A randomized controlled phase IIb trial of antigen-antibody immunogenic complex therapeutic vaccine in chronic hepatitis B patients

Development of High-Titer Antidrug Antibodies in a Phase 1b/2a Infant Clesrovimab Trial Are Associated With RSV Exposure Beyond Day 150

BACKGROUND

Clesrovimab is a human half-life-extended monoclonal antibody in phase 3 evaluation for the prevention of respiratory syncytial virus (RSV) disease in infants. Antidrug antibodies (ADA) were observed at late time points in a phase 1b/2a study where clesrovimab was well tolerated with an extended half-life of approximately 45 days.

METHODS

Serum samples at days 150, 365, and 545 postdose were assayed for ADA titers. Samples with high ADA titers were characterized for their binding specificity to the Fab or the YTE portion of clesrovimab. RSV serum neutralization (SNA) titers were also measured on ADA-positive and ADA-negative infants. Additionally, a D25 (site Ø) competitive enzyme-linked immunosorbent assay (ELISA) was performed on ADA-positive available samples to determine RSV exposure. Local surveillance data was used to ascertain RSV circulation during the trial.

RESULTS

High ADA titers were observed in a minority of infants at days 365 and 545 for all doses tested. Additionally, all high-titer ADA-positive infants had ADA directed towards the YTE epitope of clesrovimab. Moreover, these infants demonstrated robust RSV-SNA and had D25 competitive antibodies suggesting an RSV exposure after day 150, coinciding with the epidemiological data.

CONCLUSIONS

RSV exposure in infants beyond day 150 after dosing is associated with ADA development and high RSV-SNA titers with no impact on pharmacokinetics.

CLINICAL TRIALS REGISTRATION

NCT03524118.

Unveiling the nexus: The tumor microenvironment as a strategic frontier in viral cancers

Viral infections are a significant factor in the etiology of various cancers, with the tumor microenvironment (TME) playing a crucial role in disease progression. This review delves into the complex interactions between viruses and the TME, highlighting how these interactions shape the course of viral cancers. We explore the distinct roles of immune cells, including T-cells, B-cells, macrophages, and dendritic cells, within the TME and their influence on cancer progression. The review also examines how viral oncoproteins manipulate the TME to promote immune evasion and tumor survival. Unraveling these mechanisms highlights the emerging paradigm of targeting the TME as a novel approach to cancer treatment. Our analysis provides insights into the dynamic interplay between viruses and the TME, offering a roadmap for innovative treatments that leverage the unique characteristics of viral cancers.

Efficacy and safety of therapeutic vaccines for the treatment of chronic hepatitis B: A systematic review and meta-analysis of randomized controlled trials update

BACKGROUND

Most people diagnosed with chronic hepatitis B (CHB) need treatment to help reduce the risk of liver disease and limit disease transmission. Therapeutic vaccine (TV) candidates have been under study for their clinical effects on inducing HBV-specific host immune responses. This review aimed to systematically synthesize updated evidence on the efficacy and safety of TVs in patients with CHB.

METHODS

This systematic review was performed by searching different databases from January to February 2021. Completed randomized controlled trials that reported TVs' efficacy and/or safety for treating CHB compared with the standard of care (SOC) or placebo were included. Efficacy and safety estimates were reported as the logarithm of the odds ratio and risk differences, respectively. I2 > 50% was considered significant heterogeneity. Significant publication bias was considered when Egger's test P value < .10. The risk of bias was assessed using the Cochrane Risk of Bias tool. The GRADE methodology was used to assess the certainty of the evidence for each outcome.

RESULTS

Twenty-four articles with 2889 pooled samples were included. TVs made a significant difference in hepatitis B envelope antigen (HBeAg) SC (log OR = 0.76, P = .01) and (log OR = 0.40, P = .03) compared to placebo and combination therapy, respectively. HBeAg SC was significantly affected by TVs at the end of follow up (log OR = 0.49, P = .01), with significant HBsAg mean difference (MD = -0.62, P = .00). At the end of treatment, the TVs had no significant effect on HBV DNA negativity over the SOC (log OR = 0.62, P = .09) or placebo (log OR = -0.07, P = .91). TVs do not significantly affect the risk of serious adverse events (RD 0.02, 95% CI 0.00-0.04).

CONCLUSION

In patients with CHB, TVs had significant effects on HBeAg SC compared to the SOC or placebo. There was no significant difference between serious adverse events. TVs are promising treatment strategy to overcome CHB.

Contriving a novel of CHB therapeutic vaccine based on IgV_CTLA-4 and L protein via immunoinformatics approach

Chronic infection induced by immune tolerance to hepatitis B virus (HBV) is one of the most common causes of hepatic cirrhosis and hepatoma. Fortunately, the application of therapeutic vaccine can not only reverse HBV-tolerance, but also serve a potentially effective therapeutic strategy for treating chronic hepatitis B (CHB). However, the clinical effect of the currently developed CHB therapeutic vaccine is not optimistic due to the weak immunogenicity. Given that the human leukocyte antigen CTLA-4 owns strong binding ability to the surface B7 molecules (CD80 and CD86) of antigen presenting cell (APCs), the immunoglobulin variable region of CTLA-4 (IgV_CTLA-4) was fused with the L protein of HBV to contrive a novel therapeutic vaccine (V_C4HBL) for CHB in this study. We found that the addition of IgV_CTLA-4 did not interfere with the formation of L protein T cell and B cell epitopes after analysis by means of immunoinformatics approaches. Meanwhile, we also found that the IgV_CTLA-4 had strong binding force to B7 molecules through molecular docking and molecular dynamics (MD) simulation. Notably, our vaccine V_C4HBL showed good immunogenicity and antigenicity by in vitro and in vivo experiments. Therefore, the V_C4HBL is promising to again effectively activate the cellular and humoral immunity of CHB patients, and provides a potentially effective therapeutic strategy for the treatment of CHB in the future.Communicated by Ramaswamy H. Sarma.

The potential effect of HBV vaccination on off-treatment HBsAg reversion after interferon-induced HBsAg clearance

Off-treatment HBsAg reversion occurs in a considerable number of chronic hepatitis B(CHB) patients after IFN(interferon)-induced HBsAg clearance. HBV vaccination protects the general population against HBV infection. However, it remains unclear whether HBV vaccination could prevent off-treatment HBsAg reversion in CHB patients with HBsAg clearance. CHB patients (n = 199) with HBsAg clearance were included in the current study, comprising spontaneous HBsAg clearance group (n = 51), NA (nucleoside/nucleotide analogues)-induced group (n = 36) and IFN-induced group (n = 112). Log-rank test was performed to compare the cumulative incidences of HBsAg reversion between groups. Cox regression model was used to identify the factors associated with off-treatment HBsAg reversion. The 5-year cumulative incidence of HBsAg reversion in IFN-induced group was significantly higher than that in NA-induced group or spontaneous group (27.6% vs. 3.3% vs. 8.1%, both p < .05). In IFN-induced group, 66.7% of CHB patients received HBV vaccination. The cumulative incidence of HBsAg reversion in individuals with strong responses to HBV vaccination (HBsAb level >100mIU/ml) was significantly lower than that in those with weak responses to HBV vaccination (HBsAb level ≤100mIU/ml) or without HBV vaccination in IFN-induced group (7.7% vs. 58.5% vs. 31.9%, both p < .05). Multivariate Cox regression analysis confirmed strong responses to HBV vaccination were independently associated with a lower cumulative incidence of HBsAg reversion after IFN-induced HBsAg clearance (HR = 0.246, 95%CI: 0.066-0.907, p = .035). HBV vaccination has potential to prevent off-treatment HBsAg reversion in CHB patients after IFN-induced HBsAg clearance via a sufficiently high level of HBsAb, helping clinicians optimize the clinical management of such patients.

Immune therapies against chronic hepatitis B

Patients with chronic hepatitis B (CHB) represent a living and permanent reservoir of hepatitis B virus (HBV). Millions of these CHB patients will eventually develop complications such as liver cirrhosis, hepatic failure, and hepatocellular carcinoma if they are not treated properly. Accordingly, several antiviral drugs have been developed for the treatment of CHB, but these drugs can neither eradicate all forms of HBV nor contain the progression of complications in most patients with CHB. Thus, the development of new and novel therapeutics for CHB remains a pressing need. The molecular and cellular mechanisms underlying the pathogenesis of CHB indicate that immune dysregulations may be responsible for HBV persistence and progressive liver damage in CHB. This provided the scientific and ethical basis for the immune therapy of CHB patients. Around 30 years have passed since the initiation of immune therapies for CHB in the early 1990s, and hundreds of clinical trials have been accomplished to substantiate this immune treatment. Despite these approaches, an acceptable regimen of immune therapy is yet to be realized. However, most immune therapeutic agents are safe for human usage, and many of these protocols have inspired considerable optimism. In this review, the pros and cons of different immune therapies, observed in patients with CHB during the last 30 years, will be discussed to derive insights into the development of an evidence-based, effective, and patient-friendly regimen of immune therapy for the treatment of CHB.

Role of anti-HBs in functional cure of HBeAg+ chronic hepatitis B patients infected with HBV genotype A

BACKGROUND & AIMS

HBsAg-specific antibody responses are difficult to detect during chronic hepatitis B infection (CHB) and are often overlooked. The aim of this study was to examine whether anti-HBs may be involved in functional cure (FC) by profiling anti-HBs responses in patients with CHB using a panel of specific assays.

METHODS

Longitudinal serum samples were obtained from 25 patients with CHB who were infected with HBV genotype A and were undergoing nucleos(t)ide analogue (NA) treatment: 14 achieved FC while 11 remained infected (non-FC). Anti-HBs immune complexes (HBsAg-IC), FcγRIIIa dimer binding, epitope specificity and neutralisation efficacy were measured.

RESULTS

HBsAg-IC peaks were detected prior to HBsAg loss in 10/14 FC patients. These HBsAg-IC peaks overlapped with either an alanine aminotransferase (ALT) flare (8/10 patients), or a rise in ALT (2/10 patients). HBsAg-IC peaks were detected in 7/11 non-FC patients, but were not associated with an ALT flare. FCγRIIIa binding was detected in 9/14 FC patients, independent from detection of overlapping HBsAg-IC/ALT peaks. FC patients had stable HBsAg epitope occupancy across the study, whereas non-FC patients had a reduction in HBsAg epitope occupancy within the first 12-24 weeks of NA treatment. Convalescent sera from FC patients recognised more HBsAg epitopes and neutralised HBV infection more potently than anti-HBs derived from vaccinees. Neutralisation potency appeared to increase post-HBsAg loss in 4/5 FC patients examined.

CONCLUSIONS

Using these assays, we confirm that anti-HBs responses are present and fluctuate over time in this cohort of patients with HBeAg+ CHB, who were infected with HBV genotype A and treated with NAs. Key anti-HBs profiles associated with either FC or failure to achieve FC were also identified, suggesting a role for anti-HBs responses in FC.

LAY SUMMARY

Using a panel of assays to characterise hepatitis B surface antibody (anti-HBs) responses in a group of patients with chronic hepatitis B, we identified anti-HBs profiles associated with either functional cure, or failure to achieve functional cure. Functional cure was associated with immune complex peaks which overlapped with alanine aminotransferase flares. Conversely, in those who did not achieve functional cure, immune complex peaks were present, but were not associated with alanine aminotransferase flares, and a decline in anti-HBs diversity was observed early during treatment.

The Safety and Efficacy of a Therapeutic Vaccine for Chronic Hepatitis B: A Follow-Up Study of Phase III Clinical Trial

The objective of the present study was to assess the safety and efficacy of a therapeutic vaccine containing both HBsAg and HBcAg (NASVAC) in patients with chronic hepatitis B (CHB) three years after the end of treatment (EOT) as a follow-up of a phase III clinical trial. NASVAC was administered ten times by the nasal route and five times by subcutaneous injection. A total of 59 patients with CHB were enrolled. Adverse events were not seen in any of the patients. Out of the 59 CHB patients, 54 patients exhibited a reduction in HBV DNA, compared with their basal levels. Although all the patients had alanine transaminase (ALT) above the upper limit of normal (>42 IU/L) before the commencement of therapy, the levels of ALT were within the ULN level in 42 patients. No patient developed cirrhosis of the liver. The present study, showing the safety and efficacy of NASVAC 3 years after the EOT, is the first to report follow-up data of an immune therapeutic agent against CHB. NASVAC represents a unique drug against CHB that is safe, of finite duration, can be administered by the nasal route, is capable of reducing HBV DNA and normalizing ALT, and contains hepatic fibrosis.

Sustained Antiviral and Liver Protection by a Nasal Therapeutic Vaccine (NASVAC, Containing Both HBsAg and HBcAg) in Patients with Chronic Hepatitis B: 2-Year Follow-Up of Phase III Clinical Trial

A phase III clinical trial in treatment-naïve patients with chronic hepatitis B (CHB) revealed the safety and considerable therapeutic efficacy of a vaccine containing both hepatitis B surface antigen (HBsAg) and hepatitis B core antigen (HBcAg) (NASVAC) at the end of treatment (EOT) and 24 weeks after EOT. Two years after EOT, we checked HBV DNA, alanine aminotransferase (ALT), and hepatitis B e antigen (HBeAg). The data reveal that 33 of 66 NASVAC-recipient CHB patients became negative for HBV DNA in the blood two years after EOT. The ALT levels were within the upper limit of normal (ULN) in 37 patients, although all 66 CHB patients had elevated ALT (above ULN) before the start of therapy. Out of the total twelve HBeAg-positive patients, eight patients became negative for HBeAg. None of the patients developed cirrhosis of the liver within this period. NASVAC is a finite treatment regimen with sustained antiviral and liver-protecting properties. This study is the first to report follow-up data of immune therapy for CHB. NASVAC, an immune therapy of finite duration, is endowed with sustained antiviral and liver protection properties in CHB patients.

Exploring evidence-based innovative therapy for the treatment of chronic HBV infection: experimental and clinical

With the advent of various vaccines and antimicrobial agents during the 20th century, the control and containment of infectious diseases appeared to be a matter of time. However, studies unveiled the diverse natures of microbes, their lifestyle, and pathogenetic potentials. Since the ground-breaking discovery of the hepatitis B virus (HBV) by Baruch Blumberg and the subsequent development of a vaccine in the early 1980s, the main task of the scientific community has been to develop a proper management strategy for HBV-induced chronic liver diseases. In the early 1980’s, standard interferon (IFN) induced a reduction of HBV DNA levels, followed by the normalization of serum transaminases (alanine aminotransferase, ALT), in some chronic hepatitis B (CHB) patients. However, in the course of time, the limitations of standard IFN became evident, and the search for an alternative began. In the late 1980’s, nucleoside analogs entered the arena of CHB treatment as oral drugs with potent antiviral capacities. At the beginning of the 21st century, insights were developed into the scope and limitations of standard IFN, pegylated-IFN as well as nucleoside analogs for treating CHB. Considering the non-cytopathic nature of the HBV, the presence of covalently closed circular DNA (cccDNA) in the nucleus of the infected hepatocytes and HBV-induced immune-mediated liver damages, a new field of CHB management was initiated by modulating the hosts’ immune system through immune therapy. This review will discuss the nature and design of innovative immune therapy for CHB.

Therapeutic vaccination for treatment of chronic hepatitis B

Chronic hepatitis B infection remains a serious global health threat, contributing to a large number of deaths through liver cirrhosis and hepatocellular carcinoma. Current treatment does not eradicate disease, and therefore new treatments are urgently needed. In acute hepatitis B virus (HBV) a strong immune response is necessary to clear the virus, but in chronic infection the immune response is weakened and dysfunctional. Therapeutic vaccination describes the process of inoculating individuals with a non‐infective form of viral antigen with the aim of inducing or boosting existing HBV‐specific immune responses, resulting in sustained control of HBV infection. In this review we outline the rationale for therapeutic vaccination in chronic HBV infection, discuss previous and ongoing trials of novel HBV therapeutic vaccine candidates and outline strategies to improve vaccine efficacy going forward.

Toward a new era of hepatitis B virus therapeutics: The pursuit of a functional cure

Hepatitis B virus (HBV) infection, although preventable by vaccination, remains a global health problem and a major cause of chronic liver disease. Although current treatment strategies suppress viral replication very efficiently, the optimal endpoint of hepatitis B surface antigen (HBsAg) clearance is rarely achieved. Moreover, the thorny problems of persistent chromatin-like covalently closed circular DNA and the presence of integrated HBV DNA in the host genome are ignored. Therefore, the scientific community has focused on developing innovative therapeutic approaches to achieve a functional cure of HBV, defined as undetectable HBV DNA and HBsAg loss over a limited treatment period. A deeper understanding of the HBV life cycle has led to the introduction of novel direct-acting antivirals that exert their function through multiple mechanisms, including inhibition of viral entry, transcriptional silencing, epigenetic manipulation, interference with capsid assembly, and disruption of HBsAg release. In parallel, another category of new drugs aims to restore dysregulated immune function in chronic hepatitis B accompanied by lethargic cellular and humoral responses. Stimulation of innate immunity by pattern-recognition receptor agonists leads to upregulation of antiviral cytokine expression and appears to contribute to HBV containment. Immune checkpoint inhibitors and adoptive transfer of genetically engineered T cells are breakthrough technologies currently being explored that may elicit potent HBV-specific T-cell responses. In addition, several clinical trials are attempting to clarify the role of therapeutic vaccination in this setting. Ultimately, it is increasingly recognized that elimination of HBV requires a treatment regimen based on a combination of multiple drugs. This review describes the rationale for progressive therapeutic interventions and discusses the latest findings in the field of HBV therapeutics.

Immune Complex Vaccine Strategies to Combat HIV-1 and Other Infectious Diseases

Immune complexes (ICs) made of antibody-bound antigens exhibit immunomodulatory activities exploitable in a vaccination strategy to optimize vaccine efficacy. The modulatory effects of ICs are typically attributed to the Fc fragments of the antibody components, which engage Fc receptors, complement and complement receptors on various immune cells. These Fc-mediated functions facilitate the critical interplay between innate and adaptive immune systems to impact the quality and quantity of the elicited adaptive responses. In addition to the Fc contribution, the Fab fragment also plays an immunoregulation role. The antigen-binding domains of the Fab fragment can bind their specific epitopes at high affinity to sterically occlude these antigenic sites from recognition by other antibodies. Moreover, the Fab-mediated binding has been demonstrated to induce allosteric alterations at nearby or distant antigenic sites. In this review article, we survey published studies to illuminate how the immunomodulatory functions of ICs have been investigated or utilized in a vaccination strategy to fight against an array of infectious pathogens, culminating with IC vaccine designs aimed at preventing HIV-1 infection. In particular, we highlight IC vaccine candidates that exploit Fab-mediated steric and allosteric effects to direct antibody responses away or toward the V1V2 domain, the V3 loop, and other antigenic sites on the HIV-1 envelope gp120 glycoprotein. Like other HIV-1 vaccine approaches, the path for IC-based vaccines to reach the clinic faces major hurdles yet to be overcome; however, investigations into this vaccine strategy have provided insights into the multifaceted activities of antibodies beyond their conventional roles in the host defense against HIV-1 and other microbial pathogens.

Designing the next-generation therapeutic vaccines to cure chronic hepatitis B: focus on antigen presentation, vaccine properties and effect measures

In the mid‐90s, hepatitis B virus (HBV)‐directed immune responses were for the first time investigated in detail and revealed suboptimal T‐cell responses in chronic HBV patients. Based on these studies, therapeutic vaccination exploiting the antigen presentation capacity of dendritic cells to prime and/or boost HBV‐specific T‐cell responses was considered highly promising. Now, 25 years later, it has not yet delivered this promise. In this review, we summarise what has been clinically tested in terms of antigen targets and vaccine forms, how the immunological and therapeutic effects of these vaccines were assessed and what major clinical and immunological findings were reported. We combine the lessons learned from these trials with the most recent insights on HBV antigen presentation, T‐cell responses, vaccine composition, antiviral and immune‐modulatory drugs and disease biomarkers to derive novel opportunities for the next generation of therapeutic vaccines designed to cure chronic HBV either alone or in combination therapy.

Prophylactic and therapeutic HBV vaccination by an HBs-expressing cytomegalovirus vector lacking an interferon antagonist in mice

Cytomegalovirus (CMV)-based vaccines show promising effects against chronic infections in nonhuman primates. Therefore, we examined the potential of hepatitis B virus (HBV) vaccines based on mouse CMV (MCMV) vectors expressing the small HBsAg. Immunological consequences of vaccine virus attenuation were addressed by either replacing the dispensable gene m157 ("MCMV-HBsȍ) or the gene M27 ("ΔM27-HBs"), the latter encodes a potent IFN antagonist targeting the transcription factor STAT2. M27 was chosen, since human CMV encodes an analogous gene product, which also induced proteasomal STAT2 degradation by exploiting Cullin RING ubiquitin ligases. Vaccinated mice were challenged with HBV through hydrodynamic injection. MCMV-HBs and ΔM27-HBs vaccination achieved accelerated HBV clearance in serum and liver as well as robust HBV-specific CD8⁺ T-cell responses. When we explored the therapeutic potential of MCMV-based vaccines, especially the combination of ΔM27-HBs prime and DNA boost vaccination resulted in increased intrahepatic HBs-specific CD8⁺ T-cell responses and HBV clearance in persistently infected mice. Our results demonstrated that vaccines based on a replication competent MCMV attenuated through the deletion of an IFN antagonist targeting STAT2 elicit robust anti-HBV immune responses and mediate HBV clearance in mice in prophylactic and therapeutic immunization regimes.

Recent Advances in Understanding, Diagnosing, and Treating Hepatitis B Virus Infection

Chronic hepatitis B virus (HBV) infection affects 292 million people worldwide and is associated with a broad range of clinical manifestations including cirrhosis, liver failure, and hepatocellular carcinoma (HCC). Despite the availability of an effective vaccine HBV still causes nearly 900,000 deaths every year. Current treatment options keep HBV under control, but they do not offer a cure as they cannot completely clear HBV from infected hepatocytes. The recent development of reliable cell culture systems allowed for a better understanding of the host and viral mechanisms affecting HBV replication and persistence. Recent advances into the understanding of HBV biology, new potential diagnostic markers of hepatitis B infection, as well as novel antivirals targeting different steps in the HBV replication cycle are summarized in this review article.

Targeting HIV Env immunogens to B cell follicles in nonhuman primates through immune complex or protein nanoparticle formulations

Following immunization, high-affinity antibody responses develop within germinal centers (GCs), specialized sites within follicles of the lymph node (LN) where B cells proliferate and undergo somatic hypermutation. Antigen availability within GCs is important, as B cells must acquire and present antigen to follicular helper T cells to drive this process. However, recombinant protein immunogens such as soluble human immunodeficiency virus (HIV) envelope (Env) trimers do not efficiently accumulate in follicles following traditional immunization. Here, we demonstrate two strategies to concentrate HIV Env immunogens in follicles, via the formation of immune complexes (ICs) or by employing self-assembling protein nanoparticles for multivalent display of Env antigens. Using rhesus macaques, we show that within a few days following immunization, free trimers were present in a diffuse pattern in draining LNs, while trimer ICs and Env nanoparticles accumulated in B cell follicles. Whole LN imaging strikingly revealed that ICs and trimer nanoparticles concentrated in as many as 500 follicles in a single LN within two days after immunization. Imaging of LNs collected seven days postimmunization showed that Env nanoparticles persisted on follicular dendritic cells in the light zone of nascent GCs. These findings suggest that the form of antigen administered in vaccination can dramatically impact localization in lymphoid tissues and provides a new rationale for the enhanced immune responses observed following immunization with ICs or nanoparticles.

The role of hepatitis B surface antibodies in HBV infection, disease and clearance

The clinical sequelae associated with chronic HBV infection is generally regarded as a consequence of an inadequate and inappropriate immune response to active viral replication, predominantly at the T-cell level. However, recent studies on hepatitis B surface antigen (HBsAg)-specific B cells and hepatitis B surface antibody (anti-HB) responses have identified their previously unrecognized role in the pathogenesis of chronic hepatitis B (CHB). These studies have also uncovered novel therapeutic approaches to more effectively target HBsAg loss and seroconversion, an important end point and regarded as a functional cure. Anti-HBs IgG has also been shown to have multiple direct acting antiviral roles with the Fab component directly blocking viral entry, and release while the Fc component has been linked to antibody dependent cellular cytotoxicity. Likewise, the HBsAg-specific B-cell dysfunctionality can be reversed providing new therapeutic opportunities to achieve functional cure in CHB.

Advances in Targeting the Innate and Adaptive Immune Systems to Cure Chronic Hepatitis B Virus Infection

“Functional cure” is being pursued as the ultimate endpoint of antiviral treatment in chronic hepatitis B (CHB), which is characterized by loss of HBsAg whether or not anti-HBs antibodies are present. “Functional cure” can be achieved in <10% of CHB patients with currently available therapeutic agents. The dysfunction of specific immune responses to hepatitis B virus (HBV) is considered the major cause of persistent HBV infection. Thus, modulating the host immune system to strengthen specific cellular immune reactions might help eliminate HBV. Strategies are needed to restore/enhance innate immunity and induce HBV-specific adaptive immune responses in a coordinated way. Immune and resident cells express pattern recognition receptors like TLRs and RIG I/MDA5, which play important roles in the induction of innate immunity through sensing of pathogen-associated molecular patterns (PAMPs) and bridging to adaptive immunity for pathogen-specific immune control. TLR/RIG I agonists activate innate immune responses and suppress HBV replication in vitro and in vivo, and are being investigated in clinical trials. On the other hand, HBV-specific immune responses could be induced by therapeutic vaccines, including protein (HBsAg/preS and HBcAg), DNA, and viral vector-based vaccines. More than 50 clinical trials have been performed to assess therapeutic vaccines in CHB treatment, some of which display potential effects. Most recently, using genetic editing technology to generate CAR-T or TCR-T, HBV-specific T cells have been produced to efficiently clear HBV. This review summarizes the progress in basic and clinical research investigating immunomodulatory strategies for curing chronic HBV infection, and critically discusses the rather disappointing results of current clinical trials and future strategies.

Therapeutic efficacy of hepatitis B virus vaccine in treatment of chronic HBV infections: A systematic review and meta-analysis

There is a need for improved treatment of patients with chronic hepatitis B (CHB). We reviewed the literature to explore the efficacy of HB vaccines alone or in combination therapy (CT) with antiviral drugs in CHB patients and to meta-analyze data from randomized controlled trials. We conducted a systematic search in ten databases. All studies investigating the efficacy of HBV vaccine in HBV infected patients were included with no restrictions. Among 1359 studies initially identified, 23 studies (n = 1956 patients) were included for the final analysis. CT showed a significant reduction of HBV DNA compared with analogue monotherapy (AM) at the 12-month follow-up period (odds ratio (OR) = 2.835, 95% confidence interval (CI) [1.275, 6.306], p = .011). Additionally, CT also remarkably induce HbsAg loss in comparison with AM (OR = 11.736, 95% CI [1.841, 74.794], p = .009). Our pooled data revealed no difference between treatment and control regarding alanine aminotransferase normalization, HBeAg seroconversion, and HBeAg disappearance. In addition, CT using vaccine and NAs resulted in a statistically significant higher incidence of adverse effects than AM. The therapeutic effects of combination therapy for patients with CHB were encouraging, but future studies need to investigate all possible treatment combinations and assess their cost-effectiveness.

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.

Toward a Functional Cure for Hepatitis B: The Rationale and Challenges for Therapeutic Targeting of the B Cell Immune Response

The central role of the cellular immune response in the control and clearance of the hepatitis B virus (HBV) infection has been well-established. The contribution of humoral immunity, including B cell and antibody responses against HBV, has been investigated for a long time but has attracted increasing attention again in recent years. The anti-HBs antibody was first recognized as a marker of protective immunity after the acute resolution of the HBV infection (or vaccination) and is now defined as a biomarker for the functional cure of chronic hepatitis B (CHB). In this way, therapies targeting HBV-specific B cells and the induction of an anti-HBs antibody response are essential elements of a rational strategy to terminate chronic HBV infection. However, a high load of HBsAg in the blood, which has been proposed to induce antigen-specific immune tolerance, represents a major obstacle to curing CHB. Long-term antiviral treatment by nucleoside analogs, by targeting viral translation by siRNA, by inhibiting HBsAg release via nucleic acid polymers, or by neutralizing HBsAg via specific antibodies could potentially reduce the HBsAg load in CHB patients. A combined strategy including a reduction of the HBsAg load via the above treatments and the therapeutic targeting of B cells by vaccination may induce the appearance of anti-HBs antibodies and lead to a functional cure of CHB.

Therapeutic vaccination for chronic hepatitis B: A systematic review and meta-analysis

Therapeutic vaccines may be promising treatments for chronic hepatitis B (CHB), but their clinical efficacy and safety are unclear. We conducted a systematic review of the evidence for the efficacy and safety of therapeutic vaccines in CHB patients. We searched PubMed, EMBASE and Google Scholar from 1990 until present and abstracts from EASL, APASL and AASLD from 2012 to 2017 and selected randomized controlled trials of CHB patients, comparing therapeutic vaccines with no treatment or standard of care. The Cochrane Risk of Bias tool v2.0 and GRADE method were used. Analyses were stratified by hepatitis B e antigen (HBeAg) status and the comparator (therapeutic vaccines vs no treatment, or therapeutic vaccines + standard of care vs standard of care). Efficacy outcomes were HBeAg seroconversion, hepatitis B virus DNA reduction and hepatitis B virus surface antigen (HBsAg) loss, measured at the end of treatment or end of follow-up. Effects were reported as risk differences with 95% confidence intervals using a random effects model. Fifteen studies were included. A wide variety of therapeutic vaccines were tested. For HBeAg clearance at the end of follow-up, when comparing therapeutic vaccines vs no therapy, RD = 0.01, 95% CI -0.05 to 0.07, and when comparing therapeutic vaccines + standard of care vs standard of care, RD = 0.03, 95% CI -0.03 to 0.09. For HBVDNA reduction at the end of follow-up, when comparing therapeutic vaccines vs no therapy, RD = -0.03, 95% CI -0.08 to 0.02, and when comparing therapeutic vaccines + standard of care, RD = 0.15, 95% CI 0.02-0.28. There were only a few studies on HBsAg loss, and hence, the findings were inconclusive. The only efficacy finding was HBVDNA reduction at the end of follow-up for therapeutic vaccines + standard of care vs standard of care; otherwise, therapeutic vaccines do not appear to be efficacious for the treatment of CHB, but were limited by few RCTs, suboptimal therapeutic vaccines and patient selection.

From therapeutic antibodies to immune complex vaccines

In recent years, therapeutic monoclonal antibodies have made impressive progress, providing great benefit by successfully treating malignant and chronic inflammatory diseases. Monoclonal antibodies with broadly neutralizing effects against specific antigens, or that target specific immune regulators, manifest therapeutic effects via their Fab fragment specificities. Subsequently therapeutic efficacy is mediated mostly by interactions of the Fc fragments of the antibodies with their receptors (FcR) displayed on cells of the immune system. These interactions can trigger a series of immunoregulatory responses, involving both innate and adaptive immune systems and including cross-presentation of antigens, activation of CD₈⁺ T cells and CD₄⁺ T cells, phagocytosis, complement-mediated antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). The nature of the triggered effector functions of the antibodies is markedly affected by the glycosylation patterns of the Fc fragments. These can cause differences in the conformation of the heavy chains of antibodies, with resultant changes in antibody binding affinity and activation of the complement system. Studies of the Fc glycosylation profiles together with the associated Fc effector functions and FcR/CR interactions promoted interest and progress in engineering therapeutic antibodies. Furthermore, because antigen–antibody immune complexes (ICs) have shown similar actions, in addition to certain novel immunoregulatory mechanisms that also reshape immune responses, the properties of ICs are being explored in new approaches for prevention and therapy of diseases. In this review, both basic studies and experimental/clinical applications of ICs leading to the development of preventive and therapeutic vaccines are presented.

Multiple doses of hepatitis B recombinant vaccine for chronic hepatitis B patients with low surface antigen levels: a pilot study

BACKGROUND

Seroclearance of hepatitis B surface antigen (HBsAg) has been rarely achieved in the treatment of chronic hepatitis B (CHB) patients. We administered HBsAg-based recombinant vaccine in patients with low HBsAg concentrations.

METHODS

Twenty hepatitis B e antigen-negative patients, with HBsAg < 1000 IU/ml, were enrolled. Vaccines were administered every 8 weeks for 48 weeks (seven doses). HBsAg levels and anti-HBs were assayed longitudinally until 48 weeks post-vaccination. HLA genotyping and cDNA microarray were performed to search for response predictors.

RESULTS

Nineteen patients completed the study. At the end of vaccination, HBsAg declined significantly (Δ = - 0.27 ± 0.49 log IU/ml, p = 0.0005). The annual decline rate was significantly greater than that of an age-, gender-, and baseline HBsAg-matched control group (Δ = - 0.18 ± 0.46 versus + 0.11 ± 0.42 log IU/ml/year; p = 0.0229). Two patients achieved HBsAg seroclearance. Fourteen had significant HBsAg decline (Δ = - 0.64 ± 0.88 log IU/ml). No significant adverse events occurred during the trial. cDNA microarray identified the top up- and down-regulated genes in responders as HLA-DQ and HLA-DMB, respectively. HLA genotyping identified HLA-DQB1*04, HLA-DRB1*04, and HLA-B*40 as predictors for non-response (p = 0.0499, 0.0152, and 0.0314, respectively).

CONCLUSIONS

In low-level HBsAg CHB patients, serial HBsAg-based vaccinations were safe, resulting in significant HBsAg decline. HLA gene expression and genotypes played a role in vaccine responsiveness (ClinicalTrials.gov Identifier: NCT01817725).

Treatment of chronic hepatitis B naïve patients with a therapeutic vaccine containing HBs and HBc antigens (a randomized, open and treatment controlled phase III clinical trial)

Context

Current drugs for chronic hepatitis B therapy have a poor efficacy in terms of post-treatment sustained viral suppression and generate important side effects during and after therapy. Therapeutic vaccination with HBV antigens is an attractive alternative to test.

Objective

Evaluating the efficacy of a therapeutic vaccine candidate (designated NASVAC) containing both hepatitis B surface antigen (HBsAg) and core antigen (HBcAg) versus pegylated interferon (Peg-IFN) in naïve chronic hepatitis B patients.

Design, setting, participants

An open phase III, randomised and treatment controlled clinical trial was conducted in a total of 160 CHB patients, allocated into two groups of 80 patients each to receive NASVAC or Peg-IFN. The vaccine formulation comprised 100 μg of each HBsAg and HBcAg, and was administered in 2 cycles of 5 doses. The control group received 48 subcutaneous injections of Peg-IFN alfa 2b, 180 μg per dose, every week, for 48 consecutive weeks.

Main outcome measure

The primary outcome measure was in relation with the proportion of patients showing reduction of the viral load under the limit of detection (250 copies/mL) after 24 weeks of treatment completion.

Results

Sustained control of HBV DNA was significantly more common in NASVAC group (p<0.05) at 24 weeks of follow up. NASVAC-induced increases of alanine aminotransferases (ALT) were detected in 85% patients after 5 nasal vaccinations, although seen in only 30% of patients receiving Peg-IFN. At the end of treatment (EOT) antiviral effect was comparable in both NASVAC and Peg-IFN groups. Clearance of Hepatitis B e antigen (HBeAg) was also more frequent in NASVAC group compared to Peg-IFN recipients. A lower progression to cirrhosis was found in NASVAC group compared to Peg-IFN group.

Conclusion

Nasvac induced a superior reduction of the viral load under the limit of detection compared to Peg-IFN treatment. It is a safe and efficacious finite alternative of antiviral treatment for CHB patients.

Trial registration

ClinicalTrials.gov NCT 01374308.

Five-year Follow-up of Chronic Hepatitis B Patients Immunized by Nasal Route with the Therapeutic Vaccine HeberNasvac

A novel therapeutic vaccine for chronic hepatitis B (CHB) treatment comprising the recombinant hepatitis B surface (HBsAg) and nucleocapsid (HBcAg) antigens has been developed. Preclinical and clinical trials (CT) evidenced safety and immunogenicity in animal models as well as in phases I, II, and III clinical trials. A phase I CT has conducted in Cuba in 6 CHB patients refractory or incomplete responders to α-IFN. Patients were immunized ten times every two weeks via. nasal spray, with 100 ug HBsAg and 100 ug HBcAg. Clinical efficacy was monitored by assessing the levels of hepatitis B virus deoxyribonucleic acid (HBV DNA), alanine aminotransferase (ALT), HBeAg, and anti-HBeAg seroconversion as well as by qualitative/ quantitative HBsAg serology during this period. After a 5 year follow-up,HBeAg loss was verified in the three HBeAg (+) patients, in two cases with seroconversion to anti-HBeAg. A reduction to undetectable viral load was observed in 5 out of 6 patients, and in two cases HBsAg seroconversion was also detected. ALT increases above the 2X upper limit of normal (ULN) were only detected in HBeAg (+) patients and associated with HBe antigen loss. All patients had stiffness levels below 7.8 KPa by Fibroscan assessment at the end of this period. Although only a few patients were enrolled in this study, it seems that HeberNasvac may maintain some of the therapeutic effects for a prolonged period. How to cite this article: Fernandez G, Sanchez AL, Jerez E, Anillo LE, Freyre F, Aguiar JA, Leon Y, Cinza Z, Diaz PA, Figueroa N, Muzio V, Nieto GG, Lobaina Y, Aguilar A, Penton E, Aguilar JC. Five-year Follow-up of Chronic Hepatitis B Patients Immunized by Nasal Route with the Therapeutic Vaccine HeberNasvac. Euroasian J Hepatogastroenterol, 2018;8(2):133-139.

Overcoming immune tolerance in chronic hepatitis B by therapeutic vaccination

The currently used nucleoside analogs (i.e. entecavir and tenofovir) with high barrier-to-resistance efficiently suppress viral replication, limit inflammation and reduce the sequelae of chronic hepatitis B, but cannot cure the disease and thus have to be applied long-term. Therapeutic vaccination as an approach to cure chronic hepatitis B has shown promising pre-clinical results, nevertheless the proof of its efficacy in clinical trials is still missing. This may be partially due to suboptimal vaccine design. A main obstacle in chronic hepatitis B, however, is the high load of viral antigens expressed and secreted, which has been proposed to cause antigen-specific immune tolerance. Reduction of the viral antigen load is therefore considered a key factor for success of immune-based therapies. Although nucleoside analogs do not reduce viral antigen expression, new antiviral strategies are becoming available. Targeting viral translation by siRNA or targeting release of HBsAg from infected hepatocytes by nucleic acid polymers both reduce the antigen load. They may be considered as pre-treatment for therapeutic vaccination to increase the potential to elicit an HBV-specific immune response able to control and cure chronic HBV infection.

Nature of Host Immunity during Hepatitis B Virus Infection and designing Immune Therapy

Hepatitis B virus (HBV) infections represent one of the major public health problems in global context. More than 2 billion people in the world have been infected with this virus at some point of time in their life and millions are chronically infected, indicating that chronic HBV-infected subjects remain as a living source of HBV transmission. The public health impact of this is tremendous. Considerable numbers of chronic HBV-infected individuals would eventually develop progressive liver diseases and their complications like hepatic failure, liver cirrhosis (LC), and hepatocellular carcinoma (HCC). Epidemiological studies have suggested that about 0.6 to 1.2 million people die annually from HBV-related liver diseases. These figures about death due to HBV and sufferings from HBV-related diseases indicate a notion of medical emergencies about HBV. In addition to these, the impact of HBV on health care delivery system moves beyond these numbers of HBV-related patients and HB-related deaths. This is because significant insights have already been developed about epidemiology, virology, and pathogenesis of HBV. Also, an effective and widely used preventive vaccine is available against HBV. In addition to these, antiviral drugs against HBV have been developed from early 1980s and several such drugs are now available commercially in the open market around the worldwide. Unfortunately, the ongoing therapeutic regimens could not stand the test of time and new insights about HBV pathogenesis are required for the development of new, novel, and evidence-based therapies for chronic HBV infections.

How to cite this article: Akbar SMF, Al-Mahtab M, Khan SI. Nature of Host Immunity during Hepatitis B Virus Infection and designing Immune Therapy. Euroasian J Hepato-Gastroenterol 2018;8(1):42-46.

Current advances in the elimination of hepatitis B in China by 2030

With its 78 million chronic carriers, hepatitis B virus (HBV) infection is still one of the leading public health challenges in China. Over the last two decades, China has made great progress on the prevention of HBV transmission through national vaccination programs. Zero transmission from mother to infant has been proposed as the current goal. Available anti-HBV therapy is efficacious in suppressing HBV replication; however, it fails to completely cure patients with chronic hepatitis B and even requires lifelong treatment. To reduce the costs and improve the efficacy, several trials have been recently conducted in China to optimize the current anti-HBV managements. Novel biomarkers were identified to predict treatment outcomes, and new promising treatment strategies were developed. Reports also indicate that coinfections of HBV with other hepatotropic viruses and human immunodeficiency virus are common in China and cause severe liver diseases, which should be recognized early and treated properly. Work is still needed to eliminate hepatitis B in China by 2030.

Biomarkers distinguish HBeAg seroconverted from non-converted individuals in chronic hepatitis B patients treated with a therapeutic vaccine

Cytokine assays of host immune responses to vaccination can indicate vaccine efficacy. Here we tested the hypothesis that assays of the cytokine status of infected individuals prior to therapeutic vaccination might provide a guide to vaccine therapeutic efficacy. If so, cytokine analysis might be used to select appropriate patients for therapeutic vaccination. Data were obtained from a panel of 14 cytokine/chemokine assays that were done during a phase III clinical trial of HBsAg-HBIG therapeutic vaccine (YIC) treatment of chronic hepatitis B (CHB) patients. Summarized assay results were compared between patients who responded by HBeAg-seroconversion and non-responders. Though no single cytokine or chemokine showed clear correlation with responsiveness, by bio-mathematical analysis with Boolean modelling, the combined results revealed that plasma IL-10, IL-33 and MIP-1α together correlated best with responsiveness. However, the difference between HBeAg seroconverted and non-converted YIC-treated CHB patients was maximized when results of all 14 cytokine/chemokine assays were included and showed a sensitivity around 0.59, and a specificity of 0.8. It suggested that the combined analysis of these elements may be useful to screen appropriate CHB patients for therapeutic vaccination with YIC.

Analysis of immunological mechanisms exerted by HBsAg-HBIG therapeutic vaccine combined with Adefovir in chronic hepatitis B patients

An HBsAg-HBIG therapeutic vaccine (Yeast-derived Immune Complexes, YIC) for chronic hepatitis B (CHB) patients has undergone a series of clinical trials. The HBeAg sero-conversion rate of YIC varied from 21.9% to 14% depending on the immunization protocols from 6 to 12 injections. To analyze the immunological mechanisms exerted by 6 injections of YIC, 44 CHB patients were separately immunized with YIC, alum as adjuvant control or normal saline as blank control, with add on of antiviral drug Adefovir in all groups. Kinetic increase in Th1 and Th2 cells CD4⁺ T cell sub-populations with association in decrease in Treg cells and increase of Tc1 and Tc17 cells in CD8⁺ T cells were observed in YIC immunized group. No such changes were found in the other groups. By multifunctional analysis of cytokine profiles, significant increase of IL-2 levels was observed, both in CD4⁺ and CD8⁺ T cells in the YIC immunized group, accompanied by increase in IFN-gamma and decrease of inhibitory factors (IL-10, TGF-β and Foxp3) in CD4⁺ T cells. In the alum immunized group, slight increase of IL-10, TGF-β and Foxp3 in CD4⁺ T cells was found after the second injection, but decreased after more injections, suggesting that alum induced early inflammatory responses to a certain extent. Similar patterns of responses of IL-17A and TNF-α in CD8⁺T cells were shown between YIC and the saline group. Results indicate that add on of Adefovir, did not affect host specific immune responses.

Antibody-dependent and antibody-independent uptake of HBsAg across human leucocyte subsets is similar between individuals with chronic hepatitis B virus infection and healthy donors

Maintaining detectable levels of antibodies to hepatitis B surface antigen (HBsAg) in serum after HBsAg sero-conversion is the key clinical endpoint indicative of recovery from infection with hepatitis B virus (HBV). As HBV-infected hepatocytes secrete HBsAg subviral particles in vast excess over HBV virions, detectable hepatitis B surface antibody (anti-HBs) titres imply complete elimination of HBV virions as well as HBsAg particles. Although intrahepatic phagocytes, for example Kupffer cells, are thought to mediate clearance of HBsAg via antibody (Ab)-dependent and Ab-independent mechanisms, the relative contributions of circulating phagocytic cell types to HBsAg elimination are poorly characterized. Understanding the role of various immune cell subsets in the clearance of HBsAg is important because Ab-dependent or Ab-independent phagocytic HBsAg uptake may modulate presentation of HBsAg-derived epitopes to antigen-specific T cells and hence plays a critical role in adaptive immunity against HBV. This study aims to characterize phagocytic leucocyte subsets capable of internalizing HBsAg immune complexes (HBsAg:IC) or un-complexed HBsAg particles in whole blood directly ex vivo. The data show that uptake of HBsAg:IC occurs most prominently in monocytes, B cells, dendritic cells and in neutrophils. In contrast, B cells, and to a lesser degree also monocytes, seem to be effective phagocytes for un-complexed HBsAg. Importantly, a similar pattern of phagocytic HBsAg uptake was observed in blood from chronic hepatitis B (CHB) patients compared to healthy controls, suggesting that phagocytosis-related cellular functions are not altered in the context of CHB.

Treatment of hepatitis B virus with combination therapy now and in the future

Chronic Hepatitis B continues as a significant public health problem despite the availability of safe and effective antivirals and a highly effective protective vaccine. Current therapy, however rarely leads to cure and lifelong therapy is often required, contributing to poor uptake and ongoing morbidity. New insights into the hepatitis B viral life cycle and the host immune response have expanded the potential targets for drug therapies with interesting antiviral candidates and novel immunotherapeutic approaches in early stage development. Yet, HBV persistence is multifactorial - due to an intrahepatic reservoir and ongoing HBV-mediated immune dysregulation, making "cure" unlikely to be realized through even the most efficacious monotherapy. Building on the success seen in the treatment of hepatitis C (HCV) and human immunodeficiency virus (HIV), combination therapy may be an essential strategy to improve efficacy and decrease viral breakthrough. Combinations acting on immune and viral targets are particularly attractive. However, creating synergy while balancing efficacy and safety remains a clear challenge. Various approaches to combination therapy are reviewed, highlighting strengths and challenges of each potential strategy. Overall, combination therapies are attractive as the next step towards cure and are a key strategy for achieving treatment with finite durations and durable endpoints.

Hepatitis B Virus Immunopathology, Model Systems, and Current Therapies

Most people develop acute hepatitis B virus (HBV)-related hepatitis that is controlled by both humoral and cellular immune responses following acute infection. However, a number of individuals in HBV-endemic areas fail to resolve the infection and consequently become chronic carriers. While a vaccine is available and new antiviral drugs are being developed, elimination of persistently infected cells is still a major issue. Standard treatment in HBV infection includes IFN-α, nucleoside, or nucleotide analogs, which has direct antiviral activity and immune modulatory capacities. However, immunological control of the virus is often not durable. A robust T-cell response is associated with control of HBV infection and liver damage; however, HBV-specific T cells are deleted, dysfunctional, or become exhausted in chronic hepatitis patients. As a result, efforts to restore virus-specific T-cell immunity in chronic HBV patients using antiviral therapy, immunomodulatory cytokines, or therapeutic vaccination have had little success. Adoptive cell transfer of T cells with specificity for HBV antigen⁺ cells represents an approach aiming to ultimately eliminate residual hepatocytes carrying HBV covalently closed circular DNA (cccDNA). Here, we discuss recent findings describing HBV immunopathology, model systems, and current therapies.

Chronic hepatitis B: Immunological profile and current therapeutic vaccines in clinical trials

More than 250million people worldwide are chronically infected with hepatitis B virus (CHB), and over half a million die each year due to CHB-associated liver complications such as cirrhosis and hepatocellular carcinoma. The translation of immunological knowledge about CHB into therapeutic strategies aiming to a sustainable hepatitis B virus (HBV) clearance has been challenging. In recent years, however, the understanding on the immune effectors required to overcome chronicity has notably increased thanks to preclinical and clinical research. Therapeutic vaccination may prove to be useful for treating CHB patients when coupled with current antiviral agents and other immunomodulatory strategies. This review summarizes current data and future perspectives on therapeutic vaccination. Other treatment alternatives that could be combined with vaccines for a complete cure from hepatitis B virus infection are also discussed.

Research progress of therapeutic vaccines for treating chronic hepatitis B

Hepatitis B virus (HBV) is a member of Hepadnavirus family, which leads to chronic infection in around 5% of patients with a high risk of developing liver cirrhosis, liver failure, and hepatocellular carcinoma. ¹ Despite the availability of prophylactic vaccines against hepatitis B for over 3 decades, there are still more than 2 billion people have been infected and 240 million of them were chronic. Antiviral therapies currently used in the treatment of CHB (chronic hepatitis B) infection include peg-interferon, standard α-interferon and nucleos/tide analogs (NAs), but none of them can provide sustained control of viral replication. As an alternative strategy, therapeutic vaccines for CHB patients have been widely studied and showed some promising efficacies in dozens of preclinical and clinical trials. In this article, we review current research progress in several types of therapeutic vaccines for CHB treatment, including protein-based vaccines, DNA-based vaccines, live vector-based vaccines, peptide-based vaccines and cell-based therapies. These researches may provide some clues for developing new treatments in CHB infection.

Immuno-potentiating pathway of HBsAg-HBIG immunogenic complex visualized

Chronic viral hepatitis B (CHB) is a major global health problem. A therapeutic vaccine for CHB comprised of yeast-derived recombinant HBsAg-anti-HBs immunogenic complexes (YIC) has been devloped by us. A series of clinical trials has shown its therapeutic efficacy in decreasing HBV viral load and converting serum HBeAg-positive to anti-HBe-positive status in a subpopulation of CHB patients. Herein, we present a study of the immuno-potentiating mechanisms of YIC revealed by live-cell imaging technology. We studied internalization and dissociation of YIC in cells in vitro, and antigen presentation and T cell stimulation in mice. We found that after YIC was internalized via the Fcγ receptors (FcγR) of antigen presenting cells, it was subsequently transferred through early and late endosomal into lysosomal compartments. The dissociation of YIC was mainly observed in the late endosome. Furthermore when YIC were injected into mice, the populations of IFN-γ- and TNF-α-producing CD8+ and CD4+ T cells were higher in the YIC group than in controls receiving antigen or antibody alone. These observations supplement the known mechanisms of YIC action as a therapeutic vaccine for CHB.

Treatment of hepatitis B virus: an update

Chronic hepatitis B virus infection is a global health concern as it affects over 240 million people worldwide and an estimated 686,000 people die annually as a result of complications of the disease. With the development of newer antiviral drugs, viral suppression of HBV is achievable, however elimination of HBV from infected individuals (functional cure) remains an issue. Due to persistence of HBV DNA (cccDNA) in infected cells, chronically infected patients who discontinue therapy prior to HBsAg loss or seroconversion are likely to relapse. Several novel therapeutic strategies are being researched and studied in clinical trials. Here we review these novel strategies to achieve sustained cure or elimination of HBV. These strategies include the targeting of the host or viral factors required for viral persistence as well as therapeutic vaccines.

Novel insights into immunotherapy for hepatitis B patients

The possible use of immunotherapy for hepatitis B has emerged for two major reasons: (1) chronic hepatitis B (CHB) is an immune-mediated pathological condition, and (2) commercially available antiviral drugs are of limited efficacy. Although various immunomodulatory agents have been used to treat patients with CHB during the last three decades, there is currently no consensus among physicians and hepatologists regarding the suitability of immunotherapy for patients with CHB. However, new insights into immunotherapy for CHB have emerged; these may facilitate design of effective and tolerable immunotherapy regimens for these patients. This review provides a comprehensive overview of immunotherapy for CHB.

Immunoregulatory functions of immune complexes in vaccine and therapy

Clinical and experimental preparations of IgG/soluble antigen complexes, as well as those formed following antibody therapy in vivo, are multifaceted immune regulators. These immune complexes (ICs) have been tested in humans and animal models, mostly in forms of experimental or clinical vaccination, for at least a century. With intensified research on Fcγ receptor-mediated immune modulation, as well as with immune complex-directed antigen processing, presentation, and inflammatory responses, there are renewed interests of using ICs in vaccines and immunotherapies. Currently, IC-based immune therapy has been broadly experimented in HBV and HIV viral infection control and antitumor treatments. However, mechanistic insights of IC-based treatments are relatively recent subjects of study; strong efforts are needed to establish links to connect laboratory findings with clinical practices. This review covers the history, mechanisms, and in vivo outcomes of this safe and effective therapeutic tool, with a clear aim to bridge laboratory findings with evolving clinical applications.

Immune therapy for hepatitis B

Although several antiviral drugs are now available for treatment of patients with chronic hepatitis B (CHB), sustained off-treatment clinical responses and containment of CHB-related complications are not achieved in majority of CHB patients by antiviral therapy. In addition, use of these drugs is endowed with substantial long term risk of viral resistance and drug toxicity. The infinite treatment regimens of antiviral drugs for CHB patients are also costly and usually unbearable by most patients of developing and resource-constrained countries. Taken together, there is a pressing need to develop new and innovative therapeutic approaches for CHB patients. Immune therapy seems to be an alternate therapeutic approach for CHB patients because impaired or distorted or diminished immune responses have been detected in most of these patients. Also, investigators have shown that restoration or induction of proper types of immune responses may have therapeutic implications in CHB. Various immunomodulatory agents have been used to treat patients with CHB around the world and the outcomes of these clinical trials show that the properties of immune modulators and nature and designing of immune therapeutic regimens seem to be highly relevant in the context of treatment of CHB patients. In this review, the general properties and specific features of immune therapy for CHB have been discussed for developing the guidelines of effective regimens of immune therapy for CHB.

Converting monoclonal antibody-based immunotherapies from passive to active: bringing immune complexes into play

Monoclonal antibodies (mAbs), which currently constitute the main class of biotherapeutics, are now recognized as major medical tools that are increasingly being considered to fight severe viral infections. Indeed, the number of antiviral mAbs developed in recent years has grown exponentially. Although their direct effects on viral blunting have been studied in detail, their potential immunomodulatory actions have been overlooked until recently. The ability of antiviral mAbs to modulate antiviral immune responses in infected organisms has recently been revealed. More specifically, upon recognition of their cognate antigens, mAbs form immune complexes (ICs) that can be recognized by the Fc receptors expressed on different immune cells of infected individuals. This binding may be followed by the modulation of the host immune responses. Harnessing this immunomodulatory property may facilitate improvements in the therapeutic potential of antiviral mAbs. This review focuses on the role of ICs formed with different viral determinants and mAbs in the induction of antiviral immune responses in the context of both passive immunotherapies and vaccination strategies. Potential deleterious effects of ICs on the host immune response are also discussed.

Current progress in the development of therapeutic vaccines for chronic hepatitis B virus infection

Chronic hepatitis B is still a major public health issue despite the successful prophylactic vaccination attempts. Chronicity of hepatitis B virus (HBV) is mainly due to its ability to debilitate host's immune system. Therefore, major measures have been taken to stop this process and help patients with chronic hepatitis B infection recover from their illness. While satisfactory results have been achieved using preventive HBV vaccines, a reliable and effective therapeutic treatment is still in need of extensive studies. Current treatments for chronic hepatitis B include direct antiviral agents and nucleoside/nucleotide analogs, which are not always effective and are also costly. In addition, due to the fact that chronic HBV is responsible for debilitation of the immune system, studies have focused on developing therapeutic vaccines to help host's immune system recover and limit the infection. Several approaches including but not restricted to recombinant peptide-based, DNA-based, viral vector-based, and cell-based approaches are currently in use to develop therapeutic vaccines against the chronic form of HBV infection. In the current review, the authors will first discuss the role of the immune system in chronic hepatitis B infection and will then focus on latest advancements in therapeutic vaccination of HBV especially the clinical trials that have been carried out so far.

Current trends in hepatitis B vaccination

One of the major successes in the area of vaccinology is the emergence, development and usage of hepatitis B vaccine (a prophylactic vaccine against HBV). Hepatitis B vaccine has protected millions of individuals from acquiring HBV infection and has prevented liver cancer in the majority of vaccinated subjects. Although initially designed as prophylactic vaccines, accumulative evidence has shown that these vaccines may also be used to treat patients with chronic hepatitis B. At present, there are two main areas of discussion in hepatitis B vaccination; development of more effective prophylactic hepatitis B vaccine that can provide protection to all vaccine recipients, and designing hepatitis B-based therapeutic vaccines for treatment of chronic hepatitis B patients.

New immunotherapy strategies for antiviral treatment of chronic hepatitis B

At present, chronic hepatitis B (CHB) is treated with nucleoside analogues and interferon-α (IFN-α), which can achieve good clinical effects, but cannot completely cure CHB. Main reasons are the immune tolerance or immune failure in the body's immune system, and the persistence of covalently closed circular DNA (cccDNA) in HBV infected hepatocytes. Therefore, the development of antiviral drugs which can completely eliminate cccDNA and of immunotherapy strategies to break the immune tolerance and reactivate the immune system is of clinical significance for curing CHB. This review focuses on recent progress in research of immune therapeutic strategies for CHB, such as lymphotoxin β receptor (LT-βR) agonists, therapeutic vaccines, Toll-like receptor (TLR) agonists, programmed death 1 (PD-1) blockade, genetically engineered T cells, interleukin (IL)-12 and so on.

Alum: an old dog with new tricks

Aluminum compounds (alum) are the most widely used adjuvants in veterinary and human vaccines. Alum was initially thought to be a simple depot for antigen retention; however, our understanding of the mechanism by which it works has progressed substantially in recent decades. Nonetheless, consensus regarding its roles in different aspects of immune regulation has not been reached, and it remains a long-standing research subject in the field of vaccinology. This review, in chronological order, discusses the various hypotheses proposed in mostly inadequate attempts to illuminate the mechanism by which alum works, from the depot theory to the involvement of the NLRP3 inflammasome and from cell death-associated danger factors to crystalline structure-mediated plasma membrane alteration. In addition, novel findings of unexpected beneficial effects of decreased HBV (Hepatitis B virus) viral load and HBeAg seroconversion in chronically infected patients, as well as significant tumor suppression in experimental mice following multiple alum-only injections are examined, revealing alum's potential clinical applications beyond its use as a simple tool in antigen preparation. With increasing threats of emerging microbes, originating from natural or man-made sources, that pose significant health concerns at the population scale, the potential use of alum as a 'first-aid' vaccine is also discussed.

Oral administration of synthetic selenium nanoparticles induced robust Th1 cytokine pattern after HBs antigen vaccination in mouse model

Hepatitis B virus (HBV) infection is known as a life-threatening liver infection and leads to chronic liver disease if left untreated. Nevertheless, the prevalence of HBV infection has been reduced by an approved vaccination approach using recombinant Hepatitis B surface Antigen (HBsAg) and Alum, known as the HBV vaccine. Alum can be used as an adjuvant to increase HBsAg immunogenicity as a strong Th2 stimulator. There is a vital need to stimulate Th1 immunity by HBsAg vaccination; however, the present vaccine does not induce a prophylactic immune response in some groups. The main aim of the present study was to induce a Th1 cytokine pattern and stimulate an immune response after HBsAg vaccination. Experimental mice were fed selenium nanoparticles (SeNPs) and were later immunized with 5μg of Hepatitis B Vaccine. After a period of 30 days, the experimental animals were given two booster doses of SeNPs during their vaccination course. Group one, i.e., the control vaccine group, was only administered the HBsAg vaccine. The two treated groups, Groups 2 and 3, were daily fed different doses of SeNPs (100μg and 200μg, respectively) via gavage. Group four was considered the control group and was only given phosphate buffered saline (PBS). Lymphocyte proliferation, IFN-γ and IL-4 levels, total antibody and the isotypes of IgG1, IgG2a, IgG2b, and IgM were measured by Enzyme Linked Immunosorbent Assay (ELISA). The administration of SeNPs and the HBs antigen vaccine affected the lymphocyte proliferation; moreover, the total antibody responses also increased the IFN-γ level and induced a Th1 response.

CONCLUSIONS

The present study proposed that the administration of SeNPs with a conventional HBs antigen vaccine induces a better immune response with a Th1 bias.

A Pilot Study of MicroRNAs Expression Profile in Serum and HBsAg Particles: Predictors of Therapeutic Vaccine Efficacy in Chronic Hepatitis B Patients

Chronic hepatitis B (CHB) remains a global health problem. Therapeutic vaccination has been successfully employed to treat a subpopulation of CHB patients. Personalized treatment can not only improve therapeutic efficacy, but also decrease the cost of medical care. Since microRNAs (miRNAs) are highly conserved and are involved in many cellular processes, exploring their expression profiles in CHB patients in association with responsiveness to therapeutic vaccination may be an approach for personalized treatment. In this study, we examined the kinetic expression profiles of 13 miRNAs in sera and serum-derived hepatitis surface antigen (HBsAg) particles in 10 CHB patients including 5 responders and 5 nonresponders selected from a large cohort of 136 patients enroled in a phase III clinical trial using antigen-antibody immunogenic complex based therapeutic vaccine (YIC). Eight miRNAs were detected in both sera and HBsAg particles. Among them, the levels of serum miRNAs and serum-derived HBsAg-carried miRNAs (let-7f, miR-22, miR-30a, and miR-122) were significantly lower in the responders group compared to those in the nonresponders group at baseline and throughout the course of treatment. The lower baseline levels of serum miRNAs and HBsAg-carried miRNAs were also associated with hepatitis e antigen clearance at week 76 and hepatitis e antigen seroconversion during the study period. In summary, our study suggests that lower baseline levels of serum miRNAs and HBsAg-carried miRNAs (let-7f, miR-22, miR-30a, and miR-122) associated with YIC treatment response and the variation trend of these 4 miRNAs could have a prognostic value for responsiveness to YIC treatment.