Prospective study of cellular immunity to hepatitis-B-virus antigens from the early incubation phase of acute hepatitis B

Immune response to hepatitis B virus surface antigen peptides during HBV infection

Antibody responses of patients with acute (n = 73), fulminant (n = 30) and chronic (n = 51) hepatitis B virus (HBV) infection as well as recovered individuals (n = 7) were studied against three synthetic peptides, Pre-S1 amino acids (aa. 12–32), Pre-S2 amino acids (aa. 120–145), and S amino acids (aa. 124–147) of the envelope region (HBsAg). T cell blastogenic response was investigated in a proportion of the patients (27 acute, nine fulminant, 13 chronic hepatitis and seven recovered individuals) along with seven HBV vaccinated and three normal individuals. The presence of T cell response against S peptide was observed in all the cases (9/9, 100%) during early acute hepatitis. This was suppressed during late stages (8/18, 44%) followed by partial reversal during recovery (5/7, 71 %). T cell response and antibodies to Pre-S1 and Pre-S2 peptides were present only in one-third of the patients throughout these periods. The T cell blastogenic response as well as antibody reactivity against these peptides were absent and minimal in chronic hepatitis. Immune response against envelope protein appears to play a major role in acute hepatic injury due to HBV infection and help in virus clearance.

Immunomodulation as an option for the treatment of chronic hepatitis B virus infection: preclinical studies in the woodchuck model

New therapeutic approaches for chronic hepatitis B virus infection based on immunomodulation are now under investigation. The woodchuck model for hepatitis B virus infection has emerged as a useful animal model for the evaluation of such approaches, after developing necessary assays and reagents for immunologic studies in this model. Conventional and novel vaccines such as DNA vaccines were tested in woodchucks for their ability to induce protective immune responses against challenge infection with the woodchuck hepatitis virus (WHV). Furthermore, immunotherapeutic approaches for the control of chronic hepadnaviral infection were evaluated in woodchucks. Immunizations with WHV proteins and DNA vaccines led to the development of antibodies to the WHV surface antigen and to a significant decrease of viral load in chronically WHV-infected woodchucks. Viral vector-mediated gene transfer was explored for the delivery of antiviral cytokines IFN-alpha in woodchucks and resulted in the decrease of viral replication. It is now generally accepted that a combination of antiviral treatment and immunization will be necessary to achieve successful immunomodulation with a long-term control of chronic hepatitis B virus infection.

Immunological techniques in viral hepatitis

The need to quantitate and monitor immune responses of large patient cohorts with standardized techniques is increasing due to the growing range of treatment options for hepatitis B and hepatitis C, the development of combination therapies, and candidate experimental vaccines for HCV. In addition, advances in immunological techniques have provided new tools for detailed phenotypic and functional analysis of cellular immune responses. At present, there is substantial variation in laboratory protocols, reagents, controls and analysis and presentation of results. Standardization of immunological assays would therefore allow better comparison of results amongst individual laboratories and patient cohorts. The EASL-sponsored and AASLD-endorsed Monothematic Conference on Clinical Immunology in Viral Hepatitis was held at the University College London, United Kingdom, Oct 7-8, 2006 to bring together investigators with research experience in clinical immunology of hepatitis B virus (HBV) and hepatitis C virus (HCV) infections for in-depth discussion, critical evaluation and standardization of immunological assays. This report summarizes the information presented and discussed at the conference, but is not intended to represent a consensus statement. Our aim is to highlight topics and issues that were supported by general agreement and those that were controversial, as well as to provide suggestions for future work.

The role of inducible nitric oxide synthase in a murine acute hepatitis B virus (HBV) infection model induced by hydrodynamics-based in vivo transfection of HBV-DNA

BACKGROUND/AIMS

Inducible nitric oxide synthase (iNOS) is found to have antiviral activity. Its role is evaluated using a murine acute hepatitis B virus (HBV) infection model.

METHODS

pHBV3.6 plasmid containing HBV genome was injected into mice by hydrodynamics-based in vivo transfection. HBV antigenemia and serum HBV-DNA were detected by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction, respectively. HBV replication in liver was analyzed by Northern and Southern blot. Intrahepatic leukocytes were isolated and analyzed with flow cytometry.

RESULTS

After hydrodynamics injection of pHBV3.6, HBV genome was synthesized in the liver and HBV-DNA, as well as hepatitis B surface antigen and hepatitis B e antigen were secreted into the blood. Anti-HBV antibody responses developed afterward. A murine acute HBV infection model was established with hydrodynamics injection of non-transponase based HBV-DNA. Using this protocol in iNOS deficient or wild type B6 mice, the level of HBV transcript, replicative intermediate, and antigenemia were higher in iNOS(-/-) than in B6 mice. The intrahepatic leukocytes in iNOS(-/-) mice were also affected after transfection.

CONCLUSIONS

Our data suggests that the iNOS expression not only affects the HBV clearance, but also modulates the infiltrating leukocytes response to HBV antigens.

Kinetics of the immune response during HBV and HCV infection

The innate immune system has a role not only in protecting the host during the initial period of virus infection, but also in shaping the nature of the adaptive immune response. In this review, we follow the kinetics of the virologic and immunologic events occurring from the time of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection. We primarily discuss how the early events after infection might influence the development of the adaptive immune response in these 2 important viral infections and how new strategies for more efficient preventive and therapeutic vaccines can be derived from this knowledge.

Hydrodynamic injection of viral DNA: a mouse model of acute hepatitis B virus infection

Hepatitis B virus (HBV) is a prototype for liver-specific pathogens in which the failure of the immune system to mount an effective response leads to chronic infection. Our understanding of the immune response to HBV is incomplete, largely due to the narrow host restriction of this pathogen and the limitations of existing experimental models. We have developed a murine model for studying human HBV replication, immunogenicity, and control. After transfection of hepatocytes in vivo with a replication-competent, over-length, linear HBV genome, viral antigens and replicative intermediates were synthesized and virus was secreted into the blood. Viral antigens disappeared from the blood as early as 7 days after transfection, coincident with the appearance of antiviral antibodies. HBV transcripts and replicative intermediates disappeared from the liver by day 15, after the appearance of antiviral CD8 + T cells. In contrast, the virus persisted for at least 81 days after transfection of NOD/Scid mice, which lack functional T cells, B cells, and natural killer (NK) cells. Thus, the outcome of hydrodynamic transfection of HBV depends on the host immune response, as it is during a natural infection. The methods we describe will allow the examination of viral dynamics in a tightly controlled in vivo system, the application of mutagenesis methods to the study of the HBV life cycle in vivo, and the dissection of the immune response to HBV using genetically modified mice whose immunoregulatory and immune effector functions have been deleted or overexpressed. In addition, this methodology represents a prototype for the study of other known and to-be-discovered liver-specific pathogens.

Incubation phase of acute hepatitis B in man: dynamic of cellular immune mechanisms

After hepatitis B virus (HBV) infection, liver injury and viral control have been thought to result from lysis of infected hepatocytes by virus-specific cytotoxic T cells. Patients are usually studied only after developing significant liver injury, and so the viral and immune events during the incubation phase of disease have not been defined. During a single-source outbreak of HBV infection, we identified patients before the onset of symptomatic hepatitis. The dynamics of HBV replication, liver injury, and HBV-specific CD8+ and CD4+ cell responses were investigated from incubation to recovery. Although a rise in alanine transaminase (ALT) levels was present at the time of the initial fall in HBV-DNA levels, maximal reduction in virus level occurred before significant liver injury. Direct ex vivo quantification of HBV-specific CD4+ and CD8+ cells, by using human leukocyte antigen (HLA) class I tetramers and intracellular cytokine staining, showed that adaptive immune mechanisms are present during the incubation phase, at least 4 weeks before symptoms. The results suggest that the pattern of reduction in HBV replication is not directly proportional to tissue injury during acute hepatitis B in humans. Furthermore, because virus-specific immune responses and significant reductions in viral replication are seen during the incubation phase, it is likely that the immune events central to viral control occur before symptomatic disease.

Cationic lipid DC-Chol induces an improved and balanced immunity able to overcome the unresponsiveness to the hepatitis B vaccine

Th1 and Th2 immune responses against antigens can be modulated by the use of adjuvants. Since antibody isotypes (IgG1 and IgG2a) and cytokines induced may reflect the Th differentiation taking place during the immune response, the humoral and cellular immune responses induced in mice against hepatitis B virus surface antigen (HBsAg) were examined when the antigen was either adsorbed to aluminum hydroxyde or administered with a new adjuvant the cationic lipid 3beta-[N-(N',N'-dimethylaminoethane)carbamoyl]cholesterol (DC-Chol). The use of DC-Chol increased antibody responses in responding BALB/c mice, induced more consistent IgG1 and IgG2a antibody responses in OF1 mice and overcame the nonresponse to HBsAg in B10.M mice. Furthermore, DC-Chol was able to induce cellular immune responses to HBsAg. The DC-Chol induced a balanced Th1/Th2 response, which enabled mice to overcome the inherited unresponsiveness to HBsAg encountered with aluminum-adjuvanted vaccine. Thus, the DC-Chol provides a signal to switch on both Th1 and Th2 responses, which may have important implications for vaccination against hepatitis B virus, as well as for enhancing weak immunogenicity of other recombinant purified antigens in a nonresponder population.

Kinetics of hepatitis B surface antigen-specific immune responses in acute and chronic hepatitis B or after HBs vaccination: stimulation of the in vitro antibody response by interferon gamma

Because cellular and humoral immune responses against the hepatitis B virus (HBV) surface antigen (HBs) might be crucial to overcome HBV infection, HBs-specific B- and T-cell responses of HBV patients and HBs vaccine recipients were analyzed quantitatively and functionally. In patients with acute hepatitis B (AHB), transient high anti-HBs-secreting B-cell frequencies were observed early after clinical onset, whereas 1 patient who probably developed chronic infection and chronic HBV carriers had absent or weak B- and T-cell responses. In HBs vaccine recipients, maximal HBs-specific B- and T-cell responses were detected after the first injection that decreased gradually before anti-HBs antibodies appeared in serum. Years after vaccination, anti-HBs-secreting B cells were enriched in the bone marrow. After in vitro stimulation with HBsAg, peripheral blood mononuclear cells (PBMC) of only 1 of 5 acute and 1 of 6 chronic HBV patients, but of all 6 vaccine recipients, secreted varying amounts of interferon gamma (IFN-gamma), but no interleukin-4 (IL-4) or IL-5. Furthermore, the addition of IFN-gamma, but not of IL-2, -4, -12, or IFN-alpha, resulted in strong increases of anti-HBs-secreting B cells in vaccine recipients and chronic carriers. In conclusion, circulating anti-HBs-secreting B cells were significantly higher in early acute hepatitis B or early after HBs vaccination than in chronic hepatitis B and decreased in the follow-up as a result of compartmentalization to lymphoid tissues. Release of IFN-gamma by antigen-stimulated T cells might be critical for anti-HBs formation.

Intradermal administration of viral vaccines

Intradermal administration maybe useful in lowering the cost of vaccination against hepatitis B significantly, and may also be helpful for the rapid induction of antibodies, reversing non-responsiveness, improving postexposure prophylaxis and immunising immunocompromised people. In addition, delayed type hypersensitivity skin reaction to the vaccine could serve as a useful marker for the acquisition of T helper type 1 immunoreactivity in vivo. However, there are some disadvantages when using intradermal vaccinations, including the requirement for skilful administration, the absence of approval from licensing authorities, the development of local skin reactions and a lower antibody response when 1/10 of the standard vaccine dose is used. This requires that appropriate vaccination regimens, including the correct vaccine dosage, and vaccination schedule are followed. In the future, a similar vaccination strategy might also be applied for the prevention and control of other infectious diseases. Copyright 1998 John Wiley & Sons, Ltd.

Hepatitis B vaccine containing surface antigen and selected preS1 and preS2 sequences. 1. Safety and immunogenicity in young, healthy adults

The safety and immunogenicity of a yeast-derived recombinant hepatitis B virus (HBV) vaccine containing surface antigen (S) and selected preS1 and preS2 sequences (S-L*) were compared with those of a vaccine prepared with S alone (Engerix-B). S-L* consisted of composite particles containing S and L* at a ratio of 70/30. L* encompassed amino acid residues 12-52 of preS1 residues 133-145 of preS2, and the entire S domain. A total of 100 healthy, HBV-seronegative, young adults were randomized to receive 20 micrograms/dose of either S-L* or Engerix-B under double-blind conditions according to a 0-, 1-, 2-, 12-month schedule. In vivo humoral and in vitro lymphoproliferative responses to S and preS regions were monitored. Addition of the selected preS sequences to S did not enhance the in vivo humoral anti-HBs response but improved the in vitro stimulating capacity of the antigen (L*) in S-L* primed subjects.

The role of transplacental hepatitis B core antibody in the mother-to-infant transmission of hepatitis B virus

AIMS/METHODS

To investigate the influence of transplacental hepatitis B core antibody (anti-HBc) on perinatal hepatitis B virus (HBV) transmission, we studied the anti-HBc titers in 294 mother-neonate pairs.

RESULTS

The anti-HBc titer was highest (10(5.13 +/- 0.80) to 10(4.36 +/- 0.97) in mothers, 10(5.13 +/- 0.76) to 10(5.52 +/- 0.98) in infants) in the 200 hepatitis B e antigen (HBeAg) positive hepatitis B surface antigen (HBsAg) carrier mothers and their infants, second highest (10(4.51 +/- 0.76) and 10(4.68 +/- 0.76)) in the 60 HBeAg-negative HBsAg carrier mothers and their infants, and lowest (10(3.11 +/- 0.76) and 10(3.24 +/- 0.83)) in the 34 non-carrier mothers and their infants (p < 0.05). One hundred and ninety-two infants of HBeAg-positive carrier mothers received hepatitis B immunoglobulin as well as hepatitis B vaccines, and were followed prospectively from birth. Ten infants became HBsAg carriers, and their mothers had significantly lower anti-HBc titers than those of the mothers of 182 infants who did not become carriers (p = 0.003), while maternal serum hepatitis B virus DNA levels (29.9 +/- 23.6 versus 39.9 +/- 58.1 pg/10 ml) did not differ in those two groups (p > 0.25). The same trend was observed in the infants' anti-HBc titers in those two groups (p = 0.0006).

CONCLUSIONS

The association of lower anti-HBc titers in HBeAg-positive carrier mother-infant pairs and the development of carrier status in the infants suggests a positive role of anti-HBc in the modulation of mother-to-infant transmission of HBV. A high maternal anti-HBc level in serum may be a negative predictor of immunoprophylaxis failure in high-risk infants.

Hepatitis B virus immunopathology

Approximately 5% of the world population is infected by the hepatitis B virus (HBV) which causes a necroinflammatory liver disease of variable duration and severity. Chronically infected patients with active liver disease carry a high risk of developing cirrhosis and hepatocellular carcinoma. The immune response to HBV-encoded antigens is responsible both for viral clearance and for disease pathogenesis during this infection. While the humoral antibody response to viral envelope antigens contributes to the clearance of circulating virus particles, the cellular immune response to the envelope, nucleocapsid and polymerase antigens eliminates infected cells. The class I- and class II-restricted T cell responses to the virus are vigorous, polyclonal and multispecific in acutely infected patients who successfully clear the virus, and they are relatively weak and more narrowly focussed in chronically infected patients who do not. The pathogenetic and antiviral potential of the cytotoxic T lymphocyte (CTL) response to HBV have been demonstrated by the induction of a severe necroinflammatory liver disease following the adoptive transfer of HBV surface antigen-specific CTL into HBV transgenic mice, and by the noncytolytic suppression of viral gene expression and replication in the same animals by a post-transcriptional mechanism mediated by interferon-gamma, tumor necrosis factor-alpha and interleukin-2. The dominant cause of viral persistence during HBV infection is the development of a weak antiviral immune response to the viral antigens. While neonatal tolerance probably plays an important role in viral persistence in patients infected at birth, the basis for poor responsiveness in adult onset infection is not well understood and requires further analysis. Viral evasion by epitope inactivation and T cell receptor antagonism may contribute to the worsening of viral persistence in the setting of an ineffective immune response, as can the incomplete down-regulation of viral gene expression and the infection of immunologically privileged tissues. Chronic liver cell injury and the attendant inflammatory and regenerative responses create the mutagenic and mitogenic stimuli for the development of DNA damage that can cause hepatocellular carcinoma. Elucidation of the immunological and virological basis for HBV persistence may yield immunotherapeutic and antiviral strategies to terminate chronic HBV infection and reduce the risk of its life-threatening sequellae.

Ablation of persistent hepatitis B by bone marrow transplantation from a hepatitis B-immune donor

Chronic hepatitis B virus (HBV) infection is still a major cause of liver disease for which no definite therapy is available. We describe here a hepatitis B surface antigen (HBsAg) carrier patient with active viral replication (HBV DNA positive) who was treated for leukemia by bone marrow transplantation (BMT) from an HBV immune donor. Following BMT from the antibody to hepatitis B core antigen (anti-HBc) positive/anti-HBs positive bone marrow donor, immune reconstitution of the recipient's bone marrow resulted in clearance of the circulating HBsAg, as well as HBV DNA. The patient acquired immunity against HBV, which lasted for more than 8 months posttransplantation. Therefore, this report provides evidence that adoptive transfer of specific immunity against HBV through allogeneic BMT may lead to clearance of persistent HBV infection. Furthermore, the data support the hypothesis that the HBsAg carrier state is most probably the result of an inefficient immune response against HBV, implying that clearance of HBV may be facilitated by adoptive cellular immunotherapy.

Fine specificity of the human T-cell response to the hepatitis B virus preS1 antigen

The T-cell response to hepatitis B virus envelope antigens was studied in 11 hepatitis B vaccine recipients; 7 were selected to analyze the fine specificity of the T-cell response to the preS1 antigen. Four distinct T-cell epitopes were identified by peripheral blood lymphomononuclear cell stimulation with a panel of short synthetic peptides covering the preS1 sequence. The immunodominance of the preS1 epitopes included within peptides 21-30 and 29-48 was shown by their capacity to restimulate an HLA class II restricted proliferative response of T cells primed with the whole preS1 antigen. Conversely, peptide-specific T cells selected by peripheral blood lymphomononuclear cell stimulation with peptides 21-30 and 29-48 were able to recognize the native preS1 molecule, confirming that these epitopes are actually generated by the intracellular processing of preS1. Finally, amino acid residues essential for T-cell activation by peptide 21-30 were identified using 10 analogues of the stimulatory peptide containing single alanine substitutions. These results may be relevant to the design of efficient synthetic vaccines against hepatitis B virus infection.

Serum pre-S1 and pre-S2 antigens as prognostic markers in interferon therapy for chronic hepatitis B

We investigated the changes of serum pre-S1 and pre-S2 antigens before and after interferon therapy in 35 carriers with HBeAg, to examine their clinical significance in the therapy. Both antigens were measured quantitatively by solid-phase enzyme immunoassays using monoclonal antibodies specific to each antigen. The titers of these antigens of responders before therapy were significantly lower (p less than 0.001) than those of non-responders (6.23 +/- 1.09 versus 8.65 +/- 2.09 and 4.46 +/- 1.27 versus 6.50 +/- 1.50, respectively). The titers decreased significantly 6 months after interferon therapy in the responders (p less than 0.05), whereas they did not change in the non-responders. Our findings indicate that pre-S1 and pre-S2 antigens have a close correlation with hepatitis B virus replication and are valuable markers for predicting the responsiveness to interferon therapy.

Cellular immune response to HBcAg in mother-to-infant transmission of hepatitis B virus

Cellular immunity to HBcAg was studied in hepatitis B virus carrier children and neonates born to hepatitis B virus carrier mothers. A significant proliferative response of peripheral blood mononuclear cells to HBcAg was found in 5 of 10 children with elevated ALT levels but in none of the nine HBeAg-positive children with normal ALT levels. HBeAg but not HBsAg was detected in cord blood of 9 of 10 neonates born to HBeAg-positive carrier mothers, suggesting exposure of these neonates to HBeAg in utero. However, cord mononuclear cells from neonates born to HBeAg-positive carrier mothers did not show a significant change in the proportion of suppressor and helper T-cell subsets or proliferative response to HBcAg. Nor did they produce interleukin-2 receptor after being cocultured with HBcAg. The unresponsiveness of peripheral-blood mononuclear cells or cord mononuclear cells to HBcAg was not reversed by CD8+ cell depletion. Although cord blood mononuclear cells from neonates born to carrier mothers positive for antibody to HBeAg also did not respond to HBcAg, we encountered an infant, born to a carrier mother positive for antibody to HBeAg, who contracted acute hepatitis B at 2.5 mo of age. The baby's peripheral-blood mononuclear cells showed a significant proliferative response to HBcAg. These results support the view that transplacental maternal HBeAg probably induces a specific unresponsiveness of helper T cells to HBcAg and HBeAg in the neonates born to HBeAg-positive carrier mothers. This specific helper T cell tolerance could be maintained throughout the early replicative phase of carrier state but might break someday with the appearance of raised ALT level.

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.

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.

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.

Treatment of hepatitis B virus infection with interferon. Factors predicting response to interferon

Several randomised controlled trials have been undertaken to evaluate the efficacy of alpha-interferon in the therapy of chronic hepatitis B. In patients with HBe antigen-positive disease acquired in adult life the response rates vary from 25-50%. In those infected at birth, response rates are lower. Twenty-one pretreatment variables were assessed for their significance in response prediction using data from 114 patients given alpha-interferon for chronic hepatitis B virus infection. In those patients who had received a minimum of 90 million units per m2 total dose over 12 weeks, a negative anti-human immunodeficiency virus antibody status (p less than 0.001), chronic active hepatitis on liver biopsy (p less than 0.005), high AST level (p less than 0.001), low hepatitis B virus DNA level (p less than 0.001) and a history of acute hepatitis (p less than 0.005) were all associated with an increased likelihood of response on univariate analysis. On stepwise logistic regression analysis, hepatitis B virus DNA, AST and a history of acute hepatitis predicted response independently (p less than 0.05). The most reliable combination of predictive factors was a negative anti-human immunodeficiency virus antibody status, with either a positive history of acute icteric hepatitis and AST greater than 45 IU per liter or no history of acute icteric hepatitis and AST greater than 85 IU per liter, which predicted response in 77% with a specificity of 79% (p less than 0.001). The loss of HBsAg in addition to HBeAg and hepatitis B virus DNA was more likely to occur in patients with chronic infection of less than 2 years duration (p less than 0.001).

Changes in serum levels of hepatitis B virus markers after interferon treatment

The effect of interferon (IFN) treatment on serum levels of pre-S antigens [pre-S(1) antigen, pre-S(2) antigen, polymerized human serum albumin receptor (pAR)] which are coded by the pre-S region of hepatitis B virus DNA (HBV-DNA), and HBV-markers was analyzed in 23 patients with chronic hepatitis B. One year after IFN treatment, 4 patients (Group C) became HBeAg negative. Six patients (Group B) transiently became HBeAg-negative, but reverted to HBeAg positive. Thirteen patients (Group A) remained HBeAg positive. All of the patients remained HBsAg-positive. Initiation of IFN treatment was rapidly followed by reduction or loss of DNA-P in the serum whether the patients became HBeAg negative or remained positive, and whether serum transaminase (S-GPT) levels became normal or not after IFN treatment. Group C patients, in whom pre-S antigens decreased rapidly during IFN treatment and disappeared before S-GPT levels normalized, became HBeAg negative one year after IFN treatment. Anti-pAR was detected in three out of these 4 patients. In contrast, Group A and Group B patients, in whom pre-S antigens decreased slowly during IFN treatment and did not disappear in spite of those patients being transiently negative for HBeAg and DNA-P, remained HBeAg positive with elevated S-GPT levels one year after IFN treatment. Anti-pAR was almost undetectable. These results suggest that testing for pre-S antigens is more useful for determining the prognosis of patients with chronic hepatitis B treated with IFN than testing for HBsAg, HBeAg and DNA-P.

Which patients with chronic hepatitis B virus infection will respond to alpha-interferon therapy? A statistical analysis of predictive factors

Twenty-one pretreatment variables were assessed for their significance in response prediction using data from 114 patients given alpha-interferon for chronic hepatitis B virus infection. In those patients who had received a minimum of 90 million units per m2 total dose over 12 weeks, a negative anti-human immunodeficiency virus antibody status (p less than 0.001), chronic active hepatitis on liver biopsy (p less than 0.005), high AST level (p less than 0.001), low hepatitis B virus DNA level (p less than 0.001) and a history of acute hepatitis (p less than 0.005) were all associated with an increased likelihood of response on univariate analysis. On stepwise logistic regression analysis, hepatitis B virus DNA, AST and a history of acute hepatitis predicted response independently (p less than 0.05). The most reliable combination of predictive factors was a negative anti-human immunodeficiency virus antibody status, with either a positive history of acute icteric hepatitis and AST greater than 45 IU per liter or no history of acute icteric hepatitis and AST greater than 85 IU per liter, which predicted response in 77% with a specificity of 79% (p less than 0.001). The loss of HBsAg in addition to HBeAg and hepatitis B virus DNA was more likely to occur in patients with chronic infection of less than 2 years duration (p less than 0.001).

The preS1 antigen of hepatitis B virus is highly immunogenic at the T cell level in man

14 hepatitis B vaccine recipients who showed high titers of anti-hepatitis B surface antibodies in serum after booster immunization with a polyvalent hepatitis B surface antigen vaccine that contained trace amounts of hepatitis B virus (HBV) preS1 and preS2 envelope antigens were studied for their in vitro T cell response to these antigens. All 14 subjects displayed a significant proliferative T cell response to the S/p25 envelope region encoded polypeptide; 8 also responded to preS1, while only 1 showed a significant level of T cell proliferation to preS2. Limiting dilution analysis demonstrated that the frequency of preS-specific T cells in two of these vaccine recipients was higher than that of S/p25-specific T cells. T cell cloning was then performed and a total of 29 HBV envelope antigen-reactive CD4+ cloned lines were generated from two preS-responsive vaccines. 21 of these lines were S/p25 specific, 7 preS1 specific, and 1 preS2 specific. Taken together, all these results suggest that the preS1 antigen may function as a strong T cell immunogen in man.

In vitro immune responses to hepatitis B surface antigen (Pre-S2 and S) following remote infection by hepatitis B virus in humans

In this report we evaluate the human immune response to hepatitis B surface antigen (HBsAg) following remote infection with hepatitis B virus (HBV). HBsAg-reactive lymphocytes can be readily demonstrated in the peripheral blood of individuals with established immunity following infection with HBV. In vitro stimulation with small doses of plasma-derived HBsAg, yeast-derived HBsAg (S region) or pre-S2 peptide will induce specific IgG to HBsAg (anti-HBs) in the absence of a polyclonal increase in total IgG. The pre-S2 peptide will stimulate, in a T cell-dependent fashion, the in vitro production of anti-HBs with specificity for the S domain. This anti-HBs production is mediated by pre-S2-stimulated soluble T-cell factors. Peripheral blood mononuclear cells from individuals with established immunity proliferate to the yeast-derived HBsAg but not to the plasma-derived HBsAg or pre-S2 peptide. The chronic HBsAg carriers do not produce anti-HBs following stimulation with HBsAg regardless of the source or component of antigen used. Different study protocols failed to demonstrate HBsAg-specific responses in the peripheral blood mononuclear cells of chronic carriers.

Is booster injection with hepatitis B vaccine necessary in healthy responders? A study of the immune response

Loss of protective anti-HBs levels (less than 10 IU/l) was noted in 5 (13%) of 38 well documented healthy responders to hepatitis B vaccine 30 months after completing the initial standard vaccination series. Revaccination with a single booster injection of 20 micrograms hepatitis B vaccine intramuscularly resulted in anti-HBs levels well above those initially obtained, thus confirming considerable immunological memory. Both decline prior to and rise after booster injection were proportional to the anti-HBs level obtained initially. The antibody production after a single booster injection was closely monitored in 13 individuals. A swift response was observed from day 4 onwards in all subjects. Based on passive immunization data and in vitro infection of human hepatocytes, this time delay is likely to permit infection of hepatocytes. Therefore, until further data on longterm follow-up of vaccinated in individuals in whom anti-HBs levels have dropped to less than 10 IU/l reveal compelling evidence to the contrary, booster injections remain mandatory for those individuals at risk.

Natural history of woodchuck hepatitis virus infections during the course of experimental viral infection: molecular virologic features of the liver and lymphoid tissues

In this study, the kinetic patterns of woodchuck hepatitis virus (WHV) infection were monitored in the liver and the five primary components of the lymphoid system (peripheral blood lymphocytes, lymph nodes, bone marrow, spleen, and thymus). Groups of woodchucks experimentally infected with a standardized inoculum of WHV were sacrificed at different times over a 65-week period beginning in the preacute phase of viral infection and continuing to the period of serologic recovery or the establishment of chronic infections and subsequent hepatocellular carcinoma. Infection by WHV was not limited to the liver but involved the major components of the lymphoid system during all stages of virus infection. A complex series of kinetic patterns was observed for the appearance of WHV DNA in the different lymphoid compartments and the liver during the entire course of viral infection. A progressive evolution of different WHV genomic forms related to the replicative state of WHV was also observed. Lymphoid cells of the bone marrow were the first cells in which WHV DNA was detected, followed in order by the liver, the spleen, peripheral blood lymphocytes, lymph nodes, and finally the thymus. Several differences were observed in the cellular WHV DNA patterns between woodchucks that developed chronic WHV infections and those that serologically recovered from acute WHV infections. The observations compiled in this study indicate that the host lymphoid system is intimately involved in the natural history of hepadnavirus infections from the earliest stages of virus entry.

Treatment of acute and chronic viral hepatitis

Over the 12 years since the first introduction of interferon for the treatment of chronic hepatitis B, progress has apparently been slow. Nevertheless, it now appears that at least one third of chronic hepatitis virus carriers, particularly those with more severe disease, and a similar, perhaps greater, proportion of those with chronic parenteral non-A, non-B hepatitis, can be successfully treated with alpha-interferon. In the not too distant future, controlled trials of alpha-interferons in these situations will be complete and they will be a yardstick by which other future therapies can be judged. Already a number of trials are in progress to determine which agents might, in addition to interferon, augment the response rates. The situation clinically is analogous to that for tuberculosis in the 1950s and for cancer chemotherapy only a decade or so ago. The prospects of prevention of the progression to cirrhosis, and perhaps in the long term reduction in the incidence of hepatocellular carcinoma, are exciting, and with the introduction of a number of new cytokines available through recombinant technology, each with novel antiviral activities, the future prospects are exciting indeed.

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.

Anti-pre-S2 antibodies in natural hepatitis B virus infection and after immunization

Anti-pre-S2 antibodies were detected by enzyme-linked immuno-absorbant assay using a synthetic peptide analogue of pre-S2 protein, in different groups of hepatitis-B-infected subjects, including patients presenting with cirrhosis and liver cancer, and also in infants immunized with hepatitis B vaccine. Anti-pre-S2 antibodies were not detected in hepatitis B surface antigen (HBsAg) chronic carriers, including patients with cirrhosis or primary liver cancer. Anti-pre-S2 antibodies were not detected in HBsAg-positive sera during the early phase of acute hepatitis. They were only noted upon recovery, when anti-HBs antibodies are detectable at the same time as HBsAg. After recovery, anti-pre-S2 antibodies were noted in 57% of test sera and were still detectable in 16% of anti-HBs-positive sera obtained years after HBV infection. Anti-pre-S2 antibodies were detected in 70% of infants immunized with 2 or 5 micrograms doses of Hevac B Pasteur vaccine, confirming that this vaccine contains pre-S2 antigen. Anti-pre-S2 detection was correlated with the anti-HBs antibody titre.

Anti-HBs- and anti-HBc-containing plasma cells in livers of patients with chronic type B hepatitis

Plasma cells are commonly found in liver biopsies in acute and chronic type B hepatitis. Their specificities have not hitherto been examined. In this study, anti-HBs and anti-HBc were looked for in paraffin sections of liver biopsies from 16 patients with chronic type B hepatitis, all seropositive for HBeAg. The technique used was a reversed immunoperoxidase procedure in which purified antigens were applied to sections and detected by means of a further layer of the appropriate monoclonal antibody. Small numbers of plasma cells stained for anti-HBs and anti-HBc in 6 and 4 of 16 biopsies, respectively. Some plasma cells appeared to contain neither antibody. The two antibodies were detected together in only one biopsy. In spite of the small numbers of positive cells as revealed by the technique used, antiviral antibodies produced locally by plasma cells may play a part in the pathogenesis of viral hepatitis.

Serial study of liver-directed autoantibodies and autoreactive T-lymphocytes in acute viral hepatitis B

To explore the mechanisms underlying liver-directed autoimmune reactions in acute Hepatitis B Virus (HBV) infection, we followed five subjects who were identified in the early incubation phase (30-70 days before the first elevation of transaminases). We assessed serially cellular (using a T-lymphocyte migration inhibitory factor assay) and humoral (RIA) immunity to LSP (a macromolecular, liver-derived lipoprotein complex) and hepatic lectin (HL), the liver-specific receptor for desialylated glycoproteins, which appears to be a major target antigen for autoreactions in autoimmune chronic active hepatitis. Anti-LSP and anti-HL autoantibodies were found, at some stage during acute HBV infection, in 4/5 subjects, whereas cellular immunity to the same antigens was detected in only two patients. Sustained production of anti-HL antibodies was noted only in patients showing cellular immunity to this antigen and was apparently secondary to liver damage, whereas anti-LSP antibodies were first detected at the onset of liver injury when there was no evidence of T-cell immunity to the same antigenic complex. One explanation for this apparent dichotomy between cellular and humoral responses to LSP is that a helper T-cell response to the major envelope component of HBV, HBsAg, which precedes by 10-20 days the development of anti-LSP antibodies, promotes a humoral reaction to autoantigens contained in the LSP preparation, coexpressed with HBsAg, on the surface of infected hepatocytes.

Sequential studies of pre-S2 antigenemia and anti-pre-S2 antibodies in relation to viral replication in acute hepatitis B followed from the early incubation phase

To determine the time sequence of expression of pre-S2 peptide (120-150) during the presymptomatic phase of acute hepatitis B, we used a monoclonal antibody radioimmunoassay in five subjects followed from 30 to 70 days before the onset of liver damage. Pre-S2 peptide was present in serum at low levels from the early incubation phase and started to increase immediately after the first detection of HBV-DNA in serum, in parallel with the increase in HBsAg levels. During the symptomatic phase, levels of pre-S2 peptide declined rapidly; it was no longer detectable after recovery. Anti-pre-S2 antibodies were detected, in four patients, only in the recovery phase. These results demonstrate that expression of pre-S2 peptide occurs very early in the incubation phase of acute HBV infection and is cleared in parallel with HBsAg. Anti-pre-S2 antibodies seem to play no role in viral clearance in these patients.