A mathematical model predicting anti-hepatitis B virus surface antigen (HBs) decay after vaccination against hepatitis B

The determination of serum levels of antibodies against hepatitis B virus surface antigen (anti-HBs) after hepatitis B vaccination is currently the only simple test available to predict the decay of protection and to plan the administration of booster doses. A total of 3085 vaccine recipients of plasma-derived and recombinant vaccine have been followed for 10 years to determine the kinetics of anti-HBs production and to construct a mathematical model which could efficiently predict the anti-HBs level decline. The anti-HBs peak level was reached 68 days after the last dose of recombinant vaccine and 138 days after the last dose of plasma-derived vaccines. The age of vaccinees negatively influenced the anti-HBs levels and also the time necessary to reach the anti-HBs peak. A bilogarithmic mathematical model (log10 level, log10 time) of anti-HBs decay has been constructed on a sample of recombinant vaccine recipients and subsequently validated on different samples of recombinant or plasma-derived vaccine recipients. Age, gender, type of vaccine (recombinant or plasma-derived), number of vaccine doses (three or four) did not influence the mathematical model of antibody decay. The program can be downloaded at the site: http:@www2.stat.unibo.it/palareti/vaccine.htm . Introducing an anti-HBs determination obtained after the peak, the program calculates a prediction of individual anti-HBs decline and allows planning of an efficient booster policy.     

Immunogenicity of low doses of hepatitis B vaccine in children: a study in 650 New Zealand children

Six hundred and fifty New Zealand children from 2-12 years of age were vaccinated three times with 2 mcg intramuscular (IM) doses of Merck Sharp and Dohme plasma-derived hepatitis B vaccine (H-B-Vax), at 0, 1, and 6 months, and tested 2-3 months later for antibody to hepatitis B surface antigen (anti-HBs) by radioimmunoassay (RIA). Overall, 96.5% of the children seroconverted for anti-HBs by RIA, having levels greater than 2.1 RIA S/N units, with 91.2% having values greater than 10 S/N units. Anti-HBs levels were also determined by enzyme immunoassay (EIA), by which method a significantly better response was demonstrated in 2-4-year-olds than in older children. This study demonstrated that a satisfactory anti-HBs response was obtained using one-fifth of the recommended doses of hepatitis B vaccine.     

Development and Technical and Clinical Validation of a Quantitative Enzyme-Linked Immunosorbent Assay for the Detection of Human Antibodies to Hepatitis B Surface Antigen in Recipients of Recombinant Hepatitis B Virus Vaccine

Pending removal from the market of a commercial assay (the AUSAB [Abbott Laboratories] enzyme immunoassay [EIA]) for the determination of antibodies to hepatitis B surface antigen (HBsAg), a new in-house quantitative enzyme-linked immunosorbent assay (ELISA) to measure antibodies against HBsAg (anti-HBs) was developed (anti-HBs in-house). Specific anti-HBs antibodies were sandwiched between the precoated HBsAg ad and ay subtypes purified from plasma from hepatitis B virus (HBV) human carriers and the recombinant HBsAg adw2 subtype tagged with horseradish peroxidase. The assay was calibrated against the 1st International Reference Preparation for anti-hepatitis B immunoglobulin (lot 1977-W1042). Analytical sensitivity and the limit of quantitation were estimated at 0.43 mIU/ml and 2.0 mIU/ml, respectively. Overall reproducibility was 11.86%, and accuracy was estimated to be 94.89%. More than 4,000 samples from seven clinical trials were tested with the anti-HBs in-house assay and compared to results generated with AUSAB EIA and AUSAB radioimmunoassay (RIA). During the technical validation, the anti-HBs in-house assay was compared to the AUSAB RIA as a reference (n = 919). Overall assessment of concordance and Deming''s regression analysis were performed. The coefficient of correlation between the AUSAB RIA and anti-HBs in-house assay was 0.9815 with a slope of 0.9187. The overall agreement between anti-HBs in-house and AUSAB RIA was 97.61%, considering the clinical cutoffs at 3.3 mIU/ml and 1.0 mIU/ml for the respective assays. From a clinical perspective, seroprotection rates and anti-HBs geometric mean antibody concentrations for individual studies calculated with either the in-house assay or the reference assays were similar. Conclusions of individual studies were confirmed. The performance characteristics of the in-house assay are acceptable. There is no evidence that use of the new assay would lead to different clinical conclusions from the reference method.Hepatitis B infection is a global health problem but most acutely affects developing countries (16). Currently there is no effective therapy against hepatitis B, whose disease spectrum ranges from asymptomatic disease to chronic liver diseases, including cirrhosis and hepatocellular carcinoma. Prevention of the illness through vaccination remains the method of choice for its control and eradication. Active immunization against hepatitis B infection can be achieved using vaccines containing either inactivated hepatitis B virus (HBV) surface protein (HBsAg) physicochemically purified from plasma from HBV human carriers or recombinant surface antigen produced by transfer of the S gene of HBV coding for HBsAg to an appropriate plasmid that is then inserted into the desired expression vector. The recombinant vaccine manufactured by GlaxoSmithKline Biologicals (GSK) is produced in yeast and is antigenically similar to plasma-derived HBsAg (4). Clinical studies of this recombinant vaccine either formulated as a single-component vaccine (Engerix-B; trademark of GSK) or formulated in combination with other antigens such as hepatitis A vaccine (Twinrix; trademark of GSK) or pediatric diphtheria-tetanus-pertussis-based vaccines (such as Infanrix hexa and Tritanrix HepB; trademarks of GSK) have proven its efficacy and immunogenicity (5).To date, commercial assays from Abbott Laboratories have been used at GSK to quantify the immune response to HBV vaccines in terms of antibodies against HBsAg (anti-HBs). However, since these assays are no longer commercially available in Europe, GSK has developed an in-house assay with adequate technical and clinical performance to ensure long-term supply of an assay with consistent quality. This paper describes the development, technical validation, and the clinical assessment of the new anti-HBs in-house assay.     

Comparison of the immunogenicity of reduced doses of two recombinant DNA hepatitis B vaccines in New Zealand children

A group of 201 hepatitis B virus (HBV) sero-negative children 1-12 years of age received either three 2 micrograms doses of Merck Sharp and Dohme (MSD) or Smith Kline and French (SKF) recombinant DNA (rDNA) hepatitis B vaccine I.M. at monthly intervals. Each recipient was tested 4-6 weeks later for antibody to hepatitis B surface antigen (anti-HBs) by enzyme immunoassay (EIA) and radioimmunoassay (RIA). Ninety-six 4-5-year-old children, given 2 micrograms doses of a plasma-derived vaccine (MSD, H-B-Vax) I.M. at 0, 1, 2 months, were tested at the same time with the same assays for comparison. Anti-HBs responses and geometric mean titres (GMT) were significantly higher with the MSDrDNA vaccine (96% and 338.9 IU/liter) than with the SKF/r DNA vaccine (82.3% and 69.4 IU/liter). We conclude that for the protection of young children, 2 micrograms doses of the MSD rDNA hepatitis B vaccine may be used under similar circumstances in which 2 micrograms of the MSD plasma-derived vaccine was used. Further studies are needed before the other rDNA hepatitis B vaccine may be used in lower than the 10 micrograms dose recommended in children.     

Safety and immunogenicity of a recombinant hepatitis B vaccine

A hepatitis B vaccine produced in yeast by recombinant DNA technology was evaluated using 5-micrograms and 10-micrograms doses in a randomized trial lasting 7 months in 110 male armed forces recruits aged 17-19 years. Results were compared to those of an identical trial of a plasma-derived vaccine. No allergic reactions were observed, and the rate of mild side effects was similar to the plasma-derived vaccine. Seroconversion rates in the first month were 60% (33/55) and 67% (37/55) with the 5-micrograms and 10-micrograms doses of the recombinant vaccine, respectively. All participants seroconverted by 3 months, and none lost antibody. These results are very similar to those for plasma-derived vaccine. Comparison of titres of antibody to hepatitis B surface antigen (anti-HBs) showed a slightly higher level with the 10-micrograms than with the 5-micrograms dose of the recombinant vaccine. Geometric mean titres of anti-HBs after the booster dose were similar in the 5-micrograms and 10-micrograms dose recombinant vaccine groups (2,620 and 2,748 IU/l, respectively) and in the 5-micrograms plasma-derived vaccine group (3,591 IU/l) but significantly higher (9,227 IU/l) with the 10-micrograms dose of the plasma-derived vaccine. These results confirm the safety and immunogenicity of the recombinant vaccine, although further study is needed on the duration of immunity.     

A chemiluminescent, microparticle-membrane capture immunoassay for the detection of antibody to hepatitis B core antigen

A chemiluminescent, microparticle-membrane capture immunoassay (CLIA/MMC) for the detection of antibody to hepatitis B core antigen (anti-HBc) is described. The assay utilizes recombinant hepatitis B core antigen coupled to carboxylated latex microparticles. Human polyclonal IgG anti-HBc labelled with acridinium competes with antibody in the sample for a limited number of binding sites on the solid phase. After a 40 min incubation at 40 degrees C, the reaction mixture is transferred to a glass fiber capture membrane and washed. A chemiluminescent signal is produced by addition of alkaline peroxide and is quantitated on a semi-automated reader as described. The CLIA/MMC assay was compared with standard EIA and RIA procedures (Corzyme and Corab, respectively, Abbott Laboratories, North Chicago, IL). Assay sensitivities were RIA greater than CLIA/MMC greater than EIA. A population of 200 normal blood donors showed nearly identical distributions with the CLIA/MMC and RIA (mean = 11% inhibition, SD = 13% for both), compared with the EIA (mean = 13% inhibition, SD = 15%). With a selected plasma population (n = 307), the CLIA/MMC immunoassay showed an excellent correlation (r = 0.94) with both the EIA and RIA procedures. Association of anti-HBc reactivity near assay cutoffs with antibody to hepatitis B surface antigen suggested relative specificity in the order RIA greater than CLIA/MMC greater than EIA. The CLIA/MMC procedure, which can be readily automated, provides a non-istopic alternative to current EIA testing with performance more nearly equivalent to RIA.     

Verification of the safety, inoculability, reactogenicity and antigenic properties of a live recombinant smallpox-hepatitis B vaccine in an experiment in volunteers

Trials of the first Soviet live recombinant smallpox-hepatitis B vaccine (SHBV) in volunteers (20 men aged 18-20 years) showed its safety, good "take"-rate, and lower reactogenicity as compared with the standard smallpox vaccine (LIVP strain). Smallpox virus-neutralizing antibodies in response to SHBV were produced as well as in response to the smallpox vaccine. Revaccination of human subjects with smallpox vaccine and SHBV 45 days after the previous vaccination resulted in antibody booster to vaccinia virus. After two inoculations of SHBV at an interval of 45 days no anti-HBsAg antibodies were found for 3 months after the last vaccination. However, even a single vaccination with SHBV induced priming to HBsAg. This could be demonstrated after inoculation of the subjects vaccinated with SHBV with one dose of plasma hepatitis vaccine. In the subjects vaccinated with SHBV antibody in response to the plasma vaccine formed more frequently and in higher titres than in those prevaccinated with smallpox vaccine or placebo.     

Characterization of a human monoclonal antibody obtained after immunization with plasma vaccine and a booster with recombinant-DNA hepatitis B vaccine.

A human monoclonal antibody type IgG4, designated 1Ff4, was obtained by Epstein Barr virus transformation of peripheral blood lymphocytes from a hepatitis B vaccinee (HB-VAX: plasma-derived vaccine) after one boost of yeast recombinant DNA derived vaccine (Engerix-B). 1Ff4 binds preferentially to HBsAg/adw(2) and HBsAg/ayw(1). In binding experiments, it competes with antibodies induced by vaccination with HB-VAX-DNA (yeast recombinant) and HB-VAX (plasma-derived vaccine). 1Ff4 competes in part with a monoclonal antibody for the w/r region. Partial inhibition of binding of HBsAg/adw(2) to solid phase anti-HBs was detected, resembling inhibition obtained using other human monoclonal specific for the "a"-loop. 1Ff4 does not bind to linear peptides covering the two "a"-loops or to an adw(2)/G145R mutant, its binding to wild type HBsAg strongly depends on the presence of disulphide bonds. In a large series of HBsAg-positive samples from an endemic area, 1Ff4 antibodies were successfully used to discriminate between an adw(2) and an adrq+ strain. The characterisation of 1Ff4 and other human monoclonal anti-HBs antibodies may help to understand the fine specificity of protective antibodies elicited by immunization.     

Significance of isolated anti-HBc seropositivity by ELISA: implications and the role of radioimmunoassay.

Hepatitis B virus (HBV) surface antigen (HBsAg) and antibody to HBsAg (anti-HBs) are excellent markers for HBV infection and its immunity. The significance of isolated antibody to HBV core antigen (anti-HBc) seropositivity is not certain. To elucidate this, sera from 638 Chinese adult subjects, aged 18-52 years, seronegative for both HBsAg and anti-HBs, were tested for anti-HBc. Fifty-one (8%) were found to have an isolated anti-HBc seropositivity by ELISA, and all were negative for IgM-anti-HBc. The anti-HBc persisted in all subjects who attended follow-up for hepatitis B vaccination (n = 48) for a period of 8 months. These 48 subjects received 3 doses of hepatitis B vaccine (HB-VAX, 10 micrograms or 20 micrograms) at 0, 1, and 6 months: 72.9% developed a primary anti-HBs response (suggestive of a false-positive anti-HBc seropositivity), 4.2% developed an anamnestic or secondary anti-HBs response, and 22.9% did not develop an anti-HBs response. Increasing the cutoff point of the ELISA or reconfirmation with radioimmunoassay (RIA) reduced only a minor half of the false positives. This low specificity of anti-HBc ELISA/RIA, together with the high rate of anti-HBs response to hepatitis B vaccine, indicates that subjects with isolated anti-HBc seropositivity should be included in vaccination programs.     

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.     

Immunoassay of hepatitis b surface antigen by particle counting after pepsin digestion

Particle counting immunoassay is based on latex agglutination, the reaction being measured by instrument counting of the particles remaining unagglutinated. Most interference which generally affects latex agglutination can be avoided by pepsin digestion of the sample, provided the antigen (Ag) of interest resists pepsin, which is the case of the hepatitis B surface antigen (HBsAg). Pepsin treatment has the additional advantage of inactivating antibodies and so releasing the Ag from immune complexes. We have set up an assay of HBsAg, proceeding in a prototype of Impact Instrument (Acade Diagnostic Systems, Belgium) at a rate of 60 samples· h⁻¹ and a total running time of 2 or 4 h. This assay was compared with Abbott radioimmunoassay (RIA) in 706 consecutive patients (A) and 31 selected sera for which values close to the cut-off had been obtained by RIA (B). In A, 38 sera were found positive and 668 negative by both methods. In B, RIA after neutralization classified the samples as positive (n = 14), negative (n = 14), or dubious (n = 3). Complete agreement between latex and RIA was achieved for nine positive, 12 negative, and two dubious samples. Of five RIA-positive samples, two were classified as latex-negative and three as dubious in the latex assay. One sample dubious in RIA was found latex-positive and two RIA-negative samples were found, respectively, latex-positive and dubious; when retested after pepsin digestion, the first of them became RIA-positive. That pepsin is useful to release antigen from immune complexes was also shown by addition of rabbit anti-HBs antibodies to five positive serum samples and by the recovery of the antigen both in RIA and latex agglutination after pepsin digestion.     

Comparative evaluation of the immunogenicity of yeast-derived (recombinant) and plasma-derived hepatitis B vaccine in infants.

The immunogenicity of plasma-derived (HB Vax,MSD) and recombinant hepatitis B virus (Engerix B, SK&F) vaccines was evaluated in infants born to hepatitis B virus carrier mothers. The vaccination was carried out at 1 day, 1 month, and 6 months of age using 10 micrograms of the vaccine given intramuscularly. A total of 83/88 (94.3%) and 74/79 (93.6%) of the infants receiving the plasma-derived vaccine and yeast-derived vaccine showed antibody to hepatitis B surface antigen (anti-HBs). None of the maternal factors studied apart from the HBeAg positivity corellated with vaccine failure. The yeast-derived vaccine gives marginally lower antibody titre than the plasma-derived vaccine. The group-specific anti-"a" antibody was less than 10% of the total anti-HBsAg titre. It was observed that the vaccine alone without prior administration of hepatitis B immunoglobulin is effective in perinatal infection.     

Immune responses to late booster doses of hepatitis B vaccine

Nineteen healthy young adults were vaccinated with plasma-derived hepatitis B vaccine at months 0, 1, and 12, and their immune responses were compared to those of a similar group of 20 vaccinees immunized at months 0, 1, and 6. Late booster injections at 12 months produced nearly fivefold higher geometric mean anti-HBs levels than those of the control group. The higher anti-HBs values may lead to longer persistence of anti-HBs and thus to longer protection against hepatitis B.     

Immune response to HBsAg differently interpreted by RIA and EIA

In the first part of this study anti-HBs developed after vaccination (three different vaccines, sampling at four time intervals after the first injection) or infection (n = 342) was simultaneously tested by Ausab-RIA and Ausab-EIA (Abbot Laboratories). For each vaccination subgroup (vaccine, time) the geometric mean level (GML) of anti-HBs, expressed in IU/l using the Abbott reference panel, was calculated. The ratio GML-RIA/GML-EIA ranged from 1.4 to 2.2. Differences between the vaccine subgroups were found at months 2/3 and month 7, but not at months 12 and 24. The results obtained in convalescent sera by RIA and EIA were similar (ratio GML 1.1). It is concluded that the behaviour of anti-HBs based on the Abbott reference panel differs from that of anti-HBs obtained after vaccination. In the second part of this study, we compared RIA (Abbott Laboratories) with two other EIAs (Organon Teknika): Hepanostika anti-HBs monoclonal (HM) and Hepanostika anti-HBs 'new' (HN). The suitability of these EIAs for detecting anti-HBs greater than 10 IU/l was investigated in sera obtained after vaccination and infection (n = 538). On the first screening, all samples with anti-HBs greater than 10 IU/l (n = 109) in the RIA were detected by HM, whereas 5-7%, dependent on the time of the first incubation step, were negative by HN. The functional sensitivity of HN was 3.9 IU/l (short incubation) or 1.5 IU/l (overnight incubation) and 16.1 IU/l for HM as determined with the Organon reference panel. Sera from three reference panels, as in-house panel, an Abbott panel and an Organon panel were tested in Ausab-RIA, HM and HN. For a serum with the arbitrarily chosen level of 50 IU/l anti-HBs (in-house panel) the results of the in-house panel, the Abbott panel and the Organon panel deviated less by the Ausab-RIA. Since in the Organon-EIAs extreme values of 77 and 35 IU/l were calculated with the Abbott and the Organon panel, respectively, the need for reference sera, the use of which is not related to any particular test system, is stressed once again.     

Comparison of two techniques for detecting antibody to HBsAg during a hepatitis B vaccine study

Two assays for the detection of antibody against hepatitis B surface antigen (anti-HBs) were compared. The first was a direct sandwich radioimmunoassay (RIA) which detects, in principle, antibody against any epitope of hepatitis B surface antigen (HBsAg). The second assay was an inhibition enzyme-linked immunosorbent assay (ELISA). In this assay a fixed amount of HBsAg which can be blocked by anti-HBs is measured in a direct sandwich test. Prevaccination screening sera (n = 191) and follow-up sera obtained from high risk groups (n₁ = 85; n₂ = 41) during two hepatitis B vaccine studies were compared in RIA and ELISA. In prevaccination sera either HBsAg or anti-HBs were detected by ELISA. Full agreement between the results of RIA and ELISA for anti-HBs was obtained in sera containing more than 10 IU/1 anti-HBs. Both tests showed variable results at low titres. Experiments with monoclonal anti-HBs indicated that ELISA is less sensitive for subtype specific antibodies (anti-d, anti-y), which may explain that there were consistent differences between RIA and ELISA in a minority of cases.     

Nine-year follow-up study of a plasma-derived hepatitis B vaccine in a rural African setting

One hundred and one of 255 recipients of a plasma-derived hepatitis B vaccine were evaluated in 1990, 9 years after the first vaccine dose in a study in Zambia to evaluate the efficacy of one, two, or three doses. In 1983, 2 years after the first vaccine dose, antibody to the hepatitis B surface antigen (anti-HBs) had been detectable in 90 of these 101 participants (89%). In 1990, anti-HBs was still detectable in 72 of 101 (71%), and was present at a protective level ( ≥ 10 mlU ml) in 68 of 101 (67%). Although the original vaccine study elicited a protective level of antibody in a greater percentage of children and adolescents than in adults, there were no significant differences among the three groups at 9 years. (In 1990, anti-HBs was still detectable in 52 of 70 [74%] who had had no serologic markers of the hepatitis B virus in 1981, and a protective level was detected in 47 of 70 [67%].) A protective level of anti-HBs was detected in 1990 in 26 of 36 (72%) recipients of three doses and in 23 of 31 (74%) recipients of two doses; the slightly lower prevalence among recipients of one dose (19 of 34 [56%]) was not statistically significant. However, between the years 1983–1990, hepatitis B virus infections had occurred in one of 36 (3%) of those who had been vaccinated with three doses, one of 31 (3%) vaccinated with two doses, and eight of 34 (24%) of those vaccinated with one dose (P < .02 for either two or three doses compared with one dose). These data support the long-term immunogenicity and protective efficacy of a two- or three-dose regimen of the hepatitis B vaccine in a rural African setting. © 1993 Wiley-Liss, Inc.     

The spot-ELISA: a sensitive in vitro method to study the immune response to hepatitis B surface antigen.

We present our experience with a new sensitive in vitro method for the study of the immune response to hepatitis B surface antigen (HBsAg). This immunoenzymatic technique, called spot-ELISA, detects specific immunoglobulin production (e.g. IgG- or IgM-anti-HBs) by stimulated individual B cells in vitro. We have studied the immune response against HBsAg by mitogenic stimulation and subsequent spot-ELISA assay in 24 well-documented subjects with known immune status after either natural infection or vaccination with plasma-derived vaccine. Results indicate a good correlation between in vitro IgG anti-HBs spots and immune 'memory.' A possible predictive value in non-immunized and non-responder subjects awaits further confirmation.     

成人及新生儿乙肝疫苗免疫后15年内表面抗体水平的变化

目的描述和比较北京市15岁及以上人群(以下简称成人)及新生儿乙肝疫苗接种后的15年内抗体水平,为北京市乙肝疫苗接种策略提供参考。方法 2013年8月至2014年2月采用多阶段整群随机抽样方法在北京市1岁以上人群中抽取6 705人进行乙肝血清学流行病学调查,选择其中完成3针基因重组乙肝疫苗接种且没有进行加强免疫的成人和新生儿为研究对象,描述和比较成人和新生儿接种乙肝疫苗后15年抗-HBs阳性率和抗-HBs滴度变化。结果共纳入符合入组标准的新生儿和成人分别为463和129人。基于中国目前15~59岁人群自限性感染率估计为30%,成人接种后0~4、5~9和10~15年的抗-HBs阳性率仍可分别保持在58.6%、62.5%和48.4%,呈现平稳下降的趋势;对应的抗-HBs滴度中位数分别为288.8、120.6和62.6 m IU/m L。新生儿接种人群3个时间段的抗-HBs阳性率分别为83.3%、47.3%和43.5%;抗-HBs滴度中位数分别为71.8、8.9和6.7 m IU/m L;成人接种乙肝疫苗后5~15年的抗-HBs滴度及阳性率均高于新生儿。结论成人和新生儿接种乙肝疫苗15年内可获得良好的保护。     

Antibody detection and kinetics of antibody production during early stages of immunization with hepatitis B virus vaccine

Antibodies to influenza virus and human immunodeficiency virus are detectable in B cells during the early stages of the immune response, prior to their occurrence in plasma. To investigate similar phenomena in a model of immunization against hepatitis B virus (HBV) infection, medical students in Ghana were screened for HBV markers, HBV surface (HBs) antigen (HBsAg), and HBV core antibodies (anti-HBc). Consenting volunteers, 24 of whom were seronegative (susceptible) and 2 of whom were positive for anti-HBc (prior infection), were vaccinated on day 0, day 40, and 6 months. Two sets of 10 blood samples, sequentially collected at intervals of 2 days following each immunization on days 0 and 40, were processed into B-cell lysates and plasma. Solid-phase HBsAg coated on microtiter plates for enzyme immunoassay or nitrocellulose membranes for dot blot assay was used to detect anti-HBs activity by an indirect antiglobulin assay. A commercially procured sandwich immunoassay was used, along with an enzyme-linked immunosorbent assay and a dot blot assay, for the detection of anti-HBs in B-cell lysates and plasma. Following the first injection of vaccine, a single sample of B-cell lysate collected between 5 and 21 days revealed anti-HBs in 18/21 subjects with no plasma antibodies detectable by sandwich immunoassay. After the booster dose was injected on day 40, a single sample of B-cell lysate collected between 44 and 49 days showed anti-HBs in 16/19 subjects, and this was accompanied by plasma antibodies in 8 subjects. In contrast, between 8 and 13 days, both subjects with prior HBV infection showed anti-HBs in B-cell lysates and plasma. Thus, primary immunization with the HBV vaccine appears to transiently elicit low-affinity anti-HBs in B-cell lysates into plasma.     

Antibody responses of adults, adolescents, and children to a plasma-derived hepatitis B vaccine in a rural African setting

A field trial of a plasma-derived hepatitis B vaccine in five rural villages in Zambia was analyzed to determine if adults in a rural African setting respond to this vaccine as well as adults in Western countries and to determine the immunogenicity of fewer than the recommended three doses; 255 residents, including 171 who were susceptible to hepatitis B, were vaccinated. Among those who received three vaccine doses, protective levels of antibody to hepatitis B surface antigen (anti-HBs) developed in 67% of adults (ages 21 to 70 years), 87% of adolescents (ages 12 to 19 years), and 100% of children (ages 0 to 11 years). The 67% of vaccinated adults who developed anti-HBs at the protective level was lower than the 96% reported among adults receiving the same vaccine at the same dose and dosage schedule in studies in Western countries. No difference was seen in the response of those receiving two doses compared with those receiving three doses among adults and adolescents, suggesting that a two-dose regimen may be acceptable in these age groups in developing countries to reduce costs and improve compliance. Use of hepatitis B vaccine in a region where prevaccination hepatitis B serologic screening was not available did not appear to increase the number of severity of adverse reactions.