Variability of hepatitis E serologic assays in a pediatric liver transplant recipient: challenges to diagnosing hepatitis E virus infection in the United States

Hepatitis E virus (HEV) is an emerging cause of viral hepatitis among immunocompromised individuals in developed countries. Yet the diagnosis of HEV infection in the United States remains challenging, because of the variable sensitivity and specificity of currently available tests, and the lack of a US Food and Drug Administration-approved test. We report a case of multiple discordant HEV serology results in a pediatric liver transplant recipient with idiopathic hepatitis, and review the challenges to diagnosis of HEV infection in the United States.

PCR method for detection of adenovirus in urine of healthy and human immunodeficiency virus-infected individuals

Adenoviruses (AdV) cause diseases that range from localized, self-limited illnesses to fatal infections in immunocompromised patients. Culture is assumed to be sensitive but requires viable virus and up to 3 weeks for detection, and it can be inhibited by bacterial contamination. A new PCR method amplifying a region of the hexon gene was developed in order to detect AdV in urine more rapidly and with greater sensitivity than obtainable by culture technology. All 18 serotypes tested were detected. Quantitatively, with optimized urine processing, AdV PCR detected 0.2 PFU/ml (serotype 11) and 10 DNA copies/ml (serotype 2). Serially collected urine samples from human immunodeficiency virus (HIV)-infected patients with concurrent cytomegalovirus retinitis were divided into three groups: AdV culture-positive samples, AdV culture-negative or bacterially contaminated samples from patients with a history of AdV culture-positive urines, and AdV culture-negative samples from patients without a history of AdV culture positivity. Urine samples from healthy adults were also tested by culture and PCR to screen for asymptomatic shedding. Amplification was assessed with and without prior DNA purification. AdV was detected by PCR in 90% of culture-positive urines (100% of unclotted samples, e.g., those culture positive after storage for PCR testing), 71% of culture-negative or bacterially contaminated urines from AdV-infected patients, and 28% from AdV culture-negative patients. Healthy volunteers were culture negative for AdV, and 96% were PCR negative. The new AdV PCR method is rapid and sensitive and can detect viral DNA in samples for which culturing is problematic. The role of AdV replication during HIV infection merits further investigation with sensitive tools such as PCR.

GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid) is a potent inhibitor of influenza virus in ferrets

GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid) is a novel viral neuraminidase (sialidase) inhibitor which, following intranasal administration in ferrets, is at least 100 to 1,000 times more effective than ribavirin and amantadine against influenza A and B viruses. It retains its activity even when treatments are delayed until 24 h postinfection and has no effect on the serum antibody response to infection.

Inhibition of influenza virus replication in mice by GG167 (4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid) is consistent with extracellular activity of viral neuraminidase (sialidase)

We demonstrate the potent antiviral activity of a novel viral neuraminidase (sialidase) inhibitor, 4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid (GG167), administered by the intranasal route in comparison with those of amantadine and ribavirin in experimental respiratory tract infections induced with influenza A and B viruses. In an extended study in which mice were infected (day 0) with influenza A/Singapore/1/57 virus, with treatments given prophylactically plus twice daily over days 0 to 3 and with mice observed to day 10, we show that intranasally administered GG167 at 0.4 and 0.01 mg/kg of body weight per dose reduced mortality, lung consolidation, and virus titers in the lung, with no virus growing back following the cessation of treatment. In other studies with influenza B/Victoria/102/85 virus in which infected mice were culled after the cessation of treatment, the calculated intranasal dose required to reduce virus titers in the lungs of treated animals to 10% of that seen in untreated controls (EDAUC10 [where AUC is area under the virus titer days curve]) was 0.085 mg/kg per dose. GG167 was inactive against influenza viruses A and B when given by the intraperitoneal or oral route (EDAUC10, > 100 mg/kg per dose). GG167 was metabolically stable, with an elimination half-life of 10 min following intravenous administration. While readily bioavailable by systemic routes, it was poorly bioavailable by the oral route. Its potent efficacy by the intranasal route but lack of efficacy by other routes, relative to those of amantadine and ribavirin, was explicable in terms of its in vitro activity, bioavailability, and pharmacokinetic properties and with the extracellular activity of viral sialidase.

Epidemic hepatitis E in Pakistan: patterns of serologic response and evidence that antibody to hepatitis E virus protects against disease

IgM and IgG anti-hepatitis E virus (HEV) patterns were determined in sera collected during a hepatitis outbreak in Pakistan. HEV infection was detected serologically in 122 patients. IgM anti-HEV was detected in specimens collected up to 2 weeks before and 5-7 weeks after hospitalization in 91% and 100%, respectively, of 122 HEV-infected patients. IgG followed a similar pattern. Peak antibody titers appeared 2-4 weeks after hospitalization. At 20 months after hospitalization, IgM anti-HEV was not detected in any of 33 patients; IgG was found in all. IgG anti-HEV appeared to be protective in contracts of patients. This study confirms HEV as the cause of the outbreak, quantifies IgM and IgG anti-HEV responses, provides evidence that IgG anti-HEV protects against hepatitis E, and demonstrates that IgG anti-HEV persists, but at diminished titer, after infection. Hepatitis E in young adults is the result of primary infection with HEV and, if reinfection occurs, it does not commonly cause serious illness.

Detection of hepatitis A virus in sewage sludge by antigen capture polymerase chain reaction

Antigen capture polymerase chain reaction (PCR) was tested as a sensitive and rapid method for detecting hepatitis A virus (HAV) in raw sewage sludge. The antigen capture PCR was performed both with and without solid-phase virus-catching monoclonal antibodies. Similar results proved that both methods were equally sensitive. Sewage sludge samples from different regions in Germany were examined for evidence of HAV contamination by antigen capture PCR. This method of detection was compared with that used in a previous study of these sewage sludge samples, in which the HAV was detected through indirect immunofluorescence after cell culture inoculation. The results obtained by antigen capture PCR matched those obtained in the earlier cell culture investigations, when HAV was detected in raw as well as digested sewage sludge samples. The advantage of the PCR method, however, lies in the fact that it needs only two days while the cell culture propagation of HAV takes about 8 to 10 weeks.

ELISA for antibody to hepatitis E virus (HEV) based on complete open-reading frame-2 protein expressed in insect cells: identification of HEV infection in primates

A recombinant baculovirus containing the complete open-reading frame (ORF)-2 region of the hepatitis E virus (HEV) genome was constructed. The major protein synthesized in insect cells infected with recombinant virus was about the size expected for the complete ORF-2 product. This protein reacted in a Western blot assay with plasma from an HEV-infected chimpanzee. Lysates of the recombinant virus-infected insect cells were used in ELISA to monitor seroconversion of eight primate species (chimpanzees, four species of Old World monkeys, and three species of New World monkeys) inoculated with HEV. Homologous detector anti-immunoglobulin was more sensitive than heterologous anti-immunoglobulin for detecting anti-HEV by ELISA. All primate species except tamarins seroconverted after inoculation with HEV, although anti-HEV titers of Old World monkey species were generally higher than those of New World monkey species. The ELISA with complete ORF-2 antigen appeared to be a sensitive and practical method for detecting anti-HEV.

4-Guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid is a highly effective inhibitor both of the sialidase (neuraminidase) and of growth of a wide range of influenza A and B viruses in vitro

The sialidase (neuraminidase) inhibitor 4-guanidino-2,4-dideoxy-2,3-dehydro-N-acetylneuraminic acid (4-guanidino-Neu5Ac2en) has been examined for the ability to inhibit the growth of a wide range of influenza A and B viruses in vitro in comparison with amantadine, rimantadine, and ribavirin. 4-Guanidino-Neu5Ac2en inhibited plaque formation by laboratory-passaged strains of influenza A and B viruses, with 50% inhibitory concentrations ranging from 0.005 to 0.014 microM. A wider range of values (0.02 to 16 microM) was obtained with more recent clinical isolates, but in all cases 4-guanidino-Neu5Ac2en inhibited influenza A and B virus replication at lower concentrations than amantadine, rimantadine, or ribavirin. Inhibition by 4-guanidino-Neu5Ac2en was not obviously affected by the passage history of the viruses or by resistance to amantadine or rimantadine. 4-Guanidino-Neu5Ac2en was a very potent inhibitor of the sialidases of all the influenza viruses examined, with 50% inhibitory concentrations ranging from 0.00064 to 0.0079 microM. No cytotoxicity was observed with 4-guanidino-Neu5Ac2en at up to 10 mM. 4-Guanidino-Neu5Ac2en therefore represents a new potent and selective inhibitor of influenza A and B virus sialidase activity and replication in vitro.

Infection of owl monkeys (Aotus trivirgatus) and cynomolgus monkeys (Macaca fascicularis) with hepatitis E virus from Mexico

Owl and cynomolgus monkeys were inoculated with hepatitis E virus (HEV) to compare disease models and produce antibody and virus. By immune electron microscopy (IEM), all six owl monkeys were shown to have serologic responses manifested by unusually high levels of anti-HEV at 6 months, but only three developed hepatitis. Virus-related antigen in liver (HEV Ag) was detected by immunofluorescence microscopy of biopsies from two of four owl monkeys; one with HEV Ag also had HEV in acute-phase bile (detected by IEM) and feces (detected by infecting another owl monkey). In contrast, cynomolgus monkeys propagated HEV to higher levels and all five had hepatitis. Moderate-to-high levels of HEV Ag correlated with detectable HEV in bile for both species. Thus, the value of using HEV-infected cynomolgus was confirmed. Owl monkeys were shown to be HEV-susceptible and sources of high-level anti-HEV; Sustained anti-HEV in these monkeys may also be useful for understanding immune responses.

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.

Clinical and laboratory observations following oral or intramuscular administration of a live attenuated hepatitis A vaccine candidate

Clinical observations made after immunising volunteers with a live attenuated hepatitis A vaccine are described. The candidate vaccine was prepared with the HM175 strain of hepatitis A virus and shown to be safe, immunogenic and efficacious in experimental animals. When the candidate vaccine was tested by oral administration in humans at increasing doses--10(4), 10(5), 10(6) and 10(7) median tissue culture infective doses (TCID50)--an antibody response was not observed at any dose. Volunteers who received similar doses by the intramuscular route developed antibody to hepatitis A three weeks after immunization with 10(6) or 10(7) TCID50. The antibody response was sustained for the 12 weeks of the observation period. All volunteers remained healthy with normal results from liver tests throughout the monitoring period. Further clinical observations of this product are in progress.

Simian hepatitis A virus (HAV) strain AGM-27: comparison of genome structure and growth in cell culture with other HAV strains

Fragments of cDNA representing greater than 99% of the entire genome of wild-type hepatitis A virus (HAV) strain AGM-27, isolated from an African green monkey, were obtained by the polymerase chain reaction and sequenced. Comparison with other HAV isolates revealed differences in the predicted amino acid sequence in functionally critical parts of the genome. Comparison of the biological properties of AGM-27 with those of human wild-type and cell culture-adapted HM-175 strains revealed that AGM-27 grew in cell culture significantly better than did wild-type HM-175, but not as well as cell culture-adapted HM-175. AGM-27 and cell culture-adapted HM-175 were distinguishable by their differential growth in CV-1, FRhK-4 and primary AGMK cells.

Large-scale purification of inactivated hepatitis A virus by centrifugation in non-ionic gradients

Formalin-inactivated hepatitis A virus (HAV) can be purified for vaccine preparation by centrifugation in Renografin-76 (diatrizoate meglumine and diatrizoate sodium) gradients. Both continuous-flow rate-zonal and isopycnic methods were used for the separation of a major antigen component from minor antigen and host protein. The major antigen component, which appeared to contain complete virions by electron microscopy, could be recovered from gradients and accounted for approximately one third of the total antigen in the starting material. The HAV-specific purified antigen could be enriched 200-300-fold by either centrifugation procedure. The purified HAV antigen, when adsorbed to alum and inoculated into mice, was found to be highly immunogenic.

Detection of hepatitis A virus and other enteroviruses in water by ssRNA probes

Sensitive and specific methods are needed to detect hepatitis A virus (HAV) and other human enteroviruses in environmental samples such as drinking water and foods. Clones of cDNA encoding the 5'-most 1 kb of the HAV and coxsackievirus B3 (CB3) genomes were subcloned into T7/SP6 RNA transcription vectors. In vitro transcribed RNA from the T7 promoter detected their respective HAV or CB3 genomic RNA. Conversely, SP6 transcripts detected viral negative-stranded RNA but not the genome. When both ssRNA probes were tested at high temperature (65 degrees C), they did not hybridize with intracellular RNAs from 6 primate cell cultures used for isolation of HAV and other enteroviruses. The HAV probe did not hybridize with 13 different enteroviruses but detected as little as 500-1000 infectious units of the 7 strains of HAV tested. Conversely, the CB3 probe showed strong homology with all 13 enteroviruses tested but not HAV. The probes were used to detect HAV and other enteroviruses in water samples after virus amplification in cell culture. HAV was detected in water samples obtained during a waterborne hepatitis outbreak using the ssRNA probe. These samples were negative for HAV by direct solid phase radioimmunoassay and were not positive by immunoassays of inoculated cell cultures until several weeks of propagation. The CB3 ssRNA probe detected enteroviruses in samples of surface water and drinking water that were negative for cytopathic effects in inoculated cell cultures.

Virus-like particles in the liver of a patient with fulminant hepatitis and antibody to hepatitis E virus

In earlier studies, hepatitis E virus (HEV) particles were detected in the stools of patients with enterically transmitted non-A, non-B (ENANB) hepatitis, and HEV was etiologically associated with this disease. Such particles have not been observed in the liver, however. We describe the pathological findings in the liver of a young pregnant woman from Nepal who died as a result of fulminant NANB hepatitis. IgM antibody to HEV was detected in the patient's serum by immune electron microscopy, suggesting that she was acutely infected with that virus. On light microscopic examination of the liver we observed cholestatic hepatitis with proliferation of bile ductules and pseudoglandular arrangement of hepatocytes around distended bile canaliculi. Three types of virus-like particles were detected by electron microscopy. The most frequently observed particles were in cells lining small bile ductules; they measured 32-37 nm and were enclosed by a membrane. Particles of a second type were seen in clusters in the sinusoidal cells; they were uniform in size, without a membrane, and measured about 32 nm in diameter. Particles of a third type (65 nm) were found in epithelial cells of the small bile ductules. Among the particles we detected, the 32 nm particles most closely resembled those of HEV.

Attenuation and cell culture adaptation of hepatitis A virus (HAV): a genetic analysis with HAV cDNA

RNA transcripts of hepatitis A virus (HAV) HM-175 cDNA from attenuated, cell culture-adapted HAV were infectious in cell culture. A full-length HAV cDNA from wild-type HAV (propagated in marmosets in vivo) was constructed. Chimeric cDNAs that contained portions of both wild-type and attenuated genomes were produced. Oligonucleotide-directed mutagenesis was used to engineer a point mutation into the VP1 gene of attenuated HAV cDNA, so that the sequence of this capsid protein would be identical to that of the wild-type virus. Transfection of monkey kidney cells with RNA transcripts from several of the chimeric cDNAs and from the mutagenized cDNA induced production of HAV. Comparison of the growth of attenuated, wild-type, chimeric, and mutant viruses in vitro indicated that the P2-P3 (nonstructural protein) region is important for cell culture adaptation of the virus; the 5' noncoding region may also contribute to adaptation, but to a lesser extent. Inoculation of marmosets with transfection-derived virus also suggested that the P2-P3 region plays an important role in attenuation of HAV HM-175.

Aetiological association of a virus-like particle with enterically transmitted non-A, non-B hepatitis

Virus-like particles, approximately 27 nm in diameter, were identified in faeces from an Indian patient with enterically transmitted non-A, non-B (ENANB) hepatitis. They were serologically distinct from hepatitis A virus (HAV). Nucleic acid extracted from the particles did not hybridize with cDNA probes representing the genomes of HAV, enteroviruses, and cardioviruses. Chimpanzees were experimentally inoculated with faecal suspensions containing this 27 nm particle or with faeces from another case of ENANB hepatitis. Mild histological and biochemical hepatitis developed in these animals and there was serological evidence of infection with the virus-like particle as shown by immunoelectronmicroscopy (IEM). Serological analysis by IEM suggested that this agent or an antigenically similar virus was the aetiological agent of two epidemics and a sporadic case of ENANB hepatitis in India and of an epidemic of the illness in the USSR. Antibody to the particle was found in sera from patients with ENANB hepatitis from various geographic areas over a 30-year period.

Studies of prototype live hepatitis A virus vaccines in primate models

We have prepared two prototype live hepatitis A virus (HAV) vaccines by serial passage of the HM-175 strain of HAV in African green monkey kidney cells. Passage 21 (P-21) HM-175 virus shows evidence of attenuation for chimpanzees but not for marmosets; passage 32 (P-32) HM-175 virus shows evidence of attenuation for both species. Animals that received P-32 HAV had fewer elevations in levels of liver enzyme activity and evidence of less virus replication in the liver and excretion of virus in stool than did those that received wild-type virus. The P-21 and P-32 viruses were highly immunogenic in both species. The information provided by this study will aid in the development of a live HAV vaccine.

The isolation of a virus resembling a polyomavirus from normal calves

Viruses with characteristics of polyomaviruses were isolated from the kidneys of 18 out of 64 clinically normal calves 1-2 weeks old. All the viruses were serologically related.

An epidemic of hepatitis A in an institution for young children

A common-source epidemic of hepatitis A occurred in an Athenian institution boarding 38 children (mean age 4.8 years). All children were examined, and blood was drawn from each at the onset of the study and repeatedly during the next three months. Only one child (2.6%) was initially immune to hepatitis A virus as a result of prior infection. The attack rate (62.2%) and the ratio of icteric to anicteric cases (1:1.3) were high despite the administration of immunoglobulin (IG). Assays for anti-HAV IgM and a rising titer of anti-HAV IgG identified 19 (82.6%) and 22 (95.7%) of the 23 hepatitis A infections, respectively. One case (4.3%) was detected only by the presence of hepatitis A virus antigen and hepatitis A virus RNA in a fecal specimen, but these assays were otherwise marginally useful in this study. Nevertheless, the use of all available tests for the detection of hepatitis A virus is mandatory for the most accurate estimation of an epidemic of hepatitis A. Prompt administration of immunoglobulin had no effect on the number of clinical cases that were in the late incubation period, but it may have diminished the clinical expression of the infection and thus made diagnosis of infection more difficult.