Pre-S encoded surface proteins in relation to the major viral surface antigen in acute hepatitis B virus infection

Rupestonic Acid Derivative YZH-106 Promotes Lysosomal Degradation of HBV L- and M-HBsAg via Direct Interaction with PreS2 Domain

Hepatitis B surface antigen (HBsAg) is not only the biomarker of hepatitis B virus (HBV) infection and expression activity in hepatocytes, but it also contributes to viral specific T cell exhaustion and HBV persistent infection. Therefore, anti-HBV therapies targeting HBsAg to achieve HBsAg loss are key approaches for an HBV functional cure. In this study, we found that YZH-106, a rupestonic acid derivative, inhibited HBsAg secretion and viral replication. Further investigation demonstrated that YZH-106 promoted the lysosomal degradation of viral L- and M-HBs proteins. A mechanistic study using Biacore and docking analysis revealed that YZH-106 bound directly to the PreS2 domain of L- and M-HBsAg, thereby blocking their entry into the endoplasmic reticulum (ER) and promoting their degradation in cytoplasm. Our work thereby provides the basis for the design of a novel compound therapy to target HBsAg against HBV infection.

Hepatitis B Surface Antigen Isoforms: Their Clinical Implications, Utilisation in Diagnosis, Prevention and New Antiviral Strategies

The hepatitis B surface antigen (HBsAg) is a multifunctional glycoprotein composed of large (LHB), middle (MHB), and small (SHB) subunits. HBsAg isoforms have numerous biological functions during HBV infection-from initial and specific viral attachment to the hepatocytes to initiating chronic infection with their immunomodulatory properties. The genetic variability of HBsAg isoforms may play a role in several HBV-related liver phases and clinical manifestations, from occult hepatitis and viral reactivation upon immunosuppression to fulminant hepatitis and hepatocellular carcinoma (HCC). Their immunogenic properties make them a major target for developing HBV vaccines, and in recent years they have been recognised as valuable targets for new therapeutic approaches. Initial research has already shown promising results in utilising HBsAg isoforms instead of quantitative HBsAg for correctly evaluating chronic infection phases and predicting functional cures. The ratio between surface components was shown to indicate specific outcomes of HBV and HDV infections. Thus, besides traditional HBsAg detection and quantitation, HBsAg isoform quantitation can become a useful non-invasive biomarker for assessing chronically infected patients. This review summarises the current knowledge of HBsAg isoforms, their potential usefulness and aspects deserving further research.

Serum hepatitis B virus large and medium surface proteins as novel tools for predicting HBsAg clearance

Background

There is still lack of reliable predictors for hepatitis B surface antigen (HBsAg) clearance. Recent studies have shown that the levels of large (LHBs) and medium hepatitis B surface proteins (MHBs) are closely related to antiviral efficacy. This study aimed to investigate the possibility of LHB and MHB levels to predict HBsAg clearance.

Methods

An inactive HBsAg carriers (IHCs) cohort that had received pegylated interferon (Peg-IFN) treatment was divided into the HBsAg-cleared group (R group) and the HBsAg non-cleared group (NR group) based on whether HBsAg was cleared at 96 weeks. We detected the levels of LHBs and MHBs to evaluate the possibility of predicting HBsAg clearance.

Results

There were 39 patients in the R group and 21 in the NR group. The total HBsAg, LHB, and MHB levels at baseline and at 12 weeks were significantly lower in the R group than in the NR group (all p< 0.05). Multivariate logistic regression indicated that LHB and MHB levels at baseline and 12 weeks were independent predictors of HBsAg clearance (OR = 0.435, p = 0.016; OR = 0.136, p = 0.003; OR = 0.137, p = 0.033; OR = 0.049, p = 0.043). The area under the curve (AUC) for the baseline and 12-week LHB and MHB levels was 0.827-0.896, which were greater than that of the total HBsAg level at baseline and 12-week (AUC: 0.654-0.755). Compared with the prediction results of a single indicator, the combination of LHB and MHB levels had better value in predicting HBsAg clearance. The AUCs of combination factor 1, constructed from baseline LHB and MHB, and combination factor 2, constructed from 12-week LHB and MHB, were 0.922 and 0.939, respectively, and the sensitivity (82.05%-100.00%) and specificity (85.71%-100.00%) were both high. The combined indicators based on baseline LHBs ≤ 13.99 ng/mL and MHBs ≤ 7.95 ng/mL predicted HBsAg clearance rate of more than 90%.

Conclusion

Baseline and 12-week LHB and MHB levels can predict HBsAg clearance obtained by Peg-IFN therapy in IHCs, and the predictive value is higher than that of the total HBsAg levels.

Composition of HBsAg is predictive of HBsAg loss during treatment in patients with HBeAg-positive chronic hepatitis B

BACKGROUND & AIMS

During treatment of chronic HBV infections, loss or seroconversion of the HBV surface antigen (HBsAg) is considered a functional cure. HBsAg consists of the large (LHBs), middle (MHBs), and small surface protein (SHBs) and their relative proportions correlate strongly with disease stage. Our aim was to assess the association between HBsAg composition and functional cure during treatment.

METHODS

A total of 83 patients were retrospectively analyzed. HBsAg loss was achieved by 17/64 patients during nucleos(t)ide analogue (NA) treatment and 3/19 patients following treatment with pegylated interferon-alfa2a (PEG-IFN) for 48 weeks. Sixty-three patients without HBsAg loss were matched as controls. LHBs, MHBs and SHBs were quantified in sera collected before and during treatment.

RESULTS

Before treatment, median MHBs levels were significantly lower in patients with subsequent HBsAg loss than in those without (p = 0.005). During treatment, MHBs and LHBs proportions showed a fast decline in patients with HBsAg loss, but not in patients with HBV e antigen seroconversion only or patients without serologic response. MHBs became undetectable by month 6 of NA treatment in all patients with HBsAg loss, which occurred on average 12.8 ± 8.7 (0-52) months before loss of total HBsAg. Receiver-operating characteristic analyses revealed that the proportion of MHBs was the best early predictor of HBsAg loss before NA treatment (AUC = 0.726, p = 0.019). In patients achieving HBsAg loss with PEG-IFN, the proportions of MHBs and LHBs showed similar kinetics.

CONCLUSION

Quantification of HBsAg proteins shows promise as a novel tool to predict early treatment response. These assessments may help optimize individual antiviral treatment, increasing the rates of functional cure in chronically HBV-infected patients.

LAY SUMMARY

The hepatitis B surface antigen (HBsAg) is a key serum marker for viral replication. Loss of HBsAg is considered stable remission, which can be achieved with antiviral treatments. We have investigated whether the ratios of the different components of HBsAg, namely the large (LHBs) and medium (MHBs) HBsAg during different treatments are associated with the occurrence of HBsAg loss. We found that LHBs and MHBs decrease earlier than total HBsAg before HBsAg loss and we propose LHBs and MHBs as promising novel biomarker candidates for predicting cure of HBV infection.

Quantification of large and middle proteins of hepatitis B virus surface antigen (HBsAg) as a novel tool for the identification of inactive HBV carriers

OBJECTIVE

Among individuals with chronic hepatitis B, those with hepatitis B e-antigen (HBeAg)-negative chronic hepatitis (CHB) can be difficult to distinguish from those with HBeAg-negative chronic HBV infection, also referred to as inactive HBV carriers (ICs), but both require different medical management. The level of HBV surface antigen (HBsAg) has been proposed as a marker to discriminate between chronic infection and hepatitis stages. HBsAg consists of large, middle and small HBs. The aim of this study was to determine whether the composition of HBsAg improved the identification of ICs among HBsAg-positive subjects with different phases of HBV infections.

DESIGN

HBV large surface proteins (LHBs) and HBV middle surface proteins (MHBs) were quantified in serum samples from 183 clinically well-characterised untreated patients with acute (n=14) HBV infection, ICs (n=44), CHBs (n=46), chronic HBeAg-positive phase (n=68) and hepatitis delta coinfection (n=11) using an ELISA, with well-defined monoclonal antibodies against the preS1 domain (LHBs) and the preS2-domain (MHBs). A Western blot analysis was used to verify the quantitation of the components of HBsAg. Total HBsAg was quantified using a modified commercially available assay (HBsAg V.6.0, Enzygnost, Siemens, Erlangen).

RESULTS

The composition of HBsAg showed specific patterns across different phases of hepatitis B. Individuals in the IC phase had significantly lower proportions of LHBs and MHBs than patients in acute or chronic phases irrespective of their HBV e-antigen status (p<0.0001) or HBsAg level. Both LHBs and MHBs ratios better predicted the IC phase than total HBsAg levels.

CONCLUSION

Quantification of MHBs, particularly LHBs represents a novel tool for the identification of the IC stage.

Prediction value of serum HBV large surface protein in different phases of HBV infection and virological response of chronic hepatitis B patients

BACKGROUND

Serum HBV large surface protein (HBV-LP) is an envelope protein that has a close relationship with HBV DNA level. This study is to explore the prediction value of HBV-LP in different phase of HBV infection and during antiviral therapy in chronic hepatitis B (CHB) patients.

METHODS

A retrospective study was conducted in 2033 individuals, which included 1677 HBV infected patients in different phases and 356 healthy controls. HBV-LP, HBV serum markers and HBV DNA were detected by ELISA, CMIA and qRT-PCR, respectively. 85 CHB patients receiving PegIFNα or ETV were divided into virological response (VR) and partial virological response (PVR). The dynamic changes of HBV DNA and HBV-LP were observed.

RESULTS

The level of HBV-LP in 2033 individuals was shown as: HBeAg-positive hepatitis > HBeAg-positive infection > HBeAg-negative hepatitis > HBeAg-negative infection > healthy controls. HBV-LP was positive in all patients whose HBV DNA > 1.0E + 06 IU/ml. When HBsAg was <0.05 IU/ml or >1000 IU/ml, HBV DNAs were all negative if HBV-LP < 1.0 S/CO. When HBsAg was between 0.05 IU/ml and 1000 IU/ml, the consistency of HBV-LP with HBV DNA was 100% in case of HBV-LP > 4.0 S/CO in HBeAg-positive patients and HBV-LP > 2.0 S/CO in HBeAg-negative ones. During antiviral therapy, baseline HBV-LP was lower in VR patients than that in PVR patients. The optimal cut-off points to predict VR by baseline HBV-LP were 32.4 and 28.6 S/CO for HBeAg-positive and HBeAg-negative hepatitis patients, respectively.

CONCLUSIONS

HBV-LP may be a useful marker for distinguishing the different phases of HBV infection. Moreover, baseline HBV-LP level can be used for predicting VR of CHB patients.

Kinetics of acute hepatitis B virus infection in humans

Using patient data from a unique single source outbreak of hepatitis B virus (HBV) infection, we have characterized the kinetics of acute HBV infection by monitoring viral turnover in the serum during the late incubation and clinical phases of the disease in humans. HBV replicates rapidly with minimally estimated doubling times ranging between 2.2 and 5.8 d (mean 3.7 +/- 1.5 d). After a peak viral load in serum of nearly 10(10) HBV DNA copies/ml is attained, clearance of HBV DNA follows a two or three phase decay pattern with an initial rapid decline characterized by mean half-life (t(1/2)) of 3.7 +/- 1.2 d, similar to the t(1/2) observed in the noncytolytic clearance of covalently closed circular DNA for other hepadnaviruses. The final phase of virion clearance occurs at a variable rate (t(1/2) of 4.8 to 284 d) and may relate to the rate of loss of infected hepatocytes. Free virus has a mean t(1/2) of at most 1.2 +/- 0.6 d. We estimate a peak HBV production rate of at least 10(13) virions/day and a maximum production rate of an infected hepatocyte of 200-1,000 virions/day, on average. At this peak rate of virion production we estimate that every possible single and most double mutations would be created each day.

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.

Levels of pre-S antigens and HBV DNA in sera from high and low viremic HBV carriers

The biological and clinical significances of pre-S antigens and HBV replication were investigated. Some 125 sera, 28 from HBeAg and 97 from anti-HBe-positive HBsAg, carriers were studied. The aim was to verify whether pre-S antigens could be expressed in serum in complete absence of viremia. Pre-S proteins, determined by an enzyme immunoassay, were found in sera regardless of the presence of HBV DNA, as detected by spot-hybridization. The sera without detectable HBV DNA were investigated further by PCR using specific primers for the S and C regions of HBV. PCR analysis of samples revealed that 4 out of 5 HBeAg and 33 out of 41 (80.5%) anti-HBe positive sera contained HBV-amplified sequences of S and C regions. Pre-S antigen values correlated well with the amounts of HBV DNA in serum detected by PCR in anti-HBe-positive subjects with high titers of pre-S antigens (10(4)-10(6)). In addition, PCR highlighted the presence of HBV DNA sequences in 8 out of 17 (47.1%) pre-S-negative HBsAg-positive sera.

Correlation of preS antigens and clinical status during chronic hepatitis B virus infection

The serum kinetics of preS1 and preS2 antigens has been evaluated in 38 serial samples from eight patients with chronic active (CAH) or chronic persistent (CPH) hepatitis, followed for 2-7 years (mean 4.4 years) in whom liver biopsy was performed at intervals, and in 46 samples from ten asymptomatic HBsAg carriers followed for 4-5 years (mean 4.6 years). Four patterns of preS behaviour have been observed: (1) persistently positive preS1 and preS2; (2) disappearance of preS2; (3) disappearance of both preS1 and preS2; and (4) persistently negative preS1 and preS2. Pattern 4 has been observed exclusively among healthy carriers, while seven out of eight chronic patients exhibited either pattern 1 or 2. Among the chronic patients, preS2 disappearance was accompanied or followed by alanine aminotransferase (ALT) normalization. The correlation of preS antigens with conventional viral replication markers showed that 100% of hepatitis B virus (HBV)-DNA-positive and 86.6% of HBeAg-positive sera were preS1/preS2 positive, while 61% of HBV-DNA-negative and 64% of HBeAg-negative sera were preS1/preS2 negative. Our data suggest that continuous monitoring of preS antigens in follow-up sera will allow for an improved prognostic evaluation of chronic HBV infection.

Hepatitis B defective virus with rearrangements in the preS gene during chronic HBV infection

We have found a defective form of HBV2 in a HBsAg- and anti-HBe-positive patient with liver cancer. Viral deletions were identified in the preS coding region using PCR. The presence of deleted HBV forms was observed in serum, PBMC, and liver samples. After sequencing 12 clones were analyzed (subtype adr). In 9 out of 12 clones a 183-bp in-frame deletion was recorded in the preS1 region (2995 to 3177). Three out of 9 clones also yielded rearrangements of the preS2 N-terminal part. Four out of 9 showed numerous point mutations in the preS1 and preS2 sequence. In addition, 3 out of 12 clones, which did not show the 183-bp preS1 deletion were found to have small deletions and insertions in the same part of the preS1 gene. Immunological mapping using monoclonal anti-preS antibodies showed loss of preS epitopes located at the 3'-part of preS1 and the 5'-part of preS2. On the other hand, epitopes mapped to the 5'-part of preS1 and 3' of preS2 were conserved. PBMC were also tested and solely PCR showed the major form of defective HBV with preS1 183-bp deletion. However, viral deletions in the preS gene eliminated the preS2 promotor region and B- and T-cell recognition sites. In contrast to this, the preS1 binding site to hepatocytes was conserved. Therefore, such deletions would potentially lead to an impairment in viral clearance without affecting viral penetration in liver cells, possibly accounting for chronic HBV infection.

Hepatitis B pre-S1 and pre-S2 proteins: clinical significance and relation to hepatitis B virus DNA

Pre-S proteins may have an important role in virus assembly and virus entry into the host cell. The presence of pre-S proteins in serum has also been thought to correlate with active viral replication. To investigate whether pre-S proteins in serum might have additional diagnostic and/or predictive value for liver sequelae in HBV infection, sera from six different serological groups of patients with HBV markers (total number 363) and different manifestations of liver histology were examined for the presence of pre-S1 and pre-S2 proteins using micro-ELISAs. Pre-S1 and pre-S2 proteins were detected significantly more often in HBV-DNA-positive than in HBV-DNA-negative sera from HBsAg carriers. However, pre-S1 and pre-S2 proteins were also found in HBV-DNA-negative HBsAg carriers irrespective of serum HBeAg/anti-HBe or liver histologic findings. These results suggest that the presence of the pre-S1 and or pre-S2 proteins in serum either does not seem to reflect the presence of active viral replication and active liver disease or pre-S proteins are more readily detectable than HBeAg and HB-DNA as measured by a dot-blot technique. Furthermore, the presence of pre-S proteins in serum is strongly correlated with that of HBsAg.

Discrimination of hepatitis B virus (HBV) subtypes using monoclonal antibodies to the PreS1 and PreS2 domains of the viral envelope

We report the production and characterization of murine anti-PreS2 and anti-PreS1 monoclonal antibodies (mAb) and demonstrate their utility in discriminating hepatitis B virus (HBV) subtypes. On the basis of Western blotting and reciprocal competition binding to HBV virions, at least five distinct epitopes have been identified in the PreS domain: two within the PreS1 region and three within the PreS2 region. All PreS2 mAb bind M protein (gp33 and gp36) but only one group binds strongly to M and L proteins (p39 and gp42). This group determinant was mapped to peptide residues 120-145. The second group bound to an endoglycosidase F-sensitive epitope which is defined by a mannose-rich glycan at ASN 123 in the PreS2 region. The third group was mapped to peptide residues 150-174 and was reactive with the M envelope proteins but not L or S proteins on Western blots. All PreS1 mAb bind L protein but not M protein on Western blots. Using these mAb, HBV subtype assays were developed allowing evaluation of the Paris (1975) HBsAg subtype panel members along with other HBsAg-positive specimens. All Paris subtype members (except ayw2 and ayw3) could be easily distinguished by differential PreS2 mAb reactivity. The Paris subtypes, adw2, adw4, and adr, could be classified as distinct groups by PreS2 and PreS1 mAb binding. Specimens from Hong Kong and the United States classified as adw2 in the S region fell into two groups based on PreS2 mAb binding: one having reactivity similar to Paris adw2 subtype and the other having identical reactivity to Paris ayw1 subtype. Furthermore, some specimens classified as adr in the S region gave similar reactivity to the Paris ayr subtype in the PreS2 and PreS1 regions. One complicating factor in this approach toward subtyping was the discovery that some HBsAg positive sera may contain factors which block PreS epitopes. Grouping of HBV subtypes by PreS1, PreS2, and S mAb reactivity may allow better correlation with groupings based on HBV DNA sequence homology.

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

The envelope of hepatitis B virus consists of large, middle, and small hepatitis B surface proteins. Recent data from in vitro studies suggest that intracellular expression and distribution of the three polypeptides may be variable. These observations in artificial expression systems prompted this analysis of the occurrence and distribution of the three hepatitis B surface proteins in the liver tissue of substantial viremic (hepatitis B virus DNA- and hepatitis B e antigen-positive) and low-viremic or nonviremic (hepatitis B virus DNA-negative, anti-hepatitis B e antigen-positive) carriers by specific monoclonal antibodies against large, middle, and small proteins. Patients with an active form of viral replication showed a prevalence of middle and small hepatitis B surface proteins in the liver. In nonviremic carriers, the large hepatitis B surface protein was the predominant intrahepatic antigen, a finding that was confirmed at the ultrastructural level by staining of the entire filaments of the viral envelope material in ground glass hepatocytes. The present data are thus consistent with observations in hepatitis B virus-transgenic mice and in transfected cell systems, suggesting that the different patterns of the envelope proteins in the liver may be due to different processing at the translational level.

Assay of preS epitopes and preS1 antibody in hepatitis B virus carriers and immune persons

The diagnostical significance of the large hepatitis B surface protein with its preS1 attachment site and of anti-preS antibodies are not yet well known. We investigated the epitope of the preS1 attachment site to see whether it is a marker of viremia and whether antibodies against it occur in convalescents and vaccinees. For comparison, sera were also tested for the presence and relative amount of a preS2 epitope. The epitopes were detected by binding to specific monoclonal antibodies (mAb MA18/7 for the preS1 epitope and mAb Q19/10 for the preS2 epitope) at the solid phase of a sandwich enzyme-linked immunosorbent assay. Antibody against the preS1 epitope was detected by inhibition of binding to mAb MA18/7. This mAb inhibits attachment of preS1 antigen to hepatocytes and reacts with a subtype-independent sequential epitope at the surface of hepatitis B virus between amino acid 29-36. This preS1 epitope occurs in most hepatitis B surface antigen (HBsAg) carriers, irrespective of viremia. Free preS2 epitope Q19/10 is present in samples with more than 8 micrograms/ml total HBsAg and it is masked in sera with less HBsAg. Antibodies which compete with mAb MA18/7 for its viral preS1 epitope occur in one third of HBsAg carriers who were negative for hepatitis B e antigen. It also occurs in one third of convalescents and in most good responders to plasma-derived vaccines.

Immune blot analysis of viral surface proteins in serum and liver of patients with chronic hepatitis B virus infection

The small and the middle surface proteins of hepatitis virus form either the virion or the 22 nm particle both of which are secreted. The large surface protein by itself remains cell bound in artificially transfected cell culture unless it is accompanied by an excess of the smaller protens. Its behavior in vivo is not yet well studied. Using specific monoclonal antibodies for immunoblotting, we found an abundance of small surface protein in the serum of chronic virus carriers and moderate amounts in the liver irrespective of viremia. The large surface protein was present in the serum and the liver of viremic carriers. In nonviremic carriers, the large protein was absent from serum, but in the liver a shorter form of the large protein was readily detectable. These findings suggest a complex regulatory mechanism of the viral surface protein depending on the expression of other viral gene products.

Immunology of hepatitis B virus infections

Acute or chronic hepatitis B virus infection is often associated with symptoms which are probably caused by immune complexes, such as vasculitis, glomerulonephritis and arthritis. The immune complexes found in such patients contain excessive viral proteins. The functions of these proteins and the immune response to them during various states of infection are discussed.

Clearance of hepatitis B virus DNA and pre-S surface antigens in patients with markers of acute viral replication

To clarify the relationship between the pre-S antigens and other serological markers of hepatitis B virus (HBV) replication, we followed up 27 patients: 21 presented with symptoms of acute hepatitis (two progressed to chronicity) and six suffered from chronic hepatitis. Pre-S1, pre-S2, HBV DNA, IgM antihepatitis core antigen (HBc), hepatitis B e antigen (HBeAg), and anti-HBe were detected in about 200 sera serially collected at different times for at least 6-12 months from the onset of clinical observation. In the early symptomatic phase of acute hepatitis, the pre-S1 and pre-S2 antigens were present in 95% of the cases and correlated well with high levels of alanine-transferase (ALT) and IgM anti-HBc, while HBV DNA was present in the sera of only six (28.6%) patients (P less than 0.0001). This was the first marker to disappear (1 month after the initial stage). All of the HBV DNA-positive patients were also HBeAg positive, whereas no HBeAg-negative subjects were found with serum HBV DNA. In the six chronic patients, pre-S antigens were always present independently of the HBeAg/anti-HBe status; HBV DNA was detected in three of them, even if transiently, and in two of these it reappeared together with pre-S2 epitope. The follow-up data suggest that, in acute hepatitis, the clearance of pre-S antigens can be considered as a prognostic index of clinical resolution and that, in chronic hepatitis, the persistence of pre-S antigens seems to indicate progression of the disease. In particular, pre-S2, in patients in whom it is intermittent, can be considered as an index of reactivation.

Expression and clinical significance of pre-S1 and S2 proteins of HBV in sera of patients with chronic liver disease

To assess the significance of pre-S proteins expression during chronic hepatitis B virus (HBV) infection, we developed a sensitive labeled avidin biotin ELISA to detect pre-S1 and pre-S2 proteins. In serum specimens from 80 patients with chronic liver disease, the frequency of pre-S1 and S2 proteins was 53.7% and 47.5%, respectively. Furthermore, it reached 87.8% and 77.6%, respectively, in cases with chronic HBV infection, indicating that pre-S proteins are usually expressed in sera with chronic HBV infection. We found that the expression of pre-S proteins is closely associated with HBV replicating markers, such as HBV DNA, HBcAg and HBeAg, in sera of patients with chronic HBV infection. Both pre-S1 and S2 proteins were often concurrently expressed in liver and serum with chronic HBV infection. However, the frequency was slightly higher in liver than in serum, suggesting that it may be clinically valuable to detect pre-S proteins in serum and liver simultaneously to determine the status of HBV infection. Our results also indicated that pre-S proteins expression in serum can serve as markers of HBV infection, but cannot be used to estimate the severity and activity of hepatic pathology.

Serum titers of pre-S(2) antigen in patients with acute and chronic type B hepatitis: relation to serum aminotransferase activity and other hepatitis B virus markers

The peptide which is encoded by the pre-S(2) region of hepatitis B virus DNA, the pre-S(2) antigen, was determined quantitatively by an enzyme immunoassay system employing monoclonal antibodies. The prevalence and titer of pre-S(2)Ag were 91.9% (91/99) and 10,356 +/- 19,053 units (mean +/- S.D., arbitrary units) for hepatitis B e antigen (HBeAg)-positive patients with acute and chronic HBV infection and 86.0% (74/86) and 952 +/- 1,565 units for HBeAg-negative subjects. In four patients with acute hepatitis B, pre-S(2)Ag titers changed in parallel with HBV DNA levels, and the disappearance of pre-S(2)Ag from serum was associated with a rapid fall of ALT levels into the normal range, whereas the fluctuation of pre-S(2)Ag titer correlated with persistence of ALT elevations. In all of the 19 episodes of acute exacerbation of hepatitis which occurred in nine patients with chronic active hepatitis B, a significant elevation of pre-S(2)Ag titer was observed, closely overlapping an increase or appearance of HBV DNA, and its peak preceded peaks of ALT by 1 to 11 weeks (mean +/- S.D. = 4.26 +/- 2.57 weeks). These observations suggest that quantitative measurement of pre-S(2)Ag would be useful for estimation of the magnitude of HBV replication and would help predict the prognosis of acute hepatitis B and of acute exacerbation in chronic hepatitis B.

Occurrence of pre-S1 antigen in viremic and nonviremic carriers of hepatitis B surface antigen

The proteins of viral envelope, encoded by the pre-S1 region of HBV-DNA, were measured quantitatively with enzyme immunoassay using monoclonal antibodies directed to pre-S1 epitope and correlated with the expression of pre-S2 region encoded epitope and other HBV markers. In acute HBV infection, both pre-S encoded proteins were detected in sera along with markers of viral replication and disappeared shortly before complete virus clearance while high HBsAg titers were still present. Pre-S1 antigen was present in most (95.5%) symptomatic and asymptomatic chronic HBsAg carriers. There was no correlation between the presence of pre-S1 and HBeAg or HBV-DNA in serum: 73% of sera with pre-S1 determinants were anti-HBe positive, and only 25.4% were positive for HBV-DNA. Most pre-S1 activity in sera of viremic carriers was detected in fractions of sucrose gradient containing subviral 22-nm particles, and much less in those containing infectious virions. In asymptomatic, nonviremic HBsAg carriers, pre-S1 was located only on subviral 22-nm forms. Pre-S1 positive particles had no accessible pre-S2 epitope, which is recognized specifically by monoclonal anti-pre-S2 (F124) antibody. These results show that the synthesis of the large protein of HBV envelope may occur also in the absence of active viral replication, and in these cases pre-S1 encoded sequences are on subviral particles of HBsAg. Therefore, pre-S1 is not a serologic marker of infectious virus. Disappearance of pre-S1 epitopes on HBsAg occurs only before complete clearance of the virus, and this may have potential prognostic relevance.

Reactivation of chronic type B hepatitis: the effect on expression of serum HBV-DNA and pre-S encoded proteins

Hepatitis B markers were studied in seven patients with reactivated liver disease. Reactivation of chronic type B hepatitis, as indicated by the reappearance of hepatitis B e antigen (HBeAg) in the serum, was characterised by the appearance of hepatitis B virus-DNA (HBV-DNA) in the serum. The expression of pre-S 1 encoded protein remained unchanged in five of seven patients, and poly-HSA as a marker for pre-S 2 encoded protein remained detectable in six of seven patients before and after reactivation of chronic hepatitis. The level of serum HBV-DNA correlated well with the level of liver enzymes, which rose from normal to various levels after reactivation of the liver disease. The data suggest that inflammatory activity of the liver disease is not related to the expression of pre-S encoded protein but to viral replication. Possibly pre-C and C-gene encoded antigens, which are produced together with viral nucleic acid and expressed on the surface of HBV-infected liver cells, play the key role in liver damage believed to be mediated by cytotoxic T cells.

Methods for the study of pre-S proteins of hepatitis B virus and their antibodies: pathogenetic and clinical implications

The envelope gene of hepatitis B virus (HBV) consists of a large open reading frame which codes 3 different polypeptides by the variable use of 3 contiguous regions: the pre-S1, pre-S2 and S regions. The protein coded by the entire sequence (L protein) is identified by its unique pre-S1 epitopes and has a role in virus assembly and secretion. Pre-S1 antigens are expressed preferentially on virions and are less abundant, but present, on subviral particles. The pre-S2 sequence contains a species-specific receptor for polyalbumin, which has been implicated in virus binding to hepatocytes. Methods have been recently developed to measure pre-S1 and pre-S2 levels in serum and available data indicate that these assays may be useful in prognostic assessment of acute hepatitis B and to measure virus replication in chronic infection, although further studies are certainly needed to define specificity and sensitivity compared to conventional HBV markers. Both pre-S1 and pre-S2 are highly immunogenic and elicit anti-pre-S antibodies. Methods for detection of anti-pre-S in human sera have proved difficult to be developed due to unspecific reaction of serum components with pre-S sequences and epitope variability of the immune response in humans. Anti-pre-S2 seems a marker of recovery from acute infection, while evidence of its involvement in liver damage is weak. Both anti-pre-S2 and anti-pre-S1, but we have limited information on the latter, may be involved in virus neutralization. These issues are particularly relevant for future HB vaccine development, as it is proposed that inclusion of strategic pre-S sequences could increase efficacy.