Inhibition of human hepatitis B virus replication by AT-61, a phenylpropenamide derivative, alone and in combination with (-)beta-L-2',3'-dideoxy-3'-thiacytidine

AT-61, a member of a novel class of phenylpropenamide derivatives, was found to be a highly selective and potent inhibitor of human hepatitis B virus (HBV) replication in four different human hepatoblastoma cell lines which support the replication of HBV (i.e., HepAD38, HepAD79, 2.2.15, and transiently transfected HepG2 cells). This compound was equally effective at inhibiting both the formation of intracellular immature core particles and the release of extracellular virions, with 50% effective concentrations ranging from 0.6 to 5.7 microM. AT-61 (27 microM) was able to reduce the amount of HBV covalently closed circular DNA found in the nuclei of HepAD38 cells by >99%. AT-61 at concentrations of >27 microM had little effect on the amount of viral RNA found within the cytoplasms of induced HepAD38 cells but reduced the number of immature virions which contained pregenomic RNA by >99%. The potency of AT-61 was not affected by one of the mutations responsible for (-)-beta-L-2', 3'-dideoxy-3' thiacytidine (3TC) resistance in HBV, and AT-61 acted synergistic with 3TC to inhibit HBV replication. AT-61 (81 microM) was not cytotoxic or antiproliferative to several cell lines and had no antiviral effect on woodchuck or duck HBV, human immunodeficiency virus type 1, herpes simplex virus type 1, vesicular stomatitis virus, or Newcastle disease virus. Therefore, we concluded that the antiviral activity of AT-61 is specific for HBV replication and most likely occurs at one of the steps between the synthesis of viral RNA and the packaging of pregenomic RNA into immature core particles.     

Pathogenesis of hepatitis B and C-induced hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is estimated to have an annual worldwide incidence of 0.25 to 1.2 million new cases per year. Both the prevalence and incidence of HCC vary markedly as a function of geography and the local prevalence of chronic viral hepatitis. Both chronic hepatitis B and chronic hepatitis C are recognized as risk factors for HCC. The prevalence of cirrhosis in individuals with HCC and chronic hepatitis B or C is reported to be 80.9% and 75.8%, respectively. HCC occurs at a lower rate in chronic viral hepatitis in the absence of cirrhosis. Moreover, hepatitis C virus (HCV) rather than hepatitis B virus (HBV) is associated with the majority of non-cirrhotic cases of HCC. It is probable that the ongoing process of hepatocyte necrosis and liver cell renewal coupled with inflammation, which is characteristic of chronic viral hepatitis, causes not only nodular regeneration and cirrhosis but also progressive genomic errors in hepatocytes as well as unregulated growth and repair mechanisms leading to hepatocyte dysplasia and, in some cases, hepatic carcinoma. Current concepts concerning virus-induced HCC are reported and discussed in the following review.     

The M539V polymerase variant of human hepatitis B virus demonstrates resistance to 2'-deoxy-3'-thiacytidine and a reduced ability to synthesize viral DNA

The cytosine analog 2'-deoxy-3'-thiacytidine (3TC) has been shown to be an effective treatment for chronic hepatitis B virus (HBV) infection. However, several liver transplant patients who were undergoing treatment with 3TC for HBV infection experienced a breakthrough of virus while on 3TC. The predominant virus found in these patients' sera contained either a valine or isoleucine for the methionine in the highly conserved YMDD nucleotide binding site in the HBV polymerase. To determine the biological relevance of the Met-to-Val substitution, we mutated a plasmid that contained a cDNA copy of the HBV pregenomic RNA such that when virus replication occurred during transient transfection of HepG2 cells, an M539V polymerase variant was produced. We found that in transiently transfected cells, this variant was approximately 330-fold less sensitive to the antiviral effects of 3TC and produced 7-fold less viral DNA than the wild type.     

Pathogenetic effector function of CD4-positive T helper 1 cells in hepatitis B virus transgenic mice

The pathogenetic effector functions of hepatitis B virus (HBV)-specific CD4+, Th1 cells were analyzed in two inbred lineages of HBV transgenic mice, one of which overexpresses the HBV large envelope protein rendering the hepatocytes hypersensitive to the cytopathic effects of IFN-gamma, and another that expresses all of the HBV proteins and replicates the virus in the liver. Transfer of HBV envelope-specific Th1 cells resulted in recognition of viral Ag expressed by hepatic nonparenchymal cells, cytokine release, and a transient necroinflammatory liver disease in both lineages. The liver disease was very severe in the IFN-gamma-sensitive lineage, and it was less severe in the lineage that replicates the HBV genome; nonetheless, in this lineage the Th1 cytokines produced by these cells suppressed viral replication in the liver. These results demonstrate that CD4+ T cells with a Th1 functional phenotype can perform pathogenetic and antiviral effector functions in vivo. This suggests that CD4+ T cells can contribute directly to disease pathogenesis and inhibit viral replication during HBV infection.     

Functional analysis of HBV genomes from patients with fulminant hepatitis

Two previous case reports suggest that hepatitis B virus (HBV) core promoter variants with a high replication competence contribute to the pathogenesis of fulminant hepatitis B (FHB). We recently found in HBV genomes from patients with FHB an accumulation of mutations within the core promoter region. Therefore, the aim of this study was to investigate the phenotype of these HBV variants. Replication competence and expression of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) of viral genomes from seven patients with FHB and one patient with fulminant recurrent hepatitis after liver transplantation were analyzed by transfection experiments in human hepatoma cells. Compared with wild-type virus, the HBV variants from the seven patients with FHB produced similar or slightly lower levels of intracellular replicative intermediates and extracellular viral particles. In contrast, the HBV genomes from the patient with fulminant recurrent hepatitis synthesized and secreted significantly more HBV DNA. All genomes tested expressed similar or even higher levels of HBeAg compared with wild-type virus, except for those from four patients with a precore stop codon mutation in the respective dominant viral populations. The level of HBsAg produced by all variant genomes was similar or reduced compared with wild-type virus. These data indicate that in some cases HBV variants with enhanced replication competence and/or a defect in HBeAg expression may contribute to the development of FHB. However, neither phenotype is an essential prerequisite; thus, an additional role of other viral or host factors in the pathogenesis of FHB is suggested.     

Effects of mutations within and adjacent to the terminal repeats of hepatitis B virus pregenomic RNA on viral DNA synthesis

The viral polymerase and several cis-acting sequences are essential for hepadnaviral DNA replication, but additional host factors are likely to be involved in this process. We previously identified two sequences, UBS and DBS (upstream and downstream binding sites), present in multiple copies in and adjacent to the pregenomic RNA (pgRNA) terminal redundancy, that were specifically recognized by a 65-kDa host factor, p65. The possible roles of these two sequences in hepatitis B virus (HBV) replication were investigated in the context of the intact viral genome. UBS is contained within the terminal redundancy of pgRNA, and the 5' copy of this sequence is essential for viral replication. Mutations within the central core of UBS ablate p65 binding and selectively block synthesis of plus-strand DNA, without affecting RNA packaging or minus-strand synthesis. The DBS sequence, which is located downstream of the pgRNA polyadenylation site, overlaps the core (C) protein coding region. All mutations introduced into this site severely affected viral replication. However, these effects were shown to result from dominant negative effects of mutant core polypeptides rather than from cis-acting effects on RNA recognition. Thus, the 5' UBS but not DBS sites play important cis-acting roles in HBV DNA replication; however, the involvement of p65 in these roles remains a matter for investigation.     

Regulation of hepatitis B virus mRNA expression in a hepatitis B surface antigen transgenic mouse model by IFN-gamma-secreting T cells after DNA-based immunization

The immunotherapeutic effect of DNA-mediated immunization against chronic hepatitis B virus (HBV) infection has been evaluated in transgenic mice expressing the sequences that code for the envelope proteins of HBV in the liver. In this model of HBV chronic carriers, a single i.m. injection of plasmid DNA encoding HBV envelope proteins is sufficient to generate specific immune responses leading to the clearance of the transgene expression product and the control of HBV mRNA. The relative contributions of the T cell subpopulations induced by DNA immunization were examined using adoptive transfer experiments. It was shown that either CD8+ or CD4+ T lymphocytes from immunocompetent DNA-immunized animals were sufficient to control viral gene expression in the livers of the recipient transgenic mice. This effect was mediated by a cytokine-dependent mechanism common to both T cell subpopulations; this mechanism did not require cell lysis, but did involve the production of IFN-gamma by the activated T cells.     

Psychological adjustment of children with mild and moderately severe asthma

In chronic hepatitis B virus (HBV) infection seroconversion from hepatitis B e antigen (HBeAg) to hepatitis B e antibody (HBeAb) may be followed either by remission of the disease with low-level viraemia, or by continuing inflammation with high-level viraemia. In both situations the virus may acquire a mutation in the precore sequence which prevents it from encoding HBeAg. We now show that the number of amino acid substitutions in the HBV core is low in viral sequences from patients with HBeAg positive chronic liver disease and HBeAg negative HBeAb positive patients in remission, but the frequency of substitutions is high in HBeAg, negative HBeAb positive patients with active liver disease. Furthermore we show that these substitutions cluster in the promiscuous CD4+ T-helper-cell epitope and in HBV core/e antibody binding determinants, but are not found in regions recognized by major histocompatability complex (MHC) restricted cytotoxic T lymphocytes. Sequential viral sequences from patients before and after HBeAg/HbeAb seroconversion shows that core mutations arise either at the same time or after the precore stop mutation which prevents the virus from encoding HBeAg. These results are consistent with the hypothesis that after clearance of HBeAg, mutations in regions of the virus recognized by CD4+ helper T cells and B cells allow persistence of the HBe negative virus in HBeAb positive patients with viraemia and active hepatitis.     

The immunological diagnosis of chronic viral hepatitis

Chronic viral diseases of the liver are associated with changes in immune reactions mediated by T and B lymphocytes and dependent in severity on etiological factor (virus of hepatitis B, delta, C, their combination), the disease stage (hepatitis, cirrhosis), the process activity, kind of immune correction. HBsAg, viral hepatitis B marker, was detected in 21.2% of 1400 cases with chronic active hepatitis and liver cirrhosis. 32% of HbsAg-seropositive patients had antibodies to delta-antigen. Antibodies to HBsAg, HCV were found in 27.7 and 14.9% of the above patients. Chronic viral diseases of the liver with persistence of HBV, HDV and HCV markers are characterized by a complex of immune disorders, including a moderate rise in peripheral blood of IgM, IgG, IgA, IgE, Ig kappa, lambda, immune complexes, cryoglobulins, autoantibodies to subcellular structures as well as changes in regulatory (suppressor, helper) and effector (lymphokine-producing) functions of T lymphocytes, inhibition of phagocytosing capacity. The above shifts in immune status, clinical and biochemical activity of the disease are more pronounced in chronic active hepatitis with HCV markers compared to BHV. Of maximal intensity they were in combined viral infection HBV+HDV or HBV+HCV.     

Prevalence of hepatitis B virus markers among intravenous drug abusers in Stockholm: impact of heterosexual transmission

In order to study the importance of sexual transmission of hepatitis B virus (HBV) among intravenous drug abusers (IVDAs), and from IVDAs to others, we consecutively interviewed 171 IVDAs detained at the Stockholm Remand Prison during 4 months in 1990. Sexual histories revealed that 77% reported > or = 3 sexual partners during the last 3 years, 64% had had a sexual partner who did not inject drugs, and 61% reported a prior STD. The prevalence of HBV markers was 75%. In a multiple logistic regression analysis, a high risk for HBV markers was associated with an increasing duration of drug abuse, a high prevalence of hepatitis A markers, and an increasing number of drug injecting sexual partners during the last 3 years, indicating that sexual transmission, along with sharing of needles, may contribute to the high prevalence of HBV markers within this group. It is suggested that an adequate sexual history must be obtained from IVDAs with acute viral hepatitis in order to identify sexual partners who should be offered postexposure prophylaxis, and that non-immune IVDAs should be vaccinated against viral hepatitis A and B.     

The clinical importance of carpal instabilities following distal radial fractures

The association of viremia, elevated serum alanine aminotransferase (ALT) levels, and hepatocyte inflammatory activity in hepatocellular carcinoma (HCC) patients was studied. Serum samples from 114 HCC patients undergoing surgery were assayed for hepatitis B, C, and D viral nucleic acids by polymerase chain reaction (PCR) prior to surgery. Of these patients, 65 had HBV infection alone, 15 had HCV infection alone, 4 had HDV infection, 20 had HBV and HCV superinfection, 1 had triple viral infection, and 9 were negative for HBV and HCV infections. The prevalence of active viral replication was significantly higher in HCV than in HBV (92% versus 70%; P = 0.006) patients, and significantly higher mean serum ALT levels were also noted in the HCV group than in the HBV group (P = 0.02). The incidence of marked ALT elevation (>200 U/l) was highest in the HCV (27%) and the HDV (25%) groups. Patients in the HCV group were 10 years older than those in the HBV group. Viral superinfection did not accelerate the development of HCC. Viral replication persisted in a significant portion of HCC patients and a higher prevalence of hepatic inflammation was noted in patients with HCV- and, possibly, HDV-related HCC.     

Inhibition of hepatitis B virus replication during adenovirus and cytomegalovirus infections in transgenic mice

We have previously demonstrated that hepatitis B virus (HBV) replication and gene expression are abolished in the livers of HBV transgenic mice by cytotoxic T lymphocytes (CTLs) and during lymphocytic choriomeningitis virus (LCMV) infection, stimuli that trigger the production of alpha/beta interferon, gamma interferon, and tumor necrosis factor alpha in the liver. We now report that hepatic HBV replication and gene expression are inhibited by the local induction of these cytokines during adenovirus- and murine cytomegalovirus (MCMV)-induced hepatitis. Further, we show that MCMV also blocks HBV replication and gene expression in the proximal convoluted tubules of the kidney by causing interstitial nephritis and inducing the same cytokines in the renal parenchyma. These results suggest that inflammatory cytokines probably contribute to viral clearance during acute viral hepatitis in humans, and they imply that induction of these cytokines in the liver and other infected tissues of chronically infected patients might have therapeutic value.     

Pro-apoptotic effect of the hepatitis B virus X gene

The hepatitis B virus (HBV) is a common human pathogen that causes acute and chronic liver disease. Persistent HBV infection is strongly associated with the development of hepatocellular carcinoma. The contribution of the viral regulatory protein HBx in liver oncogenesis has been supported by our recent studies in a transgenic mouse model, showing that HBx cooperates with c-myc by accelerating the onset of primary liver tumors. Here we show that liver expression of HBx is associated with increased rates of spontaneous apoptosis in liver cells from two different transgenic lines. In transient transfection assays, overexpression of HBx in the established hepatocyte cell line MMHD3 and in human hepatoma cells HepG2 was found to induce apoptosis in a dose-dependent manner. These data suggest that HBx might trigger an apoptotic process in HBV-infected hepatocytes, in turn possibly favoring liver regeneration and accumulation of genetic alterations, ultimately leading to liver cell transformation in chronically infected patients.