Age-specific prevalence of antibodies to hepatitis A and E viruses in Pune, India, 1982 and 1992

The age-specific seroprevalence of antibody to hepatitis A virus (HAV) and antibody to hepatitis E virus (HEV) were studied in persons in Pune, India, where both viruses are endemic. The data showed that HAV infected the majority of persons by age 3 years and virtually 100% by late childhood. In contrast, infection with HEV was rare in children and did not reach peak prevalence (33%-40%) until early adulthood. The reason for the differences in infection rates between HAV and HEV is not known. Age-specific antibody patterns in serum samples obtained 10 years apart show that neither HAV nor HEV has diminished in medical importance in this Indian community.

Long-term efficacy of active postexposure immunization of infants for prevention of hepatitis B virus infection. United States-People's Republic of China Study Group on Hepatitis B

Perinatal transmission of hepatitis B virus (HBV) contributes to the high prevalence of chronic infection in China and many other countries. In a placebo-controlled trial among 166 infants, the 12-month efficacy of active postexposure prophylaxis to prevent chronic perinatal HBV infection varied by vaccine (range, 45%-89%). In a 5-year follow-up study, 2 additional infants became chronically infected with HBV, and the efficacy of active prophylaxis was estimated to be 38% and 72% for the two vaccines at 5 years. In addition, 80% of immunized infants continued to have protective levels of antibody at the end of 5 years. However, among 27 infants who received passive-active immunoprophylaxis with high-dose hepatitis B immune globulin, only 60% (11/19) had protective antibody levels. These data indicate that active postexposure immunization initiated soon after birth continues to provide protection during early childhood when there is a high risk of chronic HBV infection.

Hepatitis C and its sequelae: the biology of hepatitis C virus and implications for its control

Hepatocellular carcinoma is one of the most important cancers worldwide and at least two hepatitis viruses, hepatitis B virus (HBV) and hepatitis C virus (HCV) appear to be etiologically associated with its development. Regardless of the nature of this association, control of these two viruses would likely be effective in the prevention of hepatocellular carcinoma. The control of HBV is achievable through proper utilization of highly effective vaccines against HBV. However, the development of useful vaccines against HCV will require more knowledge about the genetic and serologic heterogeneity of this virus and the nature of the host's immune response to it.

Analysis of the X gene promoter of woodchuck hepatitis virus

During the course of woodchuck hepatitis virus (WHV) replication three virus-specific mRNA transcripts that encode four essential proteins are produced. The transcripts are 3.6, 2.3, and 0.7 kb in size. The 3.6-kb transcript serves as the replicative intermediate as well as the template for translation of the nucleocapsid and polymerase proteins. The 2.3-kb mRNA serves as the template for translation of the virus envelope proteins. Both the 3.6- and 2.3-kb transcripts are polyadenylated and are readily found in the cytoplasm of infected hepatocytes. However, the 0.7-kb transcript, specific for the X gene, accumulates in the nucleus of infected cells and is polyadenylated poorly in hepatocytes. Thus, while it is likely that the 0.7-kb transcript is the template for translation of the X protein, it is possible that it also has a function at the RNA level to regulate virus replication or gene expression. In order to characterize the WHV X promoter we cloned the region of the WHV8 genome encompassing the viral enhancer through the amino terminus of the X gene into the vector pSV0CAT. We transfected Huh-7 and WLC-3 cells with the WHV X promoter construct, along with a plasmid encoding human growth hormone to control for transfection efficiency, and assayed for the presence of chloramphenicol acetyl transferase activity. We found that the WHV X promoter was about one-half as active as the well-studied simian virus 40 early or Rous sarcoma virus promoters. Next, we made a series of 5' and 3' deletion mutants and mapped the WHV X promoter to a 21-nucleotide domain (1482-GGGGAAGCTGACGTCCTTTCC-1502) which is approximately 100 bp downstream of the corresponding promoter in hepatitis B virus. Further analysis, using oligonucleotide-directed mutagenesis, demonstrated that the essential nucleotides comprising the WHV X promoter are located in a 10-nucleotide domain near the initiation codon of the X gene. Mutation of either nucleotide T at position 1490 or G at position 1491 within this domain was sufficient to reduce the level of promoter activity by 100-fold. Thus, we have defined the important nucleotides within the promoter of the WHV X transcript which is a first step in understanding the role of this transcript in WHV replication and gene expression.

Expression of the c-myc protooncogene product in cells infected with the hepatitis delta virus

The intrahepatic accumulation of the c-myc protooncogene product was observed on immunofluorescence in each of six patients with chronic hepatitis delta virus infection who exhibited the hepatitis D antigen in their livers. The c-myc product was stained in the same nuclei that contained the hepatitis D antigen. C-myc was not observed in acute hepatitis D or in cases of chronic hepatitis delta virus infection without expression of the hepatitis D antigen. The protooncogene product was detected in only 1 of 32 viral and nonviral liver disorders unrelated to hepatitis delta virus. To confirm these observations, we transfected HBsAg-positive (PCL/PRF/5) and HBsAg-negative (HepG2) transformed liver cell lines with a plasmid containing a hepatitis delta virus cDNA trimer under the control of the SV40 early enhancer/promoter sequences. Whereas baseline c-myc expression was barely detectable in mock-transfected PLC/PRF/5 or HepG2 cells, strong c-myc nuclear fluorescence was observed when these same cells were transfected with the hepatitis D antigen expression vector. Similar results were obtained after infection of HeLa cells with a recombinant vaccinia virus expressing the hepatitis D antigen. Detection of c-myc mRNA sequences by means of in situ hybridization suggested that the c-myc product accumulation was not due to increased amounts of its mRNA. The c-myc protein accumulates selectively in the livers of patients with chronic hepatitis delta virus infection and in the same nuclei that contain the hepatitis D antigen. The expression of c-myc in hepatitis D antigen-containing cells does not require the presence of hepatitis B virus infection.

Hepatitis C virus: historical perspective and current concepts

Over the past 30 years, hepatitis C has emerged from shadowy enigma to important public health problem. The existence of the etiological agent of this disease was first appreciated two decades ago but significant progress in its understanding had to await its molecular characterization within the past 5 years. The virus is a member of the family Flaviviridae and is the cause of approximately 20% of clinical viral hepatitis in the United States. While the control of the transmission of hepatitis C virus in blood and blood products has been nothing less than spectacular, the control of community-acquired hepatitis C will be a major challenge to the scientific and medical communities.

Successful passive and active immunization of cynomolgus monkeys against hepatitis E

Virtually full protection against hepatitis E and partial or complete protection against infection with hepatitis E virus (HEV) were achieved in passively or actively immunized cynomolgus monkeys. Hepatitis, viremia, and shedding of the virus in feces were detected in all nonimmunized animals that were challenged with HEV. HEV titers detected by reverse transcriptase PCR were higher in feces than in serum of nonimmunized animals. Anti-HEV antibody titers at the time of challenge ranged between 1:40 and 1:200 in animals passively immunized with convalescent plasma from a cynomolgus monkey previously infected with HEV and between 1:100 and 1:10,000 in animals actively immunized with a recombinant 55-kDa open reading frame 2 protein. The estimated 50% protective titer of passively acquired anti-HEV antibodies was 1:40. Although only one of four passively immunized animals showed histopathologic evidence of hepatitis, all four were infected after challenge; however, the titers of HEV in serum and feces were lower in the passively immunized animals than in the nonimmunized group. The actively immunized animals developed neither hepatitis nor viremia when challenged with HEV and virus was either not detected or was present in low titer in feces. The protective response was a function of the ELISA anti-HEV antibody titer at the time of challenge and the immunization schedule.

A new Chinese isolate of hepatitis E virus: comparison with strains recovered from different geographical regions

The full-length cDNA of a new Chinese strain (KS2-87) of Hepatitis E virus (HEV) has been constructed and sequenced. The 5' noncoding region of KS2-87 is 26 nucleotides in length, which is one nucleotide shorter than that of HEV (B1) (Burma) and 23 nucleotides longer than that of HEV (Mexico). Comparison of the nucleotide and amino acid sequences of KS2-87 with all other published HEV sequences showed that KS2-87 was closer to two other Chinese strains (CHT-88, CHT-87) and SAR-55 (Pakistan) than to HEV (B1) and HEV (B2) (Burma) or HEV (Mexico). Comparisons of partial sequences of genes encoding a nonstructural and a structural protein revealed the existence of genetically related groups of HEV within geographical regions, whereas larger nucleotide differences were seen among isolates that were more geographically and epidemiologically distant.

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.

Sequence analysis of the core gene of 14 hepatitis C virus genotypes

We previously sequenced the 5' noncoding region of 44 isolates of hepatitis C virus (HCV), as well as the envelope 1 (E1) gene of 51 HCV isolates, and provided evidence for the existence of at least 6 major genetic groups consisting of at least 12 minor genotypes of HCV (i.e., genotypes I/1a, II/1b, III/2a, IV/2b, 2c, V/3a, 4a-4d, 5a, and 6a). We now report the complete nucleotide sequence of the putative core (C) gene of 52 HCV isolates that represent all of these 12 genotypes as well as two additional genotypes provisionally designated 4e and 4f that we identified in this study. The phylogenetic analysis of the C gene sequences was in agreement with that of the E1 gene sequences. A major division in the genetic distance was observed between HCV isolates of genotype 2 and those of the other genotypes in analysis of both the E1 and C genes. The C gene sequences of 9 genotypes have not been reported previously (i.e., genotypes 2c, 4a-4f, 5a, and 6a). Our analysis indicates that the C gene-based methods currently used to determine the HCV genotype, such as PCR with genotype-specific primers, should be revised in light of these data. We found that the predicted C gene was exactly 573 nt long in all 52 HCV isolates, with an N-terminal start codon and no in-frame stop codons. The nucleotide and predicted amino acid identities of the C gene sequences were in the range of 79.4-99.0% and 85.3-100%, respectively. Furthermore, we mapped universally conserved, as well as genotype-specific, nucleotide and deduced amino acid sequences of the C gene. The predicted C proteins of the different HCV genotypes shared the following features: (i) high content of proline residues, (ii) high content of arginine and lysine residues located primarily in three domains with 10 such residues invariant at positions 39-62, (iii) a cluster of 5 conserved tryptophan residues, (iv) two nuclear localization signals and a DNA-binding motif, (v) a potential phosphorylation site with a serine-proline motif, and (vi) three conserved hydrophilic domains that have been shown by others to contain immunogenic epitopes. Thus, we have extended analysis of the predicted C protein of HCV to all of the recognized genotypes, confirmed the existence of highly conserved regions of this important structural protein, and demonstrated that the genetic relatedness of HCV isolates is equivalent when analyzing the most conserved (i.e., C) and the most variable (i.e., E1) genes of the HCV genome.

Prevention of hepatitis C virus infection in chimpanzees after antibody-mediated in vitro neutralization

Hepatitis C virus (HCV) is the most important etiologic agent of non-A, non-B hepatitis and is a major cause of chronic liver disease and hepatocellular carcinoma. Development of an effective vaccine would be the most practical method for prevention of the infection, but whether infection with HCV elicits protective immunity in the host is unclear. Neutralization of HCV in vitro was attempted with plasma of a chronically infected patient, and the residual infectivity was evaluated by inoculation of eight seronegative chimpanzees. The source of HCV was plasma obtained from a patient during the acute phase of posttransfusion non-A, non-B hepatitis, which had previously been titered for infectivity in chimpanzees. Neutralization was achieved with plasma obtained from the same patient 2 yr after the onset of primary infection but not with plasma obtained 11 yr later, although both plasmas contained antibodies against nonstructural and structural (including envelope) HCV proteins. Analysis of sequential viral isolates from the same patient revealed significant genetic divergence as early as 2 yr after infection. However, the HCV recovered from the patient 2 yr after the infection had a striking sequence similarity with the HCV recovered from one of the chimpanzees inoculated with the acute-phase virus, suggesting that the progenitor of the new strain was already present 2 yr earlier. This evidence, together with the different sequences of HCV recovered from the chimpanzees that received the same inoculum, confirms that HCV is present in vivo as a quasispecies. These results provide experimental evidence in vivo that HCV infection elicits a neutralizing antibody response in humans but suggest that such antibodies are isolate-specific. This result raises concerns for the development of a broadly reactive vaccine against HCV.

Hepatitis C virus: historical perspective and current concepts

Over the past 30 years, hepatitis C has emerged from shadowy enigma to important public health problem. The existence of the etiological agent of this disease was first appreciated two decades ago but significant progress in its understanding had to await its molecular characterization within the past 5 years. The virus is a member of the family Flaviviridae and is the cause of approximately 20% of clinical viral hepatitis in the United States. While the control of the transmission of hepatitis C virus in blood and blood products has been nothing less than spectacular, the control of community-acquired hepatitis C will be a major challenge to the scientific and medical communities.

Infectivity titration of a prototype strain of hepatitis E virus in cynomolgus monkeys

The infectivity titer of a standard stock of the SAR-55 strain of hepatitis E virus (HEV) was determined in cynomolgus macaques (Macaca fascicularis) and the effect of dose on the course of the infection was examined by weekly monitoring of alanine aminotransferase (ALT) and anti-HEV levels. Antibody to HEV (anti-HEV) was measured with ELISAs based on ORF-2 recombinant antigens consisting of either a 55 kDa region expressed in insect cells or shorter regions expressed as fusion proteins in bacteria. The ELISA based on the 55 kDa antigen was generally more sensitive. The infectivity titer of SAR-55 was 10(6) cynomolgus 50% infectious doses per gram of feces. The infectivity titer corresponded to the HEV genome titer of the inoculum as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Anti-HEV IgM was detected in only a portion of the animals that had an anti-HEV IgG response. Biochemical evidence of hepatitis was most prominent in animals that were inoculated with the higher concentrations of virus and the incubation period to seroconversion was prolonged in animals that received the lower doses.

Seroepidemiology of water-borne hepatitis in India and evidence for a third enterically-transmitted hepatitis agent

Many epidemics of water-borne hepatitis have occurred throughout India. These were thought to be epidemics of hepatitis A until 1980, when evidence for an enterically transmitted non-A, non-B hepatitis was first reported. Subsequently, hepatitis E virus was discovered and most recent epidemics of enterically transmitted non-A, non-B hepatitis have been attributed to hepatitis E virus infection. However, only a limited number of cases have been confirmed by immuno electron microscopy, polymerase chain reaction, or seroconversion. In the present study we have performed a retrospective seroepidemiologic study of 17 epidemics of water-borne hepatitis in India. We have confirmed that 16 of the 17 epidemics were caused at least in part by serologically closely related hepatitis E viruses. However, one epidemic, in the Andaman Islands, and possibly a significant minority of cases in other epidemics, appears to have been caused by a previously unrecognized hepatitis agent.

Hepatitis viruses: changing patterns of human disease

Viral hepatitis is a disease of antiquity, but evidence for more than one etiologic agent has been recognized only since the 1940s, when two viruses (hepatitis A virus and hepatitis B virus) were thought to account for all disease. In the past 20 years, three additional hepatitis agents (hepatitis C virus, hepatitis D virus, and hepatitis E virus) have been discovered, and there is evidence for at least one additional virus. Each of the five recognized hepatitis viruses belongs to a different virus family, and each has a unique epidemiology. The medical impact of these viruses on society has been strongly influenced by changes in human ecology. This has resulted in some cases in diminished disease and in others in increases in the incidence of disease.

Neutralizing antibodies against hepatitis C virus and the emergence of neutralization escape mutant viruses

We developed an in vitro assay for antibodies to hepatitis C virus (HCV) that bind to virions and prevent initiation of the replication cycle in susceptible cells in vitro. These antibodies therefore appear to be capable of neutralizing the virus. Using this assay and a standard inoculum of HCV of known infectivity, we have measured the antibody in serial serum samples obtained from the same chronically infected patient over 14 years following onset of his hepatitis. Such antibody was found in sera collected within 5 years of onset of hepatitis but not in later sera. In double immunoprecipitation experiments with anti-human immunoglobulin, the same sera that contained neutralizing antibody were found to contain antibody that bound to HCV to form antigen-antibody complexes immunoprecipitable with anti-human globulin. Similarly, plasma collected from this patient in 1990, 13 years after onset of hepatitis, and which contained HCV that had diverged genetically from the 1977 strain, did not contain antibody capable of neutralizing either the 1977 or the 1990 strain of HCV. However, plasma collected a year later (1991, 14 years after onset of hepatitis) contained neutralizing antibody to the 1990, but not the 1977, strain of HCV. These results suggest that HCV does induce antivirion antibody, as measured by blocking of initiation of the replication cycle of virus in cells and by the formation of immunoprecipitable antigen-antibody complexes but that these antibodies are isolate specific and change over time. Thus, these antivirion antibodies function as neutralizing antibodies and are probably in vitro correlates of the attempt of the host to contain the emergence of neutralization-resistant variants of HCV over time.

Hepatitis C virus in multiple episodes of acute hepatitis in polytransfused thalassaemic children

We investigated the course of distinct episodes of acute non-A, non-B (NANB) hepatitis in three polytransfused thalassaemic children. In each case, the first episode was associated with the appearance of serum hepatitis C virus (HCV) RNA and anti-HCV seroconversion. The second episode was accompanied by the reappearance of HCV viraemia, which in two patients was due to reinfection with a different HCV strain and in the third could be the result of either reactivation of primary infection or reinfection with a new but closely related strain. Thus HCV infection may not induce protective immunity, which has implications for vaccine development.

Transmission of hepatitis A to patients with hemophilia by factor VIII concentrates treated with organic solvent and detergent to inactivate viruses. The Italian Collaborative Group

OBJECTIVE

To determine whether an outbreak of hepatitis A virus (HAV) infection that occurred in 52 patients with hemophilia in Italy was acquired through infusion of contaminated factor VIII or through environmental enteric transmission.

DESIGN

A case-control study and a molecular analysis of HAV sequences from implicated lots of factor VIII and from infected patients.

PATIENTS

The first 29 patients with hemophilia and jaundice in whom hepatitis A developed were compared with one to three matched controls with hemophilia but no jaundice.

MEASUREMENTS

Type of concentrate and batches infused, number of doses, contacts with persons who had jaundice or hepatitis A, travel abroad to countries reported to have a high attack rate for hepatitis A, and consumption of raw shellfish. Hepatitis A viral sequences sought by polymerase chain reaction in lots of factor VIII and in serial serum samples from two patients with hemophilia in whom hepatitis A developed. Amplification by polymerase chain reaction of cDNA transcribed with reverse transcriptase from matched sets of factor VIII and recipient serum samples. Determination of nucleotide sequence of amplified hepatitis A virus genome.

MAIN RESULTS

Case patients were neither more nor less likely than controls to have traveled to high-risk countries, consumed raw shellfish, or had contact with persons with jaundice. Case patients were more likely than controls to have received a factor VIII concentrate treated with a solvent-detergent mixture to inactivate viruses (odds ratio, infinity; 95% CI, 4.5 to infinity) and to have had larger infusions of the concentrate during the presumed HAV incubation period (odds ratio, 8.54; CI, 2.78 to 27.5). Hepatitis A viral sequences were found in 5 of 12 tested lots of factor VIII. Genomic sequences of HAV obtained for two matched sets of factor VIII and recipient serum samples were identical within each set but different for the two sets.

CONCLUSION

Hepatitis A was transmitted by a factor VIII concentrate treated by a virucidal method (solvent-detergent) that ineffectively inactivates nonenveloped viruses.

In vivo transfection by hepatitis A virus synthetic RNA

Marmosets injected intrahepatically with nucleic acids (cDNA and RNA transcripts) representing the full-length genome of the wild-type HM-175 strain of hepatitis A virus experienced acute hepatitis and seroconversion to hepatitis A virus capsid proteins. The hepatitis was comparable in severity to that caused by infection with the wild-type virus. The viral cDNA and the hepatitis A virus recovered from the feces of an injected animal contained the same marker mutation. Therefore, intermediate cell culture steps can be omitted and the virulence of a hepatitis A virus encoded by a cDNA clone can be evaluated by direct transfection of marmosets.

Attenuated hepatitis A virus: genetic determinants of adaptation to growth in MRC-5 cells

A live candidate hepatitis A virus vaccine, developed from the HM-175 strain and adapted to growth in primary African green monkey kidney (AGMK) cells, was adapted to growth in MRC-5 cells. The nucleotide sequence of the MRC-5 cell-adapted virus was determined and compared with the known sequence of the AGMK cell-adapted virus. Thirteen unique mutations, which occurred during passage in MRC-5 cells, were identified. Four of the unique mutations were located in a cluster in the 5' noncoding region (NC), and three of the remaining nine mutations encoded amino acid changes. Infectious chimeric cDNAs were constructed from infectious cDNA clones of the AGMK cell-adapted and wild-type HM-175 viruses and PCR-amplified cDNA segments of the MRC-5 cell-adapted virus. The viruses encoded by these plasmids were recovered after transfection of cultured cells with in vitro transcripts, and their growth phenotypes in fetal rhesus kidney 4 (FRhK-4) and MRC-5 cells were determined. The important growth-enhancing mutations could be divided into three sets. Two of these were located in the 5' NC region, and the third was located in the 2C nonstructural gene. The mutations in the 5' NC region that developed during passage in MRC-5 cells were indispensable for efficient growth in MRC-5 cells, but a combination of the two groups in the 5' NC region and one in the 2C gene were required to increase growth dramatically in MRC-5 cells.

High prevalence of hepatitis C virus (HCV) RNA in dialysis patients: failure of commercially available antibody tests to identify a significant number of patients with HCV infection. Copenhagen Dialysis HCV Study Group

Results of serologic tests were correlated with hepatitis C virus (HCV) viremia, determined by a cDNA polymerase chain reaction assay to detect HCV RNA, in 340 Danish dialysis patients; of these, 28 (8.2%) were positive for antibodies to HCV (anti-HCV) with second-generation ELI-SAs. HCV RNA was found in sera from 27 of these 28 anti-HCV-positive patients. However, 8 dialysis patients had detectable levels of HCV RNA but were anti-HCV-negative with second-generation ELISAs. Among the 35 HCV-infected dialysis patients 16 were positive, 7 indeterminate, and 12 negative with the second-generation RIBA. More than 60% of patients with evidence of ongoing liver disease had HCV infection. Thus, current commercially available antibody tests did not accurately reflect the HCV status in dialysis patients. A relatively high prevalence (> 10%) of HCV RNA, closely associated with liver disease, was found among dialysis patients in a low-prevalence area of the world.

Importance of the polymerase chain reaction in the study of hepatitis C virus infection

Recently, the principal etiological agent of parenterally transmitted non-A, non-B hepatitis was molecularly cloned from the plasma of an experimentally infected chimpanzee and has been named hepatitis C virus. Determination of the complete nucleotide sequence of the hepatitis C virus genome was a crucial step in preparing the way for future study of this medically important human pathogen. Due to the very low concentration of virus in serum, amplification of viral RNA sequences by reverse transcription and polymerase chain reaction is the only practical method currently available for demonstrating viremia in patients with hepatitis C virus infection. This review examines the pivotal role of the polymerase chain reaction in understanding the biology of hepatitis C virus.

Mutant woodchuck hepatitis virus genomes from virions resemble rearranged hepadnaviral integrants in hepatocellular carcinoma

Although hepadnaviruses are implicated in the etiology of hepatocellular carcinoma, the pathogenic mechanisms involved remain uncertain. Clonally propagated integrations of hepadnaviral DNA into cellular DNA can be demonstrated in most virally induced hepatocellular carcinomas. Integration occurs at random sites in cellular DNA, but the highly preferred sites in viral DNA are adjacent to the directly repeated sequence DR1, less often DR2, or in the cohesive overlap region. Integrants invariably contain simple deletions or complex rearrangements that have been thought to occur after integration. We report here the detection of mutant woodchuck hepatitis virus (WHV) genomes cloned from virions in serum that are strikingly similar to the rearranged hepadnaviral genomes found previously as integrated sequences in cellular DNA. Of 102 cloned genomes studied, 2 had large inverted duplications, 1 a 219-nucleotide direct duplication, and 1 a 219-nucleotide deletion. Virus-virus DNA junctions occurred either adjacent to DR1 or DR2 or in the cohesive overlap region at preferred topoisomerase I cleavage sites. Since these sites are located in the single-stranded regions of the genome, cleavage by topoisomerase I would produce linear molecules that would be expected to be highly recombinogenic since this enzyme, possessing nicking and ligating activities, would remain covalently attached. Sucrose density gradient centrifugation coupled with polymerase chain reaction studies confirmed that the mutant WHV DNA forms resided in virions and did not represent free viral DNA released from infected cells or were unlikely to be an artifact of the cloning process. Thus, the finding in virions of mutant WHV DNA similar to WHV DNA integrated into cellular DNA suggests that the processes of mutation and integration are linked in some instances. Furthermore, the mutant genomes that are preferentially integrated into cellular DNA may have an etiologic role in hepatocarcinogenesis.

Partial sequence comparison of eight new Chinese strains of hepatitis E virus suggests the genome sequence is relatively stable

Partial genomic sequences representing 420 nucleotides of a nonstructional region, 480 nucleotides of the putative RNA polymerase region, and 540 nucleotides of the structural region of epidemic-associated Chinese strains of hepatitis E virus (HEV) were obtained by direct sequencing of PCR-amplified DNA. Comparison with previously published HEV sequences showed a clear relatedness of all Chinese strains to each other and to a Pakistani strain (Sar-55). All eight Chinese strains examined had very similar sequences (98.5-99.8% homology) in the regions examined and were much closer to the Pakistani strain (Sar-55) (97.9-98.4% homology) than to the Burmese strain (92.5-93.3% homology). Sequence comparisons of the three genomic regions in the Chinese strains indicated that the RNA polymerase region was much more conserved than the other nonstructural region or the structural region. HEV isolates from three remote geographic regions of China had sequences closely related to each other.