The size of the viral inoculum contributes to the outcome of hepatitis B virus infection

The roles of continuous and discontinuous proliferations on hepatitis B virus infection

The proliferation of both uninfected and infected hepatocytes, as well as the recycling effects of rcDNA-containing capsids are two key mechanisms playing significant roles in the persistence and clearance of hepatitis B virus (HBV) infection. In this study, the temporal dynamics of this viral infection is investigated through two intercellular mathematical models considering proliferation of both types of hepatocytes (uninfected and infected) and recycling effects of capsids. Both models are formulated on the basis of a key finding in the existing literature: mitosis of an infected hepatocytes yields in two uninfected progenies. In the first model (defined by P-model), we examine the continuous proliferation (which occur continuously), while the second one (defined by M-model) deals with the discontinuous proliferation (happen when the concentration of liver cells decreases to less than 70% of its initial concentration). The proposed models are calibrated with the experimental data obtained from an adult chimpanzee. Results of this study suggest that when both hepatocytes proliferate with equal rate, proliferation helps the individual in a rapid recovery from the acute infection whereas in case of chronic infection, the severity of the infection increases. On the other hand, if the infected hepatocytes proliferate at a different rate that of uninfected hepatocytes, the proliferation of uninfected hepatocytes contributes to increase the infection, but the proliferation of infected hepatocytes acts to reduce the infection from the long-term perspective. The global sensitivity analysis also shows the same results. Furthermore, it is also observed that the differences between the outcomes of continuous and discontinuous proliferations are significant and noteworthy.

Bistability between acute and chronic states in a Model of Hepatitis B Virus Dynamics

Understanding the mechanisms responsible for different clinical outcomes following hepatitis B infection requires a systems investigation of dynamical interactions between the virus and the immune system. To help elucidate mechanisms of protection and those responsible from transition from acute to chronic disease, we developed a deterministic mathematical model of hepatitis B infection that accounts for cytotoxic immune responses resulting in infected cell death, non-cytotoxic immune responses resulting in infected cell cure and protective immunity from reinfection, and cell proliferation. We analyzed the model and presented outcomes based on three important disease markers: the basic reproduction number R0, the infected cells death rate δ (describing the effect of cytotoxic immune responses), and the liver carrying capacity K (describing the liver susceptibility to infection). Using asymptotic and bifurcation analysis techniques, we determined regions where virus is cleared, virus persists, and where clearance-persistence is determined by the size of viral inoculum. These results can guide the development of personalized intervention.

An immune-based predictive model for HBV clearance: validation in multicenter cohorts and mechanistic insights from in vivo studies

BACKGROUND

Chronic HBV infection is a major risk factor for hepatocellular carcinoma, posing a significant global health burden. However, predictive models for HBV clearance based on immune biomarkers remain limited.

METHODS

We systematically developed a predictive tool by quantifying mRNA expression levels of CD4⁺ T-cell subset transcription factors, cytokines, and immune checkpoints in PBMCs from chronic HBV patients and resolved HBV individuals using RT-qPCR. A binary logistic regression model was constructed in the training cohort, with performance evaluated by ROC and calibration curves, followed by internal and external validation in independent cohorts. For in vivo validation, an HBV-transfected mouse model was established via rapid tail vein injection of pGL3-CP-Fluc-HBV1.2C2 plasmid. Outcomes included body weight, HBsAg/HBV DNA levels, and luciferase activity. Kaplan-Meier analysis assessed cumulative clearance rates, while RT-qPCR tracked model-related mRNA dynamics in PBMCs.

RESULTS

The model identified GATA3, FOXP3, IFNG, TNF, and HAVCR2 as key genes, demonstrating robust predictive accuracy for HBV clearance. Dose-specific temporal patterns of immune gene regulation were observed, revealing distinct immunomodulatory mechanisms between groups.

CONCLUSION

This study establishes a reliable immune-based predictive model for HBV clearance and highlights divergent immune responses in chronic versus resolved infection.

The immune response in chronic HBV infection

Hepatitis B virus (HBV) is an ancient virus that has evolved unique strategies to persist as a chronic infection in humans. Here, I summarize the innate and adaptive features of the HBV-host interaction, and I discuss how different profiles of antiviral immunity cannot be predicted only on the basis of virological and clinical parameters.

Phase Ib/IIa randomized study of heterologous ChAdOx1-HBV/MVA-HBV therapeutic vaccination (VTP-300) as monotherapy and combined with low-dose nivolumab in virally-suppressed patients with CHB

BACKGROUND & AIMS

The induction of effective CD8+ T cells is thought to play a critical role in the functional cure of chronic hepatitis B (CHB). Additionally, the use of checkpoint inhibitors is being evaluated to overcome T-cell dysfunction during CHB.

METHODS

A chimpanzee adenoviral vector (ChAdOx1-HBV) and a Modified vaccinia Ankara boost (MVA-HBV) encoding the inactivated polymerase, core, and S region from a consensus genotype C HBV were studied. Fifty-five patients with virally suppressed CHB and HBsAg <4,000 IU/ml were enrolled. Group 1 received MVA-HBV intramuscularly on Day 0 and 28, Group 2 received ChAdOx1-HBV on Day 0 and MVA-HBV on Day 28 (VTP-300), Group 3 received VTP-300 + low-dose nivolumab (LDN) on Day 28, and Group 4 received VTP-300 plus LDN with both injections.

RESULTS

VTP-300 alone and in combination with LDN was well tolerated with no treatment-related serious adverse events. Reductions of HBsAg were demonstrated in Group 2: 3 of 18 patients with starting HBsAg <50 IU/ml had durable log10 declines of >0.7 log10 at 2 months after the last dose. Group 3 (n = 18) had mean reductions in HBsAg of 0.76 log10 and 0.80 log10 (p <0.001) at 2 and 7 months after the last dose. Two patients developed persistent non-detectable HBsAg levels. CD4+ and CD8+ antigen-specific T-cell responses were generated and there was a correlation between IFN-γ ELISpot response and HBsAg decline in Group 2.

CONCLUSIONS

VTP-300 induced CD4+ and CD8+ T cells and lowered HBsAg in a subset of patients with baseline values below 100 IU/ml. The addition of LDN resulted in significant reduction in surface antigen. VTP-300 is a promising immunotherapeutic that warrants further development alone or in combination therapies.

IMPACT AND IMPLICATIONS

The induction of potent, durable CD8+ T cells may be critical to achieving a functional cure in chronic HBV infection. A prime-boost immunotherapeutic consisting of an adenoviral-vector encoding hepatitis B antigens followed by a pox virus boost was shown to induce CD8+ T cells and to lower HBsAg, either alone or more impactfully when administered in conjunction with a checkpoint inhibitor, in patients with chronic hepatitis B. The use of immunotherapeutics in this setting warrants further evaluation.

CLINTRIALS

NCT047789.

CD40 stimulation activates CD8+ T cells and controls HBV in CD4-depleted mice

Background & Aims

HBV treatment is challenging due to the persistence of the covalently closed circular DNA replication pool, which remains unaffected by antiviral intervention. In this study, we determined whether targeting antigen-presenting cells via CD40 stimulation represents an appropriate therapeutic approach for achieving sustained HBV control in a mouse model of HBV replication.

Methods

Mice were transduced with an adeno-associated virus encoding the HBV genome (AAV-HBV) to initiate HBV replication and were administered agonistic CD40 antibody. CD4-depleting antibody was administered in addition to the CD40 antibody. Viral antigens in the blood were measured over time to determine HBV control. HBV-specific CD8+ T cells were quantified in the spleen and liver at the experimental endpoint.

Results

CD40 stimulation in CD4-depleted AAV-HBV mice resulted in the clearance of HBsAg and HBeAg, along with a reduction in liver HBV mRNA, contrasting with CD4-competent counterparts. CD8+ T cells were indispensable for CD40-mediated HBV control, determined by HBV persistence following their depletion. In CD4-replete mice, CD40 stimulation initially facilitated the expansion of HBV-specific CD8+ T cells, which subsequently could not control HBV. Finally, α-CD4/CD40 treatment reduced antigenemia and liver HBV mRNA levels in chronic AAV-HBV mice, with further enhancement through synergy with immunization by VSV-MHBs (vesicular stomatitis virus expressing middle HBsAg).

Conclusions

Our findings underscore the potential of CD40 stimulation as a targeted therapeutic strategy for achieving sustained HBV control and reveal a CD4+ T cell-dependent limitation on CD40-mediated antiviral efficacy.

Impact and implications

Immunotherapy has the potential to overcome immune dysfunction in chronic HBV infection. Using a mouse model of HBV replication, this study shows that CD40 stimulation can induce sustained HBV control, which is dependent on CD8+ T cells and further enhanced by co-immunization. Unexpectedly, CD40-mediated HBV reduction was improved by the depletion of CD4+ cells. These findings suggest potential strategies for reversing HBV persistence in infected individuals.

Low risk of hepatitis B virus reactivation in membranous nephropathy patients with resolved infection undergoing rituximab-based regimens without antiviral prophylaxis

INTRODUCTION

Patients with resolved hepatitis B virus infection undergoing rituximab are at risk of hepatitis B virus reactivation without antiviral prophylaxis. However, the risk in such patients treated with rituximab-based regimens for membranous nephropathy is not clear. We evaluated the risk of hepatitis B virus reactivation in membranous nephropathy patients with resolved infection undergoing rituximab-based regimens without antiviral prophylaxis.

METHODS

Clinical data of 51 membranous nephropathy patients with resolved hepatitis B virus infection undergoing rituximab-based regimens without antiviral prophylaxis were retrospectively analyzed. Among these, 21 patients were followed for more than 1 year after rituximab discontinuation. The clinical data collected aimed to assess patients' responses and the risk of hepatitis B virus reactivation during and after rituximab treatment.

RESULTS

30/51 (58.8 %) patients reached complete or partial remission at 12 months. None of the patients experienced HBsAg seroreversion during rituximab treatment. Alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transpeptidase and total bilirubin levels, as well as the numbers of patients who exceeded the upper limits of normal for alkaline phosphatase and prothrombin time, did not show any statistically significant difference during rituximab-based therapy. Neither did the anti-HBs level, the number of patients with protective anti-HBs titers exceeding 10 U/L, nor the levels of CD19+ B cells, CD4+ T cells, CD8+ T cells, and natural killer cells. Among the 21 patients followed for 12 (ranging from 12 to 19) months after rituximab discontinuation, no hepatitis B virus reactivation was observed. The mean anti-HBs level and the number of patients with anti-HBs titers over 10 U/L did not show any statistically significant difference during the extended follow-up of 33 patient-years. Neither did the CD4+ T cell, CD8+ T cell, nor the natural killer cell counts. One patient presented with an ALT level that exceeded the baseline value by three times and reached above 100 U/L, accompanied by elevations in AST, GGT, and ALP levels. Meanwhile, the anti-HBs titer was 816.09 U/L, and HBsAg was negative.

CONCLUSION

The administration of rituximab-based regimens in membranous nephropathy patients with hepatitis B virus resolved infection leads to a low risk of hepatitis B virus reactivation without antiviral prophylaxis. Patient's immune status, drug combination, rituximab strategy should be fully evaluated when considering antiviral prophylaxis therapy.

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

Background & Aims

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

Methods

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

Results

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

Conclusions

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

Impact and Implications

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

Mathematical Models of Early Hepatitis B Virus Dynamics in Humanized Mice

Analyzing the impact of the adaptive immune response during acute hepatitis B virus (HBV) infection is essential for understanding disease progression and control. Here we developed mathematical models of HBV infection which either lack terms for adaptive immune responses, or assume adaptive immune responses in the form of cytolytic immune killing, non-cytolytic immune cure, or non-cytolytic-mediated block of viral production. We validated the model that does not include immune responses against temporal serum hepatitis B DNA (sHBV) and temporal serum hepatitis B surface-antigen (HBsAg) experimental data from mice engrafted with human hepatocytes (HEP). Moreover, we validated the immune models against sHBV and HBsAg experimental data from mice engrafted with HEP and human immune system (HEP/HIS). As expected, the model that does not include adaptive immune responses matches the observed high sHBV and HBsAg concentrations in all HEP mice. By contrast, while all immune response models predict reduction in sHBV and HBsAg concentrations in HEP/HIS mice, the Akaike Information Criterion cannot discriminate between non-cytolytic cure (resulting in a class of cells refractory to reinfection) and antiviral block functions (of up to 99 % viral production 1-3 weeks following peak viral load). We can, however, reject cytolytic killing, as it can only match the sHBV and HBsAg data when we predict unrealistic levels of hepatocyte loss.

The dual role of regulatory T cells in hepatitis B virus infection and related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major contributor to cancer-related deaths worldwide. Hepatitis B virus (HBV) infection is a major etiologic factor leading to HCC. While there have been significant advancements in controlling HBV replication, achieving a complete cure for HBV-related HCC (HBV-HCC) remains an intricate challenge. HBV persistence is attributed to a myriad of mechanisms, encompassing both innate and adaptive immune responses. Regulatory T cells (Tregs) are pivotal in upholding immune tolerance and modulating excessive immune activation. During HBV infection, Tregs mediate specific T cell suppression, thereby contributing to both persistent infection and the mitigation of liver inflammatory responses. Studies have demonstrated an augmented expression of circulating and intrahepatic Tregs in HBV-HCC, which correlates with impaired CD8+ T cell function. Consequently, Tregs play a dual role in the context of HBV infection and the progression of HBV-HCC. In this comprehensive review, we discuss pertinent studies concerning Tregs in HBV infection, HBV-related cirrhosis and HCC. Furthermore, we summarize Treg responses to antiviral therapy and provide Treg-targeted therapies specific to HBV and HCC.

Routine evaluation of HBV-specific T cell reactivity in chronic hepatitis B using a broad-spectrum T-cell epitope peptide library and ELISpot assay

BACKGROUND

The clinical routine test of HBV-specific T cell reactivity is still limited due to the high polymorphisms of human leukocyte antigens (HLA) in patient cohort and the lack of universal detection kit, thus the clinical implication remains disputed.

METHODS

A broad-spectrum peptide library, which consists of 103 functionally validated CD8+ T-cell epitopes spanning overall HBsAg, HBeAg, HBx and HBpol proteins and fits to the HLA polymorphisms of Chinese and Northeast Asian populations, was grouped into eight peptide pools and was used to establish an ELISpot assay for enumerating the reactive HBV-specific T cells in PBMCs. Totally 294 HBV-infected patients including 203 ones with chronic hepatitis B (CHB), 13 ones in acute resolved stage (R), 52 ones with liver cirrhosis (LC) and 26 ones with hepatocellular carcinoma (HCC) were detected, and 33 CHB patients were longitudinally monitored for 3 times with an interval of 3-5 months.

RESULTS

The numbers of reactive HBV-specific T cells were significantly correlated with ALT level, HBsAg level, and disease stage (R, CHB, LC and HCC), and R patients displayed the strongest HBV-specific T cell reactivity while CHB patients showed the weakest one. For 203 CHB patients, the numbers of reactive HBV-specific T cells presented a significantly declined trend when the serum viral DNA load, HBsAg, HBeAg or ALT level gradually increased, but only a very low negative correlation coefficient was defined (r = - 0.21, - 0.21, - 0.27, - 0.079, respectively). Different Nucleotide Analogs (NUCs) did not bring difference on HBV-specific T cell reactivity in the same duration of treatment. NUCs/pegIFN-α combination led to much more reactive HBV-specific T cells than NUCs monotherapy. The dynamic numbers of reactive HBV-specific T cells were obviously increasing in most CHB patients undergoing routine treatment, and the longitudinal trend possess a high predictive power for the hepatitis progression 6 or 12 months later.

CONCLUSION

The presented method could be developed into an efficient reference method for the clinical evaluation of cellular immunity. The CHB patients presenting low reactivity of HBV-specific T cells have a worse prognosis for hepatitis progression and should be treated using pegIFN-α to improve host T-cell immunity.

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

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

TLR9-independent CD8+ T cell responses in hepatic AAV gene transfer through IL-1R1-MyD88 signaling

Upon viral infection of the liver, CD8+ T cell responses may be triggered despite the immune suppressive properties that manifest in this organ. We sought to identify pathways that activate responses to a neoantigen expressed in hepatocytes, using adeno-associated viral (AAV) gene transfer. It was previously established that cooperation between plasmacytoid dendritic cells (pDCs), which sense AAV genomes by Toll-like receptor 9 (TLR9), and conventional DCs promotes cross-priming of capsid-specific CD8+ T cells. Surprisingly, we find local initiation of a CD8+ T cell response against antigen expressed in ∼20% of murine hepatocytes, independent of TLR9 or type I interferons and instead relying on IL-1 receptor 1-MyD88 signaling. Both IL-1α and IL-1β contribute to this response, which can be blunted by IL-1 blockade. Upon AAV administration, IL-1-producing pDCs infiltrate the liver and co-cluster with XCR1+ DCs, CD8+ T cells, and Kupffer cells. Analogous events were observed following coagulation factor VIII gene transfer in hemophilia A mice. Therefore, pDCs have alternative means of promoting anti-viral T cell responses and participate in intrahepatic immune cell networks similar to those that form in lymphoid organs. Combined TLR9 and IL-1 blockade may broadly prevent CD8+ T responses against AAV capsid and transgene product.

Classifying hepatitis B therapies with insights from covalently closed circular DNA dynamics

The achievement of a functional cure for chronic hepatitis B (CHB) remains limited to a minority of patients treated with currently approved drugs. The primary objective in developing new anti-HBV drugs is to enhance the functional cure rates for CHB. A critical prerequisite for the functional cure of CHB is a substantial reduction, or even eradication of covalently closed circular DNA (cccDNA). Within this context, the changes in cccDNA levels during treatment become as a pivotal concern. We have previously analyzed the factors influencing cccDNA dynamics and introduced a preliminary classification of hepatitis B treatment strategies based on these dynamics. In this review, we employ a systems thinking perspective to elucidate the fundamental aspects of the HBV replication cycle and to rationalize the classification of treatment strategies according to their impact on the dynamic equilibrium of cccDNA. Building upon this foundation, we categorize current anti-HBV strategies into two distinct groups and advocate for their combined use to significantly reduce cccDNA levels within a well-defined timeframe.

Differential kinetics of splenic CD169+ macrophage death is one underlying cause of virus infection fate regulation

Acute infection and chronic infection are the two most common fates of pathogenic virus infections. While several factors that contribute to these fates are described, the critical control points and the mechanisms that underlie infection fate regulation are incompletely understood. Using the acute and chronic lymphocytic choriomeningitis virus (LCMV) infection model of mice, we find that the early dynamic pattern of the IFN-I response is a differentiating trait between both infection fates. Acute-infected mice generate a 2-wave IFN-I response while chronic-infected mice generate only a 1-wave response. The underlying cause is a temporal difference in CD8 T cell-mediated killing of splenic marginal zone CD169+ macrophages. It occurs later in acute infection and thus enables CD169+ marginal zone macrophages to produce the 2nd IFN-I wave. This is required for subsequent immune events including induction of inflammatory macrophages, generation of effector CD8+ T cells and virus clearance. Importantly, these benefits come at a cost for the host in the form of spleen fibrosis. Due to an earlier marginal zone destruction, these ordered immune events are deregulated in chronic infection. Our findings demonstrate the critical importance of kinetically well-coordinated sequential immune events for acute infection control and highlights that it may come at a cost for the host organism.

CD4+ T cells reverse surface antigen persistence in a mouse model of HBV replication

IMPORTANCE

Hepatitis B virus (HBV) is a leading causative agent of viral hepatitis. A preventative vaccine has existed for decades, but only limited treatment options are available for people living with chronic HBV. Animal models for studying HBV are constrained due to narrow viral tropism, impeding understanding of the natural immune response to the virus. Here, using a vector to overcome the narrow host range and establish HBV replication in mice, we identified the role of helper T cells in controlling HBV. We show that helper T cells promote the B cell's ability to generate antibodies that remove HBV and its associated surface antigen from the blood and that transfer of purified helper T cells from HBV-immunized mice can reverse the accumulation of virus and antigen, furthering our understanding of the immune response to HBV.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Syndrome of liver depression and spleen deficiency is a primary TCM syndrome of response to entecavir + FuZheng HuaYu in patients with HBV-related liver fibrosis

Objective

Although clinical studies have found that Chinese patent medicine FuZheng HuaYu tablet/capsule can promote the reversal of HBV-related liver fibrosis, not all sufferers have histopathological responses. This study aims to explore the correlation between traditional Chinese medicine (TCM) syndromes and response to entecavir + FuZheng HuaYu (ETV + FZHY) in patients with HBV-related liver fibrosis.

Methods

This a multi-center cross-sectional study. According to the different treatment strategies that sufferers have ever received, a total of 437 cases were included and divided into ETV + FZHY group and ETV + placebo group. And based on the relevant efficacy determination criteria, the two groups were subdivided into efficacy responders and non-responders. Then, TCM clinical questionnaire information of these patients were collected for subsequent analysis to acquire relevant syndrome elements and TCM syndromes.

Results

No matter what group was, the first three frequency of TCM pathological position in efficacy responders were as follows: Liver > Spleen > Stomach (TCM concepts). As for the ETV + FZHY group, the first three frequency of pathological nature was ranked as Qi deficiency > Dampness > Heat. Compared with the non-responders, the frequency of Spleen, Stomach, Qi deficiency, Heat, and Qi movement stagnation was significantly increased in the efficacy responders (P < 0.05). In terms of TCM syndromes, the frequency increase of Syndrome of liver depression and spleen deficiency (LDSD), in the efficacy responders, changed more obviously than the non-responders (Chi2 = 6.32, P = 0.0006).

Conclusions

TCM syndrome elements of Spleen, Stomach, Qi deficiency, Heat, and Qi movement stagnation were closely associated with efficacy responders with HBV-related liver fibrosis in the ETV + FZHY group. Moreover, LDSD was a primary TCM syndrome in these responders.

Induction of broad multifunctional CD8+ and CD4+ T cells by hepatitis B virus antigen-based synthetic long peptides ex vivo

Introduction

Therapeutic vaccination based on synthetic long peptides (SLP®) containing both CD4+ and CD8+ T cell epitopes is a promising treatment strategy for chronic hepatitis B infection (cHBV).

Methods

We designed SLPs for three HBV proteins, HBcAg and the non-secreted proteins polymerase and X, and investigated their ability to induce T cell responses ex vivo. A set of 17 SLPs was constructed based on viral protein conservation, functionality, predicted and validated binders for prevalent human leukocyte antigen (HLA) supertypes, validated HLA I epitopes, and chemical producibility.

Results

All 17 SLPs were capable of inducing interferon gamma (IFNɣ) production in samples from four or more donors that had resolved an HBV infection in the past (resolver). Further analysis of the best performing SLPs demonstrated activation of both CD8+ and CD4+ multi-functional T cells in one or more resolver and patient sample(s). When investigating which SLP could activate HBV-specific T cells, the responses could be traced back to different peptides for each patient or resolver.

Discussion

This indicates that a large population of subjects with different HLA types can be covered by selecting a suitable mix of SLPs for therapeutic vaccine design. In conclusion, we designed a set of SLPs capable of inducing multifunctional CD8+ and CD4+ T cells ex vivo that create important components for a novel therapeutic vaccine to cure cHBV.

Modeling suggests that virion production cycles within individual cells is key to understanding acute hepatitis B virus infection kinetics

Hepatitis B virus (HBV) infection kinetics in immunodeficient mice reconstituted with humanized livers from inoculation to steady state is highly dynamic despite the absence of an adaptive immune response. To recapitulate the multiphasic viral kinetic patterns, we developed an agent-based model that includes intracellular virion production cycles reflecting the cyclic nature of each individual virus lifecycle. The model fits the data well predicting an increase in production cycles initially starting with a long production cycle of 1 virion per 20 hours that gradually reaches 1 virion per hour after approximately 3-4 days before virion production increases dramatically to reach to a steady state rate of 4 virions per hour per cell. Together, modeling suggests that it is the cyclic nature of the virus lifecycle combined with an initial slow but increasing rate of HBV production from each cell that plays a role in generating the observed multiphasic HBV kinetic patterns in humanized mice.

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

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

Activation of CD4 T cells during prime immunization determines the success of a therapeutic hepatitis B vaccine in HBV-carrier mouse models

BACKGROUND & AIMS

We recently developed a heterologous therapeutic vaccination scheme (TherVacB) comprising a particulate protein prime followed by a modified vaccinia-virus Ankara (MVA)-vector boost for the treatment of HBV. However, the key determinants required to overcome HBV-specific immune tolerance remain unclear. Herein, we aimed to study new combination adjuvants and unravel factors that are essential for the antiviral efficacy of TherVacB.

METHODS

Recombinant hepatitis B surface and core antigen (HBsAg and HBcAg) particles were formulated with different liposome- or oil-in-water emulsion-based combination adjuvants containing saponin QS21 and monophosphoryl lipid A; these formulations were compared to STING-agonist c-di-AMP and conventional aluminium hydroxide formulations. Immunogenicity and the antiviral effects of protein antigen formulations and the MVA-vector boost within TherVacB were evaluated in adeno-associated virus-HBV-infected and HBV-transgenic mice.

RESULTS

Combination adjuvant formulations preserved HBsAg and HBcAg integrity for ≥12 weeks, promoted human and mouse dendritic cell activation and, within TherVacB, elicited robust HBV-specific antibody and T-cell responses in wild-type and HBV-carrier mice. Combination adjuvants that prime a balanced HBV-specific type 1 and 2 T helper response induced high-titer anti-HBs antibodies, cytotoxic T-cell responses and long-term control of HBV. In the absence of an MVA-vector boost or following selective CD8 T-cell depletion, HBsAg still declined (mediated mainly by anti-HBs antibodies) but HBV replication was not controlled. Selective CD4 T-cell depletion during the priming phase of TherVacB resulted in a complete loss of vaccine-induced immune responses and its therapeutic antiviral effect in mice.

CONCLUSIONS

Our results identify CD4 T-cell activation during the priming phase of TherVacB as a key determinant of HBV-specific antibody and CD8 T-cell responses.

IMPACT AND IMPLICATIONS

Therapeutic vaccination is a potentially curative treatment option for chronic hepatitis B. However, it remains unclear which factors are essential for breaking immune tolerance in HBV carriers and determining successful outcomes. Our study provides the first direct evidence that efficient priming of HBV-specific CD4 T cells determines the success of therapeutic hepatitis B vaccination in two preclinical HBV-carrier mouse models. Applying an optimal formulation of HBV antigens that activates CD4 and CD8 T cells during prime immunization provided the foundation for an antiviral effect of therapeutic vaccination, while depletion of CD4 T cells led to a complete loss of vaccine-induced antiviral efficacy. Boosting CD8 T cells was important to finally control HBV in these mouse models. Our findings provide important insights into the rational design of therapeutic vaccines for the cure of chronic hepatitis B.

Studying T Cell Responses to Hepatotropic Viruses in the Liver Microenvironment

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

Can T Cells Abort SARS-CoV-2 and Other Viral Infections?

Despite the highly infectious nature of the SARS-CoV-2 virus, it is clear that some individuals with potential exposure, or even experimental challenge with the virus, resist developing a detectable infection. While a proportion of seronegative individuals will have completely avoided exposure to the virus, a growing body of evidence suggests a subset of individuals are exposed, but mediate rapid viral clearance before the infection is detected by PCR or seroconversion. This type of "abortive" infection likely represents a dead-end in transmission and precludes the possibility for development of disease. It is, therefore, a desirable outcome on exposure and a setting in which highly effective immunity can be studied. Here, we describe how early sampling of a new pandemic virus using sensitive immunoassays and a novel transcriptomic signature can identify abortive infections. Despite the challenges in identifying abortive infections, we highlight diverse lines of evidence supporting their occurrence. In particular, expansion of virus-specific T cells in seronegative individuals suggests abortive infections occur not only after exposure to SARS-CoV-2, but for other coronaviridae, and diverse viral infections of global health importance (e.g., HIV, HCV, HBV). We discuss unanswered questions related to abortive infection, such as: 'Are we just missing antibodies? Are T cells an epiphenomenon? What is the influence of the dose of viral inoculum?' Finally, we argue for a refinement of the current paradigm that T cells are only involved in clearing established infection; instead, we emphasise the importance of considering their role in terminating early viral replication by studying abortive infections.

Exposed seronegative: Cellular immune responses to SARS-CoV-2 in the absence of seroconversion

The factors determining whether infection will occur following exposure to SARS-CoV-2 remain elusive. Certain SARS-CoV-2-exposed individuals mount a specific T-cell response but fail to seroconvert, representing a population that may provide further clarity on the nature of infection susceptibility and correlates of protection against SARS-CoV-2. Exposed seronegative individuals have been reported in patients exposed to the blood-borne pathogens Human Immunodeficiency virus and Hepatitis C virus and the sexually transmitted viruses Hepatitis B virus and Herpes Simplex virus. By comparing the quality of seronegative T-cell responses to SARS-CoV-2 with seronegative cellular immunity to these highly divergent viruses, common patterns emerge that offer insights on the role of cellular immunity against infection. For both SARS-CoV-2 and Hepatitis C, T-cell responses in exposed seronegatives are consistently higher than in unexposed individuals, but lower than in infected, seropositive patients. Durability of T-cell responses to Hepatitis C is dependent upon repeated exposure to antigen - single exposures do not generate long-lived memory T-cells. Finally, exposure to SARS-CoV-2 induces varying degrees of immune activation, suggesting that exposed seronegative individuals represent points on a spectrum rather than a discrete group. Together, these findings paint a complex landscape of the nature of infection but provide clues as to what may be protective early on in SARS-CoV-2 disease course. Further research on this phenomenon, particularly through cohort studies, is warranted.

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.

Current Best Practice in Hepatitis B Management and Understanding Long-term Prospects for Cure

The hepatitis B virus (HBV) is a major cause of cirrhosis and hepatocellular carcinoma worldwide. Despite an effective vaccine, the prevalence of chronic infection remains high. Current therapy is effective at achieving on-treatment, but not off-treatment, viral suppression. Loss of hepatitis B surface antigen, the best surrogate marker of off-treatment viral suppression, is associated with improved clinical outcomes. Unfortunately, this end point is rarely achieved with current therapy because of their lack of effect on covalently closed circular DNA, the template of viral transcription and genome replication. Major advancements in our understanding of HBV virology along with better understanding of immunopathogenesis have led to the development of a multitude of novel therapeutic approaches with the prospect of achieving functional cure (hepatitis B surface antigen loss) and perhaps complete cure (clearance of covalently closed circular DNA and integrated HBV DNA). This review will cover current best practice for managing chronic HBV infection and emerging novel therapies for HBV infection and their prospect for cure.

The Origin of Capsid-Derived Immune Complexes and Their Impact on HBV-Induced Liver Diseases

Over 240 million people worldwide are chronically infected with Hepatitis B Virus (HBV), a hepatotropic DNA virus with an evolutionary root of over 400 million years. Persistent HBV infection exhibits distinct and diverse phases of disease, from minimal liver pathology to fulminant Hepatitis, that vary in duration and severity among individuals. Although huge progress has been made in HBV research which has yielded an effective prophylactic vaccine and potent antiviral therapy, our understanding of its virology and immunobiology is still far from complete. For example, the recent re-discovery of serum HBV RNA in chronic Hepatitis B (CHB) patients has led to the proposal of noncanonical viral particles such as RNA virion and capsid-derived immune complex (Capsid-Antibody-Complexes, CACs) that contradict long-established basic theory. Furthermore, the existence of capsid-derived immune complex may hint at novel mechanism of HBV-induced liver disease. Here, we summarize the past and recent literature on HBV-induced immune complex. We propose that the release of capsid-derived particles by HBV has its deep evolutionary origin, and the associated complement activation serves as an indispensable trigger for intrahepatic damage and a catalyst for further cell-mediated immunopathology.

Why doesn't Ebola virus cause pandemics like SARS-CoV-2?

Ebola virus is among the most dangerous, contagious and deadly etiological causes of viral diseases. However, Ebola virus has never extensively spread in human population and never have led to a pandemic. Why? The mechanistic biophysical model revealing the biothermodynamic background of virus-host interaction) could help us to understand pathogenesis of Ebola virus disease (earlier known as the Ebola hemorrhagic fever). In this paper for the first time the empirical formula, thermodynamic properties of biosynthesis (including the driving force of virus multiplication in the susceptible host), binding constant and thermodynamic properties of binding are reported. Thermodynamic data for Ebola virus were compared with data for SARS-CoV-2 to explain why SARS-CoV-2 has caused a pandemic, while Ebola remains on local epidemic level. The empirical formula of the Ebola virus was found to be CH_1.569O_0.3281N_0.2786P_0.00173S_0.00258. Standard Gibbs energy of biosynthesis of the Ebola virus nucleocapsid is -151.59 kJ/C-mol.

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.

Programmed Cell Death Protein 1 Axis Inhibition in Viral Infections: Clinical Data and Therapeutic Opportunities

A vital function of the immune system is the modulation of an evolving immune response. It is responsible for guarding against a wide variety of pathogens as well as the establishment of memory responses to some future hostile encounters. Simultaneously, it maintains self-tolerance and minimizes collateral tissue damage at sites of inflammation. In recent years, the regulation of T-cell responses to foreign or self-protein antigens and maintenance of balance between T-cell subsets have been linked to a distinct class of cell surface and extracellular components, the immune checkpoint molecules. The fact that both cancer and viral infections exploit similar, if not the same, immune checkpoint molecules to escape the host immune response highlights the need to study the impact of immune checkpoint blockade on viral infections. More importantly, the process through which immune checkpoint blockade completely changed the way we approach cancer could be the key to decipher the potential role of immunotherapy in the therapeutic algorithm of viral infections. This review focuses on the effect of programmed cell death protein 1/programmed death-ligand 1 blockade on the outcome of viral infections in cancer patients as well as the potential benefit from the incorporation of immune checkpoint inhibitors (ICIs) in treatment of viral infections.

Prevalence and Genomic Sequence Analysis of Domestic Cat Hepadnavirus in the United States

Hepadnaviruses are partially double-stranded DNA viruses that infect a variety of species. The prototypical virus in this family is the human hepatitis B virus, which chronically infects approximately 400 million people worldwide and is a risk factor for progressive liver disease and liver cancer. The first hepadnavirus isolated from carnivores was a domestic cat hepadnavirus (DCH), initially identified in Australia and subsequently detected in cats in Europe and Asia. As with all characterized hepadnaviruses so far, DCH infection has been associated with hepatic disease in its host. Prevalence of this infection in the United States has not been explored broadly. Thus, we utilized conventional and quantitative PCR to screen several populations of domestic cats to estimate DCH prevalence in the United States. We detected DCH DNA in 1 out of 496 animals (0.2%) in the U.S. cohort. In contrast, we detected circulating DCH DNA in 7 positive animals from a cohort of 67 domestic cats from Australia (10.4%), consistent with previous studies. The complete consensus genome of the U.S. DCH isolate was sequenced by Sanger sequencing with overlapping PCR products. An in-frame deletion of 157 bp was identified in the N-terminus of the core open reading frame. The deletion begins at the direct repeat 1 sequence (i.e., the 5′ end of the expected double-stranded linear DNA form), consistent with covalently closed circular DNA resultant from illegitimate recombination described in other hepadnaviruses. Comparative genome sequence analysis indicated that the closest described relatives of the U.S. DCH isolate are those previously isolated in Italy. Motif analysis supports DCH using NTCP as an entry receptor, similar to human HBV. Our work indicates that chronic DCH prevalence in the U.S. is likely low compared to other countries.

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

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

Comparing the efficacy and safety of tenofovir and adefovir or combined drug treatment for the treatment of chronic hepatitis B infection: a systematic review and meta-analysis

BACKGROUND

Chronic hepatitis B (CHB) affects a vast population globally. A variety of drugs are available for the treatment of CHB, including tenofovir (TDF) and adefovir (ADV). However, the efficacy of monotherapy drug treatment is inconclusive, the safety and efficacy of TDF remain unclear, more data are needed to be included and combined drug treatment is considered to exhibit higher efficacy. To explore this issue, we performed a current literature review and meta-analysis to compare the efficacy and safety of ADV vs. TDF, TDF vs. ADV + lamivudine (LAM); TDF vs. ADV + entecavir (ETV).

METHODS

We systematically searched China National Knowledge Infrastructure, the Cochrane Library, Embase, PubMed, Chinese VIP, and Wanfang Data, for relevant clinical trials since July 2015, all included studies were based on PICOS principles and evaluated independently by the reviewers in accordance with the Cochrane Handbook (Rob2.0). A meta-analysis was performed by using Review Manager 5.4.

RESULTS

We included a total of 32 studies, including 31 randomized controlled trials and one retrospective study involving 2,473 patients. The results revealed a low risk of bias in included studies, that the virologic response of TDF was superior to ADV (P<0.05). And TDF was also superior to ADV in Serum creatinine levels, Immunologic function, and safety profile. However, when ADV was combined with other medications, it was superior to TDF in alanine aminotransferase (ALT) level and Tbil level and adverse reactions, but on other indicators, TDF was superior to drug combination therapy.

CONCLUSIONS

Results showed that TDF was superior to ADV in the parameters of ALT, hepatitis B virus (HBV)-DNA reduction, HBeAg-negative conversion rate, safety, and total bilirubin levels in patients with CHB. However, when ADV was combined with LAM or ETV, they often showed the same therapeutic effect as TDF in parameters such as ALT level and Tbil level and combined therapy can effectively reduce the occurrence of adverse reactions. In this study, because the sample source countries were limited, a greater number of global studies are needed in the future to verify the current findings.

Immunological biomarker discovery in cure regimens for chronic hepatitis B virus infection

There have been unprecedented advances in the identification of new treatment targets for chronic hepatitis B that are being developed with the goal of achieving functional cure in patients who would otherwise require lifelong nucleoside analogue treatment. Many of the new investigational therapies either directly target the immune system or are anticipated to impact immunity indirectly through modulation of the viral lifecycle and antigen production. While new viral biomarkers (HBV RNA, HBcAg, small, middle, large HBs isoforms) are proceeding through validation steps in clinical studies, immunological biomarkers are non-existent outside of clinical assays for antibodies to HBs, HBc and HBe. To develop clinically applicable immunological biomarkers to measure mechanisms of action, inform logical combination strategies, and guide clinical management for use and discontinuation of immune-targeting drugs, immune assays must be incorporated into phase I/II clinical trials. This paper will discuss the importance of sample collection, the assays available for immunological analyses, their advantages/disadvantages and suggestions for their implementation in clinical trials. Careful consideration must be given to ensure appropriate immunological studies are included as a primary component of the trial with deeper immunological analysis provided by ancillary studies. Standardising immunological assays and data obtained from clinical trials will identify biomarkers that can be deployed in the clinic, independently of specialised immunology laboratories.

Getting to HBV cure: The promising paths forward

Chronic HBV infection is a global public health burden estimated to impact nearly 300 million persons worldwide. Despite the advent of potent antiviral agents that effectively suppress viral replication, HBV cure remains difficult to achieve because of the persistence of covalently closed circular DNA (cccDNA), HBV-DNA integration into the host genome, and impaired immune response. Indefinite treatment is necessary for most patients to maintain level of viral suppression. The success of direct-acting antivirals (DAAs) for hepatitis C treatment has rejuvenated the search for a cure for chronic hepatitis B (CHB), though an HBV cure likely requires an additional layer: immunomodulators for restoration of robust immune responses. DAAs such as entry inhibitors, capsid assembly modulators, inhibitors of subviral particle release, cccDNA silencers, and RNA interference molecules have reached clinical development. Immunomodulators, namely innate immunomodulators (Toll-like receptor agonists), therapeutic vaccines, checkpoint inhibitors, and monoclonal antibodies, are also progressing toward clinical development. The future of the HBV cure possibly lies in triple combination therapies with concerted action on replication inhibition, antigen reduction, and immune stimulation. Many obstacles remain, such as overcoming translational failures, choosing the right endpoint using the right biomarkers, and leveraging current treatments in combination regimens to enhance response rates. This review gives an overview of the current therapies for CHB, HBV biomarkers used to evaluate treatment response, and development of DAAs and immune-targeting drugs and discusses the limitations and unanswered questions on the journey to an HBV cure.

HIV Infection Predisposes to Increased Chances of HBV Infection: Current Understanding of the Mechanisms Favoring HBV Infection at Each Clinical Stage of HIV Infection

Human immunodeficiency virus (HIV) selectively targets and destroys the infection-fighting CD4+ T-lymphocytes of the human immune system, and has a life cycle that encompasses binding to certain cells, fusion to that cell, reverse transcription of its genome, integration of its genome into the host cell DNA, replication of the HIV genome, assembly of the HIV virion, and budding and subsequent release of free HIV virions. Once a host is infected with HIV, the host’s ability to competently orchestrate effective and efficient immune responses against various microorganisms, such as viral infections, is significantly disrupted. Without modern antiretroviral therapy (ART), HIV is likely to gradually destroy the cellular immune system, and thus the initial HIV infection will inexorably evolve into acquired immunodeficiency syndrome (AIDS). Generally, HIV infection in a patient has an acute phase, a chronic phase, and an AIDS phase. During these three clinical stages, patients are found with relatively specific levels of viral RNA, develop rather distinctive immune conditions, and display unique clinical manifestations. Convergent research evidence has shown that hepatitis B virus (HBV) co-infection, a common cause of chronic liver disease, is fairly common in HIV-infected individuals. HBV invasion of the liver can be facilitated by HIV infection at each clinical stage of the infection due to a number of contributing factors, including having identical transmission routes, immunological suppression, gut microbiota dysbiosis, poor vaccination immune response to hepatitis B immunization, and drug hepatotoxicity. However, there remains a paucity of research investigation which critically describes the influence of the different HIV clinical stages and their consequences which tend to favor HBV entrenchment in the liver. Herein, we review advances in the understanding of the mechanisms favoring HBV infection at each clinical stage of HIV infection, thus paving the way toward development of potential strategies to reduce the prevalence of HBV co-infection in the HIV-infected population.

Ongoing viral replication and production of infectious virus in patients with chronic hepatitis B virus suppressed below the limit of quantitation on long-term nucleos(t)ide therapy

Nucleos(t)ide analogs are standard-of-care for the treatment of chronic hepatitis B and can effectively reduce hepatitis B virus (HBV) replication but rarely leads to cure. Nucleos(t)ide analogs do not directly eliminate the viral episome, therefore treatment cessation typically leads to rapid viral rebound. While treatment is effective, HBV DNA is still detectable (although not quantifiable) in the periphery of the majority of nucleos(t)ide analog treated HBV patients, even after prolonged treatment. Addressing whether the detectable HBV DNA represents infectious virus is a key unknown and has important implications for the development of a curative treatment for HBV. The minimum HBV genome equivalents required to establish infection in human liver chimeric mice was determined by titration of HBV patient sera and the infectivity in chimeric mice of serum from patients (n = 7) suppressed to the limit of detection on nucleos(t)ide analog therapy was evaluated. A minimum of 5 HBV genome equivalents were required to establish infection in the chimeric mice, confirming this model has sufficient sensitivity to determine whether serum from virally suppressed patients contains infectious virus. Strikingly, serum from 75% (n = 3 out of 4) of nucleos(t)ide-treated HBV patients with DNA that was detectable, but below the lower limit of quantitation, also established infection in the chimeric mice. These results demonstrate that infectious virus is still present in some HBV patients on suppressive nucleos(t)ide therapy. This residual virus may support viral persistence via continuous infection and explain the ongoing risk for HBV-related complications despite long-term suppression on therapy. Thus, additional treatment intensification may facilitate HBV cure.

Association of Lower Exposure Risk With Paucisymptomatic/Asymptomatic Infection, Less Severe Disease, and Unrecognized Ebola Virus Disease: A Seroepidemiological Study

Background

It remains unclear if there is a dose-dependent relationship between exposure risk to Ebola virus (EBOV) and severity of illness.

Methods

From September 2016 to July 2017, we conducted a cross-sectional, community-based study of Ebola virus disease (EVD) cases and household contacts of several transmission chains in Kono District, Sierra Leone. We analyzed 154 quarantined households, comprising both reported EVD cases and their close contacts. We used epidemiological surveys and blood samples to define severity of illness as no infection, pauci-/asymptomatic infection, unrecognized EVD, reported EVD cases who survived, or reported EVD decedents. We determine seropositivity with the Filovirus Animal Nonclinical Group EBOV glycoprotein immunoglobulin G antibody test. We defined levels of exposure risk from 8 questions and considered contact with body fluid as maximum exposure risk.

Results

Our analysis included 76 reported EVD cases (both decedents and survivors) and 421 close contacts. Among these contacts, 40 were seropositive (22 paucisymptomatic and 18 unrecognized EVD), accounting for 34% of the total 116 EBOV infections. Higher exposure risks were associated with having had EBOV infection (maximum risk: adjusted odds ratio [AOR], 12.1 [95% confidence interval {CI}, 5.8-25.4; trend test: P < .001) and more severe illness (maximum risk: AOR, 25.2 [95% CI, 6.2-102.4]; trend test: P < .001).

Conclusions

This community-based study of EVD cases and contacts provides epidemiological evidence of a dose-dependent relationship between exposure risk and severity of illness, which may partially explain why pauci-/asymptomatic EBOV infection, less severe disease, and unrecognized EVD occurs.

Protective Role of Rheumatic Diseases Against Hepatitis B Virus Infection and Human Leukocyte Antigen B27 Highlighted

BACKGROUND

By determining the hepatitis B virus (HBV) surface antigen (HBsAg) positive rate postexposure and HBV-specific antigen/antibody (Ag/Ab) level in patients with rheumatic diseases, we aimed at exploring the rheumatic link to HBV control.

METHODS

Patients who underwent HBV screening in the Ruijin Hospital from 2020 to 2021 were enrolled for the exposure rate estimation. Among antibody to HBV core antigen (HBcAb)-positive patients, we adopted propensity score matching (PSM) to study the impact of rheumatism on HBsAg seroprevalence after exposure. A second PSM evaluated the Ag/Ab differences. We also had HBsAg prevalence in human leukocyte antigen B2 (HLA-B27) tested patients studied.

RESULTS

With 33,989 screened patients, exposure rates remained comparable between rheumatic and non-rheumatic patients: 48.94 vs. 49.86%. PSM first yielded 2,618 balanced pairs. We observed significantly fewer patients with rheumatic diseases in HBsAg positive cases than negative ones (p < 0.001). In the second round, PSM matched 279 pairs, HBsAg (p < 0.001) and HBeAg (p < 0.05) positivity rates were significantly lower in the rheumatic patients, whereas HBsAb positivity rate (p < 0.001) and level (p < 0.01) were significantly higher. Though the value of HBcAb was overall significantly lower (p < 0.001) within the realm of rheumatic diseases, patients with ankylosing spondylitis (AS) demonstrated a significantly higher value than other rheumatic diseases. We saw significantly fewer HBV infections in HLA-B27 positive subjects than in the negative ones (p < 0.001).

CONCLUSION

In this propensity score-matched study, rheumatic patients had an advantage in HBV control. In rheumatic patients, HBcAb levels, together with the beneficial role of HLA-B27, were highlighted.

Innate and Adaptive Immunopathogeneses in Viral Hepatitis; Crucial Determinants of Hepatocellular Carcinoma

Viral hepatitis B (HBV) and hepatitis C (HCV) infections remain the most common risk factors for the development of hepatocellular carcinoma (HCC), and their heterogeneous distribution influences the global prevalence of this common type of liver cancer. Typical hepatitis infection elicits various immune responses within the liver microenvironment, and viral persistence induces chronic liver inflammation and carcinogenesis. HBV is directly mutagenic but can also cause low-grade liver inflammation characterized by episodes of intermittent high-grade liver inflammation, liver fibrosis, and cirrhosis, which can progress to decompensated liver disease and HCC. Equally, the absence of key innate and adaptive immune responses in chronic HCV infection dampens viral eradication and induces an exhausted and immunosuppressive liver niche that favors HCC development and progression. The objectives of this review are to (i) discuss the epidemiological pattern of HBV and HCV infections, (ii) understand the host immune response to acute and chronic viral hepatitis, and (iii) explore the link between this diseased immune environment and the development and progression of HCC in preclinical models and HCC patients.

Intrahepatic immune infiltrate in chronic hepatitis B and chronic hepatitis C: Similar but not the same

In chronic hepatitis B (CHB) and C (CHC) infections, the composition of the immune cell microenvironment at the site of infection is poorly understood. Thus, our aim was to characterize and compare liver infiltrates to identify shared and exclusive hepatic immune components. Immunohistochemistry was performed on 26 CHB and 42 CHC liver biopsies to determine Th (CD4+), Th1 (T-bet+), Th17 (IL-17A+), Treg (Foxp3+) and CTL (CD8+) cells frequency in portal/periportal and intralobular areas and relate them to liver damage. CHB and CHC cases shared a portal/periportal CD4+ lymphocyte predominance and a lobular CD8+ lymphocyte majority. However, CHC exhibited a concomitant lobular T-bet+ cell dominance while in CHB FoxP3+ cells prevail. CHC disclosed higher frequencies of P/P FoxP3+, IL-17A+ and T-bet+ cells and intralobular CD4+, IL-17A+ and T-bet+ lymphocytes. HBeAg+ chronic hepatitis and CHC cell frequencies were similar except for lobular T-bet+ that remained higher among CHC cases. Comparison among cases with less severe liver disease revealed lower lymphocyte frequencies in CHB samples, while no differences were observed between patients with more severe stages. Interestingly, in CHB portal/periportal CD4+ and lobular CD4+, CD8+ and IL-17A+ cells were associated with severe hepatitis. Even when all studied populations were identified in both infections preferential lymphocyte frequencies and prevalence at different areas along with their association with liver damage highlighted that CHB and CHC immune responses are not the same.

Pathogenicity and virulence of Hepatitis B virus

Hepatitis B virus (HBV) is a hepatotropic virus and an important human pathogen. There are an estimated 296 million people in the world that are chronically infected by this virus, and many of them will develop severe liver diseases including hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HBV is a small DNA virus that replicates via the reverse transcription pathway. In this review, we summarize the molecular pathways that govern the replication of HBV and its interactions with host cells. We also discuss viral and non-viral factors that are associated with HBV-induced carcinogenesis and pathogenesis, as well as the role of host immune responses in HBV persistence and liver pathogenesis.

Microbiota-Meditated Immunity Abnormalities Facilitate Hepatitis B Virus Co-Infection in People Living With HIV: A Review

Hepatitis B virus (HBV) co-infection is fairly common in people living with HIV (PLWH) and affects millions of people worldwide. Identical transmission routes and HIV-induced immune suppression have been assumed to be the main factors contributing to this phenomenon. Moreover, convergent evidence has shown that people co-infected with HIV and HBV are more likely to have long-term serious medical problems, suffer more from liver-related diseases, and have higher mortality rates, compared to individuals infected exclusively by either HIV or HBV. However, the precise mechanisms underlying the comorbid infection of HIV and HBV have not been fully elucidated. In recent times, the human gastrointestinal microbiome is progressively being recognized as playing a pivotal role in modulating immune function, and is likely to also contribute significantly to critical processes involving systemic inflammation. Both antiretroviral therapy (ART)-naïve HIV-infected subjects and ART-treated individuals are now known to be characterized by having gut microbiomic dysbiosis, which is associated with a damaged intestinal barrier, impaired mucosal immunological functioning, increased microbial translocation, and long-term immune activation. Altered microbiota-related products in PLWH, such as lipopolysaccharide (LPS) and short-chain fatty acids (SCFA), have been associated with the development of leaky gut syndrome, favoring microbial translocation, which in turn has been associated with a chronically activated underlying host immune response and hence the facilitated pathogenesis of HBV infection. Herein, we critically review the interplay among gut microbiota, immunity, and HIV and HBV infection, thus laying down the groundwork with respect to the future development of effective strategies to efficiently restore normally diversified gut microbiota in PLWH with a dysregulated gut microbiome, and thus potentially reduce the prevalence of HBV infection in this population.