Hepatitis B virus persistence in mice reveals IL-21 and IL-33 as regulators of viral clearance

Hepatitis B virus surface antigen drives T cell immunity through non-canonical antigen presentation in mice

Hepatitis B virus (HBV) exclusively infects hepatocytes and produces large amounts of subviral particles containing its surface antigen (HBsAg). T cell immunity is crucial for controlling and clearing HBV infection. However, the intercellular processes underlying HBsAg presentation to T cells are incompletely understood. Here, using preclinical mouse models, we show that, following HBsAg expression, the intrahepatic Batf3+XCR1+CCR7- conventional dendritic cell subset cDC1 presents HBsAg by MHC-I cross-dressing, driving CD8+ T cell response. Meanwhile, upon HBsAg access to lymphoid tissues, B cells acquire HBsAg directly in the follicles of lymphoid tissues and initiate CD4+ T cell responses sequentially in the follicular and interfollicular regions, guided by chemoattractant receptors CCR5 and EBI2, respectively. Finally, we identify ALCAM, LFA-1, and CD80 as key co-stimulatory signals essential for optimal T cell responses. Thus, these findings reveal the roadmap of non-canonical antigen presentation that drives T cell immunity against HBsAg, advancing novel therapeutic strategies for chronic HBV infection.

Transfection of unmodified oligodeoxynucleotide with polyethylenimine reduces the level of hepatitis B surface antigen

Introduction

The delivery of nucleic acid into cells using polyethylenimine (PEI) as non-viral carrier is a potential candidate technique for the treatment of hepatitis B virus (HBV) infection.

Methods

In the present study, PEI was used as cationic polymers and transfected with unmodified oligodeoxynucleotides in cell cultures and the BALB/c mouse model to investigate its efficiency in blocking HBV surface antigen (HBsAg) secretion.

Results and discussion

PEI/oligonucleotide complexes selectively inhibited HBsAg secretion in the culture supernatant, while there were no evident alterations in HBeAg and HBV DNA levels, thereby suggesting its potential inhibitory activity against the production of HBsAg. The complexes formed by PEI with double-stranded decoy oligonucleotides also suppressed HBsAg secretion but showed no expected interference with the intermediate levels of HBV transcription or replication. Furthermore, PEI/plasmid-DNA complexes demonstrated no influence on the expression levels of HBsAg, thus highlighting the specific effects of PEI/oligonucleotides exerted on HBsAg release. PEI-oligonucleotides transfection prior to the viral inoculation impaired HBV infection in HepG2-NCTP cells. Importantly, the PEI/oligonucleotide complex also induced the decline of HBsAg in hydrodynamically injected BALB/c mice. These findings demonstrate that transfection of PEI/oligonucleotide complexes can help effectively reduce HBsAg level and may offer a new potential avenue for the development of anti-HBV treatment.

Potential role of liver-resident CD3+ macrophages in HBV clearance in a mouse hepatitis B model

Background & Aims

Chronic HBV infection usually causes cirrhosis and hepatocellular carcinoma. Comparative investigations of acute and chronic HBV cases would help determine the immune responses crucial for viral clearance.

Methods

A fast-cleared HBV mouse model was established in Alb-Cre mice via hydrodynamic injection of HBV plasmid, while persistent HBV model mice were generated via recombinant covalently closed circular DNA-adeno-associated virus 8 infection. The single-cell transcriptomes of CD45+ intrahepatic non-parenchymal cells from these mice were conducted. Multiplexed immunohistochemistry and flow cytometry were used to confirm the findings from single-cell transcriptomes. Transwell, coculture, and adoptive transfer experiments were performed to study the generation and functions of macrophages.

Results

Twenty-four clusters of immune cells were identified. Myeloid cells, including granulocytes, monocytes, and dendritic cells, are activated early in HBV fast-cleared mice. Significantly, a cluster of CD3+ macrophages was found in the viral clearance phase, which was confirmed in liver tissue from five acute patients with HBV. These cells highly expressed CXCL1, tumor necrosis factor alpha, and HBsAg-specific T cell receptors. The transwell assay revealed that CD3+ macrophages originate from macrophages (n = 6). T cells and anti-HBsAg antibodies are indispensable for their differentiation, which was further confirmed in T- and/or B-cell-deficient mice. Interestingly, these CD3+ macrophages capable of killing peptide-loaded hepatocytes and engulfing IgG-coated beads were persistently detectable in the mouse liver for 10 weeks after HBV clearance. The expression levels of CD5L and Bcl2, two classical antiapoptotic proteins, increased (p <0.001), suggesting that the CD3+ macrophages are long-term resident populations. Finally, adoptive transfer of CD3+ macrophages accelerated HBV clearance in mice (n = 5, p <0.01).

Conclusions

We identified long-term polyfunctional CD3+ macrophages residing in HBV fast-cleared livers that could help elucidate the immune responses involved in eliminating HBV.

Impact and implications

The liver is a special organ with unique immune characteristics and tolerance to foodborne antigens. Chronic infections can develop in newborns after exposure to HBV; however, acute infections usually occur in adults, indicating that immune cells in the liver tissue microenvironment can also effectively fight against the virus. Nevertheless, the mechanisms involved in acute HBV infection have rarely been studied. In this study, we identified a macrophage population with both T cell and macrophage characteristics in the livers of acute HBV model mice and revealed that these macrophages play important roles in HBV clearance. Moreover, we confirmed that this population is derived from macrophages in the presence of virus-specific T cells and antibodies. This finding highlights the complexity of antiviral immune responses in liver microenvironments.

Homeobox protein MSX-1 restricts hepatitis B virus by promoting ubiquitin-independent proteasomal degradation of HBx protein

Hepatitis B virus (HBV) X protein (HBx) is a key factor for regulating viral transcription and replication. We recently characterized homeobox protein MSX-1 (MSX1) as a host restriction factor that inhibits HBV gene expression and genome replication by directly binding to HBV enhancer II/core promoter (EnII/Cp) and suppressing its promoter and enhancer activities. Notably, HBx expression was observed to be repressed more drastically by MSX1 compared to other viral antigens. In this work, we report that in addition to transcriptional repression, MSX1 also post-transcriptionally downregulates HBx protein stability. Mechanistically, MSX1 induces ubiquitin-independent proteasomal degradation of HBx, which is mediated through HBx C-terminal domain. Furthermore, this effect on HBx degradation correlates with MSX1-induced upregulation of DNAJA4 and CRYAB expression. Similar to MSX1, both DNAJA4 and CRYAB promote HBx degradation and repress HBV gene expression and genome replication. In chronic hepatitis B (CHB) patients, immune active phase (IA) is associated with higher intrahepatic expression of MSX1, DNAJA4 and CRYAB, and lower serum HBV markers compared to immune tolerant (IT) phase. Finally, HBV infection is significantly suppressed by MSX1 overexpression in both NTCP-overexpressing cell and humanized liver mouse models. These results demonstrate additional and novel mechanisms of MSX1-mediated repression of HBV, and establish MSX1 as a multi-functional HBV restriction factor with therapeutic potential.

Identification and characterization of host factor VCPIP1 as a multi-functional positive regulator of hepatitis B virus

Chronic infection with hepatitis B virus (HBV) remains an important public health challenge. Viral covalently closed circular DNA (cccDNA) persists in infected hepatocytes and serves as the template for transcribing all viral RNA species. HBV regulatory protein X (HBx) interacts with other viral and cellular proteins to play diverse functions in viral life cycle, including modulation of cccDNA transcription activity. Here, we used proximity labeling coupled with proteomic analysis to screen for HBx-interacting host proteins. One of the identified candidates, deubiquitinating enzyme valosin-containing protein-interacting protein 1 (VCPIP1), directly binds HBx and stabilizes HBx by reducing its proteasomal degradation, which corroborated a recent report. VCPIP1-mediated upregulation of HBV transcription, antigen expression, and genome replication was demonstrated using a series of HBV replication and infection models. More importantly, VCPIP1 was found to upregulate HBV in the absence of HBx. Mechanistic studies revealed that VCPIP1 HBx-independently associates with HBV enhancer I/X promoter (EnI/Xp) and positively modulates both its promoter and enhancer activities, partially through promoting the binding of YY1 transcription factor to EnI/Xp. Results presented here expand the recently described role of VCPIP1 in HBV life cycle and establish it as a multi-functional positive regulator of this virus.

IMPORTANCE

Hepatitis B virus (HBV) encodes the regulatory protein HBx that plays crucial roles in viral life cycle and cellular processes through interacting with viral and cellular proteins. Identifying HBx-interacting proteins may reveal novel aspects of host-virus interactions. In this work, proximity labeling coupled with proteomic analysis identified multiple HBx-interacting host factors, and among these, valosin-containing protein-interacting protein 1 (VCPIP1) was confirmed to directly bind HBx and reduce its proteasomal degradation, corroborating a recent report. In addition to upregulating HBx-expressing HBV, we showed that VCPIP1 also positively regulates mutant HBV lacking HBx expression. This novel HBx-independent function of VCPIP1 was shown to involve its association with one viral promoter/enhancer element, which upregulated the latter's promoter and enhancer activities. These results establish VCPIP1 as a positive regulator of HBV that acts through multiple, diverse mechanisms and might also contribute toward revealing novel cellular functions of VCPIP1.

Liver mechanosignaling as a natural anti-hepatitis B virus mechanism

The mechanisms underlying the natural control of hepatitis B virus (HBV) infection have long been an intriguing question. Given the wide physiological range of liver stiffness and the growing attention to the role of mechanical microenvironment in homeostasis and diseases, we investigated how physical matrix cues impact HBV replication. High matrix stiffness significantly inhibited HBV replication and activated YAP in primary hepatocyte culture system, a key molecule in mechanosignaling. YAP activation notably suppressed HBV transcription and antigen expression. Several YAP-induced genes exhibited strong anti-HBV effects. Single-cell analysis of liver tissue from male individuals with active HBV replication revealed a strong significant negative correlation between YAP signature activation and HBV transcript levels. Intraperitoneal administration of YAP small molecule agonist potently controls HBV in male mouse models. These findings unveil a mechanism that involves the mechanical environment of hepatocytes and YAP to clear hepatotropic viral infection in the liver, providing new perspectives for HBV cure studies and antiviral development.

Hepatitis B virus core protein as a Rab-GAP suppressor driving liver disease progression

Chronic hepatitis B virus (HBV) infection can lead to advanced liver pathology. Here, we establish a transgenic murine model expressing a basic core promoter (BCP)-mutated HBV genome. Unlike previous studies on the wild-type virus, the BCP-mutated HBV transgenic mice manifest chronic liver injury that culminates in cirrhosis and tumor development with age. Notably, agonistic anti-Fas treatment induces fulminant hepatitis in these mice even at a negligible dose. As the BCP mutant exhibits a striking increase in HBV core protein (HBc) expression, we posit that HBc is actively involved in hepatocellular injury. Accordingly, HBc interferes with Fis1-stimulated mitochondrial recruitment of Tre-2/Bub2/Cdc16 domain family member 15 (TBC1D15). HBc may also inhibit multiple Rab GTPase-activating proteins, including Rab7-specific TBC1D15 and TBC1D5, by binding to their conserved catalytic domain. In cells under mitochondrial stress, HBc thus perturbs mitochondrial dynamics and prevents the recycling of damaged mitochondria. Moreover, sustained HBc expression causes lysosomal consumption via Rab7 hyperactivation, which further hampers late-stage autophagy and substantially increases apoptotic cell death. Finally, we show that adenovirally expressed HBc in a mouse model is directly cytopathic and causes profound liver injury, independent of antigen-specific immune clearance. These findings reveal an unexpected cytopathic role of HBc, making it a pivotal target for HBV-associated liver disease treatment. The BCP-mutated HBV transgenic mice also provide a valuable model for understanding chronic hepatitis B progression and for the assessment of therapeutic strategies.

Association between autoimmune liver diseases and chronic hepatitis B: A multivariable Mendelian randomization study in European population

BACKGROUND

Observational studies have indicated a link between autoimmune liver diseases (AILD) and chronic hepatitis B (CHB) through observational studies. The association between AILD and CHB remains indeterminate.

METHODS

A two-sample Mendelian randomization (MR) analysis was conducted to scrutinize the causal nexus between AILD and CHB utilizing summary statistics derived from extensive genome-wide association studies (GWASs) in European populations. The primary statistical methodology employed was the inverse variance-weighted (IVW) method to deduce the causal connection of AILD on CHB. This study incorporated primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and autoimmune hepatitis (AIH) as subtypes of AILD. Additionally, we conducted a multivariable MR (MVMR) analysis to account for the potential confounding effects of smoking, alcohol consumption, body mass index (BMI), and some autoimmune diseases.

RESULTS

Our MR investigation encompassed a cohort of 725,816 individuals. The MR analysis revealed that genetically predicted PSC significantly correlated with a reduced risk of CHB (IVW OR = 0.857; 95%CI: 0.770-0.953, P = 0.005). Conversely, the reverse MR analysis suggested that genetic susceptibility to PSC might not modify the risk of CHB (IVW OR = 1.004; 95% CI: 0.958-1.053, P = 0.866). Genetically proxied PBC and AIH exhibited no discernible causal association with CHB in the MR analysis using the IVW method (P = 0.583; P = 0.425). The MVMR analysis still indicated a decreased risk of CHB associated with PSC (OR = 0.853, P = 0.003).

CONCLUSION

Our study elucidates a causal relationship between PSC and a diminished risk of CHB.

Intrahepatic homeobox protein MSX-1 is a novel host restriction factor of hepatitis B virus

Chronic hepatitis B virus (HBV) infection (CHB) is a risk factor for the development of liver fibrosis, cirrhosis, and hepatocellular carcinoma. Covalently closed circular DNA serves as the sole transcription template for all viral RNAs and viral transcription is driven and enhanced by viral promoter and enhancer elements, respectively. Interactions between transcription factors and these cis-elements regulate their activities and change the production levels of viral RNAs. Here, we report the identification of homeobox protein MSX-1 (MSX1) as a novel host restriction factor of HBV in liver. In both HBV-transfected and HBV-infected cells, MSX1 suppresses viral gene expression and genome replication. Mechanistically, MSX1 downregulates enhancer II/core promoter (EnII/Cp) activity via direct binding to an MSX1 responsive element within EnII/Cp, and such binding competes with hepatocyte nuclear factor 4α binding to EnII/Cp due to partial overlap between their respective binding sites. Furthermore, CHB patients in immune active phase express higher levels of intrahepatic MSX1 but relatively lower levels of serum and intrahepatic HBV markers compared to those in immune tolerant phase. Finally, MSX1 was demonstrated to induce viral clearance in two mouse models of HBV persistence, suggesting possible therapeutic potential for CHB.IMPORTANCECovalently closed circular DNA plays a key role for the persistence of hepatitis B virus (HBV) since it serves as the template for viral transcription. Identification of transcription factors that regulate HBV transcription not only provides insights into molecular mechanisms of viral life cycle regulation but may also provide potential antiviral targets. In this work, we identified host MSX1 as a novel restriction factor of HBV transcription. Meanwhile, we observed higher intrahepatic MSX1 expression in chronic hepatitis B virus (CHB) patients in immune active phase compared to those in immune tolerant phase, suggesting possible involvement of MSX1 in the regulation of HBV activity by the host. Lastly, intrahepatic overexpression of MSX1 delivered by recombinant adenoviruses into two mouse models of HBV persistence demonstrated MSX1-mediated repression of HBV in vivo, and MSX1-induced clearance of intrahepatic HBV DNA in treated mice suggested its potential as a therapeutic target for the treatment of CHB.

High-pressure Hydrodynamic Injection as a Method of Establishing Hepatitis B Virus Infection in Mice

Among several existing mouse models for hepatitis B virus (HBV) infection, the high-pressure hydrodynamic injection (HDI) method is frequently used in HBV research due to its economic advantages and ease of implementation. The use of the HDI method is influenced by factors such as mouse genetic background, age, sex, and the type of HBV plasmid used. This overview provides a multidimensional analysis and comparison of various factors that influence the effectiveness of the HBV mouse model established through HDI. The goal is to provide a summary of information for researchers who create HBV models in mice.

The Role of Interleukins in HBV Infection: A Narrative Review

Hepatitis B virus (HBV) infection is a worldwide medical issue with significant morbidity and mortality, as it is the main cause of chronic liver disease and hepatocellular carcinoma (HCC). Both innate and adaptive immune responses play a key role in HBV replication and suppression. Recently, the pathophysiological function of interleukins (IL) in the natural course of HBV has gained much attention as a result of the broad use of anti-interleukin agents for a variety of autoimmune diseases and the accompanying risk of HBV reactivation. We present a narrative review regarding the role of IL in HBV infection. Collectively, the pro-inflammatory ILs, namely IL-1, IL-5, IL-6, IL-12 and IL-21, seem to play a critical role in the suppression of HBV replication. In contrast, the anti-inflammatory cytokines IL-10, IL-23 and IL-35 probably act as HBV replication enhancers, while IL-17 has been correlated with HBV-related liver injury. Interestingly enough, IL-2, IL-4 and IL-12 have been tried as therapeutic options against HBV infection with contradictory results. Lastly, the role of IL-22 remains largely ill defined, although preliminary data suggest that it may play a significant role in HBV replication, proliferation and subsequent liver damage.

IL-21 collaborates with anti-TIGIT to restore NK cell function in chronic HBV infection

Available therapies for chronic hepatitis B virus (HBV) infection are not satisfying, and interleukin-21 (IL-21) and checkpoint inhibitors are potential therapeutic options. However, the mechanism underlying IL-21 and checkpoint inhibitors in treating chronic HBV infection is unclear. To explore whether IL-21 and checkpoint inhibitors promote HBV clearance by modulating the function of natural killer (NK) cells, we measured the phenotypes and functions of NK cells in chronic HBV-infected patients and healthy controls on mRNA and protein levels. We found that chronic HBV infection disturbed the transcriptome of NK cells, including decreased expression of KLRK1, TIGIT, GZMA, PRF1, and increased expression of CD69. We also observed altered phenotypes and functions of NK cells in chronic HBV-infected patients, characterized by decreased NKG2D expression, increased TIGIT expression and impaired interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α) production. Furthermore, these alterations cannot be restored by telbivudine treatment but can be partially restored by IL-21 and anti-TIGIT stimulation. IL-21 upregulated the expression of activating receptor CD16, CD69, and NKG2D on NK cells, enhanced IFN-γ production, cytolysis, and proliferation of NK cells, while anti-TIGIT promoted IFN-γ production in CD56dim subset exclusively in chronic HBV infected patients. Additionally, IL-21 was indispensable for anti-TIGIT in HBsAg clearance in mice bearing HBV. It enhanced IFN-γ production in splenic NK cells rather than intrahepatic NK cells, indicating a brand-new mechanism of IL-21 in HBV clearance when combined with anti-TIGIT. Overall, our findings contribute to the design of immunotherapy through enhancing the antiviral efficacy of NK cells in chronic HBV infection.

Host and HBV Interactions and Their Potential Impact on Clinical Outcomes

Hepatitis B virus (HBV) is a challenge for global health services, affecting millions and leading thousands to end-stage liver disease each year. This comprehensive review explores the interactions between HBV and the host, examining their impact on clinical outcomes. HBV infection encompasses a spectrum of severity, ranging from acute hepatitis B to chronic hepatitis B, which can potentially progress to cirrhosis and hepatocellular carcinoma (HCC). Occult hepatitis B infection (OBI), characterized by low HBV DNA levels in hepatitis B surface antigen-negative individuals, can reactivate and cause acute hepatitis B. HBV genotyping has revealed unique geographical patterns and relationships with clinical outcomes. Moreover, single nucleotide polymorphisms (SNPs) within the human host genome have been linked to several clinical outcomes, including cirrhosis, HCC, OBI, hepatitis B reactivation, and spontaneous clearance. The immune response plays a key role in controlling HBV infection by eliminating infected cells and neutralizing HBV in the bloodstream. Furthermore, HBV can modulate host metabolic pathways involved in glucose and lipid metabolism and bile acid absorption, influencing disease progression. HBV clinical outcomes correlate with three levels of viral adaptation. In conclusion, the clinical outcomes of HBV infection could result from complex immune and metabolic interactions between the host and HBV. These outcomes can vary among populations and are influenced by HBV genotypes, host genetics, environmental factors, and lifestyle. Understanding the degrees of HBV adaptation is essential for developing region-specific control and prevention measures.

Lipid nanoparticle-mediated delivery of IL-21-encoding mRNA induces viral clearance in mouse models of hepatitis B virus persistence

Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA), the transcription template for all viral mRNAs, is highly stable and current treatment options cannot effectively induce its clearance. Previously, we established an HBV persistence mouse model based on a clinical isolate (termed BPS) and identified interleukin-21 (IL-21) as a potent inducer of HBV clearance. Lipid nanoparticle (LNP) mediated delivery of mRNA has proven to be a highly safe and effective delivery platform. This work explored the applicability and effectiveness of the mRNA-LNP platform in IL-21-based HBV therapies. First, LNP-encapsulated murine IL-21 mRNA (LNP-IL-21) was prepared, characterized, and demonstrated to engender IL-21 expression in vitro and in vivo. Next, LNP-IL-21 was shown to induce clearance of both serum and intrahepatic HBV antigen and DNA in two HBV persistence mouse models based on BPS and recombinant cccDNA (rcccDNA), respectively, which was associated with HBV-specific humoral and cellular immune responses. Furthermore, peripheral blood mononuclear cells from BPS persistence mice treated ex vivo with LNP-IL-21 and HBV surface antigen (HBsAg) could induce similar HBV clearance upon infusion into recipient mice. These findings indicated that IL-21 combined with mRNA-LNP platform represents a valid and promising strategy for developing novel therapeutics against chronic HBV infection.

Inhibition of HBV replication by EVA1A via enhancing cellular degradation of HBV components and its potential therapeutic application

Hepatitis B virus (HBV) DNA is much higher during HBeAg-positive chronic HBV infection (EP-CBI) than during HBeAg-negative chronic HBV infection (EN-CBI), although the necroinflammation in liver is minimal and the adaptive immune response is similar in both phases. We previously reported that mRNA levels of EVA1A were higher in EN-CBI patients. In this study, we aimed to investigate whether EVA1A inhibits HBV gene expression and examine the underlying mechanisms. The available cell models for HBV replication and model HBV mice were used to investigate how EVA1A regulates HBV replication and the antiviral activity based on gene therapy. The signaling pathway was determined through RNA sequencing analysis. The results demonstrated that EVA1A can inhibit HBV gene expression in vitro and in vivo. In particular, EVA1A overexpression resulted in accelerated HBV RNA degradation and activation of the PI3K-Akt-mTOR pathway, two processes that directly and indirectly inhibiting HBV gene expression. EVA1A is a promising candidate for treating chronic hepatitis B (CHB). In conclusion, EVA1A is a new host restriction factor that regulates the HBV life cycle via a nonimmune process.

HBx-Induced HSPA8 Stimulates HBV Replication and Suppresses Ferroptosis to Support Liver Cancer Progression

Hepatitis B virus (HBV) infection is a major driver of hepatocarcinogenesis. Ferroptosis is a type of iron-mediated cell death that can suppress liver transformation. Previous studies have linked HBV to ferroptosis in liver fibrosis and acute liver failure. However, whether ferroptosis is involved in HBV-mediated liver cancer is poorly understood. Here, we identified heat shock protein family A member 8 (HSPA8) as a crucial host factor that modulates HBV replication and ferroptosis in liver cancer. Hepatitis B X protein (HBx) upregulated HSPA8 by coactivating the transcription factor heat shock factor 1 (HSF1) in cells. HSPA8 enhanced HBV replication by recruiting hepatitis B core protein (HBc) to the HBV covalently closed circular DNA (cccDNA) minichromosome, forming a positive feedback loop. Moreover, HSPA8 suppressed ferroptosis in liver cancer cells by upregulating the expression of SLC7A11/GPX4 and decreasing erastin-mediated reactive oxygen species and Fe2+ accumulation in cells in vitro and in vivo. Inhibition of HSPA8 reduced the growth of HBV-positive liver tumors and increased sensitivity to erastin. In conclusion, HBx-elevated HSPA8 regulates both HBV replication and ferroptosis in liver cancer. Targeting HSPA8 could be a promising strategy for controlling HBV and hepatocarcinogenesis.

SIGNIFICANCE

HBV-induced upregulation of HSPA8 promotes hepatocarcinogenesis by suppressing ferroptosis and stimulating HBV replication, identifying HSPA8 as a potential therapeutic target in liver cancer.

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.

IFNα subtype-specific susceptibility of HBV in the course of chronic infection

Chronic hepatitis B virus (HBV) infection continues to be a major health problem worldwide and remains hard to be cured. Therapy with interferon (IFN) α is an important method for the clinical treatment of chronic hepatitis B. IFNα exhibits direct antiviral effects as well as immunomodulatory activities, which can induce sustained antiviral responses in part of the treated chronic hepatitis B patients. Numerous IFNα subtypes with high sequence identity between 76-96% exist which are characterized by diverse, non-redundant biological activities. Our previous studies have demonstrated that the clinically approved IFNα2 is not the most effective subtype for the anti-HBV treatment among all IFNα subtypes. So far very little is known about the IFNα subtype expression pattern during early HBV infection and the IFNα subtype-specific susceptibility during persistent HBV infection as well as its related cellular mechanism. Here we determined the Ifna subtype mRNA expression during acute and chronic HBV infection by using the well-established hydrodynamic injection (HDI) mouse model and we revealed a transient but strong expression of a panel of Ifna subtypes in the spleen of HBV persistent replication mice compared to HDI controls. Immunotherapy with distinct IFNα subtypes controlled chronic HBV infection. IFNα subtype-mediated antiviral response and immune activation were comprehensively analyzed in an AAV-HBV persistent infection murine model and murine IFNα2 was identified as the most effective subtype in suppression of HBV replication. Further analysis of the immune response revealed a strong immunomodulatory activity of murine IFNα2 on splenic and intrahepatic NK and T cell activation during persistent HBV infection. Taken together, our data provide IFNα subtype-specific differences in the antiviral and immunomodulatory effector responses and a strong expression of all IFNα subtypes in the spleen during persistent HBV infection in mice. This knowledge will support the development of novel immunotherapeutic strategies for chronic hepatitis B infection.

Establishment and Characterization of a New Cell Culture System for Hepatitis B Virus Replication and Infection

Hepatitis B virus (HBV) is a primary cause of chronic liver diseases in humans. HBV infection exhibits strict host and tissue tropism. HBV core promoter (Cp) drives transcription of pregenomic RNA (pgRNA) and plays a key role in the viral life cycle. Hepatocyte nuclear factor 4α (HNF4α) acts as a major transcriptional factor that stimulates Cp. In this work, we reported that BEL7404 ​cell line displayed a high efficiency of DNA transfection and high levels of HBV antigen expression after transfection of HBV replicons without prominent viral replication. The introduction of exogenous HNF4α and human sodium taurocholate cotransporting polypeptide (hNTCP) expression into BEL7404 made it permissive for HBV replication and susceptible to HBV infection. BEL7404-derived cell lines with induced HBV permissiveness and susceptibility were constructed by stable co-transfection of hNTCP and Tet-inducible HNF4α followed by limiting dilution cloning. HBV replication in such cells was sensitive to inhibition by nucleotide analog tenofovir, while the infection was inhibited by HBV entry inhibitors. This cell culture system provides a new and additional tool for the study of HBV replication and infection as well as the characterization of antiviral agents.

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BEL7404 ​cells are characterized by a high transfection efficiency, but do not support canonical HBV replication.

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BEL7404 ​cells lack endogenous HNF4α expression, and exogenous HNF4α rescues canonical HBV replication.

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BEL7404 ​cells with stable hNTCP and inducible HNF4α expression support HBV infection and inducible replication.

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BEL7404-derived cell lines supporting HBV infection retain high transfection efficiencies and allow testing of antivirals.

Hepatitis B Virus-Specific Cellular Immunity Contributes to the Outcome of Occult Hepatitis B Virus Infection

There is little known of immunologic factors leading to the occurrence of occult HBV infection (OBI). Specific cellular immune response to hepatitis B virus (HBV) core/pol peptides was compared between blood donor populations, including 37 OBIs, 53 chronic HBV infections (CHB), 47 resolved infections, and 56 non-infected controls, respectively. The rate of CD4⁺/CD8⁺ T cell proliferation in OBI or CHB carriers was higher than in HBV resolved and non-infected individuals (P < 0.05). The intensity of IFN-γ-secretion T-cell response of OBI carriers was highest, followed by CHB and resolved infections, and non-infected individuals (P < 0.05). The frequency of intracellular IFN-γ and IL-17A CD4⁺/CD8⁺ and IL-21 CD4⁺ T-cell responses was significantly higher in resolved infections than in OBI or CHB carriers (P < 0.05), while the level of extracellular IL-17A of peripheral blood mononuclear cells (PBMCs) was higher in OBI and CHB carriers than in resolved infections (P < 0.01). The frequency of intracellular IL-10 CD4⁺ T-cell response in CHB, OBI, and resolved infections was higher than in HBV non-infected individuals (P < 0.01). Intracellular IL-10 CD8⁺ T cell and extracellular IL-10 T-cell responses were higher in CHB than in OBI (P = 0.012) or HBV resolved infections (P < 0.01). In conclusion, the higher level of effective T-cell response with IFN-γ, IL-17A, and IL-21 contributes to resolved infection outcome, while higher levels of suppressive T-cell response with IL-10 result in HBV chronicity. OBI is an intermediary status between HBV resolved and chronic infections, in which IL-21 effector and IL-10 suppressor T-cell responses play an important role in directing the outcome of HBV infection.

Monocytic MDSCs homing to thymus contribute to age-related CD8+ T cell tolerance of HBV

Hepatitis B virus exposure in children usually develops into chronic hepatitis B (CHB). Although hepatitis B surface antigen (HBsAg)–specific CD8⁺ T cells contribute to resolve HBV infection, they are preferentially undetected in CHB patients. Moreover, the mechanism for this rarely detected HBsAg-specific CD8⁺ T cells remains unexplored. We herein found that the frequency of HBsAg-specific CD8⁺ T cells was inversely correlated with expansion of monocytic myeloid-derived suppressor cells (mMDSCs) in young rather than in adult CHB patients, and CCR9 was upregulated by HBsAg on mMDSCs via activation of ERK1/2 and IL-6. Sequentially, the interaction between CCL25 and CCR9 mediated thymic homing of mMDSCs, which caused the cross-presentation, transferring of peripheral HBsAg into the thymic medulla, and then promoted death of HBsAg-specific CD8⁺ thymocytes. In mice, adoptive transfer of mMDSCs selectively obliterated HBsAg-specific CD8⁺ T cells and facilitated persistence of HBV in a CCR9-dependent manner. Taken together, our results uncovered a novel mechanism for establishing specific CD8⁺ tolerance to HBsAg in chronic HBV infection.

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.

High mobility group AT-hook 1 (HMGA1) is an important positive regulator of hepatitis B virus (HBV) that is reciprocally upregulated by HBV X protein

Chronic infection with hepatitis B virus (HBV) is associated with liver cirrhosis and hepatocellular carcinoma. Upon infection of hepatocytes, HBV covalently closed circular DNA (cccDNA) exists as histone-bound mini-chromosome, subjected to transcriptional regulation similar to chromosomal DNA. Here we identify high mobility group AT-hook 1 (HMGA1) protein as a positive regulator of HBV transcription that binds to a conserved ATTGG site within enhancer II/core promoter (EII/Cp) and recruits transcription factors FOXO3α and PGC1α. HMGA1-mediated upregulation of EII/Cp results in enhanced viral gene expression and genome replication. Notably, expression of endogenous HMGA1 was also demonstrated to be upregulated by HBV, which involves HBV X protein (HBx) interacting with SP1 transcription factor to activate HMGA1 promoter. Consistent with these in vitro results, chronic hepatitis B patients in immune tolerant phase display both higher intrahepatic HMGA1 protein levels and higher serum HBV markers compared to patients in inactive carrier phase. Finally, using a mouse model of HBV persistence, we show that targeting endogenous HMGA1 through RNA interference facilitated HBV clearance. These data establish HMGA1 as an important positive regulator of HBV that is reciprocally upregulated by HBV via HBx and also suggest the HMGA1-HBV positive feedback loop as a potential therapeutic target.

In Vivo Mouse Models for Hepatitis B Virus Infection and Their Application

Despite the availability of effective vaccination, hepatitis B virus (HBV) infection continues to be a major challenge worldwide. Research efforts are ongoing to find an effective cure for the estimated 250 million people chronically infected by HBV in recent years. The exceptionally limited host spectrum of HBV has limited the research progress. Thus, different HBV mouse models have been developed and used for studies on infection, immune responses, pathogenesis, and antiviral therapies. However, these mouse models have great limitations as no spread of HBV infection occurs in the mouse liver and no or only very mild hepatitis is present. Thus, the suitability of these mouse models for a given issue and the interpretation of the results need to be critically assessed. This review summarizes the currently available mouse models for HBV research, including hydrodynamic injection, viral vector-mediated transfection, recombinant covalently closed circular DNA (rc-cccDNA), transgenic, and liver humanized mouse models. We systematically discuss the characteristics of each model, with the main focus on hydrodynamic injection mouse model. The usefulness and limitations of each mouse model are discussed based on the published studies. This review summarizes the facts for considerations of the use and suitability of mouse model in future HBV studies.

Hepatitis B virus middle surface antigen loss promotes clinical variant persistence in mouse models

Hepatitis B virus (HBV) middle surface antigen (MHBs) mutation or deletion occurs in patients with chronic HBV infection. However, the functional role of MHBs in HBV infection is still an enigma. Here, we reported that 7.33% (11/150) isolates of CHB patients had MHBs start codon mutations compared with 0.00% (0/146) in acute hepatitis B (AHB) patients. Interestingly, MHBs loss accounted for 11.88% (126/1061) isolates from NCBI GenBank, compared with 0.09% (1/1061) and 0.00% (0/1061) for HBV large surface antigen (LHBs) loss and HBV small surface antigen (SHBs) loss, respectively. One persistent HBV clone of genotype B (B56, MHBs loss) from a CHB patient was hydrodynamically injected into BALB/c mice. B56 persisted for >70 weeks in BALB/c mice, whereas B56 with restored MHBs (B56^M+) was quickly cleared within 28 days. Serum cytokine assays demonstrated that CXCL1, CXCL2, IL-6 and IL-33 were significantly increased during rapid HBV clearance in B56^M+ mice. Furthermore, the enhancers and promoters of B56 were proved to be required for B56 persistence in mice. Ablating MHBs expression improved the persistence of a new clone (HBV1.3, genotype B) which was recreated by using enhancers and promoters of B56. These data demonstrated that MHBs deletion can promote the persistence of specific HBV variants in a hydrodynamic mouse model. MHBs re-expression restored a rapid clearance of HBV, which was accompanied by cytokine responses including the elevation of CXCL1, CXCL2, IL-6 and IL-33.

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells-in particular, follicular helper T (Tfh) cells-which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.

Reduced pannexin 1-IL-33 axis function in donor livers increases risk of MRSA infection in liver transplant recipients

Liver transplantation patients are at increased risk for methicillin-resistant Staphylococcus aureus (MRSA) infection, but the molecular mechanism remains unclear. We found that genetic predisposition to low pannexin 1 (PANX1) expression in donor livers was associated with MRSA infection in human liver transplantation recipients. Using Panx1 and Il-33-knockout mice for liver transplantation models with MRSA tail vein injection, we demonstrated that Panx1 deficiency increased MRSA-induced liver injury and animal death. We found that decreased PANX1 expression in the liver led to reduced release of adenosine triphosphate (ATP) from hepatocytes, which further reduced the activation of P2X2, an ATP-activating P2X receptor. Reduced P2X2 function further decreased the NLRP3-mediated release of interleukin-33 (IL-33), reducing hepatic recruitment of macrophages and neutrophils. Administration of mouse IL-33 to Panx1^-/- mice significantly (P = 0.011) ameliorated MRSA infection and animal death. Reduced human hepatic IL-33 protein abundance also associated with increased predisposition to MRSA infection. Our findings reveal that genetic predisposition to reduced PANX1 function increases risk for MRSA infection after liver transplantation by decreasing hepatic host innate immune defense, which can be attenuated by IL-33 treatment.

Epigenetic Regulation of Cannabinoid-Mediated Attenuation of Inflammation and Its Impact on the Use of Cannabinoids to Treat Autoimmune Diseases

Chronic inflammation is considered to be a silent killer because it is the underlying cause of a wide range of clinical disorders, from cardiovascular to neurological diseases, and from cancer to obesity. In addition, there are over 80 different types of debilitating autoimmune diseases for which there are no cure. Currently, the drugs that are available to suppress chronic inflammation are either ineffective or overtly suppress the inflammation, thereby causing increased susceptibility to infections and cancer. Thus, the development of a new class of drugs that can suppress chronic inflammation is imperative. Cannabinoids are a group of compounds produced in the body (endocannabinoids) or found in cannabis (phytocannabinoids) that act through cannabinoid receptors and various other receptors expressed widely in the brain and immune system. In the last decade, cannabinoids have been well established experimentally to mediate anti-inflammatory properties. Research has shown that they suppress inflammation through multiple pathways, including apoptosis and inducing immunosuppressive T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Interestingly, cannabinoids also mediate epigenetic alterations in genes that regulate inflammation. In the current review, we highlight how the epigenetic modulations caused by cannabinoids lead to the suppression of inflammation and help identify novel pathways that can be used to target autoimmune diseases.

Animal Models of Hepatitis B Virus Infection-Success, Challenges, and Future Directions

Chronic hepatitis B virus (HBV) infection affects more than 250 million people worldwide, which greatly increases the risk for terminal liver diseases, such as liver cirrhosis and hepatocellular carcinoma (HCC). Even though current approved antiviral therapies, including pegylated type I interferon (IFN) and nucleos(t)ide analogs, can effectively suppress viremia, HBV infection is rarely cured. Since HBV exhibits a narrow species tropism and robustly infects only humans and higher primates, progress in HBV research and preclinical testing of antiviral drugs has been hampered by the scarcity of suitable animal models. Fortunately, a series of surrogate animal models have been developed for the study of HBV. An increased understanding of the barriers towards interspecies transmission has aided in the development of human chimeric mice and has greatly paved the way for HBV research in vivo, and for evaluating potential therapies of chronic hepatitis B. In this review, we summarize the currently available animal models for research of HBV and HBV-related hepadnaviruses, and we discuss challenges and future directions for improvement.

Prior transient exposure to interleukin-21 delivered by recombinant adeno-associated virus vector protects mice from hepatitis B virus persistence

Chronic infection of hepatitis B virus (HBV) is a high risk factor for hepatic diseases, such as liver fibrosis, cirrhosis and hepatocellular carcinoma. Non-responders and hyporesponders to HBV vaccine are not protected from HBV infection. Patients that achieve autonomous or treatment-induced recovery are at risk of reactivation due to persistence of HBV covalently closed circular DNA (cccDNA) in hepatocytes. Interleukin 21 (IL-21) is a key regulator of HBV clearance in mouse models of HBV persistence: IL-21-based therapies effectively induces HBV clearance and protects mice from subsequent re-challenge. In this study, we explore the possibility of using IL-21 as prophylaxis against HBV by using mouse models of HBV persistence. HBV-naïve mice were transiently exposed to exogenous IL-21 through injection with recombinant adeno-associated virus expressing mouse IL-21 (AAV-IL-21). After extraneous IL-21 protein and DNA had become undetectable, mice were challenged with persistence-inducing HBV replicon plasmid through hydrodynamic injection. Viral persistence was analyzed by measuring viral antigens and DNA markers in serum and intrahepatic HBV DNA. For mechanistic studies, CD8⁺ T cell functions were blocked by repeated intraperitoneal injections of CD8 monoclonal antibodies in HBV-challenged mice. AAV-IL-21-injected mice quickly cleared HBV after HBV replicon challenge. In contrast, untreated mice and mice injected with control virus (AAV-Ctrl) allowed establishment of HBV persistence. Mechanistically, mice with prior IL-21 exposure displayed marked intrahepatic CD8⁺ T cell infiltrations, and CD8 blocking experiments demonstrated that CD8⁺ T cell responses functionally contributed toward clearance.

IL-33 ameliorates liver injury and inflammation in Poly I:C and Concanavalin-A induced acute hepatitis

The IL-33/ST2 axis is known to be involved in liver pathologies and IL-33 is over-expressed in mouse hepatitis models. We aimed to investigate the proposed protective effect of IL-33 in murine fulminant hepatitis induced by a Toll like receptor 3 (TLR3) viral mimetic, Poly I:C or by Concanavalin-A (ConA). The Balb/C mice were administered intravenously with ConA (15 mg/kg) or Poly I:C (30 μg/mouse) to induce acute hepatitis along with vehicle control. The recombinant mouse IL-33 (rIL-33) was injected (0.2 μg/mouse) to mice 2 h prior to ConA or Poly I:C injection to check its hepato-protective effects. The gross lesions, level of serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), histopathology (H&E staining) and levels of IFNγ and TNFα were measured by ELISA. The gross pathological liver injury induced by Poly I:C or ConA was reduced by rIL-33 administration in mice. The levels of AST and ALT were significantly (P ≤ 0.05) higher in mice challenged with Poly I:C or ConA in comparison to control mice. The rIL-33 pre-treated mice in both Poly I:C and ConA challenge groups showed significantly (P ≤ 0.05) lower levels of AST and ALT, and decreased liver injury (parenchymal and per-vascular necrotic areas) in histological liver sections. The soluble levels of TNFα and IFNγ were significantly (P ≤ 0.05) raised in Poly I:C or ConA challenged mice than control mice. The levels of TNFα and IFNγ were significantly reduced (P ≤ 0.05) in rIL-33 pre-treated mice. In conclusion, the exogenous IL-33 administration mitigated liver injury and inflammation (decreased levels of IFNγ and TNFα) in Poly I:C and ConA-induced acute hepatitis in mice.

IL-33 Inhibits Hepatitis B Virus through Its Receptor ST2 in Hydrodynamic HBV Mouse Model

Interleukin-33 has been demonstrated to be associated with liver damage. However, its potential value in hepatitis B virus (HBV) infection remains unknown. This study was designed to investigate the role of IL-33 in hydrodynamic HBV mouse model. Different doses of IL-33 were used to treat HBV wild-type, ST2 knockout, CD8+ T depletion, NK depletion C57BL/6 mice and C.B-17 SCID and nod SCID mouse, respectively. The concentrations of HBV DNA, HBsAg, HBeAg, and molecules related to liver function were detected in the collected serum at different time points from model mice. Intrahepatic HBcAg was visualized by immunohistochemical staining of liver tissues. In vitro, hepG2 cells were transfected with pAAV-HBV 1.2, then treated with IL-33. The results showed that IL-33 significantly reduced HBV DNA and HBsAg in a dose-dependent manner in HBV wild-type mice. However, in the IL-33 specific receptor ST2 knockout mice, their antiviral effects could not be exerted. Through immunodeficient animal models and in vivo immune cell depletion mouse model, we found that IL-33 could not play antiviral effects without NK cells. Moreover, IL-33 could reduce the levels of HBsAg and HBeAg in the supernatant of HBV-transfected hepG2 cells in vitro. Our study revealed that IL-33 could inhibit HBV through ST2 receptor in the HBV mouse model, and this effect can be impaired without NK cell. Additionally, IL-33 had the direct anti-HBV effect in vitro, indicating that IL-33 could be a potent inducer of HBV clearance and a promising drug candidate.

Characterization of IL-21-expressing recombinant hepatitis B virus (HBV) as a therapeutic agent targeting persisting HBV infection

Chronic infection by hepatitis B virus (HBV) is associated with high risks of liver fibrosis, cirrhosis and hepatocellular carcinoma. In mouse models of HBV persistence, interleukin 21 (IL-21) has been identified as a potent inducer of viral clearance. Strict hepatotropism makes recombinant HBV (rHBV) vectors ideal for liver-targeting gene delivery. Previously, we established an rHBV vector termed 5c3c, which is highly replicative by itself, but requires HBV envelope proteins provided in trans to produce virions. 5c3c-based rHBV virions are capable of delivering cargo gene expression driven by HBV Sp1 promoter into infected hepatocytes. In this work, we explore the feasibility of using 5c3c-derived rHBV for liver-specific delivery of IL-21 as treatment of chronic HBV infection. Methods: 5c3c-derived rHBV replicons harboring mouse or human IL-21 genes (termed 5c3c-mIL-21 and 5c3c-hIL-21 respectively) were constructed and then tested for the production of rHBV virions in vitro and in vivo. 5c3c-mIL-21's anti-HBV effects were determined in chronic HBV mouse model. Furthermore, superinfection by rHBV virions was analysed using HBV-infected HepG2/NTCP cells and human liver chimeric mice. Results: 5c3c-mIL-21 and 5c3c-hIL-21 were efficiently replicative and produced enveloped virions when provided with envelope proteins, both in vitro and in vivo. In mouse model of HBV persistence, IL-21 expressed from injected 5c3c-mIL-21 replicon induced complete viral clearance. 5c3c-mIL-21 and 5c3c-hIL-21 virions could infect HepG2/NTCP cells and engender sustained IL-21 expression. Most importantly, IL-21-expressing rHBV virions could superinfect HBV-infected HepG2/NTCP cells and human hepatocytes in human liver chimeric mice, and engender sustained IL-21 expression and rHBV production. Conclusion: These data suggest the high potential of 5c3c-derived IL-21-expressing rHBV as a novel therapeutic against chronic HBV infection.

Characterization and engineering of broadly reactive monoclonal antibody against hepatitis B virus X protein that blocks its interaction with DDB1

Hepatitis B virus (HBV) X protein (HBx) plays diverse roles in both viral life cycle and HBV-related carcinogenesis. Its interaction with DNA damage-binding protein 1 (DDB1) was shown to be essential for engendering cellular conditions favorable for optimal viral transcription and replication. Previously, we described a mouse monoclonal antibody against HBx (anti-HBx 2A7) recognizing HBx encoded by representative strains from 7 of 8 known HBV genotypes. In this work, we further characterized 2A7 in order to explore its potential usefulness in HBx-targeting applications. We demonstrated that 2A7 recognizes a linear epitope mapped to L⁸⁹PKVLHKR⁹⁶ on HBx, a segment that is highly conserved across genotypes and coincidentally overlaps with the DDB1-interacting segment. HBx-DDB1 binding could be inhibited by 2A7 in vitro, suggesting therapeutic potential. Nucleic acid and amino acid sequences of 2A7 were then obtained, which allowed construction of recombinant antibody and single chain variable fragments (scFv). 2A7-derived recombinant antibody and scFv recapitulate 2A7's HBx-binding capacity and epitope specificity. We also reported preliminary results using cell-penetrating peptide for delivering 2A7 antibody across cell membrane to target intracellular HBx. Anti-HBx 2A7 and 2A7-derived scFv characterized here may give rise to novel HBx-targeting diagnostics and therapeutics for HBV- and HBx-related pathologies.

Evaluation of antiviral - passive - active immunization ("sandwich") therapeutic strategy for functional cure of chronic hepatitis B in mice

Background

Chronic Hepatitis B (CHB) remains a major problem for global public health. Viral persistence and immune defects are the two major reasons for CHB, and it was hypothesized that based on a transient clearance of serum viral DNA and HBsAg “window stage”, active immunization against hepatitis B virus (HBV) might initiate effective host immune responses versus HBV to achieve functional cure of CHB.

Methods

Two experimental mouse models that mice hydrodynamic injected HBV DNA or infected with recombinant AAV/HBV were used. The “sandwich” therapeutic effect by using a potent human anti-HBsAg neutralizing monoclonal antibody (G12) in combination with antiviral drug tenofovir disoproxil fumarate (TDF), followed by active immunization with HBsAg-HBsAb (mYIC) was evaluated.

Findings

A single G12 injection rapidly cleared serum HBsAg in HDI-HBV carrier mice, with a synergistic effect in decreasing viral DNA load when TDF was given orally. When both serum viral DNA and HBsAg load became low or undetectable, mYIC was administered. A more effective clearance of viral DNA and HBsAg was observed and serum HBsAb was developed only in these “sandwich”-treated mice. Efficient intrahepatic anti-HBV immune responses were also observed in these mice, including the formation of aggregates of myeloid cells with CD8⁺T cells and increased TNF-α, granzyme B production.

Interpretation

The “sandwich” combination therapy not only efficiently decreased HBsAg and HBV DNA levels but also induced effective cellular and humoral immunity, which may result in functional cure of CHB.

S100A9 extends lifespan in insulin deficiency

Tens of millions suffer from insulin deficiency (ID); a defect leading to severe metabolic imbalance and death. The only means for management of ID is insulin therapy; yet, this approach is sub-optimal and causes life-threatening hypoglycemia. Hence, ID represents a great medical and societal challenge. Here we report that S100A9, also known as Calgranulin B or Myeloid-Related Protein 14 (MRP14), is a leptin-induced circulating cue exerting beneficial anti-diabetic action. In murine models of ID, enhanced expression of S100A9 alone (i.e. without administered insulin and/or leptin) slightly improves hyperglycemia, and normalizes key metabolic defects (e.g. hyperketonemia, hypertriglyceridemia, and increased hepatic fatty acid oxidation; FAO), and extends lifespan by at least a factor of two. Mechanistically, we report that Toll-Like Receptor 4 (TLR4) is required, at least in part, for the metabolic-improving and pro-survival effects of S100A9. Thus, our data identify the S100A9/TLR4 axis as a putative target for ID care.

Insulin replacement is a valuable therapy for insulin deficiency, however, other therapies are being investigated to restore metabolic homeostasis. Here, the authors identify S100A9 as a leptin induced circulating cue that improves glucose and lipid homeostasis and extends survival in insulin deficient mice.

Lymphocyte Antigen 6 Complex, Locus C+ Monocytes and Kupffer Cells Orchestrate Liver Immune Responses Against Hepatitis B Virus in Mice

To understand the mechanism(s) of age-dependent outcomes of hepatitis B virus (HBV) infection in humans, we previously established an age-related HBV mouse model in which 6-week-old (N6W) C3H/HeN mice exhibited virus tolerance whereas 12-week-old (N12W) counterparts presented virus clearance. By investigating the hepatic myeloid cell dynamics in mice of these two ages, we aim to identify factors associated with HBV clearance. C3H/HeN mice were transfected with an HBV plasmid by hydrodynamic injection. Serum HBV markers were monitored weekly. Hepatic leucocyte populations and their cytokine/chemokine productions were examined at baseline, day 3 (D3), day 7 (D7), and day 14 after injection. C-C chemokine receptor type 2 (CCR2) antagonist and clodronate (CLD) were respectively administered to N12W and N6W mice to study the roles of lymphocyte antigen 6 complex, locus C (Ly6C)⁺ monocytes and Kupffer cells (KCs) in viral clearance. N12W mice had a significantly higher number of TNF-α-secreting Ly6C⁺ monocytes and fewer IL-10-secreting KCs at D3 in the liver than their younger N6W counterparts after HBV transfection. In addition, the elevated number of interferon-γ⁺ TNF-α⁺ CD8⁺ T cells at D7 was only seen in the older cohort. The enhanced Ly6C⁺ monocyte induction in N12W mice resulted from elevated C-C motif chemokine ligand 2 (CCL2) secretion by hepatocytes. CCR2 antagonist administration hampered Ly6C⁺ monocyte recruitment and degree of KC reduction and delayed HBV clearance in N12W animals. Depletion of KCs by CLD liposomes enhanced Ly6C⁺ monocyte recruitment and accelerated HBV clearance in N6W mice. Conclusions: Ly6C⁺ monocytes and KCs may, respectively, represent the resistance and tolerance arms of host defenses. These two cell types play an essential role in determining HBV clearance/tolerance. Manipulation of these cells is a promising avenue for immunotherapy of HBV-related liver diseases.

IL-21-based therapies induce clearance of hepatitis B virus persistence in mouse models

Chronic hepatitis B virus (HBV) infection causes hepatitis, liver cirrhosis and hepatocellular carcinoma. Covalently closed circular DNA (cccDNA) is the sole viral transcription template and not affected by current treatment options, constituting a key determinant of HBV persistence. Novel therapeutics with demonstrable effectiveness against cccDNA are required.

Methods: Previously, we established an HBV persistence mouse model using replicon plasmid derived from a clinical isolate (termed BPS) and identified IL-21 as a potent clearance-inducer. We also described another persistence mouse model based on cccDNA mimics produced in vivo termed recombinant cccDNA (rcccDNA). In this work, effectiveness of IL-21-based gene and cellular therapies was tested using these models.

Results: In both models of HBV persistence, single injections with adeno-associated virus (AAV) expressing murine IL-21 highly efficiently induced clearance of both HBV markers from serum, and more importantly, BPS DNA and rcccDNA from mouse liver. Mechanistically, IL-21-induced clearance was associated with activation and liver infiltration of CD8⁺ T cells, and CD8 antibody injections negatively affected AAV-IL-21 effectiveness. More notably, adoptive transfer of CD8⁺ T cells from AAV-IL-21-cured mice engendered clearance in acceptor HBV persistence mice. Furthermore, cured mice were protected against re-challenge with long-lived memory. Most significantly, infusion of splenocytes from treatment-naïve mice stimulated ex vivo with IL-21 protein and HBV antigen could also induce clearance in treatment-naïve mice.

Conclusion: These data demonstrate IL-21-based gene and cellular therapies as valid candidates for treating chronic HBV infections, with potential in removing cccDNA-harboring hepatocytes via activated CD8⁺ T cells accompanied by long-term protective memory.

Interleukin-33/ST2-Mediated Inflammation Plays a Critical Role in the Pathogenesis and Severity of Type I Autoimmune Hepatitis

Interleukin (IL)‐33 was recently described as a new member of the IL‐1 family; members of this family have proinflammatory activity. IL‐33 and its soluble receptor ST2 (sST2) have been implicated in the pathogenesis of autoimmune diseases. This study investigated serum IL‐33 and sST2 in type I autoimmune hepatitis (AIH) and the relationship of these molecules with clinical and pathologic parameters. Subjects included 65 patients with AIH who were diagnosed in our hospital. The control population included 17 healthy individuals and 36 patients with primary biliary cholangitis (PBC). Mean age at AIH diagnosis was 55.5 years, and the male‐to‐female ratio was 6:59. Serum IL‐33 and sST2 levels were significantly higher in patients with AIH than in those with PBC or controls. Importantly, immunohistochemistry revealed high IL‐33 expression in liver sections from patients with AIH. In particular, serum IL‐33 and sST2 levels were significantly higher in acute‐onset AIH than in chronic‐onset AIH. Serum IL‐33 levels were positively correlated with serum total bilirubin (TB), alanine aminotransferase (ALT), and necroinflammatory activity in AIH. We performed multivariate logistic regression analysis and found serum IL‐33 levels to be independent factors for severe activity. Serum sST2 levels were positively correlated with serum TB and ALT and negatively correlated with serum albumin and prothrombin time in AIH. In particular, serum sST2 levels were significantly higher in severe symptoms of AIH. Serum IL‐33 and sST2 levels in patients with AIH responsive to treatment with prednisolone were significantly decreased after treatment. Interestingly, serum IL‐33 level was associated with a significantly increased risk of relapse. Conclusion: IL‐33/ST2 may play an important role in the pathogenesis and severity of AIH and may be a promising target for AIH therapy.

This study aimed to investigate serum IL‐33 and sST2 in type I autoimmune hepatitis (AIH) patients and its relationship with clinical and pathological parameters. Multivariate analysis was performed, and serum IL‐33 levels were independent factors for severe activity and relapse. Our findings suggest that IL‐33/ST2 may play an important role in the pathogenesis and severity of AIH and may present a promising target for AIH therapy.

Cytokine and chemokine signatures associated with hepatitis B surface antigen loss in hepatitis B patients

BACKGROUND

The clearance of hepatitis B surface antigen (HBsAg) loss, defined as functional cure, is a clinical target in patients with chronic hepatitis B (CH). To understand the immune responses underlying functional cure, we evaluated cytokine and chemokine expression profiles from patients with resolving and nonresolving acute hepatitis B (AH).

METHODS

We cross-sectionally evaluated 41 chemokines and cytokines at the peak of hepatitis in the sera from 41 self-limited AH patients who achieved HBsAg seroconversion, 8 AH patients who failed to clear HBsAg within 1 year after the diagnosis, 8 CH patients with hepatic flare, and 14 healthy volunteers. We longitudinally examined 41 chemokines and cytokines in the sera from 4 self-limited AH patients, 3 chimpanzees inoculated with hepatitis B virus (HBV), and 2 CH patients treated with nucleotide analogs and PEG-IFN-α, one resulting in functional cure.

RESULTS

In AH patients and HBV-inoculated chimpanzees with HBsAg loss, CXCL9, CXCL10, CXCL11, CXCL13, and IL-21 were elevated at hepatitis with subsequent decline of HBsAg. Interestingly, IL-21 elevation was observed only in resolving AH patients but not in nonresolvers. CXCL13 and IL-21 elevation was not observed in CH patients who failed to attain HBsAg loss, even at hepatic flare. A concomitant increase of CXCL13 and IL-21 was significant in CH patients who attained HBsAg seroconversion with a sequential therapy.

CONCLUSION

Elevation of serum CXCL9, CXCL10, CXCL11, CXCL13, and IL-21 might be a hallmark of functional cure of AH or CH patients.

The doses of plasmid backbone plays a major role in determining the HBV clearance in hydrodynamic injection mouse model

Background

Hepatitis B virus (HBV) chronically infects approximately 350 million people worldwide, causing a major risk of liver disease and hepatocellular carcinoma (HCC). Many mouse models have been tried to establish HBV infection through injection with various HBV-containing plasmids. However, it is not well understood that different plasmids, all of which contain the similar HBV genome, even the same plasmids with different dose, results in opposite immune responses toward HBV.

Methods

In this study, we investigated the role of HBV-containing plasmid backbones and the HBcAg in determining the HBV persistence. C57BL/6 mice were injected hydrodynamically with 6 μg or 20 μg of WT pAAV/HBV1.2 plasmid, e/core-null pAAV/HBV1.2 plasmid, or none-HBV genome pAAV/control plasmid. Serum levels of HBV-related markers were measured by quantitative immunoradiometric assay (IRMA). Liver HBcAg expression was detected by immunohistochemical staining. The mRNA levels of cytokines and Th1-related immune factors were quantified by qRT-PCR.

Results

All mice injected with 6 μg of the pAAV/HBV1.2 plasmid shows HBsAg positive at week 6 after hydrodynamic injection (AHI) as previously investigated. However, the mice injected with 20 μg pAAV/HBV1.2 or 6μgpAAV/HBV1.2 plus 14μgpAAV/control plasmid results in HBV clearance within 4 weeks AHI, indicating the anti-HBV activity is induced by 20 μg plasmid DNA, but not by the inserted viral genome. This anti-HBV activity is independent of HBcAg and Toll like receptor (TLR) signaling pathway, since the lack of HBcAg in pAAV/HBV1.2 plasmid or stimulation with TLRs agonists does not influence the kinetics of serum HBsAg in mice. The mRNA levels of t-bet and cxcr3 were dramatically up-regulated in the liver of the mice injected with 20 μg plasmid DNA.

Conclusion

Our studies demonstrate that plasmid backbones are responsible for modulating immune responses to determine HBV persistence or clearance in our HBV mouse model by hydrodynamic injection of HBV-containing plasmid, and Th1 cells play key roles on HBV clearance.

Animal models for the study of hepatitis B virus infection

Even with an effective vaccine, an estimated 240 million people are chronically infected with hepatitis B virus (HBV) worldwide. Current antiviral therapies, including interferon and nucleot(s)ide analogues, rarely cure chronic hepatitis B. Animal models are very crucial for understanding the pathogenesis of chronic hepatitis B and developing new therapeutic drugs or strategies. HBV can only infect humans and chimpanzees, with the use of chimpanzees in HBV research strongly restricted. Thus, most advances in HBV research have been gained using mouse models with HBV replication or infection or models with HBV-related hepadnaviral infection. This review summarizes the animal models currently available for the study of HBV infection.