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S Bowden

Publications and source records attributed to S Bowden.

At least 19 recordsLinked to original sources
PubMed2006

A 2a/1b full-length p7 inter-genotypic chimeric genome of hepatitis C virus is infectious in vitro.

The p7 protein of hepatitis C virus (HCV) functions as an ion channel in planar lipid bilayers, and its function is vital for the virus life cycle. In this study, we replaced either the entire or partial p7 of genotype 2a (strain JFH1), an HCV strain that replicates and produces virus progeny in vitro, with the corresponding regions of the p7 protein from genotype 1b (Australian isolate, HCV-A). Compared to wild type, the chimeric viruses reached their peak of infectivity with a delay but they produced a comparable titer to the wild type virus and the progeny viruses were able to infect naive permissive cells. Amantadine treatment of wild type and chimeric viruses reduced the virus titers by about 50% and 45%, respectively. Therefore, in this study, for the first time, we demonstrated that genotype 2a (JFH1 strain) genome encoding a full-length genotype 1b p7 gene produces infectious particles in vitro. These chimeric viruses are valuable instruments for comparative studies of the p7 proteins.

Amantadine↗
PubMed2005

Detection of multiple hepatitis C virus genotypes in a cohort of injecting drug users.

Multiple genotypes of the hepatitis C virus (HCV) were detected in five of 138 HCV RNA positive injecting drug users (IDUs) recruited in Melbourne, Australia. Two were detected by combined LiPA and core and NS5a region sequencing, and three more (selected for testing due to their high-risk behaviour) by heteroduplex mobility analysis. We conclude that the true prevalence of mixed infection in IDUs is undoubtedly higher than the 3.6% (five of 138) we observed, and is underestimated by LiPA, the most common method of genotyping. As responsiveness to HCV treatment varies significantly with genotype, a high prevalence of mixed HCV infections in IDUs must diminish overall treatment efficacy and lessen our ability to reduce the burden of HCV-related disease.

Australia↗
PubMed2003

Induction interferon and ribavirin for re-treatment of chronic hepatitis C patients unresponsive to interferon alone.

BACKGROUND: The optimal treatment for hepatitis C patients unresponsive to interferon is unclear. High-dose induction interferon may enhance early viral clearance, whilst ribavirin reduces relapse; in combination, they may improve sustained virological response rates. AIM: To compare the efficacy and safety of re-treatment with interferon induction, with or without ribavirin, in interferon non-responders. METHODS: We randomized 218 biochemical interferon non-responders to 10 MU interferon alpha 2b daily for 4 weeks, followed by 5 MU thrice weekly for 48 weeks plus ribavirin (II + R), or to the same interferon regimen plus placebo (II + P). All patients were viraemic at entry. RESULTS: The sustained virological response in the II + R group was 39%[95% confidence interval (CI), 30-48%], compared with 16% (95% CI, 9-23%) in the II + P group (P < 0.002). The study drug was discontinued for intolerable symptoms during induction in 9% of the II + R group and in 5% of the II + P group. By logistic regression, a sustained virological response was more likely following II + R treatment (odds ratio, 4.4; 95% CI, 2.1-9.7) and less likely in patients with genotype 1 or 4 (odds ratio, 0.16; 95% CI, 0.07-0.36). CONCLUSION: High-dose induction interferon plus ribavirin is well tolerated and effective for patients unresponsive to interferon alone.

Adolescent↗
PubMed2001

New hepatitis viruses: contenders and pretenders.

Following the development of tests for hepatitis C virus and hepatitis E virus infection, it became clear that there remained cases of hepatitis that were non-A-E. Such cases provided impetus for the search for additional hepatitis viruses and, by using molecular techniques, several candidates were identified. An enteric agent responsible for sporadic non-A and non-E hepatitis was tentatively called hepatitis F virus. However, the lack of any corroborating reports has cast doubt on its status as a true hepatitis virus. Two groups independently reported the isolation of a blood-borne virus, designated as hepatitis G virus (HGV) and GB virus C (GBV-C) by their respective discoverers. They were later shown to be isolates of the same virus. While the virus has a high prevalence in cases of non-A-E hepatitis, it also has a high prevalence in the appropriate control groups and convincing evidence for its replication in the liver is lacking. Another possible hepatitis virus, TT virus, was discovered in the blood of a patient with post-transfusion non-A-E hepatitis. By using PCR primers designed to overcome the high nucleotide sequence divergence, TT virus was found to be ubiquitous with a worldwide distribution. A disease association is thus unlikely. Most recently, a DNA virus designated as SEN-V has been announced as a major cause of non-A-E hepatitis. Based on limited data available to researchers, SEN-V is the most convincing contender for the new hepatitis virus title. However, the lessons learnt from the hepatitis virus pretenders will need to be applied to SEN-V and any future contenders.

Animals↗
PubMed2001

Analysis of hepatitis B viral load decline under potent therapy: complex decay profiles observed.

We used a new real-time polymerase chain reaction (PCR)-based assay that is sensitive, has a wide dynamic linear range, and is highly reproducible to quantify hepatitis B virus (HBV) DNA in the serum of infected individuals undergoing potent antiviral therapy. In addition, we made frequent measurements of viral load after initiation of treatment and maintained follow-up to about 12 weeks. To analyze the data we used a new model of HBV decay, which takes into account that existing drug treatments do not completely block de novo infection and the possibility of noncytolytic loss of infected cells. On initiation of therapy, there was a mean delay of 1.6 days followed by a biphasic or muliphasic decay of plasma HBV DNA. The slope of the first phase varied considerably, with one individual having rapid decay, corresponding to a virion half-life of 1 hour, but others showing half-lives of up to 92 hours. Individuals either had a slow second-phase decline (t((1/2)) = 7.2 +/- 1.2 days) or a flat second phase. Some individuals exhibited a complex "staircase pattern" of decay, with further phases of viral DNA decline and phases with little change in viral load.

2-Aminopurine↗
PubMed2000

Assessment of long-term outcomes of community-acquired hepatitis C infection in a cohort with sera stored from 1971 to 1975.

The aim of this study was to examine the long-term effects of hepatitis C virus (HCV) infection on a cohort of patients admitted with acute viral hepatitis from 1971 through 1975. The availability of stored sera from this time enabled testing to identify those who were anti-HCV-positive on admission. Sixteen percent (n = 238) of the cohort tested anti-HCV-positive. The unexposed group was selected from those who were anti-HCV-negative. Systematic approaches were used to locate the cohort and health outcomes assessed by a study-specific questionnaire and clinical, serological, virological, and biochemical assessment. Complete follow-up was achieved on 98 anti-HCV-positive individuals and 201 negatives. Injecting drug use (IDU) was the presumed route of infection. At a mean of 25 years' follow-up, 54% of the anti-HCV-positive group had evidence of chronic HCV infection (both anti-HCV- and HCV-RNA-positive); the remainder were HCV-RNA-negative. Sixty-nine percent of those chronically infected had elevated serum alanine transaminase (ALT) levels, but only 8% had progressed to overt cirrhosis, and no cases of hepatocellular carcinoma (HCC) were identified. In summary, anti-HCV-positive subjects were 8 times more likely to have died from suicide or drug overdose than from HCV-related disease. Anti-HCV-positive study subjects were at increased risk of liver-related pathology after 25 years' follow-up, but few had progressed to overt cirrhotic liver disease. Excess mortality in this group was not the result of liver disease. This suggests that the natural history of community-acquired HCV may be more benign than previously thought.

Adult↗
PubMed1999

Lamivudine therapy in patients undergoing liver transplantation for hepatitis B virus precore mutant-associated infection: high resistance rates in treatment of recurrence but universal prevention if used as prophylaxis with very low dose hepatitis B immune globulin.

Recurrent hepatitis B virus (HBV) infection remains a major cause of morbidity and mortality after liver transplantation. Recently, antiviral therapy, such as lamivudine, has become available for prophylaxis against HBV reactivation posttransplantation and for the treatment of HBV recurrent disease. We report our initial experience with lamivudine therapy in patients with precore mutant-associated HBV infection undergoing liver transplantation (n = 29). Outcomes were compared in three patient groups: group 1, precore mutant HBV infection not receiving lamivudine (n = 10); group 2, recurrent precore mutant HBV infection posttransplantation subsequently treated with lamivudine (n = 10); and group 3, HBV precore mutant patients undergoing liver transplantation and receiving lamivudine and low-dose hepatitis B immune globulin (HBIG) from the time of transplantation (n = 9). In group 1, HBV recurred in 9 of 10 patients, with subsequent graft loss in all 9 patients. In group 2, all patients developed HBV recurrence at a mean of 7.3 months posttransplantation and started lamivudine therapy at a median of 16 months posttransplantation. Follow-up on lamivudine therapy was for a median of 11 months. Six of these 10 patients developed mutations in the HBV polymerase gene associated with lamivudine resistance. There were two liver failure-related deaths in this group. In group 3 patients, there was one death from graft-versus-host disease. The remaining 8 patients have been followed up for a mean of 15.6 months posttransplantation, and all remain hepatitis B surface antigen negative and HBV DNA negative. In conclusion, lamivudine therapy in association with low-dose HBIG is effective in preventing HBV reactivation posttransplantation. Rescue therapy with lamivudine in patients with HBV recurrence is only moderately effective, with a 60% lamivudine resistance rate in patients treated for longer than 6 months.

Adult↗
PubMed1997

Hepatitis B virus polymerase mutations during antiviral therapy in a patient following liver transplantation.

BACKGROUND/AIMS: The purpose of this study was to investigate possible resistance mutations which arose in the polymerase gene of hepatitis B virus (HBV) in a patient with severe recurrent HBV infection following liver transplantation. The patient's management included antiviral chemotherapy for almost 4 years comprising ganciclovir, foscarnet and famciclovir. In the last 2.5 years of famciclovir treatment, an increase in serum HBV DNA levels and a reduced sensitivity of the virion-associated DNA polymerase to penciclovir triphosphate were observed. METHODS: The viral polymerase gene and X gene were sequenced from serum samples collected at representative time intervals covering the entire treatment period. RESULTS: No mutations were detected in the X gene. Three nucleotide mutations, each of which resulted in an altered amino acid sequence, were detected in the polymerase gene after 816 days of total antiviral therapy (370 days of famciclovir). Two of these mutations were detected by direct sequencing and the third was detected after cloning and was present in 10% of the clones. All three mutations occurred in "region B" of RNA-dependent DNA polymerases. The HBV polymerase has similarities to both RNA and DNA polymerases. These mutations in the HBV polymerase gene were located in a similar area to the penciclovir-induced mutations observed in the herpes simplex virus DNA polymerase gene. CONCLUSIONS: Three mutations within the HBV polymerase gene were detected which were associated with a reduced penciclovir sensitivity.

2-Aminopurine↗
PubMed1996

Retransplantation for precore mutant-related chronic hepatitis B infection: prolonged survival in a patient receiving sequential ganciclovir/famciclovir therapy.

Retransplantation for hepatitis B-related liver allograft failure is rarely successful. Recurrence of infection is almost universal, and the second allograft is invariably lost more rapidly than the first. In a recent multicenter study, only 1 of 20 hepatitis B virus (HBV)-positive patients who underwent liver retransplantation survived beyond 6 months. This report describes the long-term effect of antiviral therapy in a 56-year-old man who was retransplanted for HBV-related allograft loss 14 months after his initial liver transplant. He was treated after the second transplant with intravenous daily ganciclovir. After 10 months of this therapy HBV recurrence was detected. After a change to oral famciclovir therapy, there was a decrease in serum HBV DNA and amino-transferase levels and an improvement in the patient's clinical condition. Famiciclovir therapy has now been continued for 26 months, and the patient remains well 3 years after his second transplant, despite persistent HBV infection and progression to cirrhosis. These observations indicate that the use of long-term antiviral therapy offers promise for improving outcomes in patients who undergo retransplantation after HBV-related liver allograft failure.

2-Aminopurine↗
PubMed1995

Reversion of duck hepatitis B virus DNA replication in vivo following cessation of treatment with the nucleoside analogue ganciclovir.

In order to define, in more detail, the virological events which occur after completion of antiviral chemotherapy, ducks congenitally infected with the duck hepatitis B virus (DHBV) were treated for 4 weeks with the nucleoside analogue ganciclovir and followed up over a 7-day period. Specimens of serum and liver were collected daily during follow-up for virological analysis. Treatment resulted in a substantial reduction in both viraemia and liver DHBV DNA replicative intermediates. However, after cessation of treatment, viraemia returned to detectable levels within 4 days. In the liver, the viral supercoiled DNA (SC DNA) was the form least affected by therapy and returned to near control levels by day 2 post-treatment. The other hepatic replicative intermediates reached pretreatment levels within 4 days of cessation of therapy. This study has defined the kinetics of relapse of viral replication after completion of antiviral therapy in the duck hepatitis B model. Of all viral replicative forms, the SC DNA appears to be the one which is most resistant to nucleoside analogue therapy and is presumably responsible for the relapse phenomenon observed post-treatment.

Animals↗
PubMed1995

Inhibition of duck hepatitis B virus DNA replication by antiviral chemotherapy with ganciclovir-nalidixic acid.

The aim of this study was to examine the effects of ganciclovir and nalidixic acid either alone or in combination on duck hepatitis B virus DNA replication in vivo with particular reference to production of viral supercoiled DNA and RNA. The most effective antiviral response was observed in the livers of ducks treated by the combination therapy for 28 days, which resulted in a substantial decrease in the amounts of viral supercoiled DNA, relaxed circular and single-stranded DNA, and also viral RNA. This combination treatment was not hepatotoxic over the study period.

Animals↗
PubMed1995

The covalently closed duplex form of the hepadnavirus genome exists in situ as a heterogeneous population of viral minichromosomes.

Replication of hepadnaviruses requires a persistent population of covalently closed circular (CCC) DNA molecules in the nucleus of the infected cell. It is widely accepted that the vital role of this molecule is to be the sole DNA template for the synthesis by RNA polymerase II of all viral transcripts throughout the infection process. Since the transcriptional activity of eukaryotic nuclear DNA is considered to be determined in part by its specific organization as chromatin, the nucleoprotein disposition of the hepadnavirus CCC DNA was investigated. These studies were undertaken on the duck hepatitis B virus (DHBV) CCC DNA present in the liver cell nuclei of DHBV-infected ducks. The organization and protein associations of the DHBV CCC DNA in situ were inferred from sedimentation, micrococcal nuclease digestion, and DNA superhelicity analyses. These three lines of investigation demonstrate that the DHBV CCC DNA is stably associated with proteins in the nuclei of infected liver cells. Moreover, they provide compelling evidence that the viral nucleoprotein complex is indeed a minichromosome composed of classical nucleosomes but in arrays that are atypical for chromatin. When the DHBV chromatin is digested with micrococcal nuclease, a ladder of viral DNA fragments that exhibits a 150-bp repeat is produced. This profile for the viral chromatin is obtained from the same nuclei in which the duck chromatin shows the standard 200-bp ladder. The superhelicity of the DHBV CCC DNA ranges from 0 to 20 negative supertwists per molecule, with all possible 21 topoisomers present in each DNA preparation. The 21 topoisomers of DHBV CCC DNA are inferred to derive from an identically diverse array of viral minichromosomes. In the DHBV minichromosomes composed of 20 nucleosomes, 96.7% of the viral DNA is calculated to be compacted into these chromatin subunits spaced on average by 5 bp of linker DNA; other minichromosomes contain fewer nucleosomes and proportionately more linker DNA. Two major subpopulations of DHBV minichromosomes are detected with comparable prevalence. The two groups correspond to minichromosomes which contain essentially a full or half complement of nucleosomes. The functional significance of this minichromosome diversity is unknown but is suggestive of transcriptional regulation of the viral DNA template.

Animals↗
PubMed1994

The role of Raf-1 in the regulation of extracellular signal-regulated kinase 2 by the T cell antigen receptor.

Triggering of the T cell antigen receptor (TCR) complex activates the serine/threonine kinase Raf-1 whose function is necessary for TCR induction of the interleukin 2 gene. Raf-1 has been identified as a candidate mitogen-activated protein (MAP) kinase kinase kinase (MKKK) and thus has the potential to couple the TCR to the activation of the MAP kinases such as ERK2. In the present study, the role of Raf-1 in ERK2 regulation of ERK2 in T cells has been explored. A constitutively active Raf-1 kinase, v-raf, or a dominant inhibitory Raf-1 mutant were expressed transiently from the pEF BOS vector in Jurkat cells and the effects of these Raf-1 mutants on a coexpressed ERK2 reporter was assessed. The action of the constitutively active Raf-1 was to stimulate the ERK2 kinase, whereas the dominant negative version of Raf-1 inhibited the ERK2 activation induced by triggering of the TCR. These data indicate a role for Raf-1 in the regulation of ERK2 in T cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1994

Detection of hepatitis B virus DNA in tears by polymerase chain reaction.

OBJECTIVE: To assess the possibility of transmission of hepatitis B virus (HBV) via tears. METHODS: Tear and plasma specimens were collected from 36 carriers of HBV, and the presence of HBV DNA was investigated using the polymerase chain reaction (PCR). RESULTS: Ten (29.4%) of the 34 carriers of chronic HBV and one of the two patients with acute hepatitis B had plasma specimens that were positive for HBV DNA using PCR. Sixteen (47.1%) of the 34 carriers of chronic HBV had tear specimens that were repeatedly positive for HBV DNA using PCR, 10 (29.4%) had tear specimens that were repeatedly negative, and the remaining eight (23.5%) had tear specimens that were equivocal. Both of the patients with acute hepatitis B had tear specimens that were positive for HBV DNA using PCR. CONCLUSION: Hepatitis B virus DNA can be demonstrated in the tears of carriers, even those who were asymptomatic.

Base Sequence↗