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.

Taxonomy of the caliciviruses.

The International Committee on Taxonomy of Viruses (ICTV) has recently approved several proposals submitted by the present Caliciviridae Study Group. These proposals include the division of the family into 4 new genera designated Lagovirus, Vesivirus, "Norwalk-like viruses (NLVs), and "Sapporo-like viruses (SLVs); the latter 2 genera were assigned temporary names until acceptable names can be determined by the scientific community. The genera have been further divided into the following species: Feline calicivirus and Vesicular exanthema of swine virus (genus Vesivirus), Rabbit hemorrhagic disease virus and European brown hare syndrome virus (genus Lagovirus), Norwalk virus (genus NLV), and Sapporo virus (genus SLV). In addition, the ICTV approved a proposal to remove the hepatitis E virus from the Caliciviridae into an "unassigned classification status.

Antibody to hepatitis E virus in HIV-infected individuals and AIDS patients.

Antibody to hepatitis E virus of IgG class (anti-HEV IgG) is regularly detected in industrialized countries, where HEV is non-endemic, at levels not exceeding 2-3%; seropositive individuals are often found in certain groups of patients and professionals exposed to an increased risk of blood-borne infections. The present study was aimed at the identification of anti-HEV IgG in patients with human immunodeficiency virus (HIV) infection, including acquired immune deficiency syndrome (AIDS), living in Russia and Belarus, an area of low anti-HEV prevalence with a moderate spread of HIV infection and AIDS. In Russia, 13 out of 117 HIV-infected patients (11.1%) were found to be anti-HEV seropositive. This differed significantly from the frequency observed in the normal population (1.7%) but not from the frequency in a matching control, high-risk group consisting of male prisoners (8.0%). No difference in the frequency of anti-HEV IgG seropositivity was found between groups of HIV-infected men subdivided by sexual orientation. The rate of anti-HEV seropositivity increased with the progression of HIV infection, reaching 43.3% in AIDS patients and 38.1% in those who died from AIDS. In Belarus, anti-HEV IgG seropositivity was not found among 20 HIV-infected subjects nor among individuals from the control risk group, which consisted of 25 intravenous drug users. In conclusion, HEV infection may have common transmission mechanisms (risk factors) with HIV infection rather than represent an additional opportunistic infection in AIDS.

Epidemiology of hepatitis E virus infection.

Hepatitis E is an acute, icteric, self-limiting disease, which is spread widely in many tropical and subtropical countries where it occurs both in the form of epidemics of variable magnitude or sporadically. Hepatitis E affects young adults, rather than children, and causes a high mortality rate, particularly in pregnant women. In industrialized countries this disease occurs occasionally as imported sporadic cases. The aetiological cause of hepatitis E is a virus, hepatitis E virus (HEV), which is temporally classified as a member of the Calicivirus family, although its genomic composition is unique. There are experimental data as well as epidemiological observations allowing us to assume that hepatitis E may be a zoonosis as HEV is pathogenic for some domestic and wild animals. Recently, serological assays based on the use of recombinant or synthetic antigens were developed and applied to determine the prevalence of antibody to HEV (anti-HEV) in various epidemic and non-epidemic settings. In suspected hepatitis E cases, anti-HEV seropositivity was detected at an elevated rate but the overall seroprevalence of anti-HEV in normal human populations of endemic areas appeared to be unexpectedly low. A low but constant presence of anti-HEV seropositivity was observed also in non-endemic industrialized countries. In some of these countries, anti-HEV seropositivity was accumulated in groups of patients with various liver and non-liver pathologies and certain groups at risk for blood-borne infections.

Serological survey on hepatitis E virus infection in an endemic area: diagnosis potential of enzyme immunoassay for detection of IgG antibody.

BACKGROUND: Hepatitis E is a major cause of acute icteric disease widespread in tropical and sub-tropical regions but rarely occurring in industrialized countries. Recently solid-phase enzyme immunoassays with recombinant antigens have been introduced for diagnosis of this infection. OBJECTIVES: The aim of this study was to evaluate the diagnostic potential of a newly developed Abbott test for the detection of IgG class antibodies to hepatitis E virus (anti-HEV IgG) in hepatitis patients and 'normal' individuals. STUDY DESIGN: Sera taken from hepatitis patients and individuals without liver disorders in endemic (Kirghizstan and Uzkbekistan) versus non-endemic (Moscow) areas were investigated. In parallel IgG class antibodies to hepatitis A virus (anti-HAV IgG) were determined by an enzyme immunoassay with native HAV antigen. RESULTS: In five groups comprising altogether 86 suspected hepatitis E patients from endemic area the rate of anti-HEV IgG seropositivity varied from 85% to 17%. In Moscow anti-HEV IgG was found in one patient (who also had acute hepatitis B) out of 19. Anti-HEV IgG persisted in an experimentally infected volunteer for at least 12 years after the acute disease. Among the individuals without liver disorders eight out of 173 (4.6%) showed anti-HEV IgG seropositivity in Kirghizstan while there was only one seropositive out of 165 (0.6%) in Moscow. In contrast, anti-HAV IgG were frequently present in the residents of both areas: in Kirghizstan over 90% of individuals from young age groups already had these antibodies; in Moscow the rate of anti-HAV IgG seropositivity constantly increased from 31% in the youngest age group to almost 85% in the oldest one. CONCLUSION: Prevalence of anti-HEV antibodies was unexpectedly low in endemic area; in Moscow anti-HEV IgG was found only in single cases. Anti-HEV IgG seropositivity in a single serum sample could be of certain diagnostic value in non-endemic areas.

Hepatitis E virus infection in Europe: regional situation regarding laboratory diagnosis and epidemiology.

Hepatitis E virus (HEV) was first identified in the excreta of an experimentally infected human volunteer and further confirmed by similar findings in clinical specimens from patients with acute jaundice disease different from hepatitis A and B. The HEV is a 27- to 34-nm spherical non-enveloped virus obviously represented by a single serotype; however, its final taxonomic definition remains to be established. Studies on molecular biology of this virus revealed some peculiar characteristics showing no homologies in its nucleotide sequence to any entries in the Genbank database. The HEV infection was experimentally transmitted to non-human primates producing a disease in many features similar to that occurring in humans. Recently cell lines persistently infected with the HEV have also been obtained. These studies provided valuable virus-specific reagents which were used in diagnostic tests. Currently immune electron microscopy, fluorescent antibody technique, latex agglutination, cDNA hybridization, and Western blotting are employed to prove the etiological involvement of HEV in suspected hepatitis cases; serological tests with synthetic substances analogous to HEV antigens are expected to be available soon. Reliable diagnostic procedures can be carried out in a number of laboratories with the locally produced reagents. The HEV infection is common in many hot climate countries being responsible for more than 50% of jaundice cases among young adults. The European region is considered to be free of natural foci of this infection, however, several sporadic cases of HEV disease were reported to occur in Europeans who developed jaundice shortly after returning from endemic areas. It is suspected that in the Mediterranean countries (Italy and Spain) the cases of HEV infection could be causatively related to the consumption of shell-fish cultivated in sewage-polluted waters.

Identification of precursors of structural proteins VP1 and VP2 of hepatitis A virus.

The morphogenetic pathway of hepatitis A virus (HAV), classified as a member of the enteroviruses within the Picornaviridae, still remains obscure and seems to differ considerably from that of poliovirus, the most studied representative of this genus. In order to elucidate the precursor/product relationship of HAV structural proteins, subviral particles, which represent more than 50% of the viral antigen produced in infected cells, were separated from mature virions and their polypeptide pattern was analyzed by polyacrylamide gel electrophoresis and immunoblotting using monospecific antisera. Whereas mature virions are composed of viral proteins VP1, VP2, and VP3, subviral particles contained VP0 and smaller polypeptides instead of VP2. Comparison of proteins of different strains of HAV showed that VP0 of strain HAS-15 migrated slower than that of strains MBB or GBM. During the course of the infectious cycle, VP0 accumulated and only small portions were converted to VP2 supporting earlier observations that encapsidation of RNA with concomitant cleavage of VP0 is rate-limiting, leaving a large amount of viral antigen in premature particles. Similar to VP0, accumulation of VP1 was observed and two immunologically related precursor proteins, p38 and p36, were found during the course of infection. Immunological characterization of p38 using antisera directed to the N-terminus of VP1 and to synthetic peptides located at the presumptive C- and N-termini of 2A suggests that p38 is VP1 delta 2A carrying 45 N-terminal amino acids of the P2-region.

Immunogenicity of inactivated purified tissue culture vaccine against hepatitis A (HepAvac) assessed in laboratory rodents.

Immune response of laboratory rodents (guinea-pigs, CBA and Balb/c mice, Wistar and August rats) to inactivated hepatitis A vaccine was quantitatively assessed. Under comparable conditions of experiment, the mice showed the highest antibody titres and were capable of reacting to the lower doses of immunogen; meanwhile their individual variations in immune response were more pronounced; white rats were the least susceptible to the vaccine, demonstrating the minimal antibody formation; guinea-pigs produced antibody at intermediate levels but the antibody titres were the most homogeneous. The enhancing effect of aluminium hydroxide was observed in guinea-pigs examined at the late postimmunization stage. Differences in immunogenicity of three vaccine lots were essentially similar when these lots were tested as undiluted preparations in guinea-pigs and mice for mean antibody titres and in mice for 50% immune response using serial dilutions of vaccine. All three tests could be routinely employed for vaccine immunogenicity control.

Natural hosts of hepatitis A virus.

The host range for hepatitis A virus (HAV) is limited to man and several species of non-human primates, and involvement of vertebrates other than primates in HAV circulation is unlikely. Spontaneous hepatitis A infection has been reported to occur in captive non-human primates including the great apes (chimpanzee) as well as Old World (cynomolgus, African vervet, stump-tailed) and New World (aotus) monkeys. The presence of anti-HAV antibody in the sera of newly captured monkeys of these species shows that infection may also spread in their natural habitat. HAVs isolated from spontaneously infected monkeys, although antigenically closely related to human HAV, exhibit a significant degree of genomic heterogeneity. There are at least four distinct simian HAVs differing from each other and from all human HAV strains. It is suggested that each virus is native to a given species reflecting evolutionary relationships among HAVs and their hosts in the order of Primates.

Immunogenicity trial of inactivated hepatitis A virus vaccine in human volunteers.

An inactivated hepatitis A virus (HAV) vaccine was tested on a group of human adult volunteers. The vaccine was administered subcutaneously, and a control group received a placebo (aluminium hydroxide). The vaccine was found to be relatively well tolerated and non-reactogenic, and levels of anti-HAV were comparable to those in other studies.

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.

Variations in genome fragments coding for RNA polymerase in human and simian hepatitis A viruses.

The genome of hepatitis A virus (HAV) isolated from spontaneously infected African vervet monkey (Cercopithecus aethiops) has been cloned and partially sequenced. Comparison of genome fragments (1248 and 162 bp) from the 3D (RNA polymerase) region with the corresponding parts of human HAV genomes revealed a high degree of heterogeneity: there were altogether 257 nucleotide changes leading to 44 substitutions in predicted amino acid sequence, i.e. 89% amino acid identity. This divergence is considered to be significantly greater than genomic variations usually found among human HAV strains, where amino acid identity in the 3D region is over 98%.

Shifts in the rates and levels of antibody to hepatitis A virus associated with hepatitis A infection in children's communities.

In order to investigate the shift in the rates and levels of antibody to hepatitis A virus, 567 children in 20 isolated groups of five day-care centers were observed over a period of 8 months during which the seasonal rise in hepatitis A morbidity occurs. Increases in the proportion of seropositive ranging from 5 to 37% were demonstrated in 6 groups, and were always associated with the occurrence of either overt or sub-clinical hepatitis A infection. High rates of seropositivity were also noted in the groups in which cases of hepatitis A had been registered prior to the period of observation. In some children with low and medium antibody levels, antibody titres showed further increases after reinfection. A substantial part of children retained low antibody titres during the entire period of observation, and eight previously sero-negative children developed low antibody levels after asymptomatic hepatitis A infections. In one group the spread of hepatitis A infection (clinical and asymptomatic) was prevented by the administration of commercially available immunoglobulin immediately after the discovery of an infected food handler. Passive antibodies were found in previously sero-negative children, and these antibodies dropped to undetectable levels two months after administration.

Non-A, non-B fulminant viral hepatitis in France in returnees from Asia and Africa.

Among 61 patients admitted for non-A, non-B fulminant viral hepatitis to Hôpital Beaujon, 10 had returned from Asia or Africa, and 51 had not been outside France, within the month preceding jaundice. This suggests that hepatitis might have been contracted in Asia or Africa in the former, and in France in the latter. The interval between the onset of jaundice and the onset of hepatic encephalopathy was 10 days in the former and 26 days in the latter (P less than 0.03). The serum of the patient returning from Asia contained, and the sera of the nine patients returning from Africa did not contain, antibodies to a virus isolated from the stools of patients suffering from an epidemic fecal-oral non-A, non-B viral hepatitis in Central Asia. It is concluded that infection with Asian-African non-A, non-B viruses can be the cause of fulminant hepatitis in persons returning from these countries, that the course of this type of non-A, non-B fulminant viral hepatitis is shorter than that of non-A, non-B fulminant hepatitis contracted in France, and that different viruses might be responsible for non-A, non-B hepatitis in Asia and Africa.