Regulatory NK cells mediated between immunosuppressive monocytes and dysfunctional T cells in chronic HBV infection

Restoration of CD3+CD56+ NKT-like cell function by TIGIT blockade in inactive carrier and immune tolerant patients of chronic hepatitis B virus infection

Chronic hepatitis B (CHB) virus infection, which can be divided into immune-tolerant (IT), immune-active (IA), inactive carrier (IC) phases, and HBeAg-negative hepatitis (ENEG), can induce liver cirrhosis and eventually hepatocellular carcinoma (HCC). CD3+CD56+ NKT-like cells play an important role in antiviral immune response. However, the mechanism of NKT-like cells to mediate immune tolerance remains largely elusive. In this study, we observed circulating NKT-like cells from IC and IT CHB patients were phenotypically and functionally impaired, manifested by increased expression of inhibitory receptor TIGIT and decreased capacity of secreting antiviral cytokines. Besides, TIGIT+ NKT-like cells of IC and IT CHB patients expressed lower levels of cytotoxic cytokines than the TIGIT- subset. Furthermore, increased expression of CD155, the ligand of TIGIT, on plasmacytoid dendritic cells (pDCs) was detected in IC and IT CHB patients. Importantly, the co-culture of NKT-like cells and pDCs showed that NKT-like cells restored their antiviral ability after TIGIT blockade upon HBV peptide stimulation in IC and IT CHB patients. In conclusion, our findings suggest that the TIGIT pathway may mediate immune tolerance in IT CHB patients and lead to functional impairment in IC patients, indicating that TIGIT may be a potential therapeutic checkpoint for immunotherapy of CHB patients.

Uncommon Adverse Events of Immune Checkpoint Inhibitors in Small Cell Lung Cancer: A Systematic Review of Case Reports

BACKGROUND

This study aimed to systematically review case reports documenting rare adverse events in patients with small cell lung cancer (SCLC) following the administration of immune checkpoint inhibitors (ICIs).

METHODS

A systematic literature review was conducted to identify case reports detailing previously unreported adverse drug reactions to ICIs in patients with SCLC. The scope of the literature reviewed was restricted to case studies on SCLC published up to 31 December 2023.

RESULTS

We analyzed twenty-four studies on ICI use for patients with SCLC. There were six reports on atezolizumab, four on durvalumab, and three on adverse events from monotherapy with nivolumab. Reports involving combination treatments were the most frequent, with a total of six, predominantly involving using nivolumab in combination with ipilimumab. Additionally, there was one report each on using pembrolizumab, nofazinilimab, sintilimab, tislelizumab, and toripalimab. We collected detailed information on the clinical course, including patient and disease characteristics, symptoms, treatment for each adverse event, and recovery status. Among the patients included in the case reports, 21 out of 24 (87.5%) had extensive-stage SCLC when initiating ICI therapy, with only 1 patient diagnosed with limited-stage SCLC. Respiratory system adverse events were most common, with seven cases, followed by neurological, endocrinological, and gastroenterological events. Three case reports documented adverse events across multiple systems in a single patient. In most cases, patients showed symptom improvement; however, four studies reported cases where patients either expired without symptom improvement or experienced sequelae.

CONCLUSIONS

Efforts to develop reliable biomarkers for predicting irAEs continue, with ongoing research to enhance predictive precision. Immunotherapy presents diverse and unpredictable adverse events, underscoring the need for advanced diagnostic tools and a multidisciplinary approach to improve patient management.

Cytokine Response of Natural Killer Cells to Hepatitis B Virus Infection Depends on Monocyte Co-Stimulation

Hepatitis B virus (HBV) is a major driver of chronic hepatic inflammation, which regularly leads to liver cirrhosis or hepatocellular carcinoma. Immediate innate immune cell response is crucial for the rapid clearance of the infection. Here, natural killer (NK) cells play a pivotal role in direct cytotoxicity and the secretion of antiviral cytokines as well as regulatory function. The aim of this study was to further elucidate NK cell responses triggered by an HBV infection. Therefore, we optimized HBV in vitro models that reliably stimulate NK cells using hepatocyte-like HepG2 cells expressing the Na+-taurocholate co-transporting polypeptide (NTCP) and HepaRG cells. Immune cells were acquired from healthy platelet donors. Initially, HepG2-NTCP cells demonstrated higher viral replication compared to HepaRG cells. Co-cultures with immune cells revealed increased production of interferon-γ and tumor necrosis factor-α by NK cells, which was no longer evident in isolated NK cells. Likewise, the depletion of monocytes and spatial separation from target cells led to the absence of the antiviral cytokine production of NK cells. Eventually, the combined co-culture of isolated NK cells and monocytes led to a sufficient cytokine response of NK cells, which was also apparent when communication between the two immune cell subpopulations was restricted to soluble factors. In summary, our study demonstrates antiviral cytokine production by NK cells in response to HBV+ HepG2-NTCP cells, which is dependent on monocyte bystander activation.

Galectin-3-ITGB1 Signaling Mediates Interleukin 10 Production of Hepatic Conventional Natural Killer Cells in Hepatitis B Virus Transgenic Mice and Correlates with Hepatocellular Carcinoma Progression in Patients

BACKGROUND AND AIMS

The outcomes of HBV infections are related to complex immune imbalances; however, the precise mechanisms by which HBV induces immune dysfunction are not well understood.

METHODS

HBV transgenic (HBs-Tg) mice were used to investigate intrahepatic NK cells in two distinct subsets: conventional NK (cNK) and liver-resident NK (LrNK) cells during a chronic HBV infection.

RESULTS

The cNK cells, but not the LrNK cells, were primarily responsible for the increase in the number of bulk NK cells in the livers of ageing HBs-Tg mice. The hepatic cNK cells showed a stronger ability to produce IL-10, coupled with a higher expression of CD69, TIGIT and PD-L1, and lower NKG2D expression in ageing HBs-Tg mice. A lower mitochondrial mass and membrane potential, and less polarized localization were observed in the hepatic cNK cells compared with the splenic cNK cells in the HBs-Tg mice. The enhanced galectin-3 (Gal-3) secreted from HBsAg+ hepatocytes accounted for the IL-10 production of hepatic cNK cells via ITGB1 signaling. For humans, LGALS3 and ITGB1 expression is positively correlated with IL-10 expression, and negatively correlated with the poor clinical progression of HCC.

CONCLUSIONS

Gal-3-ITGB1 signaling shapes hepatic cNK cells but not LrNK cells during a chronic HBV infection, which may correlate with HCC progression.

Can quantitative surface antigen levels and systemic immune-inflammation index be predictive as a new indicator for the initiation of treatment in chronic hepatitis b?

OBJECTIVES

The natural history of chronic HBV infection (CHB) is generally divided into four phases: HBeAg-positive chronic HBV infection (EPCI) and -hepatitis (EPCH), HBeAg-negative chronic HBV infection (ENCI) and -hepatitis (ENCH). This study aimed to investigate changes in serum quantitative surface antigen (qHBsAg), systemic immune-inflammation index (SII) and systemic inflammatory response index (SIRI) in a large number of CHB patients.

METHOD

Three hundred seventy-two CHB patients who underwent liver biopsy between January 2015 and February 2020 were evaluated.

RESULTS

The SII-values were strongly significant between EPCI-EPCH ( P = 0.002), however, there was significant difference between ENCI-ENCH ( P = 0.025). Considering the SIRI results, there was a significant difference between both EPCI-EPCH ( P = 0.009) and ENCI-ENCH ( P = 0.118). In HBeAg-positive patients HBV-DNA, qHBsAg, and SII were found to be predictive ( P = 0.029, P = 0.039, P = 0.027, respectively) while in HBeAg-negative patients, age, AST, HBV-DNA, qHBsAg, SII, and SIRI were found to be predictive ( P = 0.047, P = 0.084, P = <0.001, P = 0.001, P = 0.012, P = 0.002, respectively). In EPCH phase, whereby accuracy rate results of HBV-DNA, qHBsAg, and SII were 75.3%, 73.4%, and 60.4%, respectively, while in the ENCH phase the accuracy rates of age, AST, HBV-DNA, qHBsAg, SII, and SIRI values were 57.8%, 65.6%, 68.3%, 63.8%, 57.3% and 53.2%, respectively.

CONCLUSION

HBV-DNA, qHBsAg, and SII are predictive in EPCH patients. Age, AST, HBV-DNA, qHBsAg, SII and SIRI are all predictive in ENCH patients. In patients with CHB, we recommend using SII to distinguish between EPCI-EPCH and ENCI-ENCH. Based on its sensitivity and features, we believe that qHBsAg and SII are suitable measuring instruments in discrimination both of EPCI-EPCH and ENCI-ENCH.

From hepatitis B virus infection to acute-on-chronic liver failure: The dynamic role of hepatic macrophages

Acute-on-chronic liver failure (ACLF) is a progressive disease that is associated with rapid worsening of clinical symptoms and high mortality. A multicentre prospective study from China demonstrated that patients with hepatitis B virus-related ACLF (HBV-ACLF) exhibited worse clinical characteristics and higher mortality rates compared to non-HBV-ACLF patients. Immune dysregulation is closely linked to the potential mechanisms of initiation and progression of ACLF. Innate immune response, which is represented by monocytes/macrophages, is up-regulated across ACLF development. This suggests that monocytes/macrophages play an essential role in maintaining the immune homeostasis of ACLF. Information that has been published in recent years shows that the immune status and function of monocytes/macrophages vary in ACLF precipitated by different chronic liver diseases. Monocytes/macrophages have an immune activation effect in hepatitis B-precipitated-ACLF, but they exhibit an immune suppression in cirrhosis-precipitated-ACLF. Therefore, this review aims to explain whether this difference affects the clinical outcome in HBV-ACLF patients as well as the mechanisms involved. We summarize the novel findings that highlight the dynamic polarization phenotype and functional status of hepatic macrophages from the stage of HBV infection to ACLF development. Moreover, we discuss how different HBV-related liver disease tissue microenvironments affect the phenotype and function of hepatic macrophages. In summary, increasing developments in understanding the differences in immune phenotype and functional status of hepatic macrophages in ACLF patients will provide new perspectives towards the effective restoration of ACLF immune homeostasis.

The novel mechanism facilitating chronic hepatitis B infection: immunometabolism and epigenetic modification reprogramming

Hepatitis B Virus (HBV) infections pose a global public health challenge. Despite extensive research on this disease, the intricate mechanisms underlying persistent HBV infection require further in-depth elucidation. Recent studies have revealed the pivotal roles of immunometabolism and epigenetic reprogramming in chronic HBV infection. Immunometabolism have identified as the process, which link cell metabolic status with innate immunity functions in response to HBV infection, ultimately contributing to the immune system's inability to resolve Chronic Hepatitis B (CHB). Within hepatocytes, HBV replication leads to a stable viral covalently closed circular DNA (cccDNA) minichromosome located in the nucleus, and epigenetic modifications in cccDNA enable persistence of infection. Additionally, the accumulation or depletion of metabolites not only directly affects the function and homeostasis of immune cells but also serves as a substrate for regulating epigenetic modifications, subsequently influencing the expression of antiviral immune genes and facilitating the occurrence of sustained HBV infection. The interaction between immunometabolism and epigenetic modifications has led to a new research field, known as metabolic epigenomics, which may form a mutually reinforcing relationship with CHB. Herein, we review the recent studies on immunometabolism and epigenetic reprogramming in CHB infection and discuss the potential mechanisms of persistent HBV infection. A deeper understanding of these mechanisms will offer novel insights and targets for intervention strategies against chronic HBV infection, thereby providing new hope for the treatment of related diseases.

Blockage of CacyBP inhibits macrophage recruitment and improves anti-PD-1 therapy in hepatocellular carcinoma

BACKGROUND

Despite remarkable advancements in cancer immunotherapy, the overall response rate to anti-programmed cell death-1 (anti-PD-1) therapy in hepatocellular carcinoma (HCC) patients remains low. Our previous study has demonstrated the critical role of CacyBP/SIP (Calcyclin-Binding Protein and Siah-1 Interacting Protein) as a regulator of HCC development and progression. However, the possible impact of CacyBP on the tumor immune microenvironment has not yet been clarified.

METHODS

The expressions of CacyBP and Myd88 in HCC cell lines and tissues was detected by bioinformatics analysis, real-time quantitative PCR, western blotting and immunohistochemistry. The interaction between CacyBP and Myd88 was measured using co-immunoprecipitation and immunofluorescence. In vitro and in vivo assays were used to investigate the regulation of CacyBP on tumor-associated macrophages (TAMs).

RESULTS

We identified that CacyBP was positively correlated with Myd88, a master regulator of innate immunity, and Myd88 was a novel binding substrate downstream of CacyBP in HCC. Additionally, CacyBP protected Myd88 from Siah-1-mediated proteasome-dependent degradation by competitively binding to its Toll/interleukin-1 receptor (TIR) domain. Inhibition of CacyBP-Myd88 signaling subsequently diminished HDAC1-mediated H3K9ac and H3K27ac modifications on the CX3CL1 promoter and reduced its transcription and secretion in HCC cells. Moreover, by using in vitro and in vivo strategies, we demonstrated that depletion of CacyBP impaired the infiltration of TAMs and the immunosuppressive state of the tumor microenvironment, further sensitizing HCC-bearing anti-PD-1 therapy.

CONCLUSIONS

Our findings suggest that targeting CacyBP may be a novel treatment strategy for improving the efficacy of anti-PD-1 immunotherapy in HCC.

HBV suppresses macrophage immune responses by impairing the TCA cycle through the induction of CS/PDHC hyperacetylation

BACKGROUND

It is now understood that HBV can induce innate and adaptive immune response disorders by affecting immunosuppressive macrophages, resulting in chronic HBV infection. However, the underlying mechanism is not fully understood. Dysregulated protein acetylation can reportedly influence the differentiation and functions of innate immune cells by coordinating metabolic signaling. This study aims to assess whether HBV suppresses macrophage-mediated innate immune responses by affecting protein acetylation and to elucidate the underlying mechanisms of HBV immune escape.

METHODS

We investigated the effect of HBV on the acetylation levels of human THP-1 macrophages and identified potential targets of acetylation that play a role in glucose metabolism. Metabolic and immune phenotypes of macrophages were analyzed using metabolomic and flow cytometry techniques. Western blot, immunoprecipitation, and immunofluorescence were performed to measure the interactions between deacetylase and acetylated targets. Chronic HBV persistent infected mice were established to evaluate the role of activating the tricarboxylic acid (TCA) cycle in macrophages for HBV clearance.

RESULTS

Citrate synthase/pyruvate dehydrogenase complex hyperacetylation in macrophages after HBV stimulation inhibited their enzymatic activities and was associated with impaired TCA cycle and M2-like polarization. HBV downregulated Sirtuin 3 (SIRT3) expression in macrophages by means of the toll-like receptor 2 (TLR2)-NF-κB- peroxisome proliferatoractivated receptor γ coactivator 1α (PGC-1α) axis, resulting in citrate synthase/pyruvate dehydrogenase complex hyperacetylation. In vivo administration of the TCA cycle agonist dichloroacetate inhibited macrophage M2-like polarization and effectively reduced the number of serum HBV DNA copies.

CONCLUSIONS

HBV-induced citrate synthase/pyruvate dehydrogenase complex hyperacetylation negatively modulates the innate immune response by impairing the TCA cycle of macrophages. This mechanism represents a potential therapeutic target for controlling HBV infection.

Activation of AIM2 by hepatitis B virus results in antiviral immunity that suppresses hepatitis C virus during coinfection

IMPORTANCE

Clinical data suggest that Hepatitis C virus (HCV) levels are generally lower in Hepatitis B virus (HBV) co-infected patients, but the mechanism is unknown. Here, we show that HBV, but not HCV, activated absent in melanoma-2. This in turn results in inflammasome-mediated cleavage of pro-IL-18, leading to an innate immune activation cascade that results in increased interferon-γ, suppressing both viruses.

Intestinal Microbiota Dysbiosis Promotes Mucosal Barrier Damage and Immune Injury in HIV-Infected Patients

The intestinal microbiota is an "invisible organ" in the human body, with diverse components and complex interactions. Homeostasis of the intestinal microbiota plays a pivotal role in maintaining the normal physiological process and regulating immune homeostasis. By reviewing more than one hundred related studies concerning HIV infection and intestinal microbiota from 2011 to 2023, we found that human immunodeficiency virus (HIV) infection can induce intestinal microbiota dysbiosis, which not only worsens clinical symptoms but also promotes the occurrence of post-sequelae symptoms and comorbidities. In the early stage of HIV infection, the intestinal mucosal barrier is damaged and a persistent inflammatory response is induced. Mucosal barrier damage and immune injury play a pivotal role in promoting the post-sequelae symptoms caused by HIV infection. This review summarizes the relationship between dysbiosis of the intestinal microbiota and mucosal barrier damage during HIV infection and discusses the potential mechanisms of intestinal barrier damage induced by intestinal microbiota dysbiosis and inflammation. Exploring these molecular mechanisms might provide new ideas to improve the efficacy of HIV treatment and reduce the incidence of post-sequelae symptoms.

Association between AHR Expression and Immune Dysregulation in Pancreatic Ductal Adenocarcinoma: Insights from Comprehensive Immune Profiling of Peripheral Blood Mononuclear Cells

Pancreatic cancer, particularly pancreatic ductal adenocarcinoma (PDAC), has an immune suppressive environment that allows tumour cells to evade the immune system. The aryl-hydrocarbon receptor (AHR) is a transcription factor that can be activated by certain exo/endo ligands, including kynurenine (KYN) and other tryptophan metabolites. Once activated, AHR regulates the expression of various genes involved in immune responses and inflammation. Previous studies have shown that AHR activation in PDAC can have both pro-tumorigenic and anti-tumorigenic effects, depending on the context. It can promote tumour growth and immune evasion by suppressing anti-tumour immune responses or induce anti-tumour effects by enhancing immune cell function. In this study involving 30 PDAC patients and 30 healthy individuals, peripheral blood samples were analysed. PDAC patients were categorized into Low (12 patients) and High/Medium (18 patients) AHR groups based on gene expression in peripheral blood mononuclear cells (PBMCs). The Low AHR group showed distinct immune characteristics, including increased levels of immune-suppressive proteins such as PDL1, as well as alterations in lymphocyte and monocyte subtypes. Functional assays demonstrated changes in phagocytosis, nitric oxide production, and the expression of cytokines IL-1, IL-6, and IL-10. These findings indicate that AHR's expression level has a crucial role in immune dysregulation in PDAC and could be a potential target for early diagnostics and personalised therapeutics.

Hepatitis B Virus Envelope Antigen and Hepatitis B Virus Surface Antigen Both Contribute to the Innate Immune Response During Persistent Hepatitis B Virus Infection

This study aimed to investigate the changes of toll-like receptor 4 (TLR4), proinflammatory cytokine expression, hepatitis B virus surface antigen (HBsAg), and hepatitis B virus envelope antigen (HBeAg) expression as well as innate immune cell percentages in a mouse model of persistent hepatitis B virus (HBV) infection to better understand the innate immune response. Mouse models of persistent HBV infection, HBsAg expression, and HBeAg expression were developed using high-pressure tail-vein injection of recombinant adeno-associated viruses. Enzyme-linked immunosorbent assays (ELISAs) were used to determine the serum proinflammatory cytokine levels. Immunohistochemistry and western blot assays were used to detect TLR4 expression. Flow cytometric analysis was used to assess the percentage of innate immune cells in the whole blood. Persistent HBV infection, HBsAg expression, and HBeAg expression each significantly decreased the expression of TLR4. Persistent HBV infection significantly increased the percentages of T cells and monocytes, whereas it decreased the percentage of natural killer (NK) cells. Persistent HBeAg expression also decreased the percentage of NK cells, whereas persistent HBsAg expression increased the percentage of NK cells. Both persistent HBsAg and HBeAg expression increased the percentage of monocytes. However, both persistent HBsAg and HBeAg expression decreased the percentage of T cells. HBV as well as HBsAg and HBeAg showed similar effects on the expression of TLR4 and proinflammatory cytokines as well as the percentage of monocytes. Persistent HBV infection increased the percentage of T cells and decreased the percentage of NK cells, whereas only persistent HBeAg expression contributed to a decreased percentage of NK cells.

Interspecies comparison of the early transcriptomic changes associated with hepatitis B virus exposure in human and macaque immune cell populations

Background and aims

Hepatitis B virus (HBV) infection affects 300 million individuals worldwide, representing a major factor for the development of hepatic complications. Although existing antivirals are effective in suppressing replication, eradication of HBV is not achieved. Therefore, a multi-faceted approach involving antivirals and immunomodulatory agents is required. Non-human primates are widely used in pre-clinical studies due to their close evolutionary relationship to humans. Nonetheless, it is fundamental to identify the differences in immune response between humans and these models. Thus, we performed a transcriptomic characterization and interspecies comparison of the early immune responses to HBV in human and cynomolgus macaques.

Methods

We characterized early transcriptomic changes in human and cynomolgus B cells, T cells, myeloid and plasmacytoid dendritic cells (pDC) exposed to HBV ex vivo for 2 hours. Differentially-expressed genes were further compared to the profiles of HBV-infected patients using publicly-available single-cell data.

Results

HBV induced a wide variety of transcriptional changes in all cell types, with common genes between species representing only a small proportion. In particular, interferon gamma signaling was repressed in human pDCs. At the gene level, interferon gamma inducible protein 16 (IFI16) was upregulated in macaque pDCs, while downregulated in humans. Moreover, IFI16 expression in pDCs from chronic HBV-infected patients anti-paralleled serum HBsAg levels.

Conclusion

Our characterization of early transcriptomic changes induced by HBV in humans and cynomolgus macaques represents a useful resource for the identification of shared and divergent host responses, as well as potential immune targets against HBV.

The hepatitis B virus pre-core protein p22 suppresses TNFα-induced apoptosis by regulating the NF-κB pathway

OBJECTIVE

Cell apoptosis is strongly associated with hepatocellular carcinoma (HCC) progress. Thus, gaining a comprehensive understanding of the virus interfering with the apoptotic process is important for the development of effective anti-tumor therapies. The objective of this study is to explore the potential involvement of HBeAg-p22 (HBV-p22) in TNFα-induced apoptosis.

METHODS

Protein expression was detected using western blot. Cell viability and apoptosis were assessed by employing Cell Counting Kit-8 (CCK8) and flow cytometry, respectively. Evaluation of protein-protein interactions was accomplished through co-immunoprecipitation and glutathione-S-transferase (GST) pull-down assays.

RESULTS

In this study, it was shown that HBV-p22 inhibited apoptosis of human hepatoma cell lines after tumor necrosis factor-alpha (TNF-α) stimulation. Mechanistically, HBV-p22 suppressed Jun N-terminal kinases (JNK) signaling and enhanced nuclear factor kappa-B (NF-κB) signaling. Moreover, HBV-p22 interacted with I-kappa B kinase α (IKKα) and increased its phosphorylation.

CONCLUSIONS

Collectively, HBV-p22, whereby the mechanism contributing to anti-apoptotic effect was regulation of the NF-κB pathway via enhancing the phosphorylation of IKKα.

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.

Treatment of Liver Fibrosis after Hepatitis B with TCM Combined with NAs Evaluated by Noninvasive Diagnostic Methods: A Retrospective Study

Objective. Chronic hepatitis B liver fibrosis is an important intermediate link in the development of liver cirrhosis. A retrospective cohort study was conducted in Longhua Hospital affiliated to the Shanghai University of Traditional Chinese Medicine in order to prove whether integrated traditional Chinese and Western medicine could improve the incidence of CHB complications and clinical prognosis. There are 130 patients with hepatitis B liver fibrosis (being treated from 2011-2021) included in the study, and the patients were divided into 64 TCM users (NAs combined with TCM) and 66 TCM nonusers (NAs antiviral therapy). The serum noninvasive diagnostic model (APRI, FIB-4) and LSM value were used to classify the stages of fibrosis. The results showed that the LSM value was decreased significantly in TCM users compared with TCM nonusers (40.63% versus 28.79%). Indicators of FIB-4 and APRI of TCM users have improved significantly compared with that of TCM nonusers (32.81% versus 10.61% and 35.94% versus 24.24%). The AST, TBIL, and HBsAg levels in TCM users were lower than those in TCM nonusers, and the HBsAg level was inversely correlated with the CD3+, CD4+, and CD8+ in TCM users. The PLT and spleen thickness of TCM users also were improved considerably. The incidence rate of end-point events (decompensated cirrhosis/liver cancer) in TCM nonusers was higher than that of TCM users (16.67% versus 1.56%). The long course of the disease and a family history of hepatitis B were the risk factors for disease progression, and long-term oral administration of TCM was the protective factor. As a result, the serum noninvasive fibrosis index and imaging parameters in TCM users were lower than those of TCM nonusers. Patients in the treatment of NAs combined with TCM had better prognoses such as a lower HBsAg level, a more stable lymphocyte function, and a lower incidence of end-point events. The present findings suggest the effect of TCM combined with NAs in the treatment of chronic hepatitis B liver fibrosis is better than that of single drug treatment.

The surge of HBsAb level in a HBsAg-negative ES-SCLC patient after anlotinib plus atezolizumab treatment: A case report

Small-cell lung cancer (SCLC) is a poorly differentiated neuroendocrine tumor with endocrine function. For decades, chemotherapy and immune checkpoint inhibitors (ICIs) have been the first-line treatment options. Because of its ability to normalize tumor vessels, anlotinib is recommended as a novel therapy as a third-line treatment. A combination of anti-angiogenic drugs and ICIs can effectively and safely benefit advanced cancer patients. However, immune-related side effects caused by ICIs are common. Hepatitis B virus (HBV) reactivation and hepatitis are common during immunotherapy in patients with chronic HBV infection. A 62-year-old man with ES-SCLC who had brain metastasis was described in this case. It is unusual for a HBsAg-negative patient to develop an increase in HBsAb after receiving atezolizumab immunotherapy. Although some researchers have reported the functional cure of HBV by PD-L1 antibody, this is the first case that showed a sustained increased in HBsAb level after anti-PD-L1 therapy. It is related with CD4+ and CD8+ T cells activation and HBV infection microenvironment. Importantly, this could provide a solution to insufficient protective antibody production after vaccination as well as a therapeutic opportunity for HBV patients with cancers.

NLRP3 inflammasome-induced pyroptosis in digestive system tumors

Programmed cell death (PCD) refers to cell death in a manner that depends on specific genes encoding signals or activities. PCD includes apoptosis, pyroptosis, autophagy and necrosis (programmed necrosis). Among these mechanisms, pyroptosis is mediated by the gasdermin family and is accompanied by inflammatory and immune responses. When pathogens or other danger signals are detected, cytokine action and inflammasomes (cytoplasmic multiprotein complexes) lead to pyroptosis. The relationship between pyroptosis and cancer is complex and the effect of pyroptosis on cancer varies in different tissue and genetic backgrounds. On the one hand, pyroptosis can inhibit tumorigenesis and progression; on the other hand, pyroptosis, as a pro-inflammatory death, can promote tumor growth by creating a microenvironment suitable for tumor cell growth. Indeed, the NLRP3 inflammasome is known to mediate pyroptosis in digestive system tumors, such as gastric cancer, pancreatic ductal adenocarcinoma, gallbladder cancer, oral squamous cell carcinoma, esophageal squamous cell carcinoma, in which a pyroptosis-induced cellular inflammatory response inhibits tumor development. The same process occurs in hepatocellular carcinoma and some colorectal cancers. The current review summarizes mechanisms and pathways of pyroptosis, outlining the involvement of NLRP3 inflammasome-mediated pyroptosis in digestive system tumors.

Exosome and virus infection

Exosomes are messengers of intercellular communication in monolayer vesicles derived from cells. It affects the pathophysiological process of the body in various diseases, such as tumors, inflammation, and infection. It has been confirmed that exosomes are similar to viruses in biogenesis, and exosome cargo is widely involved in many viruses’ replication, transmission, and infection. Simultaneously, virus-associated exosomes can promote immune escape and activate the antiviral immune response of the body, which bidirectionally modulates the immune response. This review focuses on the role of exosomes in HIV, HBV, HCV, and SARS-CoV-2 infection and explores the prospects of exosome development. These insights may be translated into therapeutic measures for viral infections and reduce the disease burden.

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.

SIRT7 affects autophagy and activation of hepatic stellate cells by regulating the acetylation level of high mobility group protein 1

OBJECTIVE

Preventing the progression of hepatic fibrosis is an important strategy to improve the prognosis of liver disease. The purpose of this study was to investigate the role of sirtuin7 (SIRT7) and high mobility group box 1 (HMGB1) acetylation in the occurrence and development of hepatic fibrosis.

MATERIALS AND METHODS

Hepatic fibrosis mice model was induced by CCl₄. TGF-β1 was used to activated quiescent hepatic stellate cell (qHSC) into activated HSC (aHSC). Hematoxylin-eosin evaluated hepatic fibrosis in vivo, and the distribution of α-smooth muscle actin (α-SMA) or HMGB1 was detected by immunohistochemistry or immunofluorescence. The expressions of SIRT7, autophagy related proteins, and HSC activation-related proteins were detected by Western blot. Immunoprecipitation detected the acetylation level of HMGB1. Lysine mutants of HMGB1 were constructed in vitro to explore the acetylation sites of HMGB1.

RESULTS

Hepatocyte autophagy and activation levels were enhanced in CCl₄ group or aHSC group, and the acetylation level of HMGB1 was increased. Nuclear transfer of HMGB1 occurred in aHSC, and HMGB1was mainly distributed in cytoplasm. The expression of SIRT7 in CCl₄ group or aHSC group was most significantly decreased, and knockdown of SIRT7 leads to increased levels of HSCs autophagy and activation. Overexpression of SIRT7 or interference of HMGB1 alone in aHSC can reduce the level of autophagy and activation of aHSC. However, continued overexpression of SIRT7 in shHMGB1-aHSC could not reduce the autophagy and activation levels of aHSC. Among the 11 Flag-HMGB1 mutants, the acetylation level of K86R-Flag-HMGB1 was the lowest. The acetylation level of K86R-Flag-HMGB1 did not change due to SIRT7 downregulation.

CONCLUSION

This study proved that SIRT7 can directly target the K86R site of HMGB1 and participate in regulating the expression and distribution of HMGB1, thus affecting the autophagy and activation level of HSCs.

TLR8 agonist partially improves IFN-γ deficiency of NK cells in chronic hepatitis B through the synergy of monocytes

BACKGROUND

Natural killer (NK) cells exhibit a selective deficiency of IFN-γ production in chronic hepatitis B (CHB). Toll-like receptor 8 (TLR8) agonists could induce IFN-γ production in immune cells, although their effects on the deficiency in NK cells remain unclear.

AIMS

To investigate TLR8 expression in NK cells and the effect of TLR8 agonists in patients with CHB METHODS: We enrolled 32 patients with CHB and 19 healthy controls to assess TLR8 expression and IFN-γ production in NK cells. The sorted NK cells and monocytes were co-cultured to compare the extent of IFN-γ and IL-10 production after TLR8 agonist ssRNA40 stimulation. The synergic effect of NK cells and monocytes was assessed by blocking IL-12 and IL-18. We recruited another 22 patients with CHB undergoing nucleotide analogue (NA) therapy to explore the impact of antiviral treatment on the ssRNA40-mediated response of NK cells.

RESULTS

In patients with CHB, TLR8 expression in NK cells was up-regulated, accompanied by insufficient IFN-γ production. The enhanced IFN-γ secretion by ssRNA40 in NK cells depended on monocyte-derived IL-12 and IL-18. NK cells displayed an imbalanced response to ssRNA40 in patients with CHB with a weak increase in IFN-γ despite a higher IL-10 production. The response was improved in patients with CHB undergoing NA therapy.

CONCLUSIONS

In patients with CHB, targeting TLR8 partially rescues the IFN-γ insufficiency in NK cells. However, NK cells show an inhibitory response to TLR8 agonist stimulation. TLR8 agonist combined with NA may enhance the antiviral effect of NK cells.

Clinical application and prospect of immune checkpoint inhibitors for CAR-NK cell in tumor immunotherapy

Chimeric antigen receptor (CAR) engineering of natural killer (NK) cells is an attractive research field in tumor immunotherapy. While CAR is genetically engineered to express certain molecules, it retains the intrinsic ability to recognize tumor cells through its own receptors. Additionally, NK cells do not depend on T cell receptors for cytotoxic killing. CAR-NK cells exhibit some differences to CAR-T cells in terms of more precise killing, numerous cell sources, and increased effectiveness in solid tumors. However, some problems still exist with CAR-NK cell therapy, such as cytotoxicity, low transfection efficiency, and storage issues. Immune checkpoints inhibit immune cells from performing their normal killing function, and the clinical application of immune checkpoint inhibitors for cancer treatment has become a key therapeutic strategy. The application of CAR-T cells and immune checkpoint inhibitors is being evaluated in numerous ongoing basic research and clinical studies. Immune checkpoints may affect the function of CAR-NK cell therapy. In this review, we describe the combination of existing CAR-NK cell technology with immune checkpoint therapy and discuss the research of CAR-NK cell technology and future clinical treatments. We also summarize the progress of clinical trials of CAR-NK cells and immune checkpoint therapy.

Circulating Monocytes Serve as Novel Prognostic Biomarker in Pancreatic Ductal Adenocarcinoma Patients

Pancreatic ductal adenocarcinoma (PDAC) ranks among the most fatal cancer diseases, widely accepted to have the most dismal prognoses. Although immunotherapy has broadly revolutionized cancer treatment, its value in PDAC appears to be relatively low. Exhibiting protumoral effects, monocytes have recently been proposed as potential targets of such immunotherapeutic regimens. However, to date, the body of evidence on monocytes’ role in PDAC is scarce. Therefore, we analyzed monocytes in the peripheral blood of 58 PDAC patients prior to surgery and compared them to healthy individuals. PDAC patients showed increased levels of monocytes when compared to healthy controls In addition, patients with perineural infiltration demonstrated a higher percentage of monocytes compared to non-infiltrating tumors and PDAC G3 was associated with higher monocyte levels than PDAC G2. Patients with monocyte levels > 5% were found to have an 8.9-fold increased risk for a G3 and perineural infiltrated PDAC resulting in poorer survival compared to patients with <5% monocyte levels. Furthermore, PDAC patients showed increased expressions of CD86 and CD11c and decreased expressions of PD-L1 on monocytes compared to healthy individuals. Finally, levels of monocytes correlated positively with concentrations of IL-6 and TNF-α in plasma of PDAC patients. Based on our findings, we propose monocytes as a novel prognostic biomarker. Large-scale studies are needed to further decipher the role of monocytes in PDAC and investigate their potential as therapeutic targets.

A2AR limits IL-15-induced generation of CD39+ NK cells with high cytotoxicity

CD39-mediated inhibition of natural killer (NK) cell activity has been demonstrated, but the characteristics of CD39⁺ NK cells in humans are not known. We investigated the characteristics of human circulating CD39⁺ NK cells. In healthy donors, the proportion of circulating CD39⁺ NK cells in total NK cells was relatively low compared with that of CD39^- NK cells. Nonetheless, a higher proportion of CD39⁺ NK cells expressed CD107a. Similarly, a higher proportion of CD39⁺ NK cells expressed CD107a in patients with hepatitis B virus or patients with hepatocellular carcinoma. Stimulation with NK-sensitive K562 cells or interleukin (IL)-12/IL-18 activated CD39⁺ NK cells to express higher levels of CD107a, IFN-γ and TNF-α, relative to CD39^- NK cells. Importantly, IL-15 induced the generation of CD39⁺ NK cells. In contrast, A2A adenosine receptor (A2AR) ligation suppressed the generation of CD39⁺ NK cells by inhibiting IL-15 signaling. These data for the first time demonstrated that A2AR counteracts IL-15-induced generation of human CD39⁺ NK cells, which have a stronger cytotoxicity than CD39^- NK cells. IL-15-induced human CD39⁺ NK cells might be better choice for immunotherapy based on adoptive transfer of NK cells.

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.

NAFLD and HBV interplay - related mechanisms underlying liver disease progression

Non-alcoholic fatty liver disease (NAFLD) and Hepatitis B virus infection (HBV) constitute common chronic liver diseases with worldwide distribution. NAFLD burden is expected to grow in the coming decade, especially in western countries, considering the increased incidence of diabetes and obesity. Despite the organized HBV vaccinations and use of anti-viral therapies globally, HBV infection remains endemic and challenging public health issue. As both NAFLD and HBV have been associated with the development of progressive fibrosis, cirrhosis and hepatocellular carcinoma (HCC), the co-occurrence of both diseases has gained great research and clinical interest. The causative relationship between NAFLD and HBV infection has not been elucidated so far. Dysregulated fatty acid metabolism and lipotoxicity in NAFLD disease seems to initiate activation of signaling pathways that enhance pro-inflammatory responses and disrupt hepatocyte cell homeostasis, promoting progression of NAFLD disease to NASH, fibrosis and HCC and can affect HBV replication and immune encountering of HBV virus, which may further have impact on liver disease progression. Chronic HBV infection is suggested to have an influence on metabolic changes, which could lead to NAFLD development and the HBV-induced inflammatory responses and molecular pathways may constitute an aggravating factor in hepatic steatosis development. The observed altered immune homeostasis in both HBV infection and NAFLD could be associated with progression to HCC development. Elucidation of the possible mechanisms beyond HBV chronic infection and NAFLD diseases, which could lead to advanced liver disease or increase the risk for severe complications, in the case of HBV-NAFLD co-existence is of high clinical significance in the context of designing effective therapeutic targets.

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.

Disruption of the HLA-E/NKG2X axis is associated with uncontrolled HIV infections

The contribution of the HLA-E/NKG2X axis in NK-mediated control of HIV infection remains unclear. We have studied the relationship between HLA-E expression and phenotypical as well as functional characteristics of NK cells, in the context of chronic HIV infection and in an in vitro model of acute infection. High viremia in HIV+ individuals was related to increased HLA-E expression, and changes in NK subpopulations, especially a reduction of the CD56bright as well as an increase in adaptive NK subpopulation. Uncontrolled HIV infection was also characterized by a reversion of the NKG2A/NKG2C expression ratio and a loss of positive and negative regulation of NK mediated by HLA-E. This was reflected in a lower cytotoxic, degranulation and cytokine production capacity, especially in CD56bright and adaptive NK. In line with these results, HLA-E expression showed a positive correlation with viral growth inhibition in an in vitro model of acute infection at day 7, which was lost after 14 days of culture. Using HLA-E expressing K562 cells, we determined that only one out of 11 described HIV-derived HLA-E epitopes increased HLA-E surface stability. In spite of that, eight of the 11 epitopes were capable of increasing degranulation and three drove differences in NK-cell mediated cell lysis or cytokine secretion. In conclusion, our results indicate that HLA-E molecules presenting HIV-derived epitopes may sensitize target cells for NK lysis in early HIV infection. However, prolonged exposure to elevated HLA-E expression levels in vivo may lead to NK cell dysfunction and reduced viral control In chronic infection.

TGF-β from the Porcine Intestinal Cell Line IPEC-J2 Induced by Porcine Circovirus 2 Increases the Frequency of Treg Cells via the Activation of ERK (in CD4+ T Cells) and NF-κB (in IPEC-J2)

Porcine circovirus 2 (PCV2) causes immunosuppression. Piglets infected with PCV2 can develop enteritis. Given that the gut is the largest immune organ, however, the response of the gut's immune system to PCV2 is still unclear. Here, IPEC-J2 cells with different treatments were co-cultured with PBMC or CD4⁺ T cells (Transwell). Flow cytometry and Western blotting revealed that PCV2-infected IPEC-J2 increased the frequency of CD4⁺ T cells among piglets' peripheral blood mononuclear cells (PBMCs) and caused CD4⁺ T cells to undergo a transformation into Foxp3⁺ regulatory T cells (Treg cells) via activating CD4⁺ T ERK. Cytokines production and an inhibitor assay showed that the induction of Tregs by PCV2-infected IPEC-J2 was dependent on TGF-β induced by PCV2 in IPEC-J2, which was associated with the activation of NF-κB. Taken together, PCV2-infected IPEC-J2 activated NF-κB to stimulate the synthesis of TGF-β, which enhanced the differentiation of CD4⁺ T cells into Treg cells through the activation of ERK in CD4⁺ T cells. This information sheds light on PCV2's function in the intestinal immune system and suggests a potential immunosuppressive mechanism for PCV2 infection.

STAT1 is associated with NK cell dysfunction by downregulating NKG2D transcription in chronic HBV-infected patients

PURPOSE

Natural killer (NK) cells are key players in the immune system, however, the exact mechanism of NK cell dysfunction during HBV infection remains poorly defined.

METHODS

Hepatitis B envelope antigen-negative (HBeAg-, n = 19) chronic hepatitis B infection (CHB) patients, HBeAg-positive (HBeAg+, n = 20) CHB patients, HBV-related hepatocellular carcinoma (HBV-HCC, n = 12) patients and healthy blood donors (HD, n = 20), were enrolled in our study. The phenotype and function of the corresponding NK cells of these subjects were then determined. NK cells were cocultured with HBV to assess whether HBV influences the activation of STAT1. Receptors, proliferation, apoptosis rate, and cytotoxicity of NK-92 cells were detected after STAT1 overexpression and knockdown. The relationship between STAT1 and NKG2D promoter was determined by luciferase assay.

RESULTS

The levels of NKG2D and STAT1 were the lowest in the HBV-HCC group compared with the HD group, followed by the HBeAg+ group and then the HBeAg- group, respectively. Interestingly, STAT1 levels were positively correlated with NKG2D expression and HBeAg status. Furthermore, STAT1 directly bound to the NKG2D promoter to regulate the transcription and expression of NKG2D. Finally, the results also suggested that knockdown of STAT1 can inhibit proliferation, increase apoptosis rate of NK-92 cells and impair cytotoxicity of NK-92 cells.

CONCLUSION

STAT1 is correlated with NK cell dysfunction by downregulating NKG2D transcription in HBV-infected patients. Our findings demonstrate that STAT1 is an important and positive regulator of NK cells, which could provide a potential immunotherapy target for CHB.

When does hepatitis B virus meet long-stranded noncoding RNAs?

Hepatitis B virus (HBV) infection in humans and its associated diseases are long-standing problems. HBV can produce a large number of non-self-molecules during its life cycle, which acts as targets for innate immune recognition and initiation. Among these, interferon and its large number of downstream interferon-stimulated gene molecules are important early antiviral factors. However, the development of an effective antiviral immune response is not simple and depends not only on the delicate regulation of the immune response but also on the various mechanisms of virus-related immune escape and immune tolerance. Therefore, despite there being a relatively well-established consensus on the major pathways of the antiviral response and their component molecules, the complete clearance of HBV remains a challenge in both basic and clinical research. Long-noncoding RNAs (lncRNAs) are generally >200 bp in length and perform different functions in the RNA strand encoding the protein. As an important part of the IFN-inducible genes, interferon-stimulated lncRNAs are involved in the regulation of several HBV infection-related pathways. This review traces the basic elements of such pathways and characterizes the various recent targets of lncRNAs, which not only complement the regulatory mechanisms of pathways related to chronic HBV infection, fibrosis, and cancer promotion but also present with new potential therapeutic targets for controlling HBV infection and the malignant transformation of hepatocytes.

Intrahepatic transcriptomics reveals gene signatures in chronic hepatitis B patients responded to interferon therapy

Chronic hepatitis B virus (HBV) infection remains a substantial public health burden worldwide. Alpha-interferon (IFNα) is one of the two currently approved therapies for chronic hepatitis B (CHB), to explore the mechanisms underlying IFNα treatment response, we investigated baseline and 24-week on-treatment intrahepatic gene expression profiles in 21 CHB patients by mRNA-seq. The data analyses demonstrated that PegIFNα treatment significantly induced antiviral responses. Responders who achieved HBV DNA loss and HBeAg or HBsAg seroconversion displayed higher fold change and larger number of up-regulated interferon-stimulated genes (ISGs). Interestingly, lower expression levels of certain ISGs were observed in responders in their baseline biopsy samples. In HBeAg+ patients, non-responders had relative higher baseline HBeAg levels than responders. More importantly, HBeAg− patients showed higher HBsAg loss rate than HBeAg+ patients. Although a greater fold change of ISGs was observed in HBeAg− patients than HBeAg+ patients, upregulation of ISGs in HBeAg+ responders exceeded HBeAg− responders. Notably, PegIFNα treatment increased monocyte and mast cell infiltration, but decreased CD8 T cell and M1 macrophage infiltration in both responders and non-responders, while B cell infiltration was increased only in responders. Moreover, co-expression analysis identified ribosomal proteins as critical players in antiviral response. The data also indicate that IFNα may influence the production of viral antigens associated with endoplasmic reticulum. Collectively, the intrahepatic transcriptome analyses in this study enriched our understanding of IFN-mediated antiviral effects in CHB patients and provided novel insights into the development of potential strategies to improve IFNα therapy.

miR-146a Maintains Immune Tolerance of Kupffer Cells and Facilitates Hepatitis B Virus Persistence in Mice

Kupffer cells (KCs), the largest tissue-resident macrophage population in the body, play a central role in maintaining a delicate balance between immune tolerance and immunity in the liver. However, the underlying molecular mechanism remains elusive. In this study, we show that KCs express high levels of miR-146a, which is under control of the PU.1 transcription factor. miR-146a deficiency promoted KCs differentiation toward a proinflammatory phenotype; conversely, miR-146a overexpression suppressed this phenotypic differentiation. We found that hepatitis B virus (HBV) persistence or HBV surface Ag treatment significantly upregulated miR-146a expression and thereby impaired polarization of KCs toward a proinflammatory phenotype. Furthermore, in an HBV carrier mouse model, KCs depletion by clodronate liposomes dramatically promoted HBV clearance and enhanced an HBV-specific hepatic CD8⁺ T cell and CD4⁺ T cell response. Consistent with this finding, miR-146a knockout mice cleared HBV faster and elicited a stronger adaptive antiviral immunity than wild-type mice. In vivo IL-12 blockade promoted HBV persistence and tempered the HBV-specific CTL response in the liver of miR-146a knockout mice. Taken together, our results identified miR-146a as a critical intrinsic regulator of an immunosuppressive phenotype in KCs under inflammatory stimuli, which may be beneficial in maintenance of liver homeostasis under physiological condition. Meanwhile, during HBV infection, miR-146a contributed to viral persistence by inhibiting KCs proinflammatory polarization, highlighting its potential as a therapeutic target in HBV infection.

Burgeoning Exploration of the Role of Natural Killer Cells in Anti-PD-1/PD-L1 Therapy

Antibodies targeting programmed death receptor-1 (PD-1)/programmed death ligand-1 (PD-L1) have been considered breakthrough therapies for a variety of solid and hematological malignancies. Although cytotoxic T cells play an important antitumor role during checkpoint blockade, they still show a potential killing effect on tumor types showing loss of/low major histocompatibility complex (MHC) expression and/or low neoantigen load; this knowledge has shifted the focus of researchers toward mechanisms of action other than T cell-driven immune responses. Evidence suggests that the blockade of the PD-1/PD-L1 axis may also improve natural killer (NK)-cell function and activity through direct or indirect mechanisms, which enhances antitumor cytotoxic effects; although important, this topic has been neglected in previous studies. Recently, some studies have reported evidence of PD-1 and PD-L1 expression in human NK cells, performed exploration of the intrinsic mechanism by which PD-1/PD-L1 blockade enhances NK-cell responses, and made some progress. This article summarizes the recent advances regarding the expression of PD-1 and PD-L1 molecules on the surface of NK cells as well as the interaction between anti-PD-1/PD-L1 drugs and NK cells and associated molecular mechanisms in the tumor microenvironment.

Research Progress on the Mechanism of Persistent Low-Level HBsAg Expression in the Serum of Patients with Chronic HBV Infection

Among HBV-infected persons, there is a group of people with hepatitis B surface antigen (HBsAg) showing persistently low levels of expression. The production of low-level HBsAg does not mean a good outcome of chronic HBV infection. Patients still have virus replication and sustained liver damage, and they have the potential to transmit the infection. This risk poses a challenge to clinical diagnosis and blood transfusion safety and is a major concern of experts. However, the mechanism behind persistent low-level HBsAg expression in serum is not completely clear, and complete virus clearance by the host is vital. In this review, we summarize the research progress on the mechanism behind low-level expression of HBsAg in patients with chronic HBV infection in recent years.

Innate and adaptive immune escape mechanisms of hepatitis B virus

Chronic hepatitis B virus (HBV) infection is an international health problem with extremely high mortality and morbidity rates. Although current clinical chronic hepatitis B (CHB) treatment strategies can partly inhibit and eliminate HBV, viral breakthrough may result due to non-adherence to treatment, the emergence of viral resistance, and a long treatment cycle. Persistent CHB infection arises as a consequence of complex interactions between the virus and the host innate and adaptive immune systems. Therefore, understanding the immune escape mechanisms involved in persistent HBV infection is important for designing novel CHB treatment strategies to clear HBV and achieve long-lasting immune control. This review details the immunological and biological characteristics and escape mechanisms of HBV and the novel immune-based therapies that are currently used for treating HBV.

Negative Regulation and Protective Function of Natural Killer Cells in HIV Infection: Two Sides of a Coin

Natural killer (NK) cells play an important immunologic role, targeting tumors and virus-infected cells; however, NK cells do not impede the progression of human immunodeficiency virus (HIV) infection. In HIV infection, NK cells exhibit impaired functions and negatively regulate other immune cell responses, although NK cells can kill HIV-infected cells and thereby suppress HIV replication. Considerable recent research has emerged regarding NK cells in the areas of immune checkpoints, negative regulation, antibody-dependent cell-mediated cytotoxicity and HIV reservoirs during HIV infection; however, no overall summary of these factors is available. This review focuses on several important aspects of NK cells in relation to HIV infection, including changes in NK cell count, subpopulations, and immune checkpoints, as well as abnormalities in NK cell functions and NK cell negative regulation. The protective function of NK cells in inhibiting HIV replication to reduce the viral reservoir and approaches for enhancing NK cell functions are also summarized.

Platelets mediate inflammatory monocyte activation by SARS-CoV-2 Spike protein

Infection with SARS-CoV-2, the causative agent of COVID-19, causes mild to moderate disease in most patients but carries a risk of morbidity and mortality. Seriously affected individuals manifest disorders of hemostasis and a cytokine storm, but it is not understood how these manifestations of severe COVID-19 are linked. Here, we showed that the SARS-CoV-2 spike protein engaged the CD42b receptor to activate platelets via 2 distinct signaling pathways and promoted platelet-monocyte communication through the engagement of P selectin/PGSL-1 and CD40L/CD40, which led to proinflammatory cytokine production by monocytes. These results explain why hypercoagulation, monocyte activation, and a cytokine storm are correlated in patients severely affected by COVID-19 and suggest a potential target for therapeutic intervention.

Role of IL-10-Producing Natural Killer Cells in the Regulatory Mechanisms of Inflammation during Systemic Infection

Natural killer (NK) cells have the dual ability to produce pro-inflammatory (IFNγ) and anti-inflammatory (IL-10) cytokines during systemic infection, which points to their crucial role both as inflammatory effectors for infection clearance and as regulators to counterbalance inflammation to limit immune-mediated damage to the host. In particular, immunosuppressive IL-10 secretion by NK cells has been described to occur in systemic, but not local, infections as a recent immunoregulatory mechanism of inflammation that may be detrimental or beneficial, depending on the timing of release, type of disease, or the infection model. Understanding the factors that drive the production of IL-10 by NK cells and their impact during dualistic inflammatory states, such as sepsis and other non-controlled inflammatory diseases, is relevant for achieving effective therapeutic advancements. In this review, the evidence regarding the immunoregulatory role of IL-10-producing NK cells in systemic infection is summarized and discussed in detail, and the potential molecular mechanisms that drive IL-10 production by NK cells are considered.

MyD88 in myofibroblasts regulates aerobic glycolysis-driven hepatocarcinogenesis via ERK-dependent PKM2 nuclear relocalization and activation

Hepatic stellate cells (HSCs) and cancer-associated fibroblasts (CAFs) play critical roles in liver fibrosis and hepatocellular carcinoma (HCC). MyD88 controls the expression of several key modifier genes in liver tumorigenesis; however, whether and how MyD88 in myofibroblasts contributes to the development of fibrosis-associated liver cancer remain elusive. Here, we used an established hepatocarcinogenesis mouse model involving apparent liver fibrogenesis, in which MyD88 was selectively depleted in myofibroblasts. Myofibroblast MyD88-deficient (Fib-MyD88 KO) mice developed significantly fewer and smaller liver tumor nodules. MyD88 deficiency in myofibroblasts attenuated liver fibrosis and aerobic glycolysis in hepatocellular carcinoma tissues. Mechanistically, MyD88 signaling in myofibroblasts increased the secretion of CCL20, which promoted aerobic glycolysis in cancer cells. This process was dependent on the CCR6 receptor and ERK/PKM2 signaling. Furthermore, liver tumor growth was greatly relieved when the mice were treated with a CCR6 inhibitor. Our data revealed a critical role for MyD88 in myofibroblasts in the promotion of hepatocellular carcinoma by affecting aerobic glycolysis in cancer cells and might provide a potential molecular therapeutic target for HCC. This article is protected by copyright. All rights reserved.

Effects of HBeAg Status on cellular immune function of patients with Hepatitis B virus/Treponema Pallidum Co-infectio

Objectives

This study was aimed at exploring the effects of hepatitis B envelope antigen (HBeAg) status on the cellular immune function of patients with hepatitis B virus/treponema pallidum (HBV/TP) co-infection.

Methods

The clinical data of 79 patients with HBV/TP co-infection admitted to our hospital from January 2019 to January 2020 were retrospectively analyzed. These patients were divided into two groups according to the different HBeAg statuses before the treatment: 41 HBeAg+ patients were included in the HBeAg+ group, while 38 HBeAg- patients were included in the HBeAg- group. The levels of HBV-DNA, T lymphocyte subsets represented by NK cells and cytokines associated with T cells in the peripheral blood (PB) of the patients were compared between both groups.

Results

The HBV-DNA levels in the HBeAg+ group were significantly higher than those in the HBeAg- group (P < 0.05). The levels of CD3⁺, CD4⁺, CD4⁺/CD8⁺ and natural killer (NK) cells in the HBeAg+ group were higher than those in the HBeAg- group (P < 0.05), while the levels of CD8⁺ cells were lower than those in the HBeAg- group (P < 0.05). Moreover, the levels of interferon-γ (IFN-γ), tumor necrosis factor (TNF-α), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-17 (IL-17), transforming growth factor-β (TGF-β) in the HBeAg+ group were all significantly higher than those in the HBeAg- group (P < 0.05), but there was no significant difference in the levels of interleukin-4 (IL-4) and interleukin-10 (IL-10) between the HBeAg+ group and the HBeAg- group (P > 0.05).

Conclusion

HBeAg+ can increase the HBV-DNA levels in the PB of patients with HBV/TP co-infection, in turn triggering the body to initiate cellular immunity, increasing the levels of T lymphocyte subsets, and promote the secretion of cytokines.

Transforming growth factor-β: An early predictor of a functional cure in chronic hepatitis B treated with interferon

BACKGROUND

The relationship between the serum transforming growth factor (TGF)-β level and HBsAg loss has not been clearly elaborated in patients with chronic hepatitis B (CHB).

METHODS

Two cohorts of patients with CHB were studied. Cohort A: A total of 207 hepatitis B e antigen (HBeAg)-negative CHB patients who finished ≥1 year nucleos(t)ide analogue monotherapy and sequentially received PEGylated interferon treatment for less than 96 weeks were included. Cohort B: Forty HBeAg-positive patients who initially received entecavir therapy for at least 96 weeks were included. Their viral markers and serum TGF-β levels were measured at different time points during therapy.

RESULTS

The levels of serum TGF-β and HBsAg (0-24 W) were significantly lower in the patients who had HBsAg< 0.05 IU/mL at 48 weeks than in patients who did not in cohort A. We got the same results when we further divided the patients into subgroups according to the initial HBsAg cut-off values (1000 IU/mL, 100 IU/mL, 50 IU/mL) in cohort A. However, HBeAg seroconversion did not lead to the downregulation of TGF-β levels. The levels of serum TGF-β were significantly correlated with HBsAg quantitation in cohort A (12-24 W) but not in cohort B (0-48 W). The levels of TGF-β at week 12 could be used as an early index to predict a functional cure (AUC=0.818) as well as the levels of HBsAg itself (AUC=0.882) in HBeAg-negative chronic hepatitis B patients treated with PEGylated interferon.

CONCLUSIONS

The levels of serum TGF-β were significantly associated with HBsAg loss but not with HBeAg seroconversion and could be used as an early index to predict a functional cure in CHB patients treated with PEGylated interferon.

Involvement of TIGIT in Natural Killer Cell Exhaustion and Immune Escape in Patients and Mouse Model With Liver Echinococcus multilocularis Infection

BACKGROUND AND AIMS

Alveolar echinococcosis (AE) is a lethal helminthic liver disease caused by persistent infection with Echinococcus multilocularis. Although more attention has been paid to the immunotolerance of T cells caused by E. multilocularis infection, the role of natural killer (NK) cell, a critical player in liver immunity, is seldom studied.

APPROACH AND RESULTS

Here, we observed that NK cells from the blood and closed liver tissue (CLT) of AE patients expressed a higher level of inhibitory receptor TIGIT and were functionally exhausted with a lower expression of granzyme B, perforin, interferon-gamma (IFN-γ), and TNF-α. Addition of anti-TIGIT (T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domain) monoclonal antibody into AE patients' peripheral blood mononuclear cell culture significantly enhanced the synthesis of IFN-γ and TNF-α by NK cells, indicating the reversion of exhausted NK cells by TIGIT blockade. In the mouse model of E. multilocularis infection, liver and splenic TIGIT⁺ NK cells progressively increased dependent of infection dosage and timing and were less activated and less degranulated with lower cytokine secretion. Furthermore, TIGIT deficiency or blockade in vivo inhibited liver metacestode growth, reduced liver injury, and increased the level of IFN-γ produced by liver NK cells. Interestingly, NK cells from mice with persistent chronic infection expressed a higher level of TIGIT compared to self-healing mice. To look further into the mechanisms, more regulatory CD56^bright and murine CD49a⁺ NK cells with higher TIGIT expression existed in livers of AE patients and mice infected with E. multilocularis, respectively. They coexpressed higher surface programmed death ligand 1 and secreted more IL-10, two strong inducers to mediate the functional exhaustion of NK cells.

CONCLUSIONS

Our results indicate that inhibitory receptor TIGIT is involved in NK cell exhaustion and immune escape from E. multilocularis infection.

Nucleic acid vaccines: A taboo broken and prospect for a hepatitis B virus cure

Although a prophylactic vaccine is available, hepatitis B virus (HBV) remains a major cause of liver-related morbidity and mortality. Current treatment options are improving clinical outcomes in chronic hepatitis B; however, true functional cure is currently the exception rather than the rule. Nucleic acid vaccines are among the emerging immunotherapies that aim to restore weakened immune function in chronically infected hosts. DNA vaccines in particular have shown promising results in vivo by reducing viral replication, breaking immune tolerance in a sustained manner, or even decimating the intranuclear covalently closed circular DNA reservoir, the hallmark of HBV treatment. Although DNA vaccines encoding surface antigens administered by conventional injection elicit HBV-specific T cell responses in humans, initial clinical trials failed to demonstrate additional therapeutic benefit when administered with nucleos(t)ide analogs. In an attempt to improve vaccine immunogenicity, several techniques have been used, including codon/promoter optimization, coadministration of cytokine adjuvants, plasmids engineered to express multiple HBV epitopes, or combinations with other immunomodulators. DNA vaccine delivery by electroporation is among the most efficient strategies to enhance the production of plasmid-derived antigens to stimulate a potent cellular and humoral anti-HBV response. Preliminary results suggest that DNA vaccination via electroporation efficiently invigorates both arms of adaptive immunity and suppresses serum HBV DNA. In contrast, the study of mRNA-based vaccines is limited to a few in vitro experiments in this area. Further studies are needed to clarify the prospects of nucleic acid vaccines for HBV cure.

Restoration of HBV-specific CD8+ T-cell responses by sequential low-dose IL-2 treatment in non-responder patients after IFN-α therapy

Patients with chronic hepatitis B (CHB) undergoing interferon (IFN)-α-based therapies often exhibit a poor HBeAg serological response. Thus, there is an unmet need for new therapies aimed at CHB. This study comprised two clinical trials, including 130 CHB patients, who were treatment-naïve; in the first, 92 patients were systematically analyzed ex vivo for interleukin-2 receptor (IL-2R) expression and inhibitory molecules expression after receiving Peg-IFN-α-2b therapy. In our second clinical trial, 38 non-responder patients, in whom IFN-α therapy had failed, were treated with or without low-dose IL-2 for 24 weeks. We then examined the hepatitis B virus (HBV)-specific CD8⁺ T-cell response and the clinical outcome, in these patients. Although the majority of the participants undergoing Peg-IFN-α-2b therapy were non-responders, we observed a decrease in CD25 expression on their CD4⁺ T cells, suggesting that IFN-α therapy may provide a rationale for sequential IL-2 treatment without increasing regulatory T cells (Tregs). Following sequential therapy with IL-2, we demonstrated that the non-responders experienced a decrease in the numbers of Tregs and programmed cell death protein 1 (PD-1) expression. In addition, sequential IL-2 administration rescued effective immune function, involving signal transducer and activator of transcription 1 (STAT1) activation. Importantly, IL-2 therapy significantly increased the frequency and function of HBV-specific CD8⁺ T cells, which translated into improved clinical outcomes, including HBeAg seroconversion, among the non-responder CHB patients. Our findings suggest that sequential IL-2 therapy shows efficacy in rescuing immune function in non-responder patients with refractory CHB.

Expression Regulation and Function of T-Bet in NK Cells

Natural killer (NK) cells are cytotoxic innate lymphocytes that play an important role in immune surveillance. The development, maturation and effector functions of NK cells are orchestrated by the T-box transcription factor T-bet, whose expression is induced by cytokines such as IFN-γ, IL-12, IL-15 and IL-21 through the respective cytokine receptors and downstream JAK/STATs or PI3K-AKT-mTORC1 signaling pathways. In this review, we aim to discuss the expression and regulation of T-bet in NK cells, the role of T-bet in mouse NK cell development, maturation, and function, as well as the role of T-bet in acute, chronic infection, inflammation, autoimmune diseases and tumors.