Detection by radioimmunoassay of IgM class antibody to hepatitis B core antigen: a comparison of two methods

Comparison of three immunoassays for the detection of anti-HHV6

Sera from 96 blood donors were tested for antibody to human herpesvirus 6 by indirect immunofluorescence (IF), circle immunoassay (CIA) and competitive radioimmunoassay (RIA). The correlation between the three assays was good but the CIA and competitive RIA were more sensitive for the detection of HHV6 antibody than indirect IF. The crossreaction of HHV6 antibody with that to the other human herpesviruses was also studied in this blood donor group. No correlation was found between antibody to human herpesvirus 6 by any of the methods described and antibody to any of the other human herpesviruses in these sera.

Diagnosis of hepatitis A and B by testing saliva

The use of salivary samples to diagnose acute viral hepatitis was investigated. Tests for IgM antibody to hepatitis A virus (anti-HAV) on 29 acute-phase samples from serologically confirmed cases of hepatitis A were strongly reactive. Follow-up samples indicated that IgM anti-HAV persisted at moderate levels for 2-4 months and was not usually detectable thereafter. The ratio of IgM to IgG anti-HAV (RIA index) correlated closely with the interval from onset of infection. Significant levels of IgM anti-HAV were not detected in the saliva of 103 IgG anti-HAV positive and 102 IgG anti-HAV negative individuals nor of 4 individuals with hepatitis B. Similarly, IgM anti-HBc was present in the saliva of acute cases of hepatitis B, but not in the saliva of 25 IgG anti-HBc positive and 85 IgG anti-HBc negative individuals, nor of 24 individuals with recent hepatitis A. It is concluded that saliva is a convenient and satisfactory alternative to serum for the diagnosis of hepatitis A infection.

Late onset hepatic failure: clinical, serological and histological features

The clinical, laboratory and histological features of 47 patients with what is defined as late onset hepatic failure are reviewed. Twenty-five of the patients were female and 22 male with a median age of 45 years. Hepatic dysfunction was severe as evidenced by the prolongation of prothrombin time (median = 32 sec, range = 17 to 120 sec). In only four cases was a viral etiology proven (2 hepatitis B, 2 hepatitis A) although the similarity of the clinical features to patients with fulminant viral hepatitis--apart from the longer period of illness prior to the onset of encephalopathy (median = 9 weeks, range = 8 to 24 weeks)--made non-A, non-B infection a possibility in the remainder. There were also similarities to chronic active hepatitis with low titer antibodies to smooth muscle or antinuclear factor in 17% and elevation of the serum IgG in 49%. Liver biopsy in 5 of 8 survivors more than 1 year after initial presentation showed chronic active hepatitis in three. Lobular inflammatory infiltrate, bridging necrosis and multilobular collapse were the features of the acute stage of illness in both the survivors and fatal cases. The patients given corticosteroids did not have a statistically significant improvement in survival, and overall mortality for the series was 81%. Hepatic transplantation, successfully performed in one patient, would appear to offer the best chance of survival for the majority of these patients.

[Anti-HBc IgM in acute and chronic hepatitis B virus infection]

Hepatitis B core antigen (HBcAg) synthesized in E. coli was used for determination of immunoglobulin M class-specific antibodies against HBcAg. It was found that 98% of cases with acute hepatitis B surface antigen (HBsAg) positive hepatitis type B were anti-HBc immunoglobulin M (IgM) positive. Atypical hepatitis B was detected in 33% of anti-HBc-positive HBsAg-negative cases with acute hepatitis. Anti-HBc IgM was positive for 6 months in acute resolving hepatitis type B, whereas cases resulting in chronic hepatitis B remained anti-HBc IgM-positive for up to 900 days. Chronic HBsAg carriers with severe liver disease had anti-HBc IgM more often than individuals with minor liver damage; 83% of HBsAg-positive liver cirrhoses, 63% of chronic aggressive hepatitis, 50% of HBsAg-positive liver carcinoma, but only 17% of chronic persistent hepatitis or 7% of healthy blood donors were anti-HBc IgM-positive. Determination of anti-HBc IgM is useful in detecting atypical hepatitis B virus infections without HBsAg in serum and, with some restrictions, in discriminating acute and chronic hepatitis type B.

BK virus specific IgM responses in cord sera, young children and healthy adults detected by RIA

An IgM capture solid-phase radioimmunoassay (MACRIA) for BK virus (BKV) specific IgM is described. This test was found to be more sensitive in detecting BKV specific IgM than both haemagglutination inhibition and immune electron microscopy with serum fractions from sucrose density gradients. The use of this specific assay allowed large numbers of sera to be examined with ease so that the distribution of BKV specific IgM in different populations could be studied more fully. BKV specific IgM was detected in 11/300 sera from London blood donors, in 24/114 sera from children aged between 2 and 11 years admitted to a paediatric unit and 14/79 sera taken from children aged between 2 and 5 years for the investigation of anti-streptolysin 0 titres. BKV specific IgM was not detected in 404 cord sera examined to investigate the transplacental transmission of BK virus.

Specificity and sensitivity of the IgM capture immunoassay: studies of possible factors inducing false positive or false negative results

The specificity and sensitivity of the IgM-capture immunoassay (IgM-CI) were evaluated for detection of rubella specific IgM and hepatitis B core (HBc) specific IgM. For rubella specific IgM, antibodies bound to the solid phase were detected by haemadsorption and for HBc specific IgM, by using HBc antigen (HBcAg) and radiolabelled IgG anti-HBc. Rheumatoid factor (RF) was found to interfere in the test for HBc specific IgM because IgM-RF bound to the solid phase reacted with aggregated radiolabelled HBc specific IgG. This false positive reaction did not occur when radiolabelled F(ab')2 was used instead of the whole IgG molecule. HBcAg purified from biological fluids might be coated with host IgG and under these conditions, HBcAg could react with RF. It was also demonstrated that high levels of IgG antibodies could interfere with IgG anti-mu coated-surface by means of non-immunological protein-protein interactions. In fact, IgG did not interfere in the rubella assay, whereas it did in the very sensitive anti-HBc test. To prevent this false-positive reaction, different dilution media were tested. Only the addition of non-specific IgG and fetal calf serum (FCS), to the dilution medium, seems to improve the specificity of the test. Furthermore, in order to decrease this non-specific IgG-IgG interaction and an occasional prozoning phenomenon, the dilution of serum to be tested was taken into account. Parameters considered to decrease sensitivity were also studied. RF, anti-F(ab')2 antibodies and non-specific IgM did not decrease significantly the sensitivity of the assay.

A user's guide to the indirect solid-phase radioimmunoassay for the detection of cytomegalovirus-specific IgM antibodies

In this review full laboratory details are given of a solid-phase indirect radioimmunoassay for the detection of specific IgM antibodies against cytomegalovirus. Practical advice is given on readily available commercial sources of reagents, a simple iodination procedure, the rapid dilution of sera under test and calculation of the results with a computer program available from the authors. Problems encountered with the assay are also detailed such as interference by rheumatoid factor, deterioration of the radiolabel and high background binding found with some sera. If these problems are avoided by the methods given in the text then the radioimmunoassay has been shown to give results of 100% specificity with 89% sensitivity for detecting congenital infection and 92% sensitivity for identifying primary cytomegalovirus infection in pregnant women.

Use of hepatitis B core antigen produced in Escherichia coli to detect immunoglobulin M specific antibodies in an enzyme-linked immunosorbent assay

The antigenic activity of HBcAg produced in Escherichia coli and HBcAg from human liver was compared in a mu-specific solid-phase antibody-capture assay for detection of anti-HBc-IgM. HBcAg from liver could be detected in dilutions up to 1:3, HBcAg from Escherichia coli in dilutions up to 1:10,000. Using HBcAg from Escherichia coli, sera from five patients with acute resolving hepatitis B and sera from four patients with acute hepatitis B who had developed chronic liver disease were tested for anti-HBc-IgM in ELISA. IgM fractions separated out of the same sera by immunoaffinity chromatography were tested for anti-HBc-IgM using a commercially available test. The results were in good agreement with those obtained by ELISA. Anti-HBc-IgM could be detected up to 900 days after onset of disease. Different groups of patients were tested for presence of anti-HBc-IgM in ELISA. Fifty-nine of 60 patients with acute hepatitis B were positive for anti-HBc-IgM at onset of illness. Ten of 16 patients with chronic aggressive hepatitis and seven of 23 HBsAg positive dialysis patients were also positive for anti-HBc-IgM, whereas only two of 12 patients with chronic persistent hepatitis and one of 15 HBsAg positive blood donors ("healthy" carriers of HBsAg) had detectable anti-HBc-IgM.

A comparison of enzyme-immunoassay and radioimmunoassay for detection of hepatitis A virus and antibodies against hepatitis A virus

A direct comparison has been made of tracers labelled with an enzyme and with 125I in solid phase enzyme-immunoassay (EIA) and solid phase radioimmunoassay (RIA) for the detection of hepatitis A virus (HAV) antigen and antibodies to HAV. By comparing the binding capacity of peroxidase-labelled anti-HAV-IgG and anti-HAV-F(ab)2 fragments tracers, anti-HAV-IgG was found to have a higher binding capacity than anti-HAV-F(ab)2 fragments in both EIA and RIA. For EIA 16.25-fold more anti-HAV-IgG was needed for one test probe compared to RIA and 32.5-fold more anti-HAV-F(ab)2 fragments. For the detection of HAV antigen from stool preparations and IgG and IgM antibodies against HAV, there were only minor quantitative differences in titre. EIA was as sensitive as RIA.

Immunoglobulin M antibodies against hepatitis B core antigen in patients with chronic hepatitis B infection

A batch of sera obtained from subjects with acute hepatitis B virus (HBV) infection, chronic carriers of hepatitis B surface antigen (HBsAg) who were either asymptomatic or who had chronic active hepatitis, and 32 sera from patients with HBsAg negative chronic active hepatitis were examined for the presence of antibodies against hepatitis B core antigen (anti-HBc) by radioimmunoassay (RIA). Sera containing anti-HBc were fractionated on sucrose density gradients to separate immunoglobulin M (IgM) and the titre of anti-HBc IgM was determined. In patients with acute HBV infection, anti-HBc IgM was detected during the acute phase of the illness with titres ranging from 1:128 to 1:4,096 (geometric mean titre 1:709). The titre of anti-HBc IgM fell rapidly over the following months and in most patients persisted at low levels for several years. Anti-HBc IgM was also detected in subjects with chronic HBV infection but with significantly lower titres. In asymptomatic carriers, anti-HBc IgM titres ranged from 1:4 to 1:32 (geometric mean titre 1:12), whilst carriers with chronic active hepatitis had titres ranging from 1:4 to 1:128 (geometric mean titre 1:35). By using a standardized assay procedure, the titre of anti-HBc IgM in a patient's serum may be of value in differentiating between acute and chronic HBV infection.

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.

Clinical and prognostic differences in fulminant hepatitis type A, B and non-A non-B

In 73 patients with fulminant viral hepatitis, non-A non-B hepatitis (NANB) was most common (43.8%), with hepatitis type A (HAV) diagnosed in 31.5% and hepatitis type B (HBV) in 24.7%. The non-A non-B group had a significantly longer duration from the onset of symptoms to the appearance of encephalopathy (median 21 days) compared with the HAV and HBV groups (medians 10 and seven days, p less than 0.01 and p less than 0.005 respectively). In the HAV group the severity of liver damage, judged by the maximum prolongation of the prothrombin time, was significantly less than in the HBV group (58 and 150 seconds prolonged respectively, p less than 0.005), and cerebral oedema was significantly less frequent (39% and 72% respectively, p less than 0.05). Consistent with this, the survival rate was higher in the HAV group (43.4%) compared with the HBV group (16.6%) and NANB group (9.3%) (p less than 0.005). These variations in presentation and clinical course may be a consequence of differences in the pathogenesis of the hepatic necrosis.

Diagnostic assays with monoclonal antibodies for the human serum parvovirus-like virus (SPLV)

Monoclonal antibodies to the serum parvovirus-like virus (SPLV) were prepared by the hybridoma technique. They provided an antibody reagent which was used to develop solid phase antibody-capture assays for anti-SPLV IgM and IgG and for SPLV antigen. These assays were more sensitive than those based on human convalescent antibody as a reagent, and were more economical in the use of SPLV antigen. Their use enabled the serological responses to SPLV to be studied more fully and their sensitivity revealed the extent of SPLV infection. SPLV antigen was detected in four patients by both counter-immuno electrophoresis (CIE) and radioimmunoassay (RIA) and in two others by RIA alone. Parvovirus particles were seen in all six by electron microscopy. The anti-SPLV IgM response was measured in patients infected by SPLV. It was strong 5-18 days after the onset of illness, then declined and was only detectable in trace amounts after 6 months. Anti-SPLV IgG was also formed early, and persisted for at least 6 months. In a survey of 310 blood donors anti-SPLV was detected in 134 (43%) by CIE, but in 190 (61%) by IgG antibody capture RIA.

Serological markers in fulminant hepatitis B

Serological markers for hepatitis B virus infection have been examined in 34 patients with acute hepatitis B, 17 of whom developed fulminant hepatic failure. Hepatitis B surface antigen concentrations were significantly lower and hepatitis Be antigen was less frequently detectable in patients with fulminant hepatic failure compared with those with acute hepatitis (median 0.64 micrograms, range 16-0 and median 32 micrograms and range 100-4 micrograms respectively, p less than 0.001; HBeAg detected in 12% and 88% respectively, p less than 0.001). The IgM component of hepatitis B core antibody was significantly higher in the patients with fulminant hepatic failure with median values of 500 IU/ml compared with those with uncomplicated hepatitis (median 202 IU/ml, p less than 0.05 Wilcoxon's rank test). Three patients who developed a fulminant course had detectable levels of either anti-HBs or anti-HBe. These results are consistent with enhanced antibody responses to all three hepatitis B virus antigens and more rapid clearance of the latter during fulminant hepatic failure.

Serodiagnosis of recent hepatitis B infection by IgM class anti-HBc

The time sequence, relative reactivity, and persistence of anti-HBc IgM were assessed in patients with HBsAg-positive viral hepatitis. A solid-phase immunoassay was developed using the IgM capture procedure with anti-mu-coated polystyrene beads. HBcAg was purified from serum Dane particles and used as a probe with 125I-labeled anti-HBc IgG. This immunoassay exhibited a pronounced prozoning phenomenon, and relative titers of sera differed widely depending upon the dilution of serum tested. When all sera were tested at 1:5,000 dilution, results were comparable in different patient groups. Anti-HBc IgM persisted at detectable levels for up to 2 years, and it was necessary to establish relative titers to discriminate current from remote infections. A cut-off assay value was established, and in 12 cases of acute hepatitis B virus (HBV) infection, antibody exceeded this value for about 6 months after onset of HBs antigenemia. A similar profile of anti-HBc IgM persistence was observed in seven patients who developed an HBsAg chronic carrier state. Long-term viral replication did not sustain elevated IgM class-specific antibody levels. The studies suggest that anti-HBc IgM analyses may be useful for differentiating recent and current HBV infections from remote infections, eliminating HBV as the agent for non-A, non-B hepatitis in asymptomatic HBsAg carriers, and detecting HBV as the etiologic agent during silent (HBsAg negative) infections.

Complexes between HBsAg and IgM in serum of patients with acute hepatitis

HBsAg bound to IgM was measured in the serum of HBsAg carriers with acute hepatitis using a radioimmunoassay based on selective absorption of IgM on solid phase coated with antiserum to human IgM. HBsAg/IgM was detected in 94 (100%) patients with acute type B hepatitis during the acute phase of infection and persisted after the fourth week only in 13 of them, who developed chronic liver disease. HBsAg/IgM was detected only in 1 patient out of 15 carriers of the HBsAg with superimposed non-B hepatitis. No activity was found in serum of 20 patients with acute HBsAg-negative hepatitis. The nature of the IgM component of the complex is uncertain, however, blocking experiments of the HBsAg/IgM reaction with polymerized human albumin suggest that the IgM component of the complex might represent antibody to the denatured protein. Persistent HBsAg/IgM complex detection in patients with acute type B hepatitis provides a useful tool to predict transition of HBV infection to chronicity. Its absence in patients with acute HBsAg-positive hepatitis is indicative of non-B hepatitis in chronic carriers of the HBsAg.

A comparison of antibody capture radio- and enzyme immunoassays with immunofluorescence for detecting IgM antibody in infants with congenital rubella

IgM antibody capture radioimmunoassay (MACRIA) and enzyme immunoassay (MACEIA) were compared with immunofluorescence (IF) for detecting specific IgM antibody in 99 sera from 76 infants with confirmed congenital rubella, and 61 sera from a comparative group of 59 infants who had miscellaneous abnormalities but in whom congenital rubella was not confirmed. All of 35 specimens collected from confirmed cases within 12 weeks of birth were positive by all three methods and all but one of 17 specimens collected after the age of 18 months were uniformly negative. At intermediate ages discrepancies occurred in 18 specimens, of which eight were positive and 10 negative by IF. Three of these 18 specimens were negative by both antibody capture procedures but showed weak fluorescence; the other 15 were negative by MACEIA, but positive by MACRIA which appears to be the more sensitive of the antibody capture methods. Sera from five infants in the comparative group were clearly positive by all three methods. These five infants were probably congenitally infected with rubella. Sera from the other 54 infants were negative, except for one that gave a weakly positive result by MACRIA alone. Antibody capture procedures offer several advantages over previous methods for detecting IgM antibody. Although MACRIA was found to be slightly more sensitive than MACEIA, the greater stability of the enzyme label, together with the possibility of both visual and quantitative assessment, could make MACEIA the method of choice for detecting rubella-specific IgM.

Detection of antibody to varicella-zoster virus by competitive and IgM-antibody capture immunoassay

A simple, sensitive, and specific competitive solid phase immunoassay for antibody to varicella-zoster virus (anti-VZV) is described. The assay uses reagents that can easily be prepared and is sparing of viral antigen. Using a solid phase coated with sheep IgG from a serum raised against human mu-Fc, the same reagents will accurately detect anti-VZV IgM. The competitive assay divided sera from children from adults into immune and nonimmune groups that closely correlated with a history of previous VZV illness. It was not affected by the presence or absence of antibody to other herpes viruses. The IgM antibody capture assay demonstrated the presence of anti-VZV IgM in sera from patients with both varicella and zoster and gave negative results in patients with infections unrelated to VZV and in healthy blood donors.