Subclasses of antibodies to hepatitis B core antigen in chronic HBV infection: changes during treatment with alpha interferons and predictors of response

Poor response to 18-month lamivudine monotherapy in chronic hepatitis B patients with IgM anti-HBc and acute exacerbation

BACKGROUND

Appearance of immunoglobulin class M antibody against hepatitis B core antigen is a predictor of beneficial response to interferon-alpha therapy in chronic hepatitis B patients, but its relationship with the efficacy of lamivudine therapy remains unclear.

AIM

To investigate the outcome of lamivudine therapy in chronic hepatitis B patients with immunoglobulin class M antibody against hepatitis B core antigen and acute exacerbation.

METHODS

Chronic hepatitis B patients with acute exacerbation receiving a national-wide therapeutic trial of 18-month lamivudine monotherapy were enrolled for the analysis. Four consecutive seronegative patients were recruited as individual matching controls of one positive subject. Immunoglobulin class M antibody against hepatitis B core antigen in serum was assayed monthly by an automated microparticle enzyme immunoassay.

RESULTS

Fifteen (8.9%) of 167 chronic hepatitis B patients with acute exacerbation were seropositive for IgM anti-HBc. Thus 60 seronegative patients were consecutively recruited as control group. At the end of therapy, two (13.3%) of the 15 seropositive patients achieved a sustained response, significantly lower than 26 (43.3%) of the control group.

CONCLUSIONS

Appearance of immunoglobulin class M antibody against hepatitis B core antigen in chronic hepatitis B patients with acute exacerbation is a predictor of poor response to lamivudine monotherapy. This is clinically relevant to the decision-making in treating chronic hepatitis B patients with acute exacerbation.

Immune recognition of linear antigenic regions within the hepatitis B pre-C and C-gene translation products using synthetic peptides

The antibody recognition of linear regions within the amino acid (aa) sequence of hepatitis B (HB) core antigen (HBcAg), e antigen (HBeAg), and pre-C region was investigated in 46 patients infected with hepatitis B virus (HBV), and one immunized rabbit. Peptide analogues were synthesized to cover the complete product of the C-gene, including the pre-C region using various synthetic methods. Two carriers of hepatitis B surface antigen (HBsAg) with anti-HBe, recognized pin-bound decapeptides covering amino acid (aa) 76-83 of HBc/eAg, and the most essential residues were found to be Asp78, Pro79, Arg82, and Asp83. Pre-C peptides were recognized by IgG1 or IgG3 in sera from two out of ten cases with acute HB, in four out of twelve sera from HBeAg-positive carriers of HBsAg, and in two out of twelve sera from anti-HBe-positive carriers of HBsAg. Two sera from the cases of acute HB showed strong reactivity of the IgG3 isotype with HBc/eAg peptides 61-85. Five of the sera from HBeAg-positive carriers of HBsAg were weakly reactive with peptides 41-60, 61-85, 121-140, and/or 141-160. Eight of the sera from anti-HBe-positive carriers of HBsAg recognized aa 121-140 of HBc/e with IgG1, IgG3, and/or IgG4 isotypes. IgG from one immunized rabbit recognized peptides 1-20, 61-85, and 71-90, and the T-cells recognized peptides 1-20 and 71-90. Thus, human and rabbit antibodies recognize linear antigenic regions within the pre-C, and within regions 1-20, 41-60, 61-85, 121-140, and 141-160 of HBcAg.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of serum IgM anti-HBc in chronic hepatitis B virus infection

Because of widely differing reports on the significance of IgM anti-HBc in chronic hepatitis B virus (HBV) infection, paired sera and liver biopsies from 49 patients with chronic HBV infection were analysed for serum IgM anti-HBc, HBsAg titre, HBeAg/anti-HBe, HBV DNA, serum aspartate transaminase, intrahepatic HBcAg expression, and liver histology. High levels of IgM anti-HBc, in the diagnostic range of acute hepatitis B (greater than 1.2), were detected in seven patients (14.3%) and a total of 34 patients (69.6%) had an index of more than 0.2. No correlation was found between IgM anti-HBc and the serum markers of active viral replication or HBsAg titre but it correlated significantly with intrahepatic expression of cytoplasmic HBcAg (r2 = 0.165, P = 0.002). IgM anti-HBc also correlated with active liver histology (P = 0.015) but there was a considerable overlap of the IgM anti-HBc index values between the various disease groups, indicating a poor specificity. Serial assessment of IgM anti-HBc in eight patients treated with interferon-alpha (four responders) showed an increase in IgM anti-HBc in three out of four patients corresponding to the e-seroconversion period followed by a drop in IgM anti-HBc levels. However, an increase in IgM anti-HBc was also seen in one non-responder, indicating that this feature is not unique to interferon-alpha responders. These data indicate that serum IgM anti-HBc cannot be used alone as a certain diagnostic measure of HBV replication nor in the prediction of liver histology.

Immunoglobulin G subclasses of antibodies to hepatitis B core antigen in HBs antigen positive liver diseases

Serum immunoglobulin G (IgG) subclasses of hepatitis B core antibody (anti-HBc) in 54 patients with different types of hepatitis B surface antigen positive (HBsAg+) liver diseases (asymptomatic carrier (ASC), acute hepatitis (AH), chronic hepatitis (CH) and liver cirrhosis (LC)) and 18 normal controls were estimated by enzyme-linked immunosorbent assay (ELISA) using subclass specific anti-human mouse monoclonal antibodies. In 11 cases, the estimations were carried out at both exacerbation and remission stages of chronic active hepatitis (CAH). In 4 cases of CAH, serial observations of anti-HBc IgG subclasses were made according to the clinical course. In 5 cases of CAH, the estimations were carried out at the HBe antigen positive (HBeAg+) stage and after sero-conversion to anti-HBe positive (anti-HBe+) stage. In ASC the main anti-HBc IgG subclasses were restricted to one subclass--anti-HBc IgG1. In AH on the other hand, all the subclasses were represented. In CH all the subclasses were detected under different diagnostic conditions but anti-HBc IgG1 was the main subclass. In LC the mean concentration of anti-HBc IgG3 was higher than the concentration of anti-HBc IgG1. In exacerbation stages of CAH, the different anti-HBc IgG subclasses had higher concentrations than in remission stages. The concentrations of different anti-HBc IgG subclasses fell just after seroconversion from HBeAg+ stage to anti-HBe+ stage. These data suggest that the estimation of anti-HBc IgG subclasses may be helpful in establishing the diagnosis of different types and stages of HBsAg+ liver diseases.

The hepatitis B virus

Of all the hepatotropic viruses, HBV is associated with the greatest worldwide morbidity and mortality. This is because of the ease of transmission and the potential for progression to a chronic infective carrier state, with the complications of cirrhosis and hepatocellular carcinoma. The use of PCR has shown that some of the earlier concepts concerning the interpretation of serological data were inaccurate. Many patients with anti-HBe and anti-HBs have viral DNA detectable by PCR, and some hepatocellular carcinoma patients have detectable HBV DNA in their livers in the absence of all serological markers of HBV disease. The clearance of HBV infected cells from the liver is dependent on the interplay between the interferon system and the cellular limb of the host immune response. The importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells has been established for chronic HBV infection. The importance of pre-S sequences as inducers and targets of the virus-neutralizing humoral immune response is becoming established, but their precise role must await the development of in vitro models of hepadnavirus infection and a greater understanding of the mechanisms of viral uptake. The epidemiology and clinical course of the disease can be modified by immunization, immune stimulation and antiviral chemotherapy. For the developing world, a programme of immunization at birth would be the most effective way of eliminating this disease, but at present the cost is prohibitive. For the developed world, immunization is realistic for the at-risk population, and anti-viral and immunostimulatory therapy available for those already infected. In adult acquired chronic HBV infection alpha-interferon produces HBe antigen clearance in 40-60% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce HBe antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic remains unclear, and its relationship to fulminant hepatitis is under investigation.

The hepatitis B virus and the host response

The clearance of hepatitis B virus infected cells from the liver is probably dependent on an interplay between the interferon system and the cellular limb of the host immune response. Although the importance of the nucleocapsid proteins as targets for sensitized cytotoxic T cells is established in chronic hepatitis B infection, further studies are needed during the early phase of acute infection. The relative importance of pre-S sequences as inducers and targets of the virus neutralizing humoral immune response is becoming established but their precise place will await the development of in vitro models of hepadna virus infection and precise definition of the mechanism of viral uptake. In adult life, deficient production of alpha-interferon and suppression of the ability of the host to respond to interferon are probably important factors underlying the development of chronic infection. In the neonate, however, specific suppression of the cell-mediated immune response may be involved. The presence of a mutation in the pre-core region of some virus isolates has recently been described. Hepatocytes infected with this virus cannot produce hepatitis B e antigen and the course of the liver disease is fairly rapid. Whether this mutant causes liver damage in the same way as the wild virus or is directly cytopathic needs further study. In adult-acquired chronic hepatitis B virus infection, alpha-interferon produces hepatitis B e antigen clearance in 26-88% of cases and is followed by resolution of the hepatic inflammation. Results in neonatally acquired infection are less impressive and prednisolone priming followed by interferon may be needed.(ABSTRACT TRUNCATED AT 250 WORDS)