Immunoglobulin isotypes of anti-HBc and anti-HBe and hepatitis B virus (HBV) DNA elimination in acute hepatitis B

Anti-hepatitis B surface antigen IgG1 subclass is predominant in individuals who have recovered from hepatitis B virus infection, chronic carriers, and vaccinees

Patterns of each IgG-specific subclass for hepatitis B virus (HBV) core antigen (anti-HBc) are remarkably different among individuals with different infection status, i.e., completely recovered or chronic carrier. Each of the IgG-specific subclasses of HBV surface antigen (anti-HBs) was tested for ELISA sensitivity using four commercially available hepatitis B surface antigen (HBsAg) kits and one self-prepared plate. The specificity in 18 serum samples obtained from chronic HBV carriers, recovered individuals, vaccinees and non-infected individuals was investigated. Differences in absorbance values were obtained by comparing results from these different plates. Data on the absorbance values of anti-HBs IgG subclasses obtained indicated that one to four subjects had a false-negative or false-positive result using the four commercial plates. Only the self-prepared plate demonstrated 100% specificity and sensitivity for anti-HBs subclasses. Moreover, the results indicate that anti-HBs subclass IgG1 was predominant in cured patients, chronic carriers and vaccinees. The samples from both chronic carriers and vaccinees exhibited a significantly higher concentration of total IgG and IgG1 than samples in recovered individuals (P<0.05).

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.

Anti-HBc IgG subclasses in different populations by comparing a variety of ELISA plates

The number of IgG subclasses for hepatitis B virus (HBV) core antigen (anti-HBc), demonstrated for HBV-infected individuals, was measured by enzyme-linked immunosorbent assay (ELISA). Four commercially available hepatitis B core antigen (HBcAg) plates and one prepared plate were tested for ELISA sensitivity by the detection of 14 serum samples drawn from HBV chronic carriers, cured patients, vaccinees, and non-infected individuals. Differences in optical density (OD) values were obtained by comparing data gathered from the five plate types, suggesting that different plates may have different binding capabilities for each anti-HBc IgG subclass and, thus, contribute to the different ELISA sensitivities. Of these plates, the GB plate showed the most obvious absorbance changes for anti-HBc subclasses in different populations. These data also indicated different patterns for IgG-specific subclasses for various populations. For HBsAg+ carriers, the OD for IgG1 was greater than for IgG3. By contrast, the OD for IgG3 was higher than that for IgG1 in those subjects who were negative for HBsAg.

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)

Antigenic regions within the hepatitis C virus envelope 1 and non-structural proteins: identification of an IgG3-restricted recognition site with the envelope 1 protein

Antibody binding to antigenic regions of hepatitis C virus (HCV) envelope 1 (E1; residues 183-380, E2/non-structural (NS) 1 (residues 380-437), NS1 (residues 643-690), and NS4 (1684-1751) proteins were assayed for 50 sera with antibodies to HCV (anti-HCV) and for 46 sera without anti-HCV. Thirty-four peptides, 18 residues long with an eight-amino acid overlap within each HCV region, were synthesized and tested with all 96 sera. Within the E region 183-380, the major binding site was located to residues 203-220, and was recognized by eight sera. Within the E2/NS1 region 380-437, the peptide covering residues 410-427 was recognized by two sera, and within the NS1 region 643-690, peptides covering residues 663-690 were recognized by four sera. Within the NS4 region 1684-1751, 27 sera were reactive to one or more of the NS4 peptides, and 21 out of these were reactive with peptide 1694-1711. One part of the major binding site could be located to residues 1701-1704, with the sequence Leu-Tyr-Arg-Glu. The IgG1, IgG3 and IgG4 subclasses were reactive with the five antigenic regions of HCV core, residues 1-18, 11-28, 21-38, 51-68 and 101-118. Reactivity to the major envelope site consisted almost exclusively of IgG3, and reactivity to the major site of NS4 consisted only of IgG1. Thus, a non-restricted IgG response to linear HCV-encoded binding sites was found to the core protein, whereas IgG subclass-restricted linear binding sites were found within the E1 protein, and within the NS4 protein.

Immunoglobulin G subclass responses against the structural components of Puumala virus

Sera from sequentially bled nephropathia epidemica patients (acute-phase, convalescent-phase, and 2-year sera) and sera from 10 to 20 years postinfection were examined by immunoglobulin G (IgG) subclass-specific ELISAs for reactivities against each of the Puumala virus structural proteins (N, G1, and G2). IgG1 was found to be the dominating antiviral subclass, and most of the patients had IgG1 directed to all three structural proteins at all times with a continuous increase over time. IgG2 to the three viral proteins was detected in very low amounts in only a few of the samples. All of the serially bled patients developed IgG3 against each of the proteins, but the responses against the different viral components varied; anti-N- and anti-G1-specific IgG3 showed a peak in the convalescent-phase samples, while the anti-G2 IgG3 response was highest in the acute-phase sera. Eight of ten serially bled patients developed specific IgG4. The IgG4 responses showed similar patterns against all three viral proteins with very low optical density values in the acute- and convalescent-phase samples, followed by higher optical densities in the sera drawn 2 years after infection. Seven of nine 10-year sera contained virus-specific IgG4. These results support the theory concerning the persistence of Puumala virus or viral antigens several years after infection.

Improvement in the specificity of assays for detection of antibody to hepatitis B core antigen

Reducing agents dramatically alter the specificity of competitive assays for antibody to hepatitis B core antigen (anti-HBc). A specificity improvement was demonstrated with a new assay which utilizes microparticle membrane capture and chemiluminescence detection as well as a current radioimmunoassay procedure (Corab: Abbott Laboratories, Abbott Park, Ill.). The effect was most noticeable with elevated negative and weakly reactive samples. In both systems, reductants increased separation of a negative population (n = 160) from assay cutoffs. With a selected population (n = 307), inclusion of reductant eliminated apparent anti-HBc activity in 54 of 81 samples in the 30 to 70% inhibition range. Reductant-stable anti-HBc samples were strongly associated with the presence of antibody to hepatitis B surface antigen (21 of 27). The association persisted below the detection limits of current assays to 0.3 to 0.4 Paul Ehrlich Institute units per ml. Only 1 of 54 reduction-sensitive borderline samples was confirmed to be positive for antibody to hepatitis B surface antigen. The modified procedures had unchanged or slightly improved sensitivity for immunoglobulin G (IgG)-associated anti-HBc activity. Although IgM anti-HBc detection was reduced from four- to eightfold in the presence of reductants, sensitivities remained at least twofold greater than tha of an enzyme immunoassay (Corzyme M; Abbott) designed to detect acute-phase levels of IgM anti-HBc. The use of reducing agents should significantly improve the reliability of anti-HBc testing, especially near assay cutoffs.

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.