Overcoming tolerance in hepatitis B virus transgenic mice: a possible involvement of regulatory T cells

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

IMPORTANCE

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

Association of cytokines with hepatitis B virus and its antigen

To investigate the characteristics of cytokines in patients with different HBV infection status and their correlation with HBV DNA, HBsAg, and HBeAg levels. Peripheral blood samples were collected from patients with chronic HBV infection in immune tolerance phase (IT), HBeAg-positive chronic hepatitis B (CHB), and acute hepatitis B (AHB) groups, and levels of cytokines were detected by Luminex technique, and analyzed by FLEXMAP 3D analyzer. The correlation between cytokines and HBV DNA load, HBsAg, HBeAg, and alanine aminotransferase (ALT) level in patients with chronic HBV infection was analyzed. In total 312 subjects (184 males and 128 females) were enrolled in the study. There were significant differences among IT, CHB, and AHB groups in Flt-3L value (P = .003; H = 12.312), IFN-γ (P = .001; H = 11.723), IL-10 (P = .001; H = 18.736), IL-17A ((P = .001; H = 12.735), and TGF-β1 (P = .001; Z = 48.571). IFN-α2 levels in CHB group were significantly higher than those in IT and AHB groups (15.24 vs 35.78 pg/mL, P = .000; Z = 3.727; 13.88 vs 35.78 pg/mL, P = .024; Z = -2.258. In CHB group, the levels of HBsAg and ALT were positively correlated with the levels of IL-10 (r = .173; P = .006; r = 0.176; P = .006, respectively), while HBeAg level was positively correlated with the IFN-α2 level (r = .153; P = .016). In AHB group, the HBsAg level was positively correlated with Flt-3L, IFN-α2, IL-10, and IL-6 (r = .402; P = .023; r = .436; P = .016; r = .524, P = .002; r = .405; P = .022, respectively). HBeAg level was positively correlated with IFN-γ and IL-17A levels (r = .400; P = .023; r = .373; P = .036, respectively), and ALT level was positively correlated with IL-6 levels (r = .367; P = .039). In either AHB or CHB group, HBV DNA load was only related to TGF-β level (r = .493; P = .004; r = -.218, P = 0.009 respectively). The correlation between Flt-3L and HBsAg (F = 7.422; P = .007); IL-17, IL-6, and HBeAg (F = 5.757; P = .017; F = 6.156; P = .014) were statistically significant. There was significant correlation between TGF-β2 and HBV DNA (F = 11.795; P = .001), and between ALT and HBsAg, HBV DNA (F = 26.089; P = .000; F = 4.724; P = .031). HBsAg, HBeAg, and HBV DNA were correlated with cytokines and ALT in patients with HBV infection. The level of IFN-α2 was significantly higher in patients with CHB. HBV DNA load was only correlated with the level of TGF-β in acute or CHB.

Entecavir Plus Pegylated Interferon and Sequential HBV Vaccination Increases HBsAg Seroclearance: A Randomized Controlled Proof-of-Concept Study

BACKGROUND

HBsAg seroclearance is considered a functional cure for patients with chronic hepatitis B, but is rarely achievable with oral nucleos(t)ide analogs alone. We conducted a randomized controlled proof-of-concept trial to evaluate the impact of adding pegylated interferon (Peg-IFN) alfa-2a plus sequential or concomitant hepatitis B virus (HBV) vaccination.

METHODS

A total of 111 patients who achieved serum HBV DNA <20 IU/mL and quantitated HBsAg (qHBsAg) <3,000 IU/mL with entecavir were randomly assigned (1:1:1) to the E+sVIP group (entecavir + Peg-IFN alfa-2a [180 µg every week over 48 weeks] + sequential HBV vaccination [20 µg of HBsAg on weeks 52, 56, 60, and 76]), E+cVIP group (entecavir + Peg-IFN alfa-2a + concomitant HBV vaccination [weeks 4, 8, 12, and 28]), or the control group (entecavir only). The primary endpoint was HBsAg seroclearance at week 100 and secondary endpoints included safety.

RESULTS

No differences in baseline qHBsAg were observed among the groups. The E+sVIP group in the intention-to-treat analysis showed a significantly higher chance of HBsAg seroclearance during week 100 than the control group (16.2% vs. 0%, P=0.025), but the E+cVIP group (5.4%) failed to reach a significant difference (P=0.54). Adverse events were significantly more frequent in the E+sVIP (81.1%) or E+cVIP group (70.3%) than the control group (2.7%) (both P<0.0001). However, the frequency of serious adverse events did not differ significantly among three groups (2.7%, 5.4%, and 2.7%, respectively; P=1.00).

CONCLUSIONS

Entecavir plus an additional Peg-IFN alfa-2a treatment followed by sequential HBV vaccination under an intensified schedule significantly increases the chance of HBsAg seroclearance compared to entecavir alone.

Plasmacytoid Dendritic Cell Function and Cytokine Network Profiles in Patients with Acute or Chronic Hepatitis B Virus Infection

Background:

Plasmacytoid dendritic cells (pDCs) and cytokines play an important role in occurrence and recovery of hepatitis B virus (HBV) infection. The aim of this study was to explore the frequency and function of pDC and serum cytokine network profiles in patients with acute or chronic HBV infection.

Methods:

The healthy individuals (HI group), hepatitis B envelope antigen (HBeAg)-positive chronic HBV patients in immune tolerance (IT) phase (IT group), HBeAg-positive chronic HBV patients (CHB group), and acute HBV patients (AHB group) were enrolled in this study. The frequency of cluster of differentiation antigen 86 (CD86) + pDC and the counts of CD86 molecular expressed on surface of pDC were tested by flow cytometer. The quantitative determinations of cytokines, including Fms-like tyrosine kinase 3 ligand (Flt-3L), interferon (IFN)-α2, IFN-γ, interleukin (IL)-17A, IL-6, IL-10, transforming growth factor (TGF)-β1 and TGF-β2, were performed using Luminex multiplex technology.

Results:

In this study, there were 13 patients in HI group, 30 in IT group, 50 in CHB group, and 32 in AHB group. Compared with HI group, HBV infected group (including all patients in IT, CHB and AHB groups) had significantly higher counts of CD86 molecular expressed on the surface of pDC (4596.5 ± 896.5 vs. 7097.7 ± 3124.6; P < 0.001). The counts of CD86 molecular expressed on the surface of pDC in CHB group (7739.2 ± 4125.4) was significantly higher than that of IT group (6393.4 ± 1653.6, P = 0.043). Compared with IT group, the profile of cytokines of Flt-3L, IFN-γ, and IL-17A was decreased, IFN-α2 was significantly increased (P = 0.012) in CHB group. The contents of IL-10, TGF-β1, and TGF-β2 in AHB group were significantly increased compared with IT and CHB groups (all P < 0.05).

Conclusions:

This study demonstrated that the function of pDC was unaffected in HBV infection. The enhanced function of pDC and IFN-α2 might involve triggering the immune response from IT to hepatitis active phase in HBV infection. Acute patients mainly presented as down-regulation of the immune response by enhanced IL-10 and TGF-β.

Regulatory B cell phenotype and mechanism of action: the impact of stimulating conditions

A diverse population of regulatory B (Breg) cells reportedly exhibits significant immunomodulatory effects in various models of inflammatory responses and infectious diseases caused by bacteria, viruses or parasites. Breg cells contribute to maintenance of homeostasis via IL-10 production and multiple IL-10-independent mechanisms. The current review describes various phenotypic and functional subsets of Breg cells in autoimmune and infectious diseases and discusses the impacts of experimental conditions that have been found to drive Breg cell differentiation.

Breaking Hepatitis B Virus Tolerance and Inducing Protective Immunity Based on Mimicking T Cell-Independent Antigen

There are over 350 million chronic carriers of hepatitis B virus (HBV) in the world, of whom about a third eventually develop severe HBV-related complications. HBV contributes to liver cirrhosis and hepatocellular carcinoma development. Remarkable progress has been made in selective inhibition of HBV replication by nucleoside analogs. However, how to generate protective antibody of HBsAb in HBV-infected patients after HBV-DNA becomes negative still remains a challenge for scientists. In this study, we show that OmpC-HBsAg 'a' epitope chimeric protein vaccine can break HBV tolerance and induce protective immunity in HBV transgenic mice based on mimicking T cell-independent antigen to bypass T cells from the adaptive immune system. The antibodies induced by the vaccine have the ability to prevent HBV virion infection of human hepatocytes.

Vaccination with ubiquitin-hepatitis B core antigen-cytoplasmic transduction peptide enhances the hepatitis B virus-specific cytotoxic T-lymphocyte immune response and inhibits hepatitis B virus replication in transgenic mice

Chronic hepatitis B virus (HBV) infection is characterized by functionally impaired type 1 T-helper cell (Thl) immunity and poor HBV‑specific T‑cell responses. Ubiquitin (Ub), a highly conserved small regulatory protein, commonly serves as a signal for target proteins that are recognized and degraded in proteasomes. The rapid degradation of Ub‑mediated antigens results in efficient stimulation of cell‑mediated immune responses. Thus, the Ub‑HBV core antigen (HBcAg)‑cytoplasmic transduction peptide (CTP) fusion protein was designed for specific delivery of a foreign modified antigen to the cytoplasm of antigen‑presenting cells. HBV transgenic mice were used to determine whether Ub‑HBcAg‑CTP would restore HBV‑specific immune responses and anti‑viral immunity in these animals. The results demonstrated that synthesized Ub‑HBcAg‑CTP not only significantly increased the levels of interleukin‑2 and interferon (IFN)‑γ compared with those in the HBcAg‑CTP, IFN‑α, Ub‑HBcAg, HBcAg and phosphate‑buffered saline groups, but additionally induced the highest IFN‑γ+ CD8+ T‑cell numbers and HBV‑specific cytotoxic T lymphocyte (CTL) responses, indicating a strong immune response. In addition, enhancement of specific CTL activity provoked by the fusion protein reduced hepatitis B surface antigen (HBsAg) and HBV DNA serum levels and diminished the expression of HBsAg and HBcAg in liver tissue of HBV transgenic mice, suggesting that there was a therapeutic effect. In conclusion, the present study provided evidence that Ub‑HBcAg‑CTP activated the Th1‑dependent immunity, triggered functional T cell responses and subsequently inhibited viral replication in HBV transgenic mice. These observations suggested that the fusion protein may represent an innovative and promising candidate for active immunotherapy during chronic and persistent HBV.

Tapasin modification on the intracellular epitope HBcAg18-27 enhances HBV-specific CTL immune response and inhibits hepatitis B virus replication in vivo

HBV-specific cytotoxic T-lymphocyte (CTL) activity has a very important role in hepatitis B virus clearance. Present studies suggest that Tapasin, a endoplasmic reticulum (ER) chaperone, stabilizes the peptide-receptive MHC I conformation, allowing peptide exchange and increasing more peptides to be translocated into the ER. We have previously testified that cytoplasmic transduction peptide (CTP)-HBcAg(18-27)-Tapasin fusion protein could enter cytoplasm of dendritic cells, and enhance T cells' response to generate specific CTLs efficiently in vitro. In the present study, we evaluated specific immune responses of CTP-HBcAg(18-27)-Tapasin fusion protein in HLA-A2 transgenic mice (H-2K(b)) and anti-viral ability in HBV transgenic mice, and explored the mechanisms probably involved in. The studies showed that CTP-HBcAg(18-27)-Tapasin not only increased production of cytokine IFN-γ and interleukin-2 (IL-2), compared with CTP-HBcAg(18-27), HBcAg(18-27)-Tapasin, and PBS, but also significantly induced the higher percentages of IFN-γ+CD8(+) T cells and specific CTL responses in HLA-A2 transgenic mice. Moreover, enhancement of specific CTL activity induced by the fusion protein reduced HBV DNA and hepatitis B surface antigen (HBsAg) levels and decreased the expression of HBsAg and hepatitis B core antigen (HBcAg) in liver tissue of HBV transgenic mice. In addition, CTP-HBcAg(18-27)-Tapasin could upregulate the expression of JAK2, Tyk2, STAT1, and STAT4 in T lymphocytes in HLA-A2 transgenic mice splenocytes. However, there was no significant difference on the expressions of JAK1, JAK3, and STAT6 between each group. In conclusion, CTP-HBcAg(18-27)-Tapasin fusion protein could enhance not only the percentages of CTLs but also induce robust specific CTL activity and inhibits hepatitis B virus replication in vivo, which was associated with activation of the JAK/STAT signaling pathway.

Hepatitis B surface antigen could contribute to the immunopathogenesis of hepatitis B virus infection

Various findings concerning the clinical significance of quantitative changes in hepatitis B surface antigen (HBsAg) during the acute and chronic phase of hepatitis B virus (HBV) infection have been reported. In addition to being a biomarker of HBV-replication activity, it has been reported that HBsAg could contribute to the immunopathogenesis of HBV persistent infection. Moreover, HBsAg could become an attractive target for immune therapy, since the cellular and humeral immune response against HBsAg might be able to control the HBV replication and life cycle. However, several reports have described the immune suppressive function of HBsAg. HBsAg might suppress monocytes, dendritic cells (DCs), natural killer (NK), and natural killer T (NK-T) cells by direct interaction. On the other hand, cytotoxic T lymphocytes (CTLs) and helper T (Th) cells were exhausted by high amounts of HBsAg. In this paper, we focused on the immunological aspects of HBsAg, since better understanding of the interaction between HBsAg and immune cells could contribute to the development of an immune therapy as well as a biomarker of the state of HBV persistent infection.

Identification of a unique double-negative regulatory T-cell population

Regulatory T (Treg) cells represent one of the main mechanisms of regulating self-reactive immune cells. Treg cells are thought to play a role in down-regulating immune responses to self or allogeneic antigens in the periphery. Although the function of Treg cells has been demonstrated in many experimental settings, the precise mechanisms and antigen specificity often remain unclear. In a hepatitis B e antigen-T-cell receptor (HBeAg-TCR) double transgenic mouse model, we observed a phenotypically unique (TCR+)  CD4- /CD8-  CD25(+/-)  GITR(high)  PD-1(high)  FoxP3-) HBeAg-specific population that demonstrates immune regulatory function. This HBeAg-specific double-negative regulatory cell population proliferates vigorously in vitro, in contrast to any other known regulatory population, in an interleukin-2-independent manner.

Regulatory T cells in HBV and HCV liver diseases: implication of regulatory T lymphocytes in the control of immune response

IMPORTANCE OF THE FIELD

Hepatic cirrhosis is a frequent consequence of chronic hepatitis infection (HBV and HCV) or alcohol abuse and the most common cause of hepatocellular carcinoma (HCC). Currently, liver transplantation remains the only effective therapeutic approach for cirrhosis-related HCC patients. The evolution of the pathology strongly depends on immunological mechanisms.

AREAS COVERED IN THIS REVIEW

Despite the presence of specific T cells, viral chronic infection and continuous tumor growth suggest a failure of immune control. It appears that direct suppression of antiviral or antitumor effector cells by regulatory T cells plays a pivotal role in the impairment of immune response. Several types of regulatory T cells have been described, natural regulatory T cells (nTreg) and induced-type 1 regulatory T cells (Tr1) being the best characterized.

WHAT THE READER WILL GAIN

Currently, there is no evidence for a direct implication of regulatory T cells in the evolution of hepatitis, especially concerning chronic infection, cirrhosis late stage and HCC progress. However, recent studies show that regulatory T cells are implicated in the modulation of HBV- and HCV-associated immune response, thus, promoting HCC progress.

TAKE HOME MESSAGE

Therefore, nTreg and Tr1 cells seem to play an important role in the control of immune response leading to chronic hepatitis infection and progression of the pathology to cirrhosis and HCC.

The delivery of HBcAg via Tat-PTD enhances specific immune response and inhibits Hepatitis B virus replication in transgenic mice

Recent studies have indicated that the therapeutic vaccine based on enhancement of HBV-specific cytotoxic T-lymphocyte (CTL) activity may lead to viral clearance in chronically infected individuals. It is demonstrated that protein transduction domains (PTD) from HIV-1-Tat protein is able to enter cells when combined with exogenous antigens and induce specific CTL responses. We have previously testified that the expressed and purified fusion protein containing Tat-PTD47-57 and HBcAg could enter cytoplasm of dendritic cells, and enhance T cells response to generate HBcAg-specific CTLs efficiently in vitro. In the present study, we evaluated HBcAg-specific immune responses of PTD-HBcAg fusion protein in BALB/c mice and antiviral immunity in HBV transgenic mice. The studies showed that PTD-HBcAg not only induced significantly higher antibody responses, but also increased production of cytokine (IFN-gamma, IL-2, IL-4 and IL-10) compared to HBcAg alone and PBS. Moreover, PTD-HBcAg fusion protein increased significantly the percentages of IFN-gamma+CD8+ T cells and HBcAg-specific (CTL) responses. Also, enhancement of immune response induced by fusion protein reduced HBV DNA and HBsAg levels and decreased the expression of HBsAg in liver tissue of HBV transgenic mice. In conclusion, PTD-HBcAg fusion protein could enhance not only cell immune response but also humoral immune response, and induce robust specific CTL activity and therapeutic effects in HBV transgenic mice.

Molecular characteristics and stages of chronic hepatitis B virus infection

Hepatitis B virus (HBV) is a common viral pathogen that causes a substantial health burden worldwide. Remarkable progress has been made in our understanding of the natural stages of chronic HBV infection. A dynamic balance between viral replication and host immune response is pivotal to the pathogenesis of liver disease. Knowledge of the HBV genome organization and replication cycle can unravel HBV genotypes and molecular variants, which contribute to the heterogeneity in outcome of chronic HBV infection. Most HBV infections are spontaneously resolved in immunocompetent adults, whereas they become chronic in most neonates and infants at a great risk of developing complications such as cirrhosis and hepatocellular carcinoma (HCC). Those with chronic HBV infection may present in one of the four phases of infection: immune tolerance, immune clearance [hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB)], inactive carrier state, and reactivation (HBeAg-negative CHB). Understanding the dynamic nature of chronic HBV infection is crucial in the management of HBV carriers. Long-term monitoring and optimal timing of antiviral therapy for chronic HBV infection help to prevent progression of HBV-related liver disease to its later stage, particularly in patients with higher risk markers of HCC, such as serum DNA concentration, HBeAg status, serum aminotransferase, HBV genotypes, and pre-core or core mutants.

Recipient cytotoxic T lymphocyte antigen-4 +49 G/G genotype is associated with reduced incidence of hepatitis B virus recurrence after liver transplantation among Chinese patients

BACKGROUND

Single-nucleotide polymorphisms (SNP) of two-gene locus cytotoxic T lymphocyte antigen-4 (CTLA-4) +49 and CD86 +1057 were previously reported to influence the outcome of liver transplantation (LT) with respect to allograft acceptance. SNP at CTLA-4 +49 was also suggested to be associated with the individual difference in the clearance of hepatitis B virus (HBV). However, their influence on the incidence of post-LT HBV reinfection was not clear. With the increasing knowledge of costimulatory mechanisms on LT and host immune response, we designed this study to investigate the relationship between different alleles as well as genotypes at these two locations and HBV reinfection after LT.

METHODS

Genomic DNA from 167 LT recipients with HBV-related diseases was genotyped for CTLA-4 +49 and CD86 +1057 genomic polymorphisms using a sequence-specific primer-polymerase chain reaction (PCR-SSP). HBV recurrence was diagnosed based on the serological and pathological finding of HBV DNA and HBsAg.

RESULTS

The present study indicated that the recipients with CTLA-4 +49 GG genotype had a reduced risk (6.67%) of HBV recurrence compared with non-CTLA-4 +49 GG-carrying individuals (20.7%) (relative risk 3.098) (P=0.032). The allelic frequency of CTLA-4 +49 G was also significantly lower in patients with HBV recurrence, compared with that in patients without HBV recurrence (P=0.013, odds ratio 2.176, 95% confidence interval 1.170-4.046). However, no significant association was found between CD86 +1057 and HBV recurrence.

CONCLUSION

Our result on CTLA-4 +49 A/G polymorphism indicated that the CTLA-4 +49 GG genotype was related to a reduced risk in the incidence of HBV recurrence.

Therapeutic potential of dendritic cell-based immunization against HBV in transgenic mice

Hepatitis B virus (HBV) transgenic mice that express HBV envelope proteins represent a model of chronic HBV infection suitable for the development of therapeutic immunization strategies. To address immunologically therapeutic effects induced by peptide-pulsed DCs, HBV transgenic mice were immunized with peptide-pulsed DCs, and the mice were killed after three times of immunization and the splenocytes were stimulated in vitro and detected by IFN-gamma ELISPOT and cytotoxic T lymphocyte (CTL) activity. The data demonstrated that HBV-specific CD8+ T cell response could be induced and CD8+ T cells had specific CTL activity. Furthermore, ELISA and fluorescent quantitative PCR were performed to detect the level of serum HBsAg and HBV DNA and the results demonstrated that HBV-specific peptide-pulsed DCs could significantly reduce the concentration of serum HBsAg and HBV DNA. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were measured and no significant differences were observed between the different groups, which indicated that no hepatocellular injury occurred. Taken together, the data strongly demonstrated that CD8+ T cell responses and antiviral immunity were elicited in HBV transgenic mice, suggesting that peptide-pulsed DCs could elicit an effective antiviral immunity.