Dissociated antibody responses to the S and pre-S2 regions of the hepatitis B virus after vaccination in hemophiliacs

The membranes of hepatocytes and the pre-S2 envelope protein of the hepatitis B virus (HBV) contain binding sites for polymerized human albumin, which is thought to act as a link between HBV and hepatocytes. Hence, anti-pre-S2 antibodies should prevent HBV uptake by the liver, and there is indeed preliminary evidence that they protect chimpanzees from HBV infection. To evaluate whether a plasma-derived vaccine containing the pre-S2 sequence induced an anti-pre-S2 response in 105 vaccinated hemophiliacs, anti-pre-S2 was measured in parallel with antibody to hepatitis B surface antigen (anti-HBs). Eighty-five percent of the hemophiliacs had both anti-pre-S2 and anti-HBs when vaccination was completed, 13% had anti-HBs alone, and 2% (two cases) had anti-pre-S2 alone. Eighty-seven percent of anti-pre-S2-positive hemophiliacs compared with only 50% of anti-pre-S2-negative hemophiliacs (P less than 0.001) developed high anti-HBs titers (greater than or equal to 1,000 mlU/ml). This study demonstrates, therefore, that the antibody responses to the S and pre-S2 regions of HBV may be dissociated after vaccination in hemophiliacs and that higher anti-HBs titers are attained in anti-pre-S2-positive hemophiliacs.     

Trend of hepatitis B virus infection in freshmen classes at two high schools in Hualien,Taiwan from 1991 to 1999

Taiwan is an endemic area of hepatitis B virus (HBV) infection. A nationwide mass vaccination program to prevent HBV infection was started in 1985. Perinatal and horizontal transmission of HBV decreased substantially after the launching of this program. However, the influence of this program on children born before 1985 has not been studied. From 1991 to 1999, annual surveys of hepatitis B virus surface antigen (HBsAg) and antibody (anti-HBs) were carried out in freshmen at two high schools in Hualien, Taiwan. The average age was 16 years old. Although these students were born 2-10 years after the start of the national HBV vaccination program, there is a significant trend of decreasing HBsAg carrier rate (from 21.0% to 10.5% in males and 14.3% to 4.7% in females) and increasing anti-HBs rate (from 56.6% to 67.8% in males and 70.3% to 75.9% in females) over the 9 years. With yearly comparison, the carrier rate of HBsAg started to show significant decrease since 1994, while the anti-HBs began to rise significantly after 1996, especially in male students. The HBsAg carrier rate in male students was significantly higher, while the anti-HBs rate was significantly lower, than that in female students in most of the years. It is concluded that the effect of HBV vaccination also reduced horizontal transmission of HBV to children born up to 7 years before the start of the program.     

Acute hepatitis B viral infection in a patient with anti-HBs.

We report a patient with antibody to hepatitis B surface antigen (anti-HBs) but no antibodies to other hepatitis B virus components, who developed acute symptomatic type B hepatitis. The possible explanations for this unusual serological pattern are 1) the antibody-positive status, which developed against only a subdeterminant of hepatitis B surface antigen (HBsAg), arose naturally or as the result of cross-reaction with a variety of antigens; and 2) seroconversion to anti-HBs occurred in response to surface antigen of a mutant strain of hepatitis B virus (HBV). This anti-HBs positivity, in the absence of antibody to hepatitis B core antigen, does not provide natural immunization against HBV infection, and so is not protective. Individuals who are positive to anti-HBs antibody alone which is not elicited by HBV vaccine, should be vaccinated against possible HBV infection.     

Permanent loss of anti-HBc after reactivation of hepatitis B virus infection in an anti-HBs and anti-HBc-positive patient after allogeneic stem cell transplantation.

BACKGROUND: Reactivation of a hepatitis B virus (HBV) infection after transplantation is associated with a high morbidity and mortality. HBV infections generally result in anti-HBc persisting lifelong. CASE REPORT: A 44-year-old female presented 10 years after allogeneic stem cell transplantation with a chronic hepatitis B. The infection was reactivated from a resolved (anti-HBs and anti-HBc positive) HBV infection acquired some years prior to transplantation. Interestingly, she lost all antibodies to HBV including anti-HBc and is upto now anti-HBc negative. The sequence of the surface and the core gene did not reveal any escape mutations. Thus, the loss of anti-HBc might suggest an immunotolerance of the donor's immune system against HBcAg. CONCLUSION: This data illustrate that an HBV infection might be reactivated despite high anti-HBs levels prior to transplantation. Furthermore, this is the first patient in which a complete loss of anti-HBc could be documented. Moreover, since anti-HBc is often used as a screening marker for HBV it should be kept in mind that anti-HBc negative patients with high viremic HBV infection may occur.     

Reactivation of an occult hepatitis B virus escape mutant in an anti-HBs positive, anti-HBc negative lymphoma patient.

BACKGROUND: Hepatitis B virus (HBV) often persists after resolution, but its replication is suppressed by antiviral T cells. Immunosuppressive treatment may lead to viral reactivation and severe hepatitis. Early antiviral therapy prevents reactivation but some occult HBV infections are not easily detectable. RESULTS: Here we describe a patient with a progressive non-Hodgkin lymphoma who had probably not been vaccinated against HBV and, before immunosuppression, showed antibodies (anti-HBs) against the viral surface antigen (HBsAg) as the only possible marker of occult HBV infection. Under immunosuppression he developed viremia (>10(8)copies/mL). The virus exhibited three S gene mutations (L109R, C137W, G145R) which led to false negative HBsAg results and diminished binding of vaccine-induced anti-HBs. CONCLUSIONS: Reliable screening and monitoring of severely immunosuppressed patients for HBV should include, in addition to anti-HBc and HBsAg, anti-HBs and sensitive HBV DNA assays. Furthermore, active vaccination or hepatitis B immune globulin may not protect against such mutants.     

Seroprevalence and risk factors for hepatitis B infection in an adult population in Northeast China

Background and aim: The prevalence of the hepatitis B virus (HBV) is higher in adults than in children. We determined the seroepidemiology of HBV infection in an adult population in JiLin, China, to guide effective preventive measures.Methods: A cross-sectional serosurvey was conducted throughout JiLin, China. A total of 3833 people was selected and demographic and behavioral information gathered. Serum samples were tested for HBV markers and liver enzymes.Results: The prevalence of the hepatitis B surface antigen (HBsAg), the antibody to the hepatitis B surface antigen (anti-HBs), the hepatitis B e antigen (HBeAg), the antibody to HBeAg (anti-HBe), and the antibody to the hepatitis B core antigen (anti-HBc) were 4.38%, 35.66%, 1.38%, 6.65%, and 40.88%, respectively. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly higher among HBsAg (+) than HBsAg (-) subjects. By multivariate logistic regression analysis, independent predictors for chronic HBV infection were smoking, poor sleep quality; occupation as private small-businessmen, laborers, or peasants; male gender; family history of HBV; personal history of vaccination; and older age. Independent predictors for exposure to HBV were large family size, occupation as a private small-businessman, male gender, family history of HBV, personal history of vaccination, and older age. Independent predictors for immunity by vaccination were occupation as a private small-businessman, high income, personal history of vaccination, and young age. Independent predictors for immunity by exposure were drinking, male gender, personal history of vaccination, and older age.Conclusions: The prevalence rate of HBV infection (4.38%) was lower than the previous rate of general HBV vaccination. However, 44.59% of the population remained susceptible to HBV. The prevalence of HBV infection was high in young adults, private small-businessmen, peasants, those with a family history of HBV, and males. Therefore, immunization of the non-immune population is reasonable to reduce hepatitis B transmission between adults.     

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.     

The isolated presence of anti-HBc antibodies: prevalence and interpretation based on the results of viral DNA research and anti-HBs antibodies measurement after vaccination

In order to study the significance of the isolated presence of anti-HBc antibodies, we have looked for the 3 classic serological markers of the hepatitis B (HBs antigen, anti-HBs and anti-HBc antibodies) in 1,586 hospital agents who are to vaccinate in the framework of a campaign of systematic vaccination of the hospital personnel of university hospitals of Sfax for a period of 18 months. We identified subjects who presented isolated anti-HBc antibodies (33 individuals = 2.08%). In these subjects'serum, we performed a research of the DNA of hepatitis B virus (HBV) with a PCR hybridization technique using a couple of primers. One week after administration of a vaccine dose, we also measured anti-HBs antibodies in their sera. Among the tested 18 personnel with anti-HBc isolated antibodies, 11.1% had low rates of anti-HBs antibodies indicating that there is presumably primary antibody response and therefore a false positivity of anti-HBc antibodies in pre-vaccinal serology; while 11.1% others had higher rates of anti-HBs antibodies corresponding to a secondary antibody response, which witness a previous HBV immunisation. The research of the HBV-DNA was positive in 11.1% of tested personnel, testifying a presumably chronic portage of the virus with low rates of the HBs antigen undetectable with the serological techniques. For the remainder subjects with isolated anti-HBc antibodies (66.7%), the interpretation remains ambiguous.     

HBV and HCV infection in Japanese dental care workers

Protective measures against occupational exposure to the hepatitis B virus (HBV) and hepatitis C virus (HCV) must be taken in order to prevent infection in dental care workers. To determine the best way to protect these workers, our study examined viral hepatitis infection in dental care workers in regions with a high prevalence of HCV infections in Japan. In total, 141 dental care workers (including dentists, dental hygienists and dental assistants) were enrolled. After a questionnaire to elicit demographic information was administered by an oral surgeon, hepatitis B surface antigen (HBsAg), antibody to HBs (anti-HBs), antibody to hepatitis B core antigen (anti-HBc) and antibody to HCV (anti-HCV) were measured. When necessary, HBeAg, anti-HBe, levels of HBV DNA, anti-HBc IgM and HCV RNA in serum were measured. Of the dental care workers included, 68 (48.2%) had been immunized with a HBV vaccine. Only 9 wore a new pair of gloves for each new patient being treated, 36 changed to a new pair only after the old gloves were torn and 24 did not wear any gloves at all. No one was positive for HBsAg or anti-HCV, though 73 (51.8%) and 17 (12.1%) workers were respectively positive for anti-HBs and anti-HBc. The positive rate of anti-HBc varied directly with worker age and experience. Of the 68 workers immunized with HBV vaccine, 51 (75%) were positive for anti-HBs. Of the 63 workers who were not so immunized, 17 (27%) were positive for anti-HBs and 15 of these were also positive for anti-HBc. Immunized workers were more protected against HBV infection than non-immunized workers, indicating that HBV vaccine was a useful measure for protection against the infection. The anti-HBc positive rate was significantly higher among dental care workers than general blood donors, suggesting that frequency of exposure to HBV was greater in dental care workers. HBV vaccination should be made compulsory for all dental care workers who handle sharp instruments.     

Failure of preexisting antibody against hepatitis B surface antigen to prevent subsequent hepatitis B infection.

We studied a patient who developed acute hepatitis B virus (HBV) infection despite the presence of preexisting antibody to the surface antigen of HBV (anti-HBs). Anti-HBs has been reported to consist primarily of antibody against the common a determinant of HBV. Antibody directed against this major determinant appears to confer protection against HBV, regardless of the subtype. Our patient was shown to have had preexisting anti-HBs of anti-d but not anti-a specificity. She subsequently developed non-A, non-B viral hepatitis followed by an episode of acute hepatitis B after exposure to HBV of the ayw subtype.     

Low rates of active hepatitis B and C infections among adults and children living with HIV and taking antiretroviral therapy: A multicenter screening study in Lesotho

Lesotho presents the second-highest adult human immunodeficiency virus (HIV) prevalence globally. Among people living with HIV, data on hepatitis B virus (HBV) or hepatitis C virus (HCV) coinfection are limited. We report HBV and HCV coinfection data from a multicentre cross-sectional study among adult and pediatric patients taking antiretroviral therapy in 10 health facilities in Lesotho. Among 1318 adults screened (68% female; median age, 44 years), 262 (20%) had immunologically controlled HBV infection, 99 (7.6%) tested anti-HBs positive and anti-HBc negative, indicating vaccination, and 57 (4.3%) had chronic HBV infection. Among the patients with chronic HBV infection, 15 tested hepatitis B envelope antigen (HBeAg) positive and eight had detectable HBV viremia (median, 2 477 400 copies/mL; interquartile range, 205-34 400 000) with a mean aspartate aminotransferase-to-platelet ratio index of 0.48 (SD, 0.40). Prevalence of HCV coinfection was 1.7% (22 of 1318), and only one patient had detectable HCV viremia. Among 162 pediatric patients screened, three (1.9%) had chronic HBV infection, whereby two also tested HBeAg-positive, and one had detectable HBV viral load (210 copies/mL). Six of 162 (3.7%) had anti-HCV antibodies, all with undetectable HCV viral loads. Overall prevalence of chronic HBV/HIV and HCV/HIV coinfection among adults and children was relatively low, comparable to earlier reports from the same region. But prevalence of immunologically controlled HBV infection among adults was high. Of those patients with chronic HBV infection, a minority had detectable HBV-DNA.     

IgG subclass composition of antibodies to HBsAg in circulating immune complexes from patients with hepatitis B virus infections

The IgG subclass of antibody associated with hepatitis B surface antigen (HBsAg) in circulating immune complexes (CIC) from patients with either acute or chronic hepatitis B virus (HBV) infections was measured using an isotype and antigen-specific ELISA. All patients were HBsAg positive but were negative for free anti-HBs antibody. The subclass of antibody associated with HBsAg in CIC in both groups was predominantly IgG1 and IgG4. This is in contrast to free anti-HBs in convalescent sera from patients recovering from HBV infection, which are highly restricted to IgG1 and IgG3. The finding of high levels of IgG4 antibodies in CIC suggest that CIC containing this subclass may be cleared less efficiently than CIC containing antibodies of other subclasses. Formation of these CIC may be an important factor in the progression of infection to chronicity and may also be involved in the antigen-specific immunosuppression seen in early acute and chronic HBV infections.     

Prevalence of anti-HBc in anti-HBs positive individuals: implications for selecting vaccine candidates

Two serologic markers, anti-HBs, -HBc, are useful to determine whether individuals at risk for hepatitis B virus infection are candidates for hepatitis B vaccination. To evaluate the usefulness of these markers in detecting immunity from prior infection (usually asymptomatic), 192 anti-HBs positive health care workers were tested for anti-HBc. In the 68% of individuals with anti-HBs RIA ratios greater than 10, anti-HBc was found in only 75%. In the group with anti-HBs ratios less than 10, only 6.6% had anti-HBc. Health care workers with frequent contact with blood and other body fluids were more likely to have both markers present. The incidence of the markers in this group was similar to that observed in 520 homosexually active males. The authors conclude that anti-HBs is more likely to identify prior immunity, particularly in individuals with infrequent HBV exposures.     

Significance of "anti HBC alone" serological profile in 284 patients suspicious of being infected with hepatitis B virus

The "anti-HBc alone" serological profile is a frequent finding in hepatitis B virus infections, but little is known about its clinical significance. The aim of this study was to explore the 'anti-HBc alone' serological profile obtained by immunosorbent assay (ELISA) in 284 patients suspicious of being infected with hepatitis B virus. Sera were screened for following serological markers: HBs Ag, anti-HBc and anti-HBs antibodies using immunoradiometric assay (IRMA) and for HBV DNA using polymerase chain reaction. Among 284 studied sera with 'anti-HBc alone' serological profile, 124 were positives for anti-HBs antibodies by IRMA and corresponding to a recovered form of hepatitis B. Nineteen sera were negatives for anti-HBc antibodies, suggesting false positive results by ELISA. Two sera were found positives for HBs Ag by IRMA, which are related to authentic hepatitis B. HBV DNA was positive in 4 sera, suggesting occult hepatitis B. This study indicates that "anti-HBc alone" serological profile is most often correlates with recovered hepatitis B infection, but it can mask an occult hepatitis B.     

Lack of genetic restriction by a potential anti-idiotype vaccine for type B viral hepatitis

Anti-idiotype (anti-Id) reagents that bear an internal image capable of mimicking hepatitis B surface antigen (HBsAg) were used to induce an antibody to HBsAg (anti-HBs) response in both rabbits and chimpanzees. The anti-idiotype induced antibody response produced in rabbits recognized HBsAg determinants associated with the induction of protective immunity against hepatitis B virus (HBV). Attesting further to the specificity was the binding of the rabbit anti-idiotype to the anti-idiotype induced anti-HBs containing sera. Our findings suggest that genetic restrictions associated with the induction of an interspecies immune response may not be a limitation of anti-idiotype based vaccines. In addition, anti-idiotype immunization also produced an anti-HBs in chimpanzees, a species susceptible to infection with human HBV. These data demonstrate that internal-image-bearing anti-idiotype reagents can induce an immune response across species barriers. Additionally, the reagents represent a viable alternative approach to vaccination against agents such as hepatitis B virus that cause human disease.     

Neutralization of hepatitis B virus infectivity by a murine monoclonal antibody: an experimental study in the chimpanzee

Two study chimpanzees were inoculated intravenously with approximately 1,000 chimpanzee infectious doses of hepatitis B virus (HBV), one with subtype adr and one with subtype ayw, each previously incubated with 0.1 ml of a murine monoclonal antibody (IgG 1(K) class) directed against a single epitope on hepatitis B surface antigen common to most or all HBV. Two control chimpanzees received identical doses of HBV not incubated with the murine anti-HBs. Neither study chimpanzee developed HBV infection during 12 months of follow-up as judged by normal serum aminotransferase activity, normal liver biopsies, and negative serological tests for HBV-associated antigens and antibodies. In contrast, both control chimpanzees became infected by HBV as evidenced by elevated serum aminotransferase activity, liver biopsy changes characteristic of viral hepatitis, and the appearance of hepatitis B surface antigen (HBsAg) in their sera. Both study chimpanzees were shown to be fully susceptible to infection with these same HBV inocula when challenged 15 months after the initial inoculations at a time when passively administered anti-HBs was no longer detectable. Prior to challenge with HBV, one of the two study chimpanzees received a second injection of the same volume of the murine monoclonal anti-HBs. The survival of this anti-HBs in serum was reduced from six weeks (after the initial injection) to approximately two weeks.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of Immune Response to Hepatitis B Vaccine in Healthcare Workers at a Tertiary Care Hospital

Purpose: Healthcare workers (HCWs) are at high risk of acquiring hepatitis B virus (HBV) infection through occupational exposure which is preventable through hepatitis B vaccination. In the current study, the response to HBV surface antigen (HBsAg) vaccine was assessed in a selected group of HCWs by testing for antibodies against HBsAg (anti-HBs). Methods: Blood samples were collected in all HCWs, who have received the complete schedule of hepatitis B vaccination and anti-HBs levels, were assessed quantitatively in sera using ELISA. Results: The age range of the study participants was 20–55 years. The mean months after the last dose of vaccination were 60.36. Among the 85 participants, 96.5% (n = 82) have protective immunity to hepatitis B. The anti-Hbs response was similar in both male and female (P > 0.05). There was a decline in immune response as the age was increasing (P < 0.05). The results of the study found a significant decline in the immune response with time (P < 0.05). The anti-Hbs response was declined with smoking habit (P < 0.05) and with increasing body mass index (P < 0.05). Conclusion: Post-HBsAg vaccination immunity to hepatitis B was 96.5% in HCW and was similar to that of global rates. Increasing age, time period, smoking habit, and overweight were associated with decreased immunity. Many studies are needed in developing newer HBV vaccines with very high immunogenicity. Giving highly immunogenic vaccine to HCWs will ensure safety at work by reducing nosocomial transmission which is very much desired in a resource-limited country.     

Regulation of the neutralizing anti-hepatitis B surface (HBs) antibody response in vitro in HBs vaccine recipients and patients with acute or chronic hepatitis B virus (HBV) infection

Antibodies directed to the HBs antigen indicate viral clearance and the development of life-long immunity in patients that recovered from HBV infection. In HBs antigen vaccine recipients anti-HBs antibodies provide protective immunity. However, little is known about the regulation of this HBs-specific antibody response. The existence of anti-HBs-secreting B cells was demonstrated using the highly sensitive ELISPOT technique compared with conventional ELISA in serum and cell culture supernatants. In the peripheral blood of patients with acute self-limited hepatitis B, HBs-specific B cells were demonstrated with a high frequency despite undetectable anti-HBs serum antibodies. HBV-immunized patients that had recovered from infection and vaccine recipients had significantly lower frequencies, whereas chronic HBV carriers and negative controls showed no anti-HBs-secreting B cells. Coculture experiments of isolated B and T cells revealed that the anti-HBs antibody response was restricted to the presence of T helper cells, but not to identical HLA class II molecules. Allogeneic T cells derived from vaccine recipients or chronic HBV carriers stimulated the HBs-specific B cell response in HBs vaccine recipients. Otherwise, isolated T helper cells could never provide sufficient help to induce the HBs-specific B cell response in chronic HBV carriers. Furthermore, peripheral blood mononuclear cells (PBMC) of six out of 10 vaccine recipients, one out of five HBV-immunized patients, but of no chronic HBV carrier showed a proliferative response to different HBs antigen preparations. This study demonstrated a high frequency of circulating anti-HBs-producing B cells in the early phase of acute HBV infection, but a lower frequency of HBs-specific B cells years after resolution of HBV infection. In chronic HBV carriers, however, deficient HBs-specific T and B cell responses were observed.     

Lack of immunity to hepatitis B virus among the expatriates residing in southern Taiwan

Taiwan is an endemic area for hepatitis B virus (HBV) infection. There are more than 3-million carriers on this island. Chronic HBV infections may result in liver cirrhosis and hepatocellular carcinoma, which are common in Taiwan. However little information is available concerning the immunity and the susceptibility to HBV among the expatriate-population (non-permanent residents from foreign countries) in Taiwan. Thus controversies exist on the indications for HBV vaccination among the foreign visitors and expatriates. This study evaluated the serological status of those who attended the Kaohsiung Adventist Clinic between May 1986 and August 1989. Hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) were determined by ELISA. A total of 152 expatriates (85M, 67F, aged 5 to 64 years, duration of residence in Taiwan: 2 weeks to 11 years) without previous HBV vaccination, were tested. HBsAg and anti-HBs were not detected in 125 (82%). Anti-HBs was found in 22 (15%). There was no correlation between the duration of residence and anti-HBs positivity. However, there was an increased prevalence of anti-HBs with increasing age after 30. For those expatriates who were anti-HBs positive, 64% had a history of sexual contact with a partner from an endemic area of HBV. HBsAg was detected in 5 (3%). Three were symptomatic with abnormal liver function tests. Four had a history of sexual exposure. Their children were not antigenemic. It is concluded that most (greater than 82%) of the expatriates residing in southern Taiwan have no immunity to HBV and sexual contact is a major route (70%) of transmission.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunogenicity in chimpanzees of experimental hepatitis B vaccines prepared from intact hepatitis B virus,purified polypeptides,or polypeptide micelles

The immunogenicity of three experimental hepatitis B vaccines was evaluated in chimpanzees. Although no antibody to hepatitis B surface antigen (anti-HBs) was detected in two chimpanzees that received an aqueous polypeptide vaccine subcutaneously, a strong anti-HBs response was observed two and ten weeks, respectively, following challenge with hepatitis B virus. Inoculation of two additional chimpanzees with a micellar preparation of these polypeptides by the intravenous route resulted in anti-HBs production in one of the chimpanzees. Two chimpanzees inoculated subcutaneously with an aqueous vaccine of formalin-inactivated intact hepatitis B virus developed anti-HBs in low titers, but the development of antibody to the hepatitis B core antigen following challenge inoculations suggested that subclinical HBV infections may have occurred despite prior vaccination.