Hepatitis B immunopathogenesis and immunotherapy

Molecular epidemiology of hepatitis B virus (HBV) in Ethiopia: A review article

Hepatitis B virus (HBV) belongs to the family Hepadnaviridae and is the smallest human DNA virus, with a genome that is only 3200 nucleotides long. The absence of proofreading function in HBV reverse transcriptase provides a wide range of genetic variants for targeted outgrowth at different stages of infection. A number of sub genotypes and ten HBV genotypes (A through J) have been identified through analyses of the divergence of HBV genomic sequences. Numerous clinical outcomes, including the emergence of chronicity, the course of the disease, the effectiveness of treatment, and the response to vaccination, have been related to differences in genotype between HBV isolates. There are just seven studies that have been done in Ethiopia that examine the molecular epidemiology of HBV. Moreover, these studies haven't been compiled and reviewed yet. In this review, we looked at the genetic diversity and molecular epidemiology of HBV, the relationship between HBV genotypes and clinical outcomes, the immunopathogenesis of HBV, and finally the molecular epidemiology of HBV in Ethiopia. PubMed, Embase, and Google Scholar search engines were used to find relevant articles for the review. By using HBV genotyping, clinicians can better tailor vaccination decisions and antiviral therapy for patients with chronic hepatitis B who are more likely to experience the disease's progression.

Critical Updates on Chronic Hepatitis B Virus Infection in 2021

Chronic hepatitis B virus (HBV) infection is a global healthcare burden in the form of chronic liver disease, cirrhosis, liver failure and liver cancer. There is no definite cure for the virus and even though extensive vaccination programs have reduced the burden of liver disease in the future population, treatment options to eradicate the virus from the host are still lacking. In this review, we discuss in detail current updates on the structure and applied biology of the virus in the host, examine updates to current treatment and explore novel and state-of-the-art therapeutics in the pipeline for management of chronic HBV. Furthermore, we also specifically review clinical updates on HBV-related acute on chronic liver failure (ACLF). Current treatments for chronic HBV infection have seen important updates in the form of considerations for treating patients in the immune tolerant phase and some clarity on end points for treatment and decisions on finite therapy with nucleos(t)ide inhibitors. Ongoing cutting-edge research on HBV biology has helped us identify novel target areas in the life cycle of the virus for application of new therapeutics. Due to improvements in the area of genomics, the hope for therapeutic vaccines, vector-based treatments and focused management aimed at targeting host integration of the virus and thereby a total cure could become a reality in the near future. Newer clinical prognostic tools have improved our understanding of timing of specific treatment options for the catastrophic syndrome of ACLF secondary to reactivation of HBV. In this review, we discuss in detail pertinent updates regarding virus biology and novel therapeutic targets with special focus on the appraisal of prognostic scores and treatment options in HBV-related ACLF.

Influence of Pattern Recognition Receptor Ligands on Induction of Innate Immunity and Control of Hepatitis B Virus Infection

Failure of current therapies to cure chronic hepatitis B has led to renewed interest in therapies that stimulate the host immune system. APOBEC3 (A3) family enzymes have been shown to induce mutations in hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) leading to inhibition of HBV transcription and replication. Pattern recognition receptor (PRR) agonists have been reported to suppress HBV, but it is unclear whether these agonists induce A3 gene expression in hepatocytes. We, therefore, evaluated whether PRR signaling activates the expression of A3 genes and other innate immunity genes and restricts HBV infection. HepG2-sodium taurocholate cotransporting polypeptide (NTCP) cells were infected with HBV and treated with various PRR agonists. The level of HBV infection was subsequently assessed by measurement of HBV biomarkers, including HBV DNA, cccDNA, HBs, and HBe antigens in infected hepatocytes. Among all tested PRR ligands, only Poly(I:C)-HMW/LyoVec and Poly(I:C)-HMW significantly inhibited hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), HBV DNA, and cccDNA, whereas R848 and lipopolysaccharide (LPS) only showed significant inhibition on HBsAg and HBeAg, but not virus DNA. CpG and Pam3CSK4, on the other hand, had no significant inhibitory effect on any of the HBV infection parameters. Moreover, Poly(I:C)-HMW/LyoVec and Poly(I:C)-HMW were the only ligands that significantly increased IL-8 secretion. Interestingly, HBV infection reduced IL-8 secretion induced by Poly(I:C)-HMW and to a lesser extent Poly(I:C)-HMW/LyoVec. Poly(I:C)-HMW/LyoVec had a significant effect on increasing the expression level of A3F, A3G, A3H, TLR3, RIG-1, and MDA5 genes. Our data suggest that PRR agonists may control HBV infection through different mechanisms. The RIG-1 and MDA5 agonist, Poly(I:C)-HMW/LyoVec, seems to downregulate HBV infection through induction of A3 genes.

Cross talk between hepatitis B virus and innate immunity of hepatocytes

Innate immunity plays a major role in controlling viral infections. Recent exploration of sodium taurocholate co-transporting polypeptide receptor as specific hepatitis B virus (HBV) receptor in human hepatocytes has provided appropriate cell culture tools to study the innate immunity of hepatocytes and its cross talk with HBV. In this review, we give a brief update on interaction between HBV and innate immunity using the currently available in vitro cellular models that support the complete life cycle of HBV. We will discuss how HBV can act as a 'stealth' virus to counteract the innate immune responses mediated by the pathogen recognition receptors of hepatocytes and escape the first line of surveillance of the host immune system. We give an overview of the cellular components of innate immunity that present in these in vitro models and discuss how activating these innate immunity components may contribute to the eradication of HBV infection.

Humoral Immune Responses and Hepatitis B Infection

BACKGROUND

Chronicity or seroclearance of hepatitis B virus (HBV) antigens is determined by the host immune responses. Current approaches to treat HBV patients are based on inhibition of replication using different antivirals (nucleoside or nucleotide analogs) as monotherapy, or along with immune modulators as combination therapy is being used worldwide for reducing the viral load. Understanding the role of immune cellular therapies with currently available treatments for persistent viral-mediated responses in HBV patients is unexplored. However, the generation of antibodies against a surface (HBs) and envelop (HBe) antigen of hepatitis B remains an issue for future studies and needs to be explored.

SUMMARY

Humoral immunity, specifically T follicular helper (TFh) cells, may serve as a target for therapy for HBsAg seroconversion. In this review, we have been engrossed in the importance and role of the humoral immune responses in CHBV infection and vertical transmission. Key Message: TFh cells have been suggested as the potential target of immunotherapy which lead to seroconversion of HBe and HBs antigens of HBV. HBsAg seroconversion and eradication of covalently closed circular DNA are the main challenges for existing and forthcoming therapies in HBV infection.

Immunoreactivity pattern of monoclonal antibodies against Hepatitis B vaccine with global Hepatitis B virus genotypes

Hepatitis B surface antigen (HBsAg) specific monoclonal antibodies (mAbs) are potentially valuable therapeutic and diagnostic tool. We have previously established and characterized a panel of mAbs derived from immunized BALB/c mice with a yeast-derived recombinant HB vaccine subgentoype A2 and HBsAg subtype adw2. This study was conducted to evaluate the reactivity pattern of this anti-HBs mAbs panel with various genotypes and subgenotypes of HBV using the first WHO HBV genotype reference panel containing 15 serum samples representing the subgenotypes A1, A2, B1, B2, C2, D1-D3, E, F2, and H. Ten out of 21 anti-HBs mAbs were able to strongly recognize all gentopye/subtypes of HBsAg provided in the WHO reference panel. However, 10 out of 21 anti-HBs mAbs showed a moderate to profound loss of reactivity with HBV genotypes/HBsAg subtypes D2/ayw3, E/ayw4, F2/adw4, and H/adw4. Two mAbs from the second group displayed a profoundly reduced reactivity with only 1 out of 3 C2/adr genotype/subtype samples. The amino acid alignment of these 3 samples showed that this particular sample contains amino acid substitution at residue 127, which is located inside "a" determinant. This amino acid substitution, which profoundly affected the reactivity of anti-HBs antibodies, has been previously reported only in D/ayw3, E/ayw4, F/adw4, and H. Interestingly, the amino acid alignment of the samples in this WHO panel showed that P127T substitution can also be found in C2/adr. Comparing amino acids sequences inside the antigenic loop (AGL) showed that D2/ayw3 contains a T118A/P127T double substitution, E/ayw4 contains P127L/T140S, F2/adw4 contains P127L/T140S/ F158L, and H/adw4 contains P127L substitution. Therefore, amino acid variability at positions 118, 127, 140, and 158 was found to cause significant loss of reactivity with anti-HBs mAbs. Since HBsAg variability in different genotypes of HBV can profoundly affect the reactivity of anti-HBs mAbs, analytical sensitivity for HBsAg assays should be considered based on the circulating and common HBV variants in the relevant countries.

Immune function of plasmacytoid dendritic cells, natural killer cells, and their crosstalk in HBV infection

Chronic hepatitis B virus infection is a major health problem, with over 245 million chronic carriers worldwide. This persistent infection is thought to be associated with inefficient innate and adaptive immune responses. Natural killer cells (NK cells) and plasmacytoid dendritic cells (pDCs) are the major innate immune cells which respond to viral infection at the early phase and are considered major components of the antiviral immune response. In this review, we summarize recent findings regarding the role of NK cells, pDCs, and their cross-talk in HBV infection and its chronicity. Although the data regarding the biological function of pDCs and NK cells in HBV infection is still controversial, many studies show that in chronic HBV infection, the cytotoxicity of NK cells is retained, while their capacity to secrete cytokines is strongly impaired. In addition, interferon-α production by pDCs is impaired during chronic HBV infection, and the virus interferes with pDC-NK cell interaction.

Hepatocytic expression of human sodium-taurocholate cotransporting polypeptide enables hepatitis B virus infection of macaques

Hepatitis B virus (HBV) is a major global health concern, and the development of curative therapeutics is urgently needed. Such efforts are impeded by the lack of a physiologically relevant, pre-clinical animal model of HBV infection. Here, we report that expression of the HBV entry receptor, human sodium-taurocholate cotransporting polypeptide (hNTCP), on macaque primary hepatocytes facilitates HBV infection in vitro, where all replicative intermediates including covalently closed circular DNA (cccDNA) are present. Furthermore, viral vector-mediated expression of hNTCP on hepatocytes in vivo renders rhesus macaques permissive to HBV infection. These in vivo macaque HBV infections are characterized by longitudinal HBV DNA in serum, and detection of HBV DNA, RNA, and HBV core antigen (HBcAg) in hepatocytes. Together, these results show that expressing hNTCP on macaque hepatocytes renders them susceptible to HBV infection, thereby establishing a physiologically relevant model of HBV infection to study immune clearance and test therapeutic and curative approaches.

Association of the tandem polymorphisms (rs148314165, rs200820567) in TNFAIP3 with chronic hepatitis B virus infection in Chinese Han population

Background

Chronic hepatitis B virus (HBV) infection remains an important public health issue. A20, a ubiquitin-editing protein encoded by tumor necrosis factor alpha-inducible protein 3 (TNFAIP3) gene, is complicated in HBV infection and liver injury. The tandem polymorphisms (rs148314165, rs200820567), deletion T followed by a T to A transversion and collectively referred to as TT > A in TNFAIP3, may attenuate A20 expression.

Methods

The rs148314165 and rs200820567 polymorphisms were examined using PCR amplification followed by direct sequencing in 419 patients with chronic HBV infection, 77 HBV infection resolvers and 175 healthy controls of Chinese Han ethnicity.

Results

The genotypes and alleles of rs148314165 and rs200820567 polymorphisms determined and the haplotypes constructed were consistently identical, confirming the reliable determination of the TT > A variant. The genotypes of rs148314165 and rs200820567 in HBV patients, HBV infection resolvers and healthy controls are in Hardy-Weinberg equilibrium (P > 0. 05). The patients with chronic HBV infection had higher frequency of TT > A variant than healthy controls (6.6% vs. 3.4%; OR, 1.979; 95% CI, 1.046–3.742; P = 0.033). The frequency of TT > A variant between patients with chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma had no significant differences.

Conclusions

The TT > A variant of TNFAIP3 may be associated with the susceptibility of chronic HBV infection but not the clinical diseases. Studies in large sample size of HBV patient and control populations are required to further clarify the role of this important variant in chronic HBV infection and the disease progression related to the infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0814-5) contains supplementary material, which is available to authorized users.

Localization of immunodominant epitopes within the "a" determinant of hepatitis B surface antigen using monoclonal antibodies

The common "a" determinant is the major immunodominant region of hepatitis B surface antigen (HBsAg) shared by all serotypes and genotypes of hepatitis B virus (HBV). Antibodies against this region are thought to confer protection against HBV and are essential for viral clearance. Mutations within the "a" determinant may lead to conformational changes in this region, which can affect the binding of neutralizing antibodies. There is an increasing concern about identification and control of mutant viruses which is possible by comprehensive structural investigation of the epitopes located within this region. Anti-HBs monoclonal antibodies (mAbs) against different epitopes of HBsAg are a promising tool to meet this goal. In the present study, 19 anti-HBs mAbs were employed to map epitopes localized within the "a" determinant, using a panel of recombinant mutant HBsAgs. The topology of the epitopes was analyzed by competitive enzyme-linked immunosorbent assay (ELISA). Our results indicate that all of the mAbs seem to recognize epitopes within or in the vicinity of the "a" determinant of HBsAg. Different patterns of binding with mutant forms were observed with different mAbs. Amino acid substitutions at positions 123, 126, 129, 144, and 145 dramatically reduced the reactivity of antibodies with HBsAg. The T123N mutation had the largest impact on antibody binding to HBsAg. The reactivity pattern of our panel of mAbs with mutant forms of HBsAg could have important clinical implications for immunoscreening, diagnosis of HBV infection, design of a new generation of recombinant HB vaccines, and immunoprophylaxis of HBV infection as an alternative to therapy with hepatitis B immune globulin (HBIG).

Mechanism for cytoplasmic transduction peptide-HBcAg18-27-Tapasin to induce HBV specific CTL response in C57BL/6 mice

AIM: To observe whether the fusion protein cytoplasmic transduction peptide (CTP) -HBcAg_18-27-Tapasin can induce HBV-specific cytotoxic T lymphocyte (CTL) response in C57BL/6 mice via the JAK / STAT pathway.

METHODS: C57BL/6 mice were randomly divided into four groups: CTP-HBcAg_18-27-Tapasin alone group, CTP-HBcAg_18-27-Tapasin + AG490 group, AG490 alone group, and PBS group. Mice were immunized with the fusion protein through intramuscular injection, and AG490 was administered through intraperitoneal injection. The proliferation of T lymphocytes was observed using CCK-8 assay. The levels of the cytokines secreted by T lymphocytes were detected by ELISA, and the levels of intracellular cytokines of proliferative T lymphocytes were detected by flow cytometry. Expression levels of molecules of the JAK/STAT signal pathway were detected by real-time PCR.

RESULTS: The percentage of CD8⁺IFN-γ⁺ T cells, T lymphocytes proliferative activity and the levels of Th1 cytokines in the CTP-HBcAg_18-27-Tapasin alone group were significantly increased compared with the CTP-HBcAg_18-27-Tapasin + AG490 group (P < 0.01), although there was no statistical significance between the other groups. The expression levels of Jak2 and STAT4 were significantly higher in the CTP-HBcAg_18-27-Tapasin alone group than the rest groups (P < 0.05), and the expression levels of Tyk2 and STAT1 were also dramatically increased in the CTP-HBcAg_18-27-Tapasin alone group compared to other groups (P < 0.01).

CONCLUSION: CTP-HBcAg_18-27-Tapasin fusion protein increases HBV-specific CTL response via the JAK/STAT signal pathway in C57BL/6 mice.