Pitfalls in the study of hepatitis A

History of the Discovery of Hepatitis A Virus

Disease outbreaks resembling hepatitis A have been known since antiquity. However, it was not until World War II when two forms of viral hepatitis were clearly differentiated. After the discovery of Australia antigen and its association with hepatitis B, similar methodologies were used to find the hepatitis A virus. The virus was ultimately identified when investigators changed the focus of their search from serum to feces and applied appropriate technology.

Hepatitis-E-virus-associated antigen: improved detection in stools by protein Fv removal

ELISA detection of a hepatitis-E-virus-associated antigen (HEV-AAg) in stools was reappraised for its possible interference with a new Fab-binding factor, termed protein Fv, released during infectious hepatitis. Transaminase elevation, HEV-AAg discharge and Fv leakage appeared simultaneously in a Cercopithecus monkey inoculated with infected stools. Labelled normal, or immune human IgG, were compared with pre- and post-inoculation simian IgG, for HEV-AAg and Fv detection. Coated normal and patient human IgM were also compared to pre- and post-inoculation simian IgM in HEV-AAg and Fv capture assays. Simian IgM and beta-galactosidase-labelled simian IgG minimized Fv interference and appeared to be the best adapted system for HEV-AAg detection. Nevertheless, Fv was still the cause of false-positive interpretations in some cases; therefore adsorption with monoclonal IgM was required to ensure HEV specificity. The improved test was performed on stools from 30 Senegalese patients hospitalized for various sporadic attacks of viral hepatitis. HEV-AAg was detected in 6 out of 30 cases and no positivity was observed in patients suffering from hepatitis due to HAV, HBV, cytomegalovirus or Epstein-Barr virus. The specificity of the assay was confirmed by inhibition experiments with the sera from HEV-infected patients. Hence, this inhibition assay can also be used to detect serum antibodies to HEV-AAg.

Identification of enterically transmitted hepatitis virus particles by solid phase immune electron microscopy

Small 'featureless' viruses (less than 50 nm) are difficult to identify by routine immune electron microscopy techniques, particularly when they are mixed with debris from stool or cell culture extracts. A combination of conventional immune electron microscopy (IEM) and solid phase IEM (SPIEM) methodologies was used to identify hepatitis A virus (HAV) in stool and cell culture extracts and non-A non-B hepatitis (hepatitis E) in stool extracts. Compared with conventional IEM, the modified SPIEM method resulted in a significant increase in the number of particles observed. Several small aggregates, each containing 2-20 particles, were observed scattered randomly within most grid squares. Similar results were seen with stool extracts from hepatitis E (HEV) infections. The SPIEM method is a simple, highly sensitive specific assay that facilitates rapid identification of enteric hepatitis viruses. Several experiments were done to characterize the effects of altered physical environment within the assay and to evaluate potential modifications.

Rapid virus subunit visualization by direct sedimentation of samples on electron microscope grids

Airfuge direct ultracentrifugation of viral samples on electron microscope grids offers a rapid way for concentrating viral particles or subunits to facilitate their detection and study. Using the A-100 fixed angle rotor (30 degrees) with a K factor of 19 at maximum speed (95,000 rpm), samples up to 240 microliters can be prepared for electron microscopy observation in a few minutes: observation time is decreased and structural details are highlighted. Using latex spheres to calculate the increase in sensitivity compared to the inverted drop procedure, we obtained a 10- to 40-fold increase in sensitivity depending on the size of particles. Application of this technique to rubella virus permitted better visualization of viral membrane subunits on the particles. Rubella hemagglutinin immuno-stimulating complexes preparations were also better visualized and their morphology conserved after direct ultracentrifugation on the specimen grids. Similar observations are reported for respiratory syncytial virus associated subunits.

Characterization of a precipitating antigen detected in the serum of patients with viral hepatitis

During a search for the aetiological agent of non-A non-B hepatitis, a precipitating antigen was detected in the sera of some patients during the acute phase of their illness. The antigen was detected by agar gel diffusion using antibody from convalescent sera obtained from patients with non-A non-B hepatitis, and from haemophiliac sera. The antigen was usually detected early in the patient's illness, disappearing as liver function tests returned to normal. In some patients specific antibody appeared during the convalescent phase of the disease. The antigen does not appear to be specific for non-A non-B hepatitis, as it could be detected with similar frequency in patients with hepatitis A or hepatitis B and some patients with other liver disorders. Biochemical and biophysical studies suggest that the antigen is probably an abnormal lipoprotein produced as a result of acute liver damage.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Epidemiological and serological study of hepatitis A virus outbreaks in France: a comparison between immunoadherence and radioimmunoassay

An epidemiological study and the simultaneous evaluation of anti-HAV antibody using radio immunoassay (RIA) and immunoadherence hemagglutination assay (IAHA) was performed during three hepatitis A epidemics in the Tours area (France). Fifty-seven sera from 35 subjects with viral hepatitis type A and 16 sera from nine children who did not develop any clinical signs of hepatitis were studied. The more explosive epidemic occurred in an institution for mentally retarded children (attack rate 68%). The two major outbreaks observed were due to the introduction of the institutions of individuals infected with hepatitis A virus. Two out of three of the index cases had a seafood dinner three to four weeks before onset of jaundice. Sera taken one week after jaundice were always found to be anti-HAV positive by both RIA and IAHA, and sera taken more than three days before the appearance of jaundice were negative by both methods. Sera taken at the peak of the transaminase elevation were anti-HAV positive by RIA but only one out of two were positive by IAHA. The anti-HAV titre by RIA increased from the time of the appearance of jaundice and the highest titres, over 1/20000 were seen only after several months. Observations of subjects in close contact with patients who seroconverted without any manifestation of hepatitis, confirmed the existence of clinically mute infections.

Hepatitis A diagnosis in man: radioimmunoassay for hepatitis A antigen detection in faeces

A new radioimmunoassay (RIA) procedure using a double-sandwich technique was developed for the detection of hepatitis A antigen (HAV) in crude faecal extracts for patients involved in three outbreaks of type A hepatitis. Stools were obtained from 24 residents suffering from acute hepatitis A and from six children who remained asymptomatic throughout the epidemic. In addition, the HAV detection was performed in sera from 13 patients with hepatitis. HAV was detected in stools as early as five days before and as late as five days after the onset of jaundice. In this procedure, positive activity was only found in stools from patients with type A hepatitis, but not in negative controls. HAV was not detected in acute-phase sera. The double-sandwich RIA test used appears to be a reliable test for the large-scale screening of HAV in stool samples from patients suffering from type A hepatitis.

Serologic response in human hepatitis A: detection of antibody by radioimmunoassay and immune adherence hemagglutination

An indirect solid-phase radioimmunoassay (RIA) for detection of antibody to the hepatitis A antigen (anti-HAV) was developed using polystyrene pearls as the solid phase and hepatitis A antigen (HAAg) extracted from marmoset livers. This RIA was compared to an immune adherence hemagglutination assay (IAHA) which employed HAAg derived from the stools of chimpanzees collected during acute hepatitis A. Anti-HAV was detected in the sera of 15 humans with naturally acquired hepatitis A infection. Sensitivity and specificity were greater using the RIA, permitting the detection of anti-HAV as early as the time of onset of jaundice. Either seroconversion or a significant increase in the titer of anti-HAV was demonstrated following hepatitis A exposure in paired sera from six patients by both techniques. No significant difference in anti-HAV responses was noted between patients with icteric compared to anicteric hepatitis A or between children and adults with hepatitis A.

Application of a screening test for antibody the hepatitis B core antigen

Hepatitis B core antigen (HBcAg) was prepared from human liver tissue and used in an immunoelectro-osmophoresis screening test to detect antibody to HBcAg (anti-HBc) in patients with evidence of liver disease and in blood donors. With the exception of two immunosuppressed HBsAg carriers, anti-HBc was found in all cases of hepatitis B infection even when HBsAg was detectable only by radioimmunoassay. Non-specific reactions were observed in 'non-B' hepatitis but, in spite of this problem, antib-HBc screening was considered a useful addition to routine tests in the clinical hepatitis laboratory.

Studies of an outbreak of acute hepatitis A: II. Antibody changes to cytomegalovirus and herpersvirus

The acute and convalescent sera from 14 schoolchildren with acute hepatitis A were tested for antibody changes to 70 viral antigens. Marked decreases were noted in the levels of antibody to cytomegalovirus in 5 of the 14 children and in the levels of antibody to herpesvirus type 1 in 3. No such changes were noted in 9 sex- and age-matched healthy control children from the same classes.

Comparison of human fecal and serum parvo-like viruses

Parvovirus-like particles found in the sera of two blood donors had the size and appearance on electron microscopy of a virus (B19) found in the serum of a blood donor by Cossart et al. (1975), and those of a virus found in the feces of a normal subject. Antibody to these viruses was detected by immune electron microscopy and immunoelectro-osmophoresis in the sera of 50 children aged 10 to 15 years. Of these, 36% had antibody to the fecal virus, 36% had antibody to B19, and 54% had antibody to the two other serum viruses. The results of these tests suggest that serologically the three serum viruses were similar to one another, but that the fecal virus was distinct. The two blood donors had nonspecific symptoms at the time of viremia. Both donors had developed immunoglobulin M antibody to the virus when tested 3.5 and 4.5 weeks later, but no viruses were detected in the feces or urine.

Virus-like particles demonstrated by freeze-squeeze technique in acute-phase serum of patients with HBAg-negative hepatitis

Electromicroscopy of fluid, squeezed from excised and frozen precipitation lines obtained by immunoelectrophoresis in agarose gels of acute-phase sera from patients with HBAg-negative hepatitis, revealed particles of 22, 27, and 31-41 nm. These precipitates and particles were not present in normal human sera and disappeared from the sera of the patients after recovery. These particles were still demonstrable after two years' storage at -20 degrees C.

Faecal shedding of hepatitis-A antigen

Serial stool specimens from two individuals with experimental hepatitis-A infection were examined and the shedding pattern of hepatitis-A antigen (HAAg) was determined by immune electron microscopy. HAAg particles were detected at least 5 days before the development of abnormal transaminase levels and jaundice, but not later than the day of peak transaminase levels. The pattern of early faecal shedding of HAAg particles correlated well with the early infectivity of faeces and accorded with the suggestion that HAAg is involved in the aetiology of hepatitis-A infection.