PubMed Health⌕ Search

Biomedical subjects

J L Gerin

Publications and source records attributed to J L Gerin.

At least 19 recordsLinked to original sources
PubMed1992

Structural requirements for RNA editing in hepatitis delta virus: evidence for a uridine-to-cytidine editing mechanism.

Hepatitis delta virus (HDV) nucleotide 1012 is edited from uridine to cytidine in 10-40% of the RNA genomes during replication. This editing event is an important control point in the HDV life cycle because it results in both the packaging of viral RNA and the inhibition of HDV replication. We find that the editing event is highly specific for both the sequences neighboring nucleotide 1012 and the base-paired context of position 1012 within the unbranched rod structure of HDV RNA. Prior studies identified the base transition at nucleotide 1012 but were unable to distinguish between editing of the genomic versus the antigenomic strands [Luo, G. X., Chao, M., Hsieh, S. Y., Sureau, C., Nishikura, K. & Taylor, J. (1990) J. Virol. 64, 1021-1027]. In this study, comparisons of mutations that differentiate between base pairing in genomic and antigenomic RNAs indicate that the genomic strand of HDV is the actual editing substrate. We conclude that the virus uses a uridine to cytidine editing mechanism, which is provided by the host cell.

Animals↗
PubMed1992

Use of a standardized cell culture assay to assess activities of nucleoside analogs against hepatitis B virus replication.

A cell culture system for the evaluation of compounds which inhibit HBV replication (Korba and Milman, Antiviral Res. 15:217, 1991) has been developed into a standardized assay. Toxicity of test compounds was assessed by the uptake of neutral red dye under culture and treatment conditions which were identical to those used for the antiviral assays. A total of 667 separate cultures of 2.2.15 cells were evaluated for this study. In 86 untreated cell cultures, representing 15 experiments over a 24-month period, the levels of extracellular HBV virion DNA and intracellular HBV DNA forms were found to vary by less than 2.5-fold overall. Virion DNA in serum and intracellular viral DNA replication intermediates [RI] are the two most reliable and commonly followed markers of hepadnavirus replication in patients and experimental animals. In these assays, levels of extracellular HBV virion DNA and intracellular HBV RI were well correlated in 2.2.15 cells. Less correlation was observed between the levels of HBV virion DNA and the 3.2-kb episomal HBV genomes present in the cells. A threshold level of 22-37 intracellular replicating HBV genomes appeared to be required before virions were detected in the culture medium. The activities of several 2'-substituted and 3'-substituted deoxynucleoside analogs against HBV replication were compared using this standardized assay. Dideoxycytosine [ddC] and dideoxyguanosine [ddG] were the most selective 2',3'-dideoxynucleosides against HBV in 2.2.15 cells. Substitution of fluorine at the 2' position abolished the antiviral activity of ddC, but enhanced the selective antiviral activities of dideoxythymidine and dideoxyuracil. Several 2'-fluorinated pyrimidine arabinosyl furanosides, reported to be potent (but toxic) inhibitors of hepadnaviruses in vivo, demonstrated relatively low selective antiviral activities in 2.2.15 cells. The current data base allows for validation of any given set of test evaluations through statistical analysis of both the positive and the negative treatment controls present in each experiment; thus, relevant comparisons of the selectivity of anti-HBV activities for different compounds examined in future experiments can be made.

Antiviral Agents↗
PubMed1992

Altered glycosylation of alpha-fetoprotein in hepadnavirus-induced hepatocellular carcinoma of the woodchuck.

Altered glycosylation of alpha-fetoprotein (AFP) has been proposed as a marker of hepatocellular carcinoma (HCC) in humans. The lectin-binding properties of woodchuck AFP were investigated to determine if woodchuck hepatitis virus (WHV)-induced HCCs are also accompanied by changes in AFP glycosylation. Ninety-eight to 100% of the AFP from normal, WHV-free woodchucks with physiologic AFP elevations and from WHV-carrier woodchucks with HCC bound to concanavalin A, indicating that virtually all of the AFP was glycosylated. Three percent or less of the serum AFP of normal woodchucks bound to Lens culinaris agglutinin (LCA). In contrast, the AFP from woodchucks with HCC had an increased LCA-binding fraction (range, 8-77%). The increased LCA-binding AFP in WHV-induced HCC is analogous to that which frequently accompanies hepatitis B virus (HBV)-induced HCC in humans. This study corroborates the relationship of altered glycoconjugate synthesis to virus-induced malignant transformation, confirms the importance of AFP glycoforms as markers of HCC, and demonstrates that the WHV-infected woodchuck should be useful in investigating changes in AFP glycosylation during hepadnavirus hepatocarcinogenesis and HCC growth.

Animals↗
PubMed1992

Inactivated whole-virus vaccine derived from a proviral DNA clone of simian immunodeficiency virus induces high levels of neutralizing antibodies and confers protection against heterologous challenge.

We tested the ability of macaques vaccinated with inactivated whole simian immunodeficiency virus (SIV) to resist challenge with either homologous or heterologous cell-free uncloned SIV administered by the intravenous route. The vaccine virus was derived from a proviral DNA clone and thus was considered genetically homogeneous. Sixteen macaques received either hepatitis B surface antigen (n = 6) or the inactivated whole-SIV vaccine (n = 10) at weeks 0, 4, and 49 of the study. All SIV vaccine recipients developed high levels of homologous and heterologous neutralizing antibodies in response to vaccination. At the time of challenge (week 53), vaccinees were further stratified to receive either homologous (n = 10) or heterologous (n = 6) uncloned live SIV. The envelope glycoproteins of the homologous and heterologous challenge viruses were 94% and 81% identical to the vaccine virus, respectively. Regardless of challenge inoculum, all vaccinees in the control group (hepatitis B surface antigen) became infected, whereas all SIV vaccinees were protected against detectable infection. These data support the concept that an efficacious vaccine for HIV might be possible, and suggest that genetic variation of HIV might not be an insurmountable obstacle for vaccine development.

Animals↗
PubMed1992

Production of hepatitis B virus by stably transfected monocytic cell line U-937: a model for extrahepatic hepatitis B virus replication.

Human monocytic cell line U-937 was transfected with the hepatitis B virus (HBV) genome. Transfected cells releasing HBV surface antigen (HBsAg) and HBV e antigen (HBeAg) into the culture supernatant were cloned and further characterized. The HBV genomes were present in these cells in both chromosomally integrated and episomal forms. Intracellular replicative intermediates of HBV DNA and HBV-specific RNA transcripts of 3.6 and 2.2 kb were also detected. Viral DNA was present in the culture supernatant in viral particles with the buoyant densities of mature HBV virions. Electron microscopy revealed the presence of 22-nm spherical HBsAg particles, and Western blot analysis detected pre-S1 and -S2 antigens in particles in the culture supernatant. HBV DNA in U-937 cells was found to be positively regulated by corticosteroids, interleukin-1 beta, and transforming growth factor-1 beta. The stably transfected cell clones can be used to study HBV replication and its regulation in cells of bone marrow origin and to investigate the influence of HBV on the function of cells of the immune system.

Blotting, Northern↗
PubMed1992

Immunosuppression with cyclosporine during the incubation period of experimental woodchuck hepatitis virus infection increases the frequency of chronic infection in adult woodchucks.

The immunosuppressive agent cyclosporine was given to adult woodchucks during acute experimental infection with woodchuck hepatitis virus (WHV). All 17 woodchucks given WHV alone or with a vehicle resolved the infection (i.e., zero chronicity), but when cyclosporine was given throughout the incubation and acute phases of infection (0-12 or 14 weeks; n = 12), the rate of chronic infection increased to 92%. When cyclosporine was given only during the incubation period (0-4 weeks; n = 10) or only during the acute phase of infection (2-12 weeks; n = 9), the rates increased to 50% and 55%, respectively. However, when the drug was given after the acute phase (8-18 weeks; n = 9), the chronic infection rate (11%) did not differ from that in untreated and vehicle controls. Immune responses inhibited by cyclosporine are important in resolution of acute WHV infection and occur mainly during the first 8 weeks. Immunosuppression of these responses for even short intervals during incubation (e.g., 0-4 weeks) increases the risk of chronicity.

Animals↗
PubMed1992

The precore gene of the woodchuck hepatitis virus genome is not essential for viral replication in the natural host.

A number of naturally occurring hepatitis B virus mutants that cannot synthesize the virus precore protein have been identified. Such mutants have been associated with more severe forms of hepatitis, including fulminant hepatitis. The most common mutation observed is a substitution of G to A in the distal precore gene that converts a codon specifying Trp (TGG) to a termination codon (TAG). Using oligonucleotide-directed mutagenesis, we have produced the same point mutation in the precore gene of an infectious clone of woodchuck hepatitis virus (WHV). Transfection of mutant WHV DNA into the livers of adult woodchucks resulted in replication of the mutant in three of three susceptible animals. Levels of virus replication and transient elevations in liver enzymes in serum were similar to those of adult animals infected with wild-type WHV. Virions, found to possess mutant precore genes by polymerase chain reaction amplification and DNA sequencing, were recovered from the serum of one of the animals and inoculated subcutaneously into neonatal woodchucks. They produced infection in all five animals studied. The level of virus replication in neonatal animals infected with this mutant virus was comparable to that found in neonatal woodchucks infected with wild-type WHV, but none of five woodchucks infected with the precore mutant virus as neonates became chronic virus carriers. It was concluded that the precore gene of the WHV genome is not essential for virus replication in the natural host but may be important for chronic infection.

Animals↗
PubMed1992

Immunopathology of glomerulonephritis associated with chronic woodchuck hepatitis virus infection in woodchucks (Marmota monax).

Retrospective analysis of necropsy findings of 705 woodchucks was performed to determine the prevalence and morphology of immune-mediated glomerulonephritis, its relationship to woodchuck hepatitis virus (WHV) infection, and the presence of major WHV antigens. Twenty-six woodchucks had glomerular lesions. Renal tissue of the 26 animals was evaluated histologically and immunohistochemically for immune-mediated glomerulonephritis. Of these 26 animals, immune-mediated glomerulonephritis was diagnosed in six, all of which were chronic WHV carriers. Membranous glomerulonephritis was identified in three animals, two of which also had mesangial proliferation. Host immunoglobulin was present within the mesangium and along capillary loops in all three. Woodchuck hepatitis virus core antigen (WHcAg) was present along capillary loops of two of these animals, one membranous and one mixed, and in the mesangium of all three. Woodchuck hepatitis virus surface antigen (WHsAg) deposition was similar to WHcAg deposition but was only present along capillaries in those animals with mixed nephritis. The remaining three animals had mesangial proliferation. WHsAg and host immunoglobulin deposition were predominately mesangial; WHcAg was not detected. Transmission electron microscopy showed thickening of the capillary loop basement membranes and subepithelial electron-dense deposits in animal one, and deposits in the mesangium in animal six.

Animals↗
PubMed1991

Cyclosporin A modulates the course of woodchuck hepatitis virus infection and induces chronicity.

Immunosuppression is known to influence the state of chronic hepatitis B virus infection, and is thought to increase the risk of developing chronic infection in newly exposed individuals. Cyclosporin A (CsA), an immunosuppressive agent that inhibits Th cell function, was administered to woodchucks chronically infected with woodchuck hepatitis virus (WHV), and resulted in a decreased severity of chronic hepatitis and an increased viremia during the treatment. Adult woodchucks inoculated with WHV and given CsA for 14 wk had increased viremias, decreased acute phase liver injury, and developed chronic infections at a higher rate compared with immunocompetent woodchucks given virus alone (chronicity in seven of seven WHV + CsA + vs zero of nine WHV + CsA-; p less than 0.001). These results in a relevant animal model of hepatitis B virus infection indicate: 1) that liver injury in acute hepadnavirus infections is immune-mediated and not a direct cytopathic effect of virus replication; 2) that Th cells function in the inflammatory response and in the immunologic control of hepadnavirus infection; and 3) that suppression of Th cell function in acute hepadnavirus infection decreases liver injury but alters the outcome of infection in favor of chronicity. These results also suggest continued challenges in the application of CsA in liver transplantation for hepatitis B virus-induced diseases.

Acute Disease↗
PubMed1991

Attempts to transmit hepatitis B virus to chimpanzees by arthropods.

Bedbugs (Cimex lectularius L.) were fed on an infective blood-hepatitis B virus (HBV) mixture. Further bedbugs and tampan ticks (Ornithodoros moubata [Murray]) were fed on HBV-carrier chimpanzees. After a 10-13 day interval for oviposition, tests done on samples of individual arthropods showed that 53-85% of the bugs were HBsAg-positive and none HBeAg-positive, while 100% of the ticks were HBsAg-positive and 88% HBeAg-positive. The remaining arthropods were fed on 3 susceptible chimpanzees, which had failed to develop HBV infection after 11 months, indicating no transmission had occurred. Subsequently the presence of viable virus in the original infective meals was confirmed by inoculation of the relevant donor sera directly into the 3 still susceptible chimpanzees. HBV infections quickly followed in each animal. It is concluded that, while mechanical transmission of HBV is most unlikely after a 10-13-day interval between feedings in bedbugs and tampans, it is still possible that mechanical transmission between humans might occur during interrupted feeds.

Animals↗
PubMed1991

Hepatocellular carcinoma in Richardson's ground squirrels (Spermophilus richardsonii): evidence for association with hepatitis B-like virus infection.

During studies of seasonal obesity, a high frequency of hepatic neoplasms was observed in Richardson's ground squirrels. Of 12 Richardson's ground squirrels examined thoroughly, 7 had mild or moderate degrees of chronic portal hepatitis and 6 (50%) had hepatocellular carcinoma. Serological tests for hepadnavirus surface antigen, anti-core antibody and virion DNA that recognize the ground squirrel hepatitis virus of California ground squirrels (Spermophilus beecheyi) were uniformly negative. Southern blot analyses of EcoRI digests of liver cell DNA demonstrated 3.2 kb fragments that hybridized with a ground squirrel hepatitis virus-specific probe in nontumorous liver tissue from 6 of 10 ground squirrels and in hepatocellular carcinoma specimens from 2 of 5 squirrels indicating infection with a hepadnavirus related to ground squirrel hepatitis virus. Failure, however, to detect serum antibody to ground squirrel hepatitis core antigen suggested probable antigenic differences between the ground squirrel hepatitis virus of California ground squirrels and the putative Richardson's ground squirrel agent. Further studies are required to fully characterize the hepadnavirus of Richardson's ground squirrels and to determine its relationship to hepatocarcinogenesis in this species.

Animals↗