Enhanced immunogenicity of the pre-S region of hepatitis B surface antigen

Detection of antibodies against pre-S1 proteins in sera of patients with hepatitis B virus (HBV) infection

Pre-S1 (large S) proteins are components of the envelope of HBV. The presence of pre-S1 proteins is correlated with viral replication. To test sera of patients with HBV infection for the presence of antibodies against pre-S1 proteins (anti-pre-S1), an E. coli extract containing a pre-S fusion protein covering the greater part of the pre-S1 region was subjected to Western blotting and probed with sera of patients. Anti-pre-S1 was present in the sera of all 4 patients with acute self-limited HBV infection and in the sera of 3 patients with a fulminant course. The antibodies could not be detected in the sera of 6 patients with acute HBV infection entering chronicity, in the sera from 10 HBsAg carriers or in the sera of 25 patients with chronic liver disease, positive for HBsAg and antibodies to hepatitis Delta virus. In an additional study, anti-pre-S1 could not be found in 11 sera from 12 patients with previous HBV infection, positive for anti-HBs and anti-HBc. Antibodies to pre-S1 proteins appear at the early stage of acute resolving HBV infection and seem to play a role in the elimination of the virus. The antibodies are absent in the sera of patients with acute HBV infection entering a chronic course and in the sera of chronic HBsAg-carriers.

T-cell recognition of pre-S regions of HBsAg can bypass nonresponse to the S region

The objective of the studies reported herein was to identify and characterize T cell and B cell recognition sites within the pre-S regions of HBsAg/p39, and to analyze functional T-cell-B cell interactions at the level of in vivo antibody production. The results indicate: (1) several peptides within the pre-S(1) region of HBsAg were identified which can induce and elicit HBsAg/p39-specific T-cell proliferation; (2) a 10 amino acid peptide, p12-21, and the 94-117 sequence define pre-S(1)-specific T-cell recognition sites; (3) five distinct, pre-S(1)-specific antibody binding sites and 2 pre-S(2)-specific antibody binding sites were identified; (4) synthetic pre-S(1) region T-cell determinants can prime in vivo antibody production to multiple B-cell epitopes within the pre-S(2) and S regions, as well as within the pre-S(1) region; and (5) specificity of the primed T cell population can influence the specificity of the B-cell response.

Synthesis in yeast of hepatitis B virus surface antigen modified P31 particles by gene modification

The pre-S2 portion of hepatitis B virus surface antigen P31 gene was modified to make gene products resistant to trypsin-like proteases in Saccharomyces cerevisiae. The coding sequence for 6 amino acids (Ser44 - Thr49) including Arg48 was removed, and the altered gene was inserted into an expression vector. The modified HBsAg P31 (M-P31c) gene products, consisting of GP37 and GP34, formed particles having both HBsAg antigenicity and polymerized-albumin receptor activity. Since the M-P31c particles can elicite two kinds of protective antibodies against hepatitis B virus, anti-S and anti-pre-S2 antibodies, the M-P31c particles are expected to be potentially effective to S-nonresponders.

A solid-phase enzyme immunoassay for the determination of IgM and IgG antibodies against translation products of pre-S1 and pre-S2 regions of hepatitis B virus

The envelope of hepatitis B virus is coded for by pre-S1, pre-S2 regions and the S gene. A method was developed to determine antibody to the product of pre-S1 region (anti-pre-S1) and antibody to the product of pre-S2 region (anti-pre-S2), either of IgM or IgG class, by a solid-phase enzyme immunoassay. For the determination of anti-pre-S1, tubular particles containing translation products of pre-S1, pre-S2 regions and the S gene were broken into constituent envelope polypeptides and immobilized on a solid support. Serums were absorbed with spherical particles containing translation products of pre-S2 region and the S gene, obtained from plasma positive for hepatitis B e antigen (HBeAg) and deprived of particles carrying pre-S1 product by an affinity column. They were then tested for the binding with tubular polypeptides fixed on a solid support, and the bound antibody representing anti-pre-S1 was detected by monoclonal antibody to human IgM/mu or IgG/gamma labeled with horseradish peroxidase. For the determination of anti-pre-S2, test serums were absorbed with spherical particles containing the product of the S gene, obtained from plasma positive for antibody to HBeAg and deprived of particles bearing pre-S2 product by an affinity column. They were then tested for the binding with polypeptides, fixed on a solid support, composed of products of pre-S2 region and the S gene. The assay was applied to the determination of anti-pre-S1 and anti-pre-S2 of IgM or IgG class in asymptomatic carriers and in persons who had recovered from infection with hepatitis B virus.

Expression of hepatitis B virus large envelope polypeptide inhibits hepatitis B surface antigen secretion in transgenic mice

The outer membrane of the hepatitis B virus consists of host lipid and the hepatitis B virus major (p25, gp28), middle (gp33, gp36), and large (p39, gp42) envelope polypeptides. These polypeptides are encoded by a large open reading frame that contains three in-phase translation start codons and a shared termination signal. The influence of the large envelope polypeptide on the secretion of hepatitis B surface antigen (HBsAg) subviral particles in transgenic mice was examined. The major polypeptide is the dominant structural component of the HBsAg particles, which are readily secreted into the blood. A relative increase in production of the large envelope polypeptide compared with that of the major envelope polypeptide led to profound reduction of the HBsAg concentration in serum as a result of accumulation of both envelope polypeptides in a relatively insoluble compartment within the cell. We conclude that inhibition of HBsAg secretion is related to a hitherto unknown property of the pre-S-containing domain of the large envelope polypeptide.

Assembly of viral particles in Xenopus oocytes: pre-surface-antigens regulate secretion of the hepatitis B viral surface envelope particle

Infection with hepatitis B virus (HBV) is associated with the production of a viral envelope particle that contains membrane lipids, surface antigen (S), and two presurface-antigens (pre-S) comprised of the entire S moiety with approximately 55 (pre-S2) and 174 (pre-S1) additional NH2-terminal amino acids. We show here that Xenopus oocytes injected with synthetic S mRNA assemble and secrete characteristic 22-nm viral envelope particles. In contrast, pre-S1 and pre-S2 antigens are synthesized but not secreted. By coinjecting mRNAs, we found that synthesis of high levels of pre-S proteins specifically inhibits S antigen secretion. On the other hand, high levels of S synthesis can drive the secretion of small amounts of either pre-S antigen. These observations are consistent with a model for viral envelope assembly in which both S and pre-S proteins are incorporated into a multimeric particle, presumably via interactions between the S protein domains, while the pre-S amino-terminal moieties regulate the secretion of this structure. Our results indicate that Xenopus oocytes will provide a powerful system for studying the morphogenesis of simple structures of viral or cellular origin.

A synthetic peptide vaccine involving the product of the pre-S(2) region of hepatitis B virus DNA: protective efficacy in chimpanzees

The S gene encoding the major surface polypeptide of hepatitis B virus is preceded by the region pre-S(2) with a capacity to code for 55 amino acid residues. In the product of region pre-S(2), the sequence of 19 amino acid residues (amino acids 14-32 from the N terminus) representing an area of high local hydrophilicity is shared by viral strains of subtypes adr, ayw, and ayr; residue 22, phenylalanine, is replaced by leucine in a strain of the other subtype, adw. A synthetic peptide vaccine involving these 19 amino acid residues, when given to two chimpanzees, raised antibodies that bound to viral particles and protected the animals from challenge with 10(6) chimpanzee infectious doses of hepatitis B virus.

Hepatitis B virus large surface protein is not secreted but is immunogenic when selectively expressed by recombinant vaccinia virus

The envelope region of the hepatitis B virus (HBV) genome contains an open reading frame that begins upstream of the major surface protein gene. The two minor proteins that are initiated within this pre-s segment are immunogenic and may be involved in virus attachment to hepatocytes. We have constructed a recombinant vaccinia virus that contains the predicted coding segment for the large surface protein (LS) under control of a vaccinia virus that contains the predicted coding segment for the large surface protein (LS) under control of a vaccinia virus promoter. Cells infected with the recombinant virus synthesized HBV polypeptides of 39 and 42 kilodaltons, corresponding to the unglycosylated and glycosylated forms of LS, respectively. The presence of pre-s epitopes in the 39- and 42-kilodalton polypeptides was demonstrated by binding of antibody prepared against a synthetic peptide. Synthesis of the 42-kilodalton species was specifically inhibited by tunicamycin, suggesting that it is N-glycosylated. Despite apparent glycosylation, LS was not secreted into the medium of infected cells. Nevertheless, rabbits vaccinated with the purified recombinant virus made antibodies that recognized s and pre-s epitopes. Antibody to the NH2 terminus of LS appeared before or simultaneously with antibody that bound to the major surface protein. The additional immunogenicity provided by expression of LS may be advantageous for the development of an HBV vaccine.

Absence of pre-S2 antibodies in natural hepatitis B virus infection

Antibodies to the host "self" component human serum albumin (HSA) and to its receptor are induced by the pre-S2 encoded aminoacid sequence (120-145) of the middle surface protein on the hepatitis B virus (HBV) particle and are produced as part of the immune response during acute HBV-infection. The antibodies disappeared rapidly during the convalescence phase and were not detectable in patients with naturally acquired immunity to HB. These data raise questions about the importance of anti-pre-S2 antibodies for long-term protection against HBV-infection. The coexistence of HBV-DNA with antibodies to native HSA (nHSA) in 13/16 patients with biopsy proven liver disease and of HBV-DNA with anti-pre-S2 in 10/13 patients argues against the attribution of virus eliminating properties to antibodies directed against pre-S2 determinants. In fact circulating anti-nHSA and anti-pre-S2 persisted in 16/17 and 13/17 patients, respectively, with major HBV-induced liver disease but not in symptomless HBsAg carriers. This finding suggests that continuous production of antibodies against the "self" component HSA and/or its receptor structures are associated with the pathogenesis of chronic HBV-induced liver disease. Pre-S2 coded peptide sequences should thus not be incorporated into HB vaccines.

Monoclonal antibody recognizing pre-S(2) epitope of hepatitis B virus: characterization of pre-S(2) epitope and anti-pre-S(2) antibody

A hybrid cell line producing monoclonal antibodies recognizing an epitope encoded by the pre-(S)2 region of hepatitis B virus (HBV) genome was obtained by fusion of mouse myeloma cells with lymphocytes from mice immunized with HBV. The monoclonal antibody Mo-F124 secreted from the hybrid line reacted with the pre-S(2) epitope expressed on the surface of both viral and recombinant HBsAg particles--pre-S(2) and S gene product--localised on 34 kD glycoprotein of the viral envelope. The pre-S(2) epitope was sensitive to digestion with V8 protease from Staphylococcus aureus. The enzyme abolished reactivity with Mo-F124 and polymerized human serum albumin (pHSA) binding activity of recombinant particles. Mo-F124 antibody was used to develop highly sensitive radioimmunoassays for determination of pre-S(2) epitope and anti-pre-S(2) antibody in sera of hepatitis B patients. Detection of a pre-S(2) epitope by the monoclonal antibody-based assay in the early phase of acute HBV infection correlated well with the presence of markers of active viral replication (HBeAg, HBV DNA). The appearance of anti-pre-S(2) antibody, usually in the third month after onset of symptoms, was followed by elimination of circulating HBsAg and seroconversion to anti-HBs in all tested cases of uncomplicated acute hepatitis followed by recovery. Anti-pre-S(2) response was not observed in patients with chronic hepatitis B or acute HBV infection progressing to chronic disease. The observed correlation of anti-pre-S(2) response with recovery suggests that the pre-S(2) epitope may represent one of the epitopes inducing antibodies that neutralize the hepatitis B virus.

Antibodies to pre-S and X determinants arise during natural infection with ground squirrel hepatitis virus

The DNA sequence of the ground squirrel hepatitis virus (GSHV) genome predicts the existence of several proteins in addition to the major surface (S) and core antigens. These include the pre-S1 and pre-S2 proteins, initiated at sites within the open reading frame preceding and continuous with the coding region for the S gene product, and the X protein, the putative product of an independent reading frame. Using an antibody directed against a peptide predicted by codons 130 to 143 of the pre-S1 reading frame, we identified a 43-kilodalton product of the pre-S1 coding region in preparations of GSHV surface antigen purified from the sera of infected animals. In addition, by immunoprecipitation of S- and pre-S-specific in vitro translation products with ground squirrel sera obtained after GSHV infection, we determined that antibodies arise to both S and pre-S determinants. The antibody response to pre-S includes, in some cases, reactivity to pre-S1-specific domains and is not always associated with an anti-S response. Similarly, by production of the viral X gene product in vitro followed by immunoprecipitation with ground squirrel sera, we showed that antibodies to this viral gene product also arise during infection, indicating that X antigenic determinants are synthesized during viral infection and are recognized by the host immune system.

Viral hepatitis

Developments over the last four years in our understanding of viral hepatitis are analyzed. The molecular structure of hepatitis A has been established, and vaccines for prevention are under development. The recognition of the replicative and integrated stages of hepatitis B infection has allowed more rational approaches to therapy. Vaccines are of proven value. Delta virus infection has assumed an important role world wide as a cause of serious and fulminant liver disease in hepatitis B carriers. The agents for non-A, non-B virus hepatitis have eluded identification. These are important causes of chronic liver disease particularly in recipients of blood transfusion.

Characterization of monoclonal antibodies specific for the pre-S2 region of the hepatitis B virus envelope protein

Monoclonal antibodies (McAb) specific for the pre-S region of the hepatitis B virus (HBV) envelope protein were prepared using HBV particles of hepatitis B surface antigens (HBsAg) as immunogens. The antibodies reacted in Western blot analyses and in ELISA with pre-S2 sequences of the HBV envelope protein. Pepsin or protease V8 treatment of the antigen abolished reactivity. The fine specificity of one of the McAb (F376) was established by immunoassays using synthetic peptides and a pre-S2-beta-galactosidase fusion protein expressed in E. coli. The shortest peptide recognized by F376 is demarcated by residues pre-S(132) at the N-terminal and pre-S(140)-pre-S(145) at the C-terminal. The corresponding amino acid sequence (for HBV subtype adw2) is: QDPRVRGLY(LPAGG). Additional amino acid residues at the N-terminal, and possibly at the C-terminal ends contribute to the binding of McAb, probably due to conformational influences. The McAb was applied to immunoassays of pre-S2 sequences in purified HBsAg and in human sera containing HBsAg.

Nonoverlapping T and B cell determinants on an hepatitis B surface antigen pre-S(2) region synthetic peptide

We have examined T cell recognition of a hepatitis B surface antigen (HBsAg), pre-S(2)-region synthetic peptide, p120-145, in terms of fine specificity, H-2-linked genetic influences, comparison to antibody binding, and relevance to T cell recognition of the native protein. We showed that the immune response to the synthetic peptide is regulated by H-2-linked genes, but that the pattern of H-2 restriction differed from that observed for the native anti-pre-S(2) response. Dominant and nonoverlapping T cell and B cell recognition sites were identified on the synthetic peptide p120-145. T cell recognition is focussed on the NH2-terminal sequence, and antibody (B cell) recognition is focussed on the COOH-terminal sequence. The fine specificity of T cell recognition of p120-145 was defined by a single, subtype-dependent amino acid substitution. With respect to the immunogenicity of p120-145, the synthetic peptide containing both T and B cell determinants is highly immunogenic in responder strains, whereas separate T or B cell peptide determinants are minimally immunogenic. Furthermore, the synthetic T cell recognition site can prime T cell help for antibody production to the synthetic B cell site, which is crossreactive with the native pre-S(2) region of HBsAg/p33 particles. This system provides evidence that totally synthetic T cell and B cell recognition sites can be combined to yield a functional immunogen.

A poliovirus neutralization epitope expressed on hybrid hepatitis B surface antigen particles

The hepatitis B virus (HBV) envelope protein carrying the surface antigen (HBsAg) is assembled with cellular lipids in mammalian cells into empty viral envelopes. In a study to evaluate the capacity of such particles to present foreign peptide sequences in a biologically active form, in-phase insertions were created in the S gene encoding the major envelope protein. One of the sequences inserted was a synthetic DNA fragment encoding a poliovirus neutralization epitope. Mammalian cells expressing the modified gene secreted hybrid particles closely resembling authentic 22-nanometer HBsAg particles. These particles reacted with a poliovirus-specific monoclonal antibody and induced neutralizing antibodies against poliovirus. The results indicate that empty viral envelopes of HBV may provide a means for the presentation of peptide sequences and for their export from mammalian cells.

Expression of hepatitis B virus surface antigen P31 gene in yeast

The hepatitis B virus surface antigen (HBsAg) P31 gene has been expressed in yeast Saccharomyces cerevisiae. The gene products were shown to be glycoproteins with molecular sizes of 37,000 and 34,000 daltons (GP37 and GP34) containing polymerized albumin receptors. Successfully detecting these proteins depended on the extraction procedures. In the extract without protein denaturants and inhibitors, these products were degraded rapidly by proteases to yield smaller size derivatives lacking polymerized albumin receptors. As is the case in human serum-derived HBsAg, yeast HBsAg consisting of GP37 and GP34 was found to be particles or aggregates having a buoyant density of 1.2 g/cc; these particles bound to polymerized human serum albumin in species-specific manner.

Novel hepatitis B vaccines

Development of vaccines against hepatitis B has proceeded along four main lines. Human plasma-derived vaccines are safe, effective, and in general use. Subunit polypeptide vaccines formulated in micelles have reached the stage of clinical trials. Recombinant DNA vaccines have been produced in prokaryotic and eukaryotic cells, notably in yeast. The yeast-derived recombinant vaccine has proved safe and effective in extensive clinical trials, eliciting antibodies of equal quantity and quality of specificity to those elicited by plasma-derived vaccine. DNA recombination has also been applied to the development of hybrid vaccinia virus vaccines which are capable of immunological 'priming'. Finally, chemical synthesis has succeeded in producing small peptides which include specific epitopes eliciting antibody responses in experimental animals. This last approach offers a prospect of ultimately producing multivalent synthetic vaccines against several microbial agents.

Immunogenicity of a reduced dose of recombinant hepatitis B vaccine

We report a trial of a reduced dose (2.5 micrograms) of recombinant hepatitis B vaccine, carried out over seven months in 54 males aged 17 to 19 years. Response to the reduced dose was significantly inferior to that found in equivalent trials of 5 and 10 micrograms doses. Although all seroconverted, three participants (6%) remained below the protective level of 10 IU l-1 of antibody to hepatitis B surface antigen (anti-HBs) and a further eight (15%) below 100 IU l-1, possibly requiring early revaccination. The final geometric mean titre of anti-HBs was 810 IU l-1 (95% confidence interval, 433 to 1520). It appears that 2.5 micrograms may be too low a dosage for general use in adults.

Immunochemical structure of the hepatitis B surface antigen vaccine--II. Analysis of antibody responses in human sera against the envelope proteins

Antibody responses to the three envelope (env) proteins of hepatitis B viral particles (HB-VP): the S-encoded P25 polypeptide; the pre-S(2)- and S-encoded GP33/GP36 polypeptide; and the large entire env gene (pre-S + S) product, P39/GP42, were investigated using a Western immunoblotting assay (WIBA). HB-VP proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to nitrocellulose by electroblotting were used as antigenic probes to determine the polypeptide specificity of these antibodies present in immune individuals. Antisera from human subjects either after a natural HBV infection or after active immunization with the hepatitis B vaccine licensed in France were selected on the basis of a positive serological RIA test for antibodies against hepatitis B surface antigen (HBsAg). In all studied cases, the lack of reactivity of the anti-HBs/P25 antibodies in blots from reduced SDS gels confirms that the S-related-determinants have a conformation sensitive to denaturing agents. In contrast, the anti-pre-S(2)/GP33-GP36 antibodies and the anti-pre-S(1)/P39-GP42 antibodies can be easily detected in WIBA, providing these antibodies recognize the disulfide-bond independent pre-S determinants on the denatured env proteins. However, antisera raised in guinea-pigs against individual HBsAg polypeptides contain antibodies reacting with denatured S-proteins, suggesting that the sequential S-determinants are lost during HBV morphogenesis. Antibody responses in HBV convalescing patients or vaccinated healthy donors are shown to be characterized by: an early transient polypeptide specific-antibody response to pre-S(2)-sequences (detected in WIBA); a persistent antibody response to conformation-dependent S-determinants (detected in RIA). This implies that effective long-term protection against HBV infection requires antibodies directed to native env proteins.

Pre-S1 antigens and antibodies early in the course of acute hepatitis B virus infection

The presence of the two "large" surface proteins of hepatitis B virus (HBV), P39 and GP42 of pre-S1-hepatitis B surface antigen, was assayed in the serum of an experimentally infected chimpanzee by using antibodies to a pre-S1-specific fusion protein synthesized in Escherichia coli. The immune response to pre-S1-hepatitis B surface antigen was monitored by using the pre-S1 fusion protein as an antigen. pre-S1 proteins were detected in the serum early in the course of infection and prevailed as long as hepatitis B surface antigen did, together with hepatitis B e antigen and viral DNA. Thus, the pre-S1 antigen can be considered a novel diagnostic marker for acute HBV infection. Antibodies to pre-S1, both immunoglobulin M and G classes, were also detected early in infection, shortly after the appearance of the pre-S1 antigen, suggesting its strong immunogenicity in vivo. The anti-pre-S1 antibodies therefore also represent an early serological marker for acute HBV infection and, owing to their early appearance and persistence, may play a role in the neutralization of the virus.

Antibody to the receptor for polymerized human serum albumin in acute and persistent infection with hepatitis B virus

The antibody against the receptor for polymerized human serum albumin was determined by radioimmunoassay. The method involved the inhibition by the test serum, absorbed with HBsAg particles without the receptor, on the binding of polymerized human serum albumin to HBsAg particles with the receptor fixed on a solid support. The amount of polymerized human serum albumin captured by the receptor on HBsAg was then determined by the radiolabeled monoclonal antibody directed to an epitope specific for polymerized human serum albumin. In acute infection, the antibody to the receptor for polymerized human serum albumin appeared in the early recovery phase while HBs antigenemia and elevated transaminase levels were still present, preceding the antibody to HBsAg (anti-HBs). The antibody was detected in 4 (1%) of 358 sera from asymptomatic carriers of HBsAg containing antibody to HBeAg, and in none of 67 sera containing HBeAg. Although the antibody was found in as many as 111 (74%) of 150 sera from blood donors who had presumably acquired anti-HBs after natural infection, it was not detected in any sera from 77 recipients of hepatitis B vaccine who had seroconverted for anti-HBs. On the basis of these observations, the determination of antibody to the receptor for polymerized human serum albumin helps in further understanding the immunity to hepatitis B virus.

Antibodies to a synthetic peptide from the preS 120-145 region of the hepatitis B virus envelope are virus neutralizing

Studies with synthetic peptides have provided evidence for the presence of preS coded sequences in the envelope (env) proteins of hepatitis B virus (HBV) and indicated that these sequences are involved in the specific attachment of HBV to liver cells. Scanning of the preS sequence for immunodominant continuous epitopes identifies the sequence within residues preS (120-145) as the most immunogenic in eliciting antibodies recognizing HBV and as the most efficiently binding antibodies from sera of rabbits and humans immunized with HBV env proteins. To assess the potential of preS (120-145) as a synthetic vaccine against hepatitis B, in vitro neutralization of the virus by rabbit antiserum to the peptide was assayed in chimpanzees. The animals, subsequently proven to be susceptible to HBV infection, did not develop hepatitis B as judged by negative serological tests for HBV-associated antigens and antibodies and by normal serum alanine aminotransferase levels and normal liver biopsies. These results establish the role of preS domains in the process of virus neutralization and the potential of synthetic preS analogues for hepatitis B vaccination.

Detection of pre-S1 proteins in serum and liver of HBsAg-positive patients: a new marker for hepatitis B virus infection

The presence of pre-S1 proteins in serum and liver of individuals with acute and chronic hepatitis B virus infection was investigated in Western blots using antibodies against a fusion protein, containing amino acids 20-120 of the pre-S region. Pre-S1 proteins were present in 20 of 38 HBsAg-positive sera. All sera positive for pre-S1 proteins were also positive for hepatitis B virus DNA indicating the presence of hepatitis B virions, and 16 of these sera were also positive for HBeAg. In five sera positive for hepatitis B virus DNA, pre-S1 proteins were not found. In an additional study, pre-S1 proteins could be detected in 4 of 6 patients with acute hepatitis B virus infection during the first 2 weeks after admission to the hospital. The presence of pre-S1 proteins showed a good correlation with the detection of hepatitis B virus DNA. After seroconversion from HBeAg to anti-HBe, both hepatitis B virus DNA and pre-S1 proteins were no longer detectable. Pre-S1 proteins were present in three liver tissue specimens from two patients with acute hepatitis B virus infection and from one patient with cirrhosis of the liver. The proteins were not found in the liver of two HBsAg-positive patients with hepatocellular carcinoma (primary liver carcinoma), negative for HBeAg. Pre-S1 proteins can be detected in serum, positive for hepatitis B virus DNA and in liver tissue of hepatitis B virus-infected individuals. The presence of these proteins appears to correspond with the presence of hepatitis B virus DNA, both markers indicating hepatitis B virus replication.

Characterization of large surface proteins of hepatitis B virus by antibodies to preS-S encoded amino acids

The major surface protein of HBV, the 226-amino-acid HBsAg, is encoded in the 3' proximal segment of the preS-S gene of 389 codons. To identify gene products from the 5' proximal preS sequence, DNA fragments from the preS region were expressed in Escherichia coli as fusion proteins. Antisera prepared against these fusions were used to screen serum proteins of HBV-infected individuals, and found to react specifically with the two large HBV surface proteins of 39 and 42 kDa. The presence of these proteins could be correlated with acute HBV infection. Analysis by Western blotting using the preS sequence-specific antisera and HBV particles separated into spheres, filaments, and Dane particles confirmed that these proteins were associated with the native virus. Dane particles containing active DNA polymerase could be immune precipitated by the preS-specific antibodies, showing that the preS-coded part of these surface proteins is located on the surface of the virion.

Clonal analysis of intrahepatic T lymphocytes in chronic active hepatitis. Isolation of a T-cell line specific for hepatitis B core antigen from a patient with serological evidence of exposure to HBV

We have evaluated whether peripheral blood and hepatic lymphocytes from a patient with chronic active hepatitis (CAH) and antibodies to HBV in serum were specifically sensitized to HBV envelope antigens (HBsAg and pre-S Ag) or to HBcAg. No proliferation to HBV antigens was demonstrated upon stimulation of peripheral blood mononuclear cells either unfractionated or enriched in CD4+ (helper/inducer) T cells. Of 15 T-cell cloned lines (7 CD8+ and 8 CD4+) obtained by limiting dilution in the presence of PHA and recombinant IL2 from liver-infiltrating lymphocytes, one, designated H2, showed specific sensitization to HBcAg, whereas none demonstrated sensitization to viral envelope antigens. The H2 line displayed the CD8+ phenotype, suppressor activity on polyclonal immunoglobulin production and IL2-dependent, HBcAg-specific proliferation. These results suggest that in patients with CAH and serological evidence of previous exposure to HBV, it is possible to obtain lymphocytes specifically sensitized to HBcAg from liver biopsy.

Expression of the hepatitis B virus large envelope protein in Saccharomyces cerevisiae

The yeast vector pPV2 has been constructed for inducible expression of non-fused proteins from the PHO5 promoter. Signals of the URA3 gene are used for transcription termination. The 226-amino-acid 'major' and the 389-amino-acid 'large' envelope protein of hepatitis B virus (HBV) have been produced in Saccharomyces cerevisiae following insertion of the S gene or of the entire pre-S region and the S gene, respectively, of HBV into pPV2. Although normally only a minor constituent of the viral envelope, the 'large' protein forms particles with cellular lipids similar to those composed of the 'major' envelope protein. Such particles carry pre-S1, pre-S2, and S-encoded epitopes and, in addition, a receptor for polymerized human serum albumin.

Distinct H-2-linked regulation of T-cell responses to the pre-S and S regions of the same hepatitis B surface antigen polypeptide allows circumvention of nonresponsiveness to the S region

Recently, additional polypeptide components of the surface envelope of hepatitis B virus (HBV) have been identified. The pre-S(1) and pre-S(2) regions of the HBV genome encode NH2-terminal amino acid residues that together with the S-gene product (25 kDa) comprise polypeptides of 33 kDa and 39 kDa. The possible immunopathologic significance of these larger polypeptides and their relevance to vaccine development prompted us to examine the murine immune response to pre-S(2)-encoded determinants as compared to S-encoded determinants on the same polypeptide. Previous work showed that the pre-S(2) region elicits greater antibody production in vivo than does the S region of hepatitis B surface antigen. In this study, we examined immunogenicity of the pre-S(2) region at the T-cell level, H-2- and non-H-2-linked genetic influences on the pre-S(2) response, and the effect of the immune response to one region on the immune response to the other region. The results indicate that (i) the pre-S(2) region is significantly more immunogenic than the S region at the T-cell level; (ii) pre-S(2)-region-specific T-cell activation is regulated by H-2-linked genes and correlates with the H-2 restriction of in vivo antibody production to the pre-S(2) region; (iii) the H-2 restriction of the T-cell response to the pre-S(2) region is distinct from the H-2 restriction of the T-cell response to S-region determinants; (iv) non-H-2-linked and non-Igh-linked genes also influence the humoral immune response to the pre-S(2) region; and (v) immunization of an S-region-nonresponder, pre-S(2)-region T-cell-responder strain with HBV envelope particles containing both the pre-S(2) and S regions can circumvent nonresponsiveness to the S region through pre-S(2)-specific T-cell helper function.

Enzyme-linked immunoassay of pre-S gene-coded sequences in hepatitis B vaccines

Pre-S gene coded domains of the hepatitis B virus (HBV) envelope protein are highly immunogenic in experimental animals and humans. Their presence in HBV and hepatitis B surface antigen (HBsAg) particles leads to production of anti-pre-S-specific antibodies during the course of HBV infection. Since antibodies specific for pre-S domains are capable of preventing the attachment of HBV to hepatocytes and are virus neutralizing, it would seem desirable to produce HBV vaccines with a standardized level of pre-S determinants to ensure their potential for eliciting the same repertoire of protective antibodies as found after recovery from natural infection. However, a test with appropriate sensitivity for detecting pre-S determinants to ensure their potential for eliciting the same repertoire of protective antibodies as found after (ELISA) for detecting pre-S determinants in vaccines containing less than or equal to 20 micrograms of HBsAg. The components of this assay are (1) antibodies to a synthetic peptide pre-S (120-145) adsorbed to polystyrene beads, and (2) beta-lactamase-labelled antibodies purified from anti-HBV serum on the basis of their affinity for a pre-S (120-174) beta-galactosidase fusion protein produced in Escherichia coli. Results of an evaluation of the pre-S content of HBV vaccines from two different commercial sources are discussed.

The hepatitis B virus

DNA recombinant technology has radically changed hepatitis B virus (HBV) virology. The genetic organization, transcription and replication of the virus are basically understood, structures of integrated HBV sequences in hepatocellular carcinoma have been characterized, and new vaccines produced by recombinant DNA technique are being developed.

Genetic restriction of immune responsiveness to synthetic peptides corresponding to sequences in the pre-S region of the hepatitis B virus (HBV) envelope gene

Proteins of the HBV envelope (env) are coded for by two adjacent regions of the HBV env gene: the pre-S and S regions. Antigenic determinants corresponding to amino acid sequences of both regions are recognized by human antibodies and are important in virus-neutralizing responses. Protective immune responses to HBV appear to be linked to the major HLA histocompatibility complex. Inbred and congenic strains of mice represent a model system relevant for studies on the genetic control of immune responsiveness of humans to HBV envelope proteins. Such mouse strains were ranked according to their antibody response to the S protein and divided into high [d,q], intermediate [a,k,b], and low [s] responders (letters in brackets indicate H-2 haplotype.) Selected pre-S antigenic determinants can be mimicked with high fidelity by synthetic peptide analogues that are immunogenic without any carriers. Thus it is possible to study directly the genetic control of immune responsiveness to pre-S epitopes mimicked by these peptides without having to consider the influence of carriers or of S protein. The results presented here show that inbred mouse strains can be ranked according to their antibody responses to the synthetic peptide pre-S(120-145) as follows: A/J[a] approximately equal to SWR/J[q] greater than C57BL/6J[b] approximately equal to AKR/J[k] approximately equal to SJL/J[s] much greater than DBA/2J[d] greater than BALB/cJ[d]. Only SJL/J[s] mice responded well to another synthetic peptide pre-S (12-32). Thus, H-2-linked genes regulating the immune response to S protein and to epitopes on pre-S-coded sequences are distinct. Anti-pre-S(120-145) responses in S protein-nonresponders circumvent this nonresponsiveness. This should be considered in the design of hepatitis B vaccines.

Expression of hepatitis B virus surface antigen P31 gene in Escherichia coli

A hepatitis B virus surface antigen (HBsAg) P31-coding DNA was constructed from a DNA fragment of the plasmid pHBr330 containing the entire hepatitis B virus (HBV) adr DNA and a chemically synthesized adaptor. The P31 gene was inserted into an expression vector, pTRP771, having an Escherichia coli tryptophan operon (trp) promoter to give a recombinant plasmid pTRP P31-R. The distance between the Shine-Dalgarno (SD) sequence and the initiation codon of P31 gene was adjusted to 9 bp. The expression level of HBsAg by E. coli 294[pTRP P31-R] was significantly elevated, in contrast to that of HBsAg by E. coli 294[pTRP SS-6]. Western blotting analysis has shown that E. coli[pTRP P31-R] synthesizes a specific polypeptide P31 of about 31 kDal, which reacts with anti-HBsAg antibody. The binding studies with polyalbumins from various species have also suggested that HBsAg P31 specifically binds to polymerized human serum albumin.