The utilization of biotin-antibiotin interaction for the detection of antibody to hepatitis B surface antigen (anti-HBs)

A biotin-antibiotin solid-phase enzyme-linked immunoassay for the detection and quantitation of the antibody to hepatitis B surface antigen (anti-HBs) is described. The assay utilizes hepatitis B surface antigen as a solid-phase 'capture' reagent and a mixture of biotinylated HBsAg and antibiotin-conjugated horseradish peroxidase as a detector reagent. The assay was compared to a commercial enzyme immunoassay (AUSAB EIA) which used the biotin-avidin system for anti-HBs detection. The two assays were found to measure the same molecules and to correlate well regarding anti-HBs titers.     

A biotin/avidin solid-phase sandwich enzyme immunoassay for the antibody to hepatitis B surface antigen (anti-HBs)

A biotin/avidin solid-phase enzyme immunoassay for the detection and quantitation of the antibody to hepatitis B surface antigen (anti-HBs) is described. The assay utilizes hepatitis B surface antigen (HBsAg) as a solid-phase 'capture' reagent and a mixture of biotinylated HBsAg and avidin-conjugated horseradish peroxidase as a probe 'detector' reagent. The assay was compared to a commercial radioimmune assay for anti-HBs detection. The two assays were found to measure the same molecules and to correlate well regarding anti-HBs titers.     

Characterization of a reduction-sensitive factor from human plasma responsible for apparent false activity in competitive assays for antibody to hepatitis B core antigen.

Addition of reducing agents to competitive assays for antibody to hepatitis B core antigen (anti-HBc) eliminates apparent false reactivity of specimens obtained from individuals with no prior history of hepatitis B virus (HBV) infection and without other serological markers of HBV infection. We have purified and characterized a reduction-sensitive factor (RSF) isolated from the plasma of several volunteer blood donors. Column fractions were assayed fro anti-HBc by using a highly sensitive chemiluminescence assay with a detection of 0.15 Paul Ehrlich Institut units per ml at 50% inhibition. Gel filtration on Sephacryl S-300 indicated that reductant-sensitive samples possessed anti-HBc activity that was associated with immunoglobulin M (IgM), whereas reductant-stable activity was associated with IgG. Gel filtration followed by metal chelate affinity chromatography resulted in a 55-fold purification and demonstrated that RSF activity copurifies with IgM. RSF was recovered from a recombinant hepatitis B core antigen matrix and shown to be an IgM species by immunoblot. In addition, RSF activity coeluted with IgM protein from anti-mu-chain Sepharose. Discrepancies between enzyme immunoassay and radioimmunoassay procedures for anti-HBc (Corzyme and Corab, respectively: Abbott Laboratories, North Chicago, Ill.) appear to be due to the relative sensitivity of the enzyme immunoassay for IgM anti-HBc (sevenfold greater than the radioimmunoassay using a specific panel). The biological basis for the occurrence of low levels of nonspecific IgM anti-HBc reactivity in individuals not previously exposed to HBV remains to be elucidated.     

Detection of IgM to hepatitis B core antigen in a reductant containing, chemiluminescence assay

The Abbott PRISM® hepatitis B core (HBc) antigen assay is an automatic in vitro competitive chemiluminescence immunoassay for the detection of total antibody to HBc (anti-HBc) antigen in human serum or plasma. The assay utilizes cysteine solution as a reducing reagent in order to maximize specificity. To help understand the effect of cysteine on detection of anti-HBc antigen, we separated and purified anti-HBc IgM and IgG from human plasma using size exclusion, protein A/G, and affinity chromatography techniques. We showed that cysteine affected the reactivity of anti-HBc IgM with recombinant HBc (rHBc) antigen but not the reactivity of anti-HBc IgG. Anti-HBc IgM treated with cysteine yielded byproducts which were reactive in the PRISM HBcore assay. Reduction-sensitive factor (RSF) — IgM fraction from serum known to be non-specific for anti-HBc activity, similarly treated with cysteine, was no longer reactive in the PRISM HBcore assay. We showed that cysteine treatment is effective against non-specific IgM in human blood. Also, the inclusion of cysteine in the PRISM HBcore assay does not compromise the detection of HBc specific antibodies.     

Significance of anti-HBc IgM in the differential diagnosis of viral hepatitis

IgM antibody to hepatitis B core antigen (anti-HBc IgM) as determined by IgM capture immunoassay is generally present in high titer during acute hepatitis B infection. A strong positive reaction for anti-HBc IgM during acute hepatitis is indicative of an acute HBV infection even in hepatitis B surface antigen (HBsAg)-negative patients. With the help of anti-HBc IgM otherwise unidentified HBV infection can be diagnosed in HBsAg-negative patients and an optimal combination of diagnostic tests for acute hepatitis B infection would therefore include assays for both HBsAg and anti-HBc IgM. In the HBsAg carrier with or without chronic liver disease the presence and meaning of anti-HBc IgM is still a matter for discussion. Detection of a weak positive result for anti-HBc IgM in HBsAg-positive patients without a recent history of acute hepatitis cannot always be regarded as a definite marker of recent hepatitis B infection. However. quantitation of the anti-HBc IgM results seems to improve the clinical value of the test. Comparison of the available anti-HBc IgM assays is needed and may well establish a reliable cut-off level that would differentiate acute from chronic hepatitis B and ongoing from resolving hepatitis B in HBsAg-positive patients.     

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.     

Diagnostic value of anti-HBc IgM in high HBV prevalence areas

The diagnostic value of an anti-mu-capture immunoassay for the detection of IgM antibody against hepatitis B core antigen (anti-HBc) was evaluated. Strongly positive results were obtained from the acute phase sera of the 25 acute hepatitis B patients who were hepatitis B surface antigen (HBsAg) positive and of the 18 confirmed acute hepatitis B patients who had already cleared HBsAg when symptoms developed. Negative results were obtained in 5 hepatitis A patients, 20 non-A, non-B acute hepatitis patients serologically susceptible to HBV, 22 patients with chronic hepatitis B liver disease, 15 asymptomatic HBsAg carriers, and 10 healthy patients immune from past HBV infection. Fourteen of the acute hepatitis patients remained HBsAg positive for a follow-up period of at least 6 months, and 12 of these were found consistently anti-HBc IgM negative. These were considered as chronic HBsAg carriers with a superimposed form of acute liver injury. These data show that this assay can differentiate between acute from chronic (HBsAg positive) and recent from old (HBsAg negative) hepatitis B virus infection. Thus, it should be very useful in the complex diagnostic situations encountered commonly in areas with high prevalence of HBV infections.     

Evaluation of enzyme immunoassay for anti-HBc IgM in the diagnosis of acute hepatitis B virus infection

Corzyme-MTM (Abbott Laboratories, North Chicago, IL), a newly introduced kit for the measurement of serum IgM antihepatitis B core antigen by enzyme immunoassay, was evaluated for the diagnosis of acute B-viral hepatitis (AVH-B). The study included 175 acute viral hepatitis patients with transient hepatitis B surface antigen (HBsAg). Sera from 160 were tested on multiple occasions until their HBsAg cleared. IgM anti-HBc was found in 171 of 175 patients (98.4%) during the acute phase. The serum samples from 42 patients with liver biopsy-proven chronic active hepatitis, type B (CAH-B), and 18 patients with persistent hepatitis, type B (PH-B), were analyzed for the presence of IgM anti-HBc, using the same technic. None of the sera from 42 patients with CAH-B and only 2 of the 18 patients with PHB had IgM anti-HBc. Thus, the measuring IgM anti-HBc using Corzyme-M kit is helpful in the diagnosis of AVH-B and in the discrimination of acute from chronic HBV infections.     

Evaluation of anti-HBc IgM estimation by radioimmunoassay for anti-HBc on column separated IgM

Tests for Igm antibody to hepatitis B core antigen (anti-HBc IgM) are useful diagnostic tools in the evaluation of patients with hepatitis B virus (HBV) infection. A method is described for detecting anti-HBc IgM based on application of a commercially available radioimmunoassay for total anti-HBc to column separated serum IgM and the technique is evaluated in patients with acute and chronic HBV infection. Our test is both sensitive and specific for diagnosing acute hepatitis B, although duration of positivity is highly variable. This technique is simple, inexpensive, and might be particularly useful for laboratories performing limited numbers of examinations, or with limited resources. A 45 percent savings in reagent costs is realized in our laboratory.     

Selective detection of IgM-antibody against core antigen of the hepatitis B virus by a modified enzyme immune assay.

IgM antibody against core antigen of the hepatitis B virus (anti-HBc IgM) was selectively determined by a new enzyme immunoassay (EIA). Microtiter plates were coated with anti-human micro chain immunoglobulin. On addition of serum IgM is bound by a factor of about 4,000 more than IgG. After removing the sample, HBcAg is added to the IgM-coated surface. Binding takes place if the IgM contained anti-HBc and was demonstrated by the aid of a conjugate made from anti-HBc IgG and horse radish peroxidase. Quantitation may be achieved without testing a dilution series. The assay was not disturbed by a large excess of anti-HBc IgG in the sample and rheumatoid factor did not produce false-positive results, provided the sample was diluted in an excess of aggregated IgG. The diagnostic relevance of the assay was demonstrated in selected cases of acute hepatitis B. Rapid diagnosis of acute hepatitis B infection is therefore now possible in those cases whihc are HBsAg-negative but anti-HBc-positive.     

Application of hepatitis B core particles produced by human primary hepatocellular carcinoma (PLC/342) propagated in nude mice to the determination of anti-HBc by passive hemagglutination

Human primary hepatocellular carcinoma (PLC/342), carried by nude mice, produces hepatitis B core particles as well as hepatitis B surface antigen particles. Core particles purified form PLC/342 tumors displayed epitopes of hepatitis B core antigen (HBcAg) but not epitopes of hepatitis B e antigen (HBeAg) on their surface, unlike core particles prepared from Dane particles, derived from plasma of asymptomatic carriers, that expressed epitopes of both HBcAg and HBeAg. Core particles obtained from PLC/342 tumors were applied to the determination of antibody to HBcAg (anti-HBc) by passive hemagglutination. The assay detected anti-HBc not only in individuals with persistent infection with hepatitis B virus and in those who had recovered from transient infection, but also in patients with acute type B hepatitis, indicating that it can detect anti-HBc of either IgG or IgM class. A liberal availability of core particles from tumors carried by nude mice, taken together with an easy applicability of the method, would make the passive hemagglutination for anti-HBc a valuable tool in clinical and epidemiological studies, especially in places where sophisticated methods are not feasible.     

Diagnostic significance of anti-HBc IgM (RIA) in healthy HBsAg carriers and in chronic hepatitis B

The diagnostic significance of IgM antibody against hepatitis B core antigen (anti-HBc) in healthy hepatitis B surface antigen (HBsAg) carriers and in subjects affected by chronic hepatitis B was evaluated. IgM anti-HBc was sought and found in all nine patients examined who were affected by acute HBsAg-positive hepatitis. It was also detected in 2 out of 18 patients with HBsAg-positive chronic persistent hepatitis and in 12 out of 42 patients affected by HBsAg-positive chronic active hepatitis. The absence of this marker was noted in all 26 HBsAg healthy carriers and in the subjects with HBsAg-positive cirrhosis. No relationship was found between the presence of IgM anti-HBc and the degree of inflammatory activity in the patients with HBsAg-positive chronic active hepatitis. A correlation was not found between the presence of IgM anti-HBc and the presence of hepatitis B e antigen (HBeAg) in the same patients. These data show that the absence of IgM anti-HBc may be useful in identifying healthy carriers of HBsAg. The presence of this antibody may be a suitable indication of acute HBsAg-positive hepatitis. In patients with chronic active hepatitis B the presence of IgM anti-HBc cannot be used as diagnostic tool in predicting the severity of liver disease.     

Comparison of radioimmunoassay and counter-immunoelectrophoresis for the detection of antibody to hepatitis B core antigen

A competitive solid-phase radioimmunoassay (RIA) for antibody to hepatitis B core antigen (anti-HBc) was set up using purified hepatitis B core antigen and ¹²⁵I-labeled anti-HBc. RIA was compared with counter-immunoelectrophoresis (CIEP) for anti-HBc by examining a panel of quality control sera, clinical specimens screened for evidence of hepatitis B virus infection and sera collected during a VD clinic survey.RIA for anti-HBc was found to be more sensitive and more specific than CIEP. It detected anti-HBc in all HBsAg-positive and in most anti-HBs-positive patients. CIEP for anti-HBc was also positive in almost all HBsAg-positive patients but was frequently negative in anti-HBs-positive patients. Non-specific reactions occurred in both tests but by RIA they could be more easily distinguished from true positives.     

Enzyme immunoassay for anti-hepatitis B core (HBc) immunoglobulin G1 and significance of low-level results in competitive assays for anti-HBc

An enzyme immunoassay (EIA) for anti-hepatitis B core (HBc) immunoglobulin G1 (IgG1) was compared with a commercial radioimmunoassay (RIA) for anti-HBc antibody (Corab: Abbott Laboratories, North Chicago, Ill.). In parallel tests of 445 consecutive samples, discrepant results were obtained with 2 samples, 1 of which was positive only by the RIA and the other of which was positive only by the EIA for anti-HBc IgG1. In tests of another 192 samples with low blocking activity in the RIA (inhibition range, 90 to 30%), 10 samples gave discrepant results, 5 of which were positive only by the RIA and the other 5 of which were positive only by the EIA for anti-HBc IgG1. Of 12 samples with discrepant results, 11 samples were tested further for anti-HBc IgG3, IgM, and IgA1 by the EIA. Of these, seven samples were positive for anti-HBc IgG1, anti-HBc IgG3, or both. All seven samples were also positive for anti-hepatitis B surface (HBs) antigen. Three samples were negative for anti-HBc IgG1, anti-HBc IgG3, or both but were positive for anti-HBc IgM, anti-HBc IgA1, or both; and one sample was reactive only in the RIA. These four samples were all negative for anti-HBs. Thus, low-level results in the RIA caused by anti-HBc IgM, anti-HBc IgA, or both reflect the unspecific activation of immature B lymphocytes that is not related to previous exposure to hepatitis B virus (HBV). In contrast, the presence of anti-HBc IgG1, anti-HBc IgG3, or both indicates differentiated anti-HBc IgG-producing plasma cells and previous exposure to HBV, as was also shown by the presence of anti-HBs. On class and subclass determination for confirmation of positivity for anti-HBc in 19 serum samples, which was identified by screening of blood from 1,343 donors by a competitive EIA (Hepanostika; Organon), 9 samples with positive results, all low level, did not indicate previous exposure to HBV. It was concluded that determination of classes and subclasses of anti-HBc provides a tool for discriminating positive anti-HBc results not caused by HBV exposure.     

Anti-DNA,anti-HBc correlations with RIA-detected HBeAg and anti-HBe in chronic HBsAg carriers

The interrelations of 1) antibody to hepatitis B core antigen (HBcAg) — anti-HBc; 2) single-stranded DNA-binding antibodies (anti-DN A); and 3) the e-antigen/antibody system — hepatitis B e antigen (HBeAg) and antibody (anti-HBe), were studied in 150 hepatitis B surface antigen (HBsAg) carriers, in 43 of whom diagnostic liver biopsies had been performed. There was a good correlation between titers of anti-HBc and anti-DN A, regarded as indicators of viral and pathological activity, respectively, as well as between levels of these two antibodies and the presence of HBeAg or anti-HBE as detected by radio-immune assay (RIA). In general, HBeAg-positive carriers showed high anti-HBc and high anti-DNA titers, while the carriers positive for anti-HBe had low titers of both. These findings were in accord with the histopathological results. The three serologic parameters, anti-HBc, anti-DNA, and e-antigen/anti-body, should together prove useful for the evaluation of the clinical status of chronic HBsAg carriers.     

Distribution of HBcAg in hepatitis B detected by immunoperoxidase staining with three different preparations of anti-HBc antibodies.

To evaluate the role of the expression of hepatitis B core antigen (HBcAg) in liver cell damage the immunoperoxidase staining pattern of cryostat liver biopsy specimens from 16 chronic carriers of hepatitis B surface antigen (HBsAg) was investigated using three different kinds of anti-HBc antibodies. Polyclonal antibody prepared from recombinant HBcAg seemed to be more sensitive in detecting HBcAg than did monoclonal antibody from the same antigen. The topographical distribution of HBcAg detected by these two antibodies was similar, showing a close correlation to the histological activity of disease. Furthermore, the predominant localisation of cytoplasmic HBcAg usually reflected an active and severe ongoing hepatitis. On the other hand, monoclonal antibody prepared from purified Dane particles resulted in the prominent cytoplasmic staining for HBcAg regardless of histological severity of the hepatitis. The quantitative expression and topographical distribution of HBcAg depended on the type of anti-HBc antibodies used.     

Immunoglobulin M antibodies to hepatitis B core antigen: evaluation of enzyme immunoassay for diagnosis of hepatitis B virus infection

In acute and chronic hepatitis B, antibodies of the immunoglobulin M (IgM) class against the hepatitis B core antigen (anti-HBc IgM) have been demonstrated. For the determination of anti-HBc IgM, a sensitive enzyme immunoassay with anti-mu-coated flat-bottomed microtiter plates is described and evaluated. The specificity of the anti-HBc IgM test system was proven by pretreatment of presumed anti-HBc IgM-positive samples with anti-mu to block anti-HBc IgM. The test system was highly sensitive. In the acute stage of hepatitis B, anti-HBc IgM could be demonstrated in serum dilutions up to 10(-7) (mean titer, 10(-5)), and in sera from patients with chronic hepatitis B, the mean titer was 10(-3). In a study of unselected patients whose sera were sent at irregular intervals for testing, anti-HBc IgM persisted in a high percentage (52%) for at least 13 to 18 months after onset of illness despite the fact that these patients eliminated hepatitis B surface antigen (HBsAg) and produced antibodies to HBsAg (anti-HBs). By using the anti-HBc IgM test as an additional aid in the diagnosis of acute HBsAg-negative hepatitis, the hepatitis B etiology could be established in 13 of 42 patients (31.4%). Investigations of the prevalence of anti-HBc IgM in different groups of patients with chronic hepatitis B infection showed 89.4% anti-HBc IgM-positive results in patients with chronic active hepatitis B, 60% in patients with HBsAg-negative chronic active hepatitis, 58.2% in patients with primary liver carcinoma and markers of hepatitis B infections, and 34.9% in healthy carriers of HBsAg.     

Radioimmunoassay and some properties of human antibodies to hepatitis B core antigen

A solid-phase radioimmunoassay for antibodies to hepatitis B core antigen (anti-HBc) is described. Polystyrene beads coated with anti-HBc, hepatitis B core antigen prepared from pooled sera of humans infected with hepatitis B virus (HBV) and 125I-labelled anti-HBc were used for the test. Distinct patterns of development and changes of anti-HBc and their immunologic properties are all related to variations of other markers specific for HBV infections. Knowledge concerning the detailed features of the immune response to hepatitis B core antigen may provide deeper insight into the pathogenesis of HBV infections.     

A chemiluminescent, microparticle-membrane capture immunoassay for the detection of antibody to hepatitis B core antigen

A chemiluminescent, microparticle-membrane capture immunoassay (CLIA/MMC) for the detection of antibody to hepatitis B core antigen (anti-HBc) is described. The assay utilizes recombinant hepatitis B core antigen coupled to carboxylated latex microparticles. Human polyclonal IgG anti-HBc labelled with acridinium competes with antibody in the sample for a limited number of binding sites on the solid phase. After a 40 min incubation at 40 degrees C, the reaction mixture is transferred to a glass fiber capture membrane and washed. A chemiluminescent signal is produced by addition of alkaline peroxide and is quantitated on a semi-automated reader as described. The CLIA/MMC assay was compared with standard EIA and RIA procedures (Corzyme and Corab, respectively, Abbott Laboratories, North Chicago, IL). Assay sensitivities were RIA greater than CLIA/MMC greater than EIA. A population of 200 normal blood donors showed nearly identical distributions with the CLIA/MMC and RIA (mean = 11% inhibition, SD = 13% for both), compared with the EIA (mean = 13% inhibition, SD = 15%). With a selected plasma population (n = 307), the CLIA/MMC immunoassay showed an excellent correlation (r = 0.94) with both the EIA and RIA procedures. Association of anti-HBc reactivity near assay cutoffs with antibody to hepatitis B surface antigen suggested relative specificity in the order RIA greater than CLIA/MMC greater than EIA. The CLIA/MMC procedure, which can be readily automated, provides a non-istopic alternative to current EIA testing with performance more nearly equivalent to RIA.