Hepatic expression patterns of the large and middle hepatitis B virus surface proteins in viremic and nonviremic chronic hepatitis B

PreS1- targeting chimeric antigen receptor T cells diminish HBV infection in liver humanized FRG mice

Current therapies control but rarely achieve a cure for hepatitis B virus (HBV) infection. Restoration of the HBV-specific immunity by cell-based therapy represents a potential approach for a cure. In this study, we generated HBV specific CAR T cells based on an antibody 2H5-A14 targeting a preS1 region of the HBV large envelope protein. We show that the A14 CAR T cell is capable of killing hepatocytes infected by HBV with high specificity; adoptive transfer of A14 CAR T cells to HBV infected humanized FRG mice resulted in reductions of all serum and intrahepatic virological markers to levels below the detection limit. A14 CAR T cells treatment increased the levels of human IFN-γ, GM-CSF, and IL-8/CXCL-8 in the mice. These results show that A14 CAR T cells may be further developed for curative therapy against HBV infection by eliminating HBV-infected hepatocytes and inducing production of pro-inflammatory and antiviral cytokines.

Immunobiology and pathogenesis of hepatitis B virus infection

Hepatitis B virus (HBV) is a non-cytopathic, hepatotropic virus with the potential to cause a persistent infection, ultimately leading to cirrhosis and hepatocellular carcinoma. Over the past four decades, the basic principles of HBV gene expression and replication as well as the viral and host determinants governing infection outcome have been largely uncovered. Whereas HBV appears to induce little or no innate immune activation, the adaptive immune response mediates both viral clearance as well as liver disease. Here, we review our current knowledge on the immunobiology and pathogenesis of HBV infection, focusing in particular on the role of CD8⁺ T cells and on several recent breakthroughs that challenge current dogmas. For example, we now trust that HBV integration into the host genome often serves as a relevant source of hepatitis B surface antigen (HBsAg) expression during chronic infection, possibly triggering dysfunctional T cell responses and favouring detrimental immunopathology. Further, the unique haemodynamics and anatomy of the liver - and the changes they frequently endure during disease progression to liver fibrosis and cirrhosis - profoundly influence T cell priming, differentiation and function. We also discuss why therapeutic approaches that limit the intrahepatic inflammatory processes triggered by HBV-specific T cells might be surprisingly beneficial for patients with chronic infection.

Do the circulating Pre-S/S quasispecies influence hepatitis B virus surface antigen levels in the HBeAg negative phase of HBV infection?

BACKGROUND

Virus, host factors and their interplay influence Hepatitis B surface Antigen serum levels during Hepatitis B Virus (HBV) infection course and treatment.

AIM

To study the Pre-S/S circulating quasispecies in a cohort of untreated, HBeAg negative, genotype-D, HBsAg carriers.

METHODS

We studied 260 carriers: 71 with HBeAg negative infection (ENI; HBV-DNA ≤2000 IU/mL); 42 Grey Zone (GZ; HBV-DNA ≤20 000 IU/mL); 82 chronic hepatitis (CH) and 65 cirrhosis (CI) (HBV-DNA > 20 000 IU/mL). Population sequencing was applied to identify Pre-S/S gene mutations responsible for any amino acid substitution or potential biological/antigenic implications (M-muts) on HBsAg.

RESULTS

HBsAg serum levels were lower in ENI + GZ than in CH + CI (2.61 [-1.10/4.06] vs 3.62 [2.41/4.92] log₁₀ IU/mL, P < 0.001) and in CI than CH (3.48 [2.41/4.38] vs 3.66 [2.57/4.92] log₁₀ IU/mL, P < 0.001). M-muts were found in 73 (28.1%) cases: 5 (7.0%) ENI, 3 (7.1%) GZ, 26 (31.7%) CH, 39 (60.0%) CI (P < 0.001) and mostly in Pre-S2 (17.6%) than Pre-S1 (5.8%) and Small-S (10.8%; P < 0.001). Overall HBsAg serum levels were higher in carriers with M-muts (3.56 [0.95/4.38] vs 3.17 [-1.10/4.92] log₁₀ IU/mL, P < 0.001), but comparable in carriers with or without M-mut when considering separately ENI + GZ (2.84 [0.95/3.89] vs 2.61 [-1.10/4.06] log₁₀ IU/mL, P = 0.330] and CH + CI (3.57 [2.67/4.38] vs 3.63 [2.41/4.92] log₁₀ IU/mL, P = 0.37). Infection phase (β: 0.422, P < 0.001), age (β: -0.260, P < 0.001), ALT (β: -0.103, P = 0.045), liver stiffness (β: -0.118, P = 0.039) and HBV-DNA (β: 0.384, P < 0.001), but not M-mut were independently associated with HBsAg serum levels.

CONCLUSIONS

In HBeAg negative, genotype-D, carriers Pre-S/S heterogeneity increases with severity of liver disease, but does not influence HBsAg serum levels, that in low viraemic carriers are associated with an effective control of HBV.

Viral Biomarkers in Chronic HBeAg Negative HBV Infection

Viral biomarkers are important tools for monitoring chronic hepatitis B virus (HBV) hepatitis B early antigen (HBeAg) negative infection, both in its natural course as well as during and after treatment. The biomarkers consist of antibodies against viral epitopes, viral proteins, and molecular surrogate markers of the quantity and transcriptional activity of the stable episomal HBV covalently closed circular DNA (cccDNA) which is located in the nuclei of the infected hepatocytes. HBV deoxyribonucleic acid (DNA) or else viral load measurement in plasma or serum is a marker of HBV replication of major clinical importance. HBV DNA is used for staging and treatment monitoring as described in international scientific guidelines. Quantification of HBV antigens, mainly hepatitis B surface antigen (HBsAg) as well as Hepatitis B core related antigen (HBcrAg), play an important yet secondary role, especially in cases of low or undetectable HBV DNA and has been evaluated for the classification of the inactive carrier state, as a predictor of subsequent HBsAg clearance, treatment outcome, and development of hepatocellular carcinoma (HCC). The measurement of the replicative intermediate HBV RNA in serum is currently evaluated and may also prove to be a significant biomarker particularly in patients treated with nucleot(s)ide analogs. This review focuses on the viral biomarkers mentioned above and their role in HBV, HBeAg negative, infection.

From HCV To HBV Cure

Approximately 170 million people are chronically infected with HCV and 350 million are chronically infected with HBV worldwide. It is estimated that more than one million patients die from complications related to chronic viral hepatitis, mainly HCC which is one of the most frequent cancers in many countries, especially Africa, the Middle East and Asia. HCV drug development has been impressive, and this revolution led to several direct-acting antiviral agents achieving an HCV cure after only 6-12 weeks. This progress could theorically lead to HCV global elimination making HCV and its consequences a rarity. HBV research and development programs can learn from the HCV experience, to achieve an HBV functional or sterilizing cure. This review will summarize key steps which have been realized for an HCV cure, and discuss the next steps to achieve for an HCV elimination. And also, how this HCV revolution has inspired scientists and clinicians to achieve the same for HBV.

Hepatitis B Virus Middle Protein Enhances IL-6 Production via p38 MAPK/NF-κB Pathways in an ER Stress-Dependent Manner

During hepatitis B virus (HBV) infection, three viral envelope proteins of HBV are overexpressed in the endoplasmic reticulum (ER). The large S protein (LHBs) and truncated middle S protein (MHBs^t) have been documented to play roles in regulating host gene expression and contribute to hepatic disease development. As a predominant protein at the ultrastructural level in biopsy samples taken from viremic patients, the role of the middle S protein (MHBs) remains to be understood despite its high immunogenicity. When we transfected hepatocytes with an enhanced green fluorescent protein (EGFP)-tagged MHBs expressing plasmid, the results showed that expression of MHBs cause an upregulation of IL-6 at the message RNA and protein levels through activating the p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor-kappa B (NF-κB) pathways. The use of specific inhibitors of the signaling pathways can diminish this upregulation. The use of BAPTA-AM attenuated the stimulation caused by MHBs. We further found that MHBs accumulated in the endoplasmic reticulum and increased the amount of glucose regulated protein 78 (GRP78/BiP). Our results provide a possibility that MHBs could be involved in liver disease progression.

Hepatitis B Surface Antigen Quantification across Different Phases of Chronic Hepatitis B Virus Infection Using an Immunoradiometric Assay

BACKGROUND/AIMS

Quantification of hepatitis B surface antigen (HBsAg) is an emerging serologic test and may be useful for identifying treatment strategies for chronic hepatitis B (CHB). This study aimed to evaluate HBsAg titers during the natural course of CHB and identify correlations between HBsAg titers and hepatitis B virus (HBV) DNA concentrations across different CHB phases measured using an immunoradiometric assay (IRMA).

METHODS

CHB phases were defined on the basis of HBV DNA concentrations, the presence of hepatitis B e antigen/antibody (HBeAg/Ab) and serum alanine aminotransferase levels. Serum HBsAg titers and paired HBV DNA concentrations in the different phases of CHB were compared using 627 serum samples.

RESULTS

Mean HBsAg titers were significantly higher in the immunotolerant (IT) phase and immunoreactive (IR) HBeAg-positive phase than in the low-replicative (LR) and HBeAg-negative CHB (ENH) states. The correlation between HBsAg titers and HBV DNA concentrations was modest in the IT (n=36, r=0.804, p<0.001) and IR (n=48, r=0.773, p<0.001) phases, and it was poor in the LR state (n=116, r=0.289, p=0.002); however, no significant correlation was observed in the ENH state (n=67, r=0.146, p=0.237) or in the oral nucleos(t)ide analogue-treated group (n=267).

CONCLUSIONS

HBsAg quantification using IRMA might be useful for discriminating different CHB phases and different stages of chronic liver disease.

HBsAg quantification: useful for monitoring natural history and treatment outcome

The template of hepatitis B virus transcription, the covalently closed circular DNA (cccDNA), plays a key role in the life cycle of the virus and permits the persistence of infection. It has been suggested that hepatitis B surface antigen (HBsAg) quantification reflects the concentration of cccDNA in the liver. In hepatitis B e antigen (HBeAg) positive chronic hepatitis B, HBsAg levels are higherduring the immune tolerance phase than during the immune clearance phase. During the natural history of chronic hepatitis B, serum HBsAg declines progressively from the immune-tolerant to the low replicative phase. In HBeAg negative patients, the combination of low hepatitis B virus (HBV) DNA (<2000 IU/ml) and low HBsAg levels (<1000 IU/ml) can predict inactive carrier status, low risk of hepatocellular carcinoma, and the probability of HBsAg loss. HBsAg in combination with HBV DNA predicts the outcome of Peg-Interferon therapy: An absence of decline at week 12 is a good predictor of non-response and to stop therapy. Any decline at week 24, suggests that therapy should be continued to 48 weeks. Although the decrease in HBsAg decline slow with nucleos(t)ide analogue therapy, a rapid decline can predict future HBsAg seroclearance. A level <100 IU/ml during six consecutive months could be a marker of a sustained response after treatment cessation.

Early serum hepatitis B virus large surface protein level: a stronger predictor of virological response to peginterferon alfa-2a than that to entecavir in HBeAg-positive patients with chronic hepatitis B

BACKGROUND

The response rate to antiviral therapy varies greatly among individuals, and its prediction is still very challenging.

OBJECTIVES

To evaluate the usefulness of serum hepatitis B virus large surface protein (LHBs) levels compared with HBsAg in prediction of the antiviral treatment effect.

STUDY DESIGN

Quantification of LHBs, HBsAg and HBV DNA was carried out at baseline and during antiviral therapy (weeks 4, 12, 24, 36 and 48) in HBeAg-positive patients treated with peginterferon alfa-2a (n = 21) or entecavir (n = 41).

RESULTS

The serum LHBs concentration was correlated positively with HBV DNA and HBsAg (r = 0.635 and 0.588, respectively). LHBs and HBV DNA levels decreased significantly in a biphasic manner and HBsAg level tended to decrease slowly in both treatment groups. In peginterferon alfa-2a group, the cutoff of 88.46 ng/ml in serum LHBs at week 4 gave the best AUC ( = 0.96) with positive and negative predictive values of 88.9% and 100%, in association with virological response (VR). Serum LHBs level at week 4 also showed an association with VR in entecavir group (AUC 0.78). The predictive model incorporating LHBs, HBsAg and HBV DNA could discriminate VR at baseline (AUC 0.79) and showed an association with serological response (SR) at week 12 (AUC 0.80) in peginterferon alfa-2a group.

CONCLUSIONS

On-treatment quantification of serum LHBs may be a more useful parameter for predicting VR in patients on peginterferon alfa-2a than those on entecavir. Combining LHBs, HBsAg and HBV DNA can predict VR and SR more effectively and earlier.

Immuno-polymerase chain reaction as a unique molecular tool for detection of infectious agents

Theoretically, the immuno-polymerase chain reaction (IPCR) method is the most sensitive technique for the detection of proteins and gains its uniqueness through the exponential amplification of a signal-generating nucleic acid intermediate attached to a protein target. This method is similar to PCR for the detection of nucleic acid targets, and has now been shown to offer the ability to detect infectious agents where nucleic acids are not present. Although the technical development of IPCR has taken a torturous path down a winding avenue of encouraging advances, the method remains rarely utilized by the scientific community and completely unused as a clinical diagnostic test approved by a national accrediting agency. Although the use of real-time instrumentation has enhanced the performance of IPCR to higher levels of statistical accuracy and reproducibility, as compared with the conventional method, its application remains limited by the high standards required for clinical diagnoses of infectious diseases. This review summarizes experimental data published to date describing the utilization of the IPCR method as it relates to the detection and diagnosis of human infectious disease, and examines the progressive development of this method, as well as the factors impeding its universal application as a clinical diagnostic tool. With further standardization and validation, the IPCR method has the potential to become the most analytically sensitive method available for the detection of target proteins of infectious diseases.

[Quantification of hepatitis B virus HBsAg: clinical implications]

The surface antigen of hepatitis B virus (HBsAg) is the main serological marker of HBV infection since its discovery almost 50 years ago. Currently the quantification of HBsAg has acquired special relevance as there are commercial tests to measure its levels. Several studies have shown that in patients treated with pegylated interferon alfa the fall of HBsAg levels predicts the loss of HBsAg and persistent virologic response. The role of the quantification of HBsAg in the treatment with nucleoside analogues is still not well understood and requires further studies.

Evidence of serologic activity in chronic hepatitis B after surface antigen (HBsAg) seroclearance documented by conventional HBsAg assay

Background

Possible serologic activity after hepatitis B surface antigen (HBsAg) seroclearance documented by conventional assays in chronic hepatitis B (CHB) has not been thoroughly investigated.

Methods

We determined the levels of serum hepatitis B virus (HBV) DNA, hepatitis B core-related antigen (HBcrAg), and linearized HBsAg (CLEIA prototype) in 329 CHB patients (72.0% male) after HBsAg seroclearance was documented by a conventional HBsAg assay.

Results

The median interval between presentation and HBsAg seroclearance was 69.4 months. The median age at HBsAg seroclearance was 50 years. Assays for serum HBV DNA, HBcrAg, and linearized HBsAg were performed at a median time interval of 11.2 months after HBsAg loss. Linearized HBsAg and HBcrAg were detectable in 85 (25.8%) and 69 (21%) patients, respectively, and one or both serologic markers were detectable in 133 patients (40.4%). Serum HBV DNA was detectable in only 7 patients (2.1%). There was no correlation between linearized HBsAg and HBcrAg levels (r = 0.095, p = 0.924). The incidences of detectable linearized HBsAg and HBcrAg did not differ between patient samples taken at 6–12 and >12 months after HBsAg seroclearance (p = 0.146 and 0.079, respectively). Among patients with detectable serologic markers, median levels of linearized HBsAg (p = 0.581) and HBcrAg (p = 0.951) did not significantly change with time after HBsAg seroclearance.

Conclusion

Using novel HBcrAg and linearized HBsAg assays, viral serologic activity after HBsAg seroclearance was demonstrated in more than 40% of CHB patients. These tests have potential applications in diagnosing and prognosticating CHB patients with HBsAg seroclearance.

HBsAg Quantification in Clinical Practice

Several standardized commercial assays for quantification of hepatitis B surface antigen (qHBsAg) are now available. Studies on HBsAg kinetics from Asia and Europe have demonstrated that HBsAg levels are highest during the immune-tolerant phase, become lower during immune-clearance phase and are the lowest in hepatitis B 'e' antigen (HBeAg)-negative inactive low-replicative phase with a rise during HBeAg-negative chronic hepatitis B (CHB). Combined use of hepatitis B virus-deoxyribonucleic acid (HBV-DNA) and HBsAg levels may help in differentiating true inactive carrier state from HBeAg-negative CHB. Several retrospective studies have demonstrated a role for decline in HBsAg level for predicting response and nonresponse to therapy. In HBeAg-positive patients treated with pegylated-interferon (PEG-IFN), a lack of decline of qHBsAg at week 12 predicts nonresponders while a decline of qHBsAg at week 24 predicts responders to PEG-IFN. In HBeAg-negative patients, if at week 12, there is no decline in qHBsAg and the HBV-DNA decline is < 2 log, the patient is unlikely to respond, then stopping of PEG-IFN should be considered. With nucleos(t)ide analogs, the decline in HBsAg is lower than that with PEG-IFN and more marked in patients with HBeAg-positive chronic hepatitis, with elevated alanine aminotransaminase (ALT), thus suggesting that active immune response against HBV is required to lower HBsAg. In patients with HBeAg-negative chronic hepatitis, fall in HBsAg may help in developing stopping rules to reduce the need for lifelong therapy. Information provided by HBsAg is complementary to HBV-DNA and cannot replace the same. Prospective studies on HBsAg kinetics from all regions of the world are required to define optimum time of testing and cutoff levels before stopping rules can be recommended.

Quantification of HBsAg: Basic virology for clinical practice

Hepatitis B surface antigen (HBsAg) is produced and secreted through a complex mechanism that is still not fully understood. In clinical fields, HBsAg has long served as a qualitative diagnostic marker for hepatitis B virus infection. Notably, advances have been made in the development of quantitative HBsAg assays, which have allowed viral replication monitoring, and there is an opportunity to make maximal use of quantitative HBsAg to elucidate its role in clinical fields. Yet, it needs to be underscored that a further understanding of HBsAg, not only from clinical point of view but also from a virologic point of view, would enable us to deepen our insights, so that we could more widely expand and apply its utility. It is also important to be familiar with HBsAg variants and their clinical consequences in terms of immune escape mutants, issues resulting from overlap with corresponding mutation in the P gene, and detection problems for the HBsAg variants. In this article, we review current concepts and issues on the quantification of HBsAg titers with respect to their biologic nature, method principles, and clinically relevant topics.

Quantification of hepatitis B surface antigen: a new concept for the management of chronic hepatitis B

HBsAg is a very important clinical test that might not only indicate active hepatitis B virus (HBV) infection but might also be used to predict clinical and treatment outcome. Clearance of HBsAg in patients with chronic HBV infection is associated with a much better clinical outcome, although surveillance for early detection of hepatocellular carcinoma (HCC) should continue. HBV DNA quantification is currently used for selecting candidates for therapy, monitoring response to therapy and detecting the emergence of drug resistance. Assays for HBsAg quantification are less expensive than HBV DNA and fully automated with a high throughput capacity. HBsAg titering may be a useful tool to manage patients with chronic HBV, to more clearly define which patients may, and more importantly, may not, benefit from treatment. Baseline and on-treatment HBsAg quantification may help to refine future treatment algorithms for both immune-modulator therapy and nucleos(t)ide analogues. Both HBV markers provide complementary information on the status of HBV infection. However, the relevance of serum HBsAg levels and its use as a reliable replacement for both covalently closed circular DNA and HBV DNA remain unclear.

IFNgamma expression inhibits LHBs storage disease and ground glass hepatocyte appearance, but exacerbates inflammation and apoptosis in HBV surface protein-accumulating transgenic livers

BACKGROUND/AIMS

Interferon gamma (IFNgamma) controls hepatitis B virus replication. As systemic application may cause severe adverse effects, approaches of liver-directed IFNgamma gene therapy may represent an attractive alternative for treatment of chronic viral hepatitis B and thus needs testing in vivo in suitable animal models.

METHODS

We therefore crossbred Alb-1HBV transgenic mice overexpressing the large HBV surface protein (LHBs) in their livers and developing LHBs storage disease and ground glass hepatocyte appearance with SAP-IFNgamma transgenic animals previously shown to exhibit constitutive hepatic IFNgamma expression, and analyzed the resulting double-transgenic offspring.

RESULTS

We found that IFNgamma coexpression significantly reduced hepatic LHBs expression and thereby inhibited hepatocellular LHBs storage disease and ground glass hepatocyte appearance. The beneficial antiviral IFNgamma effects as observed in Alb1-HBV SAP-IFNgamma double-transgenic livers were associated with significantly elevated serum ALT concentrations, massive mononuclear cell infiltrates, appearance of Councilman bodies, and increased alpha-PARP (poly(ADP-ribose) polymerase cleavage).

CONCLUSIONS

Exacerbation of hepatic necroinflammation and increased hepatocellular apoptosis rate in IFNgamma-expressing Alb1-HBV transgenic livers suggest that special precautions be taken for testing approaches of liver-specific IFNgamma expression in patients with chronic hepatitis B.

Different types of ground glass hepatocytes in chronic hepatitis B virus infection contain specific pre-S mutants that may induce endoplasmic reticulum stress

Ground glass hepatocyte (GGH) represents a histological hallmark of chronic hepatitis B virus infection and contains surface antigens in the endoplasmic reticulum (ER). Several types of GGHs are recognized at different hepatitis B virus replicative stages. The recent identification of pre-S mutants from GGHs encourages us to investigate whether different GGHs may harbor specific mutants and exhibit differential biological activities. In this study, we applied laser capture microdissection to isolate specific GGHs from a total of 50 samples on eight resected liver specimens. The surface genes in two major types of GGHs were analyzed. Type I GGHs expressed an inclusion-like pattern of hepatitis B surface antigens and harbored mutants with deletions over pre-S1 region, whereas type II GGHs, distributed in clusters and emerged at late replicative phase, contained mutants with deletions over pre-S2 region that defines a cytotoxic T lymphocyte (CTL) immune epitope, and may represent an immune escape mutant. Transfection of pre-S mutants in Huh7 revealed decreased syntheses of middle and small S proteins with accumulation of large surface antigen in ER, which in turn led to the activation of ER stress response with differential activities for different mutants. This study therefore demonstrates that different GGHs may contain specific mutants and exhibit differential biological activities.

Identification of a pre-S2 mutant in hepatocytes expressing a novel marginal pattern of surface antigen in advanced diseases of chronic hepatitis B virus infection

BACKGROUND AND AIMS

The expression of hepatitis B viral (HBV) antigens in liver tissue reflects the replicative status of chronic HBV infection. We have previously recognized a novel marginal pattern of hepatitis B surface antigen (HBsAg) in hepatocytes, which usually clusters in groups and emerges at the late non-replicative phase. This study was designed to investigate whether the marginal-type HBsAg represented the gene product of a specific HBV-surface mutant.

METHODS

Microdissection of cirrhotic nodules homogeneously expressing marginal HBsAg was performed on two of 12 resected livers from HBsAg-seropositive patients with hepatocellular carcinoma. The gene presumably encoding marginal HBsAg was polymerase chain reaction (PCR)-cloned, sequenced and analysed. In vitro transfection and expression of the cloned surface mutant plasmids were performed on the Huh7 cell line to illustrate intrahepatic HBsAg expression.

RESULTS

Immunohistochemical staining revealed that the marginal HBsAg was positive for pre-S1 and thus contained large surface proteins. The PCR cloning and sequencing of the genes presumably encoding marginal-type HBsAg in both cases revealed the same deletion at the 5' terminus (nt 2-55) of pre-S2. A point mutation on the small-surface (S) antigen was also found in one case. The pre-S2 deletion sequence and the mutation sites of the S gene coincide with human lymphocyte antigen-restricted T- and/or B-cell epitopes. In vitro transfection of the mutant plasmid revealed a blot-like retention or accumulation of HBsAg in the cytoplasm or at the periphery of hepatocytes, accompanied by a decreased secretion of HBsAg in the culture supernatant, mimicking intrahepatic expression.

CONCLUSION

A natural pre-S2 deletion mutant was identified in hepatocytes expressing a novel marginal pattern of HBsAg, which probably contains mutant, large, surface proteins. The biological significance of the pre-S2 deletion mutant should be interesting in view of the clustering proliferation of hepatocytes expressing marginal HBsAg.

Ultrastructural analysis of hepatitis B virus in HepG2-transfected cells with special emphasis on subviral filament morphogenesis

The intracellular accumulation of empty hepatitis B virus (HBV) particles of filamentous shape leads to a direct cytopathic effect in so-called ground-glass hepatocytes. The aim of this study was to investigate how these filaments can be structurally formed at the cellular level. By electron microscopy, we reexamined the HBV-producer HepG2T-14 cells, which have been described as producing a substantial amount of empty HBV filaments compared with the other forms of HBV particles. Examination of ultrathin sections of HepG2T14 cells revealed the presence of HBV virions and filaments at the periphery of extremely large intracellular cisternae, probably related to a pre-Golgi compartment. Very long filaments appeared to be formed by a tubular budding of a long portion of the cisterna membrane. This phenomenon may be identical to that observed in the hepatocytes of HBV chronic carriers, in which the inability of the infected cell to export long HBV filamentous particles through the cellular secretion pathway seems to be at the origin of a direct cytopathic effect.

Histopathology and pathobiology of hepatotropic virus-induced liver injury

The present report concerns current knowledge regarding immunopathogenesis that can be applied in the interpretation of histopathological changes in acute and chronic viral hepatitis. The histopathological features of viral hepatitis have not been changed and light microscopic examination remains essential for making a diagnosis and classification of chronic hepatitis and for the provision of objective parameters on grading and staging. However, new understanding and knowledge of viral pathogenesis, host immune responses, the biological behaviour of the causative viral agents and, in particular, viral interference in multiple hepatotropic viral infections must be taken into consideration in the interpretation of histopathological and immunopathological findings of liver tissues. This report also presents some histopathological analyses on multiple hepatotropic viral infections. It can be concluded that the diagnostic histological criteria for acute hepatitis remain applicable in such settings. However, the cause of acute flare up in chronic hepatitis could not be determined without clinical, virological and serological information. Routine histopathology cannot distinguish a new infection from an acute exacerbation due to a high level of viral replication or mutant virus. A repertoire of immunocytochemical stainings for viral antigens is helpful, but caution must be exercised in suggesting a specific viral aetiology due to the fact that suppression of pre-existing viral antigens can be pronounced when the new or concurrent infection is hepatitis C virus related.

Intracellular accumulation of incompletely processed transforming growth factor-alpha polypeptides in ground glass hepatocytes of chronic hepatitis B virus infection

BACKGROUND

Transforming growth factor-alpha is an intracellularly processed and secreted polypeptide that induces a proliferative response in epithelial target cells and represents a potential regulatory factor in embryonic development, liver regeneration, and also hepatocarcinogenesis. We have observed focal transforming growth factor-alpha expression in liver tissues with chronic hepatitis B virus infection.

METHODS

To further elucidate the nature of this focal transforming growth factor-alpha accumulation we have analyzed overall 23 different liver tissues with chronic hepatitis B virus and hepatitis C virus infection as well as normal liver tissues by immunohistology, ELISA, and Western immunoblot with and without immunoprecipitation.

RESULTS

By immunohistology transforming growth factor-alpha polypeptides showed focal subcellular accumulation in ground glass hepatocytes, the histological hallmark of chronic hepatitis B virus infection, in co-localization with HBV-preS1 antigen. By ELISA and Western immunoblot increased tissue concentrations of transforming growth factor-alpha were demonstrated in chronically hepatitis B virus-infected liver tissues with ground glass hepatocytes, especially a 15-kD polypeptide, most likely representing an incompletely processed transforming growth factor-alpha polypeptide. Transforming growth factor-alpha retention in ground glass hepatocytes is not a general unspecific effect, since it was not observed for several other secretory liver proteins. Accumulated transforming growth factor-alpha in ground glass hepatocytes does not co-localize with Epidermal Growth Factor Receptor expression.

CONCLUSION

Thus evidence is presented that a principally secreted (viral) polypeptide (HBV-preS1) can interfere with the secretion and processing of a second (cellular) protein (transforming growth factor-alpha). Accumulation of transforming growth factor-alpha may result from alteration of the endoplasmic reticulum due to storage of hepatitis B virus surface antigen particles. No evidence was found for transforming growth factor-alpha in ground glass hepatocytes to intracellularly interact with the Epidermal Growth Factor Receptor.

Development of a two-site immuno-PCR assay for hepatitis B surface antigen

Hepatitis B virus (HBV) gene transcription may occur at very low levels resulting in HBsAg concentrations in serum and liver below the limit of detection by currently available immunoassays. An assay has been developed that combines the specificity of two high affinity anti-HBs monoclonal antibodies (MAb) directed against distinct and separate determinants in the 'a' domain of HBsAg with the highly sensitive polymerase chain reaction (PCR) detection method. Following capture of HBsAg present in serum samples, the second anti-HBs MAb, which is biotinylated, is added. Binding of the second antibody allows the subsequent specific binding of streptavidin and a biotinylated linear DNA molecule derived from a bluetongue virus (BTV) gene. Presence of this DNA is then detected by PCR using BTV-specific primers. The PCR product is quantified by a liquid-phase oligonucleotide enzymatic assay, which further increases the sensitivity of the technique. The use of a two-site MAb capture and PCR detection system for HBsAg was shown to greatly enhance the specificity and sensitivity of the assay and detect as little as 0.5 pg of HBsAg in serum samples. It is suggested that the principles of this technique could be applied to measure other low level viral antigens in serum and biological samples.

Hybrid hepatitis B virus core-pre-S proteins synthesized in avirulent Salmonella typhimurium and Salmonella typhi for oral vaccination

Avirulent salmonellae expressing foreign genes are attractive for use as oral vaccine carriers. To facilitate the stable expression of heterologous genes without conferring antibiotic resistance, a deletion of the asdA1 gene was introduced into Salmonella typhimurium and S. typhi delta cya delta crp mutant vaccine strains. An asd-complementing plasmid expressing hybrid hepatitis B virus nucleocapsid-pre-S (HBcAg-pre-S) particles was constructed. These hybrid HBcAg-pre-S particle genes were stably expressed in S. typhimurium and S. typhi delta cya delta crp mutant vaccine strains in this balanced, lethal host-vector combination. A single oral immunization of BALB/c mice with a recombinant S. typhimurium delta cya delta crp mutant synthesizing hybrid HBcAg-pre-S elicited potentially virus-neutralizing anti-pre-S serum immunoglobulin G antibodies. In addition, serum immunoglobulin G recognizing S. typhimurium lipopolysaccharide was induced. Distribution in tissue after oral immunization was analyzed in one plasmid-strain combination. The recombinant S. typhimurium colonized the gut-associated lymphoid tissue and the spleen and persisted for over 4 weeks, retaining the HBcAg-pre-S expression plasmid. An isogenic virulence plasmid-cured S. typhimurium delta cya delta crp strain expressing the same HBcAg-pre-S gene had reduced immunogenicity for the carried antigen after oral immunization.

Dysregulated surface gene expression from disrupted hepatitis B virus genomes

During chronic infection by hepatitis B virus, the viral genome frequently integrates into the host chromosome, causing gross disruption and rearrangement of the viral DNA. We have obtained data showing that viral genomic disruptions which delete the enhancers from the transcribed region of the viral surface gene can lead to dysregulation of surface gene expression at the transcriptional level. Specifically, in cells transfected with such disrupted genomes, there is a decreased amount of transcripts coding for the major form of the surface protein but little change in the amount of transcripts coding for the large surface protein. In these cells, secretion of the surface proteins is blocked in the endoplasmic reticulum-Golgi intermediate compartment, consistent with previous work from other groups showing that relative overexpression of the large surface protein can block secretion of all forms of the surface protein. Our findings suggest that viral genomic rearrangements during integration may be a contributing factor in the pathogenesis of ground-glass hepatocytes, which contain large amounts of intracellular surface proteins as a result of a block in secretion and are frequently seen in the livers of patients with chronic hepatitis B.

A virulent Salmonella expressing hybrid hepatitis B virus core/pre-S genes for oral vaccination

This report reviews and extends data on the use of hepatitis B virus (HBV) core (HBcAg) particles as a carrier moiety for B-cell epitopes of the HBV envelope proteins. Virus-neutralizing epitopes of the HBV pre-S region were inserted at the N-terminus, the N-terminus through a precore linker sequence, the C-terminus and an internal position of HBcAg by genetic engineering in Escherichia coli. The hybrid HBc/pre-S proteins were purified and their antigenicity and immunogenicity analysed. All purified HBc/pre-S particles were particulate. Pre-S epitopes inserted at the N-terminus through a precore polylinker, the truncated C-terminus and at the internal position between HBcAg amino acids 75 and 81 were accessible on the particle surface. N-terminal fusions required the presence of the linker sequence to become surface accessible and immunogenic. Fusions to the N- and C-termini of HBcAg did not interfere with HBcAg antigenicity and immunogenicity. In contrast, insertion at the internal site abrogated recognition of HBcAg by five out of six monoclonal antibodies and diminished recognition by human polyclonal anti-HBc antibodies as well as HBcAg immunogenicity. A pre-S(2) sequence fused to the C-terminus of HBcAg was surface accessible and weakly immunogenic. Pre-S(1) sequences fused to the N-terminus through a precore linker were surface accessible and highly immunogenic. The same sequence fused to the core methionine was not surface accessible or immunogenic. Insertion of the same pre-S(1) sequence at an internal position of HBcAg resulted in the most efficient anti-pre-S(1) antibody response.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of former and newly developed HBV assays in a Third World setting

Newly available HBV serological assays have not been established routinely in most underdeveloped countries. Utilizing enzyme-immune assays to determine the presence of pre-S1 antigen and anti-pre-S2, and using two conventional hybridization techniques and the PCR assay to detect HBV-DNA, we studied 30 HBsAg chronic carriers and as a reference group 10 subjects whose only HBV routine marker was anti-HBc. Seventy-nine percent of the HBeAg positive carriers showed detectable HBV-DNA by a non-radioactive slot-blotting technique. The PCR assay was more sensitive than the slot-blotting technique, detecting HBV-DNA in anti-HBe positive patients with moderate or normal ALT activity. Pre-S1 antigen was mostly related to the presence of HBsAg and anti-pre-S2 was associated with active viremic state, increased ALT activity (ranges 51 to 640 IU/L), and with self-limited HBV infection. The presence of HBV-DNA in the group with anti-HBc only was detectable solely by the PCR assay. For an underdeveloped country the addition of a PCR assay or pre-S/anti-pre-S protein tests to the current assessment procedures of HBV chronic infection should be used only in selective cases. HBeAg/anti-HBe serological evaluation and HBV-DNA detection by a non-isotopic conventional hybridization technique still remain as useful tools to screen initially for the presence of viremia in chronic HBsAg carriers. The presence of HBV-DNA in individuals with anti-HBc only suggests that anti-HBc screening should be maintained and expanded to all the blood banks of less industrialized countries where the rate of HBV infection in apparently healthy people tends to be high.

Intrahepatic expression of pre-S1 and pre-S2 antigens in chronic hepatitis B virus infection in relation to hepatitis B virus replication and hepatitis delta virus superinfection

Hepatocyte expression of pre-S1 and pre-S2 in relation to hepatitis B virus replication (hepatitis B virus-DNA in serum and HBcAg in the liver), histological activity and hepatitis delta virus superinfection was studied by indirect immunofluorescence on frozen sections of liver specimens from 68 patients with chronic hepatitis B virus infection. All 44 patients with chronic type B hepatitis had pre-S1 and pre-S2 display in the liver. The distribution of pre-S1 in the liver was membranous in one, mixed membranous and cytoplasmic in 12, and cytoplasmic in 31. The distribution of pre-S2 was membranous in one, mixed membranous and cytoplasmic in 26, and cytoplasmic in 17. Membranous expression of pre-S1 was significantly more prevalent in patients with active hepatitis B virus replication than in those without (13/28 v 0/16, p < 0.001), regardless of the histological activity, as was membranous expression of pre-S2 (27/28 v 0/16, p < 0.001). In contrast, a significantly higher extent of cytoplasmic expression of pre-S1 and pre-S2 was noted in patients without active hepatitis B virus replication than in those with. Of 24 patients with chronic type D hepatitis virus, eight had active hepatitis B virus replication, and the other 16 did not. The distribution and quantitative expression of pre-S1 and pre-S2 in the liver in these patients also correlated significantly with the status of hepatitis B virus replication and, moreover, showed little or no difference from those without hepatitis delta virus infection. In conclusion, all patients with chronic type B hepatitis had synthesis and display of pre-S1 and pre-S2 in the liver. The distribution and quantitative expression of pre-S1 and pre-S2, however, were closely related to the status of hepatitis B virus replication, but not to the histological activity. Hepatocyte expression of pre-S1 and pre-S2 in chronic type D hepatitis also correlated significantly with status of hepatitis B virus replication, and was not modulated by concurrent hepatitis delta virus infection.

Hepatitis B virus infection and primary hepatocellular carcinoma

For many years, epidemiological studies have demonstrated a strong link between chronic hepatitis B virus (HBV) infection and the development of primary hepatocellular carcinoma (PHC). Other hepatocarcinogens such as hepatitis C virus and aflatoxin also contribute to hepatocarcinogenesis either in conjunction with HBV infection or alone. Cellular and molecular biological studies are providing explanations for the HBV-PHC relationship, and models are now being formulated to further test the relative importance of various factors such as viral DNA integration, activation of oncogenes, genetic instability, loss of tumor suppressor genes, and trans-activating properties of HBV to the pathogenesis of PHC. Further research will probably define more than a single mechanism whereby chronic HBV infection results in PHC.

High-level expression of hepatitis B viral antigens in fibrosing cholestatic hepatitis

The expression of hepatitis B viral antigens was quantified in liver tissue from four transplant recipients with fibrosing cholestatic hepatitis (FCH) and compared with five other transplant recipients who did not develop this syndrome and 30 patients with chronic hepatitis B virus (HBV) infection. As measured by radioimmunoassays, the liver tissue from patients with FCH had significantly greater amounts of both hepatitis B surface antigen (HBsAg) and nucleocapsid antigens than to transplant patients without this syndrome (P less than 0.01) or patients with chronic HBV infection (P less than 0.001). Intrahepatic expression of pre-S1/pre-S2 in FCH was also extensive with a distribution parallel to that of HBsAg. High-level expression of intrahepatic HBsAg and hepatitis B core antigen in the explanted liver was associated with subsequent development of FCH in the liver graft, suggesting that viral/host factors may also be important. This pattern of intrahepatic hepatitis viral antigen expression, by analogy with Chisari's transgenic mice model and Roingeard's HBV-transfected HepG2 cell model, may be the cause of direct hepatocytopathic injury in this condition.

The position of heterologous epitopes inserted in hepatitis B virus core particles determines their immunogenicity

The nucleocapsid (HBcAg) of the hepatitis B virus (HBV) has been suggested as a carrier moiety for vaccine purposes. We investigated the influence of the position of the inserted epitope within hybrid HBcAg particles on antigenicity and immunogenicity. For this purpose, genes coding for neutralizing epitopes of the pre-S region of the HBV envelope proteins were inserted at the amino terminus, the amino terminus through a precore linker sequence, the truncated carboxy terminus, or an internal site of HBcAg by genetic engineering and were expressed in Escherichia coli. All purified hybrid HBc/pre-S polyproteins were particulate. Amino- and carboxy-terminal-modified hybrid HBc particles retained HBcAg antigenicity and immunogenicity. In contrast, insertion of a pre-S(1) sequence between HBcAg residues 75 and 83 abrogated recognition of HBcAg by 5 of 6 anti-HBc monoclonal antibodies and diminished recognition by human polyclonal anti-HBc. Predictably, HBcAg-specific immunogenicity was also reduced. With respect to the inserted epitopes, a pre-S(1) epitope linked to the amino terminus of HBcAg was not surface accessible and not immunogenic. A pre-S(1) epitope fused to the amino terminus through a precore linker sequence was surface accessible and highly immunogenic. A carboxy-terminal-fused pre-S(2) sequence was also surface accessible but weakly immunogenic. Insertion of a pre-S(1) epitope at the internal site resulted in the most efficient anti-pre-S(1) antibody response. Furthermore, immunization with hybrid HBc/pre-S particles exclusively primed T-helper cells specific for HBcAg and not the inserted epitope. These results indicate that the position of the inserted B-cell epitope within HBcAg is critical to its immunogenicity.

Expression of pre-S1, pre-S2, S and X peptides in relation to viral replication in livers with chronic hepatitis B

The expression of large (pre-S1), middle (pre-S2), major S (S) polypeptides of the envelope (HBs) and X peptides of hepatitis B virus (HBV) was investigated in 37 liver specimens with chronic hepatitis B by indirect immunoperoxidase staining. Primary antisera utilized were polyclonal ones against HBs (poly-HBs), core (HBc) and X and monoclonal ones against pre-S1, pre-S2 and S with (particle-S) or without (peptide-S) conformational structure. The localization of HBs proteins in hepatocytes was classified into three types: diffuse, membranous and inclusion. The peptide-S and pre-S2 were expressed at nearly the same frequency as poly-HBs in all types, whereas particle-S was found less frequently (18/29 cases) in the inclusion type, and pre-S1 was recognized relatively rarely (9/33 cases) in the membranous type. As for staining intensity, peptide-S and pre-S2 were almost identical to poly-HBs which stained the most strongly among all three staining types. Particle-S was similar to poly-HBs in the membranous type, but was weak in the inclusion type in the majority. While pre-S1 was stained in a similar intensity to poly-HBs in the diffuse and inclusion types, it was weak or negative in the membranous type. Thus, envelope particles indicated by particle-S staining appeared to be located most frequently in the membranous type, but their assembly might be suppressed in the inclusion type where pre-S1 was well expressed. The X peptide was more frequently detected in the liver with serum HBe antigen and/or HBV DNA. The X peptide was stained exclusively in the cytoplasm of hepatocytes and was correlated with the cytoplasmic HBc antigen. The X peptide was not observed differently between cases with and those without cirrhosis. This suggests that the expression of X peptide tends to occur with virus replication but not with disease progression.