Differential roles of serum hepatitis B virus DNA and hepatitis B surface antigen level in predicting virological breakthrough in patients receiving lamivudine therapy

BACKGROUND AND AIM

The role of serum hepatitis B surface antigen (HBsAg) level in determining virological breakthrough (VB) for patients with hepatitis B virus (HBV) infection receiving lamivudine remains unclear. The study aimed to evaluate the impact of serum HBsAg levels on VB among patients receiving lamivudine therapy, especially in a setting of low HBV viral load.

METHODS

Two hundred sixty-eight consecutive treatment-naïve patients who underwent lamivudine therapy for chronic hepatitis B were enrolled. Factors in terms of VB were analyzed by multivariate analysis.

RESULTS

After a median treatment duration of 67.1 weeks, 102 patients had VB. Multivariate analysis showed that positive hepatitis B e antigen (HBeAg) (hazard ratio 2.165, P = 0.026) and HBV DNA levels ≥ 2000 IU/mL after 6 months of lamivudine therapy (hazard ratio 5.236, P = 0.001) were independent risk factors predicting VB. The cumulative VB rates stratified by HBeAg-positive and -negative at 3 years were 44.7% and 26.3%, respectively. At 3 years, the cumulative VB rates stratified by the HBV DNA < 2000 and ≥ 2000 IU/mL after 6 months of therapy were 25.5% and 79.4%, respectively. For HBeAg-positive patients with serum HBV DNA < 2000 IU/mL after 6 months of therapy, baseline HBsAg levels ≥ 20,000 IU/mL was the only risk factor associated with VB.

CONCLUSIONS

For chronic hepatitis B patients treated with lamivudine, serum HBV DNA level > 2000 IU/mL after 6 months of therapy could predict subsequent VB. In patients with lower on-treatment viral load, baseline serum HBsAg level is associated with the emergence of VB, especially for those with serum positive HBeAg.

Pro-205 of large hepatitis delta antigen and Pro-62 of major hepatitis B surface antigen influence the assembly of different genotypes of hepatitis D virus

Hepatitis B surface antigen (HBsAg) is essential for the assembly and infection of hepatitis D virus (HDV). The assembly efficiency of genotype 1 HDV is higher than that of genotype 2, whilst the P62L substitution of major HBsAg further compromises the assembly of genotype 2 and 4 HDV. This study investigated the influence of proline residues in the carboxyl end of the large hepatitis delta antigen (HDAg-L) on the assembly of HDV of different genotypes. Expression vectors containing the HDAg-L gene or full-length HDV genome of genotype 1, 2 or 4 were co-transfected with plasmids expressing HBsAg proteins that bore either proline or leucine residues at position 62. Of the eight HDV genotypes, only genotype 1 has Pro-205 in HDAg-L, whereas genotypes 2 and 4 have Arg-205. The Arg-205 to Pro-205 substitution in HDV-2 and -4 markedly increased the assembly efficiencies of HDAg-L and whole HDV genomes, even in the presence of HBsAg with Leu-62. In contrast, secretion of genotype 1 HDV or HDAg-L was reduced significantly when arginine or alanine replaced Pro-205. When HBsAg contained Pro-62, the influence of Pro-205 on assembly decreased. In conclusion, both Pro-205 of the HDAg-L and Pro-62 of the major HBsAg play critical roles in the assembly of HDV of different genotypes. The presence of Pro-205 in genotype 1 HDV may account for its higher assembly efficiencies and wider distribution.

Risk factors for early and late recurrence in hepatitis B-related hepatocellular carcinoma

BACKGROUND/AIMS

Hepatitis B virus (HBV) levels correlate with the development of hepatocellular carcinoma (HCC), but the role of viral load in HCC recurrence after tumor resection remains unclear. Herein we aimed to investigate the role of viral load in HCC recurrence following tumor resection.

METHODS

From 1990 to 2002, 193 HBV-related HCC patients who underwent tumor resection in Taipei Veterans General Hospital were enrolled. Serum HBV DNA level and mutations were analyzed for association with early and late recurrence, together with other clinical variables.

RESULTS

During a follow-up of 58.2+/-44 months, 134 patients had HCC recurrence. Multivariate analysis showed that multinodularity (Hazard ratio [HR], 95% confidence interval [CI]; 2.232, 1.021-4.878), macroscopic venous invasion (4.693, 1.645-13.391), AFP >20 ng/ml (3.891, 1.795-8.475), and cut margin <or= 1cm (3.333, 1.487-7.470) were correlated with early recurrence (within two years of operation) of HCC. In addition, multivariate analysis determined that Ishak hepatic inflammatory activity >6 (4.658, 1.970-11.017), multinodularity (3.266, 1.417-7.526), ICG-15 >10% (2.487, 1.095-5.650) and HBV DNA level >10(6) copies/ml (2.548, 1.040-6.240) were significantly associated with late recurrence (>two years after resection). Patients with high viral loads tended to have higher Ishak inflammatory (7.00+/-3.07 vs. 5.33+/-2.96, p=0.001) and fibrosis scores (4.17+/-2.01 vs. 3.20+/-2.41, p=0.007) than those with lower loads.

CONCLUSIONS

Tumor factors were associated with early HCC recurrence while high viral loads and hepatic inflammatory activity were associated with late recurrence. Pre- and post-operative antiviral and anti-inflammatory therapies may be crucial in reducing late recurrence.

Positive selection of hepatitis delta antigen in chronic hepatitis D patients

Liver disease may become ameliorated in some patients with chronic hepatitis D virus (HDV) infection. We present here a study based on longitudinal sampling to investigate the viral dynamics in chronic HDV infection. We examined the HDV variants from different time points, especially those before and after the elevation of serum aminotransferase levels. The datasets from each patient were tested for positive selection by using maximum-likelihood methods with heterogeneous selective pressures along the nucleotide sequence. An average of 4.9%, ranging from 3.1 to 6.8%, of the entire delta antigen sites was regulated by a diversifying selection. Most of the positively selected sites were associated with immunogenic domains. Likelihood ratio tests revealed a significant fitness of positive selection over neutrality of the hepatitis delta antigen gene in all patients. We further adapted a neural network method to predict potential cytotoxic T ligand epitopes. Among the HLA-A*0201 cytotoxic T ligand epitopes, three consistent epitopes across all three genotypes were identified: amino acids (aa) 43 to 51, 50 to 58, and 114 to 122. Three patients (60%) had sites evolving under positive selection in the epitope from aa 43 to 51, and four patients (80%) had sites evolving under positive selection in the epitope from aa 114 to 122. The discovery of immunogenic epitopes, especially cytotoxic-T-lymphocyte ligands, associated with chronic HDV infection may be crucial for further development of novel treatments or designs in vaccine for HDV superinfection.

Genotypes and viremia of hepatitis B and D viruses are associated with outcomes of chronic hepatitis D patients

BACKGROUND & AIMS

Genotypes and viremia of hepatitis D virus (HDV) and hepatitis B virus (HBV) may be associated with outcomes. This study evaluated the impact of viral genotypes and viremia on outcomes of dual HBV and HDV infection.

METHODS

Viremia and viral genotypes were analyzed in 194 consecutive chronic hepatitis B patients with HDV superinfection and correlated with outcomes.

RESULTS

The numbers of HBV genotype A, B, C, and nonclassified were 4, 57, 23, and 110, respectively. There were 51 genotype I HDV, 74 genotype II HDV, 8 genotype IV HDV, and 61 nonclassified HDV genotype. In a median follow-up of 135 months, 24 progressed to cirrhosis and 41 developed hepatocellular carcinoma. Patients infected with genotype I HDV had a lower remission rate (15.2% vs 40.2%; P = .007) and more adverse outcomes (cirrhosis, hepatocellular carcinoma, or mortality) (52.2% vs 25.0%; P= .005) than those with genotype II HDV. Patients infected with genotype C HBV had a lower remission rate (0 vs 32.1%; P = .005) and more adverse outcomes (70.0% vs 33.9%; P = .005) than those with genotype B HBV. The presence of HBV or HDV viremia was associated with lower remission rates compared with those negative for both (26.4% and 24.3% vs 69.2%; P < .001). In multivariate analysis, age, genotype C HBV, and genotype I HDV were independent factors associated with adverse outcomes.

CONCLUSIONS

In chronic HBV and HDV dual infections, older age, genotype I HDV, and genotype C HBV correlated with adverse outcomes.

“Defective” mutations of hepatitis D viruses in chronic hepatitis D patients

AIM: To verify whether “defective” mutations existed in hepatitis D virus (HDV).

METHODS: Hepatitis delta antigen (HDAg)-coding sequences were amplified using Pfu DNA polymerases with proof-reading activities from sera of five patients with chronic hepatitis D. Multiple colonies were sequenced for each patient. Pfu analyzed a total of 270 HDV clones. Three representative defective HDV clones were constructed in expression plasmids and transfected into a human hepatoma cell line. Cellular proteins were extracted and analyzed by Western blot.

RESULTS: Four of five cases (80%) showed defective HDV genomes in their sera. The percentage of defective genomes was 3.7% (10/270). The majority (90%) of the defective mutations were insertions or deletions that resulted in frameshift and abnormal stop translation of the HDAg. The predicted mutated HDAg ranged from 45 amino acids to >214 amino acids in length. Various domains of HDAg associated with viral replication or packaging were affected in different HDV isolates. Western blot analysis showed defected HDAg in predicted positions.

CONCLUSION: “Defective” viruses do exist in chronic HDV infected patients, but represented as minor strains. The clinical significance of the “defected” HDV needs further study to evaluate.

Interaction and replication activation of genotype I and II hepatitis delta antigens

The nucleotide sequences of hepatitis D viruses (HDV) vary 5 to 14% among isolates of the same genotype and 23 to 34% among different genotypes. The only viral-genome-encoded antigen, hepatitis delta antigen (HDAg), has two forms that differ in size. The small HDAg (HDAg-S) trans-activates viral replication, while the large form (HDAg-L) is essential for viral assembly. Previously, it has been shown that the packaging efficiency of HDAg-L is higher for genotype I than for genotype II. In this study, the question of whether other functional properties of the HDAgs are affected by genotype differences is addressed. By coexpression of the two antigens in HuH-7 cells followed by specific antibody precipitation, it was found that HDAgs of different origins interacted without genotypic discrimination. Moreover, in the presence of hepatitis B virus surface antigen, HDAg-S was incorporated into virion-like particles through interaction with HDAg-L without genotype restriction. As to the differences in replication activation of genotype I HDV RNA, all HDAg-S clones tested had some trans-activation activity, and this activity varied greatly among isolates. As to the support of HDV genotype II replication, only clones of HDAg-S from genotype II showed trans-activation activity, and this activity also varied among isolates. In conclusion, genotype has no effect on HDAg interaction and genotype per se only partly predicts how much the HDAg-S of an HDV isolate affects the replication of a second HDV isolate.

Spread of hepatitis E virus among different-aged pigs: two-year survey in Taiwan

Swine are reservoirs of hepatitis E virus (HEV). In this study, a 2-year survey of HEV in feces and sera of swine was conducted to determine if: 1) HEV has circulated among pigs for some time in Taiwan; 2) the spread of HEV among different-aged pigs; and 3) there exists HEV strains possibly imported through trading. From 1998-2000, 521 serum samples and 54 fecal specimens from pigs were examined by reverse transcription polymerase chain reaction. None of the 11 pigs in suckling stage (< 2 months) were serum HEV RNA positive. The highest viremia rate (4.5%) was in pigs of 2 months age, followed by 1.2% and 1.8% in pigs of growing (3-4 months) and finishing stages (5-6 months), and none in pigs older than 6 months. Viremia showed little variation in different years and areas. None of the 20 fecal samples from pigs in suckling stage were HEV RNA positive, whereas 9% of the 34 samples from pigs in growing or finishing stages were positive. Most swine HEV isolates in Taiwan clustered within the genotype 4, whereas the three HEV isolates cloned from pigs imported recently from the U.S. belonged to the genotype 3 HEV in the U.S. The results suggest that HEV may infect pigs at an early growing stage and spread unnoticed among pigs and possibly across countries through trading.

Varied assembly and RNA editing efficiencies between genotypes I and II hepatitis D virus and their implications

The mechanisms that link genotypes of hepatitis D virus (HDV) with clinical outcomes have not yet been elucidated. Genotypic variations are unevenly distributed along the sequences of hepatitis delta antigens (HDAgs). Of these variations, the packaging signal at the C-terminus has a divergence of 74% between genotypes I and II. In this report, we address the issue of whether these high variations between genotypes affect assembly efficiency of HDV particles and editing efficiency of RNA. Viral package systems of transfection with expression plasmids of hepatitis B surface antigen and HDAgs or whole genomes of HDV consistently indicate that the package efficiency of genotype I HDV is higher than that of genotype II. Segment swapping of large-form HDAg indicates that the C-terminal 19-residue region plays a key role for the varied assembly efficiencies. Also, the editing efficiency of genotype I HDV is higher than that of genotype II. The nucleotide and structural changes surrounding the editing site may explain why genotype II HDV has a low RNA editing efficiency. The findings of in vitro assembly systems were further supported by the observations that patients infected with genotype II had significantly lower alanine transaminase (ALT) levels, more favorable outcomes (P <.05), and a trend to have lower serum HDV RNA levels as compared with those infected with genotype I HDV (P =.094). In conclusion, genotype II HDV secretes fewer viral particles than genotype I HDV does, which in turn may reduce the extent of infection of hepatocytes and result in less severe hepatic inflammation.

Characterization of a strain-specific monoclonal antibody to hepatitis delta virus antigen

Sequences of the hepatitis delta virus (HDV) vary to different degrees among isolates. A monoclonal antibody, designated as HP6A1, against the antigen of HDV (HDAg) has been characterized for its specificity. HP6A1 bound to HDAg of isolate 25 (genotype I) that was used for immunization, but not to others of both genotypes I and II. The epitope recognized by HP6A1 was then determined by a phage library displaying various heptapeptides. A consensus peptide deduced has the best match with that of residues 4-10 of HDAg (isolate 25). To confirm the phage mapping result, Escherichia coli recombinant proteins containing different lengths and various segments of HDAg (isolate 25) were constructed. The shortest HDAg segment contained in the fusion protein that reacted with HP6A1 was residues 1-10. When this peptide was added to the N-terminus of a heterologous protein engineered for eucaryotic expression, the fusion protein was detected by HP6A1. It is concluded that HP6A1 recognizes an epitope located at the N-terminus of HDAg (isolate 25). Since viruses of quasi-species exist in natural infections, a question of how different viral strains interact in vivo remains to be explored. The highly specific MAb opens a possibility to examine the fate of one strain in the presence of other related species in a cell transfection system.

Clinical and epidemiological implications of swine hepatitis E virus infection

In nonendemic areas, most patients with acute hepatitis E were infected through traveling to endemic areas. However, some patients did not have a history of foreign travel before infection. Furthermore, high seroprevalence rates of antibody to hepatitis E virus (anti-HEV) were found in the general adult population in some countries without any recorded outbreak of hepatitis E. The significance of anti-HEV assay in these subjects remains obscure. To study if swine might be a source of HEV infection, HEV was tested in sera of 235 pigs in Taiwan, and from 5 patients with acute HEV infection who either denied or did not provide any foreign travel history. Three (1.3%) pigs had detectable swine HEV RNA. The swine and human HEV strains from Taiwan formed a monophyletic group, distinct from three previously reported groups: the United States human and swine HEV strains, the Mexico strain, and the largest group composed of the Asian and the African strains. The identity of nucleotide sequences was 84-95% between swine and human HEV strains in Taiwan, and 72-79% between Taiwan strains and those from different areas. The predicted amino acid sequence of a Taiwan swine HEV strain within the peptide 3-2 used in commercial anti-HEV assay showed a high identity (91-94%) with those of other human and swine HEV strains. Swine may be a reservoir of HEV and subclinical swine HEV infection may occur. Cross-reactivity of current anti-HEV assay may account for the high prevalence rate of anti-HEV in the general population in nonendemic areas.

Recombination of hepatitis D virus RNA sequences and its implications

Recombination between RNA sequences plays a role in the fast evolution of a few viruses. There has been no report on hepatitis D virus (HDV) recombination. In this study, we analyzed genetic recombination of HDV and its possible impact on evolution and clinical course. The aligned HDV sequences allowed us to construct a phylogenetic tree which supported the notion of distinct lineages of HDV. The tree was also used in the analysis of recombination using partial likelihoods assessed through optimization. Nine segments of the HDV genome with significant levels of genetic recombination were detected. Five segments were in the hypervariable region, and four were in the delta-antigen- coding region. None could be found in the well-conserved autocleavage region that is essential for replication. Recombination occurred both between and within types. The results of this study indicated that the remarkable variation in HDV genomic sequences, particularly in the hypervariable region, among different genotypes may at least partly result from multiple episodes of genetic recombination during evolution. Genetic recombination may play a significant role in increasing genetic diversity. Importantly, a genetic recombination (nt 1082-1093) occurred in one of the immunogenic domains of hepatitis delta virus antigen recognized by human and woodchuck antibodies (amino acids 174-195). Genetic recombination also occurred at another segment between nt 1517 and 1535, which was close to one of the predicted T-cell epitopes (amino acids 26-41). In longitudinal analysis of HDV genomes at different time points during chronic infection, novel dominant HDV strains with amino acid changes at these epitopes usually emerged after severe hepatitis attacks. In the comparison of HDV clones during or shortly after flare-up of liver disease, Ka/Ks ratios of > 1 were frequently found, suggesting Darwinian positive selection. Therefore, recombination in these two segments may play an important role for HDV in the evasion of immunity.

Localization of isoprenylated antigen of hepatitis delta virus by anti-farnesyl antibodies

Hepatitis delta virus (HDV) is a subviral pathogen that requires pre-existing or concurrent infection with hepatitis B virus (HBV). HDV expresses two forms of a single protein, the delta antigen (HDAg), which are identical except for an additional 19 residues at the C terminus of the large form. Within this C-terminal extension a cysteine residue is isoprenylated; this isoprenylation is critical for interaction with HBV envelope proteins to enable virus assembly and release into the medium. Therefore, large HDAg must be recruited to an extracellular compartment. However, immuno-staining with HDAg-specific antibodies has localized the large antigen mainly to the nucleus and supports the notion that large HDAg suppresses virus replication in the nucleus. Since isoprenylation would increase the hydrophobicity of the protein and may favour transport towards specific membranes, the question remains whether the large HDAg detected in the nucleus carries an isoprenyl group. To address this issue, antibodies against the farnesyl modification were generated to allow direct visualization of the antigen by immunofluorescence microscopy. The anti-farnesyl antibodies specifically stained large HDAg expressed in Huh-7 cells, and the signal was largely restricted to the nucleus; the staining pattern could be superimposed on those of cells stained for large HDAg. The large HDAg translocated into the nucleus was therefore isoprenylated. In addition, antibodies specific for the farnesyl modification should be applicable to the study of other similarly isoprenylated proteins.

Mixed genotypes infection with hepatitis D virus

Heterogeneity of hepatitis C viral (HCV) genomes results in escape from immune clearance. Super-infection or mixed infection of different genotypes of HCV are seen commonly in humans. Hepatitis D virus (HDV) is classified into 3 genotypes. This study was planned to investigate if mixed genotypes infection of HDV occurs in humans. HDV genotyping based on restriction fragment length polymorphism (RFLP) was used to screen 60-99 HDV clones from each case of 7 prostitutes and 11 patients. Mixed infections were diagnosed by the finding of two or more different RFLP patterns in a case and were confirmed by sequencing. Five prostitutes had mixed infections of genotypes IIa and IIb HDV, while only 2 patients had mixed infections of genotypes I and II HDV (P< 0.05). The heterogeneity in nucleotide sequence was generally below 2% among HDV quasi-species from the same subject, while the heterogeneity was 27.7% between genotypes I and II HDV, and 22.8% between genotypes IIa and IIb HDV from a subject with mixed infection. Multiple HDV clones from the spouses of the 2 index cases were also analyzed. One spouse had mixed infection and the other did not, corresponding to the index cases. In cases with mixed genotypes infections, the prevalence of the minor strain was less than 10% of the total colony population analyzed.

Evidence of transmission of hepatitis B virus to spouses from sequence analysis of the viral genome

Heterosexual contact is one of the common routes of transmission for hepatitis B virus (HBV) among adults in Taiwan, but only a few studies have provided direct evidence at the level of the HBV genome of infected couples with acute non-fulminant hepatitis to document a common source. By cloning and sequencing polymerase chain reaction-amplified HBV-DNA, we analysed the sequences of the conserved region of the surface gene (nucleotide (n.t.) 305-513, representing 6.5% of the viral genome) of HBV in five HBV-infected index patients, their spouses and four randomly selected HBV carriers as controls. Risk factors associated with acute HBV infection in index cases were sexual contact with their spouses within 3 months before the onset of hepatitis. For all five couples, the HBV-infected index patient and the spouse shared a 100% sequence homology of HBV-DNA. In contrast, there was significantly more variation (mean heterogeneity 6.1%, range 1-13.9%) in the amplified region between the five couples and between each couple and the controls (P<0.001). This study demonstrated that sequence analyses can correlate well with epidemiological findings and confirm the value of the molecular approach for linked infections of HBV through heterosexual contact between spouses. Susceptible adults should receive vaccination.

Characterization and phylogenetic analysis of a novel hepatitis D virus strain discovered by restriction fragment length polymorphism analysis

The hepatitis D virus (HDV) genotypes in 46 HDV-infected patients and 12 prostitutes were screened with Xhol restriction fragment length polymorphism (RFLP) analysis of reverse transcription PCR products of viral genomes and verified by phylogenetic analysis. The amplificates of three (6.5%) patients and two (17%) prostitutes showed a novel RFLP pattern different from those of the three known genotypes. Complete HDV genomic sequence identities between isolates with a novel RFLP and the HDV genotypes I, II and III were 72.3, 77.2 and 63.0%, respectively. Importantly, divergence was mostly seen in various regions related to replication or packaging. The novel isolates formed a monophyletic group (P < 0.05) and were most closely related to genotype II.

The impact of traveling to endemic areas on the spread of hepatitis E virus infection: epidemiological and molecular analyses

Traveling to endemic areas carries a risk of hepatitis E virus (HEV) infection, but no molecular analysis to document sources of infection is available. Eighteen (38%) of 47 patients with acute non-A, non-B, non-C hepatitis were positive for antibody to HEV (anti-HEV), and 9 (50%) of these were also positive for serum HEV RNA by polymerase chain reaction following reverse transcription. Only 1 (5%) of the 21 patients with acute hepatitis A was positive for HEV RNA. Travel to endemic areas (mostly to China; odds ratio, 22.2; 95% confidence interval, 4.7-105.8) and deeper jaundice (odds ratio, 5.2; 95% confidence interval, 1.01-27.2) were the only factors associated with HEV infection in multivariate analysis. The two HEV isolates from two patients who had traveled to China and the HEV isolate from a patient whose travel history was obscure formed a monophyletic group with the isolates from Guangzhou. The HEV isolates from our patients show a homology of 72% to 78% in nucleotide sequence with the Burma, Beijing, India, Pakistan, and Xiangjiang strains; a homology of 81% to 91% with the Guangzhou strains; and a homology of 76% with the Mexico strain. The close relationship between the Taiwan isolates and the Guangzhou strains was further supported by the short Kimura's two-parameter distances among them. In summary, HEV infection does occur in this area. Epidemiological and molecular analyses strongly indicate that most cases of HEV infection originated from travel to HEV-endemic areas.

Polymerase chain reaction analysis for viral nucleic acids in acute sporadic hepatitis patients negative for serum hepatitis B surface antigen and antibodies to hepatitis C virus

BACKGROUND

Polymerase chain reaction (PCR) is both very sensitive and very valuable in the clarification of the pathogenesis of viral hepatitis from type A to E (HAV to HEV).

METHODS

This study was aimed to detect viral nucleic acids with PCR in 33 consecutive, acute sporadic hepatitis patients who were seronegative for hepatitis B surface antigen and antibody to hepatitis C virus by conventional radioimmununoassay or enzyme-linked immunoassay.

RESULTS

Of the totals, 10 (30.3%) had detectable viral genomes. HBV DNA and HCV RNA were each detected in 2 (7.4%) of 27 patients with a self-limiting course. By contrast, HBV DNA was detected in the two (33.3%, p = 0.14) and HCV RNA in the three (50%, p = 0.03) of the six patents who became chronic; another one who had subsequent multiple exacerbations of hepatitis was positive for both HBV DNA and HCV RNA. HDV RNA was not detectable in all subjects. Although four (12.1%) were positive for antibody against HEV, none had detectable HEV RNA. Spontaneous disease resolution predominantly occurred in patients without detectable hepatitis B and hepatitis C genomes (100% of 23 patients vs 40% of 10 patients, p < 0.01).

CONCLUSIONS

These results demonstrate that a combination of serological and molecular tests is mandatory for the appraisal of acute sporadic non-B non-C hepatitis and its clinical prognosis, they also raise the possibility of a hepatotrophic agent other than HAV to HEV. Recent documentation of the new GBV-C (hepatitis G virus) suggests the necessity of studying the unidentified pathogenesis in patients with non-A to E hepatitis.

Evidence of transmission of hepatitis D virus to spouses from sequence analysis of the viral genome

To study sexual transmission of hepatitis D virus (HDV), 52 spouses of 56 index patients were observed and HDV genomes from antibody to HDV (anti-HDV)-positive couples were sequenced. Of the spouses, 11 (21%) were serum HBsAg positive, 3 (27%) of whom were also anti-HDV positive. The HDV sequences between spouses were found to be nearly identical (98% to 98.8%) in the region analyzed (nt 911 to nt 1260). Only one couple showed an identity > 90% with the genotype I HDV strains. The HDV sequences of the remaining two couples showed > 95% identity with each other and > 91% homology with genotype II, but they shared only a 73.1% to 73.7% homology with those of the first couple. The regions corresponding to the autocatalytic cleavage sites, the junction between the middle and the carboxyl terminal one-third domains, and the middle domain of the open reading frame for delta antigen on the antigenomic HDV RNA were more conserved with < 19% divergence among the three couples. Interestingly, there was a 56% divergence in the region corresponding to the carboxyl end of the open reading frame for the large delta antigen on the antigenomic HDV RNA. In summary, this study provides a direct nucleotide evidence of a common source of HDV infection in each couple. Despite divergence in the viral nucleotide sequence, both genotypes I and II were found in Taiwan and were transmitted from patients with a history of prostitute contact to spouses through sexual contact.

Expression and localization of the small and large delta antigens during the replication cycle of hepatitis D virus

To study the expression and localization of delta antigen during the replication cycle of hepatitis D virus, we cotransfected HuH-7 hepatoma cells with a hepatitis B virus expression plasmid and plasmids expressing the small or large delta antigen or the entire HDV genome. The transfected cells and culture medium were analyzed on double immunofluorescence staining for delta antigen and HBsAg, on Western blotting and on Northern-blot hybridization from 4 hr to 9 days after transfection. In cells transfected with the expression plasmid carrying the small delta antigen open reading frame, only the small delta antigen was expressed; it was localized in the nucleolus and was not released into the medium during the culture period. In cells transfected with the large delta antigen expression plasmid, the large delta antigen expressed was localized in the nucleolus at the initial stage; this was followed by relocalization in nucleoplasm. Finally, large delta antigen was released in HBsAg-enveloped particles within 1 day of transfection. In cells cotransfected with hepatitis B virus and hepatitis D virus expression plasmids, the small delta antigen was expressed 4 hr after transfection, whereas the large form was expressed 3 days after transfection. Expression of the large delta antigen coincided with the localization changes from nucleolar to mixed stage and, finally, to nucleoplasm and release of the hepatitis D virus particles. The large delta antigen appears to play a key role in relocalization of the delta antigen and packaging of the hepatitis D virus virions.(ABSTRACT TRUNCATED AT 250 WORDS)