T-cell vaccines that elicit effective immune responses against HCV in chimpanzees may create greater immune pressure for viral mutation

A prime/boost vaccine strategy that transfects antigen-presenting cells using ligand-modified immunoliposomes to efficiently deliver plasmid DNA, followed by boosting with non-replicating recombinant adenovirus was used in chimpanzees to generate HCV-specific memory T-cells. Three chimpanzees (two vaccines, one control) were immunized with immunoliposomes complexed with DNA expressing NS3-NS5B or complexed with empty vector. Animals were boosted with adenovirus expressing NS3-NS5B, or non-recombinant adenovirus (control). Using liposome delivery we were able to obtain specific HCV responses following DNA priming in the chimpanzees. This data and mouse immunization studies confirm this as a more efficient delivery system than direct intramuscular inoculations with naked DNA. Subsequent to the adenovirus boost significant increases in peripheral HCV-specific T-cell responses and intrahepatic IFN-gamma and CD3varepsilon mRNA were also observed in the two vaccinated animals. Following challenge (100 CID(50)) both vaccinated animals showed immediate and significant control of viral replication (peak titers 3.7x10(4) and 9x10(3)IU/mL at weeks 1 and 2), which coincided with increases in HCV-specific T-cell responses. Viral kinetics in the control animal were comparable to historical controls with exponential increases in titer during the first several weeks. One vaccinated animal developed a low-level persistent infection (2x10(3)IU/mL) which correlated with a decrease in HCV-specific T-cell responses. Circulating virus isolated from both vaccinated animals showed approximately 2-fold greater nonsynonymous mutation rates compared to controls and the nonsynonymous/synonymous mutation rate ratio was indicative of positive selection. These data suggest that although T-cell vaccines can induce immune responses capable of controlling HCV, they also induce high levels of immune pressure for the potential selection of escape mutants.

Quantitative detection of hepatitis E virus RNA and dynamics of viral replication in experimental infection

Hepatitis E virus (HEV) RNA has been detected in the stool and serum of patients with HEV infection and experimentally infected nonhuman primates. However, dynamics of HEV levels in the stool and serum during clinical and subclinical infections have not been determined. A real-time reverse transcription polymerase chain reaction assay, using SYBR Green I in a LightCycler, was developed and optimized to allow quantification of HEV RNA in the stool and serum of both genotype 1 and 2 isolates. The specificity of the assay was confirmed by testing known HEV-RNA-positive and -negative stool and serum specimens and the sensitivity was evaluated using a synthetic HEV RNA standard. Profiles of viraemia and faecal shedding in two chimpanzees inoculated with an isolate of HEV genotype 1 showed the appearance of virus in the stools on day 4 postinoculation (5.65-6.85 log copies/mg) and in the serum on day 7 postinoculation (6.0-6.93 log copies/mL). Peak HEV RNA levels in the stool and serum coincided with peak alanine aminotransferase (ALT) levels observed on day 22 postinoculation in the two chimpanzees. At the time of detection of IgG anti-HEV in serum, viral RNA was no longer detectable in the stool or serum and ALT values had returned to normal levels in both chimpanzees, suggesting the efficacy of the immune response in terminating viral replication. Quantitative evaluation of HEV RNA in humans may allow determining the role of virus levels in the pathogenesis and transmission of HEV.

Experimental studies on subclinical hepatitis E virus infection in cynomolgus macaques

Serial subclinical transmission among susceptible humans may serve as a reservoir of hepatitis E virus (HEV) in areas in which HEV is endemic. This hypothesis was investigated in an experimental primate model. Four groups of 4 cynomolgus macaques each were inoculated intravenously with 10(4)-10(5) (group 1), 10-100 (group 2), and 1-10 (group 3) cynomolgus macaque HEV infectious doses. All 4 animals in group 1 had clinical disease marked by alanine aminotransferase (ALT) elevation, fecal virus excretion, viremia, and seroconversion. Of the animals in groups 2 and 3, only 1 had evidence of biochemical hepatitis, although most had virus excretion and viremia (3 animals each in groups 2 and 3), and evidence of seroconversion (1 animal in group 2 and 3 animals in group 3). Viral genomic titers in stool specimens of animals with or without ALT elevation were similar. Infectivity studies confirmed the viability and transmission potential of the virus excreted by animals without ALT elevation. These data suggest that subclinical HEV infection may represent an HEV reservoir.

Nonenveloped nucleocapsids of hepatitis C virus in the serum of infected patients

One of the characteristics of hepatitis C virus (HCV) is the high incidence of persistent infection. HCV core protein, in addition to forming the viral nucleocapsid, has multiple regulatory functions in host-cell transcription, apoptosis, cell transformation, and lipid metabolism and may play a role in suppressing host immune response. This protein is thought to be present in the bloodstream of the infected host as the nucleocapsid of infectious, enveloped virions. This study provides evidence that viral particles with the physicochemical, morphological, and antigenic properties of nonenveloped HCV nucleocapsids are present in the plasma of HCV-infected individuals. These particles have a buoyant density of 1.32 to 1.34 g/ml in CsCl, are heterogeneous in size (with predominance of particles 38 to 43 or 54 to 62 nm in diameter on electron microscopy), and express on their surface epitopes located in amino acids 24 to 68 of the core protein. Similar nucleocapsid-like particles are also produced in insect cells infected with recombinant baculovirus bearing cDNA for structural HCV proteins. HCV core particles isolated from plasma were used to generate anti-core monoclonal antibodies (MAbs). These MAbs stained HCV core in the cytoplasm of hepatocytes from experimentally infected chimpanzees in the acute phase of the infection. These chimpanzees had concomitantly HCV core antigen in serum. These findings suggest that overproduction of nonenveloped nucleocapsids and their release into the bloodstream are properties of HCV morphogenesis. The presence of circulating cores in serum and accumulation of the core protein in liver cells during the early phase of infection may contribute to the persistence of HCV and its many immunopathological effects in the infected host.

Global epidemiology and medical aspects of hepatitis E

Hepatitis E is a self-limited enterically transmitted acute viral hepatitis that occurs frequently in epidemic outbreaks and as sporadic hepatitis in the Indian sub-continent, Southeast and Central Asia, the Middle East, parts of Africa, and Mexico. Hepatitis E virus (HEV) is excreted in faeces and is transmitted predominantly by the faecal-oral route, usually through contaminated water. The reservoir of the virus during the inter-epidemic periods in disease-endemic countries may reside in the environment, in sub-clinically HEV-infected humans, and/or animals infected with an HEV-like virus. Chronic infection is unknown. Diagnosis of HEV infection is usually made by detection of anti-HEV antibodies or HEV-RNA in patients serum specimens. Clinical illness due to HEV infection is similar to other forms of viral hepatitis except in pregnant women, in whom the illness is particularly severe with a mortality as high as 25%. Asymptomatic and anicteric infections may occur. No specific treatment is available, and the most effective mode of preventing this disease is use of clean water and proper sanitation. Recombinant vaccines are being developed that may be particularly useful for travellers to the disease-endemic areas and for pregnant women.

Hepatitis E virus infection in chimpanzees: a retrospective analysis

Different patterns of disease were observed among 11 chimpanzees who were inoculated intravenously with hepatitis E virus (HEV) positive fecal specimens from four different outbreaks (Nepal 1981, Uzbekistan 1981, Pakistan 1985, and Mexico 1986). Five chimpanzees had marginal or no liver enzyme elevations within 70 days of inoculation. Two of the chimpanzees had limited viremia, but did not produce detectable antibody. The four remaining chimpanzees had liver enzyme elevations, viral shedding, viremia, seroconversion to anti-HEV, and detectable HEV antigen in liver biopsy specimens. These results may reflect the range of infection patterns that develop in humans after natural exposure to the HEV.

Duration of viraemia and faecal viral excretion in acute hepatitis E

Data on duration of viral excretion and viraemia during hepatitis E virus (HEV) infection are limited. We tested serial stool and serum samples from 20 patients with acute hepatitis E for HEV RNA. Faecal excretion and viraemia in these patients were found to be short lived. In 19 patients, all samples obtained after biochemical resolution of hepatitis tested negative; in the remaining patient, HEV RNA was detected in the serum samples but not in stool after biochemical resolution. Long-term persistence of HEV in body fluids of infected individuals seems to be an unlikely reservoir for transmission of HEV.

Related TT viruses in chimpanzees

A series of serum specimens obtained from two chimpanzees experimentally infected with hepatitis A virus (HAV), hepatitis C virus, and hepatitis G/GB-C virus were tested for TT virus (TTV) by polymerase chain reaction (PCR). All PCR fragments obtained from both animals were directly sequenced, and the nucleotide sequences were compared to each other and to all known TTV sequences. This comparison showed that both animals were infected simultaneously with four new TTV variants designated A, M1, M2, and M3. One chimpanzee was found to be infected with TTV only after HAV inoculation, whereas the other animal was infected with TTV before any experimental procedure was performed. A set of PCR primers specific for these four new TTV variants was used to amplify TTV-like sequences from nine naive chimpanzees. None of these animals was infected with the prototype TTV variant. Two of these animals, however, were infected with one of the new TTV variants, while one animal was infected with an additional new TTV variant designated T. Among 99 hepatitis patients, 29 were found to be infected with the prototype TTV variant. None of these human specimens was found to be positive by PCR specific for TTV variants A, M1, M2, and M3. Similarly, not a single specimen from a smaller subset of human serum samples was found to be positive for the TTV variant T. Phylogenetic analysis performed on all known TTV sequences demonstrated that TTV can be classified into 13 different, yet closely related TTV species, designated as TTV-I for the prototype variant through TTV-XIII. The new variants M1 and M2 were classified as two different genotypes of TTV-VI, variant M3 was classified as TTV-VII, variant A was classified as TTV-VIII, and variant T was classified as TTV-IX. Thus, the data obtained in this study suggest that TTV represents a large swarm of TTV-like species, some of which have not been detected in humans and circulate predominantly among chimpanzees.

Hepatitis E

Hepatitis E, previously known as enterically transmitted non-A, non-B hepatitis, is an infectious viral disease with clinical and morphologic features of acute hepatitis. Its causative agent, hepatitis E virus, consists of small, 32- to 34-nm diameter, icosahedral, nonenveloped particles with a single-stranded, positive-sense, 7.5-kb RNA. The virus has two main geographically distinct strains, Asian and Mexican; recently, novel isolates from nonendemic areas and a genetically related swine HEV have been described. HEV is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in the Indian subcontinent, southeast and central Asia, the Middle East, parts of Africa, and Mexico. The virus is excreted in feces and is transmitted predominantly by fecal-oral route, usually through contaminated water. Person-to-person transmission is uncommon. Clinical attack rates are the highest among young adults. Recent evidence suggests that humans with subclinical HEV infection and animals may represent reservoirs of HEV; however, further data are needed. Diagnosis of hepatitis E is usually made by detection of specific IgM antibody, which disappears rapidly over a few months; IgG anti-HEV persists for at least a few years. Clinical illness is similar to other forms of acute viral hepatitis except in pregnant women, in whom illness is particularly severe with a high mortality rate. Subclinical and unapparent infections may occur; however, chronic infection is unknown. No specific treatment is yet available. Use of clean drinking water and proper sanitation is currently the most effective method of prevention. Passive immunization has not been proved to be effective, and recombinant vaccines for travelers to disease-endemic areas and for pregnant women currently are being developed.

Hepatitis E: an overview and recent advances in clinical and laboratory research

Hepatitis E virus (HEV) is a non-enveloped RNA (7.5 kb) virus that is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in southeast and central Asia, the Middle East, parts of Africa and Mexico. Hepatitis E virus infection spreads by the faecal-oral route (usually through contaminated water) and presents after an incubation period of 8-10 weeks with a clinical illness resembling other forms of acute viral hepatitis. Clinical attack rates are the highest among young adults. Asymptomatic and anicteric infections are known to occur. Chronic HEV infection is not observed. Although the mortality rate is usually low (0.07-0.6%), the illness may be particularly severe among pregnant women, with mortality rates reaching as high as 25%. Recent isolation of a swine virus resembling human HEV has opened the possibility of zoonotic HEV infection. Studies of pathogenetic events in humans and experimental animals reveal that viral excretion begins approximately 1 week prior to the onset of illness and persists for nearly 2 weks; viraemia can be detected during the late phase of the incubation period. Immunoglobulin M antibody to HEV (anti-HEV) appears early during clinical illness but disappears rapidly over a few months. Immunoglobulin G anti-HEV appears a few days later and persists for at least a few years. There is no specific treatment available for hepatitis E virus infection. Ensuring a clean drinking water supply remains the best preventive strategy. Recombinant vaccines are being developed that may be particularly useful for travellers to disease-endemic areas and for pregnant women.

Excretion of hepatitis A virus (HAV) in adults: comparison of immunologic and molecular detection methods and relationship between HAV positivity and infectivity in tamarins

Fecal excretion of hepatitis A virus (HAV) in 18 patients with HAV infection was evaluated by enzyme immunoassay (EIA) to detect viral antigen and by reverse transcription-PCR amplification followed by ethidium bromide staining (PCR-ETBr) or nucleic acid hybridization (PCR-NA) to detect viral genetic material. A gradation of sensitivity was observed in the detection of virus by the three methods. In persons who had detectable virus, serial stool samples were found to be positive by EIA for up to 24 days after the peak elevation of liver enzymes. Viral genetic material could be detected by PCR-ETBr for up to 34 days and by PCR-NA for up to 54 days after the peak elevation of liver enzymes. After intravenous inoculation of tamarins with stool suspensions categorized as highly reactive for HAV (positive by EIA, PCR-ETBr, and PCR-NA), moderately reactive (positive by PCR-ETBr and PCR-NA), or weakly reactive (positive by PCR-NA), only tamarins infected with highly reactive stool suspensions (EIA positive) developed HAV infection. We conclude that positivity of stool specimens for HAV by PCR-ETBr or PCR-NA indicates a lower potential for infectivity, compared to that of EIA-positive stools.

Antigenic epitopes of the hepatitis A virus polyprotein

Forty-two antigenic domains were identified across the hepatitis A virus (HAV) polyprotein by using a set of 237 overlapping 20-mer synthetic peptides spanning the entire HAV polyprotein and a panel of serum samples from acutely HAV-infected patients. The term "antigenic domain" is used in this study to define a protein region spanned with consecutive overlapping immunoreactive peptides. Nineteen antigenic domains were found within the structural proteins, and 22 were found within the nonstructural proteins, with 1 domain spanning the junction of VP1 and P2A proteins. Five of these domains were considered immunodominant, as judged by both the breadth and the strength of their immunoreactivity. One domain is located within the VP2 protein at position 57-90 aa. A second domain, located at position 767-842 aa, contains the C-terminal part of the VP1 protein and the entire P2A protein. A third domain, located at position 1403-1456 aa, comprises the C-terminal part of the P2C protein and the N-terminal half of the P3A protein. The fourth domain, located at position 1500-1519 aa, includes almost the entire P3B, and the last domain, located at position 1719-1764 aa, contains the C-terminal region of the P3C protein and the N-terminal region of the P3D protein. It is interesting to note that four of the five most immunoreactive domains are derived from small HAV proteins and/or encompass protein cleavage sites separating different HAV proteins. The HAV-specific immunoreactivity of each antigenically reactive peptide was confirmed by using seven HAV seroconversion panels. Collectively, these data demonstrate that HAV structural and nonstructural proteins contain antigenic epitopes that can be efficiently modeled with short synthetic peptides.

Hepatitis E: an overview

Hepatitis E is an enterically transmitted, acute, self-limited, icteric viral disease that occurs in large numbers in countries of the Indian subcontinent, Asia, and Africa. The frequency of epidemics and the high mortality rate among infected pregnant women are strong indicators that hepatitis E is an important cause of morbidity and mortality in humans. Several isolates of hepatitis E virus (HEV) derived from infected humans and experimental animals have recently been cloned and sequenced, allowing investigators to determine the molecular structure of the HEV genome. Laboratory diagnosis of HEV infection is done by detection of HEV antibodies, HEV RNA in stool and serum samples, HEV particles in stool specimens, and HEV antigen in hepatocytes and stool specimens. The detection of anti-HEV by enzyme immunoassay, with the use of several recombinant HEV proteins or synthetic peptides, is the most frequently applied method for the diagnosis of the infection and characterization of its epidemiologic features. Laboratory determination of HEV replication, immune response, and liver pathologic features in patients with hepatitis E and in infected primates has facilitated studies of the disease. Preventive measures against HEV infection include the passive transfer of protective antibodies or active immunization. In efforts to develop HEV vaccines, various recombinant proteins have been used. Although a range of protective immune responses have been induced in primates, further modifications of immunogen, adjuvant, and immunization schedules are necessary to prevent HEV infection. Much remains to be learned about epidemiology of HEV infection, reservoir(s) of the virus, and protective immunity in order to develop effective strategies to prevent hepatitis E.

Detection of genomic- and minus-strand of hepatitis C virus RNA in the liver of chronic hepatitis C patients by strand-specific semiquantitative reverse-transcriptase polymerase chain reaction

Studies aimed at correlating the intrahepatic hepatitis C virus (HCV)-RNA level and anatomo-clinical features have been difficult because of sensitivity and specificity shortcomings of available techniques. We titered the genomic- and minus-strand HCV RNAs by a strand-specific, semiquantitative, genotype-independent reverse-transcriptase polymerase chain reaction (RT-PCR) in the liver tissue of 61 patients with chronic hepatitis C. Findings were correlated with the levels of HCV RNA in the serum, the HCV genotype, the expression of intrahepatic HCV antigens, the histological activity (using separate scores for the lobular and the portal/periportal necroinflammatory activity and for the fibrosis), and the response to interferon alfa (IFN-alpha) treatment. Genomic- and minus-strand HCV RNA were detected in 59 and 57 liver specimens, respectively. The HCV-RNA level in the serum correlated with the genomic-strand, but not with the minus-strand, HCV-RNA titer in the liver. No correlations were found between either strand of the intrahepatic HCV RNA and the level of expression of HCV antigens in the liver, or with the grading/staging of the underlying liver disease. The response to IFN-alpha treatment could be predicted by the serum HCV-RNA level and genotype, but not by the intrahepatic level of genomic- or minus-strand HCV RNA. These results suggest that, although the detection of the minus-strand HCV RNA reliably identifies the presence of replicating HCV in its target organ, the quantitative measurement of viremia remains the clinically meaningful "golden standard" for assessing the level of HCV replication.

In situ detection of hepatitis C viral antigens

A reliable detection system for HCV antigens in liver tissue may be used to identify the HCV cellular tropism and subcellular sites of viral replication Also, it can be used to study the relationship between viral expression and disease activity. Finally, it can facilitate the study of host-viral interactions at the cellular level (1).

Detection of intrahepatic hepatitis C virus replication by strand-specific semi-quantitative RT-PCR: preliminary application to the liver transplantation model

BACKGROUND/AIMS

Although the hepatitis C virus infection recurs in virtually all patients after liver transplantation, up to 50% of patients may not have histological recurrent hepatitis 1 year after liver transplantation. To study the relationship between hepatitis C virus infection and liver disease after liver transplantation, we compared the intrahepatic hepatitis C virus replication levels with the liver histopathology among liver transplant recipients.

METHODS

The intrahepatic negative-strand HCV RNA (i.e. the putative hepatitis C virus replication intermediate RNA) was evaluated by a semi-quantitative, strand-specific reverse transcriptase-polymerase chain reaction in 44 liver specimens from 23 patients with hepatitis C virus reinfection after liver transplantation. Results were compared with the time from liver transplantation, presence, grading and staging of the recurrent hepatitis, amount of hepatitis C virus antigens in the liver and serum HCV RNA levels.

RESULTS

Negative-strand HCV RNA was detected in 42 liver specimens as early as 7 days after liver transplantation. Its titers correlated with the amount of intrahepatic hepatitis C virus antigens, but not with HCV RNA levels in serum. Levels of negative-strand HCV RNA in 19 specimens without hepatitis were comparable to those seen in 25 specimens with hepatitis (p=0.492), and were unrelated to the liver disease grading and staging scores. The intrahepatic hepatitis C virus replication could occasionally precede the recurrence of the hepatitis by several months.

CONCLUSIONS

Molecular evidence has been obtained for intrahepatic hepatitis C virus replication occurring early after liver transplantation. The level of replication is not correlated with the development of recurrent hepatitis, suggesting that hepatitis C virus may replicate without inducing morphological evidence of liver damage.

Recurrent hepatitis C virus infection after liver transplantation: immunohistochemical assessment of the viral antigen

BACKGROUND

The value of immunohistochemical methods to identify hepatitis C virus antigen (HCVAg) in liver tissue has not been established. We have evaluated the significance of HCVAg expression in livers of patients with transplants and recurrent hepatitis C virus (HCV) infection.

METHODS

Forty-two liver biopsy specimens from 32 liver-transplant recipients with recurrent HCV infection were tested for HCVAg using fluorescein isothiocyanate-labeled polyclonal, polyreactive human immunoglobulin. Histologic assessment of liver and quantitation of HCV RNA in sera were carried out in specimens obtained simultaneously with biopsies.

RESULTS

HCVAg was found in 33% of the liver specimens obtained during the first month after transplantation and in all liver specimens obtained between 1 and 18 months after transplantation. Amounts of the antigen were significantly greater in specimens obtained more than 1 month after transplantation. A statistically significant increase of the average HCV RNA level in serum was observed in samples tested after the first month after the transplantation, and some decrease in the HCV RNA level was found in those obtained between 6 and 18 months after transplantation. Larger amounts of HCVAg were observed in specimens corresponding to episodes of acute or chronic hepatitis than in those associated with minimal parenchymal evidence of rejection.

CONCLUSIONS

OBSERVATIONS of HCVAg expression in liver biopsy specimens indicated that the presence of viral antigens in hepatocytes is a constant finding in specimens obtained 1 month or longer after transplantation. Although large amounts of HCVAg correlated with acute or chronic hepatitis, the nature of this association with the development of pathologic changes remains to be established.

Acute hepatitis E by a new isolate acquired in the United States

OBJECTIVE

To report the first case of acute hepatitis E by a novel isolate acquired in the United States and confirmed by nucleotide sequencing.

MATERIAL AND METHODS

We describe the clinical manifestations and the results of associated laboratory studies in a man who was found to have acute hepatitis E infection.

RESULTS

A 62-year-old man was hospitalized because of fever, abdominal pain, and jaundice. After an initial evaluation did not provide a cause, his serum was found to be positive for IgG anti-hepatitis E virus (HEV) by three antibody assays. Serum was also positive for HEV RNA by reverse transcriptase polymerase chain reaction (PCR). Sequencing results from the PCR products demonstrated substantial differences at the nucleotide level between this strain and the known Mexican and Burmese strains.

CONCLUSION

On the basis of this initial report, HEV should be considered an etiologic agent in patients with acute non-ABC hepatitis in the United States.

Novel hepatitis agents: the significance of clinical and experimental studies. An overview

A new virus with genomic organization similar to that of the family Flaviviridae was identified in patients with viral hepatitis and designated hepatitis G virus (HGV) or hepatitis GB virus C (GBV-C). HGV/GBV-C can be transmitted by blood and results in persistent infection, as shown in patients with posttransfusion non-A, non-B hepatitis, in transfusion recipients, and in donors of blood received by HGV-positive patients. The parenteral route of transmission of HGV/GBV-C infection was confirmed in experimentally infected chimpanzees. Epidemiologic studies of sporadic, community-acquired viral hepatitis have not indicated an association between HGV/GBV-C and acute non A-E hepatitis. Thus, the disease association of this new virus remains unconfirmed and its role in the etiology of acute and chronic hepatitis is unclear. The experimental model of HGV/GBV-C infection may define the biology of the virus replication.

Acute non-A-E hepatitis in the United States and the role of hepatitis G virus infection. Sentinel Counties Viral Hepatitis Study Team

BACKGROUND

Little is known about the relation of the newly discovered hepatitis G virus (HGV) to the cause and clinical course of acute and chronic viral hepatitis.

METHODS

We selected patients from a surveillance study of acute viral hepatitis in four U.S. counties who had acute disease during 1985 to 1986 or 1991 to 1995. Serum samples were tested for HGV RNA by the polymerase chain reaction.

RESULTS

HGV RNA was detected in 4 of 45 patients with a diagnosis of non-A-E hepatitis (9 percent), 23 of 116 patients with hepatitis C (20 percent), 25 of 100 patients with hepatitis A (25 percent), and 32 of 100 patients with hepatitis B (32 percent) (P<0.05 for the comparison of hepatitis B with hepatitis non-A-E or C). The clinical characteristics of the acute illness were similar for patients with HGV alone and those with hepatitis A, B, or C with or without HGV infection. During a follow-up period of one to nine years, chronic hepatitis did not develop in any of the patients with HGV alone, but 75 percent were persistently positive for HGV RNA, as were 87 percent of those with both hepatitis C and HGV infection. The rates of chronic hepatitis were similar in patients with hepatitis C alone (60 percent) and those with both hepatitis C and HGV infection (61 percent).

CONCLUSIONS

The evidence from this surveillance study does not implicate HGV as an etiologic agent of non-A-E hepatitis. Persistent infection with HGV was common, but it did not lead to chronic disease and did not affect the clinical course in patients with hepatitis A, B, or C.

Hepatitis E

Hepatitis E has a world-wide distribution and causes substantial morbidity and mortality in some developing countries, particularly among pregnant women. Hepatitis E virus (HEV) has recently been cloned and sequenced, and new diagnostic tests have been developed. These tests have been used to begin to characterize the natural history and epidemiological features of HEV infection. Experimental vaccines have also been developed that offer the potential to prevent hepatitis E. However, much remains to be learned about HEV, including the mechanisms of transmission, the reservoir(s) of the virus, and the natural history of protective immunity in order to develop effective strategies to prevent this disease.

Effect of immune globulin on the prevention of experimental hepatitis C virus infection

The efficacy of postexposure prophylaxis for the prevention of hepatitis C virus (HCV) infection was studied in experimentally infected chimpanzees. Three chimpanzees were inoculated with HCV: Two were treated 1 h later with anti-HCV--negative intravenous immune globulin (IGIV) or hepatitis C immune globulin (HCIG), and a third animal was not treated. HCV infection was detected in all 3 animals within a few days of inoculation. Once passively transferred anti-HCV declined in the HCIG-treated animal, there was an increase of HCV antigen (Ag)--positive hepatocytes followed by reappearance of anti-HCV; HCV Ag disappeared concordant with the development of acute hepatitis. Acute hepatitis C developed in both the IGIV-treated and untreated chimpanzees, with peak liver enzyme activity on day 59, but was delayed in the HCIG-treated animal until day 146. Postexposure HCIG treatment markedly prolonged the incubation period of acute hepatitis C but did not prevent or delay HCV infection. IGIV had no effect on the course of HCV infection.

Characterization of three novel monoclonal antibodies against hepatitis C virus core protein

Three novel monoclonal antibodies (MAbs) were established against a recombinant hepatitis C virus (HCV) core protein derived from cloned genotype 1b HCV cDNA. MAbs C7-50 and C8-59 recognize a conserved linear epitope represented by amino acid residues 21 to 40 of the nucleocapsid protein. MAb C8-48 is directed against a strain-specific conformational epitope located within the first 82 amino acids. A sensitive two-site MAb-based immunoradiometric assay was established using antibodies directed against distinct epitopes on the nucleocapsid protein. Processed 21 kDa core protein was detected by immunoblotting in human hepatocellular carcinoma cell lines and primary adult rat hepatocytes transfected with a cytomegalovirus promoter-driven expression construct. Immunofluorescence microscopy studies revealed a granular and vesicular cytoplasmic staining pattern. MAb C7-50 was used successfully to detect HCV core antigen in chronically infected chimpanzee liver tissue. These MAbs represent important reagents for the study of HCV biology and for the development of immunodiagnostic assays.

Hepatitis E: an overview

Hepatitis E has a worldwide distribution and causes substantial morbidity and mortality in some developing countries, particularly among pregnant women. Hepatitis E virus (HEV) has recently been cloned and sequenced and new diagnostic tests have been developed; these tests have been used to begin to characterize the natural history and epidemiologic features of HEV infection. Experimental vaccines have also been developed that offer the potential to prevent hepatitis E. However, to develop effective strategies to prevent this disease, much remains to be learned about HEV, including the vehicles of transmission, the reservoir(s) of the virus, and the natural history of protective immunity.

In situ detection of hepatitis C virus--a critical appraisal

Hepatitis C virus (HCV) is a single-stranded RNA virus that replicates at a low level. Accordingly, the detection of HCV RNA requires molecular techniques such as reverse transcription polymerase chain reaction and branched chain DNA signal amplification assay. Although very sensitive, these assays do not allow specific localization of HCV within the liver. In situ detection of HCV genome and gene products is important to allow for the identification of cellular tropism, obtaining clues to the subcellular site of viral replication, and defining host-viral interactions. In situ hybridization, in situ reverse transcription polymerase chain reaction and immunohistochemistry have been applied for the localization of HCV genome and gene products. However, all these techniques were found to have their limitations and conflicting results have been reported based on all three techniques. This review will critically discuss the available data with an attempt to assist researchers to further understand the potential limitations and possible ways to solve these problems. The development of better protocols for the detection and localization of HCV will help to provide a better understanding of the pathobiology of HCV which, in turn, will assist in the design of better therapeutic strategies.

Volunteer blood donors with antibody to hepatitis C virus: clinical, biochemical, virologic, and histologic features. The Hepatitis C Study Group

OBJECTIVE

To assess the clinical significance of antibody to hepatitis C virus (anti-HCV) in volunteer blood donors.

DESIGN

Prospective cohort study.

SETTING

National Institutes of Health Clinical Center, a tertiary referral research hospital.

PATIENTS

60 anti-HCV-positive blood donors, divided into three groups of 20 persons each: Group I had normal alanine aminotransferase levels, group II had levels elevated to values less than twice the normal range, and group III had levels elevated to values greater than twice the normal range.

MEASUREMENTS

Medical history, results of laboratory and virologic testing, and percutaneous liver biopsy findings.

RESULTS

Participants with normal alanine aminotransferase levels were older and more often female than those with abnormal levels. The source of infection, duration of disease, symptom score, and amount of alcohol consumed were similar in the three groups. Hepatitis C virus RNA was detectable in 85% of participants, more commonly in the groups with elevated alanine aminotransferase levels (95%) than in the group with normal levels (65%); however, titers were similar in all groups. Examination of liver biopsy specimens showed chronic hepatitis in 54 participants (90%) and cirrhosis in 1 participant. The only normal liver biopsy specimens (n = 3) were those from participants who were HCV RNA negative and had normal alanine aminotransferase levels.

CONCLUSIONS

Most blood donors with anti-HCV have chronic hepatitis C regardless of their serum alanine aminotransferase levels. Donors with normal alanine aminotransferase levels and no HCV RNA in their serum generally have normal liver histologic findings or minimal changes and have probably recovered from HCV infection.

Viral specificity of hepatitis E virus antigens identified by fluorescent antibody assay using recombinant HEV proteins

A fluorescent antibody (FA) assay for hepatitis E virus antigen (HEVAg) in infected liver tissue was used to confirm the presence of virus-specific antigens in hepatocytes during the course of infection. With the cloning of the HEV genome it is now possible to determine which viral antigens are recognized by this FA assay. Recombinant HEV proteins covering the carboxyl half of HEV open reading frame 2 (ORF2) were used in this study to demonstrate that some of the most immunoreactive virus-specific antigens detected by FA are contained within this region of ORF2 (nucleotides 6169-7126).

Hepatitis E

With the introduction of new, albeit noncommercial, diagnostic tests for the detection of HEV, our understanding of this virus has been greatly enhanced. With these tests, it has been possible to begin a delineation of the process of pathogenesis in infected humans. These tests have also shown us that, at least in some individuals, an IgG response to HEV is long lasting and may confer immunity, and it may be possible to develop a recombinant vaccine against HEV. Contrary to past results, HEV appears to be the most common cause of acute sporadic hepatitis in pediatric populations in endemic regions. HEV has been shown to be a positive-sense single-stranded RNA virus that has been tentatively classified as a calicivirus, although its nonstructural proteins exhibit sequence similarity to rubella virus and furoviruses. Despite these advances in our understanding of HEV, it is still necessary to depend on exclusion of hepatitis caused by other viruses to diagnose a hepatitis E infection; however, this situation should change with the anticipated release of commercially available diagnostic tests.

Effect of postexposure vaccination in a chimpanzee model of hepatitis A virus infection

Passive transfer of antibodies to hepatitis A virus (HAV) in immune globulin (IG) effectively prevents hepatitis A when given after exposure, but does not provide lasting protection from infection. Hepatitis A vaccines have been shown to generate quickly levels of antibody equivalent to those found after IG administration. The effect of hepatitis A vaccine in preventing infection following fecal-oral exposure was evaluated in a chimpanzee model of HAV infection. Two animals were vaccinated 1 and 3 days, respectively following inoculation and two inoculated animals served as unprotected controls. Of the two immunized animals, one had no evidence of HAV infection, while the other had an attenuated infection with no evidence of virus shedding. These results suggest that while postexposure hepatitis A vaccination may be infection permissive, it attenuates disease expression and prevents virus shedding.

Case report: role of hepatitis E virus in the etiology of community-acquired non-A, non-B hepatitis in Greece

The aim of this study was to determine the frequency of hepatitis E virus (HEV) infection in a population of Greek adults with community-acquired (sporadic) non-A, non-B hepatitis found to be seronegative for antibodies to hepatitis C virus (anti-HCV). All patients admitted to the Liver Unit of Western Attica General Hospital and diagnosed as having acute community-acquired non-A, non-B hepatitis between February, 1986, and May, 1990, were enrolled in follow up studies (n = 66). Nineteen patients with HCV infection and 11 patients with acute non-A, non-B, non-C hepatitis that progressed to chronicity were excluded. Convalescent sera were tested for antibody to HEV (anti-HEV) by a fluorescent antibody blocking assay in 33 of 36 eligible patients. One of the 33 (3%) patients was found to be positive for anti-HEV. Anti-HEV testing of all 20 available serum specimens from this patient showed evidence of anti-HEV seroconversion at the fourth week after the onset of hepatitis. The patient had not travelled abroad or within Greece or had not had apparent contact with people from foreign countries for the previous 3 months. These data show that HEV infection is not a major cause of community-acquired non-A, non-B hepatitis in Greece. However, the reported case of HEV hepatitis suggests that HEV may retain a low endemicity in Greece. More extensive seroprevalence studies are needed for an accurate estimation of the extent of HEV infection in the southeastern European countries.

Preliminary evidence that a trpE-HEV fusion protein protects cynomolgus macaques against challenge with wild-type hepatitis E virus (HEV)

Immunization of two cynomolgus macaques (cynos) with trpE-C2 protein, a trpE-HEV fusion protein that represents the carboxyl two thirds of the putative capsid protein, prevented development of biochemical evidence of viral hepatitis in these primates after challenge by wild-type HEV from either a Burmese or Mexican stool isolate. Neither of the immunized animals showed any elevation of alanine aminotransferase activity after challenge with wild-type HEV in marked contrast with the unimmunized (control) cynos. In the case of the Burmese HEV challenged cyno, the protective effect was complete with the animal failing to demonstrate any evidence of HEV infection. The immunized cyno challenged with Burmese HEV did not exhibit any HEV RNA in its stools or HEV antigen in its liver. The immunized cyno (#8902) challenged with Mexican virus exhibited HEV RNA in its stools and HEV antigen in its liver; however, microscopic examination of liver biopsy specimens from this cyno failed to detect histopathologic evidence of viral hepatitis. All of the animals (naive and immunized) developed anti-HEV IgM and IgG responses after HEV challenge. Our preliminary studies indicate that the trpE-C2 protein is a promising candidate HEV vaccine.

Changes in hepatitis C virus antigen in liver with antiviral therapy

BACKGROUND

Although it has recently become possible to detect hepatitis C viral antigens in liver biopsy specimens, the frequency and clinical significance of this finding remains uncertain. Therefore, 49 liver biopsy specimens from 35 patients with hepatitis C were studied to make these assessments.

METHODS

Hepatitis C virus antigen was detected by immunofluorescence staining of snap-frozen liver biopsy sections.

RESULTS

Hepatitis C virus antigen was present in 86% of patients; the amount and pattern of hepatitis C virus antigen staining did not correlate with the degree of hepatic injury as assessed by serum aminotransferase levels or liver histology or with the level of viral replication assessed by the titer of HCV RNA in serum. Patients who had a beneficial response to antiviral therapy had significantly less hepatitis C virus antigen staining in pretreatment liver biopsy specimens than those who did not respond. The degree of hepatitis C virus antigen staining decreased significantly following interferon alfa therapy but not after ribavirin therapy. Hepatic hepatitis C virus antigen became undetectable after therapy in those patients who had a long-term beneficial response to therapy.

CONCLUSIONS

Hepatic hepatitis C virus staining may be useful in predicting and monitoring the response to antiviral therapy.

Hepatitis E virus infection in pregnancy in Ethiopia

Thirty-two pregnant and 34 nonpregnant Ethiopian women between 15 and 45 years of age with sporadic acute viral hepatitis were studied consecutively. Demographic data including family size, monthly income and nutritional status as well as hepatitis virus markers were compared in the pregnant and nonpregnant groups. Only 3 nonpregnant women had hepatitis A infection. Hepatitis B infection was diagnosed in 4 pregnant and 9 nonpregnant women. Nineteen (59%) pregnant women had hepatitis E virus (HEV) infection as compared to 7 (22%) in the nonpregnant group (Relative risk = 2.88; 95% Confidence interval = 1.4-5.9). The remaining 9 pregnant and 15 nonpregnant women had non-A, non-B, non-E (NANBNE) hepatitis. Of a total of 10 maternal deaths, 9 occurred (7 during the third trimester) in the pregnant group, 8 in association with HEV infection. Two deaths, one from each group, were due to NANBNE hepatitis. In addition to 6 foetal losses as a result of maternal death, there were 2 foetal deaths and 7 premature deliveries as a direct result of acute viral hepatitis, all but 2 associated with HEV infection. Comparison of socioeconomic and nutritional status, clinical features, mean aminotransferase and bilirubin levels did not show differences in the two groups. Thus, pregnant women are more at risk to acquire HEV infection than nonpregnant women and HEV infection in this group of Ethiopian pregnant women is associated with high maternal mortality and neonatal complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Epitope mapping in proteins of hepatitis E virus

A series of synthetic peptides derived from proteins encoded by open reading frames 2 and 3 (ORF2 and ORF3) of the hepatitis E virus was used in an enzyme immunoassay to determine the localization of epitopes in these proteins. Five peptides spanning almost the entire ORF3 protein sequence and 12 peptides from the ORF2 protein were synthesized. Serum samples collected from outbreaks in three different regions of the world (Turkmenistan, Kenya, and Mexico) were analyzed by a peptide-based enzyme immunoassay. Primary analysis of the peptides was accomplished with the use of serum samples obtained from Middle Asia. Four of 5 peptides from the ORF3 protein and 4 of 12 peptides from the ORF2 protein specifically reacted with antibody from sera of HEV-infected patients. Peptides representing immunodominant epitopes were used for the analysis of serum samples from outbreaks in Kenya and Mexico. The data indicate that these synthetic peptides may be used to develop a diagnostic test to detect antibody to the hepatitis E virus.

Hepatitis E and hepatitis C virus infections among French soldiers with non-A, non-B hepatitis

Serologic markers of HCV and HEV were investigated in 74 French soldiers with non-A, non-B hepatitis and in 18 patients involved in an outbreak of non-A,non-B hepatitis in Algeria. Moreover, anti-HCV antibodies were detected in 13 patients with non-A,non-B hepatitis of parenteral origin. HEV antibodies were investigated in 61-65% of patients involved in the 2 enterically transmitted outbreaks of non-A,non-B hepatitis observed in Algeria and Chad. The third cluster of non-A,non-B hepatitis observed in French soldiers serving in French Guyana is more likely to be attributed to malaria prophylactic treatment with Amodiaquine than to a viral origin. HCV infection was observed in 93% of acute or chronic cases associated with blood transfusion or parenteral drug abuse. Among acute cases, none of the soldiers who contracted the disease in Africa or in French Guyana was found to be anti-HCV positive compared to 78% of those who contracted the disease in France. HCV infections resulted in chronic hepatitis in 61% of cases.

The natural history of community-acquired hepatitis C in the United States. The Sentinel Counties Chronic non-A, non-B Hepatitis Study Team

BACKGROUND

Chronic liver disease develops in more than half of patients with post-transfusion hepatitis C, but little is known about the natural history of community-acquired hepatitis C.

METHODS

In 1985 and 1986 we identified adults with acute non-A, non-B hepatitis in four counties in the United States and followed them prospectively. We used three markers to detect hepatitis C virus (HCV) infection in stored samples of serum: antibody to HCV (anti-HCV) detected by second-generation serologic assays; HCV RNA detected by polymerase-chain-reaction assay; and antibody to HCV antigen (anti-HCVAg) detected by fluorescent-antibody-blocking assay.

RESULTS

Of 130 patients with non-A, non-B hepatitis, 106 (82 percent) had HCV infection, 93 were positive for anti-HCV, and 13 were positive only for HCV RNA or anti-HCVAg. Chronic hepatitis developed in 60 (62 percent) of 97 HCV-infected patients followed for 9 to 48 months, with no relation to the risk factors for infection. Ten of the 30 patients who had liver biopsies had chronic active hepatitis. In samples collected 42 to 48 months after the onset of hepatitis, HCV RNA was detected in 12 of 13 tested patients with chronic hepatitis and in all 15 tested patients with hepatitis that had resolved. Anti-HCV persisted in all but two of the initially positive patients, for a rate of antibody loss of 0.6 per 100 person-years.

CONCLUSIONS

Patients with community-acquired hepatitis C have a high rate of chronic hepatitis. HCV may be a major cause of chronic liver disease in the United States, and in most patients HCV infection seems to persist for at least several years, even in the absence of active liver disease.

Histopathology of community acquired chronic hepatitis C. The Sentinel Counties Chronic Non-A, Non-B Hepatitis Study Team

As part of a study of community-acquired non-A, non-B hepatitis, liver biopsy specimens of 29 anti-HCV positive and four anti-HCV negative patients were evaluated in order to characterize the histopathologic changes of chronic hepatitis C. Liver biopsies were performed 6 to 46 mo after onset of the disease and repeat biopsies were obtained in 10 anti-HCV positive patients. The histologic diagnoses were chronic persistent hepatitis (45%), chronic active hepatitis (35%), and chronic lobular hepatitis (21%). Irrespective of the tissue diagnosis, the majority of the patients showed characteristic histologic abnormalities in the liver, particularly damage of the small and medium-sized bile ducts (76%), lymphoid aggregates in portal tracts (45%), enlarged macrophages (48%), and steatosis (31%). In 59% of the patients, two or more of these histologic abnormalities were combined. Similar histologic changes have previously been observed in non-A, non-B hepatitis, but only uncommonly in hepatitis A or hepatitis B. We conclude that the histopathologic findings in chronic hepatitis C are highly characteristic, although not pathognomonic.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatitis C virus antigen in hepatocytes: immunomorphologic detection and identification

Hepatitis C virus (HCV) antigen was detected immunohistochemically using fluorescein isothiocyanate-labeled immunoglobulin G fractions from chimpanzee and human sera strongly reactive with recombinant hepatitis C virus structural and non-structural proteins. The antigen was localized in the cytoplasm of hepatocytes in all 9 chimpanzees with acute hepatitis C, in 5 of 10 chimpanzees with chronic HCV infection, and in 11 of 12 patients with chronic hepatitis C. The specificity of the hepatocellular HCV and FITC-labeled probes for HCV was ascertained by blocking studies with paired serum samples obtained from 8 infected and uninfected chimpanzees or from 14 patients during the acute and chronic phases of HCV infection. Absorption experiments on FITC-labeled probes with selected host proteins (normal liver homogenate, plasma proteins, red blood cells) did not indicate cross reactivity of the probes with these antigens. Direct immunomorphologic evidence for the HCV specificity of hepatocellular HCV antigen deposits and the FITC-labeled polyclonal anti-HCVAg probe was established in absorption experiments using recombinant HCV nonstructural proteins. The putative HCV NS3 protein was the most prominent component of hepatocellular HCV antigen.

Acute sporadic hepatitis E in Sudanese children: analysis based on a new western blot assay

A newly developed Western blot assay for antibody to hepatitis E virus (anti-HEV) was used to evaluate 39 cases of acute pediatric hepatitis and 39 control patients in Khartoum, Sudan. The mean age of cases was 6.5 years (range, 2-14); 64% were male. Acute hepatitis A (IgM anti-HAV-positive) was diagnosed in 13 cases, acute hepatitis B (IgM anti-HBc-positive) in 1, and acute hepatitis E (positive for IgM anti-HEV) in 23 (59%). None of the cases with IgM anti-HAV or IgM anti-HBc had IgM anti-HEV; 3 controls had IgM anti-HEV. Acute hepatitis E was associated with recent contact with a family member or acquaintance with jaundice and the presence of indoor plumbing. The newly developed hepatitis E assay appeared to be specific for the diagnosis of acute icteric non-A, non-B hepatitis. Hepatitis E was found to be the most common cause of acute sporadic hepatitis in children living in an urban area of Africa.

Temporal relationships of hepatitis C virus RNA and antibody responses following experimental infection of chimpanzees

Liver enzyme levels, viral RNA, and the immune response against both structural and nonstructural hepatitis C virus (HCV) proteins have been studied in experimentally infected chimpanzees in order to further understand the natural history of HCV infection. An ELISA for measuring both IgG and IgM responses to core (c22), 33c (NS3), and c100 (NS4) was employed. The IgG response rates were 5/8 for core, and 8/8 for both 33c and c100. Utilizing this antigen combination, at least one antibody response is measureable at, or within 3 weeks of, the major ALT peak. Although no individual antibody response is universally associated with initial detection of seroconversion, the combination of all three recombinant proteins measures seroconversion an average of 54 days earlier than with c100 alone, in 6/8 of the animals. IgM responses were measureable in 5/8 of the chimpanzees, were of shorter duration, and usually arose concomitantly with IgG responses. IgM appears to be a good indicator of primary infection since neither boosting nor recrudescence of disease during the chronic phase of disease elicited a secondary IgM response. Viral RNA can be measured 4-7 days (average = 9 days) postinfection with the period preceding the ALT peak being characterized by several PCR positive segments interrupted by periods in which no viral RNA can be measured. Following the ALT peak, chronically infected animals with recurring ALT elevations are generally PCR positive with intercedent PCR negative periods. Those animals that appear to have biochemically resolved disease generally have PCR negative profiles, although they still may periodically exhibit PCR positive sera. This indicates that with the recent advent of new screening techniques, a more stringent definition of HCV resolution will be required.

Expression of a hepatitis E virus (HEV)-trpE fusion protein containing epitopes recognized by antibodies in sera from human cases and experimentally infected primates

A 1700 base cDNA fragment coding for the putative structural gene(s) of hepatitis E virus (HEV) was inserted into the pATH 10 expression vector. The fusion protein (C2) expressed by this plasmid was found to contain epitopes recognized by anti-HEV antibodies. C2 protein was used in a Western blot format to examine its usefulness in detecting anti-HEV antibodies in well documented human cases of HEV and non-human primates infected with HEV. Both IgM and IgG anti-HEV could be detected in our Western blot assay. This Western blot assay was found not to detect antibodies from acute-phase sera from patients with either HAV or HBV. The C2 protein contains broadly cross-reactive epitopes, and the Western blot assay was able to detect anti-HEV antibodies in patient sera from Asia, Africa, and North America. The optimum serum dilution for the detection of both IgM and IgG was 1:25.

Human linear B-cell epitopes encoded by the hepatitis E virus include determinants in the RNA-dependent RNA polymerase

Hepatitis E virus is responsible for both sporadic and epidemic hepatitis in developing countries. The nonenveloped virus is 27-34 nm in diameter and has been shown to contain a single-strand, positive-sense, polyadenylylated RNA genome of approximately 7.5 kilobases. The nucleotide sequence of the Burma strain of hepatitis E virus has been reported and three open reading frames (ORFs) have been identified. The deduced amino acid sequence from each of these ORFs was used to synthesize overlapping peptides (decamers overlapping at every fourth amino acid) on a solid phase. These peptides were then tested in an ELISA with pooled acute-phase sera from known cases of enterically transmitted non-A, non-B hepatitis collected in the Sudan. Linear B-cell epitopes were identified in all three ORFs. Epitopes were identified throughout the polyprotein encoded by ORF1, but they appeared to be particularly concentrated in the region of the RNA-dependent RNA polymerase. Distinct epitopes were identified in the presumed structural protein encoded by ORF2, and one epitope was identified close to the carboxyl terminus of the protein encoded by ORF3. These data precisely pinpoint linear B-cell epitopes recognized by antibodies from patients with acute hepatitis E and identify an antibody response directed against the RNA-dependent RNA polymerase.

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.

Acute sporadic viral hepatitis in Ethiopia: causes, risk factors, and effects on pregnancy

One hundred and ten consecutive cases of acute sporadic hepatitis among Ethiopian patients were studied to define viral causes, identify risk factors, and analyze demographic and clinical data. IgM antibodies to hepatitis A virus were found in nine patients (8%), and hepatitis B surface antigen and IgM antibodies to hepatitis B core antigen were found in 22 (20%); these findings were considered evidence of acute hepatitis A and hepatitis B, respectively. Sera from the remaining 79 patients were tested for antibodies to hepatitis E virus by a blocking fluorescent antibody test. Thirty-six (33%) of these patients were seropositive, as compared to 4 (7%) of 59 healthy control subjects; for 43 patients (39%), the cause of the acute sporadic hepatitis was unidentified. Twenty-one (19%) of the patients had antibodies to hepatitis C virus, as determined by ELISA. Demographic, biochemical, and clinical data (except in regard to sequelae) were comparable for the different types of infections. The study subjects included 32 pregnant women, 19 (59%) of whom had hepatitis E virus infection; these infections caused death in eight of the women (mostly in the third trimester) and 10 fetal complications. Thus, hepatitis E virus is a common cause of acute sporadic viral hepatitis in Ethiopian patients, and its occurrence during pregnancy is associated with high maternal and fetal morbidity and mortality.