Dynamics and genomic landscape of CD8+ T cells undergoing hepatic priming

IL-2-mediated hepatotoxicity: knowledge gap identification based on the irAOP concept

Drug-induced hepatotoxicity constitutes a major reason for non-approval and post-marketing withdrawal of pharmaceuticals. In many cases, preclinical models lack predictive capacity for hepatic damage in humans. A vital concern is the integration of immune system effects in preclinical safety assessment. The immune-related Adverse Outcome Pathway (irAOP) approach, which is applied within the Immune Safety Avatar (imSAVAR) consortium, presents a novel method to understand and predict immune-mediated adverse events elicited by pharmaceuticals and thus targets this issue. It aims to dissect the molecular mechanisms involved and identify key players in drug-induced side effects. As irAOPs are still in their infancy, there is a need for a model irAOP to validate the suitability of this tool. For this purpose, we developed a hepatotoxicity-based model irAOP for recombinant human IL-2 (aldesleukin). Besides producing durable therapeutic responses against renal cell carcinoma and metastatic melanoma, the boosted immune activation upon IL-2 treatment elicits liver damage. The availability of extensive data regarding IL-2 allows both the generation of a comprehensive putative irAOP and to validate the predictability of the irAOP with clinical data. Moreover, IL-2, as one of the first cancer immunotherapeutics on the market, is a blueprint for various biological and novel treatment regimens that are under investigation today. This review provides a guideline for further irAOP-directed research in immune-mediated hepatotoxicity.

A liver immune rheostat regulates CD8 T cell immunity in chronic HBV infection

Chronic hepatitis B virus (HBV) infection affects 300 million patients worldwide1,2, in whom virus-specific CD8 T cells by still ill-defined mechanisms lose their function and cannot eliminate HBV-infected hepatocytes3-7. Here we demonstrate that a liver immune rheostat renders virus-specific CD8 T cells refractory to activation and leads to their loss of effector functions. In preclinical models of persistent infection with hepatotropic viruses such as HBV, dysfunctional virus-specific CXCR6+ CD8 T cells accumulated in the liver and, as a characteristic hallmark, showed enhanced transcriptional activity of cAMP-responsive element modulator (CREM) distinct from T cell exhaustion. In patients with chronic hepatitis B, circulating and intrahepatic HBV-specific CXCR6+ CD8 T cells with enhanced CREM expression and transcriptional activity were detected at a frequency of 12-22% of HBV-specific CD8 T cells. Knocking out the inhibitory CREM/ICER isoform in T cells, however, failed to rescue T cell immunity. This indicates that CREM activity was a consequence, rather than the cause, of loss in T cell function, further supported by the observation of enhanced phosphorylation of protein kinase A (PKA) which is upstream of CREM. Indeed, we found that enhanced cAMP-PKA-signalling from increased T cell adenylyl cyclase activity augmented CREM activity and curbed T cell activation and effector function in persistent hepatic infection. Mechanistically, CD8 T cells recognizing their antigen on hepatocytes established close and extensive contact with liver sinusoidal endothelial cells, thereby enhancing adenylyl cyclase-cAMP-PKA signalling in T cells. In these hepatic CD8 T cells, which recognize their antigen on hepatocytes, phosphorylation of key signalling kinases of the T cell receptor signalling pathway was impaired, which rendered them refractory to activation. Thus, close contact with liver sinusoidal endothelial cells curbs the activation and effector function of HBV-specific CD8 T cells that target hepatocytes expressing viral antigens by means of the adenylyl cyclase-cAMP-PKA axis in an immune rheostat-like fashion.

Major open questions in the hepatitis B and D field - Proceedings of the inaugural International emerging hepatitis B and hepatitis D researchers workshop

The early and mid-career researchers (EMCRs) of scientific communities represent the forefront of research and the future direction in which a field takes. The opinions of this key demographic are not commonly aggregated to audit fields and precisely demonstrate where challenges lie for the future. To address this, we initiated the inaugural International Emerging Researchers Workshop for the global Hepatitis B and Hepatitis D scientific community (75 individuals). The cohort was split into small discussion groups and the significant problems, challenges, and future directions were assessed. Here, we summarise the outcome of these discussions and outline the future directions suggested by the EMCR community. We show an effective approach to gauging and accumulating the ideas of EMCRs and provide a succinct summary of the significant gaps remaining in the Hepatitis B and Hepatitis D field.

Harnessing CD8+ T cell dynamics in hepatitis B virus-associated liver diseases: Insights, therapies and future directions

Hepatitis B virus (HBV) infection playsa significant role in the etiology and progression of liver-relatedpathologies, encompassing chronic hepatitis, fibrosis, cirrhosis, and eventual hepatocellularcarcinoma (HCC). Notably, HBV infection stands as the primary etiologicalfactor driving the development of HCC. Given the significant contribution ofHBV infection to liver diseases, a comprehensive understanding of immunedynamics in the liver microenvironment, spanning chronic HBV infection,fibrosis, cirrhosis, and HCC, is essential. In this review, we focused on thefunctional alterations of CD8+ T cells within the pathogenic livermicroenvironment from HBV infection to HCC. We thoroughly reviewed the roles ofhypoxia, acidic pH, metabolic reprogramming, amino acid deficiency, inhibitory checkpointmolecules, immunosuppressive cytokines, and the gut-liver communication in shapingthe dysfunction of CD8+ T cells in the liver microenvironment. Thesefactors significantly impact the clinical prognosis. Furthermore, we comprehensivelyreviewed CD8+ T cell-based therapy strategies for liver diseases,encompassing HBV infection, fibrosis, cirrhosis, and HCC. Strategies includeimmune checkpoint blockades, metabolic T-cell targeting therapy, therapeuticT-cell vaccination, and adoptive transfer of genetically engineered CD8+ T cells, along with the combined usage of programmed cell death protein-1/programmeddeath ligand-1 (PD-1/PD-L1) inhibitors with mitochondria-targeted antioxidants.Given that targeting CD8+ T cells at various stages of hepatitis Bvirus-induced hepatocellular carcinoma (HBV + HCC) shows promise, we reviewedthe ongoing need for research to elucidate the complex interplay between CD8+ T cells and the liver microenvironment in the progression of HBV infection toHCC. We also discussed personalized treatment regimens, combining therapeuticstrategies and harnessing gut microbiota modulation, which holds potential forenhanced clinical benefits. In conclusion, this review delves into the immunedynamics of CD8+ T cells, microenvironment changes, and therapeuticstrategies within the liver during chronic HBV infection, HCC progression, andrelated liver diseases.

Optimized RNA interference therapeutics combined with interleukin-2 mRNA for treating hepatitis B virus infection

This study aimed to develop a pan-genotypic and multifunctional small interfering RNA (siRNA) against hepatitis B virus (HBV) with an efficient delivery system for treating chronic hepatitis B (CHB), and explore combined RNA interference (RNAi) and immune modulatory modalities for better viral control. Twenty synthetic siRNAs targeting consensus motifs distributed across the whole HBV genome were designed and evaluated. The lipid nanoparticle (LNP) formulation was optimized by adopting HO-PEG2000-DMG lipid and modifying the molar ratio of traditional polyethylene glycol (PEG) lipid in LNP prescriptions. The efficacy and safety of this formulation in delivering siHBV (tLNP/siHBV) along with the mouse IL-2 (mIL-2) mRNA (tLNP/siHBVIL2) were evaluated in the rAAV-HBV1.3 mouse model. A siRNA combination (terms "siHBV") with a genotypic coverage of 98.55% was selected, chemically modified, and encapsulated within an optimized LNP (tLNP) of high efficacy and security to fabricate a therapeutic formulation for CHB. The results revealed that tLNP/siHBV significantly reduced the expression of viral antigens and DNA (up to 3log10 reduction; vs PBS) in dose- and time-dependent manners at single-dose or multi-dose frequencies, with satisfactory safety profiles. Further studies showed that tLNP/siHBVIL2 enables additive antigenic and immune control of the virus, via introducing potent HBsAg clearance through RNAi and triggering strong HBV-specific CD4+ and CD8+ T cell responses by expressed mIL-2 protein. By adopting tLNP as nucleic acid nanocarriers, the co-delivery of siHBV and mIL-2 mRNA enables synergistic antigenic and immune control of HBV, thus offering a promising translational therapeutic strategy for treating CHB.

Therapeutic potential of co-signaling receptor modulation in hepatitis B

Reversing CD8+ T cell dysfunction is crucial in treating chronic hepatitis B virus (HBV) infection, yet specific molecular targets remain unclear. Our study analyzed co-signaling receptors during hepatocellular priming and traced the trajectory and fate of dysfunctional HBV-specific CD8+ T cells. Early on, these cells upregulate PD-1, CTLA-4, LAG-3, OX40, 4-1BB, and ICOS. While blocking co-inhibitory receptors had minimal effect, activating 4-1BB and OX40 converted them into antiviral effectors. Prolonged stimulation led to a self-renewing, long-lived, heterogeneous population with a unique transcriptional profile. This includes dysfunctional progenitor/stem-like (TSL) cells and two distinct dysfunctional tissue-resident memory (TRM) populations. While 4-1BB expression is ubiquitously maintained, OX40 expression is limited to TSL. In chronic settings, only 4-1BB stimulation conferred antiviral activity. In HBeAg+ chronic patients, 4-1BB activation showed the highest potential to rejuvenate dysfunctional CD8+ T cells. Targeting all dysfunctional T cells, rather than only stem-like precursors, holds promise for treating chronic HBV infection.

The lack of HBsAg secretion does neither facilitate induction of antiviral T cell responses nor Hepatitis B Virus clearance in mice

Immune tolerance to the hepatitis B virus (HBV) is crucial for developing chronic hepatitis B, and the HBV surface antigen (HBsAg) produced and secreted in high amounts is regarded as a key contributor. HBsAg is expressed in HBV-infected hepatocytes and those carrying an HBV integration. Whether either HBsAg secretion or the high antigen amount expressed in the liver determines its immunomodulatory properties, however, remains unclear. We, therefore, developed a novel HBV animal model that allowed us to study the role of secreted HBsAg. We introduced a previously described HBs mutation, C65S, abolishing HBsAg secretion into a replication-competent 1.3-overlength HBV genome and used adeno-associated virus vectors to deliver it to the mouse liver. The AAV-HBV established a carrier state of wildtype and C65S mutant HBV, respectively. We investigated antiviral B- and T-cell immunity in the HBV-carrier mice after therapeutic vaccination. Moreover, we compared the effect of a lacking HBsAg secretion with that of an antiviral siRNA. While missing HBsAg secretion allowed for higher levels of detectable anti-HBs antibodies after therapeutic vaccination, it did neither affect antiviral T-cell responses nor intrahepatic HBV gene expression, irrespective of the starting level. A treatment with HBV siRNA restricting viral antigen expression within hepatocytes, however, improved the antiviral efficacy of therapeutic vaccination, irrespective of the ability of HBV to secrete HBsAg. Our data indicate that clearing HBsAg from blood cannot significantly impact HBV persistence or T-cell immunity. This indicates that a restriction of hepatic viral antigen expression will be required to break HBV immunotolerance.

Intravital imaging: dynamic insights into liver immunity in health and disease

Inflammation is a critical component of most acute and chronic liver diseases. The liver is a unique immunological organ with a dense vascular network, leading to intense crosstalk between tissue-resident immune cells, passenger leucocytes and parenchymal cells. During acute and chronic liver diseases, the multifaceted immune response is involved in disease promoting and repair mechanisms, while upholding core liver immune functions. In recent years, single-cell technologies have unravelled a previously unknown heterogeneity of immune cells, reshaping the complexity of the hepatic immune response. However, inflammation is a dynamic biological process, encompassing various immune cells, orchestrated in temporal and spatial dimensions, and driven by multiorgan signals. Intravital microscopy (IVM) has emerged as a powerful tool to investigate immunity by visualising the dynamic interplay between different immune cells and their surroundings within a near-natural environment. In this review, we summarise the experimental considerations to perform IVM and highlight recent technological developments. Furthermore, we outline the unique contributions of IVM to our understanding of liver immunity. Through the lens of liver disease, we discuss novel immune-mediated disease mechanisms uncovered by imaging-based studies.

Preclinical evaluation of therapeutic vaccines for chronic hepatitis B that stimulate antiviral activities of T cells and NKT cells

Background & Aims

Liver diseases resulting from chronic HBV infection are a significant cause of morbidity and mortality. Vaccines that elicit T-cell responses capable of controlling the virus represent a treatment strategy with potential for long-term effects. Here, we evaluated vaccines that induce the activity of type I natural killer T (NKT) cells to limit viral replication and license stimulation of conventional antiviral T-cells.

Methods

Vaccines were prepared by conjugating peptide epitopes to an NKT-cell agonist to promote co-delivery to antigen-presenting cells, encouraging NKT-cell licensing and stimulation of T cells. Activity of the conjugate vaccines was assessed in transgenic mice expressing the complete HBV genome, administered intravenously to maximise access to NKT cell-rich tissues.

Results

The vaccines induced only limited antiviral activity in unmanipulated transgenic hosts, likely attributable to NKT-cell activation as T-cell tolerance to viral antigens is strong. However, in a model of chronic hepatitis B involving transfer of naive HBcAg-specific CD8+ T cells into the transgenic mice, which typically results in specific T-cell dysfunction without virus control, vaccines containing the targeted HBcAg epitope induced prolonged antiviral activity because of qualitatively improved T-cell stimulation. In a step towards a clinical product, vaccines were prepared using synthetic long peptides covering clusters of known HLA-binding epitopes and shown to be immunogenic in HLA transgenic mice. Predictions based on HLA distribution suggest a product containing three selected SLP-based vaccines could give >90 % worldwide coverage, with an average of 3.38 epitopes targeted per individual.

Conclusions

The novel vaccines described show promise for further clinical development as a treatment for chronic hepatitis B.

Impact and Implications

Although there are effective prophylactic vaccines for HBV infection, it is estimated that 350-400 million people worldwide have chronic hepatitis B, putting these individuals at significant risk of life-threatening liver diseases. Therapeutic vaccination aimed at activating or boosting HBV-specific T-cell responses holds potential as a strategy for treating chronic infection, but has so far met with limited success. Here, we show that a glycolipid-peptide conjugate vaccine designed to coordinate activity of type I NKT cells alongside conventional antiviral T cells has antiviral activity in a mouse model of chronic infection. It is anticipated that a product based on a combination of three such conjugates, each prepared using long peptides covering clusters of known HLA-binding epitopes, could be developed further as a treatment for chronic hepatitis B with broad global HLA coverage.

Single-cell RNA-sequencing of virus-specific cellular immune responses in chronic hepatitis B patients

Chronic hepatitis B (CHB) is a major global health challenge. CHB can be controlled by antivirals but a therapeutic cure is lacking. CHB is characterized by limited HBV-specific T cell reactivity and functionality and expression of inhibitory receptors. The mechanisms driving these T cell phenotypes are only partially understood. Here, we created a single-cell RNA-sequencing dataset of HBV immune responses in patients to contribute to a better understanding of the dysregulated immunity. Blood samples of a well-defined cohort of 21 CHB and 10 healthy controls, including a subset of 5 matched liver biopsies, were collected. scRNA-seq data of total immune cells (55,825) plus sorted HBV-specific (1,963), non-naive (32,773) and PD1+ T cells (96,631) was generated using the 10X Genomics platform (186,123 cells) or the full-length Smart-seq2 protocol (1,069 cells). The shared transcript count matrices of single-cells serve as a valuable resource describing transcriptional changes underlying dysfunctional HBV-related T cell responses in blood and liver tissue and offers the opportunity to identify targets or biomarkers for HBV-related immune exhaustion.

Cellular strategies to induce immune tolerance after liver transplantation: Clinical perspectives

Liver transplantation (LT) has become the most efficient treatment for pediatric and adult end-stage liver disease and the survival time after transplantation is becoming longer due to the development of surgical techniques and perioperative management. However, long-term side-effects of immunosuppressants, like infection, metabolic disorders and malignant tumor are gaining more attention. Immune tolerance is the status in which LT recipients no longer need to take any immunosuppressants, but the liver function and intrahepatic histology maintain normal. The approaches to achieve immune tolerance after transplantation include spontaneous, operational and induced tolerance. The first two means require no specific intervention but withdrawing immunosuppressant gradually during follow-up. No clinical factors or biomarkers so far could accurately predict who are suitable for immunosuppressant withdraw after transplantation. With the understanding to the underlying mechanisms of immune tolerance, many strategies have been developed to induce tolerance in LT recipients. Cellular strategy is one of the most promising methods for immune tolerance induction, including chimerism induced by hematopoietic stem cells and adoptive transfer of regulatory immune cells. The safety and efficacy of various cell products have been evaluated by prospective preclinical and clinical trials, while obstacles still exist before translating into clinical practice. Here, we will summarize the latest perspectives and concerns on the clinical application of cellular strategies in LT recipients.

Antibody-independent protection against heterologous SARS-CoV-2 challenge conferred by prior infection or vaccination

Vaccines have reduced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) morbidity and mortality, yet emerging variants challenge their effectiveness. The prevailing approach to updating vaccines targets the antibody response, operating under the presumption that it is the primary defense mechanism following vaccination or infection. This perspective, however, can overlook the role of T cells, particularly when antibody levels are low or absent. Here we show, through studies in mouse models lacking antibodies but maintaining functional B cells and lymphoid organs, that immunity conferred by prior infection or mRNA vaccination can protect against SARS-CoV-2 challenge independently of antibodies. Our findings, using three distinct models inclusive of a novel human/mouse ACE2 hybrid, highlight that CD8+ T cells are essential for combating severe infections, whereas CD4+ T cells contribute to managing milder cases, with interferon-γ having an important function in this antibody-independent defense. These findings highlight the importance of T cell responses in vaccine development, urging a broader perspective on protective immunity beyond just antibodies.

Macrophage migration inhibitory factor blockade reprograms macrophages and disrupts prosurvival signaling in acute myeloid leukemia

The malignant microenvironment plays a major role in the development of resistance to therapies and the occurrence of relapses in acute myeloid leukemia (AML). We previously showed that interactions of AML blasts with bone marrow macrophages (MΦ) shift their polarization towards a protumoral (M2-like) phenotype, promoting drug resistance; we demonstrated that inhibiting the colony-stimulating factor-1 receptor (CSF1R) repolarizes MΦ towards an antitumoral (M1-like) phenotype and that other factors may be involved. We investigated here macrophage migration inhibitory factor (MIF) as a target in AML blast survival and protumoral interactions with MΦ. We show that pharmacologically inhibiting MIF secreted by AML blasts results in their apoptosis. However, this effect is abrogated when blasts are co-cultured in close contact with M2-like MΦ. We next demonstrate that pharmacological inhibition of MIF secreted by MΦ, in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF), efficiently reprograms MΦ to an M1-like phenotype that triggers apoptosis of interacting blasts. Furthermore, contact with reprogrammed MΦ relieves blast resistance to venetoclax and midostaurin acquired in contact with CD163+ protumoral MΦ. Using intravital imaging in mice, we also show that treatment with MIF inhibitor 4-IPP and GM-CSF profoundly affects the tumor microenvironment in vivo: it strikingly inhibits tumor vasculature, reduces protumoral MΦ, and slows down leukemia progression. Thus, our data demonstrate that MIF plays a crucial role in AML MΦ M2-like protumoral phenotype that can be reversed by inhibiting its activity and suggest the therapeutic targeting of MIF as an avenue towards improved AML treatment outcomes.

A hepatic network of dendritic cells mediates CD4 T cell help outside lymphoid organs

While CD4+ T cells are a prerequisite for CD8+ T cell-mediated protection against intracellular hepatotropic pathogens, the mechanisms facilitating the transfer of CD4-help to intrahepatic CD8+ T cells are unknown. Here, we developed an experimental system to investigate cognate CD4+ and CD8+ T cell responses to a model-antigen expressed de novo in hepatocytes and reveal that after initial priming, effector CD4+ and CD8+ T cells migrate into portal tracts and peri-central vein regions of the liver where they cluster with type-1 conventional dendritic cells. These dendritic cells are locally licensed by CD4+ T cells and expand the number of CD8+ T cells in situ, resulting in larger effector and memory CD8+ T cell pools. These findings reveal that CD4+ T cells promote intrahepatic immunity by amplifying the CD8+ T cell response via peripheral licensing of hepatic type-1 conventional dendritic cells and identify intrahepatic perivascular compartments specialized in facilitating effector T cell-dendritic cell interactions.

Single-cell atlas reveals characteristic changes in intrahepatic HBV-specific leukocytes

IMPORTANCE

Hepatitis B virus (HBV)-specific CD8+ T cells play a central role in the clearance of virus and HBV-related liver injury. Acute infection with HBV induces a vigorous, multifunctional CD8+ T cell response, whereas chronic one exhibits a weaker response. Our study elucidated HBV-specific T cell responses in terms of viral abundance rather than the timing of infection. We showed that in the premalignant stage, the degree of impaired T cell function was not synchronized with the viral surface antigen, which was attributed the liver's tolerance to the virus. However, after the development of hepatocellular carcinoma, T cell exhaustion was inevitable, and it was marked by the exhaustion of the signature transcription factor TOX.

CD8 cis-targeted IL-2 drives potent antiviral activity against hepatitis B virus

CD8+ T cells are key antiviral effectors against hepatitis B virus (HBV), yet their number and function can be compromised in chronic infections. Preclinical HBV models displaying CD8+ T cell dysfunction showed that interleukin-2 (IL-2)-based treatment, unlike programmed cell death ligand 1 (PD-L1) checkpoint blockade, could reverse this defect, suggesting its therapeutic potential against HBV. However, IL-2's effectiveness is hindered by its pleiotropic nature, because its receptor is found on various immune cells, including regulatory T (Treg) cells and natural killer (NK) cells, which can counteract antiviral responses or contribute to toxicity, respectively. To address this, we developed a cis-targeted CD8-IL2 fusion protein, aiming to selectively stimulate dysfunctional CD8+ T cells in chronic HBV. In a mouse model, CD8-IL2 boosted the number of HBV-reactive CD8+ T cells in the liver without substantially altering Treg or NK cell counts. These expanded CD8+ T cells exhibited increased interferon-γ and granzyme B production, demonstrating enhanced functionality. CD8-IL2 treatment resulted in substantial antiviral effects, evidenced by marked reductions in viremia and antigenemia and HBV core antigen-positive hepatocytes. In contrast, an untargeted CTRL-IL2 led to predominant NK cell expansion, minimal CD8+ T cell expansion, negligible changes in effector molecules, and minimal antiviral activity. Human CD8-IL2 trials in cynomolgus monkeys mirrored these results, achieving a roughly 20-fold increase in peripheral blood CD8+ T cells without affecting NK or Treg cell numbers. These data support the development of CD8-IL2 as a therapy for chronic HBV infection.

Therapeutic vaccination with lentiviral vector in HBV-persistent mice and two inactive HBsAg carriers

BACKGROUND & AIMS

Immunotherapy for chronic hepatitis B virus (HBV) infection has not yet demonstrated sufficient efficacy. We developed a non-integrative lentiviral-vectored therapeutic vaccine for chronic hepatitis B and tested its antiviral effects in HBV-persistent mice and two inactive HBsAg carriers.

METHODS

Lentiviral vectors (LVs) encoding the core, preS1, or large HBsAg (LHBs) proteins of HBV were evaluated for immunogenicity in HBV-naïve mice and therapeutic efficacy in a murine model of chronic HBV infection. In addition, two inactive HBsAg carriers each received two doses of 5×107 transduction units (TU) or 1×108 TU of lentiviral-vectored LHBs (LV-LHBs), respectively. The endpoints were safety, LHBs-specific T-cell responses, and serum HBsAg levels during a 24-week follow-up.

RESULTS

In the mouse models, LV-LHBs was the most promising in eliciting robust antigen-specific T cells and in reducing the levels of serum HBsAg and viral load. By the end of the 34-week observation period, six out of ten (60%) HBV-persistent mice vaccinated with LV-LHBs achieved serum HBsAg loss and significant depletion of HBV-positive hepatocytes in the liver. In the two inactive HBsAg carriers, vaccination with LV-LHBs induced a considerable increase in the number of peripheral LHBs-specific T cells in one patient, and a weak but detectable response in the other, accompanied by a sustained reduction of HBsAg (-0.31 log10 IU/ml and -0.46 log10 IU/ml, respectively) from baseline to nadir.

CONCLUSIONS

A lentiviral-vectored therapeutic vaccine for chronic HBV infection demonstrated the potential to improve HBV-specific T-cell responses and deplete HBV-positive hepatocytes, leading to a sustained loss or reduction of serum HBsAg.

IMPACT AND IMPLICATIONS

Chronic HBV infection is characterized by an extremely low number and profound hypo-responsiveness of HBV-specific T cells. Therapeutic vaccines are designed to improve HBV-specific T-cell responses. We show that immunization with a lentiviral-vectored therapeutic HBV vaccine was able to expand HBV-specific T cells in vivo, leading to reductions of HBV-positive hepatocytes and serum HBsAg.

Targeting virus-specific CD8+ T cells for treatment of chronic viral hepatitis: from bench to bedside

INTRODUCTION

More than 350 million people worldwide live with chronic viral hepatitis and are thus at risk for severe complications like liver cirrhosis and hepatocellular carcinoma (HCC). To meet the goals of the World Health Organization (WHO) global hepatitis strategy, there is an urgent need for new immunotherapeutic approaches. These are particularly required for chronic hepatitis B virus infection and - B/D coinfection.

AREAS COVERED

This review summarizes data on mechanisms of CD8+ T cells failure in chronic hepatitis B, D, C and E virus infection. The relative contribution of the different concepts (viral escape, CD8+ T cell exhaustion, defective priming) will be discussed. On this basis, examples for future therapeutic approaches targeting virus-specific CD8+ T cells for the individual hepatitis viruses will be discussed.

EXPERT OPINION

Immunotherapeutic approaches targeting virus-specific CD8+ T cells have the potential to change clinical practice, especially in chronic hepatitis B virus infection. Further clinical development, however, requires a more detailed understanding of T cell immunology in chronic viral hepatitis. Some important conceptual questions remain to be addressed, e.g. regarding heterogeneity of exhausted virus-specific CD8+ T cells.

How does TCR-T cell therapy exhibit a superior anti-tumor efficacy

TCR-engineered T cells have achieved great progress in solid tumor therapy, some of which have been applicated in clinical trials. Deep knowledge about the current progress of TCR-T in tumor therapy would be beneficial to understand the direction. Here, we classify tumor antigens into tumor-associated antigens, tumor-specific antigens, tumor antigens expressed by oncogenic viruses, and tumor antigens caused by abnormal protein modification; Then we detail the TCR-T cell therapy effects targeting those tumor antigens in clinical or preclinical trials, and propose that neoantigen specific TCR-T cell therapy is expected to be a promising approach for solid tumors; Furthermore, we summarize the optimization strategies, such as tumor microenvironment, TCR pairing and affinity, to improve the therapeutic effect of TCR-T. Overall, this review provides inspiration for the antigen selection and therapy strategies of TCR-T in the future.

Recent advances in understanding T cell activation and exhaustion during HBV infection

Chronic hepatitis B virus (HBV) infection remains a major public health concern globally, and T cell responses are widely believed to play a pivotal role in mediating HBV clearance. Accordingly, research on the characteristics of HBV-specific T cell responses, from activation to exhaustion, has advanced rapidly. Here, we summarize recent developments in characterizing T cell immunity in HBV infection by reviewing basic and clinical research published in the last five years. We provide a comprehensive summary of the mechanisms that induce effective anti-HBV T cell immunity, as well as the latest developments in understanding T cell dysfunction in chronic HBV infection. Furthermore, we briefly discuss current novel treatment strategies aimed at restoring anti-HBV T cell responses.

Current limitations of gene therapy for rare pediatric diseases: Lessons learned from clinical experience with AAV vectors

Gene therapy using adeno-associated viral (AAV) vectors is a promising therapeutic strategy for multiple inherited diseases. Following intravenous injection, AAV vectors carrying a copy of the missing gene or the genome-editing machinery reach their target cells and deliver the genetic material. Several clinical trials are currently ongoing and significant success has already been achieved with at least six AAV gene therapy products with market approval in Europe and the United States. Nonetheless, clinical trials and preclinical studies have uncovered several limitations of AAV gene transfer, which need to be addressed in order to improve the safety and enable the treatment of the largest patient population. Limitations include the occurrence of immune-mediated toxicities, the potential loss of correction in the long run, and the development of neutralizing antibodies against AAV vectors preventing re-administration. In this review, we summarize these limitations and discuss the potential technological developments to overcome them. © 2023 Published by Elsevier Masson SAS on behalf of French Society of Pediatrics.

Cardinal features of immune memory in innate lymphocytes

The ability of vertebrates to 'remember' previous infections had once been attributed exclusively to adaptive immunity. We now appreciate that innate lymphocytes also possess memory properties akin to those of adaptive immune cells. In this Review, we draw parallels from T cell biology to explore the key features of immune memory in innate lymphocytes, including quantity, quality, and location. We discuss the signals that trigger clonal or clonal-like expansion in innate lymphocytes, and highlight recent studies that shed light on the complex cellular and molecular crosstalk between metabolism, epigenetics, and transcription responsible for differentiating innate lymphocyte responses towards a memory fate. Additionally, we explore emerging evidence that activated innate lymphocytes relocate and establish themselves in specific peripheral tissues during infection, which may facilitate an accelerated response program akin to those of tissue-resident memory T cells.

What Is the Current Status of Hepatitis B Virus Viro-Immunology?

The natural history of hepatitis B virus (HBV) infection is closely dependent on the dynamic interplay between the host immune response and viral replication. Spontaneous HBV clearance in acute self-limited infection is the result of an adequate and efficient antiviral immune response. Instead, it is widely recognized that in chronic HBV infection, immunologic dysfunction contributes to viral persistence. Long-lasting exposure to high viral antigens, upregulation of multiple co-inhibitory receptors, dysfunctional intracellular signaling pathways and metabolic alterations, and intrahepatic regulatory mechanisms have been described as features ultimately leading to a hierarchical loss of effector functions up to full T-cell exhaustion.

Possibility of PD-1/PD-L1 Inhibitors for the Treatment of Patients with Chronic Hepatitis B Infection

BACKGROUND

Chronic hepatitis B (CHB) infection is still a major global public health problem, with nearly two billion patients. Although current antiviral drugs can inhibit viral replication and reduce hepatitis B virus (HBV) related complications, it is difficult to achieve clinical endpoints due to drug resistance.

SUMMARY

Immune checkpoint inhibitors (ICIs) are an important strategy to reverse T-cell exhaustion, and rebuilding an effective functional T-cell response is a promising immunomodulatory approach for CHB patients. However, ICIs may lead to viral reactivation or immune-related adverse effects. There are still many controversies in the application of ICIs in treating patients with CHB.

KEY MESSAGES

This article reviews the research progress of ICIs in CHB infection and related issues. The goal of this paper was to summarize the possible impact of new therapies for CHB with the aim of reducing potential clinical risks.

Tissue-resident and innate-like T cells in patients with advanced chronic liver disease

Chronic liver disease results from the orchestrated interplay of components of innate and adaptive immunity in response to liver tissue damage. Recruitment, positioning, and activation of immune cells can contribute to hepatic cell death, inflammation, and fibrogenesis. With disease progression and increasing portal pressure, repeated translocation of bacterial components from the intestinal lumen through the epithelial and vascular barriers leads to persistent mucosal, hepatic, and systemic inflammation which contributes to tissue damage, immune dysfunction, and microbial infection. It is increasingly recognised that innate-like and adaptive T-cell subsets located in the liver, mucosal surfaces, and body cavities play a critical role in the progression of advanced liver disease and inflammatory complications of cirrhosis. Mucosal-associated invariant T cells, natural killer T cells, γδ T cells, and tissue-resident memory T cells in the gut, liver, and ascitic fluid share certain characteristic features, which include that they recognise microbial products, tissue alarmins, cytokines, and stress ligands in tissues, and perform effector functions in chronic liver disease. This review highlights recent advances in the comprehension of human tissue-resident and unconventional T-cell populations and discusses the mechanisms by which they contribute to inflammation, fibrosis, immunosuppression, and antimicrobial surveillance in patients with cirrhosis. Understanding the complex interactions of immune cells in different compartments and their contribution to disease progression will provide further insights for effective diagnostic interventions and novel immunomodulatory strategies in patients with advanced chronic liver disease.

Hepatic inflammatory responses in liver fibrosis

Chronic liver diseases such as nonalcoholic fatty liver disease (NAFLD) or viral hepatitis are characterized by persistent inflammation and subsequent liver fibrosis. Liver fibrosis critically determines long-term morbidity (for example, cirrhosis or liver cancer) and mortality in NAFLD and nonalcoholic steatohepatitis (NASH). Inflammation represents the concerted response of various hepatic cell types to hepatocellular death and inflammatory signals, which are related to intrahepatic injury pathways or extrahepatic mediators from the gut-liver axis and the circulation. Single-cell technologies have revealed the heterogeneity of immune cell activation concerning disease states and the spatial organization within the liver, including resident and recruited macrophages, neutrophils as mediators of tissue repair, auto-aggressive features of T cells as well as various innate lymphoid cell and unconventional T cell populations. Inflammatory responses drive the activation of hepatic stellate cells (HSCs), and HSC subsets, in turn, modulate immune mechanisms via chemokines and cytokines or transdifferentiate into matrix-producing myofibroblasts. Current advances in understanding the pathogenesis of inflammation and fibrosis in the liver, mainly focused on NAFLD or NASH owing to the high unmet medical need, have led to the identification of several therapeutic targets. In this Review, we summarize the inflammatory mediators and cells in the diseased liver, fibrogenic pathways and their therapeutic implications.

Ontogeny, functions and reprogramming of Kupffer cells upon infectious disease

The liver is a vital metabolic organ that also performs important immune-regulatory functions. In the context of infections, the liver represents a target site for various pathogens, while also having an outstanding capacity to filter the blood from pathogens and to contain infections. Pathogen scavenging by the liver is primarily performed by its large and heterogeneous macrophage population. The major liver-resident macrophage population is located within the hepatic microcirculation and is known as Kupffer cells (KCs). Although other minor macrophages reside in the liver as well, KCs remain the best characterized and are the best well-known hepatic macrophage population to be functionally involved in the clearance of infections. The response of KCs to pathogenic insults often governs the overall severity and outcome of infections on the host. Moreover, infections also impart long-lasting, and rarely studied changes to the KC pool. In this review, we discuss current knowledge on the biology and the various roles of liver macrophages during infections. In addition, we reflect on the potential of infection history to imprint long-lasting effects on macrophages, in particular liver macrophages.

Immunology of hepatitis D virus infection: General concepts and present evidence

Infection with the hepatitis D virus induces the most severe form of chronic viral hepatitis, affecting over 12 million people worldwide. Chronic HDV infection leads to rapid development of liver cirrhosis and hepatocellular carcinoma in ~70% of patients within 15 years of infection. Recent evidence suggests that an interplay of different components of the immune system are contributing to viral control and may even be implicated in liver disease pathogenesis. This review will describe general concepts of antiviral immune response and elicit the present evidence concerning the interplay of the hepatitis D virus with the immune system.

Memory CD8+ T cell-mediated protection against liver-stage malaria

Nearly half of the world's population is at risk of malaria, a disease caused by the protozoan parasite Plasmodium, which is estimated to cause more than 240,000,000 infections and kill more than 600,000 people annually. The emergence of Plasmodia resistant to chemoprophylactic treatment highlights the urgency to develop more effective vaccines. In this regard, whole sporozoite vaccination approaches in murine models and human challenge studies have provided substantial insight into the immune correlates of protection from malaria. From these studies, CD8+ T cells have come to the forefront, being identified as critical for vaccine-mediated liver-stage immunity that can prevent the establishment of the symptomatic blood stages and subsequent transmission of infection. However, the unique biological characteristics required for CD8+ T cell protection from liver-stage malaria dictate that more work must be done to design effective vaccines. In this review, we will highlight a subset of studies that reveal basic aspects of memory CD8+ T cell-mediated protection from liver-stage malaria infection.

Focus on T cell exhaustion: new advances in traditional Chinese medicine in infection and cancer

In chronic infections and cancers, T lymphocytes (T cells) are exposed to persistent antigen or inflammatory signals. The condition is often associated with a decline in T-cell function: a state called "exhaustion". T cell exhaustion is a state of T cell dysfunction characterized by increased expression of a series of inhibitory receptors (IRs), decreased effector function, and decreased cytokine secretion, accompanied by transcriptional and epigenetic changes and metabolic defects. The rise of immunotherapy, particularly the use of immune checkpoint inhibitors (ICIs), has dramatically changed the clinical treatment paradigm for patients. However, its low response rate, single target and high immunotoxicity limit its clinical application. The multiple immunomodulatory potential of traditional Chinese medicine (TCM) provides a new direction for improving the treatment of T cell exhaustion. Here, we review recent advances that have provided a clearer molecular understanding of T cell exhaustion, revealing the characteristics and causes of T cell exhaustion in persistent infections and cancers. In addition, this paper summarizes recent advances in improving T cell exhaustion in infectious diseases and cancer with the aim of providing a comprehensive and valuable source of information on TCM as an experimental study and their role in collaboration with ICIs therapy.

Immune response and treatment targets of chronic hepatitis B virus infection: innate and adaptive immunity

Chronic hepatitis B virus (HBV) infection is a major global public health risk that threatens human life and health, although the number of vaccinated people has increased. The clinical outcome of HBV infection depends on the complex interplay between viral replication and the host immune response. Innate immunity plays an important role in the early stages of the disease but retains no long-term immune memory. However, HBV evades detection by the host innate immune system through stealth. Therefore, adaptive immunity involving T and B cells is crucial for controlling and clearing HBV infections that lead to liver inflammation and damage. The persistence of HBV leads to immune tolerance owing to immune cell dysfunction, T cell exhaustion, and an increase in suppressor cells and cytokines. Although significant progress has been made in HBV treatment in recent years, the balance between immune tolerance, immune activation, inflammation, and fibrosis in chronic hepatitis B remains unknown, making a functional cure difficult to achieve. Therefore, this review focuses on the important cells involved in the innate and adaptive immunity of chronic hepatitis B that target the host immune system and identifies treatment strategies.

Current and novel modalities for management of chronic hepatitis B infection

Over 296 million people are estimated to have chronic hepatitis B viral infection (CHB), and it poses unique challenges for elimination. CHB is the result of hepatitis B virus (HBV)-specific immune tolerance and the presence of covalently closed circular DNA as mini chromosome inside the nucleus and the integrated HBV. Serum hepatitis B core-related antigen is the best surrogate marker for intrahepatic covalently closed circular DNA. Functional HBV “cure” is the durable loss of hepatitis B surface antigen (HBsAg), with or without HBsAg seroconversion and undetectable serum HBV DNA after completing a course of treatment. The currently approved therapies are nucleos(t)ide analogues, interferon-alpha, and pegylated-interferon. With these therapies, functional cure can be achieved in < 10% of CHB patients. Any variation to HBV or the host immune system that disrupts the interaction between them can lead to reactivation of HBV. Novel therapies may allow efficient control of CHB. They include direct acting antivirals and immunomodulators. Reduction of the viral antigen load is a crucial factor for success of immune-based therapies. Immunomodulatory therapy may lead to modulation of the host immune system. It may enhance/restore innate immunity against HBV (as toll-like-receptors and cytosolic retinoic acid inducible gene I agonist). Others may induce adaptive immunity as checkpoint inhibitors, therapeutic HBV vaccines including protein (HBsAg/preS and hepatitis B core antigen), monoclonal or bispecific antibodies and genetically engineered T cells to generate chimeric antigen receptor-T or T-cell receptor-T cells and HBV-specific T cells to restore T cell function to efficiently clear HBV. Combined therapy may successfully overcome immune tolerance and lead to HBV control and cure. Immunotherapeutic approaches carry the risk of overshooting immune responses causing uncontrolled liver damage. The safety of any new curative therapies should be measured in relation to the excellent safety of currently approved nucleos(t)ide analogues. Development of novel antiviral and immune modulatory therapies should be associated with new diagnostic assays used to evaluate the effectiveness or to predict response.

A computational method for cell type-specific expression quantitative trait loci mapping using bulk RNA-seq data

Mapping cell type-specific gene expression quantitative trait loci (ct-eQTLs) is a powerful way to investigate the genetic basis of complex traits. A popular method for ct-eQTL mapping is to assess the interaction between the genotype of a genetic locus and the abundance of a specific cell type using a linear model. However, this approach requires transforming RNA-seq count data, which distorts the relation between gene expression and cell type proportions and results in reduced power and/or inflated type I error. To address this issue, we have developed a statistical method called CSeQTL that allows for ct-eQTL mapping using bulk RNA-seq count data while taking advantage of allele-specific expression. We validated the results of CSeQTL through simulations and real data analysis, comparing CSeQTL results to those obtained from purified bulk RNA-seq data or single cell RNA-seq data. Using our ct-eQTL findings, we were able to identify cell types relevant to 21 categories of human traits.

Nirmatrelvir treatment of SARS-CoV-2-infected mice blunts antiviral adaptive immune responses

Alongside vaccines, antiviral drugs are becoming an integral part of our response to the SARS-CoV-2 pandemic. Nirmatrelvir-an orally available inhibitor of the 3-chymotrypsin-like cysteine protease-has been shown to reduce the risk of progression to severe COVID-19. However, the impact of nirmatrelvir treatment on the development of SARS-CoV-2-specific adaptive immune responses is unknown. Here, by using mouse models of SARS-CoV-2 infection, we show that nirmatrelvir administration blunts the development of SARS-CoV-2-specific antibody and T cell responses. Accordingly, upon secondary challenge, nirmatrelvir-treated mice recruited significantly fewer memory T and B cells to the infected lungs and mediastinal lymph nodes, respectively. Together, the data highlight a potential negative impact of nirmatrelvir treatment with important implications for clinical management and might help explain the virological and/or symptomatic relapse after treatment completion reported in some individuals.

Forthcoming Developments in Models to Study the Hepatitis B Virus Replication Cycle, Pathogenesis, and Pharmacological Advancements

Hepatitis, liver cirrhosis, and hepatocellular carcinoma are all manifestations of chronic hepatitis B. Its pathogenesis and molecular mechanism remain mysterious. As medical science progresses, different models are being used to study the disease from the physiological and molecular levels. Animal models have played an unprecedented role in achieving in-depth knowledge of the disease while posing no risk of harming humans throughout the study. The scarcity of acceptable animal models has slowed progress in hepatitis B virus (HBV) research and preclinical testing of antiviral medicines since HBV has a narrow species tropism and exclusively infects humans and higher primates. The development of human chimeric mice was supported by a better understanding of the obstacles to interspecies transmission, which has substantially opened the way for HBV research in vivo and the evaluation of possible chronic hepatitis B therapeutics. Animal models are cumbersome to handle, not accessible, and expensive. Hence, it is herculean to investigate the HBV replication cycle in animal models. Therefore, it becomes essential to build a splendid in vitro cell culture system to demonstrate the mechanisms attained by the HBV for its multiplication and sustenance. We also addressed the advantages and caveats associated with different models in examining HBV.

HBV Infection and Host Interactions: The Role in Viral Persistence and Oncogenesis

Hepatitis B virus (HBV) is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Despite the advent of vaccines and potent antiviral agents able to suppress viral replication, recovery from chronic HBV infection is still an extremely difficult goal to achieve. Complex interactions between virus and host are responsible for HBV persistence and the risk of oncogenesis. Through multiple pathways, HBV is able to silence both innate and adaptive immunological responses and become out of control. Furthermore, the integration of the viral genome into that of the host and the production of covalently closed circular DNA (cccDNA) represent reservoirs of viral persistence and account for the difficult eradication of the infection. An adequate knowledge of the virus-host interaction mechanisms responsible for viral persistence and the risk of hepatocarcinogenesis is necessary for the development of functional cures for chronic HBV infection. The purpose of this review is, therefore, to analyze how interactions between HBV and host concur in the mechanisms of infection, persistence, and oncogenesis and what are the implications and the therapeutic perspectives that follow.

Studying T Cell Responses to Hepatotropic Viruses in the Liver Microenvironment

T cells play an important role in the clearance of hepatotropic viruses but may also cause liver injury and contribute to disease progression in chronic hepatitis B and C virus infections which affect millions of people worldwide. The liver provides a unique microenvironment of immunological tolerance and hepatic immune regulation can modulate the functional properties of T cell subsets and influence the outcome of a virus infection. Extensive research over the last years has advanced our understanding of hepatic conventional CD4+ and CD8+ T cells and unconventional T cell subsets and their functions in the liver environment during acute and chronic viral infections. The recent development of new small animal models and technological advances should further increase our knowledge of hepatic immunological mechanisms. Here we provide an overview of the existing models to study hepatic T cells and review the current knowledge about the distinct roles of heterogeneous T cell populations during acute and chronic viral hepatitis.

Tissue CD14+CD8+ T cells reprogrammed by myeloid cells and modulated by LPS

The liver is bathed in bacterial products, including lipopolysaccharide transported from the intestinal portal vasculature, but maintains a state of tolerance that is exploited by persistent pathogens and tumours1-4. The cellular basis mediating this tolerance, yet allowing a switch to immunity or immunopathology, needs to be better understood for successful immunotherapy of liver diseases. Here we show that a variable proportion of CD8+ T cells compartmentalized in the human liver co-stain for CD14 and other prototypic myeloid membrane proteins and are enriched in close proximity to CD14high myeloid cells in hepatic zone 2. CD14+CD8+ T cells preferentially accumulate within the donor pool in liver allografts, among hepatic virus-specific and tumour-infiltrating responses, and in cirrhotic ascites. CD14+CD8+ T cells exhibit increased turnover, activation and constitutive immunomodulatory features with high homeostatic IL-10 and IL-2 production ex vivo, and enhanced antiviral/anti-tumour effector function after TCR engagement. This CD14+CD8+ T cell profile can be recapitulated by the acquisition of membrane proteins-including the lipopolysaccharide receptor complex-from mononuclear phagocytes, resulting in augmented tumour killing by TCR-redirected T cells in vitro. CD14+CD8+ T cells express integrins and chemokine receptors that favour interactions with the local stroma, which can promote their induction through CXCL12. Lipopolysaccharide can also increase the frequency of CD14+CD8+ T cells in vitro and in vivo, and skew their function towards the production of chemotactic and regenerative cytokines. Thus, bacterial products in the gut-liver axis and tissue stromal factors can tune liver immunity by driving myeloid instruction of CD8+ T cells with immunomodulatory ability.

Next-generation pathology detection of T cell-antigen-presenting cell immune synapses in human liver allografts

BACKGROUND AND AIMS

In otherwise near-normal appearing biopsies by routine light microscopy, next-generation pathology (NGP) detected close pairings (immune pairs; iPAIRs) between lymphocytes and antigen-presenting cells (APCs) that predicted immunosuppression weaning failure in pediatric liver transplant (LTx) recipients (Immunosuppression Withdrawal for Stable Pediatric Liver Transplant Recipients [iWITH], NCT01638559). We hypothesized that NGP-detected iPAIRs enrich for true immune synapses, as determined by nuclear shape metrics, intercellular distances, and supramolecular activation complex (SMAC) formation.

APPROACH AND RESULTS

Intralobular iPAIRs (CD45 high lymphocyte-major histocompatibility complex II + APC pairs; n = 1167, training set) were identified at low resolution from multiplex immunohistochemistry-stained liver biopsy slides from several multicenter LTx immunosuppression titration clinical trials (iWITH; NCT02474199 (Donor Alloantigen Reactive Tregs (darTregs) for Calcineurin Inhibitor (CNI) Reduction (ARTEMIS); Prospective Longitudinal Study of iWITH Screen Failures Secondary to Histopathology). After excluding complex multicellular aggregates, high-resolution imaging was used to examine immune synapse formation ( n = 998). By enriching for close intranuclear lymphocyte-APC distance (mean: 0.713 μm) and lymphocyte nuclear flattening (mean ferret diameter: 2.1), SMAC formation was detected in 29% of iPAIR-engaged versus 9.5% of unpaired lymphocytes. Integration of these morphometrics enhanced NGP detection of immune synapses (ai-iSYN). Using iWITH preweaning biopsies from eligible patients ( n = 53; 18 tolerant, 35 nontolerant; testing set), ai-iSYN accurately predicted (87.3% accuracy vs. 81.4% for iPAIRs; 100% sensitivity, 75% specificity) immunosuppression weaning failure. This confirmed the presence and importance of intralobular immune synapse formation in liver allografts. Stratification of biopsy mRNA expression data by immune synapse quantity yielded the top 20 genes involved in T cell activation and immune synapse formation and stability.

CONCLUSIONS

NGP-detected immune synapses (subpathological rejection) in LTx patients prior to immunosuppression reduction suggests that NGP-detected (allo)immune activity usefulness for titration of immunosuppressive therapy in various settings.

Serum cytokine change profile associated with HBsAg loss during combination therapy with PEG-IFN-α in NAs-suppressed chronic hepatitis B patients

Objective

The aim of this study was to explore the profile of cytokine changes during the combination therapy with pegylated interferon alpha (PEG-IFN-α) and its relationship with HBsAg loss in nucleos(t)ide analogs (NAs)-suppressed chronic hepatitis B patients.

Methods

Seventy-six patients with chronic hepatitis B with HBsAg less than 1,500 IU/ml and HBV DNA negative after receiving ≥ 1-year NAs therapy were enrolled. Eighteen patients continued to take NAs monotherapy (the NAs group), and 58 patients received combination therapy with NAs and PEG-IFN-α (the Add-on group). The levels of IFNG, IL1B, IL1RN, IL2, IL4, IL6, IL10, IL12A, IL17A, CCL2, CCL3, CCL5, CXCL8, CXCL10, TNF, and CSF2 in peripheral blood during treatment were detected.

Results

At week 48, 0.00% (0/18) in the NAs group and 25.86% (15/58) in the Add-on group achieved HBsAg loss. During 48 weeks of combined treatment, there was a transitory increase in the levels of ALT, IL1RN, IL2, and CCL2. Compared to the NAs group, CXCL8 and CXCL10 in the Add-on group remain higher after rising, yet CCL3 showed a continuously increasing trend. Mild and early increases in IL1B, CCL3, IL17A, IL2, IL4, IL6, and CXCL8 were associated with HBsAg loss or decrease >1 log, while sustained high levels of CCL5 and CXCL10 were associated with poor responses to Add-on therapy at week 48.

Conclusions

The serum cytokine change profile is closely related to the response to the combination therapy with PEG-IFN-α and NAs, and may help to reveal the mechanism of functional cure and discover new immunological predictors and new therapeutic targets.

The scientific basis of combination therapy for chronic hepatitis B functional cure

Functional cure of chronic hepatitis B (CHB) - or hepatitis B surface antigen (HBsAg) loss after 24 weeks off therapy - is now the goal of treatment, but is rarely achieved with current therapy. Understanding the hepatitis B virus (HBV) life cycle and immunological defects that lead to persistence can identify targets for novel therapy. Broadly, treatments fall into three categories: those that reduce viral replication, those that reduce antigen load and immunotherapies. Profound viral suppression alone does not achieve quantitative (q)HBsAg reduction or HBsAg loss. Combining nucleos(t)ide analogues and immunotherapy reduces qHBsAg levels and induces HBsAg loss in some patients, particularly those with low baseline qHBsAg levels. Even agents that are specifically designed to reduce viral antigen load might not be able to achieve sustained HBsAg loss when used alone. Thus, rationale exists for the use of combinations of all three therapy types. Monitoring during therapy is important not just to predict HBsAg loss but also to understand mechanisms of HBsAg loss using viral and immunological biomarkers, and in selected cases intrahepatic sampling. We consider various paths to functional cure of CHB and the need to individualize treatment of this heterogeneous infection until a therapeutic avenue for all patients with CHB is available.

Hepatitis B virus infection: An insight into the clinical connection and molecular interaction between hepatitis B virus and host extrahepatic cancer risk

The evidence for chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) occurrence is well established. The hepatocyte epithelium carcinogenesis caused by HBV has been investigated and reviewed in depth. Nevertheless, recent findings from preclinical and observational studies suggested that chronic HBV infection is equally important in extrahepatic cancer occurrence and survival, specifically gastrointestinal system-derived cancers. Immune microenvironment changes (immune-suppressive cytokine infiltration), epigenetic modification (N6-methyladenosine), molecular signaling pathways (PI3K-Akt and Wnt), and serum biomarkers such as hepatitis B virus X (HBx) protein are potential underlying mechanisms in chronic HBV infection-induced extrahepatic cancers. This narrative review aimed to comprehensively summarize the most recent advances in evaluating the association between chronic HBV infection and extrahepatic cancer risk and explore the potential underlying molecular mechanisms in the carcinogenesis induction of extrahepatic cancers in chronic HBV conditions.

Abnormally primed CD8 T cells: The Achilles' heel of CHB

Chronic hepatitis B virus (HBV) infection continues to be a significant public health challenge, and more than 250 million people around world are infected with HBV. The clearance of HBV with virus-specific CD8 T cells is critical for a functional cure. However, naïve HBV-specific CD8 T cells are heavily hindered during the priming process, and this phenomenon is closely related to abnormal cell and signal interactions in the complex immune microenvironment. Here, we briefly summarize the recent progress in understanding the abnormal priming of HBV-specific CD8 T cells and some corresponding immunotherapies to facilitate their functional recovery, which provides a novel perspective for the design and development of immunotherapy for chronic HBV infection (CHB). Finally, we also highlight the balance between viral clearance and pathological liver injury induced by CD8 T-cell activation that should be carefully considered during drug development.

Low dose interleukin-2 selectively expands circulating regulatory T cells but fails to promote liver allograft tolerance in humans

BACKGROUND & AIMS

CD4+CD25+Foxp3+ regulatory T cells (Tregs) are essential to maintain immunological tolerance and have been shown to promote liver allograft tolerance in both rodents and humans. Low-dose IL-2 (LDIL-2) can expand human endogenous circulating Tregs in vivo, but its role in suppressing antigen-specific responses and promoting Treg trafficking to the sites of inflammation is unknown. Likewise, whether LDIL-2 facilitates the induction of allograft tolerance has not been investigated in humans.

METHODS

We conducted a clinical trial in stable liver transplant recipients 2-6 years post-transplant to determine the capacity of LDIL-2 to suppress allospecific immune responses and allow for the complete discontinuation of maintenance immunosuppression (ClinicalTrials.gov NCT02949492). One month after LDIL-2 was initiated, those exhibiting at least a 2-fold increase in circulating Tregs gradually discontinued immunosuppression over a 4-month period while continuing LDIL-2 for a total treatment duration of 6 months.

RESULTS

All participants achieved a marked and sustained increase in circulating Tregs. However, this was not associated with the preferential expansion of donor-reactive Tregs and did not promote the accumulation of intrahepatic Tregs. Furthermore, LDIL-2 induced a marked IFNγ-orchestrated transcriptional response in the liver even before immunosuppression weaning was initiated. The trial was terminated after the first 6 participants failed to reach the primary endpoint owing to rejection requiring reinstitution of immunosuppression.

CONCLUSIONS

The expansion of circulating Tregs in response to LDIL-2 is not sufficient to control alloimmunity and to promote liver allograft tolerance, due, at least in part, to off-target effects that increase liver immunogenicity. Our trial provides unique insight into the mechanisms of action of immunomodulatory therapies such as LDIL-2 and their limitations in promoting alloantigen-specific effects and immunological tolerance.

CLINICAL TRIALS REGISTRATION

The study is registered at ClinicalTrials.gov (NCT02949492).

IMPACT AND IMPLICATIONS

The administration of low-dose IL-2 is an effective way of increasing the number of circulating regulatory T cells (Tregs), an immunosuppressive lymphocyte subset that is key for the establishment of immunological tolerance, but its use to promote allograft tolerance in the setting of clinical liver transplantation had not been explored before. In liver transplant recipients on tacrolimus monotherapy, low-dose IL-2 effectively expanded circulating Tregs but did not increase the number of Tregs with donor specificity, nor did it promote their trafficking to the transplanted liver. Low-dose IL-2 did not facilitate the discontinuation of tacrolimus and elicited, as an off-target effect, an IFNγ-orchestrated inflammatory response in the liver that resembled T cell-mediated rejection. These results, supporting an unexpected role for IL-2 in regulating the immunogenicity of the liver, highlight the need to carefully evaluate systemic immunoregulatory strategies with investigations that are not restricted to the blood compartment and involve target tissues such as the liver.

The Tumor Microenvironment of Hepatocellular Carcinoma: Untying an Intricate Immunological Network

HCC, the most prevalent form of primary liver cancer, is prototypically an inflammation-driven cancer developing after years of inflammatory insults. Consequently, the hepatic microenvironment is a site of complex immunological activities. Moreover, the tolerogenic nature of the liver can act as a barrier to anti-tumor immunity, fostering cancer progression and resistance to immunotherapies based on immune checkpoint inhibitors (ICB). In addition to being a site of primary carcinogenesis, many cancer types have high tropism for the liver, and patients diagnosed with liver metastasis have a dismal prognosis. Therefore, understanding the immunological networks characterizing the tumor microenvironment (TME) of HCC will deepen our understanding of liver immunity, and it will underpin the dominant mechanisms controlling both spontaneous and therapy-induced anti-tumor immune responses. Herein, we discuss the contributions of the cellular and molecular components of the liver immune contexture during HCC onset and progression by underscoring how the balance between antagonistic immune responses can recast the properties of the TME and the response to ICB.

Selective decrease of donor-reactive Tregs after liver transplantation limits Treg therapy for promoting allograft tolerance in humans

Promoting immune tolerance to transplanted organs can minimize the amount of immunosuppressive drugs that patients need to take, reducing lifetime risks of mortality and morbidity. Regulatory T cells (Tregs) are essential for immune tolerance, and preclinical studies have shown their therapeutic efficacy in inducing transplantation tolerance. Here, we report the results of a phase 1/2 trial (ARTEMIS, NCT02474199) of autologous donor alloantigen-reactive Treg (darTreg) therapy in individuals 2 to 6 years after receiving a living donor liver transplant. The primary efficacy endpoint was calcineurin inhibitor dose reduction by 75% with stable liver function tests for at least 12 weeks. Among 10 individuals who initiated immunosuppression withdrawal, 1 experienced rejection before planned darTreg infusion, 5 received darTregs, and 4 were not infused because of failure to manufacture the minimal infusible dose of 100 × 106 cells. darTreg infusion was not associated with adverse events. Two darTreg-infused participants reached the primary endpoint, but an insufficient number of recipients were treated for assessing the efficacy of darTregs. Mechanistic studies revealed generalized Treg activation, senescence, and selective reduction of donor reactivity after liver transplantation. Overall, the ARTEMIS trial features a design concept for evaluating the efficacy of Treg therapy in transplantation. The mechanistic insight gained from the study may help guide the design of future trials.

Liver-resident memory T cells: life in lockdown

A subset of memory T cells has been identified in the liver with a tissue-resident profile and the capacity for long-term 'lockdown'. Here we review how they are retained in, and adapted to, the hepatic microenvironment, including its unique anatomical features and metabolic challenges. We describe potential interactions with other local cell types and the need for a better understanding of this complex bidirectional crosstalk. Pathogen or tumour antigen-specific tissue-resident memory T cells (T_RM) can provide rapid frontline immune surveillance; we review the evidence for this in hepatotropic infections of major worldwide importance like hepatitis B and malaria and in liver cancers like hepatocellular carcinoma. Conversely, T_RM can be triggered by pro-inflammatory and metabolic signals to mediate bystander tissue damage, with an emerging role in a number of liver pathologies. We discuss the need for liver sampling to gain a window into these compartmentalised T cells, allowing more accurate disease monitoring and future locally targeted immunotherapies.

Advances in Immunotherapy for Hepatitis B

Hepatitis B virus (HBV) is a hepatotropic virus with the potential to cause chronic infection, and it is one of the common causes of liver disease worldwide. Chronic HBV infection leads to liver cirrhosis and, ultimately, hepatocellular carcinoma (HCC). The persistence of covalently closed circular DNA (cccDNA) and the impaired immune response in patients with chronic hepatitis B (CHB) has been studied over the past few decades. Despite advances in the etiology of HBV and the development of potent virus-suppressing regimens, a cure for HBV has not been found. Both the innate and adaptive branches of immunity contribute to viral eradication. However, immune exhaustion and evasion have been demonstrated during CHB infection, although our understanding of the mechanism is still evolving. Recently, the successful use of an antiviral drug for hepatitis C has greatly encouraged the search for a cure for hepatitis B, which likely requires an approach focused on improving the antiviral immune response. In this review, we discuss our current knowledge of the immunopathogenic mechanisms and immunobiology of HBV infection. In addition, we touch upon why the existing therapeutic approaches may not achieve the goal of a functional cure. We also propose how combinations of new drugs, and especially novel immunotherapies, contribute to HBV clearance.

HBV immune tolerance of HBs-transgenic mice observed through parabiosis with WT mice

It was extensively recognized that central tolerance to HBV exists in HBs-transgenic (Tg) mice, however, the immune response to HBV vaccine may be inspired in adult HBs-Tg mice after boosting with potent adjuvants, leaving a mystery to explore its immune tolerance. Here, WT-HBs-Tg parabiotic mice model was generated by conjoining WT (donor) and HBs-Tg (host) mouse via parabiotic surgery, in order to see how immunocompetent WT mice naturally respond to HBV, and how tolerant HBs-Tg mice influence the anti-HBV immunity from WT mice. It was found that WT CD8+ T cells markedly accumulated into the liver of HBs-Tg parabionts, and importantly, almost all HBsAg-specific CD8+ T cells derived from WT but not HBs-Tg mice, making a clear separation of a normal immune response from WT donor and a tolerant response by recipient host. Further, in the absence of host but not donor spleen, HBsAg-specific CD8+ T cells disappeared, indicating that host spleen was the indispensable site for donor HBsAg-specific CD8+ T cell priming though its mechanisms need further study. We found that donor CD4+ T helper cells were necessary for donor HBsAg-specific CD8+ T cell response by CD4-deficiency in WT or in HBs-Tg mice, indicating that an immune response was elicited between CD4+ T helper cells and CD8+ cytotoxic T cells of donor in the host but not donor spleen. It was noted that compared to donor CD4+ T cells, host CD4+ T cells were characterized with more tolerant features by harboring more CD25+Foxp3+ Tregs with higher expression of PD-1 and TIGIT in the spleen of HBs-Tg parabionts, which exhibited suppressive function on CD8+ T cells directly. Moreover, the Th1/Treg ratio was enhanced after parabiosis, suggesting that donor T helper cells may overcome the negative regulation of host Tregs in host spleen. In conclusion, both incompetent anti-HBV CD8+ T cells and insufficient help from CD4+ T cells are the major mechanisms underlying immune tolerance in HBs-Tg mice which helps explain HBV persistence.