Hepatitis B virus pre-S gene-encoded antigenic specificity and anti-pre-S antibody: relationship between anti-pre-S response and recovery

PreHevbrio: the first approved 3-antigen hepatitis B vaccine

INTRODUCTION

Hepatitis B remains a major cause of death and morbidity worldwide. Universal childhood immunization programs have been very successful, but many adults remain unprotected or are not optimally protected. PreHevbrio [Hepatitis B Vaccine (recombinant)] is a highly immunogenic 3-antigen (S/pre-S1/pre-S2) hepatitis B vaccine (3A-HBV) that recently received marketing authorization in the United States (2021), the European Union, United Kingdom (2022 - brand name PreHevbri), and Canada (2022- brand name PreHevbrio) for the prevention of infection caused by all known subtypes of the hepatitis B virus and the delta virus in adults 18 years and older.

AREAS COVERED

This review details the development of 3A-HBV and summarizes the results of the phase 3 clinical trials that support its immunogenicity and safety in adults.

EXPERT OPINION

3A-HBV is highly immunogenic in adults of all ages, including older adults and subgroups that respond sub-optimally to conventional single S-antigen hepatitis B vaccines (1A-HBV), such as those with obesity, type 2 diabetes, and smokers. 3A-HBV provides higher seroprotection rates after each vaccination compared to conventional 1A-HBV vaccines, allowing for more rapid protection. The higher overall immunogenicity is also reflected in more durable seroprotection years after vaccination, as supported by a follow-up study to one of the phase 3 studies.

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

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

The Hepatitis B Virus Envelope Proteins: Molecular Gymnastics Throughout the Viral Life Cycle

New hepatitis B virions released from infected hepatocytes are the result of an intricate maturation process that starts with the formation of the nucleocapsid providing a confined space where the viral DNA genome is synthesized via reverse transcription. Virion assembly is finalized by the enclosure of the icosahedral nucleocapsid within a heterogeneous envelope. The latter contains integral membrane proteins of three sizes, collectively known as hepatitis B surface antigen, and adopts multiple conformations in the course of the viral life cycle. The nucleocapsid conformation depends on the reverse transcription status of the genome, which in turn controls nucleocapsid interaction with the envelope proteins for virus exit. In addition, after secretion the virions undergo a distinct maturation step during which a topological switch of the large envelope protein confers infectivity. Here we review molecular determinants for envelopment and models that postulate molecular signals encoded in the capsid scaffold conducive or adverse to the recruitment of envelope proteins.

Expression and purification of the synthetic preS1 gene of Hepatitis B Virus with preferred Escherichia coli codon preference

To produce high levels of hepatitis B virus (HBV) preS1 protein at low cost, a DNA fragment encoding the preS1 region, residues 1-119, of HBV adr subtype was synthesized by overlapping-PCR according to Escherichia coli (E. coli) B preferred codon usage. The synthetic preS1 gene (spreS1) was cloned into the bacterial expression vector pET-30a and transferred into the expression strain E. coli BL21(DE3). Recombinant preS1 protein with an N-terminal His6 tag was expressed at high levels in soluble form, yielding about 44% of the total cellular protein. This technique overcomes problems that existed in previously reported expression systems of preS1 or its epitope, i.e., low-level expression or expression in inclusion bodies. Using this His-tagged preS1 expression system, recombinant protein was purified by single-step affinity chromatography on a Ni-NTA column resulting in a yield was about 28 mg recombinant protein per liter culture. Furthermore, Western blotting and indirect ELISA analysis demonstrate that the reactivity of preS1-specific antibody is comparable between the recombinant and commercialized preS1 protein. Thus, our improved expression system could be used for practical, low-cost large-scale production of recombinant preS1 without refolding steps.

A flexible peptide linker enhances the immunoreactivity of two copies HBsAg preS1 (21-47) fusion protein

PreS1 (21-47) region of HBV large surface protein is hepatocyte receptor binding site and the anti-preS1 (21-47) antibody possesses the virus-neutralizing activity and protective effect. It is important to obtain the peptide with higher immunoreactivity on a large scale for detecting the anti-preS1 (21-47) antibody in the sera from HBV infected patients and future vaccine recipients. The expression vector pGEX SLS, which expressed two copies of the preS1 (21-47) peptide connected by a flexible linker (Gly4Ser3) fused to glutathione S-transferase (GST), was constructed. The fusion protein, named GST-SLS, was highly expressed in E. coli and purified by affinity chromatography. Ninety milligrams purified protein can be obtained from 1l of culture. The data in ELISA analysis showed that the immunoreactivity of GST-SLS was enhanced significantly in comparison with GST-S II, a GST fusion protein with two copies preS1 (21-47) linked directly; GST-S I, another GST fusion protein with one copy preS1 (21-47) and preS1 (21-47) synthesized peptide. In addition, GST-SLS has been tried to use in detecting anti-preS1 (21-47) antibody in the sera from HBV infected patients and a satisfied result was gained. Therefore, GST-SLS may have potential to be developed into a new kit for diagnosis and prognosis of hepatitis B (HB) patients.

Identification of a novel pre-S2 mutation in a subgroup of chronic carriers with spontaneous clearance of hepatitis B virus surface antigen

BACKGROUND AND AIM

The aim of the present study was to investigate whether spontaneous seroclearance of hepatitis B surface antigen (HBsAg) in patients with chronic hepatitis B could be attributed to the presence of pre-S/S gene mutations.

METHODS

Of 34 hepatitis B virus (HBV) carriers who experienced spontaneous seroclearance of HBsAg, 30 were still seropositive for HBV DNA. The serum samples of these carriers were subjected to sequence analysis.

RESULTS

A novel pre-S2 mutation, G149R, was found in nine (group I) but not in 17 (group II) patients carrying HBV DNA with intact pre-S/S reading frames. In the remaining four patients (group III), only aberrant pre-S/S transcripts were found in their sera. Distinct patterns of amino acid substitutions specific to group I and II patients were identified. Superinfection by hepatitis C or D virus occurred predominantly in group II patients (P = 0.019). Superinfection by HBV of a different genotype occurred predominantly in patients without hepatitis C or D virus superinfection (P = 0.013). Site-directed mutagenesis experiments showed that secretion of HBsAg was not defective in the pre-S2 G149R mutant.

CONCLUSIONS

In a particular subgroup (group I) of patients, seroclearance of HBsAg was not caused by superinfection of other hepatitis viruses, nor was it caused by failure of HBsAg secretion or detection. Instead, a yet unrecognized mechanism associated with emergence of a novel pre-S2 mutation is responsible.

Development of the diagnostic immunoassay to detect anti-PreS1(21-47aa) antibody--a marker suggesting the health improvement of hepatitis B patients

BACKGROUND

A new immunoassay has been developed for the detection of the anti-PreS1(21-47aa) antibody in sera of hepatitis B virus (HBV)-infected patients. Anti-PreS1(21-47aa) antibody involves virus neutralization and is a new marker for diagnosing acute and chronic B hepatitis.

METHODS

The expression plasmids pGEXS I and pGEXS II, which expressed glutathione S-transferase (GST) fusion proteins containing a copy of PreS1(21-47aa) peptide and two orderly joined copies of PreS1(21-47aa) peptide, were constructed. The soluble expression products were purified by affinity chromatography.

RESULTS

The two PreS1(21-47aa) fusion proteins were both successfully applied in the immunoassay based on biotin-protein A and streptavidin-HRP, and could detect the anti-PreS1(21-47aa) antibody with high sensitivity in sera from hepatitis B patients. The anti-PreS1(21-27aa) antibody was detected during the recovery phase of acute hepatitis B patients, but it was found only in few of the chronic carriers by the established conventional system.

CONCLUSIONS

The follow-up study suggested that the presence of the anti-PreS1(21-27aa) antibody correlated well with the recovery of patients from hepatitis and the improvement in health.

Hypermodification and immune escape of an internally deleted middle-envelope (M) protein of frequent and predominant hepatitis B virus variants

Naturally occurring deletions within the human hepatitis B virus (HBV) preS2 region have frequently been identified in patients with hepatocellular carcinoma (HCC), while chronic carriers without cirrhosis and HCC contain no detectable preS2 deletion variants. We have characterized two different preS2 internal deletion variants from two patients. In addition to several weak phenotypes, our study revealed three unexpected strong phenotypes: (1) a paradoxical "hypermodification" phenomenon was observed with significantly increased size heterogeneity and molecular weights of the secreted middle (M) envelope proteins containing a preS2 internal deletion. This phenomenon was observed in transient transfection with a human hepatoma Huh7 cell line as well as in stable transfection with a rodent hepatoma cell line 7777. (2) A significantly increased intracellular accumulation of all three envelope proteins (large, middle, and small) was detected by both Western blot analysis and immunofluorescence microscopy. (3) The middle envelope proteins with a preS2 internal deletion were not recognized in vitro by a putative neutralizing antiserum, suggesting that these variants can evade immune recognition in vivo. To our knowledge, this is the first identification and characterization of the M deletion variant protein in HBV natural infection.

Expression and characterization of chimeric hepatitis B surface antigen particles carrying preS epitopes

Many studies have provided evidence that hepatitis B surface antigen (HBsAg) including preS1 and preS2 sequences could be an ideal candidate for a new hepatitis B virus (HBV) vaccine with higher efficacy. However, the large (L) protein containing the entire preS region expressed in mammalian cells is not efficiently assembled into particles and secreted. Here we report an alternative approach to include the dominant epitopes of preS1 and preS2 to the small (S) protein as fusion proteins by the recombinant DNA technology. Three fusion proteins containing preS2(120-146) and preS1(21-47) at the N-terminus and/or truncated C-terminus of S protein were expressed using the recombinant vaccinia virus system. All these fusion proteins were efficiently secreted in the particulate form, and displayed S, preS1 and/or preS2 antigenicity. Further analysis showed that these chimeric HBsAg particles elicited strong antibody responses against S, preS1 and preS2 antigens in BALB/c mice, suggesting that they could be promising candidates for a new recombinant vaccine to induce broader antibody response required for protection against hepatitis B viral infection.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults

The safety and immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) were compared with those of a vaccine prepared with S alone (Engerix-B). S-L* consisted of composite particles containing S and L* at a ratio of 70/30. L* encompassed amino acid residues 12-52 of preS1 residues 133-145 of preS2, and the entire S domain. A total of 100 healthy, HBV-seronegative, young adults were randomized to receive 20 micrograms/dose of either S-L* or Engerix-B under double-blind conditions according to a 0-, 1-, 2-, 12-month schedule. In vivo humoral and in vitro lymphoproliferative responses to S and preS regions were monitored. Addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response but improved the in vitro stimulating capacity of the antigen (L*) in S-L* primed subjects.

Reactogenicity and immunogenicity of a new recombinant hepatitis B vaccine containing Pre S antigens: a preliminary report

A new vaccine against hepatitis B virus (HBV) infection, produced in mammalian Chinese hamster ovary (CHO) cells, contains the small(s), middle (Pre S2) and large (Pre S1) surface proteins of HBV. Three injections of a 5-micrograms or 10-micrograms dose were administered intramuscularly (i.m.) at 0, 1 and 6 months to a group of 105 young adults, who were monitored for a period of 6 months after the third injection. Seroconversion rates were 100% after the second injection of the 5-micrograms or 10-micrograms dose. Geometric mean titres of HBsAb at 1 month after the third injection were 12,156 mIU ml-1 and 13,482 mIU ml-1 in those receiving the 5-micrograms and 10-micrograms dose respectively. The vaccine was well tolerated with no significant adverse events. These preliminary results suggest that the Pre S-s recombinant vaccine, produced in mammalian cells, is highly immunogenic, leading to 100% seroconversion in the population tested after injection of only two doses of 5 micrograms.

Weak immunogenicity of the preS2 sequence and lack of circumventing effect on the unresponsiveness to the hepatitis B virus vaccine

The preS2 sequence is known to circumvent immunological unresponsiveness to the S protein and to induce a 'carrier' effect on the anti-S antibody production, in mice. In humans, an anti-S response was found in 100% and 97% of healthy subjects vaccinated with the S and S + preS2 preparations, respectively, whereas less than 50% of drinkers responded whatever the vaccine used. Anti-preS2 were found in 44% of healthy recipients of the S + preS2 vaccine, whereas there were no anti-preS2 responders in drinkers. Anti-preS2 remained undetectable in 32% of the blood donors hyperimmunized with the S + preS2 vaccine, whereas anti-S antibody boosted in all cases. In humans, in contrast to mice, immunogenicity of the preS2 sequence appears weak and the preS sequence does not circumvent the anti-S unresponsiveness.

Expression and characterization of the multiplied, recombinant preS1 antigen of hepatitis B virus

The amino acid sequence encoded by the preS1 region of hepatitis B virus genome is expressed on the surface of virions and subviral particles. The preS1 region is involved in the recognition of specific receptors responsible for the attachment of HBV to the host cell. The cell receptor binding site was assigned to the preS1 (20-47 aa) fragment. In order to obtain a large quantity of preS1 binding domains of HBV the expression vector pWX4 was constructed. It contains four tandemly joined DNA sequences, each coding for preS1 (20-49 aa), fused with the 3' end of a DNA fragment coding for 450 aa of beta-galactosidase. E. coli cells transformed with this vector produce fusion protein beta-gal-preSlx4 in the form of inclusion bodies. Owing to the specific trypsin digestion, the preSlx4 domain was cleaved from the fusion protein. The resulting product, a 16 kDa protein, was isolated and purified by anion exchange chromatography. The presence of four Asp-Pro bonds in this sequence and the primary structure of the first 28 N-terminal amino acids were determined. Following the confirmation of the antigenic properties, the recombinant preS1 protein was used for detection of the anti-preS1 response in sera from HBV infected patients.

Improved immunogenicity in mice of a mammalian cell-derived recombinant hepatitis B vaccine containing pre-S1 and pre-S2 antigens as compared with conventional yeast-derived vaccines

The widely used hepatitis B virus (HBV) vaccines consist of the small hepatitis B surface (SHBs) protein produced in transfected yeast cells. The frequency of non-responders, especially among immunocompromised patients, has increased the demand for a more immunogenic vaccine. We evaluated the immunogenicity of recombinant HBs 20 nm particles secreted by transfected Chinese hamster ovary (CHO) cells, Bio-Hep-B (BioTechnology General Ltd, Israel), and compared it with yeast-derived vaccines. The CHO-derived vaccine contains the small hepatitis B surface antigen (SHBs protein) as the major component, as well as the middle HBs (MHBs, pre-S2) and the large HBs (LHBs, pre-S1) antigens. Nine groups of ten female Balb/c mice, 4-6 weeks old, were injected once intraperitoneally (i.p.) with 0.09, 0.27 or 0.81 micrograms of each of three vaccines: Bio-Hep-B or two conventional yeast-derived recombinant vaccines, Engerix-B (SmithKline Beecham, Belgium) and H-B-Vax II (Merck, Sharp & Dohme, USA) containing only non-glycosylated SHBs antigen. After 30 days, 40% of the mice injected with 0.09 microgram Bio-Hep-B had seroconverted, but none of the mice receiving the same dose of the other vaccines. The immunogenic dose in 50% of the mice at day 14 after injection was 0.13 microgram for Bio-Hep-B, but over 0.81 microgram for the other two vaccines. Mice of the strain B10/M (which are unresponsive to SHBs and MHBs antigens at the T-cell level) developed 100-fold higher anti-HBs titres after immunization with 1 microgram of Bio-Hep-B i.p., as compared with mice receiving the same amount of yeast-derived HBsAg vaccines.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunogenicity of a recombinant Pre-S2-containing hepatitis B vaccine versus plasma-derived vaccine administered as a booster

GenHevac B Pasteur is a recombinant hepatitis B vaccine derived from a mammalian cell line and containing HBs as well as pre-S2 antigens. Its immunogenicity was compared to that of the plasma-derived vaccine Hevac B Pasteur in a population primovaccinated 5.5 years earlier with four injections of the same plasma vaccine. The booster injection with either GenHevac or Hevac was administered to 295 subjects with residual anti-HBs titres below 500 IU/l (group 1: 0-9; group 2: 10-99; group 3: 100-499 IU/l). After four weeks, GenHevac had induced higher anti-HBs responses than Hevac in all groups, particularly among the low responders of group 1. Response to the vaccine occurred earlier with GenHevac. Mean anti-pre-S2 production was moderate in all groups for both vaccines (GenHevac: 60 IU/l; Hevac: 31 IU/l) and was not found in the 32 subjects who produced less than 100 IU/l anti-HBs. The results of the present study indicate that GenHevac is at least as immunogenic as Hevac.

Duck hepatitis B virus (DHBV) as a model for understanding hepadnavirus neutralization

The role of the immune response to the human hepatitis B virus (HBV) envelope proteins in neutralization of viral infectivity has been well documented. The similarity between HBV, prototype member of the hepadnavirus family, and the closely related duck hepatitis B virus (DHBV) has allowed, use of the latter as a convenient model for the study of molecular mechanisms of HBV replication and neutralization. In this brief review, we will examine the HBV and DHBV envelope proteins and their role as targets for virus neutralization.

Electron microscopic study of hepatitis B virus-associated antigens on the infected liver cell membrane in relation to analysis of immune target antigens in chronic hepatitis B

To clarify the characteristics of cell surface Pre-S2 Ag, HBcAg and HBeAg immunohistochemically and to explore their relationship with a cellular immune target antigen, 31 liver biopsy specimens from chronic HBV carriers were examined by immunoperoxidase staining. By immune light microscopy, Pre-S2 Ag was detected on the liver cell membrane in 18 (58%) of the 31 cases, HBcAg in 4 cases (13%) and HBeAg in 4 cases (13%). Pre-S2 Ag frequently showed a honeycomb-like membrane expression pattern which was present regardless of liver inflammation, whereas HBcAg and HBeAg exhibited a scattered membrane expression pattern detected in areas of marked inflammation. Of the 18 cases showing a honeycomb-like Pre-S2 Ag expression, 3 concomitantly showed a scattered membrane expression pattern. Immunoelectron microscopy revealed these two distinct membrane expression patterns. In areas showing a honeycomb-like membrane expression pattern, Pre-S2 Ag was demonstrated in the intercellular space and on the basolateral membranes of hepatocytes, but was not detected on the cell membranes in areas of the intercellular space lacking an immunoreaction. Cytoplasmic expression of Pre-S2 Ag was less extensive in these hepatocytes. These findings suggest that the honeycomb-like membrane expression of Pre-S2 Ag results from attachment of extracellular antigen to the liver cell membrane. In contrast, in areas showing a scattered membrane expression pattern, Pre-S2 Ag, HBcAg and HBeAg were each detected as single-layered linear deposits along the cell membrane, but were absent in the intercellular space. Each antigen was also expressed abundantly in the cytoplasm, and the immunoproducts appeared to fuse with the cell membrane. These findings suggest that the scattered membrane expression of these antigens results from intrahepatic transfer of antigen synthesized in the liver cell to the cell membrane, possibly serving as a target for the host immune-mediated response in connection with inflammation.

Serum pre-S1 and pre-S2 antigens as prognostic markers in interferon therapy for chronic hepatitis B

We investigated the changes of serum pre-S1 and pre-S2 antigens before and after interferon therapy in 35 carriers with HBeAg, to examine their clinical significance in the therapy. Both antigens were measured quantitatively by solid-phase enzyme immunoassays using monoclonal antibodies specific to each antigen. The titers of these antigens of responders before therapy were significantly lower (p less than 0.001) than those of non-responders (6.23 +/- 1.09 versus 8.65 +/- 2.09 and 4.46 +/- 1.27 versus 6.50 +/- 1.50, respectively). The titers decreased significantly 6 months after interferon therapy in the responders (p less than 0.05), whereas they did not change in the non-responders. Our findings indicate that pre-S1 and pre-S2 antigens have a close correlation with hepatitis B virus replication and are valuable markers for predicting the responsiveness to interferon therapy.

PCR analysis of HBV infected sera: relationship between expression of pre-S antigens and viral replication

In order to determine the biological significance of the pre-S antigens in HBV infection, HBsAg sera were tested for the presence of pre-S1 and pre-S2. HBV DNA was detected by spot-hybridization and PCR. The data show a complete correlation between pre-S antigenemia and HBV DNA replication in anti-HBe positive cases. PCR but not spot-hybridization was adequately sensitive to also detect HBV DNA in roughly half of the preS negative sera as well. Thus PCR appears to be a valuable technique for detection of potentially infectious anti-HBe carriers.

Anti-pre-S responses and viral clearance in chronic hepatitis B virus infection

Serial sera were collected prospectively during the clinical course of 13 HBsAg carriers with chronic liver disease and analyzed for ALT levels, pre-S1 and pre-S2 antigens and corresponding antibodies and other serological hepatitis B virus markers. In five patients, anti-pre-S1 and anti-pre-S2 antibodies became detectable in multiple serum samples, whereas in eight patients anti-pre-S was never detected or only appeared transiently during the follow-up. The first pattern was associated with normalization of ALT levels and undetectable pre-S antigens and viral DNA by the polymerase chain reaction assay at final follow-up. HBsAg clearance occurred in two of the five patients. The second pattern was one of persistence of HBsAg and pre-S antigens, associated with the presence of serum HBV DNA detectable by spot hybridization or polymerase chain reaction regardless of clinical outcome. These findings demonstrate the occurrence of anti-pre-S antibodies in chronic hepatitis B virus-induced liver disease and associate anti-pre-S appearance with the clearance of hepatitis B virus from serum.

Immunogenicity and safety of a recombinant hepatitis B vaccine produced in mammalian cells and containing the S and the preS2

A group of 273 health care workers, at risk of HBV infection, underwent vaccination with recombinant HBsAg produced in mammalian cells and containing protein sequences coded by both the S and pre-S2 regions (Genhevac B). Preliminary results show that a very early pre-S2 response occurred which may be useful in post-exposure prophylaxis. This observation, in addition to reduced influence by the vaccination protocol, provides grounds for optimism in spite of the fact that the efficiency spectrum of this vaccine was not superior to that of recombinant vaccines produced in yeast.

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.

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.

Prognostic significance of pre-S2 antigen and antibody in fulminant hepatitis B. Evidence for heterogeneous serological responses

Serial sera were collected prospectively and from early on in the clinical course of ten patients with fulminant hepatitis B. These were analysed for HBV DNA (dot-blot technique), HBsAg, HBeAg, pre-S2-Ag and their respective antibodies. Two patterns emerged in nine of the patients. The first and well-recognised pattern of rapid clearance of antigens and appearance of antibodies was seen in four patients, all of whom survived. The second pattern seen in five patients was one of persistence of HBsAg and pre-S2 antigen and failure to detect antibodies but only one patient survived. The first pattern may reflect a more rapid cessation of virus replication and this may favour liver cell regeneration and recovery. In contrast, the second pattern may indicate continuing virus replication and liver cell damage which could contribute to the high mortality in some patients with fulminant hepatitis B.

Evaluation of the pre-S (pre-S(1)Ag/pre-S(2)Ab) system in hepatitis B virus infection

The diagnostic and prognostic value of pre-S(1)Ag and pre-S(2)Ab was investigated in 69 HBsAg surface antigen positive patients--14 with acute hepatitis B, 30 with chronic liver disease (six chronic persistent hepatitis, 14 chronic active hepatitis, 10 with cirrhosis) and in 25 asymptomatic carriers. Pre-S(1)Ag was found in all patients with chronic hepatitis B virus (HBV) infection regardless of viral replication. In contrast, pre-S(2)Ab was not detected in any patients. Acute hepatitis was studied sequentially with periodic controls at 20 day intervals. Pre-S(1)Ag cleared before HBsAg in six of 14 (43%) patients who progressed favourably, and the two antigens cleared simultaneously in eight of 14 (57%) cases. Patients with early clearance of pre-S(1)Ag progressed favourably, thus indicating the prognostic value of this test, which, however, is still of limited practical application given the small temporal difference between the moment of clearance of the two antigens. The first markers to clear, however, were HBeAg and DNA-HBV, which showed significant differences with respect to the clearance of HBsAg. Moreover, pre-S(2)Ab appeared before HBsAb in 57.1% of our patients and was found in some patients before pre-S(1)Ag and HBsAg had cleared (42.8%), thus allowing complete viral clearance and acute HBV infection to be predicted earlier.

A biphasic pattern of anti-pre-S responses in acute hepatitis B virus infection

The clinical relevance of the immune response to the translation products of the pre-S1 and pre-S2 regions of hepatitis B virus was examined by testing sequential serum samples from 17 patients with acute self-limited hepatitis B and from two patients in whom chronic liver disease developed. Anti-pre-S antibodies were determined by enzyme immunoassays based on the inhibition of binding of monoclonal antibodies to epitopes in the pre-S1 and pre-S2 sequence. In acute, self-limited infection, anti-pre-S antibodies appeared in a biphasic pattern. The early antibodies were detected at the time of clinical signs of acute disease when HBsAg and often HBeAg were present, but hepatitis B virus DNA was no longer detectable in serum. Anti-pre-S levels then fell, but subsequently reappeared as the late antibody during the recovery phase, after development of anti-HBe, but before anti-HBs. Anti-pre-S responses were detected in 15 of 17 patients who recovered (88.2%) and in both patients with acute hepatitis B virus infection evolving to chronic liver disease. Although the early antibodies to pre-S1 and pre-S2 proteins appeared at the time of decreasing levels of infectious virus in serum in cases of self-limited infection, these antibodies also were transiently or continuously present with high levels of serum hepatitis B virus DNA in patients in whom chronic hepatitis B infection developed. Thus the anti-pre-S response in acute hepatitis is not a prognostic marker for clinical resolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of concurrence of hepatitis B surface antigen and antibody in a large number of carriers in Okinawa, Japan

A large number of chronic hepatitis B surface antigen (HBsAg) carriers in Okinawa, Japan were tested for antibody to HBsAg (anti-HBs), by both radioimmunoassay and enzyme immunoassay methods. Concurrence of HBsAg and anti-HBs was found in 166 (26.1%). We found no clear predominance of either liver damage or hepatitis B e antigen (HBeAg) in the concurrent carriers studied. Antibody to pre-S2 antigen (anti-pre-S2) was detected in 16 (9.6%) of 166 subjects with concurrent markers, 15 of these 16 carriers were positive for antibody to HBeAg (anti-HBe). Anti-pre-S2 was correlated with anti-HBe rather than with anti-HBs. The distribution of HBsAg subtypes among carriers determined to have subtypes was 76.7% adw, 22.0% adr, 0.2% ayr, 0.9% adwr, and 0.2% adyr. The distribution of anti-HBs subtypes among concurrent carriers was 51.5% anti-r, 21.4% anti-w, 15.5% anti-d, and 10.7% anti-y. Concurrent carriers had HBsAg of one subtype and heterotypic anti-HBs. Because the HBsAg subtype ay is rare in this area, it is hard to believe that the concurrent carriers with anti-y were infected with hepatitis B virus of which the HBsAg subtype was ay. A dual infection was highly unlikely. It seems that some of the concurrent carriers correlate with compound subtypes adwr and adyr.

Changes of pre-S1 and pre-S2 antigens in sera of patients with hepatitis B virus infection

Polypeptides encoded by the pre-S1 and pre-S2 genes of hepatitis B virus (HBV) (pre-S1 antigen and pre-S2 antigen) were detected by enzyme-linked immunosorbent assay (ELISA) in 137 serum samples of patients with HBV infection. The HBV-DNA level closely correlated with the titer of pre-S antigens. However, HBV-DNA levels more closely correlated with the titer of the pre-S1 antigen [HBV-asymptomatic carrier (ASC): n = 40, r = 0.800, P less than 0.01; chronic hepatitis B (CH): n = 60, r = 0.730, P less than 0.01] than with the titer of the pre-S2 antigen [ASC: r = 0.675, P less than 0.01; CH: r = 0.575, P less than 0.01]. Thirty patients with CH, in whom hepatitis e antigen (HBeAg) was cleared after acute exacerbation (AE) [alanine aminotransferase (ALT) level greater than 200 IU/L] and the ALT level normalized, were followed for 12 months and classified into two groups: Group 1, those in whom HBeAg reappeared with an elevated ALT level within 12 months, and Group 2, those in whom HBeAg was persistently cleared from the serum and a normal ALT level continued. Of the 30 patients, 24 (80%) were classified into Group 1 and 6 (20%) were classified into Group 2. Changes in serum levels of HBV markers a month before and after AE were observed. The HBV-DNA level and DNA-P activity became negative after AE in both groups. The titer of pre-S1 antigen also decreased after AE, and no significant differences were observed between Group 1 and Group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Epitope-specific antibody response to the surface antigen of duck hepatitis B virus in infected ducks

In order to investigate the immune response to duck hepatitis B virus (DHBV) infection, newly hatched DHBV DNA negative ducklings were injected with infectious serum of sufficiently low DHBV-DNA titer to allow clearance of viremia. Of 20 injected ducklings, 13 (65%) became viremic. Of these, 6 (46%) cleared virus from the serum 3 to 22 weeks postinjection. The convalescent sera of these 6 animals were tested for an epitope-specific antibody response in a highly specific competitive inhibition assay using a panel of monoclonal antibodies against duck hepatitis B surface antigen (DHBsAg) that had been well-characterized. All 6 animals recovering from DHBV infection developed antibodies to epitopes on the preS and S proteins of DHBV. Antibody responses were highly variable with marked differences between animals in the extent and specificity of the antibody response. The humoral response to DHBsAg was prolonged in some animals but transient in others. No antibody to preS or S was detected in either preimmune sera or sera of control animals from an uninfected flock. Infected animals that did not clear viremia also remained antibody negative. The humoral responses to neutralizing preS epitopes III and V were weak but antibodies to two immunodominant epitopes on the preS region (II and B) were present in all 6 animals. The humoral response to the two epitopes in the S region was transient and of lower titer when compared to the two immunodominant preS epitopes. The two immunodominant preS epitopes may play an important role in clearance of DHBV infection in ducks.

An automatic modified polymerase chain reaction procedure for hepatitis B virus DNA detection

In order to perform an efficient and reproducible diagnostic test for hepatitis B virus (HBV) infection using the polymerase chain reaction (PCR), sixteen primer couples specific for the HBV genome were selected. Primers 15-31 nucleotides in length containing between 31-73% GC permitted amplification of fragments corresponding to the whole HBV genome. The specificity and efficiency of PCR amplification were studied in detail using DNA extracted from either a viral particle preparation or from the liver of a patient with chronic active hepatitis. Three primer couples in the X, C and PreS regions, i.e. MD24/MD26, MD27/MD31 and MD19/MD18, respectively, gave satisfactory results and performed efficiently under highly stringent hybridization conditions. A modified PCR procedure was then developed using only two thermal steps with a temperature shift of 16 degrees C. This simple method was as efficient as conventional PCR and permitted detection of a single HBV DNA molecule with the X region specific primer couple. The automatization of this PCR-based procedure permitted 40 amplification cycles in 105 min.

Changes in serum levels of hepatitis B virus markers after interferon treatment

The effect of interferon (IFN) treatment on serum levels of pre-S antigens [pre-S(1) antigen, pre-S(2) antigen, polymerized human serum albumin receptor (pAR)] which are coded by the pre-S region of hepatitis B virus DNA (HBV-DNA), and HBV-markers was analyzed in 23 patients with chronic hepatitis B. One year after IFN treatment, 4 patients (Group C) became HBeAg negative. Six patients (Group B) transiently became HBeAg-negative, but reverted to HBeAg positive. Thirteen patients (Group A) remained HBeAg positive. All of the patients remained HBsAg-positive. Initiation of IFN treatment was rapidly followed by reduction or loss of DNA-P in the serum whether the patients became HBeAg negative or remained positive, and whether serum transaminase (S-GPT) levels became normal or not after IFN treatment. Group C patients, in whom pre-S antigens decreased rapidly during IFN treatment and disappeared before S-GPT levels normalized, became HBeAg negative one year after IFN treatment. Anti-pAR was detected in three out of these 4 patients. In contrast, Group A and Group B patients, in whom pre-S antigens decreased slowly during IFN treatment and did not disappear in spite of those patients being transiently negative for HBeAg and DNA-P, remained HBeAg positive with elevated S-GPT levels one year after IFN treatment. Anti-pAR was almost undetectable. These results suggest that testing for pre-S antigens is more useful for determining the prognosis of patients with chronic hepatitis B treated with IFN than testing for HBsAg, HBeAg and DNA-P.

Identification of an attachment site for human liver plasma membranes on hepatitis B virus particles

The surface antigen of hepatitis B virus (HBsAg) exposes three protein domains: preS1, preS2, and S. In a previous study we have shown that preS1 sequences expressed in transfected yeast cells bind specifically to plasma membranes of human liver. In this study we show that purified virus particles from a virus carrier bind also specifically to such membranes. Subviral HBsAg filaments which are rich in preS1 bind well too, while HBsAg 20-nm particles which contain small amounts of preS1 bind to a much lesser degree. The binding can be inhibited by a monoclonal antibody which recognizes a sequential epitope between amino acids 27 and 49 of the preS1 domain.

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.

The preS1 antigen of hepatitis B virus is highly immunogenic at the T cell level in man

14 hepatitis B vaccine recipients who showed high titers of anti-hepatitis B surface antibodies in serum after booster immunization with a polyvalent hepatitis B surface antigen vaccine that contained trace amounts of hepatitis B virus (HBV) preS1 and preS2 envelope antigens were studied for their in vitro T cell response to these antigens. All 14 subjects displayed a significant proliferative T cell response to the S/p25 envelope region encoded polypeptide; 8 also responded to preS1, while only 1 showed a significant level of T cell proliferation to preS2. Limiting dilution analysis demonstrated that the frequency of preS-specific T cells in two of these vaccine recipients was higher than that of S/p25-specific T cells. T cell cloning was then performed and a total of 29 HBV envelope antigen-reactive CD4+ cloned lines were generated from two preS-responsive vaccines. 21 of these lines were S/p25 specific, 7 preS1 specific, and 1 preS2 specific. Taken together, all these results suggest that the preS1 antigen may function as a strong T cell immunogen in man.

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.

Human liver plasma membranes contain receptors for the hepatitis B virus pre-S1 region and, via polymerized human serum albumin, for the pre-S2 region

Hepatitis B virus particles contain three related viral envelope proteins, the small, middle, and large S (surface) proteins. All three proteins contain the small S amino acid sequence at their carboxyl terminus. It is not clear which of these S proteins functions as the viral attachment protein, binding to a target cell receptor and initiating infection. In this report, recombinant hepatitis B surface antigen (rHBsAg) particles, which contain only virus envelope proteins, were radioactively labeled, and their attachment to human liver membranes was examined. Only the rHBsAg particles containing the large S protein were capable of directly attaching to liver plasma membranes. The attachment was saturable and could be prevented by competition with unlabeled particles or by a monoclonal antibody specific for the large S protein. In the presence of polymerized human serum albumin, both large and middle S protein-containing rHBsAg particles were capable of attaching to the liver plasma membranes. Small S protein-containing rHBsAg particles were not able to attach even in the presence of polymerized human serum albumin. These results indicate that the large S protein may be the viral attachment protein for hepatocytes, binding directly to liver plasma membranes by its unique amino-terminal (pre-S1) sequence. These results also indicate that polymerized human serum albumin or a similar molecule could act as an intermediate receptor, attaching to liver plasma membranes and to the amino acid sequence (pre-S2) shared by the middle and large S proteins but not contained in the small S protein.

In vitro immune responses to hepatitis B surface antigen (Pre-S2 and S) following remote infection by hepatitis B virus in humans

In this report we evaluate the human immune response to hepatitis B surface antigen (HBsAg) following remote infection with hepatitis B virus (HBV). HBsAg-reactive lymphocytes can be readily demonstrated in the peripheral blood of individuals with established immunity following infection with HBV. In vitro stimulation with small doses of plasma-derived HBsAg, yeast-derived HBsAg (S region) or pre-S2 peptide will induce specific IgG to HBsAg (anti-HBs) in the absence of a polyclonal increase in total IgG. The pre-S2 peptide will stimulate, in a T cell-dependent fashion, the in vitro production of anti-HBs with specificity for the S domain. This anti-HBs production is mediated by pre-S2-stimulated soluble T-cell factors. Peripheral blood mononuclear cells from individuals with established immunity proliferate to the yeast-derived HBsAg but not to the plasma-derived HBsAg or pre-S2 peptide. The chronic HBsAg carriers do not produce anti-HBs following stimulation with HBsAg regardless of the source or component of antigen used. Different study protocols failed to demonstrate HBsAg-specific responses in the peripheral blood mononuclear cells of chronic carriers.

A non-radioactive diagnostic test for the detection of HBV DNA sequences in serum at the single molecule level

A non-radioactive diagnostic test, using an acetylaminofluorene-labelled DNA probe, was developed to detect HBV DNA sequences in serum. In vitro enzymatic amplification was employed to increase the amount of HBV DNA sequences, and an amplification rate up to 1.5 x 10(7) was observed. When a dot-blot was performed after amplification with the Klenow fragment for 32 cycles, the detection limit was 3-30 particles. Sera from 20 blood donors and 10 HBs-Ag carriers were screened simultaneously, with the non-radioactive test performed after 28 amplification cycles, and with the classical radioactive test without amplification. An acceptable correlation was obtained between these two techniques. In Southern blot analysis of samples amplified with the thermoresistant DNA polymerase (Taq polymerase) for 40 cycles, a single DNA molecule was detected. Thermal treatment at 115 degrees C efficiently disrupted purified viral particles and allowed the detection of a single viral particle. Applied to crude serum, a kinetic study showed that this treatment was optimal after an incubation time of up to 10 min. Under these conditions, the detection limit was approximately 2 x 10(5) viral particles, after 40 amplification cycles performed with the Taq polymerase.

Long-term immune reactivity to pre-S(2)-antigen after acute hepatitis B infection

We investigated sera from 39 patients, taken 1-8 years after recovery from acute hepatitis B for anti-pre-S(2) by Western blotting and for anti-HBs by radioimmunoassay. Anti-pre-S(2) antibodies were found in 27 out of 39 sera (69%) with the highest frequency in sera with anti-HBs greater than 100 IU/I (92%). However, sometimes sera with low anti-HBs titres showed a strong response in Western blotting. Acute hepatitis sera were also investigated from a limited number of patients (n = 14). Anti-pre-S(2) antibodies were found during antigenaemia (four out of six patients) and within 3 months after the maximum of alanine amino transferase (ALAT) (seven out of ten patients). Anti-pre-S(2) is an early antibody. It remains in the circulation for many years similar to but independent of anti-HBs.

Treatment of acute and chronic viral hepatitis

Over the 12 years since the first introduction of interferon for the treatment of chronic hepatitis B, progress has apparently been slow. Nevertheless, it now appears that at least one third of chronic hepatitis virus carriers, particularly those with more severe disease, and a similar, perhaps greater, proportion of those with chronic parenteral non-A, non-B hepatitis, can be successfully treated with alpha-interferon. In the not too distant future, controlled trials of alpha-interferons in these situations will be complete and they will be a yardstick by which other future therapies can be judged. Already a number of trials are in progress to determine which agents might, in addition to interferon, augment the response rates. The situation clinically is analogous to that for tuberculosis in the 1950s and for cancer chemotherapy only a decade or so ago. The prospects of prevention of the progression to cirrhosis, and perhaps in the long term reduction in the incidence of hepatocellular carcinoma, are exciting, and with the introduction of a number of new cytokines available through recombinant technology, each with novel antiviral activities, the future prospects are exciting indeed.

Anti-pre-S antibodies in different groups of patients with hepatitis B virus infection

The anti-pre-S antibody in the samples of sera from normal healthy persons and patients with different clinical types of liver diseases due to hepatitis B virus (HBV) infection was detected by a newly established enzyme-linked immunosorbent assay technique. This test is a blocking assay where anti-pre-S antibody in the patient's serum blocks subsequent addition of horse radish peroxidase-labelled polymerized human serum albumin (pHSA) to the pHSA-receptor site of HBsAg molecules fixed on a solid surface. Anti-pre-S activity was not detected in any from 95 healthy persons who were negative for all HBV-markers or from 105 healthy HBV carriers. In 12 sera from HBV vaccine recipients, anti-pre-S activity was noted in higher proportions compared with anti-HBs, after both the second and third doses of vaccine. Anti-pre-S activity was detected in small proportions of HBsAg positive sera from acute viral hepatitis (4.2%) and chronic active hepatitis (10%). In subacute viral hepatitis patients, the anti-pre-S antibody was totally absent. However, anti-pre-S activity was recorded in high proportions of HBsAg-positive sera from patients with cirrhosis of liver (57.2%) and fulminant hepatitis (41.6%). The anti-pre-S antibodies were assumed to be implicated in the clearance of HBV particles from circulation without causing tissue damage.

Antibodies to translation products of the pre-S1 and pre-S2 regions of the envelope gene of hepatitis B virus in fulminant hepatitis B

Sera from 11 patients with fulminant hepatitis B were tested for antibodies to translation products of the pre-S1 and pre-S2 regions of hepatitis B virus of IgM, IgA and IgG classes, as well as of IgA1, IgA2 and SIgA, with solid-phase enzyme immunoassays using native viral polypeptides. Antibodies to pre-S1 region product of IgM and/or IgA class were detected invariably in six patients who still had detectable hepatitis B surface antigen in serum at the time of clinical presentation. The remaining five patients who had lost HBsAg at presentation had antibodies to pre-S region products of various immunoglobulin classes in higher titers. The five patients with fulminant hepatitis without HBsAg had higher levels of IgA antibodies to pre-S region products than the seven patients with nonfulminant acute hepatitis B who had lost HBsAg: IgA antibody to pre-S1 region product (75.6 +/- 63.8 vs. 2.9 +/- 3.2, p less than 0.01) and IgA antibody to pre-S2 region product (28.9 +/- 25.3 vs. 4.2 +/- 6.9, p less than 0.01). IgA antibodies to pre-S1 and pre-S2 region products were invariably polymeric in fulminant hepatitis B. These findings are compatible with the hypothesis that a heightened humoral antibody response to pre-S1 and pre-S2 region products occurs early during the course of fulminant hepatitis B, participating in severe hepatic injury and early clearance of virus characteristic of this disease.

Anti-pre-S2 antibodies in natural hepatitis B virus infection and after immunization

Anti-pre-S2 antibodies were detected by enzyme-linked immuno-absorbant assay using a synthetic peptide analogue of pre-S2 protein, in different groups of hepatitis-B-infected subjects, including patients presenting with cirrhosis and liver cancer, and also in infants immunized with hepatitis B vaccine. Anti-pre-S2 antibodies were not detected in hepatitis B surface antigen (HBsAg) chronic carriers, including patients with cirrhosis or primary liver cancer. Anti-pre-S2 antibodies were not detected in HBsAg-positive sera during the early phase of acute hepatitis. They were only noted upon recovery, when anti-HBs antibodies are detectable at the same time as HBsAg. After recovery, anti-pre-S2 antibodies were noted in 57% of test sera and were still detectable in 16% of anti-HBs-positive sera obtained years after HBV infection. Anti-pre-S2 antibodies were detected in 70% of infants immunized with 2 or 5 micrograms doses of Hevac B Pasteur vaccine, confirming that this vaccine contains pre-S2 antigen. Anti-pre-S2 detection was correlated with the anti-HBs antibody titre.

Detection of hepatitis B virus sequences in serum by using in vitro enzymatic amplification

In vitro enzymatic amplification was applied to detect hepatitis B virus (HBV) DNA sequences in serum. This technique, known as the polymerase chain reaction (PCR) was used to amplify a 128 bp DNA fragment including a 112 nucleotide long sequence complementary to a region in the S gene of the HBV genome. Amplified samples were subjected to spot-test hybridization and scintillation counting using a 32P-labeled oligonucleotide probe. A kinetic study, performed for 4 to 32 PCR cycles with a viral particle preparation, showed a time-limited exponential accumulation of the specific amplified DNA fragment. Amplification yield after 32 cycles was at least 4 X 10(6) with a detection limit equal to 3 X 10(2) viral particles per ml of serum. As the reliability of the PCR technique was greatest for 24 PCR cycles, these conditions were used to develop a quantitative test with a detection limit of 4 X 10(4) viral particles per ml of serum. Results of this test were perfectly correlated with those obtained from the classical spot test without amplification. Ethidium bromide stained agarose gel and Southern blot analysis confirmed the specific amplification of the 128 bp HBV DNA fragment.

Antibody response to pre-S2 and hepatitis B virus induced liver damage

Antibodies to the pre-S2 encoded sequence of the hepatitis B virus (HBV) envelope were detected in 83% of patients recovering from acute hepatitis B. Such antibodies were absent in cases showing chronic evolution and were found in less than 10% of chronic hepatitis B cases, with no relation to liver disease activity. In acute infection anti-pre-S2 became detectable when maximum liver damage had already occurred and was still detectable in 30% of the cases tested 5-7 years after recovery, as well as in 40% of healthy individuals with naturally acquired immunity to HBV. 10 out of 20 recipients of a plasma-derived, pre-S2-containing, HB vaccine acquired anti-pre-S2 and had no evidence of concurrent liver damage or of autoimmune reactions to human albumin or of suppression of the anti-HBs response. These findings indicate that the antibody response to pre-S2 is a marker of HBV clearance and has no role in the pathogenesis of HBV-related liver damage.