Persistence of the hepatitis B virus covalently closed circular DNA in HepaRG human hepatocyte-like cells

The recently described hepatic cell line HepaRG is the sole hepatoma cell line susceptible to hepatitis B virus (HBV) infection. It provides a unique tool for investigating some unresolved issues of the virus' biology, particularly the formation of the viral mini-chromosome believed to be responsible for the persistence of infection. In this study, we characterized the main features of HBV infection: it is restricted to a subpopulation of differentiated hepatocyte-like cells that express albumin as a functional marker and represents around 10 % of all differentiated HepaRG cells. Infection may persist for more than 100 days in cells maintained at the differentiated state. Even though infected cells continued to produce infectious viral particles, very limited or no spreading of infection was observed. Low genetic variation was also observed in the viral DNA from viruses found in the supernatant of infected cells, although this cannot explain the lack of reinfection. HBV infection of HepaRG cells appears to be a very slow process: viral replication starts at around day 8 post-infection and reaches a maximum at day 13. Analysis of viral DNA showed slow and inefficient conversion of the input relaxed circular DNA into covalently closed circular (CCC) DNA, but no further amplification. Continuous lamivudine treatment inhibited viral replication, but neither prevented viral infection nor initial formation of CCC DNA. In conclusion, HBV infection in differentiated HepaRG cells is characterized by long-term persistence without a key feature of hepadnaviruses, the so-called 'CCC DNA amplification' described in the duck hepatitis B model.

Initiation of hepatitis B virus genome replication and production of infectious virus following delivery in HepG2 cells by novel recombinant baculovirus vector

One of the major problems in gaining further insight into hepatitis B virus (HBV)/host-cell interactions is to improve the existing cellular models for the study of HBV replication. The first objective of this study was to improve the system based on transduction of HepG2 cells with a recombinant baculovirus to study HBV replication. A new HBV recombinant baculovirus, Bac-HBV-1.1, in which the synthesis of pre-genomic RNA is driven by a strong mammalian promoter, was generated. Transduction with this new recombinant baculovirus led to higher levels of HBV replication in HepG2 cells compared with levels obtained with previously described baculovirus vectors. The initiation of a complete HBV DNA replication cycle in Bac-HBV-1.1-transduced HepG2 cells was shown by the presence of HBV replicative intermediates, including covalently closed circular DNA (cccDNA). Only low levels of cccDNA were detected in the nucleus of infected cells. Data showed that cccDNA resulted from the recycling of newly synthesized nucleocapsids and was bound to acetylated histones in a chromatin-like structure. HBV particles released into the supernatant of transduced HepG2 cells were infectious in differentiated HepaRG cells. Several Bac-HBV-1.1 baculoviruses containing HBV strains carrying mutations conferring resistance to lamivudine and/or adefovir were constructed. Phenotypic analysis of these mutants confirmed the results obtained with the transfection procedures. In conclusion, an improved cell-culture system was established for the transduction of replication-competent HBV genomes. This will be useful for future studies of the fitness of HBV mutants.

Identification of antigenic regions of duck hepatitis B virus core protein with antibodies elicited by DNA immunization and chronic infection

The induction of humoral response in ducks by DNA-based immunization against duck hepatitis B virus (DHBV) core protein (DHBc) was investigated. In addition, the amino acid specificity of the induced response was compared by using peptide scanning to that elicited either by protein immunization or during chronic DHBV infection. Immunization of ducks with a plasmid expressing DHBc protein led to the induction of a long-lasting antibody response able to specifically recognize viral protein in chronically infected duck livers. Peptide scanning analysis of anti-DHBc response induced during chronic DHBV infection allowed us to identify six major antigenic regions (AR1 to AR6). The reactivity spectrum of duck sera elicited by protein immunization appeared narrower and was restricted to only four of these antigenic regions in spite of higher anti-DHBc antibody titers. Interestingly, anti-DHBc antibodies induced by DNA-based immunization recognized five of six antigenic regions, and the epitope pattern was broader and more closely related to that observed in chronic viral infections. To gain more insight into the location of antigenic regions, we built a three-dimensional (3-D) model of DHBc protein based on human and duck core sequence alignment data and the HBc 3-D crystal structure. The results suggest that two identified antigenic regions (AR2, amino acids [aa] (64)T-P(84), and AR5, aa (183)A-R(210)) are located at positions on the protein surface equivalent to those of the two HBc major epitopes. Moreover, we identified another antigenic region (AR3, aa (99)I-I(112)) that was recognized by all sera from chronically infected, DNA- or protein-immunized ducks within the large 45-aa insertion in DHBc protein, suggesting that this region, which lacks HBc, is externally exposed.

Initial amplification of duck hepatitis B virus covalently closed circular DNA after in vitro infection of embryonic duck hepatocytes is increased by cell cycle progression

The relationship between the cell cycle and early amplification of duck hepatitis B virus covalently closed circular (CCC) DNA was studied after in vitro infection of fetal hepatocytes. We first showed that embryonic hepatocytes proliferated for at least 6 days after plating and that complete viral replication including CCC DNA amplification occurred in these proliferating cells. Addition of sodium butyrate or aphidicolin reversibly blocked cells in the G1 phase and diminished CCC DNA synthesis, which was restored after drug withdrawal, concomitantly with the entry of cells into S phase. Cell cycle progression of fetal hepatocytes can be triggered by stimulation with epidermal growth factor (EGF), hepatocyte growth factor (HGF), and tumor growth factor alpha (TGF-alpha). CCC DNA synthesis increased with progression to the S phase induced by EGF, HGF, and TGF-alpha alone or in combination. By contrast, tumor growth factor beta (TGF-beta) alone or in combination with EGF inhibited cell proliferation and viral DNA synthesis. By double labeling, viral nucleocapsids were found predominantly in bromodeoxyuridine-positive hepatocytes, indicating that high viral replication occurs preferentially in proliferating hepatocytes. CCC DNA was also detected mainly in cells in the S and G2/M phases separated from cells in the G1 phase by cell sorting. Taken together, these results show that hepatocyte proliferation may positively regulate the initial amplification of CCC DNA of avian hepadnaviruses, and may explain why mitosis is not necessarily associated with loss of CCC DNA.

Antiviral activity of beta-L-2',3'-dideoxy-2',3'-didehydro-5-fluorocytidine in woodchucks chronically infected with woodchuck hepatitis virus

The L-nucleoside analog beta-L-2',3'-dideoxy-2',3'-didehydro-5-fluorocytidine (beta-L-Fd4C) was first shown to exhibit potent activity against hepatitis B virus (HBV) in tissue culture and then to significantly inhibit viral spread during acute infection in the duck HBV model (F. Le Guerhier et al., Antimicrob. Agents Chemother. 44:111-122, 2000). We have therefore examined its antiviral activity in a mammalian model of chronic HBV infection, the woodchuck chronically infected with woodchuck hepatitis virus (WHV). Side-by-side comparison of beta-L-Fd4C and lamivudine administered intraperitoneally during short-term and long-term protocols demonstrated a more profound inhibition of viremia in beta-L-Fd4C-treated groups. Moreover, beta-L-Fd4C induced a marked inhibition of intrahepatic viral DNA synthesis compared with that induced by lamivudine. Nevertheless, covalently closed circular (CCC) DNA persistence explained the lack of clearance of infected hepatocytes expressing viral antigens and the relapse of WHV replication after drug withdrawal. Liver histology showed a decrease in the inflammatory activity of chronic hepatitis in woodchucks receiving beta-L-Fd4C. An electron microscopy study showed the absence of ultrastructural changes of hepatic mitochondria, biliary canaliculi, and bile ducts. However, a loss of weight was observed in all animals, whatever the treatment, as was a transient skin pigmentation in all woodchucks during beta-L-Fd4C treatment. There was no evidence that lamivudine or beta-L-Fd4C could prevent the development of hepatocellular carcinoma with the protocols used. These results indicate that beta-L-Fd4C exhibits a more potent antiviral effect than lamivudine in the WHV model but was not able to eradicate CCC DNA and infected cells from the liver at the dosage and with the protocol used.

Evolution of hepatitis B virus polymerase gene sequence during famciclovir therapy for chronic hepatitis B

Prolonged administration of nucleoside analogues for chronic hepatitis B may result in the emergence of hepatitis B viral polymerase mutants. To gain insight into the mechanism involved in the virus's resistance to famciclovir, the amino acid sequences of the terminal protein and reverse-transcriptase (RT) domains of the viral polymerase were determined during therapy among 28 patients. The antiviral response was independent of viral genotypes, and nonresponse to famciclovir was associated with a complex variability of the RT domain. No mutation in the YMDD motif was observed, whereas an L528M mutation was clearly selected by famciclovir treatment in 2 patients, as well as 14 novel mutations in 7 patients. Clone sequence analysis of the RT domains of patients undergoing retreatment with famciclovir and/or lamivudine showed the selection of a preexisting drug-resistant mutant in one case and indicated that sequential antiviral therapy may allow the rapid selection of resistant strains.

Design and evaluation of hepatitis B virus inhibitors

Antiviral therapy of chronic hepatitis B remains a major clinical problem worldwide. The design of new nucleoside analogs that inhibit hepatitis B virus (HBV) replication allowed their evaluation in in vitro and in vivo experimental models of HBV infection. This research has led to the discovery of the anti-HBV activity of lamivudine and its approval for the therapy of chronic hepatitis B. However, due to the development of viral resistance, strategies based on the combination of new inhibitors of HBV replication with immune modulatory approaches are urgently required.

Characterization of the antiviral effect of 2',3'-dideoxy-2', 3'-didehydro-beta-L-5-fluorocytidine in the duck hepatitis B virus infection model

A novel L-nucleoside analog of deoxycytidine, 2',3'-dideoxy-2', 3'-didehydro-beta-L-5-fluorocytidine (beta-L-Fd4C), was recently shown to strongly inhibit hepatitis B virus (HBV) replication in the 2.2.15 cell line. Therefore, its antiviral activity was evaluated in the duck HBV (DHBV) infection model. Using a cell-free system for the expression of the DHBV polymerase, beta-L-Fd4C-TP exhibited a concentration-dependent inhibition of dCTP incorporation into viral minus-strand DNA with a 50% inhibitory concentration of 0.2 microM which was lower than that of other tested deoxycytidine analogs, i.e. , lamivudine-TP, ddC-TP, and beta-L-FddC-TP. Further analysis showed that beta-L-Fd4C-TP is likely to be a competitive inhibitor of dCTP incorporation and to cause premature DNA chain termination. In primary duck hepatocyte cultures infected in vitro, beta-L-Fd4C administration exhibited a long-lasting inhibitory effect on viral DNA synthesis but could not clear viral covalently closed circular DNA (CCC DNA). Results of short-term antiviral treatment in experimentally infected ducklings showed that beta-L-Fd4C exhibited the most potent antiviral effect, followed by beta-L-FddC, lamivudine, and ddC. Longer administration of beta-L-Fd4C induced a sustained suppression of viremia (>95% of controls) and of viral DNA synthesis within the liver. However, the persistence of trace amounts of viral CCC DNA detected only by PCR was associated with a recurrence of viral replication after drug withdrawal. In parallel, beta-L-Fd4C treatment suppressed viral antigen expression within the liver and decreased intrahepatic inflammation and was not associated with any sign of toxicity. Our data, therefore, demonstrate that in the duck model of HBV infection, beta-L-Fd4C is a potent inhibitor of DHBV reverse transcriptase activity in vitro and suppresses viral replication in the liver in vivo.

The SATE pronucleotide approach applied to acyclovir: part II. Effects of bis(SATE)phosphotriester derivatives of acyclovir on duck hepatitis B virus replication in vitro and in vivo

The in vitro and in vivo antiviral activities of two mononucleoside phosphotriester derivatives of acyclovir (ACV) incorporating S-acyl-2-thioethyl (SATE) groups are reported using the duck model of hepatitis B (DHBV). In primary duck hepatocyte cultures, the described phosphotriesters significantly inhibited the replication of DHBV at submicromolar concentrations. They were found to be more potent than the parent nucleoside. This result was in agreement with our data concerning the anti-HBV activity of these pronucleotides in HepG2.2.15 cells (previous paper). In vivo, the studied SATE pronucleotide was also found to be more efficient than ACV in infected ducklings upon short-term oral therapy, while intraperitoneal treatment showed high anti-DHBV activity with both ACV and its SATE pronucleotide in this animal model. These findings demonstrate the potential of SATE pronucleotides of ACV as anti-HBV agents.

Analysis of a hepatitis delta virus isolate from the Central African Republic

Based on the analysis of HDV genomes from different areas of the world, three genotypes of HDV have been identified. Genotype I is the most prevalent and widespread. Genotype II is represented by two isolates from Japan and Taiwan. Genotype III has been found only in the Amazonian basin where it is associated with a history of severe disease, fulminant hepatitis with microvesicular steatosis (spongiocytosis). We report here the cloning and the analysis of the complete viral genome from woodchuck serum-derived HDV RNA after transmission from Central African Republic (RCA) patients with fulminant spongiocytic delta hepatitis. Two overlapping cDNA fragments, covering the entire HDV genome, were generated by RT-PCR and cloned. Three clones obtained from each fragment were fully sequenced. A complete consensus RCA HDV genome was reconstituted. The individual and the consensus nucleotide sequences were compared with those of 16 other fully sequenced isolates belonging to the three genotypes. Phylogenetic trees generated by the neighbour joining method firmly place our isolate in genotype I, and show that this RCA isolate differs significantly from the east African isolates previously analysed. Transfection experiments showed that the isolate is replication-competent, but less so than the control "wild-type" strain. Two novel mutations encountered in this work, one in the antigenomic ribozyme sequence and one affecting delta antigen, were studied.

Phosphorylation of DHBV pre-S: identification of the major site of phosphorylation and effects of mutations on the virus life cycle

Four potential serine/threonine phosphorylation sites [(S/T)-P motif], designated P1-P4, on the pre-S protein of duck hepatitis B virus (DHBV) have been mutated. Mutants include single (P2, P3, P4) and double amino acid substitutions (P1 + P2, P3 + P4) and one with all four sites mutated (4P). Serine at position 118 (P3) was identified as the major site of phosphorylation by Western blotting and radioimmunoprecipitation after in vitro cell labeling with [35S]methionine or [33P]orthophosphate. Mutant virions generated by transfection of LMH cells were infectious both in vitro in duck hepatocyte primary cultures and in vivo in Pekin ducks. Intracellular relaxed circular (RC) and covalently closed circular (ccc) DNA syntheses were not affected by the P3 mutation or even the quadruple mutant. Extracellular virus production was slightly increased when the P3 site was mutated. CsCl gradient centrifugation showed no clear difference between mutant and wild-type virus with respect to the ratios of enveloped virus and nucleocapsid particles in hepatocyte culture supernatants. Trypsin or V8 protease digestion with or without NP-40 indicated that phosphorylation of the pre-S domain is not involved in determining the transmembrane topology of DHBV large protein. This phenotypic analysis indicates that DHBV pre-S phosphorylation has no apparent effect on DHBV replication and formation of mature viral particles in duck hepatocyte primary culture and does not affect infectivity in ducklings.

A novel vector for the study of hepatitis delta virus replication

In order to study HDV replication without the difficulties caused by the use of a multimeric construction and to obtain a selectable expression vector, a minimal amount of antigenomic HDV cDNA, sufficient to initiate RNA dependent replication was cloned into the plasmid pUTSV1. The first plasmid, pUTdelta1.7, contained 1.7 genomes of HDV cDNA. After transfection of pUTdelta1.7 into HuH7 cells, antigenomic HDV RNA was produced, processed and could enter into the replicative cycle of HDV. However, after transfection of an antigenomic ribozyme mutant (pUTdelta1.7(AGR)) constructed on the same model, plasmid DNA dependent production of genomic HDV RNA was observed, especially in COS7 cells. It seems that a promoter within vector sequences downstream from the HDV insert may initiate counter-clockwise transcription of the plasmid. The presence of two genomic ribozymes in the insert permits the excision of a genome length genomic HDV RNA from this counter-clockwise transcript. In order to allow quantitative analysis of HDV replication, this problem was eliminated by removing the second genomic ribozyme from the insert to give the vector pUTdelta1.5. This vector can be used conveniently for transfection experiments to explore HDV biology.

Design, synthesis and structure relationships of new N,N',N",N"'-tetrakis (omega-amino alkyl) tetraazamacrocycles

A number of N,N',N",N"'-tetrakis (omega-aminoalkyl) tetraazamacrocycles and related compounds were synthesized and evaluated for their inhibitory effects on human immunodeficiency virus type 1 (HIV-1) and duck hepatitis B virus (DHBV) replication. The activity of these compounds was found to be highly dependent upon structural features: (i) the length of the alkyl linker connecting the nitrogen atoms of the macrocyclic ring to the exocyclic nitrogen atoms of the terminal amino groups (five methylenes favoured antiviral activity); (ii) substitution of the terminal amino groups of the linker reduced antiviral activity; and (iii) the size of the tetraazamacrocyclic ring (14 or 15 atoms) did not markedly affect the antiviral activity. Some analogues were potent inhibitors of HIV-1 replication, with anti-HIV activity similar to that of biscyclam (JM 2763). In contrast, other analogues were found to be highly toxic in duck hepatocyte primary culture, the 2.2.15 cell line and to a lesser extent in MT-4 cells. Structural parameters, macrocyclic ring size and metal-chelating ability have been used to develop a structure-activity relationship model in order to aid the design of antiviral molecules derived from N,N',N",N"'-tetrakis (omega-aminoalkyl) tetraazamacrocycles.

Selective inhibition of the duck hepatitis B virus by a new class of tetraazamacrocycles

The antiviral activity of a new class of N,N,N',N",NA'''-pentakis (omega-aminoalkyl) tetraazamacrocycles was evaluated in primary duck hepatocyte cultures infected with the duck hepatitis B virus (DHBV). Three of the four tested compounds were able to selectively inhibit DHBV replication by acting at an early step of the hepadnavirus infection but were associated with significant toxicity.

n-Butyrate, a cell cycle blocker, inhibits early amplification of duck hepatitis B virus covalently closed circular DNA after in vitro infection of duck hepatocytes

During chronic hepadnavirus infection, virus persistence depends on the regulation of the pool of covalently closed circular DNA (cccDNA), which is the template for transcription of viral RNA species. The development of in vitro infection of duck hepatocyte primary cultures by duck hepatitis B virus (DHBV) provides a unique opportunity to study the regulation of cccDNA synthesis. After DHBV in vitro infection, cccDNA is detected 1 day later and is amplified to a high copy number after 1 week in culture. We studied whether this amplification occurs during cell cycle progression of duckling hepatocytes. By using [3H]thymidine incorporation, we found that hepatocytes obtained from 3-week-old ducklings spontaneously entered the S phase of the cell cycle when cultured in serum-free medium without added growth factors. Bromodeoxyuridine labeling confirmed that cellular DNA synthesis took place in more than 50% of parenchymal cells. Cytofluorometry analysis revealed the presence of asynchronous populations and polyploidization processes. The addition of a cell cycle blocker, n-butyrate, completely inhibited [3H]thymidine incorporation and blocked duckling hepatocytes in the G1 phase of the cell cycle. Simultaneously, butyrate inhibited cccDNA amplification and allowed the establishment of DHBV infection, as demonstrated by the detection of a basal level of cccDNA in treated hepatocytes. Both effects were reversible since active cell DNA synthesis was restored and cccDNA accumulated after drug withdrawal.

2',3'-dideoxy-beta-L-5-fluorocytidine inhibits duck hepatitis B virus reverse transcription and suppresses viral DNA synthesis in hepatocytes, both in vitro and in vivo

beta-L-Nucleoside analogs represent a new class of potent antiviral agents with low cytotoxicity which provide new hope in the therapy of chronic hepatitis B virus (HBV) infections. We evaluated the anti-HBV activity of 2',3'-dideoxy-beta-L-5-fluorocytidine (beta-L-F-ddC), a beta-L-nucleoside analog derived from 2',3'-dideoxycytidine (ddC), in the duck HBV (DHBV) model. This compound was previously shown to inhibit HBV DNA synthesis in a stably transfected hepatoma cell line (F2215). Using a cell-free system for the expression of an enzymatically active DHBV polymerase, we could demonstrate that the triphosphate form of beta-L-F-ddC does inhibit hepadnavirus reverse transcription. In primary duck hepatocyte culture, beta-L-F-ddC showed a potent inhibitory effect on DHBV DNA synthesis which was concentration dependent. Although beta-L-F-ddC was shown to be less active than ddC against the DHBV reverse transcriptase in vitro, beta-L-F-ddC was a stronger inhibitor in hepatocytes. The oral administration of beta-L-F-ddC in experimentally infected ducklings showed that beta-L-F-ddC is a potent inhibitor of viral replication in vivo. Short-term therapy could not prevent a rebound of viral replication after the drug was withdrawn. Preventive therapy with beta-L-F-ddC could delay the onset of viremia by only 1 day compared with the time to the onset of viremia in the control group. The in vivo inhibitory effect of beta-L-F-ddC was much stronger than that of ddC and was not associated with signs of toxicity. Our data show that beta-L-F-ddC inhibits hepadnavirus reverse transcription and is a strong inhibitor of viral replication both in vitro and in vivo.

Clinical relevance of the detection of hepatitis delta virus RNA in serum by RNA hybridization and polymerase chain reaction

Hepatitis delta virus nucleic acid was detected by dot-blot hybridization using RNA probe and reverse transcription/polymerase chain reaction amplification in 223 serum samples from 66 patients with hepatitis D virus infection. Seven cases with chronic hepatitis D virus infection were treated with interferon: six for 3 months and one for 7.5 years. By using the primers located in the putative conserved regions, the technique of reverse transcription/polymerase chain reaction amplification was 10(3) to 10(4) times more sensitive than that of dot-blot hybridization. The main findings of this study are: (i) HDV RNA could be detected in the absence of any other serological hepatitis D virus marker in serum from acute hepatitis patients with IgM anti-HBc; (ii) high titer anti-HD antibodies (IgM and total anti-HD) persisted in patients during short-term interferon treatment, and in one patient during long-term interferon treatment, despite clearance of serum HDV RNA even after 3 years; (iii) total anti-HD alone was detected in the absence of IgM anti-HD and serum HDV RNA. These observations indicate that the detection of HDV RNA by molecular techniques in serum is a useful, sensitive and non-invasive technique for the early diagnosis and follow up of hepatitis D virus infection, as well as for the monitoring of antiviral therapy. In addition, total anti-HD antibody in the absence of HDV RNA may be the only residual marker of past infection. Finally, the choice of the technique for hepatitis D virus detection is important for the optimal assessment of the clinical stage and monitoring of antiviral therapy in hepatitis D virus-infected patients.

Synthesis and antiviral activity of new carbonylphosphonate 2',3'-dideoxy-3'-thiacytidine conjugates

The synthesis of new potential PFA-BCH-189 conjugate analogues is described and their molecular structure clearly identified through NMR and mass spectra techniques. The anti-HIV-1 activity was determined according to the inhibition of syncytium formation in MT-4 cells, while the anti-HBV activity was determined in infected duck hepatocytes. Both antiviral activities of the PFA-BCH-189 conjugates were much lower than those of the parent BCH-189 (2',3'-dideoxy-3'-thiacytidine) (1). Whereas a prodrug effect, following cleavage and release of the free BCH-189 and PFA, cannot be ruled out, poor cellular permeation of the drug seems to be the most likely reason for the reduced activities against HIV and DHBV. The presence of the PFA moiety appears to be detrimental for both the anti-HIV and anti-DHBV activity of PFA-BCH-189 cases.

Selective detection of human hepatitis B virus surface and core antigens in peripheral blood mononuclear cell subsets by flow cytometry

The presence of hepatitis B surface protein (HBs) and hepatitis B core protein (HBc) was investigated, by flow cytometry, on the surface of peripheral mononuclear cells (PBMC) from cells of the following phenotype: CD3 (T lymphocytes), CD4 (T helper/ inducer), CD8 (T cytotoxic/suppressor), CD19 (B lymphocytes) and CD56 [natural killer (NK) cells] among eight patients suffering from chronic hepatitis B and five healthy HBV-negative subjects. This study demonstrated the presence of HBsAg and HBcAg on the lymphocyte surface for most of the patients. The mean percentage of labelled cells was 17% for HBsAg and 15% for HBcAg. Among the different lymphocyte subsets only B lymphocytes and the NK cells expressed HBsAg for 57% and 26% of cells, respectively. Similarly HBcAg was also detected among CD19 and CD56 cells only. Polymerase chain reaction (PCR) was used to search for the presence of hepatitis B virus (HBV) DNA and RNA in PBMC, using primers located in the S gene. HBV DNA was detected with variable intensity in the CD3, CD4, CD19 and CD56 subsets following their separation with a cell sorter. For HBV RNA the signal obtained after PCR and Southern blotting was higher for CD56 and CD19 cells than for CD3 cells and undetectable for CD4 cells. This study demonstrates that replication and transcription of the HBV can occur in CD19- and CD56-positive cells. Positive signals in CD3 cells may be due to contamination of this subpopulation by NK cells.

Heterogeneity of hepatitis C virus genotypes in France

The genotypes of French hepatitis C virus (HCV) isolates were investigated by amplification of a domain from the non-structural region 3 (NS3) using nested PCR, followed by hybridization with two genotype-specific probes, F1 (HCV type I-specific) and F2 (HCV type II-specific). Among 119 HCV RNA-positive sera, 91% of samples were NS3 PCR positive. Most samples (83.2%) hybridized with one or the other probe only, whereas a few samples (4.2%) hybridized with both F1 and F2 probes (HB). A small percentage (3.4%) of samples appeared unable to hybridize with either probe (HN). For some of these samples (HB1, HB2, HN1, HN2, HN3, HN4), part of the NS3, core and envelope regions were sequenced and the corresponding deduced consensus sequences were compared with those of prototype isolates of the four HCV genotypes (types I to IV). A phylogenetic tree was constructed to illustrate the relationship between these isolates. The results obtained showed that (i) HN4 appears to be more closely related to type III than to type IV HCV genotypes, which suggests that in France there may exist additional although minor genotypes besides the two major types, F1 and F2. (ii) HB1, HB2, HN1, HN2 and probably HN3 belong to the type II HCV genotype. The association between sequence diversity and putative biological difference for isolates within the same genotype remains to be elucidated.

Monitoring of early events of experimental woodchuck hepatitis infection: studies of peripheral blood mononuclear cells by cytofluorometry and PCR

The peripheral blood mononuclear cells (PBMC) of woodchucks experimentally infected by woodchuck hepatitis virus (WHV) were examined simultaneously for the presence of membrane associated WHV antigens by cytofluorometry, and for WHV DNA and RNA sequences by the polymerase chain reaction (PCR). Four woodchucks were inoculated: two with a well-defined infectious inoculum and two with an inoculum obtained from an animal at the late incubation phase, which was positive for WHV DNA by PCR but still devoid of WHV markers. Infection was demonstrated in all four inoculated woodchucks by the appearance at different times of WHV DNA and WHV antigens in both leucocytes and serum. WHV DNA was first detected by PCR either in the serum (two cases) or in leucocytes (two cases). The mean percentage of cells positive for membrane associated WHsAg or WHcAg detected by cytofluorometry were 37% +/- 25 and 17% +/- 15 respectively. After 8 weeks, all inoculated animals were WHsAg positive in serum. These data suggest that PBMC are involved in the early events of hepadnavirus infection. They also show that sera which are positive by PCR for WHV DNA may transmit viral infection even while still seronegative for WHV markers and for WHV DNA by dot blot.

Discovery of a novel point mutation changing the HDAg expression of a hepatitis delta virus isolate from Central African Republic

None of the mutations so far discovered in several hepatitis delta virus (HDV) isolates appears to determine important changes in HDV specific protein (HDAg) expression, except for a putative mutation at nucleotide 1012 converting an amber stop codon (TAG) to a codon for tryptophan (TGG). Here we present the characterization of an HDV obtained from the liver of a woodchuck inoculated with sera from fulminant HDV patients in Central African Republic (CAR). By restriction enzyme analysis and sequencing of HDAg-coding region cDNA clones, we found that this HDV isolate bears a novel mutation (T to A) at nucleotide 1013 which converts the amber stop codon (TAG) to a codon for lysine (AAG). Comparison of these nucleotide sequences with those available from American, Japanese, Taiwanese, French, Italian and Nauru isolates showed a variability of 1.7 to 21.5% and 1.9 to 28.7% at the nucleic acid and amino acid levels, respectively. The HDAg-encoding sequence of the CAR isolate is closely related to that of the Italian HDV isolate. The in vitro expression of this HDV isolate resulted in a unique HDAg species (28K) which was identical with that characterized in vivo.

Direct cloning and expression of PCR amplified DNA and RNA sequences: application to the hepadnaviruses nucleocapsid proteins

Gene amplification may benefit from the construction of primers that augments the speed at which cloning and protein expression proceeds. Such primers include EcoRI or HindIII linkers as well as an in phase initiation or termination codon. PCR was carried out directly from viral particles of human hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV) without DNA purification and from RNA extracted from WHV infected liver. Amplified products were directly cloned in the pKK223-3 expression vector under the control of the tac promoter. The characterization of the recombinant clones expressing the nucleocapsid protein (C protein) was done by direct incubation of the filter with 125I-labelled anti-HBc and confirmed by radioimmunoassay and Western-blot analysis. This procedure allows easy selection of recombinant clones expressing a given protein and could be applied to many other genes.

Viral spliced RNA are produced, encapsidated and reverse transcribed during in vivo woodchuck hepatitis virus infection

By the use of reverse transcription followed by polymerase chain reaction (RT-PCR), we have identified one shorter than full-length, pregenomic viral RNA species in liver samples of woodchucks chronically infected with the woodchuck hepatitis virus (WHV). The spliced WHV RNA of about 2.4 kb in length was cloned and partially sequenced. The splicing donor and acceptor sites of this novel RNA are located, respectively, 130 nucleotides downstream of the ATG initiation codon of the core gene and 21 nucleotides upstream of the initiation codon of the pre-S2 surface gene. The splicing event generates a new core-polymerase fusion protein and removes the terminal protein domain and the spacer region of the polymerase gene. A nucleotide probe specific for the splice junction was used following RT-PCR, to further confirm the existence of this spliced RNA in the liver of seven WHV-infected woodchucks. Deleted viral DNA molecules corresponding to the 2.4 kb spliced RNA were also detected in the liver and, to a lesser extent, in the serum of infected woodchucks, suggesting that this spliced RNA can be encapsidated and reverse-transcribed during the course of natural WHV infection.

Effects of 2'-fluorinated arabinosyl-pyrimidine nucleosides on duck hepatitis B virus DNA level in serum and liver of chronically infected ducks

The 2'-fluorinated arabinosyl-pyrimidine nucleosides, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), are new antiviral compounds with in vitro inhibitory activity against the DNA polymerase of hepadnaviruses. Those compounds also induced permanent inhibition of viral replication in woodchucks chronically infected by woodchuck hepatitis virus. The effects of these antiviral compounds were assessed in ducks chronically infected by duck hepatitis B virus (DHBV). Following intraperitoneal administration for 5 days, FMAU (2 mg/kg/day) and FIAC (10 mg/kg/day) induced a transient decrease in DHBV replication, as shown by the decrease in both the serum and liver DHBV DNA level. After stopping therapy, DHBV replication rebounded immediately to the pretreatment level. The supercoiled form of liver viral DNA was found to be less affected by the therapy. By contrast, no obvious antiviral effect was observed with vidarabine monophosphate (ara-AMP) (80 mg/kg/day) therapy. No sign of toxicity was observed during the course of the treatment. These preliminary results confirmed in the DHBV model the higher efficacy of FIAC and FMAU as compared to ara-AMP. Pharmacokinetic studies are needed to explain the differences observed in viral replication in these 2 models of HBV infection.

Transmission of serologically silent hepatitis B virus along with hepatitis C virus in two cases of posttransfusion hepatitis

The polymerase chain reaction (PCR) was used to investigate the presence of hepatitis B virus (HBV)-related DNA sequences in blood from three blood donors and two transfusion recipients who developed posttransfusion non-A, non-B hepatitis (NANBH). In the first case, the sole donor was positive for antibody to hepatitis B surface (HBs) and core (HBc) antigens and had elevated alanine aminotransferase (ALT) levels, while the recipient had no HBV serologic markers. Both the donor and the recipient had serologic markers of hepatitis C virus (HCV) and were found positive for HBV DNA and HCV RNA sequences by PCR. The second case involved two donors and one recipient. Serologic tests for conventional HBV markers were negative in all three individuals, but one of the donors had elevated ALT. HBV DNA sequences were detected by PCR in the serum of the recipient and of the donor with high ALT, but not in the serum of the donor with normal ALT. Anti-HCV was detected in the serum of the recipient and of the suspect donor but not in that of the donor with normal ALT. The sequences amplified in the S region and determined after cloning of PCR products for both donor-recipient pairs were indistinguishable from each other and identical to the sequence of the major HBV subtype of adw in the first case and ayw in the second case. Furthermore, for the second case, an identical single-point mutation was found in both the donor and the recipient. These data confirm the transmission of conserved HBV sequences together with HCV in posttransfusion NANBH.(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration of woodchuck hepatitis virus infection of peripheral blood mononuclear cells by flow cytometry and polymerase chain reaction

Peripheral blood mononuclear cells (PBMCs) from 10 woodchuck hepatitis virus (WHV)-infected woodchucks were examined for the presence of WHV surface (WHs) and core (WHc) antigens (WHsAg and WHcAg) by cytofluorometry using fluorescein isothiocyanate-conjugated anti-WHs and anti-HBc-purified immunoglobulins from woodchuck and human sera. The presence of viral DNA and RNA was detected in the serum and PBMCs from the same blood samples by polymerase chain reaction (PCR) with two primer sets located in the S and C genes of the WHV genome. Seven animals were found positive for both WHsAg and WHcAg on the surface of PBMCs: four WHV-chronic carriers, two WHsAg-positive animals with acute WHV infection, and one woodchuck which was bled during the incubation phase of WHV infection and which became WHsAg-positive only 1 month later. Sixteen to 71% of the studied leukocyte population expressed WHsAg with a low density of expression whereas 7 to 72% expressed WHcAg with a high density of expression. Only two cases were positive for WHsAg without WHcAg on PBMCs, one WHV chronic carrier and one anti-WHs-positive animal. All woodchucks positive for WHcAg and/or WHsAg by cytofluorometry were positive also for WHV DNA and RNA in PBMCs by PCR. The tenth animal was found negative for both viral antigens as well as for WHV DNA and RNA in PBMCs despite the presence of persistent viral DNA in the serum as detected by PCR. Five healthy woodchucks devoid of WHV serological markers served as negative controls. These results obtained with a novel approach further confirm, in the woodchuck model, that a significant proportion of PBMCs are probably permissive for WHV replication. The possible immunopathogenic implications of the phenomenon are discussed.

Detection of polyadenylated RNA in hepatitis B virus-infected peripheral blood mononuclear cells by polymerase chain reaction

Polymerase chain reaction (PCR) with a reverse transcriptase step characterized a specific transcription activity in hepatitis B virus (HBV)-infected peripheral blood mononuclear cells (PBMC) in two patients (1 and 2) with chronic hepatitis positive for antibody to hepatitis B core antigen (HBc). Patient 1 was also coinfected with human hepatitis delta virus. A patient who cleared HBV replication after antiviral treatment with vidarabine served as negative control. HBV-specific RNA poly A sequences were detected by PCR in PBMC of patients 1 and 2 even without detectable HBV DNA (patient 2) as shown by dot blot and PCR assays. RNA sequences were found in both the nucleus and cytoplasm. The demonstration of HBV mRNA sequences within PBMC suggests the transcription of viral DNA, in agreement with the findings of HBV surface antigen in PBMC. The results in patient 1 demonstrated HBV mRNA sequences in leukocytes even without PCR-detectable HBV DNA sequences, likely due to ongoing hepatitis delta virus replication.

Correlation between HBV DNA detection by polymerase chain reaction and Pre-S1 antigenemia in symptomatic and asymptomatic hepatitis B virus infections

The presence of hepatitis B virus (HBV) genome in sera from 73 symptomatic and asymptomatic HBsAg carriers was studied by the polymerase chain reaction (PCR) with primers specific for the S and C regions. Pre-S proteins of the HBV envelope were detected in serum by a specific monoclonal antibody in a double immunoradiometric assay. Out of twenty-five symptomatic patients with chronic active hepatitis (14 with HBeAg and 11 with anti-HBe), all were positive for HBV DNA by PCR, while 14/14 HBeAg and 2/11 (18%) of the anti-HBe patients were positive by dot blot hybridization. All but one anti-HBe patient (96%) carried Pre-S1 proteins. Among the asymptomatic HBsAg carriers, HBV DNA was detected by PCR in 14/14 (100%) HBeAg positive patients and in 25/34 (73%) anti-HBe positive patients. Pre-S1 proteins were found, respectively, in 14/14 (100%) and 11/22 (50%) of the same cases tested in parallel. The 20 healthy blood donors devoid of HBV markers and with normal transaminases tested were found negative for HBV DNA using PCR. Out of 12 patients who recovered from acute hepatitis B, all were found negative by PCR analysis after a mean follow up of 1 year after seroconversion to anti-HBs. When serial samples from 2 patients (one with acute hepatitis B, the other with chronic hepatitis B) were tested for the presence of HBV DNA and of Pre-S1 proteins, both markers showed parallel development.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of 2'-fluorinated arabinosyl-pyrimidine nucleosides on woodchuck hepatitis virus replication in chronically infected woodchucks

The treatment of woodchuck hepatitis virus infections with 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), given intraperitoneally, caused complete and permanent decrease of serum virus endogenous DNA polymerase and viral DNA in all treated woodchucks but was associated with severe toxicity. By contrast 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-ethyluracil (FEAU) induced a sustained, although less dramatic, decrease of viral replication without apparent toxic effect. FEAU was also effective when given orally. However, in both cases this inhibitory effect was transient.

Prolonged duck hepatitis B virus replication in duck hepatocytes cocultivated with rat epithelial cells: a useful system for antiviral testing

Duck cultured hepatocytes from Pekin ducks naturally infected by duck hepatitis B virus can remain functional twice longer if a coculture system with rat liver epithelial cells is used instead of ordinary primary culture. The use of a selective medium in which ornithine and lactate replaced arginine and glucose, respectively, allowed viral replication initiated in vivo to be maintained in the coculture for 2 months. Several antiviral compounds including the pyrophosphate analog (phosphonoformic acid) or nucleoside analogs (9 beta-arabinofuranosyl AMP, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine, 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-ethyluracil and 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl thymine) were studied in both culture systems for their ability to inhibit duck hepatitis B virus replication. Hepatocytes were treated for 7 days with 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-ethyluracil (10 microM) and 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl thymine (0.5 microM) or for 14 days with 9 beta-arabinofuranosyl AMP (90 microM), phosphonoformic acid (100 microM) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (6 microM). The effects of the drugs on viral replication were monitored by testing for duck hepatitis B virus DNA in the culture supernatant and in the cells by molecular hybridization.(ABSTRACT TRUNCATED AT 250 WORDS)

Main properties of duck hepatitis B virus DNA polymerase: comparison with the human and woodchuck hepatitis B virus DNA polymerases

The main properties of the duck hepatitis B virus (DHBV) DNA polymerase have been studied and compared with those of the human hepatitis B virus (HBV) and of the woodchuck hepatitis virus (WHV) DNA polymerases. All 3 enzymes are active under high salt conditions in the presence of high magnesium concentration. DHBV DNA polymerase was found less sensitive to ethanol and to operate at higher optimal pH than the HBV and WHV DNA polymerases. Like the other two viral endogenous DNA polymerases, the DHBV enzyme was strongly inhibited by phosphonoformic acid but not by aphidicolin, sulfhydryl group blockers or phosphonoacetic acid. Inhibition of DHBV DNA polymerase by the triphosphate derivatives of several nucleoside analogs appeared similar to that reported for HBV or WHV endogenous polymerase. FIACTP was the most, and ACVTP the least effective inhibitor; BVdUTP was of intermediary potency; araCTP and araTTP had a greater inhibitory effect on DHBV DNA polymerase than HBV or WHV DNA polymerase. The similarities in the properties of DHBV and HBV DNA polymerase justify the use of the duck hepatitis B polymerase model for screening and evaluation of potentially active drugs against HBV infection.

Maintenance of woodchuck hepatitis virus activity in woodchuck hepatocyte primary culture

Primary cultures of non-proliferating hepatocytes isolated by the two-step collagenase perfusion method from woodchuck naturally infected with hepatitis virus (WHV) were used to study WHV propagation in vitro. Hepatocytes carrying WHV DNA exhibited a very high level of survival and retained their morphological characteristics for 2 to 3 months. Over this time, they were found to produce virus-specific proteins and release viral particles with DNA polymerase activity into the medium. Using Southern blot analysis and a recombinant hepatitis B virus DNA plasmid probe, intracellular and extracellular viral DNA was consistently detected. Only extrachromosomal forms of WHV DNA were observed and no integration could be demonstrated in the DNA of the cells. The WHV DNA patterns were repeatedly identical with a characteristic smear starting from 3.3 kb associated with other smaller DNA fragments which presumably represented intermediate replicative forms of viral DNA. Furthermore, dot blot hybridization of the total RNA revealed the presence of WHV-specific transcripts in cells after 3 weeks of culture. All these results are compatible with the maintenance of active WHV replication in vitro although it was somewhat reduced after the first day of culture. This provides a mammalian model for hepadnavirus replication studies in stable primary hepatocyte cultures.

Evidence for the presence of duck hepatitis B virus in wild migrating ducks

A virus closely related to duck hepatitis B virus (DHBV) was isolated from serum and liver samples of wild migratory ducks (mallards) caught in two separate wildlife reserve parks in France. In the first one (Dombes region) 12% of wild mallards were positive for DHBV, and in the second (River Somme) 3% of mallards were found positive. The DHBV isolated from the serum of wild mallards was also associated with an endogenous DNA polymerase activity capable in vitro of completing a partially double-stranded viral DNA into a fully double-stranded DNA of 3 kb. The various replicative DNA forms reported for DHBV were also detected in the liver of wild viraemic mallards. The DNA restriction enzyme pattern of the wild mallard strain differed from that of American and French strains of DHBV. The wild mallard strain DHBV was experimentally transmitted to mallard and Pekin ducklings and induced a chronic viraemia in both varieties of infected birds. This strain might be the common ancestor of all DHBV strains isolated from domestic ducks world-wide. The discovery of a DHBV-related virus in the natural wild population might be an important clue in the study of the different roles of environmental, host and viral factors in the pathogenesis of DHBV infection, and their possible oncogenic action in ducks.

Therapeutic potential of acyclovir and of the interferons in HBV-related chronic active hepatitis due to HBV with or without HDV superinfection

Acyclovir only demonstrated activity in CAH patients with low HBV replication (DNA-p less than or equal to 80 cpm). In those, oral acyclovir 4 g/day for 4 months was able to permanently inhibit DNA-p in 5/5 cases without significant side-effects.

Therapeutic activity of vidarabine in symptomatic chronic active hepatitis related to HBV

The potential inhibitory effects of nucleoside analogues such as ARA-A and acyclovir on HBV-DNA-polymerase were first demonstrated in vitro and then confirmed in vivo in open dose finding studies. The therapeutic efficacy of both ARA-A and ARA-AMP which appeared the most potent drugs was then confirmed by various studies in symptomatic HBeAg-positive patients. These studies demonstrated a similar benefit of therapy with 38 and 40% of treated patients given ARA-A and ARA-AMP, respectively, who permanently cleared HBV replication after a single course, and 67-80% who did so after two courses. Significant improvement in transaminases and histologic activity was also documented (P less than 0.001). Myalgias were observed in 10 and 30% of the patients, respectively. Patients who failed to respond to nucleosides, and those coinfected with HDV, were treated with interferons. Out of 8 cases of HDV/CAH given 5 MU thrice weekly of fibroblast beta-interferon (UPSA) for 3 months, DNA-p activity fell transiently in all 6 initially elevated cases. A parallel decrease in anti-HD titers (P less than or equal to 0.05), inflammation (P less than or equal to 0.001) and necrosis (P less than or equal to 0.05) were observed. alpha-Recombinant interferon was given i.m. for 4 months (2-7 MU/m2 X 2/7 days) to 10 CAH with high DNA-p values. HBV replication was permanently inhibited in 4 cases and dramatically reduced in 3 additional patients. Three failed to respond. Careful monitoring of DNA-p values appeared to be the single most important factor in assessing activity.

Comparative study of DHBV DNA levels and endogenous DNA polymerase activity in naturally infected ducklings in France

Duck hepatitis B virus (DHBV) was found in the serum of 1-6% of Pekin ducklings originated from French commercial flocks. The viremia was followed in the serum of 5 ducklings over a span of 3 mth by monitoring the levels of DHBV DNA and the endogenous DNA polymerase (DNAp) activity. The DHBV DNA levels in serum were quantified either by the DNA dot hybridization technique including counting of retained radioactivity, or by successive dilutions of each serum sample followed by DNA hybridization. The counting of the retained radioactivity was plotted on a curve and its evolution compared with that of viral DNAp activity. DHBV DNA levels in serum, estimated by both methods paralleled those of the DNAp activity, which peaked at the 4th or 5th week posthatch to decrease and fluctuate thereafter. Occasional discordance between DHBV DNA levels and the endogenous DNAp activity was observed, which could be correlated with the degree of repair of the single stranded gap of serum DHBV DNA. Parallel follow up studies comparing quantitative estimations of serum viral DNA and of DNAp activity, as presented here, may provide some clues for the understanding of the mechanisms involved in the establishment of the HEPA DNA virus carrier state. Such comparative studies may also be crucial for optimal monitoring of antiviral drugs in both human clinical trials and animal experimental studies.

Woodchuck hepatitis virus infection: serologic and histopathologic course and outcome

Five out of seven American woodchucks inoculated with woodchuck hepatitis virus developed antigenemia after 2 to 13 weeks followed by an antibody response. One animal became a carrier, and another animal exhibited a primary antibody response. Clinical disease was not obvious and aminotransferase elevation could not be demonstrated. Liver biopsy showed mononuclear portal infiltration and little parenchymal cell necrosis.

Inhibition of human and woodchuck hepatitis virus DNA polymerase by the triphosphates of acyclovir, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine and E-5-(2-bromovinyl)-2'-deoxyuridine

The triphosphates of acyclovir (ACV), 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (FIAC) and E-5-(2-bromovinyl)-2'-deoxyuridine (BVdU) have been examined for their inhibitory effects on the endogenous DNA polymerase reactions of human hepatitis B virus (HBV) and woodchuck hepatitis virus (WHV). All three triphosphates (ACVTP, FIACTP and BVdUTP) inhibited the HBV and WHV DNA polymerases by competing with the corresponding natural substrates. FIACTP was the most potent inhibitor of HBV and WHV DNA polymerase while ACVTP was the least effective inhibitor. The inhibitory properties of these compounds were compared with those of the 5'-triphosphates of 1-beta-arabinofuranosyl-cytosine (ara-CTP) and 1-beta-arabinofuranosylthymine (ara-TTP). The 50% inhibitory doses for HBV and WHV DNA polymerases were in the following order: FIACTP less than BVdUTP less than ara-TTP less than ACVTP less than ara-CTP. BVdUTP appeared to be an efficient alternate substrate to dTTP for HBV DNA polymerase while FIACTP was much less efficient when substituted for dCTP. ACVTP did not act as an alternate substrate to dGTP and appeared to prevent DNA chain elongation.

Immunopathologic aspects of woodchuck hepatitis

The natural history of infection with woodchuck hepatitis virus (WHV) has been studied in a colony of 38 Marmota monax. Besides serologic assessment for WHV markers, light-microscopic findings of 61 liver biopsies were correlated with the results of immunofluorescence analysis for nucleocapsid (WHcAg) and surface (WHsAg) antigens. Twenty-four chronic WHsAg carriers all featured signs of continuous viral replication. Two major immunomorphologic patterns were observed in their livers: 1) portal hepatitis in which WHcAg accumulated in the cytoplasm and WHsAg was associated with the hepatocyte membrane and 2) periportal hepatitis in which WHcAg shifted toward nuclear localization and WHsAg became mostly intracytoplasmic. Progression from portal to periportal hepatitis, observed in 7 woodchucks, appeared to be induced by a partial recovery of specific immune reactivity to WHV, insufficient, however, to interrupt WHV replication. Deposits of WHsAg and immunoglobulins were present in the kidney and spleen of animals with severe hepatitis.

Comparison of properties of woodchuck hepatitis virus and human hepatitis B virus endogenous DNA polymerases

The principal properties of the DNA polymerases of woodchuck hepatitis virus and human hepatitis B virus were compared. The enzymes of both viruses exhibited optimal activities in the same range of pH, ionic strength, and MgCl2 concentration. Like human hepatitis B virus DNA polymerase, the woodchuck hepatitis virus DNA polymerase was strongly inhibited by phosphonoformic acid but not by phosphonoacetic acid and aphidicolin. Similar inhibition patterns for both enzymes were observed with arabinofuranosyl nucleotides (9-beta-D-arabinofuranosyladenine-5'-triphosphate, 1-beta-D-arabinofuranosylcytosine-5'-triphosphate, 1-beta-D-arabinofuranosylthymine-5'-triphosphate) and dideoxythymidine triphosphate, whereas no effect was obtained with corresponding nucleosides. The therapeutic significance of these results and the relevance of the woodchuck as an experimental animal model for the study of human hepatitis B virus infections are discussed.

Use of the cross-reactivity with hepatitis B virus antigens and antibodies for the demonstration of a woodchuck hepatitis virus 'e' antigen-antibody system

Woodchucks hepatitis virus (WHV)-associated antigens and antibodies were studied using current sensitive radio- or enzyme immunoassays (RIA, EIA). A significant cross-reactivity was observed between hepatitis B surface antigen (HBsAg) and woodchuck hepatitis surface antigen (WHsAg) using RIA or EIA (Abbott Laboratories, North Chicago, Ill., U.S.A.) although not with two other commercial EIA tested (Organon Technika, Oss, The Netherlands; Behringwerke AG, Marburg, F.R.G.). A weak but significant reactivity was also found when woodchuck sera positive for WHsAg or anti-WHs by immunodiffusion were tested for HBeAg and anti-HBe by RIA, suggesting the existence of a WHeAg-anti-WHe system in infected woodchucks. The specificity of this e-anti-e reactivity in the woodchuck was further confirmed by successful absorption experiments. WHsAg and WHeAg could be distinguished serologically by immunodiffusion and separated from each other by ultracentrifugation and ammonium sulphate precipitation. A WHeAg preparation was used to boost the presumed natural antibody activity of an immune woodchuck. The specific anti-HBe response detected by RIA during the immunization experiments demonstrated the existence of a soluble WHeAg cross-reacting with the human HBe-anti-HBe system. This was confirmed in immunodiffusion by a partial identity between the precipitin lines formed by the WHeAg-anti-Whe and HBeAg-anti-HBe reaction. Whether the WHe-Ag-anti-WHe system wil mimick HBeAg and anti-HBe in all their clinico-pathological correlations, deserves further study.

Antigenic cross-reactions between woodchuck hepatitis virus and human hepatitis B virus shown by immune electron microscopy

Using immune electron microscopy (IEM), low-level cross-reactions could be demonstrated between the surface antigens of hepatitis B and woodchuck hepatitis. However, immune complex formation was greatly enhanced by pre-exposure of the antigens to 0.5% deoxycholate. Cross-reaction between the core antigens and e antigens of both viruses was also confirmed by IEM as well as radioimmunoassay. It appears that the woodchuck sera used in this study may well contain an anti-immunoglobulin akin to rheumatoid factor.

Detection by immunofluorescence of a new "core-like" Ag/Ab system in liver and serum of patients with NANB hepatitis

Using direct immunofluorescence, a nuclear antigen was found in liver of chronic hepatitis patients with circulating NANBe Ag or anti-NANBe, and selected sera from either group were used as source of conjugates. The new Ag/Ab system was designated NANBc Ag and anti-NANBc since it behaved like the core Ag of HBV . NANBc Ag was detected in coded frozen liver biopsies from patients with chronic persistent 15/25 (60%) or active 27/50 (54%) hepatitis and cryptogenic cirrhosis 16/30 (53.3%) devoid of HBV markers. Only 2/30 alcoholic cirrhosis cases (7%) used as controls were positive (p less than or equal to 0.001). The homologous anti-NANBc antibody was always detectable by indirect immunofluorescence in the patients' serum when NANBc Ag was found in the liver. It was also found in 11/135 (8%) additional cases without any other NANB marker. A correlation was observed between coded detection of the NANBc Ag/Ab system by immunofluorescence and demonstration of NANBe Ag or anti-NANBe by immunodiffusion. In acute post-transfusion NANB hepatitis, anti-NANBc was first detectable 14 days after transfusion and persisted as long as ALT remained elevated, or longer. IgM anti-NANBc present at onset became associated with an increasing proportion of IgG after the 28th day. The prevalence of anti-NANBc in sporadic NANB hepatitis (11/50 = 22%) was significantly lower (p less than or equal to 0.001) than in cases with parenteral exposure such as post-transfusion, occupational or drug addict hepatitis (47/72 = 65%). Immunofluorescent tests for NANBc Ag and Ab are promising assays for the serological diagnosis of NANB hepatitis.

Non-A, Non-B hepatitis virus: identification of a core antigen-antibody system that cross reacts with hepatitis B core antigen and antibody

Using immunodiffusion, a major cross-reactivity had been previously demonstrated between hepatitis B(HBe/3 Ag) and the antigen reported in the serum on non A, non-B hepatitis patients, therefore redesignated NANBe Ag. By direct immunofluorescence a new antigen associated with, but distinct from, NANBe Ag has now been identified in the liver of 14/26 patients with NANB chronic active hepatitis. The homologous antibody was detected in the serum of these 14 patients. Behaving like HBc Ag and cross reacting with it by immunofluorescence, the new antigen was termed NANBc Ag. Anti NANBc also became detectable in serial acute phase and convalescence sera from 5/5 NANB Ag-positive posttransfusion hepatitis cases. Further characterization of NANBe and NANBc antigens achieved by fractionation of a NANB virus-infected liver showed NANBc Ag to be expressed on 22-25 nm HB core-like particles containing DNA polymerase activity. Cross-reactivity between NANBc and HBc antigens was confirmed by immunodiffusion. Liver-derived NANBe Ag identical to serum NANBe Ag exhibited the same physical properties as HBe/3 Ag and could be similarly released by disruption of the non-A, non-B, virus cores. These results indicate that hepatitis B and NANB virions not only share the same structure and DNA polymerase activity but are also antigenically related and belong to the same new class of DNA viruses.