Functional Exhaustion of HBV-Specific CD8 T Cells Impedes PD-L1 Blockade Efficacy in Chronic HBV Infection

HBV DNA polymerase upregulates the transcription of PD-L1 and suppresses T cell activity in hepatocellular carcinoma

BACKGROUND

In HBV-associated HCC, T cells often exhibit a state of functional exhaustion, which prevents the immune response from rejecting the tumor and allows HCC to progress. Moreover, polymerase-specific T cells exhibit more severe T-cell exhaustion compared to core-specific T cells. However, whether HBV DNA polymerase drives HBV-specific CD8+ T cell exhaustion in HBV-related HCC remains unclear.

METHODS

We constructed a Huh7 cell line stably expressing HA-HBV-DNA-Pol and applied co-culture systems to clarify its effect on immune cell function. We also examined how HBV-DNA-Pol modulated PD-L1 expression in HCC cells. In addition, HBV-DNA-Pol transgenic mice were used to elucidate the underlying mechanism of HBV-DNA-Pol/PD-L1 axis-induced T cell exhaustion.

RESULTS

Biochemical analysis showed that Huh7 cells overexpressing HBV-DNA-Pol inhibited the proliferation, activation, and cytokine secretion of Jurkat cells and that this effect was dependent on their direct contact. A similar inhibitory effect was observed in an HCC mouse model. PD-L1 was brought to our attention during screening. Our results showed that the overexpression of HBV-DNA-Pol upregulated PD-L1 mRNA and protein expression. PD-L1 antibody blockade reversed the inhibitory effect of Huh7 cells overexpressing HBV-DNA-Pol on Jurkat cells. Mechanistically, HBV-DNA-Pol interacts with PARP1, thereby inhibiting the nuclear translocation of PARP1 and further upregulating PD-L1 expression.

CONCLUSIONS

Our findings suggest that HBV-DNA-Pol can act as a regulator of PD-L1 in HCC, thereby directing anti-cancer immune evasion, which further provides a new idea for the clinical treatment of liver cancer.

A Systematic Review of the Advances in the Study of T Lymphocyte Suppressor Receptors in HBV Infection: Potential Therapeutic Targets

Background: HBV-specific T lymphocytes are pivotal in eliminating the hepatitis B virus (HBV) and regulating intrahepatic inflammatory reactions. Effective T cell responses curtail HBV infection; however, compromised immunity can result in persistent infection. Beyond the acute phase, the continued presence of antigens and inflammation leads to the increased expression of various inhibitory receptors, such as PD-1, CTLA-4, Tim-3, LAG3, 2B4, CD160, BTLA, and TIGIT. This escalates the dysfunction of and diminishes the immune and proliferative abilities of T cells. Methods: In this study, we reviewed English-language literature from PubMed, Web of Science, and Scopus up to 9 July 2023. This paper aims to elucidate the inhibitory effects of these receptors on HBV-specific T lymphocytes and how immune function can be rejuvenated by obstructing the inhibitory receptor signaling pathway in chronic HBV patients. We also summarize the latest insights into related anti-HBV immunotherapy. Result: From 66 reviewed reports, we deduced that immunotherapy targeting inhibitory receptors on T cells is a reliable method to rejuvenate T cell immune responses in chronic HBV patients. However, comprehensive combination therapy strategies are essential for a functional cure. Conclusions: Targeting T cell suppressor receptors and combining immunotherapy with antiviral treatments may offer a promising approach towards achieving a functional cure, urging future research to prioritize effective combination therapeutic strategies for chronic HBV infection.

IL-2 produced by HBV-specific T cells as a biomarker of viral control and predictor of response to PD-1 therapy across clinical phases of chronic hepatitis B

BACKGROUND

There are no immunological biomarkers that predict control of chronic hepatitis B (CHB). The lack of immune biomarkers raises concerns for therapies targeting PD-1/PD-L1 because they have the potential for immune-related adverse events. Defining specific immune functions associated with control of HBV replication could identify patients likely to respond to anti-PD-1/PD-L1 therapies and achieve a durable functional cure.

METHODS

We enrolled immunotolerant, HBeAg+ immune-active (IA+), HBeAg- immune-active (IA-), inactive carriers, and functionally cured patients to test ex vivo PD-1 blockade on HBV-specific T cell functionality. Peripheral blood mononuclear cells were stimulated with overlapping peptides covering HBV proteins +/-α-PD-1 blockade. Functional T cells were measured using a 2-color FluoroSpot assay for interferon-γ and IL-2. Ex vivo functional restoration was compared to the interferon response capacity assay, which predicts overall survival in cancer patients receiving checkpoint inhibitors.

RESULTS

Ex vivo interferon-γ+ responses did not differ across clinical phases. IL-2+ responses were significantly higher in patients with better viral control and preferentially restored with PD-1 blockade. Inactive carrier patients displayed the greatest increase in IL-2 production, which was dominated by CD4 T cell and response to the HBcAg. The interferon response capacity assay significantly correlated with the degree of HBV-specific T cell restoration.

CONCLUSIONS

IL-2 production was associated with better HBV control and superior to interferon-γ as a marker of T cell restoration following ex vivo PD-1 blockade. Our study suggests that responsiveness to ex vivo PD-1 blockade, or the interferon response capacity assay, may support stratification for α-PD-1 therapies.

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.

Metabolic interventions improve HBV envelope-specific T-cell responses in patients with chronic hepatitis B

BACKGROUND

Restoration of HBV-specific T cell immunity is a promising approach for the functional cure of chronic Hepatitis B (CHB), necessitating the development of valid assays to boost and monitor HBV-specific T cell responses in patients with CHB.

METHODS

We analyzed hepatitis B virus (HBV) core- and envelope (env)-specific T cell responses using in vitro expanded peripheral blood mononuclear cells (PBMCs) from patients with CHB exhibiting different immunological phases, including immune tolerance (IT), immune activation (IA), inactive carrier (IC), and HBeAg-negative hepatitis (ENEG). Additionally, we evaluated the effects of metabolic interventions, including mitochondria-targeted antioxidants (MTA), polyphenolic compounds, and ACAT inhibitors (iACAT), on HBV-specific T-cell functionality.

RESULTS

We found that HBV core- and env-specific T cell responses were finely coordinated and more profound in IC and ENEG than in the IT and IA stages. HBV env-specific T cells were more dysfunctional but prone to respond to metabolic interventions using MTA, iACAT, and polyphenolic compounds than HBV core-specific T-cells. The responsiveness of HBV env-specific T cells to metabolic interventions can be predicted by the eosinophil (EO) count and the coefficient of variation of red blood cell distribution width (RDW-CV).

CONCLUSION

These findings may provide valuable information for metabolically invigorating HBV-specific T-cells to treat CHB.

Role of CXCR5+ CD8+ T cells in human hepatitis B virus infection

The replication of HBV in hepatocytes can be effectively inhibited by lifelong antiviral therapy. Because of the long-term presence of HBV reservoirs, the virus rebound frequently occurs once the treatment is stopped, which poses a considerable obstacle to the complete removal of the virus. In terms of gene composition, regulation of B cell action and function, CXCR5+ CD8+ T cells are similar to CXCR5+ CD4+ T follicular helper cells, while these cells are characterized by elevated programmed cell death 1 and cytotoxic-related proteins. CXCR5+ CD8+ T cells are strongly associated with progression in inflammatory and autoimmune diseases. In addition, CXCR5 expression on the surface of CD8+ T cells is mostly an indicator of memory stem cell-like failure in progenitor cells in cancer that are more responsive to immune checkpoint blocking therapy. Furthermore, the phenomena have also been demonstrated in some viral infections, highlighting the duality of the cellular immune response of CXCR5+ CD8+ T cells. This mini-review will focus on the function of CXCR5+ CD8+ T cells in HBV infection and discuss the function of these CD8+ T cells and the potential of associated co-stimulators or cytokines in HBV therapeutic strategies.

A role for immune modulation in achieving functional cure for chronic hepatitis B among current changes in the landscape of new treatments

INTRODUCTION

Chronic hepatitis B (CHB) is rarely cured using available treatments. Barriers to cure are: 1) persistence of reservoirs of hepatitis B virus (HBV) replication and antigen production (HBV DNA); 2) high burden of viral antigens that promote T cell exhaustion with T cell dysfunction; 3) CHB-induced impairment of immune responses.

AREAS COVERED

We discuss options for new therapies that could address one or more of the barriers to functional cure, with particular emphasis on the potential role of immunotherapy.

EXPERT OPINION/COMMENTARY

Ideally, a sterilizing cure for CHB would translate into finite therapies that result in loss of HBV surface antigen and eradication of HBV DNA. Restoration of a functional adaptive immune response, a key facet of successful CHB treatment, remains elusive. Numerous strategies targeting the high viral DNA and antigen burden and aiming to restore the host immune responses will enter clinical development in coming years. Most patients are likely to require combinations of several drugs, personalized according to virologic and disease characteristics, patient preference, accessibility, and affordability. The management of CHB is a global health priority. Expedited drug development requires collaborations between regulatory agencies, scientists, clinicians, and within the industry to facilitate testing of the best drug combinations.

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.

CRISPR/Cas9 for hepatitis B virus infection treatment

Hepatitis B virus (HBV) infection remains a global health challenge. Despite the availability of effective preventive vaccines, millions of people are at risk of cirrhosis and hepatocellular carcinoma. Current drug therapies inhibit viral replication, slow the progression of liver fibrosis and reduce infectivity, but they rarely remove the covalently sealed circular DNA (cccDNA) of the virus that causes HBV persistence. Alternative treatment strategies, including those based on CRISPR/cas9 knockout virus gene, can effectively inhibit HBV replication, so it has a good prospect. During chronic infection, some virus gene knockouts based on CRISPR/cas9 may even lead to cccDNA inactivation. This paper reviews the progress of different HBV CRISPR/cas9, vectors for delivering to the liver, and the current situation of preclinical and clinical research.

LAG3+ erythroid progenitor cells inhibit HBsAg seroclearance during finite pegylated interferon treatment through LAG3 and TGF-β

HBsAg seroclearance, the ideal aim of anti-hepatitis B virus (HBV) treatment, cannot be achieved easily. Anemia is another common issue for chronic hepatitis B (CHB) patients, which leads to elevation of erythroid progenitor cells (EPCs) and immune suppression in cancer. This study investigated the role of EPCs in HBsAg seroclearance following PEGylated interferon-α (PEG-IFN) treatment. CD45⁺EPC accumulation in CHB patients and an AAV/HBV mice model was found in the circulation and liver by flow cytometry and immunofluorescence tests. Wright-Giemsa staining showed that these pathological CD45⁺EPCs presented elevated erythroid cells with relative immature morphologies and atypical cells compared with the control cells. CD45⁺EPCs were associated with immune tolerance and decreased HBsAg seroclearance during finite PEG-IFN treatment. CD45⁺EPCs suppressed antigen non-specific T cell activation and HBV-specific CD8⁺T cells, partially through transforming growth factor β (TGF-β). RNA-seq revealed that CD45⁺EPCs in patients with CHB presented a distinct gene expression profile compared with CD45^-EPCs and CD45⁺EPCs from cord blood. Notably, CD45⁺EPCs from patients with CHB expressed high level of Lymphocyte-activation gene 3 (LAG3), an immune checkpoint molecule, and were then defined as LAG3⁺EPCs. LAG3⁺EPCs diminished the function of antigen presenting cells through LAG3, which was another mechanism by which LAG3⁺EPCs' suppressed HBV-specific CD8⁺T cells. Anti-LAG3 and anti-TGF-β combination treatment decreased serum HBeAg, HBV DNA levels and HBsAg level, as well as HBsAg-expression in hepatocytes during PEG-IFN treatment in the AAV/HBV mice model. Conclusions: LAG3⁺EPCs inhibited the efficacy of PEG-IFN treatment on HBsAg seroclearance induced by LAG3 and TGF-β. Anti-LAG3, anti-TGF-β and PEG-IFN combination treatment might facilitate HBV clearance.

Immune checkpoints on T and NK cells in the context of HBV infection: Landscape, pathophysiology and therapeutic exploitation

In hepatitis B virus (HBV) infection, the interplay between the virus and the host immune system is crucial in determining the pathogenesis of the disease. Patients who fail to mount a sufficient and sustained anti-viral immune response develop chronic hepatitis B (CHB). T cells and natural killer (NK) cells play decisive role in viral clearance, but they are defective in chronic HBV infection. The activation of immune cells is tightly controlled by a combination of activating and inhibitory receptors, called immune checkpoints (ICs), allowing the maintenance of immune homeostasis. Chronic exposure to viral antigens and the subsequent dysregulation of ICs actively contribute to the exhaustion of effector cells and viral persistence. The present review aims to summarize the function of various ICs and their expression in T lymphocytes and NK cells in the course of HBV infection as well as the use of immunotherapeutic strategies targeting ICs in chronic HBV infection.

Hepatitis B and Hepatitis D Viruses: A Comprehensive Update with an Immunological Focus

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) are highly prevalent viruses estimated to infect approximately 300 million people and 12-72 million people worldwide, respectively. HDV requires the HBV envelope to establish a successful infection. Concurrent infection with HBV and HDV can result in more severe disease outcomes than infection with HBV alone. These viruses can cause significant hepatic disease, including cirrhosis, fulminant hepatitis, and hepatocellular carcinoma, and represent a significant cause of global mortality. Therefore, a thorough understanding of these viruses and the immune response they generate is essential to enhance disease management. This review includes an overview of the HBV and HDV viruses, including life cycle, structure, natural course of infection, and histopathology. A discussion of the interplay between HDV RNA and HBV DNA during chronic infection is also included. It then discusses characteristics of the immune response with a focus on reactions to the antigenic hepatitis B surface antigen, including small, middle, and large surface antigens. This paper also reviews characteristics of the immune response to the hepatitis D antigen (including small and large antigens), the only protein expressed by hepatitis D. Lastly, we conclude with a discussion of recent therapeutic advances pertaining to these viruses.

Mesenchymal stem cells-based therapy in liver diseases

Multiple immune cells and their products in the liver together form a complex and unique immune microenvironment, and preclinical models have demonstrated the importance of imbalances in the hepatic immune microenvironment in liver inflammatory diseases and immunocompromised liver diseases. Various immunotherapies have been attempted to modulate the hepatic immune microenvironment for the purpose of treating liver diseases. Mesenchymal stem cells (MSCs) have a comprehensive and plastic immunomodulatory capacity. On the one hand, they have been tried for the treatment of inflammatory liver diseases because of their excellent immunosuppressive capacity; On the other hand, MSCs have immune-enhancing properties in immunocompromised settings and can be modified into cellular carriers for targeted transport of immune enhancers by genetic modification, physical and chemical loading, and thus they are also used in the treatment of immunocompromised liver diseases such as chronic viral infections and hepatocellular carcinoma. In this review, we discuss the immunological basis and recent strategies of MSCs for the treatment of the aforementioned liver diseases. Specifically, we update the immune microenvironment of the liver and summarize the distinct mechanisms of immune microenvironment imbalance in inflammatory diseases and immunocompromised liver diseases, and how MSCs can fully exploit their immunotherapeutic role in liver diseases with both immune imbalance patterns.

Hepatitis B functional cure and immune response

Hepatitis B virus (HBV) is a hepatotropic virus, which damage to hepatocytes is not direct, but through the immune system. HBV specific CD4⁺ T cells can induce HBV specific B cells and CD8⁺ T cells. HBV specific B cells produce antibodies to control HBV infection, while HBV specific CD8⁺ T cells destroy infected hepatocytes. One of the reasons for the chronicity of HBV infection is that it cannot effectively activate adoptive immunity and the function of virus specific immune cells is exhausted. Among them, virus antigens (including HBV surface antigen, e antigen, core antigen, etc.) can inhibit the function of immune cells and induce immune tolerance. Long term nucleos(t)ide analogues (NAs) treatment and inactive HBsAg carriers with low HBsAg level may "wake up" immune cells with abnormal function due to the decrease of viral antigen level in blood and liver, and the specific immune function of HBV will recover to a certain extent, thus becoming the "dominant population" for functional cure. In turn, the functional cure will further promote the recovery of HBV specific immune function, which is also the theoretical basis for complete cure of hepatitis B. In the future, the complete cure of chronic HBV infection must be the combination of three drugs: inhibiting virus replication, reducing surface antigen levels and specific immune regulation, among which specific immunotherapy is indispensable. Here we review the relationship, mechanism and clinical significance between the cure of hepatitis B and immune system.

Immune Checkpoint Molecules Expressed on CD4+ T Cell Subsets in Chronic Asymptomatic Hepatitis B Virus Carriers With Hepatitis B e Antigen-Negative

Background

Chronic hepatitis B virus (HBV) infection remains a major public health problem worldwide. Immune checkpoint molecules expressed on CD4⁺ T cells play critical roles in chronic HBV infection. However, their roles in chronic asymptomatic HBV carriers (ASCs) with hepatitis B e antigen (HBeAg)-negative remain unclear. In this study, we explored the role of immune checkpoint molecules expressed on CD4⁺ T cell subsets in chronic ASCs with HBeAg-negative.

Methods

Human peripheral blood mononuclear cells (PBMCs) from the ASCs with HBeAg-negative and healthy controls (HC) were isolated, and immune checkpoint molecules expressed on CD4⁺ T cell subsets and serum cytokines were detected by flow cytometry. Moreover, the mRNA expressions of immune checkpoint molecules were analyzed by a real-time quantitative PCR assay.

Results

In comparison with HC, CD4⁺ T cells highly expressed LAG-3, TIM-3, and PD-1 in PBMCs from chronic ASCs with HBeAg-negative. Interestingly, the expressions of TIM-3 and PD-1 on circulating follicular helper T (Tfh) cells in ASCs were significantly high. Moreover, high expressions of LAG-3, TIM-3, and PD-1 were different among Treg, Th1, Th2, and Th17 cells. In addition, the expressions of TIM-3 and CTLA-4 mRNA in PBMCs from ASCs were significantly elevated. However, the frequency of CTLA-4⁺CD4⁺ T cell subsets in PBMCs from ASCs was not different from HC. The levels of six cytokines in serum from ASCs were not clearly different from HC.

Conclusion

Immune checkpoint molecules highly expressed on CD4⁺ T cell subsets indicated an important role in chronic ASCs with HBeAg-negative, which provided potential therapeutic targets in the pathogenesis of chronic HBV infection.

Review article: hepatitis B-current and emerging therapies

BACKGROUND

The hepatitis B virus (HBV) affects an estimated 290 million individuals worldwide and is responsible for approximately 900 000 deaths annually, mostly from complications of cirrhosis and hepatocellular carcinoma. Although current treatment is effective at preventing complications of chronic hepatitis B, it is not curative, and often must be administered long term. There is a need for safe, effective, finite duration curative therapy.

AIM

Our aim was to provide a concise, up to date review of all currently available and emerging treatment options for chronic hepatitis B.

METHODS

We conducted a search of PubMed, clinicaltrials.gov, major meeting abstracts and pharmaceutical websites for publications and communications on current and emerging therapies for HBV.

RESULTS

Currently approved treatment options for chronic hepatitis B include peginterferon alpha-2a and nucleos(t)ide analogues. Both options do not offer a 'complete cure' (clearance of covalently closed circular DNA (cccDNA) and integrated HBV DNA) and rarely achieve a 'functional cure' (hepatitis B surface antigen (HBsAg) loss). An improved understanding of the viral lifecycle, immunopathogenesis and recent advances in drug delivery technologies have led to many novel therapeutic approaches that are currently being evaluated in clinical trials including targeting of viral entry, cccDNA, viral transcription, core protein, and release of HBsAg and HBV polymerase. Additionally, novel immunological approaches that include targeting the innate and adaptive immune system and therapeutic vaccination are being pursued.

CONCLUSION

The breadth and scope of novel therapies in development hold promise for regimen/s that will achieve functional cure.

Dysfunctional State of T Cells or Exhaustion During Chronic Viral Infections and COVID-19: A Review

Coronavirus disease 2019 (COVID-19) continuously affecting the lives of millions of people. The virus is spread through the respiratory route to an uninfected person, causing mild-to-moderate respiratory disease-like symptoms that sometimes progress to severe form and can be fatal. When the host is infected with the virus, both innate and adaptive immunity comes into play. The effector T cells act as the master player of adaptive immune response in eradicating the virus from the system. But during cancer and chronic viral infections, the fate of an effector T cell is altered, and the T cell may enters a state of exhaustion, which is marked by loss of effector function, depleted proliferative capacity and cytotoxic effect accomplished by an increased expression of numerous inhibitory receptors such as programmed cell death protein 1 (PD-1), lymphocyte-activation protein 3 (LAG-3), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on their surface. Various other transcriptional and epigenetic changes take place inside the T cell when it enters into an exhausted state. Latest studies point toward the induction of an abnormal immune response such as lymphopenia, cytokine storm, and T cell exhaustion during SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. This review sheds light on the dysfunctional state of T cells during chronic viral infection and COVID-19. Understanding the cause and the effect of T cell exhaustion observed during COVID-19 may help resolve new therapeutic potentials for treating chronic infections and other diseases.