Biomedical subjects

J L Gerin

Publications and source records attributed to J L Gerin.

At least 37 records · Page 2Linked to original sources

PubMed1998

Genotype-specific complementation of hepatitis delta virus RNA replication by hepatitis delta antigen.

Characterizations of genetic variations among hepatitis delta virus (HDV) isolates have focused principally on phylogenetic analysis of sequences, which vary by 30 to 40% among three genotypes and about 10 to 15% among isolates of the same genotype. The significance of the sequence differences has been unclear but could be responsible for pathogenic variations associated with the different genotypes. Studies of the mechanisms of HDV replication have been limited to cDNA clones from HDV genotype I, which is the most common. To perform a comparative analysis of HDV RNA replication in genotypes I and III, we have obtained a full-length cDNA clone from an HDV genotype III isolate. In transfected Huh-7 cells, the functional roles of the two forms of the viral protein, hepatitis delta antigen (HDAg), in HDV RNA replication are similar for both genotypes I and III; the short form is required for RNA replication, while the long form inhibits replication. For both genotypes, HDAg was able to support replication of RNAs of the same genotype that were mutated so as to be defective for HDAg production. Surprisingly, however, neither genotype I nor genotype III HDAg was able to support replication of such mutated RNAs of the other genotype. The inability of genotype III HDAg to support replication of genotype I RNA could have been due to a weak interaction between the RNA and HDAg. The clear genotype-specific activity of HDAg in supporting HDV RNA replication confirms the original categorization of HDV sequences in three genotypes and further suggests that these should be referred to as types (i.e., HDV-I and HDV-III) rather than genotypes.

Cloning, Molecular↗

PubMed1998

Preclinical investigation of L-FMAU as an anti-hepatitis B virus agent.

Preclinical aspects of a potent anti-hepatitis B virus (HBV) L-nucleoside, 1-(2-fluoro-5-methyl-beta-L-arabino-furanosyl)uracil (L-FMAU) are described. L-FMAU was prepared from L-ribose derivatives via either L-xylose or L-arabinose. L-FMAU shows potent antiviral activity against hepatitis B virus (EC50 5.0 microM in H1 cells) with high selectivity in vitro. L-FMAU is not incorporated into mitochondrial DNA and no significant lactic acid production was observed in vitro. L-FMAU is phosphorylated by thymidine kinase as well as deoxycytidine kinase, ultimately to the triphosphate, which inhibits HBV DNA polymerase as the mechanism of antiviral action. Preliminary in vivo toxological studies suggest no apparent toxicity for 30 days at 50 mg/kg/day in mice and for 3 months in woodchucks (10 mg/kg/day). L-FMAU also has respectable bioavailability in rats. L-FMAU shows potent anti-HBV activity in vivo against woodchuck hepatitis virus in chronically infected woodchucks and there is no significant virus rebound after cessation of the drug treatment.

Animals↗

PubMed1997

Geographic distribution and genetic variability of hepatitis delta virus genotype I.

Three genotypes of hepatitis delta virus (HDV) have been identified, each with different geographic distributions and disease associations. To better define the geographic distribution and genetic variability of HDV genotype I, and to evaluate the extent of genome variability in populations with different patterns of HDV infection, we have analyzed the sequence of HDV RNA in the sera of 72 patients from different areas. Patients were primarily residents of the United States and areas in and around Greece, including Archangelos, Rhodes. All sequences obtained belonged to HDV genotype I, confirming the wide geographic distribution of this genotype and its predominance in Europe and the United States. In contrast to previous studies, phylogenetic analysis of this large and diverse group of sequences, along with all available previously published HDV sequences, showed no well-defined subtypes within genotype I. Low sequence diversity was found for isolates from the United States, Archangelos, Turkey, and Albania, suggesting that HDV was introduced more recently and/or from fewer sources into these areas as compared to mainland Greece, Italy, and north Africa, where sequence diversity is much greater. The low sequence diversity among isolates from Archangelos is particularly interesting in light of the unusually mild pattern of HDV disease found in this community. Comparison of nucleic acid and amino acid sequences within and among genotypes indicated both highly conserved regions as well as genotype-specific sequences that could be related to functional differences. The most distinctive of the latter was that corresponding to the C-terminal 19-20 amino acids of the long form of hepatitis delta antigen, which is highly conserved within each genotype but considerably diverged among them.

Amino Acid Sequence↗

PubMed1997

Cloning and characterization of partial cDNAs for woodchuck cytokines and CD3epsilon with applications for the detection of RNA expression in tissues by RT-PCR assay.

Immunologic reagents and methodology are essential to develop further the woodchuck and woodchuck hepatitis virus (WHV) as a model of immune response, inflammation, and immunotherapy in hepatitis B virus (HBV) infection. Partial cDNA clones for the woodchuck CD3epsilon marker of T cells (536 bp) and for selected woodchuck cytokines were developed, including IL-1beta (332 bp), IL-2 (249 bp), IL-4 (205 bp), IL-10 (476 bp), IFN-gamma (476 bp), and TNF-alpha (381 bp). This panel of markers includes sets to measure RNAs for T cells (CD3epsilon), immune response induction (IL-1beta, IL-2), TH subsets (TH1, IL-2/IFN-gamma vs. TH2, IL-4/IL-10), and effector molecules that regulate hepadnavirus replication and liver injury (IFN-gamma, TNF-alpha). Primers representing highly conserved segments of genes from other species were used to derive the partial cDNA clones. Target RNA was obtained from woodchuck peripheral blood mononuclear cells (PBMC) that were stimulated in vitro with ConA, LPS, and human rIL-2. The cDNA clones were validated by 1) comparison with other species for homologies in the nucleotide and predicted amino acid sequences and 2) a first generation assay demonstrating induction of the respective RT-PCR products in stimulated woodchuck PBMC. The corresponding RNAs were also detectable in most cases in the total RNA from the livers of uninfected and WHV-infected woodchucks and differential expression of IFN-gamma and TNF-alpha RNAs was suggested. Second generation, semi-quantitative assays for the RNAs were validated using RT-PCR and dot-blot hybridization with 32P-oligomers derived from the internal sequences of the respective clones. Continued study of the woodchuck immune response to WHV infection using these assays will provide insight into the kinetics and immune mechanisms that initiate and maintain chronic hepadnavirus infection and, hence, enable development of improved immunotherapies for established chronic HBV infection.

Amino Acid Sequence↗

PubMed1997

The predominance of hepatitis delta virus genotype I among chronically infected Italian patients.

The sera of 46 Italian patients with chronic hepatitis delta virus (HDV) infection were analyzed for HDV RNA by polymerase chain reaction (PCR) amplification. Genetic analysis of sequences amplified from two regions of the HDV genome indicated that all HDV RNA-positive patients (98%) were infected with HDV genotype I. In Italy, infection with this genotype appeared to be associated with a broad spectrum of chronic disease. No subtypes of HDV genotype I were identified, nor were genetic variations clearly associated with different disease patterns; however, clustering of some sequences suggested correlations with geography and transmission route. Italian HDV genotype I sequences were more diverse than those from east Asia and North America, suggesting that HDV genotype I was likely introduced to Italy earlier and/or from multiple sources as compared to those areas. All sequences analyzed were predicted to fold into the unbranched rod structure typical of HDV RNA. Within this structure, three conserved features were identified, including sequences around the RNA editing site and the polyadenylation signal site. We conclude that in Italy, where HDV infection has been endemic, the overwhelmingly predominant genotype of HDV is genotype I.

Adult↗

PubMed1997

Hepatic expression of the woodchuck hepatitis virus X-antigen during acute and chronic infection and detection of a woodchuck hepatitis virus X-antigen antibody response.

The expression and localization of the woodchuck hepatitis virus X-antigen (WHxAg) was examined and compared with other markers of a woodchuck hepatitis virus (WHV) infection using rabbit antisera generated against recombinant WHxAg produced in bacteria. Cellular fractionation studies showed that WHxAg was localized to the soluble and cytoskeletal fractions of the cell when assayed by immunoprecipitation of [35S]-met-cys labeled extracts derived from primary cultures of acute WHV-infected hepatocytes. Immunohistochemical examination of liver from chronic WHV-infected animals showed WHV core antigen (WHcAg) and WHxAg expression in non-neoplastic tissue. The WHxAg was found localized to the cytoplasm of infected cells, similar to WHcAg. WHxAg expression was diminished in the foci of altered hepatocytes and in hepatocellular adenomas but was found in only 1 of 11 hepatocellular carcinomas (HCC). Hepatic biopsies from woodchucks experimentally inoculated with WHV were examined during the acute phase of infection and during convalescence for WHcAg and WHxAg expression by immunohistochemistry. Concurrent expression of WHcAg and WHxAg was observed during the viremic phase of infection. The two antigens exhibited similar localization to the cell cytoplasm, similar distribution within the liver lobule, and similar patterns of clearance during convalescence. An immune response to WHxAg was documented in some woodchucks following acute WHV infection. These studies further define the woodchuck model of HBV infection and should allow for the investigation of the role of hepadnaviral X-antigen expression in the pathogenesis of chronic hepatitis and HCC.

Acute Disease↗

PubMed1997

Recombinant vaccine against hepatitis E: dose response and protection against heterologous challenge.

Thirty-two rhesus monkeys were used to evaluate the dose response of a recombinant HEV vaccine, and the efficacy of the vaccine based on the ORF2 protein of the Pakistani strain for pre- and post-exposure vaccination against intravenous challenge with homologous or heterologous virus was examined. Post-exposure vaccination did not protect animals against hepatitis. Although primates vaccinated twice with 50-microgram, 10-microgram, 2-microgram, or 0.4-microgram doses of the recombinant 55 kDa ORF-2 protein were infected, they were protected from hepatitis when they were challenged with very high doses of the homologous strain of HEV. Primates vaccinated twice with a 50 micrograms dose of the recombinant protein were protected from hepatitis after heterologous challenge with the Mexican strain, the strain of HEV most genetically distant from the Pakistani strain.

Animals↗

PubMed1997

Depletion of mitochondrial DNA, destruction of mitochondria, and accumulation of lipid droplets result from fialuridine treatment in woodchucks (Marmota monax).

Fialuridine (FIAU, 1-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-5-iodouracil) is toxic to liver, heart, muscle, and nerve in clinical trials for chronic viral hepatitis (CH). Mitochondrial toxicity was hypothesized. To address pathophysiologic mechanisms, we examined mitochondrial changes in FIAU-treated woodchucks (WC) with CH from woodchuck hepatitis virus infection. WC (with and without CH from woodchuck hepatitis virus infection) were treated with FIAU (1.5 mg/kg/day) for 12 weeks. WC were killed. Liver, heart, skeletal muscle, and kidney samples underwent DNA extraction and were analyzed ultrastructurally (transmission electron microscopy). Myocardium, skeletal muscles, and liver samples were analyzed histologically. Abundance of hepatic, myocardial, muscle, and kidney mtDNA decreased in FIAU-treated WC, but the magnitude varied. mtDNA decreased 55% in heart, 65% in kidney, 74% in liver, and 87% in muscle (p < 0.02 for each tissue: FIAU-treated versus FIAU-untreated). Cellular damage was characterized ultrastructurally by mitochondrial enlargement, cristae dissolution, and lipid droplets. Lipid droplets found in the heart, diaphragm, biceps, and liver were sufficient to identify FIAU-treated WC (p < 0.05 each). Widespread mitochondrial damage to many tissues resulted from chronic FIAU treatment and occurred irrespective of CH. It manifested with mtDNA depletion, intracytoplasmic lipid droplets, and destroyed mitochondrial cristae. Defective mtDNA replication with mtDNA depletion seems central to the subcellular pathophysiology of altered energy metabolism and multiorgan failure in FIAU toxicity.

Animals↗

PubMed1996

DNA vaccine for hepatitis B: evidence for immunogenicity in chimpanzees and comparison with other vaccines.

Vaccination of two chimpanzees against hepatitis B virus (HBV) by intramuscular injection of plasmid DNA encoding the major and middle HBV envelope proteins induced group-, subtype- and preS2-specific antibodies. These were initially of IgM isotype, and then they were of IgG (predominantly IgGl) isotype. The chimpanzee injected with 2 mg of DNA attained >100 milli-international units/ml of anti-HBs antibody after one injection and 14,000 milli-international units/ml after four injections. A smaller dose (400 microg) induced lower and transient titers, but a strong anamnestic response occurred 1 year later. Comparison with responses in 23 chimpanzees receiving various antigen-based HBV vaccines suggests that the DNA approach is promising for prophylactic immunization against HBV.

Animals↗

PubMed1996

Liver-targeted antiviral nucleosides: enhanced antiviral activity of phosphatidyl-dideoxyguanosine versus dideoxyguanosine in woodchuck hepatitis virus infection in vivo.

It would be desirable to develop antiviral agents that can be targeted to liver to enhance their antiviral effects and reduce nonhepatic toxicity. 2',3'-Dideoxyguanosine (ddG) has been found to be a potent and selective antihepatitis B agent both in vitro and in vivo. To evaluate ddG and its liver-targeted analog, we synthesized a series of phosphatidyl-ddGs and incubated them with 2.2.15 cells, which chronically produce hepatitis B virus. 1,2-Dipalmitoylphosphatidyl-dideoxyguanosine (DPP-ddG) inhibited the production of hepatitis B virus (HBV) DNA in the culture medium by 90% at 4.5 mumol/L versus 9.1 mumol/L for ddG, while the liposome vehicle itself had no effect. To compare the efficacy of free ddG with its lipid prodrug in vivo, we treated woodchucks that were experimentally infected with woodchuck hepatitis virus (WHV) for 4 weeks by intraperitoneal injection of 2.6 mumol/kg/d of free ddG or liposomes containing 2.6 mumol/kg/d of DPP-ddG. Liposomal DPP-ddG reduced serum WHV DNA by 23- to 46-fold at the end of the fourth week, while free ddG reduced serum WHV DNA by 2.2- to 10.4-fold. Treatment with small unilamellar liposomes containing DPP-ddG is substantially more effective than free ddG in reducing WHV-DNA levels in serum in WHV-infected woodchucks. The data suggest that the use of lipid prodrugs to target the liver may be useful in enhancing antiviral therapy of hepatitis.

Animals↗

PubMed1996

Hepatitis B virus (HBV)/hepatitis D virus (HDV) coinfection in outbreaks of acute hepatitis in the Peruvian Amazon basin: the roles of HDV genotype III and HBV genotype F.

Recurring outbreaks of acute hepatitis have been a significant cause of morbidity and mortality among Peruvian military personnel stationed in the Amazon Basin region of Peru. The role of hepatitis B virus (HBV) and hepatitis D virus (HDV) infection was investigated as the possible cause of acute hepatitis among 88 military patients stationed at four different jungle outposts during 1992-1993. Analysis of serum markers indicated that 95% (84/88) had evidence of acute HBV infection; 64% (54/84) were also infected with HDV. Genetic analysis of PCR-amplified HDV and HBV fragments showed exclusively HDV genotype III and HBV genotype F. Furthermore, HDV RNA sequences were similar among patients from the same outpost but different from those at other jungle locations. The data suggested focal sources of HDV infection in the jungle environment of the outposts and, further, confirmed the unique association of HDV genotype III with severe cases of human disease in northern South America.

Acute Disease↗

PubMed1995

Antisense oligonucleotides are effective inhibitors of hepatitis B virus replication in vitro.

Antisense oligonucleotides are currently being used in numerous laboratories as potential anticancer and antiviral agents. The unique replication cycle of hepatitis B virus (HBV) contains several different steps which are potentially amenable to modulation by these molecules. We have examined the ability of 56 different single-stranded, oligodeoxyribonucleotides (14-23 nucleotides in length), which target several HBV-specific functions, to inhibit HBV replication in the human hepatoblastoma cell line, 2.2.15. None of the oligonucleotides examined were toxic at concentrations up to 500 microM. Oligonucleotides directed against the HBV surface antigen (HBsAg) gene (S gene), the preS1 open reading frame, and the HBV core antigen (HBcAg) gene (C gene) were effective at depressing virus production, while molecules targeting the HBV e antigen (HBeAg) open reading frame and the HBV polymerase (POL) gene were ineffective. Oligonucleotides directed against the HBV encapsidation signal/structure (epsilon) comprised some of the most effective antiviral molecules against HBV. None of 5 oligonucleotides complementary (i.e., 'sense' orientation) to the antisense oligonucleotides targeting HBsAg, HBcAg, HBeAg, preS1 and POL had any measurable effect on HBV production. The relative effectiveness of oligonucleotides targeting the S and C genes on HBV replication was highly correlated with an effect on HBsAg or HBcAg levels, respectively. None of the antisense oligonucleotides examined affected either the levels or the sizes of HBV-specific RNA transcripts. Since antisense oligonucleotides can exert biologic effects on HBV in 2.2.15 cell cultures in a sequence-specific manner which are consistent with predicted modes of action, such molecules may have practical applications in the therapy of chronic HBV infection.

Antiviral Agents↗

PubMed1995

Hepatitis D virus RNA editing: specific modification of adenosine in the antigenomic RNA.

RNA editing plays a central role in the life cycle of hepatitis D virus (HDV), a subviral human pathogen. Previous studies (J.L. Casey, K.F. Bergmann, T.L. Brown, and J.L. Gerin, Proc. Natl. Acad. Sci USA 89:7149-7153, 1992; H. Zheng, T.-B. Fu, D. Lazinski, and J. Taylor, J. Virol. 66:4693-4697, 1992) had concluded that the genomic RNA of HDV was the target for RNA editing and that the editing reaction was a conversion of U to C. However, we show here that the antigenomic RNA of HDV is in fact the target for HDV RNA editing, which is therefore a conversion of A to G. This result is verified by using an assay specific for editing on the antigenomic RNA and by analyzing the editing of site-directed mutant RNAs in transfected cells and in cell extracts. Because editing occurs in the absence of viral antigens and the specificity for the HDV editing target site is present even in extracts from Drosophila cells, it is likely that HDV RNA is edited by one or more cellular factors that are conserved among higher eukaryotes. These results raise the likelihood that double-stranded RNA adenosine deaminase specifically edits HDV antigenomic RNA.

Adenosine↗

PubMed1995

In vitro activation of woodchuck lymphocytes measured by radiopurine incorporation and interleukin-2 production: implications for modeling immunity and therapy in hepatitis B virus infection.

Cellular immune responses to hepatitis B virus (HBV) play an important role in the resolution of acute infection. They also influence the course of chronic infection and disease but are inadequate to completely clear the infection. Woodchuck hepatitis virus (WHV) infection of the woodchuck can provide a model to study these processes. Lymphocyte responses of woodchucks were assessed by in vitro proliferation and/or interleukin (IL)-2 assays using mitogen (Concanavalin A [ConA]), cytokine (IL-2), superantigen (Staphylococcus aureus enterotoxin B [SEB]), major histocompatibility complex (MHC) allo-antigen (mixed lymphocyte reaction [MLR]), and viral antigens (woodchuck hepatitis virus core antigen [WHcAg] and woodchuck hepatitis virus surface antigen [WHsAg]). ConA-stimulated woodchuck lymphocytes underwent cell division based on cell counting experiments and produced IL-2 as detected using an IL-2-dependent murine cell line but failed to incorporate sufficient tritiated thymidine; however, they did incorporate sufficient tritiated adenosine and deoxyadenosine to permit development of a meaningful proliferation assay. The IL-2 assay was sensitive and specific for detection of woodchuck IL-2 induced by mitogen, superantigen, and MLR, as shown by quantitative titration analysis and anti-body neutralization of ConA-supernatant activity. Cyclosporin A and FK506 specifically inhibited ConA- and SEB-induced IL-2 production by woodchuck lymphocytes. Positive two-way MLRs were detected by IL-2 production and proliferation assay between woodchucks from different geographic regions, thus indicating divergence among MHC molecules; however, occasional negative MLR reactions among indigenous pairs of woodchucks indicated that some woodchucks were mutually immunocompatible to some degree. The radioadenosine proliferation assay was sensitive for detecting peripheral blood lymphocyte responses to WHcAg and WHsAg in adult woodchucks with recently resolved acute infections. The above systems should facilitate the design of adoptive therapy and liver transplantation experiments in the woodchuck, and also enable modeling of immune responses that promote and maintain chronic hepadnavirus infection.

Animals↗

PubMed1994

Successful passive and active immunization of cynomolgus monkeys against hepatitis E.

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

Animals↗

PubMed1994

DNA ploidy analysis of hepatic preneoplastic and neoplastic lesions in woodchucks experimentally infected with woodchuck hepatitis virus.

We analyzed the DNA ploidy and the nuclear size of hepatocytes within hepatocellular carcinoma, putative preneoplastic (clear cell and basophilic foci) and adjacent non-neoplastic liver in 30 woodchucks neonatally infected with the woodchuck hepatitis virus. In livers from control woodchucks, in clear cell foci and in most chronic portal hepatitis, the hepatocytes were diploid, with less than 10% tetraploid cells. Aneuploid peaks were found in 50% of the livers with chronic active hepatitis, in 63% of basophilic foci and in 90% of hepatocellular carcinoma. Within the same tumor, aneuploid peaks with different DNA indices were observed frequently, indicating heterogeneity of tumor. S-phase was always elevated, indicating an increased rate of proliferation. Aneuploid cells had nuclei that were larger than those of control liver cells. In some basophilic foci and in some livers with chronic active hepatitis, abnormal DNA was demonstrated before the development of hepatocellular carcinoma, suggesting that these may be populations of hepatocytes at risk of neoplastic transformation.

Aneuploidy↗

PubMed1994

Woodchuck hepatitis virus surface antigen induces nitric oxide synthesis in hepatocytes: possible role in hepatocarcinogenesis.

Woodchuck hepatitis virus surface antigen (WHsAg) stimulated hepatocytes in culture to produce nitric oxide (NO.), as evidenced by the accumulation of nitrite in the medium. NO. synthesis by hepatocytes was positively correlated with WHsAg concentration. WHsAg-induced NO. synthesis was inhibited by NG-monomethyl-L-arginine and anti-WHsAg antibody. To our knowledge, this is the first demonstration of an increase in NO. formation by a viral antigen. These data, when considered in the light of the known genotoxicity of NO., raise the possibility that viral hepatitis increases the risk of liver cancer by increasing the production of NO.. Long-term elevated production of NO. free radicals due to stimulation by WHsAg in chronic hepatitis may directly cause reactions with cellular DNA leading to mutagenesis, as well as the formation of hepatocarcinogenic N-nitroso compounds. This provides a new mechanism by which hepatitis B virus infection might hypothetically increase the risk of liver cancer.

Animals↗

PubMed1994

Apparent helper-independent infection of woodchucks by hepatitis delta virus and subsequent rescue with woodchuck hepatitis virus.

Hepatitis delta virus (HDV) is a subviral agent of humans which is dependent upon hepatitis B virus as a helper for transmission. HDV can be experimentally transmitted to woodchucks by using woodchuck hepatitis virus (WHV) as the helper. We used this model system to study two types of HDV infections: those of animals already chronically infected with WHV and those of animals without any evidence of prior exposure to WHV. At 5 to 10 days after infection with HDV, liver biopsies of these two groups of animals indicated that around 1% of the hepatocytes were infected (HDV antigen positive). Moreover, similar amounts of replicative forms of HDV RNA were detected. In contrast, by 20 days postinfection, the two groups of animals were quite different in the extent of the HDV infection. The animals chronically infected with WHV showed spread of the infection within the liver and the release of high titers of HDV into the serum. In contrast, the animals not previously exposed to WHV showed a progressive reduction in liver involvement, and at no time up to 165 days postinfection could we detect HDV particles in the serum. However, if these animals were inoculated with a relatively high titer of WHV at either 7 or even 33 days after the HDV infection, HDV viremia was observed. Our data support the interpretation that in these animals, hepatocytes were initially infected in the absence of helper virus, HDV genome replication took place, and ultimately these replicating genomes were rescued by the secondary WHV infection. The observation that HDV can survive in the liver for at least 33 days in the absence of coinfecting helper virus may be relevant to the reemergence of HDV infection following liver transplantation.

Animals↗