Regulation of the human immune response to HBsAg: effects of antibodies and antigen conformation in the stimulation of helper T cells by HBsAg

Immunization against hepatitis B virus by mucosal administration of antigen-antibody complexes

Antigen-antibody complexes have been shown to enhance immune responses against several antigens given by parenteral immunization. Herein, we have evaluated the potential of administering such immunostimulatory complexes by a mucosal route. Hepatitis B surface antigen (HBsAg) complexed with antibodies against HBsAg (anti-HBs) (HBsAg/Ab) was administered to BALB/c mice by intranasal inhalation. HBsAg by itself did not induce immune responses, whereas with HBsAg/Ab complexes, both systemic and mucosal immune responses were observed and these could be modulated by adjuvants. With HBsAg/Ab (1 or 10 microg), anti-HBs antibodies induced were predominantly of the IgG1 isotype (Th2-like). In contrast, anti-HBs induced by HBsAg/Ab plus cholera toxin (CT) or oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs (CpG) (1 microg each) were predominantly IgG2a (Th1-like). Results from this study indicate that HBsAg/Ab complexes can induce strong humoral immune responses when delivered by a noninvasive route, whether used alone or in combination with other mucosal adjuvants.

Cytolytic response to HIV in patients with HIV disease treated with extracorporeal photochemotherapy: preliminary study

Extracorporeal photochemotherapy (photopheresis), an immunomodulatory therapy that targets circulating T helper lymphocytes, has been applied to the management of human immunodeficiency virus (HIV) disease. Any therapy that exerts its actions on CD4+ T cells has the potential of exacerbating HIV infection. Therefore, it was necessary to observe immune function during treatment. Because cytotoxic T lymphocytes (CTL) and natural-killer cells are thought to play an important role in the response against HIV infection, we examined the effect of photopheresis on HIV cytolytic activity. The study group consisted of seven patients with late-stage HIV disease who had not received any previous treatment for HIV infection. Patients were treated exclusively with photopheresis on two consecutive days each month for 14-32 months (average, 25 months). Peripheral lymphocytes, collected at various points during treatment, were used as effectors in a 51Cr release assay. Epstein-Barr virus (EBV)-transformed autologous B cell lines transfected with recombinant vaccinia vectors that expressed the HIV env (gp120, gp41) and gag (p24) proteins were used as target cells. All seven patients demonstrated relatively constant levels of cytolysis (>10% above controls) during treatment in the context of stable CD4+ T cell counts and a stable clinical status. These results suggest that extracorporeal photochemotherapy did not impair the cytolytic response to HIV infection and may have enhanced it in some patients.

Immune response to hepatitis A virus capsid proteins after infection

This study was undertaken to determine the immune response of humans to viral capsid polypeptides of hepatitis A virus (HAV) after natural infection, which is very important for vaccine development. Antiviral capsids in 73 serum samples from patients with acute and chronic HAV infections were analyzed by immunoblotting against individual HAV capsid polypeptides (VP1, VP2, VP3, and VP4) by using a cell culture-based HAV antigen. For reference, total anti-HAV immunoglobulin G (IgG) and anti-HAV IgM were also determined by radioimmunoassay. As a result, a dominant immune response against VP1 (98% IgG, 94% IgM) was found in the acute phase. However, many other sera also reacted with VP0 (88% IgG; 35% IgM) and VP3 (81% IgG and 29% IgM). In contrast to the acute phase, anti-VP1, anti-VP0, and anti-VP3, IgG antibodies against all three viral proteins (29, 29, and 73% respectively), especially those against VP3, were found years after onset of HAV disease and over long periods in the sera of hepatitis patients. These results suggest that antibodies for capsid polypeptides are present over an extended period in the sera of HAV-infected patients. They are likely of importance in maintaining long-term immunity.

Anti-HBs kinetics after HBV vaccination in neonates

BACKGROUND AND OBJECTIVES

We report the results of a study using a recombinant DNA HBV vaccine in newborns from an endemic area for HBV and compare the anti-HBs kinetics with observations in adults in order to make estimates about the need for booster vaccinations.

STUDY DESIGN

One hundred and forty-eight neonates were vaccinated and followed for 62 months. Based on the presence or absence of hepatitis B surface antigen in the mother, cohorts of 'exposed' and of 'non-exposed' neonates were identified.

RESULTS

A maximum concentration is normally observed after the booster vaccination followed by a rapid decline. According to Ambrosch et al. and Gesemann et al., titer calculations as a function of time, yielded 37 IU/1 and 47 IU/1 at month 60 respectively. The mean titer for the three groups of neonates investigated was at that time 74 IU/1. The prospective time intervals to arrive at an anti-HBs level of at least 10 IU/1 can be individually calculated from the individual titer after the booster vaccination. These calculated estimates show respectively: that 8.3% of the vaccinated neonates need a new booster vaccination within 14 months; that 26.7% will need a new booster within 50 months; and that only 65% need a new booster in 50 or more months.

CONCLUSION

It can be concluded that anti-HBs kinetics in very young children and adults are comparable. The least expensive way of maintaining protection against HBV in neonates seems to be the determination of the individual titers after the first booster vaccination and calculation of the prospective time interval to arrive at a minimum titer of 10 IU/1 and the need for a new booster vaccination.

A self-associating hepatitis B surface antigen-derived peptide that is immunogenic in alum

We previously described an oligomeric synthetic peptide derived from the hepatitis B surface antigen that displayed a limited tendency to form self-associating macromolecular structures in solution. Here it is demonstrated that amino-terminal myristylation of this peptide results in near quantitative aggregation of the oligomeric peptide. The myristylated peptide is highly immunogenic when used in conjunction with alum as adjuvant in both the rabbit and rhesus monkey models. The antibody response generated by peptide also cross-reacted with native antigen and was long-lasting. Collectively the results described in this and previous reports offer an attractive new approach for generating immunogenic peptide mimetics of conformational epitopes that may find application as vaccines.

Comparison of immune responses to a native viral antigen and a synthetic peptide derived from it: implications for vaccine development

Murine immune responses to the hepatitis B surface antigen (HBsAg) and a synthetic peptide derived from it were compared at the humoral level. Six of nine strains used responded to either peptide or HBsAg, though restriction profiles were not superimposable. Two of three strains non-responsive to HBsAg produced an antibody response on immunization with peptide which was cross-reactive with both peptide and HBsAg. In in vitro lymphocyte stimulation assays, lymphocyte from all six peptide-immunized mouse strains could be induced to proliferate on challenge with HBsAg. However, of the HBsAg-immunized groups, lymphocytes from only three of six responder strains proliferated on in vitro HBsAg challenge. Cumulatively, these results suggest that a vaccine formulation that includes both protein antigens and synthetic peptides derived from these proteins may be more effective at eliciting an immune response in a broader cross-section of target population.

Viral-specific immunization in AIDS-related complex by photopheresis

The potential for therapeutic intervention in 7 patients with AIDS-related complex (ARC) was evaluated through the use of photopheresis. The rationale for the study was based on: 1. the demonstration that psoralen and UVA could inactivate HIV/virus in vitro; 2. CD4 cells are the primary target population effected by HIV and photopheresis; and 3. reinfusion of inactivated virus and cell-associated virus might serve to engender an immune response. Preliminary results in 7 patients with ARC over 6 to 18 months revealed a virus-specific response with an elevation of HIV antibodies, while EBV and CMV titers remained unchanged. The immunologic results revealed an increase in the CD8 lymphocyte population, stable activation markers (B2 microglobulin neopterin), a decrease in p24 antigen titers and inability to culture HIV virus in 3 patients. All of these results were in the context of a stable or increasing CD4+ percent. Six patients did not reveal a generalized inhibition of other immune responses as demonstrated by recovery of DTH. In addition, the resolution of lymphadenopathy, night sweats, fever and weight loss, paralleled the immunologic response.

Immunology of hepatitis B virus infections

Acute or chronic hepatitis B virus infection is often associated with symptoms which are probably caused by immune complexes, such as vasculitis, glomerulonephritis and arthritis. The immune complexes found in such patients contain excessive viral proteins. The functions of these proteins and the immune response to them during various states of infection are discussed.

Lack of immune potentiation by complexing HBsAg in a heat-inactivated hepatitis B vaccine with antibody in hepatitis B immunoglobulin

In a randomized, dose-response study among 305 health care workers, we examined whether the immunogenicity of a heat-inactivated hepatitis B vaccine could be enhanced when HBsAg was complexed by anti-HBs contained in hepatitis B immunoglobulin either at equivalent proportions or at 10-fold antigen excess. The dose of HBsAg in the control vaccine as well as in the two complexed vaccine preparations could be reduced from the standard value (3 micrograms) to 0.6 micrograms per injection without affecting the antibody response in the vaccinees. Still lower dosages of HBsAg in the three vaccine preparations induced significantly lower but comparable anti-HBs responses. These results indicate that, in man, using a heat-inactivated plasma vaccine, addition of anti-HBs contained in hepatitis B immunoglobulin does not potentiate the immunogenicity of HBsAg.

Cellular immune response to hepatitis B virus antigens. An overview

It has been suggested that the cellular immune response to HBV antigens is responsible for hepatocellular injury in acute and chronic hepatitis B. However, definitive immunological studies have so far been hampered by the lack of appropriate model systems to study HBV antigen-specific T cells. The availability of highly purified and recombinant HBV antigens and of experimental techniques to maintain in continuous growth antigen-specific T cells derived not only from the peripheral blood but also from the liver should allow a better understanding of the fine immunopathogenetical mechanisms involved in viral clearance and liver damage. Whether some important biological characteristics of HBV antigens described in the mouse system, such as the high immunogenicity of the pre-S antigens and the capacity of the nucleocapsid of HBV to be a T cell-dependent and -independent antigen, are relevant to the immunopathogenesis of liver damage during natural HBV infection in man remains to be evaluated.

Modulation of the immunological response to hepatitis B virus by antibodies

Antibodies to HBsAg of IgG class enhanced the helper activity of a human T cell clone to promote the in vitro synthesis of immunoglobulins by autologous B lymphocytes. Using two different assay systems, the effect of antigen-specific antibodies on the helper function of a HBsAg-reactive T cell clone was studied. The monoclonal antibody to HBsAg A5C3 (IgG) increased significantly the T cell-dependent production of immunoglobulins by Staphyloccocus aureus-stimulated autologous B lymphocytes. Furthermore, the results obtained with a different type of assay showed that A5C3 also increased the synthesis of antibody to HBsAg by the autologous B cells in the presence of HBsAg and the helper T cell clone. On the other hand, when the monoclonal antibody to HBsAg of IgM class, H5D3 or the F(ab')2 fragment of A5C3 were tested, no significant enhancement of the helper activity of the T cell clone was observed. Experiments performed in mice showed that the in vivo antibody to HBsAg response to low concentrations of HBsAg was significantly enhanced by mixing this antigen with monoclonal antibody to HBsAg of IgG class. No effect was observed when a monoclonal antibody to HBsAg of IgM class was used to prepare the immune-complexed immunogen. The results presented here suggest that antibodies play a critical role in their own production through regulating the activity of helper T cells. This phenomenon might contribute to the increased antibody synthesis of in vivo secondary immune responses and could be of use in designing more efficient vaccine programs in man.

Demonstration of HBsAg as the antigen component in circulating immune complexes detected by peg-solid phase test

The development of an enzyme-linked immunosorbent assay to identify HBsAg as the antigen component within circulating immune complexes using immobilized polyethylene glycol (PEG) is described. The method utilizes, on one hand, the ability of PEG to bind stably to plastic supports and, on the other, to precipitate circulating macromolecules. This method is easily performed, very cheap, quick and, above all, it helps define the biological nature of the immune complexes. HBsAg can be revealed as the antigen component of HBsAg/anti-HBs soluble immune complexes at concentrations of at least 20 ng/ml and either in antigen or antibody excess. Our results indicate that HBsAg circulates in a complexed form in 47% of HBsAg chronic carriers and in 10.7% of patients with liver disease who are positive for serum antibody to hepatitis B surface antigen (anti-HBs) and to core antigen (anti-HBc). None of the other groups of patients in the study had circulating HBsAg in the complexed form.