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

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.

Study on the comparative immunogenicity of a recombinant DNA hepatitis B vaccine containing pre-S components of the HBV coat protein with non pre-S containing vaccines

A new recombinant hepatitis B vaccine (SCI-B-VAC), derived from Chinese hamster ovary (CHO) cells and consisting of both the major S protein and the minor pre-S1 and pre-S2 proteins of the viral coat were compared with two yeast-derived vaccines containing only S proteins (B-Hepavac II and Engerix-B) for immunogenicity in human volunteers in a randomized controlled study. Two hundred and ninety-five healthy subjects completed the 12 month follow up. There was no difference in the mean age and sex distribution among the three study groups. Seroconversion rates for all the three groups were similar at months 6, 9 and 12. However, hepatitis B surface antibody (anti-HBs) geometric mean titres (GMT) were significantly higher with 10 micrograms SCI-B-VAC and 20 micrograms Engerix-B than with 10 micrograms B-Hepavac-II at months 6, 9 and 12. SCI-B-VAC at month 6 also showed a significantly higher anti-HBs GMT than Engerix-B (295 vs 143 miu/mL, P < 0.02).

A Viral Mechanism in Acute Exacerbations of Chronic Type B Hepatitis: Hepatitis B Virus Reinfection and Subsequent Reactivation of Two Viral Strains

Chronic hepatitis B virus (HBV) infections are frequently associated with exacerbations of hepatitis of which the majority are due to reactivation of viral activity. Variation in a viral genome during persistent infection has been shown to be a possible cause for reactivation. In this study, we have found another possible mechanism. HBV in a patient with repeated exacerbations was isolated at six different times during follow-up and was characterized by polymerase chain reaction and DNA sequencing. The first episode of exacerbation was accompanied with increased replication of an HBV strain. The second episode, however, was associated with the sudden appearance of an HBV strain that displayed enough sequence variations to warrant the designation as a separate strain. The results suggested a reinfection event by another independent HBV. Subsequent exacerbations were then related to coactivation of both viral strains. These observations provide significant information toward understanding the acute exacerbations of chronic type B hepatitis. Copyright 2001 S. Karger AG, Basel

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)

Safety and efficacy of a recombinant yeast-derived pre-S2 + S-containing hepatitis B vaccine (TGP-943): phase 1, 2 and 3 clinical testing

A recombinant yeast-derived pre-S2 + S-containing hepatitis B vaccine (TGP-943) was clinically evaluated through three phases of testing in a total of 2137 volunteers. We observed the immunogenic purity of TGP-943 (phase 1), the inter-lot reproducibility of both safety and immunogenicity (phase 2), no significant side-effects, a high capability of inducing both anti-HBs and anti-pre-S2 antibodies (phases 1, 2 and 3), and an ability to induce seroconversion in the majority of vaccines who had been non-responsive to conventional hepatitis B vaccines (phases 2 and 3). In conclusion, TGP-943 is a safe and tolerable vaccine, with special merits: the ability to induce an early anti-pre-S2 response that circumvents the problem of delayed appearance of anti-HBs, and efficacy in non-responders to previous vaccination.

Immunogenicity of a 'pre-S2 plus S' hepatitis B vaccine in healthy adults

The product of the pre-S plus S gene of hepatitis B virus appears to be more immunogenic in mice than the S-gene product (HBsAg) alone. Therefore, we tested the immunogenicity in healthy adults of a hepatitis B vaccine containing the 'middle protein' gene product of pre-S2 plus S (pre-S vaccine). We compared the immunogenicity of three doses of the pre-S vaccine with that of a commercially available recombinant hepatitis B vaccine (Recombivax-HB); 87 seronegative adults were randomized to receive 12 micrograms (group 1), 24 micrograms (group 2), or 48 micrograms (group 3) of the pre-S vaccine or 10 micrograms of Recombivax-HB (group 4) by deltoid injection at 0, 1 and 6 months. Antibody to HBsAg (anti-HBs) appeared after booster vaccination in > or = 94% of vaccinees. Immunogenicity was best in recipients of 48 micrograms of the pre-S vaccine and Recombivax-HB, and geometric mean titres (GMT) for the pre-S vaccine were higher than those for Recombivax-HB only at the pre-S vaccine dose of 48 micrograms (group 3). Antibody to pre-S2 developed in 75% of the pre-S2 vaccine recipients (not in Recombivax-HB recipients) within 7 months. These findings indicate that the pre-S vaccine is immunogenic in healthy adults but that a dose of 48 micrograms of the current formulation is required to equal or exceed the immunogenicity of currently available, recombinant S-only vaccine. Studies in non-responders to S-only vaccines will be necessary to define an immunological advantage of the pre-S vaccines, and additional assessments will be necessary to determine whether anti-pre-S2 enhances protective efficacy.

Cloning and growth-regulated expression of the gene encoding the hepatitis B virus middle surface antigen in Yarrowia lipolytica

Expression of the gene encoding the hepatitis B virus middle surface antigen (pre-HBsAg) in the yeast Yarrowia lipolytica has been studied. The preS2-HBsAg gene was expressed from the alkaline extracellular protease-encoding gene (XPR2) promoter. In the fusion construct, the membrane-spanning 'a' domain of preS2-HBsAg has been replaced by the leader peptide and the proI region of the alkaline protease, thus eliminating the epitope responsible for the immune escape mechanism. Expression has been found to be growth-stage dependent with the highest protein accumulation during the stationary phase, accounting for around 2.35% of the total soluble intracellular proteins. The produced protein was assembled into Dane particles and was immunogenic in mice. The expression vector was found to be stable for at least 100 generations under non-selective conditions.

Analysis of the hepatitis B virus genome and immune response in HBsAg, anti-HBs positive chronic hepatitis

Although the development of antibodies against the hepatitis B virus surface antigen generally leads to the clearance of the infecting virus, anti-HBs reactivity has been reported in patients with chronic hepatitis. In the present study we analyzed the viral genome and the antibody specificity in a series of serum samples collected from a patient who seroconverted to anti-HBs during interferon therapy without clearing HBsAg. The appearance of an anti-HBs response was accompanied by the emergence of a pre-S1 defective viral genome. However, the wild-type adw2 molecular species remained largely dominant during follow up. The patient's antibody response to the surface viral antigens was directed towards the heterologous y subdeterminant and the pre-S1 fragment deleted in the variant hepatitis B virus. These results suggest that the selection of the escape viral mutant does not play a major role in viral persistence.

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.

Evaluation of the immunogenicity of a recombinant vaccine against hepatitis B containing S and pre-S2 sequences using two different schedules

The immunogenicities of hepatitis B virus vaccines containing S and pre-S2 regions were compared using two different schedules of immunization (A: 0-1-2-12 months and B: 0-1-6 months). Two hundred males and females aged 17-22 years were vaccinated with 20 micrograms per dose. The follow-up period was extended up to 13 months. One month after the booster dose anti-HBs were detected in 98.9% of those vaccinated with schedule A and 100% of those vaccinated with schedule B. Geometric mean titres (GMT) of anti-HBs were significantly higher with schedule A than schedule B, reaching GMT of 16269.7 mIU ml-1 and 4372.4 mIU ml-1, respectively, one month after the booster dose. Seroconversion rates for the anti-pre-S2 antibodies one month after the booster dose were 89.4% for schedule A and 76.6% for schedule B. GMT were 157.8 mIU ml-1 and 67.5 mIU ml-1, respectively. We conclude that both vaccines elicit high titres of anti-HBs and anti-pre-S2 antibodies. Immunity lasts longer in schedule A than in schedule B.

Concomitant cellular expression of heat shock regulated genes of hepatitis B virus surface antigen and of human growth hormone by a NIH-3T3 cell line

A plasmid carrying a DNA fragment of hepatitis B virus, coding for the pre-S2 and the entire S region of the surface antigen (HBsAg), placed under the control of the promoter of the human 70 kDa heat shock protein gene (hsp70), was introduced into Line 6, a recombinant cell line that was selected from NIH-3T3 cells previously transfected with a similar construct coding for the human growth hormone cDNA gene (chGH) and with the plasmid pEJ carrying the Ha-rasEJ activated cellular oncogene. The resulting cell line, EMS8, expressed: (1) hsp70/HBsAg and hsp70/hGH hybrid genes, (2) the human Ha-rasEJ oncogene, and (3) the neomycin resistance gene, the two last plasmid markers being used for cell selection. EMS8 cells were able to carry out post-translational modifications of the middle M and the major S envelope proteins of HBV, such as assembly and glycosylation. Accordingly, the cells synthesized and secreted both free and glycosylated M and S viral proteins, and the human growth hormone protein. In addition concomitant expression of HBsAg and hGH proteins as well as their mRNA were detected in EMS8 cells at least up to 72 hr after heat induction instead of 24 hr in the case of hGH in Line 6 cells.

Cellular recognition and HLA restriction of a midsequence HBsAg peptide in hepatitis B vaccinated individuals

Vaccination with native HBsAg results in both a humoral and a cellular immune response in humans. In individuals who responded to vaccination, the HBsAg (S region) specific response, as measured by cell proliferation, diminished significantly after 12 weeks, a time when the antibody response was still vigorous. Reduced and nonreduced HBsAg were equivalent in eliciting lymphocyte proliferation. Anti-MHC class II monoclonal antibodies were used in blocking studies to demonstrate that anti-HLA-DR but not anti-HLA-DQ or anti-HLA-DP inhibited specific lymphocyte proliferation to HBsAg. Both the monomer (reduced) and dimer (nonreduced) forms of an immunodominant midsequence HBsAg peptide (amino acid residues 139-146) produced lymphocyte proliferation roughly comparable to that induced by whole HBsAg in 6 of 7 responders immunized with whole HBsAg and the peptide-induced proliferation was blocked by anti-HLA-DR but not by anti-HLA-DP antibodies. These results suggest that HBsAg p 139-146 is a major immunodominant peptide of HBsAg and is restricted by HLA-DR.

Vaccination against hepatitis B: the Italian strategy

Viral hepatitis B, which is a major health problem worldwide, is endemic in Italy. In response to this, vaccination became compulsory in 1991. Vaccine is administered to neonates and 12-year-old adolescents; in 12 years time, all Italians under the age of 24 will be immune to HBV.

Determination of the minimal length of preS1 epitope recognized by a monoclonal antibody which inhibits attachment of hepatitis B virus to hepatocytes

The minimal amino acid sequence sufficient to be recognized efficiently by virus-attachment inhibiting murine monoclonal anti-preS1 antibody MA18/7 has been determined. We have constructed a recombinant gene library using the cloned coat protein gene of Escherichia coli RNA bacteriophage fr as a carrier. Different fragments of preS1 region from cloned hepatitis B virus (HBV) genomes, subtype ayw and adw, were inserted at position 2 of the 129 amino acid-long fr coat protein gene in the appropriate E. coli expression vectors. Fine mapping of preS1 epitope recognized by MA18/7 was accomplished by bidirectional shortening of the preS1 within original recombinant preS-fr coat protein genes with Bal31 exonuclease. Immunoblot analysis of the obtained recombinant protein library revealed that the tetrapeptide Asp-Pro-Ala-Phe (DPAF), located at the position preS(31-34) and conserved in all known HBV genomes, is sufficient to bind MA18/7 antibody. Recognition of the preS1 region by MA18/7 occurred irrespective of the amino acid context surrounding this DPAF tetrapeptide. Further shortening of this minimal epitope from the left or from the right side completely prevented antibody binding in immunoblots.

Recombinant DNA hepatitis B vaccine containing Pre-S components of the HBV coat protein--a preliminary study on immunogenicity

A novel recombinant hepatitis B vaccine, trademarked Sci-B-Vac, was evaluated for safety, tolerability and immunogenicity in an open label trial performed in Singapore. The experimental vaccine, derived from Chinese hamster ovary (CHO) cells, consists of hepatitis B surface antigen (HBsAg) particles harbouring all three viral envelope polypeptides, the major S protein and the minor Pre-S2 and Pre-S1, in their glycosylated and non-glycosylated forms. The vaccine was administered intramuscularly at 0, 1 and 6 months. No unexpected adverse effects were observed. A high level anti-HBs response to Sci-B-Vac was indicative of its immunogenicity. Subsequent to the third injection, 100% and 92% of the 10 micrograms and 5 micrograms dose recipients, respectively, were seroprotected (anti-HBs titres greater than or equal to 10 mIU ml-1). Moreover, the geometric mean titres (GMT) of the anti-HBs response were very high: 2687 and 1473 mIU ml-1, respectively. An immunogenic advantage of Sci-B-Vac was also suggested by the rapid onset of antibody response: 96% of the 10 micrograms dose recipients were seroprotected with a GMT of 159 mIU ml-1, prior to the third injection.

Comparative immunogenicity in children of mammalian cell-derived recombinant hepatitis B vaccine and plasma-derived hepatitis B vaccine

Three doses of hepatitis B vaccine were given at 2, 4 and 9 months of age to 220 Senegalese infants living in the Dakar area of Senegal. Half of the infants received 5 micrograms plasma-derived hepatitis B vaccine (Hevac B) and the remainder 20 micrograms mammalian cell-derived recombinant hepatitis B vaccine (GenHevac B). Both vaccines contain S and pre-S2 encoded proteins; however, the recombinant vaccine had a much higher pre-S2 content than the plasma-derived vaccine. Adverse reactions to both vaccines were limited to mild and transient soreness at the injection site. Fever was reported in 14-21% of the infants and was likely to be related to DTP-polio vaccine which was given simultaneously. After the two first doses, seroconversion rates and geometric mean titres of anti-HBs were higher in infants receiving the recombinant vaccine than in infants receiving the plasma-derived vaccine. After completion of vaccination, all infants in both groups had protective levels of anti-HBs antibodies. The recombinant vaccine induced more rapidly antibodies directed against S and pre-S2 epitopes. Anti-pre-S2 antibodies were detected after the first injection of GenHevac B and only after the third injection of Hevac B. From the data, GenHevac B vaccine is expected to be as effective as Hevac B vaccine for controlling hepatitis B infection.

Persistence of antibody to hepatitis B surface antigen after low-dose, intradermal hepatitis B immunization and response to a booster dose

To determine the duration of antibody after low-dose, intradermal (i.d.), plasma-derived hepatitis B vaccination and the response to a booster dose, we studied two classes of medical students who were immunized with 2 micrograms doses i.d. In one class, 73/88 (85%) who had been immunized by skilled personnel at 0, 1 and 6 months, had protective concentrations (greater than or equal to 10 mIU ml-1) of anti-HBs at 20 months after the first dose. Twelve (92%) out of 13 students who received only two doses at 0 and 1 months also had protective concentrations at month 20. At month 27, 11/16 (69%) with antibody less than or equal to 10 mIU ml-1 responded to a fourth dose of 2 micrograms i.d. with protective concentrations of anti-HBs. In the second class, after three doses of vaccine at 0, 1, and 6 months, protective concentrations of anti-HBs were present in 90/93 (97%) at 14 months and in 71/80 (89%) at 25 months. In those who received only two doses, protective concentrations were found in 24/31 (74%) at 14 months and 9/16 (56%) at 25 months. After a booster dose of 2 micrograms i.d. at month 25, anti-HBs concentrations rose from a geometric mean of 78 to 1198 mIU ml-1 in 60 subjects previously immunized with three doses and from 18 to 1054 mIU ml-1 in 16 students previously immunized with only two doses. Overall, 73/76 (96%) of students in the second group had protective concentrations of antibody after the booster dose.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Mapping of linear B-cell epitopes of hepatitis B surface antigen

Eight monoclonal antibodies directed against the surface protein of hepatitis B virus (HBV) were tested using an epitope-mapping system (Pepscan) for characterizing antigenic domains. Four different amino acid sequences corresponding to linear epitopes were identified: one in pre-S1 corresponding to the sequence 29-36, two in pre-S2 corresponding to overlapping sequences 134-141 and 137-144, and one in the S region of the protein corresponding to the amino acid sequence 117-126.

Hepatitis B virus antigen-specific T-cell activation in patients with acute and chronic hepatitis B

Since the hepatitis B virus is noncytopathic, it is generally believed that the individual specific immune response determines the course of infection. The lack of data about hepatitis B virus-specific T-cell reactions in acute infection led us to investigate the specific cellular immune response of infected individuals in terms of proliferation, and gamma-interferon and lymphotoxin production. Our results demonstrate that peripheral blood mononuclear cells (PBMNC) from patients with acute and chronic hepatitis B respond weakly to HBsAg. In contrast, patients with acute hepatitis show a vigorous response to the nucleocapsid antigen (HBcAg) in terms of proliferation and lymphokine production, while only few chronic virus carriers gave a proliferative response. Either of the antigens could activate lymphocytes to produce gamma-interferon and lymphotoxin, cytokines which may modulate antiviral immune response.

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

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

Structural relationships between hepatitis B surface antigen in human plasma and dimers from recombinant vaccine: a monoclonal antibody study

Ten monoclonal antibodies were obtained from mice immunized with a yeast recombinant hepatitis B vaccine. They were selected at an early stage for their ability to bind to native surface antigen particles (HBsAg) in human plasma. All antibodies recognized conformational epitopes which were destroyed completely or almost completely by reduction of disulphide bridges. They were divided into five epitope groups by their competition for binding to recombinant S protein, though epitopes within each group are not identical. Recombinant S protein migrated on SDS-PAGE in the absence of reducing agents as a mixture of monomers and dimers/oligomers. Sucrose gradient analysis suggests that all these forms are co-aggregated into HBsAg-like particles. On Western blots, all ten antibodies either bound only to dimers/oligomers or strongly preferred them over monomers. The results suggest that, of the antibodies produced in response to recombinant vaccine in mice, most of those which bind strongly to 'native' HBsAg particles in human plasma recognize surface structures created by interaction between two subunits.

Anti-pre-S2 antibody response in subjects vaccinated against hepatitis B and in naturally immunized subjects

Serum samples from individuals immunized with a pepsinized or non-pepsinized vaccine and from patients who had recovered from acute hepatitis B or who developed a chronic form of the disease, were analysed for the presence of antibody against the pre-S2 epitope of the hepatitis B virus. Anti-pre-S2 antibody was absent in all but one individual immunized with the pepsinized vaccine. Thirty-eight percent of the subjects who responded by anti-HBs production to the non-pepsinized preparation showed anti-pre-S2 antibody one year after complete vaccination. Among subjects who did not produce anti-HBs after immunization with this vaccine, 1 single individual produced anti-pre-S2 antibody. Anti-preS2 antibody was detectable after one year in 38% of the patients who recovered from acute hepatitis B, but in none of those with chronic hepatitis B. The kinetics of anti-pre-S2 antibody response to a booster injection was also analysed 1 month and 1 year after the 3rd injection and 1 month after the 4th injection of the non-pepsinized vaccine.

Immunogenicity and safety in newborns of a new recombinant hepatitis B vaccine containing the S and pre-S2 antigens

A study to evaluate the safety and immunogenicity of a recombinant hepatitis B vaccine containing the S and pre-S2 antigens (GenHevac B Pasteur) was conducted in healthy newborn infants. All infants received 20 micrograms of vaccine within 24 h of birth and at 1 and 2 months with a booster injection at month 12. The vaccine was administered alone in 19 infants born to low risk mothers, i.e. surface antigen (HBsAg)-negative and antibody to the core antigen (Anti-HBc)-positive mothers. The vaccine was administered in combination with 100 IU hepatitis B immune globulin (HBIg) at birth and 1 month in 18 infants born to high risk mothers, i.e. HBsAg positive mothers. In the group not receiving HBIg, the anti-HBs seroconversion rate at the 10 mIU ml-1 threshold was 50% 1 month after the first injection. In both groups, the anti-HBs seroconversion rates were 100% 1 month after the third injection and greater than 85% 1 month after the second injection. After the booster injection greater than 90% of the infants had an anti-HBs titre greater than 1000 mIU ml-1 which will probably provide them with adequate protection for several years. The kinetics of the anti-pre-S2 response was similar to that of the anti-HBs response and 100% of infants in both groups had seroconverted 1 month after the second injection of the vaccine. The side effects were scarce, all mild and transient.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Identification of immunodominant T cell epitopes of the hepatitis B virus nucleocapsid antigen

Several lines of experimental evidence suggest that inclusion of core sequences in the hepatitis B vaccine may represent a feasible strategy to increase the efficacy of the vaccination. In order to identify immunodominant core epitopes, peripheral blood T cells purified from 23 patients with acute hepatitis B and different HLA haplotypes were tested with a panel of 18 short synthetic peptides (15 to 20 amino acids [AA]) covering the entire core region. All patients except one showed a strong T cell proliferative response to a single immunodominant 20 amino acid sequence located within the aminoterminal half of the core molecule. Two additional important sequences were also identified at the aminoterminal end and within the carboxyterminal half of the core molecule. These sequences were able to induce significant levels of T cell proliferation in 69 and 73% of the patients studied, respectively. T cell response to these epitopes was HLA class II restricted. The observations that (a) polyclonal T cell lines produced by PBMC stimulation with native HBcAg were specifically reactive with the relevant peptides and that (b) polyclonal T cell lines produced with synthetic peptides could be restimulated with native HBcAg, provide evidence that AA sequences contained within the synthetic peptides represent real products of the intracellular processing of the native core molecule. In conclusion, the identification of immunodominant T cell epitopes within the core molecule provides the molecular basis for the design of alternative and hopefully more immunogenic vaccines.

Improvement of hepatitis B vaccine by the use of a new adjuvant

Humoral and cellular immune responses of mice and guinea-pigs to hepatitis B virus surface antigen when alum-precipitated or administered with Syntex Adjuvant Formulation (SAF) were compared. Two doses of HBsAg in SAF were sufficient to elicit antibody responses, and using SAF the dose of antigen could be reduced to one-tenth of that required to elicit antibody responses by alum-adjuvanted HBsAg. The use of SAF increased and made more consistent the antibody responses in young mice and in strains of mice with inherited low responses to HBsAg. Cellular responses to HBsAg were more consistently observed when SAF was used than when alum was used. SAF increased the formation of IgG2a antibodies in mice except in the B10.M strain; antibodies of this isotype activate complement and act synergistically with antibody-dependent effector cells more efficiently than antibodies of other isotypes. If SAF proves acceptable for human use it could improve vaccines against hepatitis B virus.

Comparative safety and immunogenicity of yeast recombinant hepatitis B vaccines containing S and pre-S2 + S antigens

One hundred and four healthy, hepatitis B virus (HBV) seronegative males were enrolled in a single blind, randomized pilot study to compare antibody and clinical responses to a yeast recombinant pre-S2 + S vaccine and a yeast recombinant S antigen vaccine (Recombivax HBR). Participants received either a 12, 24 or 48 micrograms dose of pre-S2 + S vaccine (with a 1:5 ratio by weight of pre-S2 and S antigens) or a 10 micrograms dose of Recombivax HBR by intramuscular injection at 0, 1 and 6 months; their serological and biochemical responses were measured at 0, 1, 2, 3, 6 and 7 months, while their clinical responses were monitored for 5 days after each injection. The proportion of vaccines with minor local or systemic complaints (mainly sore arm, malaise, myalgia, fatigue) and the proportion developing antibody to surface antigen (anti-HBs) were similar for all vaccine groups. Transient elevations in alanine aminotransferase occurred infrequently. By 7 months almost all vaccinees developed anti-HBs, but titres were generally higher among recipients of pre-S2 + S vaccine. Antibody to pre-S2 antigen developed in 70-75% by 2 months and in 91-96% by 7 months. These data imply that the recombinant yeast pre-S2 + S vaccine is as well tolerated and as immunogenic as Recombivax HBR. Further studies are being conducted to assess antibody responses in larger numbers of healthy adults as well as in special populations with sub-optimal responses to currently licensed hepatitis B vaccines.

The cellular basis for lack of antibody response to hepatitis B vaccine in humans

We had previously obtained evidence that among normal subjects the humoral antibody response to hepatitis B surface antigen (HBsAg) was bimodally distributed with about 14% of subjects producing less than 1,000 estimated radioimmunoassay RIA units. From the study of major histocompatibility complex (MHC) markers in the very poor responders who produced less than 36 estimated RIA units of antibody, it appeared that there was an excess of homozygotes for two extended haplotypes [HLA-B8, SC01, DR3] and [HLA-B44, FC31, DR7]. This finding suggested that a poor response was inherited as a recessive trait requiring nonresponse genes for HBsAg on both MHC haplotypes and was strengthened by finding a much lower antibody response among prospectively immunized homozygotes for [HLA-B8, SC01, DR3] compared with heterozygotes. In the present study, we have analyzed the cellular basis for nonresponse to this antigen by examining antigen-specific proliferation of T cells from responders and nonresponders in the presence and absence of autologous CD8+ (suppressor) cells. Peripheral blood cells from nonresponders to HBsAg failed to undergo a proliferative response to recombinant HBsAg in vitro, whereas cells from responders proliferated vigorously. This failure of cells from nonresponders to proliferate was not reversed in cell mixtures containing CD4+ and antigen-presenting cells devoid of CD8+ cells. There was no difference between responders and nonresponders with respect to the number of circulating T cells or their subsets, or the proliferative response to mitogens such as pokeweed or phytohemagglutinin or another antigen, tetanus toxoid. Our results indicate that our HBsAg nonresponding subjects have a very specific failure in antigen presentation or the stimulation of T helper cells, or both. Our evidence is against specific immune suppression as the basis for their nonresponsiveness. The failure of antigen presentation or T cell help is consistent with recessive inheritance of nonresponsiveness and suggests that response is dominantly inherited.

Immunomodulator, LZ-8, prevents antibody production in mice

LZ-8, a new and recently discovered immunomodulator from Ganoderma lucidum, has been shown to have immunosuppressive activity in vivo and to be a member of the immunoglobulin superfamily. In this paper we examined the in vivo effect of LZ-8 on antibody production using the hepatitis B surface antigen (HBs Ag) in mice. LZ-8 had mitogenic activity in vitro towards spleen cells of C57BL/10 (B10) and C57BL/10BR (B10BR) as previously shown towards those of DBA/2 mice. B10 and B10BR mice produced anti-HBs Ag antibody by the twice sensitization of the antigen while intraperitoneal administration of LZ-8 twice weekly into the mice (8 and 12 mg/kg) greatly prevented the production of antibody to HBs Ag (83.3-96.8% inhibition). We further examined the effect of LZ-8 administration on mitogen responsibility of spleen cells and on the T-cell subset population in both the spleen and lymph node but no significant differences were observed between the LZ-8 treated and untreated mice. These results suggest that the immunosuppressive activities of LZ-8, previously shown, such as the prevention of systemic anaphylaxis and the Arthus reactions, were caused by the blocking of antigen-specific antibody production.

Hepatitis B vaccination of haemodialysis patients: randomized controlled trial comparing plasma-derived vaccine with and without pre-S2 antigen

The pre-S2 protein of the hepatitis B virus envelope evokes anti-pre-S2 antibodies and enhances the anti-HBs response after vaccination in mice. In order to evaluate the immunogenicity of the pre-S2 Ag in man, 102 HBsAg, anti-HBs, anti-HBc-negative haemodialysis patients were vaccinated at random according to one of four vaccination schedules: 5 micrograms plasma vaccine Pasteur (containing 1% pre-S2) or 20 micrograms plasma vaccine MSD (no pre-S2) at 0, 1, 2, 4, 6 and 12 months; or 10 micrograms Pasteur or 40 micrograms MSD at 0, 1, 2 and 6 months. Anti-HBs levels were measured by RIA and expressed in IU l-1; anti-pre-S2 response was evaluated by both EIA and Western blot analysis. Eighty-four per cent (95% confidence interval: 75-93) of the patients exhibited an anti-HBs response of 2 IU l-1 or more and 71% (95% confidence interval: 61-81) reached an anti-HBs level of at least 10 IU l-1 within 13 months of the start of vaccination. Anti-HBs response correlated with age (the response rate decreased with increasing age) but not with either the type of vaccine or dosage. An anti-pre-S2 response was observed in 16% (EIA) and 46% (Western blot) of the patients immunized with the Pasteur vaccine and none (EIA, Western blot) of the MSD group. The level of anti-pre-S2 antibodies correlated with high anti-HBs titres; an anti-pre-S2 response occurred in only one anti-HBs-negative patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Priming effect of recombinant vaccinia virus coding for the middle hepatitis B surface antigen

Recombinant vaccinia virus expressing the middle hepatitis B virus surface antigen was incapable of inducing marked antibody response against the S and pre-S2 antigenic specifities in mice. However, mice immunized with this virus produced antibodies to both these antigens after the following administration of subtreshold doses of plasmatic hepatitis B surface antigen.

Antibody response to preS1 in hepatitis-B-virus-induced liver disease and after immunization

Antibodies to the pre-S1-encoded sequence of hepatitis B virus (HBV) envelope were detected by ELISA using a synthetic peptide analogue of preS1 proteins, in different groups of HBV-infected subjects and also in hepatitis B vaccine recipients. Such antibodies were specifically found in only 1% of HBsAg chronic carriers including patients with cirrhosis and primary liver cancer. Anti-preS1 were detected in patients with acute hepatitis; in 13% of the HBsAg+ sera obtained before recovery and in 37% of the sera obtained after recovery. Anti-preS1 antibodies were detected in recipients of a plasma-derived vaccine, but not in those receiving a recombinant vaccine. The results indicate that anti-preS1 is an earlier serum marker of HBV clearance than anti-preS2 and anti-S antibodies.

HLA-Bw54-DR4-DRw53-DQw4 haplotype controls nonresponsiveness to hepatitis-B surface antigen via CD8-positive suppressor T cells

We have previously reported that in nonresponders to hepatitis-B (HB) vaccine there was an HLA-linked immune suppression gene for hepatitis-B surface antigen (Is-HBsAg) controlling the nonresponsiveness to HBsAg, through HBsAg-specific suppressor T cells, and that the Is-HBsAg was in strong linkage disequilibrium with the HLA-Bw54-DR4-DRw53 haplotype (1). We have now done the HLA typing on an additional 6 nonresponders, and using the system of T-cell proliferative response to HBsAg we found that the Is-HBsAg controlled the nonresponsiveness to HBsAg through HBsAg-specific suppressor T cells in nonresponders to HB vaccine who have HLA-Bw54-DR4-DRw53-DQw4 haplotype. T- and B-cell recognition of HB vaccines might play an important role at 3 to 5 weeks after the last immunization. Use of an anti-HLA monoclonal antibody has shown that the HLA-DR molecule plays an important role in helper T-cell proliferation in nonresponders, although the role of HLA-DQ molecule in nonresponders was unclear.

Significance of anti-pre-S antibodies in patients with fulminant hepatic failure

Anti-pre-S antibody was tested in 38 sera from patients with fulminant hepatitis (positive for HBsAg and/or IgM anti-HBc) using a specific solid phase enzyme linked immunosorbent assay (ELISA). Anti-pre-S activity was detected in 50 percent sera samples positive for HBsAg but negative for IgM anti-HBc. There were 12.5% sera positive for both HBsAg as well as IgM anti-HBc and 75% sera negative for HBsAg but positive for IgM anti-HBc. The prevalence of HBV-specific DNA-polymerase activity was high in all the three groups whereas anti-HBs positivity was low. Anti-pre-S activity was observed both in the presence as well as in the absence of DNA-polymerase activity. High-anti-pre-S level in fulminant hepatitis B patients was assumed to be implicated in the fast clearance of HBsAg from circulation.

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

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

Protective efficacy of a novel hepatitis B vaccine consisting of M (pre-S2 + S) protein particles (a third generation vaccine)

The protective efficacy of a new type of yeast-derived hepatitis B (HB) vaccine (TGP-943, subtype adr), which was formulated from modified M (pre-S2 + S; P31) protein (M-P31c) particles, was investigated in chimpanzees. Animals were injected intramuscularly three times at 4-week intervals with doses of 10 or 40 micrograms (as a protein) of TGP-943. There were no significant differences in the immunogenicity of 10 micrograms compared to that of 40 micrograms of TGP-943 in terms of anti-S antibody response, while the induction and persistence of anti-pre-S2 antibodies seemed dose-related. Chimpanzees, vaccinated with 40 micrograms of TGP-943, produced anti-pre-S2 antibodies 2 weeks after the first injection, which appeared earlier than anti-HBs (S) antibodies. A maximum level of the anti-pre-S2 antibodies was reached 2 weeks after the second injection. Apart from immunization with TGP-943, chimpanzees injected with denatured TGP-943, consisting of 10 micrograms (as a protein) of non-particulate M-P31c antigen, produced anti-pre-S2 antibodies with a non-protecting level of anti-S antibodies (less than 10 mIU ml-1). Five weeks after the third injection, all animals were challenged intravenously with 1000 chimpanzee infectious units of HBV subtype (ayw) and were protected as confirmed by normal serological markers, no signs of infection in the sera and liver biopsies, and no detection of HBV-DNA by PCR method. No side effects from inoculation with TGP-943 or denatured TGP-943 were also encountered in any animals.

Immunohistochemical study of pre-S(2) antigen in liver and serum of patients with chronic hepatitis B

To evaluate the significance of pre-S(2) in the liver, the authors studied the relationship between serum and intrahepatic pre-S(2) in 27 patients with chronic hepatitis B. Intrahepatic expression of pre-S(2) was observed under light and electron microscopy and compared with that of HBsAg and HBcAg. All patients were positive for hepatic pre-S(2), and 25 for serum pre-S(2). Intrahepatic pre-S(2) expression was membranous or both membranous and cytoplasmic in 18 cases and was cytoplasmic in 9. The serum levels of pre-S(2) were significantly higher in cases whose intrahepatic pre-S(2) was membranous than in the cytoplasmic cases. These findings indicate that membranous expression of pre-S(2) reflects its secretion into the circulation. Intrahepatic pre-S(2) expression was found almost completely to resemble that of HBsAg on both light and electron microscopy. Membranous pre-S(2) was seen in the liver of 16 of 25 cases who were positive for intrahepatic HBcAg. In detailed studies of membranous pre-S(2) and HBcAg, both membranous pre-S(2) and HBcAg appeared in the liver of all 7 cases before or at the peak of acute exacerbation, but after it, membranous pre-S(2) was not found in 4 of 8 cases. These results suggest that disappearance of membranous pre-S(2) and HBsAg may be related to hepatic cell necrosis in some cases with acute exacerbation.

Humoral immune responses in mice using gamma inulin preparations as adjuvants for hepatitis B vaccines

There is an urgent need for new, powerful adjuvants suitable for use with sub-unit and peptide vaccines in humans. We have measured the humoral immune response in BALB/c mice to vaccine formulations using recombinant HBsAg antigens, and gamma inulin and alum adjuvants. Using Merck, Sharpe & Dohme (MSD) HBsAg at 10 micrograms/mL, high levels of anti-HBs were generated and geometric mean S/N ratios of 88, 133 and 107 were obtained for alum absorbed vaccine, gamma inulin, and a mixture of the two adjuvants, respectively. A dilution series produced ED50 values of 0.08, 0.15 and 0.22 micrograms/mL respectively. In a second series of experiments comparing alum and algamulin (a complex of gamma inulin and alum), MSD HBsAg induced anti-HBs levels of 81 and 52, and ED50 values of 0.3 and 0.4 when used in conjunction with alum and algamulin, respectively. SKF HBsAg induced anti-HBs levels of 126 and 111 with alum and algamulin, and ED50 values of 0.11 and 0.075. The class, subclass and level of antibody produced in mice boosted with a second dose of vaccine at 21 days was also examined. Both alum and gamma inulin induced higher levels of total antibody, IgG1 and minor IgG subclasses than algamulin, or HBsAg alone. Overall, gamma inulin appears to be an equivalent adjuvant to alum, although their mechanisms of action are different. Mixtures or complexes of the two adjuvants appear to be less effective in inducing humoral immune responses in mice than either alone.

The N-terminal (pre-S2) domain of a hepatitis B virus surface glycoprotein is translocated across membranes by downstream signal sequences

The coding region for the hepatitis B virus surface antigens contains three in-phase ATG codons which direct the synthesis of three related polypeptides. The 24-kilodalton major surface (or S) glycoprotein is initiated at the most distal ATG and is a transmembrane protein whose translocation across the bilayer is mediated by at least two uncleaved signal sequences. The product of the next upstream ATG is the 31-kilodalton pre-S2 protein, which contains 55 additional amino acids attached to the N terminus of the S protein. This pre-S2-specific domain is translocated into the endoplasmic reticulum. Using a coupled in vitro translation-translocation system, we showed that (i) the pre-S2 domain itself lacks functional signal sequence activity, (ii) its translocation across the endoplasmic reticulum membrane is mediated by downstream signals within the S domain, and (iii) the N-terminal signal sequence of the S protein can translocate upstream protein domains in the absence of other signals. The hepatitis B virus pre-S2 protein is an example of a natural protein which displays upstream domain translocation, a phenomenon whose existence was originally inferred from the behavior of synthetic fusion proteins in vitro.

Anti-PreS2 antibody assay for evaluating immune responses among recipients of recombinant hepatitis B PreS2 + S vaccine

A competitive radioimmunoassay was developed for measuring hepatitis B virus (HBV) anti-PreS2 antibody. The assay has been demonstrated to be highly specific for anti-PreS2 antibody and not subject to interference by other antibodies to HBV-specific antigens. This assay was used to evaluate anti-PreS2 antibody responses in a hepatitis B PreS2 + S vaccine human clinical trial in healthy adults.

Effect of the N-terminal hydrophobic sequence of hepatitis B virus surface antigen on the folding and assembly of hybrid beta-galactosidase in Escherichia coli

To investigate the mechanism of inclusion body formation and the effect of a hydrophobic sequence on the in vivo polypeptide folding, the aggregation caused by recombinant fusion beta-galactosidase in Escherichia coli was examined. Two plasmids were constructed: pTBG(H-) carried only the preS2 sequence of the hepatitis B virus surface antigen (HBsAg) in front of the beta-galactosidase gene (lacZ) while pTBG(H+) carried an additional sequence encoding the amino-terminal hydrophobic sequence of the S region of HBsAg between preS2 and lacZ. Unlike cells expressing the fusion protein not containing the hydrophobic sequence, E. coli JM109/pTBG(H+) exhibited temperature-sensitive production of beta-galactosidase. As the culture temperature increased the activity decreased dramatically. This decrease in activity was not due to a decrease in fusion polypeptide production, but rather the fusion polypeptides containing the hydrophobic sequence aggregated within the cells at high temperature. However once the fusion polypeptides folded into proper conformation at low temperature, they maintained the activity even at high temperature. The results indicate that aggregation is a consequence of incorrect folding and assembly of the polypeptides, and is not derived from the native structure. The aggregates of the pTBG(H+)-encoded fusion polypeptides did not revert to active form when the culture temperature was lowered.