Enzyme-immunoassay in diagnosis of hepatitis with emphasis on the detection of "e" antigen (HBeAg)

Detection technology and clinical applications of serum viral products of hepatitis B virus infection

Viral hepatitis, caused by its etiology, hepatitis virus, is a public health problem globally. Among all infections caused by hepatitis-associated viruses, hepatitis B virus (HBV) infection remains the most serious medical concern. HBV infection particularly affects people in East Asia and Africa, the Mediterranean region, and Eastern Europe, with a prevalence rate of > 2%. Currently, approximately 1 billion people worldwide are infected with HBV, and nearly 30% of them experience chronic infection. Chronic HBV infection can lead to chronic hepatitis B (CHB), liver cirrhosis, and hepatocellular carcinoma (HCC), resulting in the related death of approximately 1 million people annually. Although preventative vaccines and antiviral therapies are currently available, there is no cure for this infection. Clinical testing is not only the gateway for diagnosis of HBV infection, but also crucial for judging the timing of medication, evaluating the effect of antiviral therapy, and predicting the risk of relapse after drug withdrawal in the whole follow-up management of hepatitis B infected persons. With advances in detection technology, it is now possible to measure various viral components in the blood to assess the clinical status of HBV infection. Serum viral products of HBV infection, such as HBV DNA, HBV RNA, hepatitis B surface antigen, hepatitis B e-antigen, and hepatitis B core-related antigen, are non-invasive indicators that are critical for the rapid diagnosis and management of related diseases. Improving the sensitivity of monitoring of these products is essential, and the development of corresponding detection technologies is pivotal in achieving this goal. This review aims to offer valuable insights into CHB infection and references for its effective treatment. We provide a comprehensive and systematic overview of classical and novel methods for detecting HBV serum viral products and discusses their clinical applications, along with the latest research progress in this field.

HBsAG transmission from a cardiac surgeon incubating hepatitis B resulting in chronic antigenemia in four patients

A cardiac surgeon experienced an uneventful course of acute hepatitis B. HBsAg was transmitted to 11 persons: 5 of 72 patients operated on during his incubation of hepatitis B, three relatives of the infected patients, one laboratory technician, and two of the surgeon's family members. Two years later, 4 of the 5 operated patients are still infectious, whereas the 7 non-operated persons have cleared their antigenemia. This study demonstrates the significant risk of hepatitis B transmission from a cardiac surgeon incubating the disease. Furthermore, it indicates that patients who have been infected during open heart surgery and cardiopulmonary bypass run a particular risk of becoming chronic HBs antigen carriers.

Enzyme Immunoassay (EIA)/Enzyme-Linked Immunosorbent Assay (ELISA)

This brief note addresses the historical background of the invention of the enzyme immunoassay (EIA) and enzyme-linked immunosorbent assay (ELISA). These assays were developed independently and simultaneously by the research group of Peter Perlmann and Eva Engvall at Stockholm University in Sweden and by the research group of Anton Schuurs and Bauke van Weemen in The Netherlands. Today, fully automated instruments in medical laboratories around the world use the immunoassay principle with an enzyme as the reporter label for routine measurements of innumerable analytes in patient samples. The impact of EIA/ELISA is reflected in the overwhelmingly large number of times it has appeared as a keyword in the literature since the 1970s. Clinicians and their patients, medical laboratories, in vitro diagnostics manufacturers, and worldwide healthcare systems owe much to these four inventors.

Rapid and accurate viral diagnosis

In recent years, there has been increased recognition of the importance of viral infections. In addition, new antiviral agents have become available. These factors have led to a marked increase in utilization of viral diagnostic services. In this review, both conventional and rapid methods for viral diagnosis are presented, with emphasis on recent advances. The antiviral agents currently available and the major drugs under investigation are also briefly discussed. It is hoped that this review will serve as a useful adjunct for the management of patients with virus infections.

Efficacy of post-exposure prophylaxis with hepatitis B immunoglobulin in Norway

The efficacy of hepatitis B immunoglobulin (HBIG) in preventing infection by hepatitis B virus (HBV) after exposure to blood or blood-containing secretions that carried hepatitis B surface antigen (HBsAg), was studied in an uncontrolled trial in Norway from 1976-1983. Of the 177 HBIG recipients, followed up for 5-24 months, 166 were exposed by needle-stick, splash on mucous membranes or open wounds, sexual contact or medical investigation. With few exceptions, this group was given a single injection of 1250 IU of antibody to HBsAg (anti-HBs) within 7 days after exposure. One person developed clinical hepatitis B (HB) of short duration and two others developed anti-HBs. Six infants with perinatal exposure were injected with three or four doses of about 1250 IU anti-HBs at intervals of 2-3 months. The first dose was given immediately after birth. One child developed clinical HB at the age of 14 months and recovered. Of five patients exposed by blood transfusion, four developed clinical HB; the fifth apparently developed passive-active immunity. One of the four probably became an HBsAg carrier. These patients, except the one without clearance of HBsAg, received one to seven doses of HBIG within 2 days after exposure. Administration of HBIG after needle-stick and similar types of exposure, as well as administration to infants at risk of contracting HB, seems to be of great value.

Prevalence and clinical effects of delta agent. Infections in Norwegian population subgroups

The distribution of antibodies against the delta agent was studied in different groups of hepatitis B patients in Norway. Such antibodies were detected only in drug addicts, predominantly among chronic HBsAg carriers. The results support the notion that the delta agent was introduced into Scandinavia in 1970-75. Although the proportion of anti-delta positive individuals among chronic HBsAg carriers increased, the annual increase of new anti-delta carriers was essentially stable. One death caused by hepatic failure was registered among 43 anti-delta negative and none among 21 anti-delta positive chronic HBsAg carrier addicts.

Viral hepatitis markers in Thai blood donors

1,410 voluntary blood donors from Bangkok were investigated by radioimmunoassay for HBsAg, anti-HBs, anti-HBc, HBeAg, anti-HBe and anti-HAV. An HBsAg carrier state was observed in 10.7% of whom 42.1% were HBeAg positive and 40.2% had anti-HBe. Antibody prevalences (except anti-HBe) rose with increasing age. The occurrence of hepatitis markers did not vary significantly between donors living along the canals and those living in the Greater Bangkok area.

Enzyme immunoassays in which biotinillated beta-lactamase is used for the detection of microbial antigens

The performance characteristics of enzyme immunoassays are determined to a great extent by the enzyme-substrate system utilized for the immunoassay. Beta-lactamases (penicillin amido-beta-lactamhydrolase EC 3.5.2.6) offer a number of advantages which might make them useful in immunoassay systems. We linked beta-lactamase from Bacillus cereus with biotin and used the biotinillated enzyme to devise immunoassay systems for the detection of a number of microbial antigens. An assay system in which antibodies to the polyribitol phosphate antigen of Haemophilus influenzae type b were used was capable of detecting between 0.4 and 1.6 ng of that antigen. Similarly, an assay in which antibodies to the common antigens of adenoviruses and biotin-linked beta-lactamase were used was capable of detecting between 1 and 10 50% tissue culture infective doses of a strain of enteric-type adenovirus. When applied to the detection of rotavirus, a similar system in which biotinillated beta-lactamase was used was capable of detecting small amounts of antigen in a standard rotavirus preparation. This assay could also detect virus in 36 of 37 stool specimens from children with rotavirus gastroenteritis. The positive specimens could easily be distinguished from negative ones by the naked eye, and a permanent record of the qualitative results could be obtained by the use of a standard office photocopying machine. Beta-lactamases have promise for use in practical enzyme immunoassay systems, especially in situations in which expensive colorimetric instrumentation is not available.

Hepatitis B e-antigen titres for evaluating infectivity during hepatitis B virus infection

By means of an ELISA the level of hepatitis B e-antigen (HBeAg) titre was determined in 51 patients with acute and 123 patients with persistent hepatitis B virus (HBV) infection. We also investigated 120 sera of these patients for infectivity by detecting HBV-specific DNA polymerase (DNA-P). Additional determination of the HBeAg titre revealed that the detection of HBeAg at a dilution of at least 1:50 correlates with the detection of DNA-P in 95% of cases, while in sera with an HBeAg titre of 1:25 or less DNA-P is only detectable in up to 5% of cases. Since the detection of DNA-P indicates high infectivity, certain titres of HBeAg can be employed to differentiate three different degrees of infectivity: (1) Sera without HBeAg show no or only little infectivity; (2) sera containing HBeAg greater than or equal to 1:50 are highly infectious; (3) HBeAg titres up to 1:25 indicate a medium degree of infectivity. These three markers for different degrees of infectivity were applied to study the course of infectivity during acute and persistent forms of HBV infection. In acute hepatitis B the period for the elimination of HBeAg is independent of the HBeAg titre in the first serum sample. In all cases the elimination of HBeAg in acute hepatitis B did not exceed 4 months. Patients with persistent HBV infection and an initial HBeAg titre greater than or equal to 1:50 remained at this high degree of infectivity for at least 18-30 months in 70% of cases. Only 30% of this collective showed a decrease in infectivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Dane particle DNA polymerase and HBeAg: impact on clinical, laboratory, and histologic findings in hepatitis B-associated chronic liver disease

Fifty patients with chronic HBs antigenemia and Dane particle-associated DNA polymerase and HBeAg in their serum were contrasted to 46 HBsAg positive patients who had neither serum DNA polymerase or HBeAg. The time from acute onset and the duration of antigenemia were longer in patients who were DNA polymerase and HBeAg negative than in those who had both serum markers. Cirrhosis, hypoalbuminemia, and sequelae of chronic liver disease were more common in DNA polymerase, HBeAg negative patients than in those who were positive. These findings are consistent with the hypothesis that active viral replication is an early, albeit prolonged stage in the development of advanced HBsAg-associated liver disease.

An enzyme immunoassay for hepatitis B e-antigen and antibody

A solid-phase enzyme-linked immunoassay for the detection of hepatitis B e-antigen (HBeAg) and antibody (anti-HBe) was developed and compared with rheophoresis and radioimmunoassay (RIA). The enzyme-immunoassay (EIA) was similar to RIA in sensitivity and was approximately 1000-fold more sensitive than rheophoresis for HBeAg, and approximately 6000-fold more sensitive than rheophoresis for anti-HBe.

Development of an enzyme-linked immunosorbent assay (ELISA) for hepatitis B e antigen and antibody

Horseradish peroxidase has been conjugated with human immunoglobulin containing antibody to hepatitis B e antigen (anti-HBe). This was used in a solid-phase 'sandwich' enzyme-linked immunosorbent assay designed for reading by eye, to test sera for HBeAg and anti-HBe. Optimum conditions for preparing the conjugate and for performing the test are described. Results of testing hepatitis B surface antigen (HBsAg)-positive sera were compared with those obtained using a sensitive solid-phase radioimmunoassay. The enzyme assay provided a simple and sensitive method of testing for HBeAg and anti-HBe, and correlated well with the radioimmunoassay.

Detection and significance of anti-HBc in the blood bank; preliminary results of a controlled prospective study

It has been suggested that post-transfusion hepatitis B (PTHB) may occur after transfusion with blood negative for hepatitis B surface antigen (HBsAg) but positive for antibody against hepatitis B core antigen (anti-HBc). We are currently conducting a controlled prospective study of recipients of such blood to investigate this possibility. Blood donors were routinely screened for HBsAg by radioimmunoassay (RIA) and those found negative were tested for anti-HBc by RIA. The HBsAg negative, anti-HBc positive donors were then tested by antibody directed against HBsAg by RIA, antibody directed against hepatitis B 'e' antigen by enzyme-immunoassay and for the liver enzymes SGOT and SGPT. To date,, follow-up has been completed in the recipients of 141 anti-HBc positive blood donors and in a control group of the recipients of 141 anti-HBc negative blood donors. All the recipients were bled repeatedly with intervals of 4--5 weeks up to 7 months post-transfusion. Currently, no clear-cut seroconversion was observed in recipients of either group for any of the antibody markers of HBV infection. While none of the 141 recipients of anti-HBc negative blood became positive for HBsAg, 3/141 recipients of anti-HBc positive blood acquired HBsAg and developed clinically manifest post-transfusion hepatitis B.

Comparison of enzyme-labelled F(ab')2 and IgG conjugates in an enzyme-immunoassay for hepatitis B 'e' antigen

An improved enzyme-immunoassay (EIA) for the detection of hepatitis B 'e' antigen (HBeAg) and its corresponding antibody is described. The present test is as sensitive as the previous one but it is more specific as demonstrated by testing donor/recipient sera, donor plasmas and patients sera. Interference by antibody against hepatitis B surface antigen (HBsAg) did not occur due to the use of HBsAg-free reagents. Interference by rheumatoid factor could be avoided by using enzyme-labelled F(ab')2 rather than IgG conjugates. The application of an F(ab')2 conjugate, however, introduced other non-specific reactions, particularly in sera from patients with (autoimmune) liver disorder. Further study into the applicability of F(ab')2 conjugates is therefore indicated.

HBeAg, anti-HBe and anti-HBc IgM in patients with hepatitis B

Using radioimmunoassay, 70 consecutive patients with acute type B hepatitis were investigated for the presence of HBeAg and anti-HBe. The results indicate that HBeAg is found constantly in the early phase of acute hepatitis B. The presence of HBeAg for more than 10 weeks after the onset of symptoms seems to be of prognostic value and signifies the development of a chronic HBsAg carrier state. Anti-HBc titres were determined in 40 patients with acute hepatitis B with differing outcomes of their disease. The anti-HBc titres were generally above 1:100 at the time of admission to the hospital and in those patients who remained HBsAg-positive the anti-HBc titres remained about 1:1000 during the 12 month follow-up period. Anti-HBc IgM was constantly present in 42 patients with acute hepatitis B and was found to persist from 7 months to several years in those patients who became chronic HBsAg carriers. Anti-HBc IgM was found to persist for more than 2 years in five of the 12 patients investigated who developed chronic liver disease in spite of an early clearance of HBsAg.

Follow-up of blood donors positive for hepatitis B surface antigen

From 1973 to 1977 in Amsterdam the incidence of hepatitis B surface antigen (HBsAg) in blood donations from new donors was 0.224 and from known donors 0.034%. 65 donors, previously found positive for HBsAg, were re-examined. Persistence of HBsAg in new donors (28 of 31) occurred significantly (p less than 0.0005) more often than in known donors (15 of 34). All carriers were classified into HBeAg (21%) or anti-HBe (79%) by a sensitive Elisa technique. Abnormal liver function tests (LFTs) were observed in 30% of the carriers and were significantly (p less than 0.005) more often found in HBeAg than in anti-HBe-positive carriers. When the LFTs remained abnormal, in almost all (8 of 9) carriers moderate to severe histological liver disease was diagnosed.

Double-blind study of leucocyte interferon administration in chronic HBsAg-positive hepatitis

In a double-blind study human leucocyte interferon was given for six weeks to 8 of 16 patients with chronic HBsAg-positive hepatitis. In the first week 12 x 10(6) reference units were administered daily, and thereafter the dose was halved every week. During the first two weeks leucopenia was observed in 6 of the 8 interferon-treated patients. Apart from a drop in DNA-polymerase activity in the first week, no effect was found on indices of hepatitis-B-virus infection.

Quantitative relationship between HBeAg and DNA polymerase activity in sera from patients with chronic active hepatitis during a three-month period

In eight patients with biopsy-confirmed chronic active hepatitis (CAH), hepatitis B e antigen (HBeAg) levels and DNA polymerase (DNA-P) activity were assayed three times a week for six weeks and once a week for another six weeks. HBeAg levels were rather constant, whereas DNA-P activity fluctuated. No correlation was observed between the quantities of HBeAg and DNA-P activity. An unexpected fluctuation in DNA-P activity was noted in all patients after an influenza vaccination.

The occurrence of antibody markers of hepatitis B virus infection in an HBsAg-negative blood donor population

Anti HBs, anti-HBc and anti-HBe were tested in blood donors negative for HBsAg by radio- and enzyme-immunoassay. In this population 6.4% of the donors were positive for at least one type of antibody to HBV: 4.0% for anti-HBs, 2.3% for anti-HBc and 4.3% for anti-HBe. Two sera (0.2%) were exclusively positive for anti-HBc, eight sera (2.2%) were weakly positive only for anti-HBe. Further studies of the infectivity of such samples might be of interest.