) viral hepatitis is an immunological condition where immune cells induce hepatitis during conditions of immune-suppression. The immune-regulatory programmed death-1 (PD-1)/PD-ligand 1 system is acknowledged to play important roles in immune-mediated diseases. However, the PD-1/PD-L2 interaction is not well characterized, with PD-L2 also exhibiting an immunostimulatory function. We hypothesized that this atypical molecule could affect the recurrence of post-OLT hepatitis. To test this hypothesis, we conducted immunohistochemical staining analysis and in vitro analysis of PD-L2.

Translational study of before and after liver transplantation for hepatitis B and C shows that calcineurin inhibitors (CNI) increase the expression of functional programmed death-1 on hepatocytes. The results suggest an important contribution of CNI on post transplant hepatitis occurrence and severity.

Immunodominant Dengue Virus-Specific CD8+ T Cell Responses Are Associated with a Memory PD-1+ Phenotype

Dengue disease is a large public health problem that mainly afflicts tropical and subtropical regions. Understanding of the correlates of protection against dengue virus (DENV) is poor and hinders the development of a successful human vaccine. The present study aims to define DENV-specific CD8(+)T cell responses in general and those of HLA alleles associated with dominant responses in particular. In human blood donors in Nicaragua, we observed a striking dominance of HLA B-restricted responses in general and of the allele B*35:01 in particular. Comparing these patterns to those in the general population of Sri Lanka, we found a strong correlation between restriction of the HLA allele and the breadth and magnitude of CD8(+)T cell responses, suggesting that HLA genes profoundly influence the nature of responses. The majority of gamma interferon (IFN-γ) responses were associated with effector memory phenotypes, which were also detected in non-B*35:01-expressing T cells. However, only the B*35:01 DENV-specific T cells were associated with marked expression of the programmed death 1 protein (PD-1). These cells did not coexpress other inhibitory receptors and were able to proliferate in response to DENV-specific stimulation. Thus, the expression of particular HLA class I alleles is a defining characteristic influencing the magnitude and breadth of CD8 responses, and a distinct, highly differentiated phenotype is specifically associated with dominant CD8(+)T cells. These results are of relevance for both vaccine design and the identification of robust correlates of protection in natural immunity.

IMPORTANCE

Dengue is an increasingly significant public health problem as its mosquito vectors spread over greater areas; no vaccines against the virus have yet been approved. An important step toward vaccine development is defining protective immune responses; toward that end, we here characterize the phenotype of the immunodominant T cell responses. These DENV-reactive T cells express high levels of the receptor programmed death 1 protein (PD-1), while those from disease-susceptible alleles do not. Not only does this represent a possible correlate of immunodominance, but it raises the hypothesis that PD-1 might be a regulator that prevents excessive damage while preserving antiviral function. Further, as this study employs distinct populations (Nicaraguan and Sri Lankan donors), we also confirmed that this pattern holds despite geographic and ethnic differences. This finding indicates that HLA type is the major determinant in shaping T cell responses.

American tegumentary leishmaniasis: T-cell differentiation profile of cutaneous and mucosal forms-co-infection with Trypanosoma cruzi

American tegumentary leishmaniasis displays two main clinical forms: cutaneous (CL) and mucosal (ML). ML is more resistant to treatment and displays a more severe and longer evolution. Since both forms are caused by the same Leishmania species, the immunological response of the host may be an important factor determining the evolution of the disease. Herein, we analyzed the differentiation and memory profile of peripheral CD4(+) and CD8(+) T lymphocytes of patients with CL and ML and their Leishmania-T. cruzi co-infected counterparts. We measured the expression of CD27, CD28, CD45RO, CD127, PD-1 and CD57, together with interferon-γ and perforin. A highly differentiated phenotype was reflected on both T subsets in ML and preferentially on CD8(+) T cells in CL. A positive trend toward a higher T differentiation profile was found in T. cruzi-infected CL and ML patients as compared with Leishmania single infections. Association between CD8(+) T-cell differentiation and illness duration was found within the first year of infection, with progressive increase of highly differentiated markers over time. Follow-up of patients with good response to therapy showed predominance of early differentiated CD8(+) T cells and decrease of highly differentiated cells, while patients with frequent relapses presented the opposite pattern. CD8(+) T cells showed the most striking changes in their phenotype during leishmaniasis. Patients with long-term infections showed the highest differentiated degree implying a relation between T differentiation and parasite persistence. Distinct patterns of CD8(+) T differentiation during follow-up of different clinical outcomes suggest the usefulness of this analysis in the characterization of Leishmania-infected patients.

Adaptive immunity in HBV infection

During hepatitis B virus (HBV) infection, the presence of HBV-specific antibody producing B cells and functional HBV-specific T cells (with helper or cytotoxic effects) ultimately determines HBV infection outcome. In this review, in addition to summarizing the present state of knowledge of HBV-adaptive immunity, we will highlight controversies and uncertainties concerning the HBV-specific B and T lymphocyte response, and propose future directions for research aimed at the generation of more efficient immunotherapeutic strategies.

Adaptive immunity in the liver

The anatomical architecture of the human liver and the diversity of its immune components endow the liver with its physiological function of immune competence. Adaptive immunity is a major arm of the immune system that is organized in a highly specialized and systematic manner, thus providing long-lasting protection with immunological memory. Adaptive immunity consists of humoral immunity and cellular immunity. Cellular immunity is known to have a crucial role in controlling infection, cancer and autoimmune disorders in the liver. In this article, we will focus on hepatic virus infections, hepatocellular carcinoma and autoimmune disorders as examples to illustrate the current understanding of the contribution of T cells to cellular immunity in these maladies. Cellular immune suppression is primarily responsible for chronic viral infections and cancer. However, an uncontrolled auto-reactive immune response accounts for autoimmunity. Consequently, these immune abnormalities are ascribed to the quantitative and functional changes in adaptive immune cells and their subsets, innate immunocytes, chemokines, cytokines and various surface receptors on immune cells. A greater understanding of the complex orchestration of the hepatic adaptive immune regulators during homeostasis and immune competence are much needed to identify relevant targets for clinical intervention to treat immunological disorders in the liver.

The Association Between Viral Infections and Co-stimulatory Gene Polymorphisms in Kidney Transplant Outcomes

Background

The surveillance of kidney transplant patients depends on function of different immunologic markers like co-stimulatory molecules. These molecules may also be associated with post kidney transplant viral related outcomes.

Objectives

The aim of this study was to investigate the possible associations between co-stimulatory molecule gene polymorphisms and viral infections in kidney transplant patients.

Patients and Methods

In total, 172 kidney transplant patients were included in this study. Single nucleotide polymorphisms in loci of co-stimulatory molecules including: PDCD.1, CD28, CTLA4 and ICOS, were analyzed in the studied patients by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Active Cytomegalovirus (CMV) infection and history of hepatitis C virus (HCV) infection were analyzed in each kidney transplant patient using the CMV antigenemia kit and HCV antibody assay, according to the manufacturer’s instructions.

Results

CMV active infection was found in 31 of 172 (18.02%) kidney transplant patients. HCV infection was only found in two of the 172 (1.16%) studied patients. Significant associations were found between TT and TC genotypes of CTLA4 -1722T/C and T allele with acute rejection in CMV infected kidney transplant patients. A significant association was also found between the T allele of CD28 + 17 C/T genetic polymorphism and acute rejection in CMV infected kidney transplant patients. Significantly higher frequency of AA genotype and A allele of CTLA4 + 49AG polymorphism were found in CMV infected female patients. Also a significantly higher frequency of GG genotype and G allele of PDCD-1.3A/G polymorphisms were found in CMV infected female patients.

Conclusions

Based on these results, CTLA4 and CD28 genetic polymorphisms, which regulate T-cell activation, can influence active CMV infection in kidney transplant patients. These results should be confirmed by further investigations.

Regulation of CD8+ T-cell cytotoxicity in HIV-1 infection

Understanding the mechanisms involved in cellular immune responses against control of human immunodeficiency virus (HIV) infection is key to development of effective immunotherapeutic strategies against viral proliferation. Clear insights into the regulation of cytotoxic CD8+ T cells is crucial to development of effective immunotherapeutic strategies due to their unique ability to eliminate virus-infected cells during the course of infection. Here, we reviewed the roles of transcription factors, co-inhibitory molecules and regulatory cytokines following HIV infection and their potential significance in regulating the cytotoxic potentials of CD8+ T cells.