An enzyme-linked immunoassay for the possible detection of non-A, non-B viral antigen in patients with epidemic viral hepatitis

Atypical strain of hepatitis E virus (HEV) from north India

Hepatitis E virus (HEV) infection was detected during an epidemic in North India. Virus particles present in the stool of an acutely ill patient (YAM-67) was transmitted intravenously into rhesus monkeys (M. mulata) and orally to a human volunteer. Virus-like particles (VLPs) of 32-34 nm were detected in the bile of monkeys and in the stools of the human volunteer by means of solid phase immune electron microscopy (SPIEM) with acute homologous and heterologous sera. The VLPs were confirmed to be HEV by a reverse transcription polymerase chain reaction (RT-PCR). Virus-like particles from human volunteer stools were passaged further into rhesus monkeys. A bimodal rise in aminotransferase levels were observed in the animals, and liver histopathology indicated mild to severe form of hepatitis. Further, SPIEM and RT-PCR analysis in monkey bile revealed presence of virus from 15 to 45 days post-inoculation. Rechallenge of the animals 6 months after recovery with the same viral inoculum failed to produce abnormal liver function tests indicating the presence of protective immunity during this period. The VLPs in the stool from the patient (YAM-67) with epidemic hepatitis were found to retain infectivity even after several cycles of freeze-thawing and exposure at 37 degrees C for 2 days. Moreover, these VLPs from the patient, human volunteer, and monkeys did not react with an anti-HEV chimpanzee serum from NIH, Bethesda, MD. These findings indicate that this North India isolate of HEV is an atypical strain of HEV. The present study further validates that the rhesus monkey is a suitable experimental model for HEV.

Localization of a new enteric non-A, non-B [HEV] virus in target organ liver

Thirteen Macaca mulatta monkeys were used for transmission of enteric non-A, non-B hepatitis virus (HEV) by the portal vein (PV) route. All these animals developed changes which are found in self-limiting acute viral hepatitis e.g. rise in liver enzymes, the presence of HEV specific viral particles in the stool and histological changes in the liver from 21 to 45 days after HEV inoculation. All the animals recovered completely as reflected by normalization of liver enzymes, and regenerative changes in the liver. The present report highlights the ultrastructural changes in the livers of these experimental monkeys. The histopathological changes included infiltration of lymphocytes and polymorphonucleocytes around the necrotic area, swelling of mitochondria, dilation of smooth endoplasmic reticulum (ER), and presence of 27-34 nm virus particles during the acute phase of the disease. In comparison, 9 control monkeys did not show any such histological changes.

Association of hepatitis E virus with an outbreak of hepatitis in Pakistan: serologic responses and pattern of virus excretion

Hepatitis E virus (HEV), a positive-strand RNA agent, has been associated with enterically transmitted non-A, non-B hepatitis in Asia, Africa, and Mexico. To evaluate the role of HEV in an outbreak of hepatitis in Pakistan, we used immune electron microscopy to detect 1) antibody to HEV, for evidence of infection, and 2) virus, to determine the pattern of HEV excretion. Paired sera from 2 patients were assayed for antibody by using reference HEV: one seroconverted, an atypical finding for HEV infections; the other had high levels of anti-HEV in both sera. Virus particles with the size (29 x 31 nm) and morphology of HEV were detected in feces from 10 of 85 patients and serologically identified as HEV by using reference antibodies from an HEV-infected chimpanzee. One of these HEV-containing specimens was collected 9 days before the onset of jaundice; it was among feces from 38 outpatients with nonspecific symptoms and biochemical hepatitis, 12 of whom subsequently developed jaundice. The other 9 feces with HEV were among 36 collected within 7 days of the onset of acute icteric hepatitis; all 11 feces from days 8 to 15 were negative for HEV. Fecal concentrations of HEV appeared to be lower than those of many enteric viruses: only one specimen contained as many as 5 particles per EM grid square. It is concluded that HEV was etiologically associated with the epidemic and was predominantly excreted at very low levels during the first week of jaundice.

Gastroenterological emergencies in the tropics

Significant differences exist in the prevalence of most gastroenterological emergencies in tropical compared with temperate countries. Both ethnic and environmental (often clearly defined geographically) factors are relevant. The major oesophageal lesions which can present acutely in tropical countries are varices and carcinoma; bleeding and obstruction are important sequelae. Peptic ulcer disease (and its complications), often associated (not necessarily causally) with Helicobacter pylori infection, has marked geographical variations in incidence. Emergencies involving the small intestine are dominated by severe dehydration, and its sequelae, resulting from secretory diarrhoea, most notably cholera. However, enteritis necroticans ('pig bel' disease), paralytic ileus (sometimes caused by antiperistaltic agents) and obstruction (secondary to luminal helminths, volvulus and intussusception) are other important problems, especially in infants and children. Enteric fever is occasionally complicated by perforation and haemorrhage; the former (which is notoriously difficult to manage) is accompanied by significant mortality. Ileocaecal tuberculosis is a major cause of right iliac fossa pathology--sometimes associated with malabsorption; amoeboma is an important clinical differential diagnosis. The colon can be involved in invasive Entamoeba histolytica infection (which, like complicated enteric fever, is difficult to manage if the fulminant form, with perforation, ensues), shigellosis, volvulus and intussusception. Acute colonic dilatation occasionally follows Salmonella sp., Shigella sp., Campylobacter jejuni, Yersinia enterocolitica and rarely E. histolytica infections. Acute hepatocellular failure is a major cause of morbidity and mortality in the tropics and subtropics. It usually results from viral hepatitis (HBV, sometimes complicated by HDV, and HCV), but there is a long list of differential diagnoses. Hepatotoxicity resulting from herbs, chemotherapeutic agents or alcohol also occurs not infrequently. Chronic liver disease and its sequelae (often long-term results of viral hepatitis) are commonplace. Haematemesis and hepatocellular failure are usually very difficult to manage due to a lack of sophisticated support techniques in developing countries. Invasive hepatic amoebiasis usually responds well to medical management; however, spontaneous perforation can occur and the consequences of this are serious. Pyogenic liver abscess, although far less common than amoebic 'abscess', carries a bad prognosis whatever the method(s) of management. Hydatidosis and schistosomiasis also involve the liver, and helminthiases are important in the context of biliary tract disease. Gall stones are unusual in most tropical settings. Acute pancreatitis is overall unusual, but chronic calcific pancreatitis can present as an acute abdominal emergency.

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.

Transmission of enteric non-A, non-B hepatitis virus in Macaca mulatta monkeys by intraportal route: subsequent passages of HEV virus

Macaca mulatta monkeys have been used for the transmission of enteric non-A, non-B hepatitis (HEV) virus by intraportal route. Subsequent passages of HEV virus have been completed in these monkeys. In the first passage, 2 monkeys were inoculated by intra-portal route with 27-34 nm virus-like particles (VLP) obtained from known epidemics of HEV hepatitis in India, and biochemical and serological changes in the blood, histological changes in the liver and excretion of 27-34 nm VLP in the stool were studied. Results were compared with those of 4 negative control monkeys inoculated with stool extracts from healthy individuals. The second passage of 27-34 nm VLP was carried out on 2 monkeys using pools of stool suspension positive for 27-34 nm VLP from first passaged animals. Similarly, the third passage of 27-34 nm VLP was completed intraportally in another monkey. All monkeys developed acute hepatitis, as evidenced by transient elevation of aminotransferase, histopathological changes in the liver, development of antibodies aggregating 27-34 nm VLP and excretion of 27-34 nm VLP in stools. No control monkeys developed these features.

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.