published_or_final_version / Medicine / Master / Doctor of Medicine

Hepatitis B virus (HBV) causes an estimated 600,000 deaths annually, largely due to hepatocellular carcinoma (HCC). HBx, a promiscuous transactivator, is a viral oncoprotein, but its exact functions are poorly understood. Many studies have suggested that NF-κB signaling mediates HBx functions, but the underlying molecular mechanisms remain yet to be elucidated. Here, we provide evidence that HBx-mediated NF-κB activation depends on the physical interaction between HBx and a transcription factor, p65. In the cytoplasm, HBx-p65 interaction may promote IκBα phosphorylation and subsequent p65 nuclear localization. A cytokine assay using qPCR and RT-PCR indicates that HBx is associated with a unique profile of cytokine mRNA expression. As shown by chromatin immunoprecipitation (ChIP), HBx in the nuclues can be recruited to the gene promoter by p65. These findings support the importance of HBx-p65 interaction and suggest that it is potentially a promising target of novel therapeutics for HBV-associated liver diseases, including HCC.

Background: Chronic HBV within the Canadian Arctic is considered endemic (>2% prevalence). To control endemic rates in Nunavut, a vaccination program was initiated approximately 20 years ago, targeted at newborns and grade school students, as an interim catch-up program, such that all individuals born after 1980 are potentially vaccinated. This study investigates the efficacy of these programs and is the first seroepidemiological survey to determine HBV prevalence in Nunavut in the post-vaccination era. Methods: Anonymized serum specimens scheduled for destruction following routine medical testing were collected from individuals granting consent. Specimens were tested for antibodies to HBV (anti-HBs, anti-HBc) and hepatitis C virus. Anti-HBc positive samples were further tested for surface antigen (HBsAg) positivity, and HBV DNA was extracted from HBsAg positive samples in order to perform molecular characterization. Results: 4802 specimens were collected according to the age distribution of Nunavut, with vaccine age cohort specimens comprising just over half of all collected specimens. Overall anti-HCV+ was 0.55%, with all positivity observed among those aged 24 to 69 years old. Total anti-HBc+ prevalence was 9.40%; however, a 10-fold decrease in the rate of HBV exposure was noted among those born after 1980 compared to those born before (1.89% vs 20.1%, p<0.001). HBsAg positivity was primarily documented in individuals born before 1980 (2.55%), although cases still occurred among the vaccine age cohort (0.21%). HBV subgenotype B5 (HBV/B5), known to be unique among Inuit and Alaska Native people, was the most prevalent genotype observed (82%). Vaccine-based antibody as the sole serological marker was evident in the vaccine age cohort, although the rate of decay with increasing age was much greater than anticipated. Conclusion: Nearly two decades after the advent of HBV vaccination in Nunavut, HBV prevalence has decreased to 1.17%, indicating a non-endemic or low risk prevalence. However, the persistence of infection and a lower than expected prevalence of vaccine-based immunity in the vaccine age cohort will require further investigation to understand the causes and consequences.

This thesis investigates the epidemiology of hepatitis B virus infection (HBV) and estimates HBV-related liver disease burden in Vietnam and Australia using a cross-sectional study design and mathematical modelling. A population-based seroprevalence survey was undertaken in rural Northern Vietnam. In a sample of 870 study participants, prevalence of anti-HBV core antibody (anti-HBc) and hepatitis B virus surface antigen (HBsAg) was 68.2% and 19.0%, respectively, and hepatitis B e antigen (HBeAg) was detected in 16.4% of the HBsAg-positive group. Factors associated with HBV infection (anti-HBc and/or HBsAg-positive) were age 60 years or older (adjusted odds ratio (AOR), 3.82; 95% CI, 1.35??10.80; P = 0.01), residence in Vu Thu district (AOR, 3.00; 95% CI, 2.16??4.17; P <0.001), hospital admission (AOR, 2.34; 95% CI, 1.33??4.13; P = 0.003) and history of acupuncture (AOR, 2.01; 95% CI, 1.29??3.13; P = 0.002). Household contact with a person with liver disease (AOR, 2.13; 95% CI, 1.29??3.52; P = 0.003), reuse of syringes (AOR, 1.81; 95% CI, 1.25??2.62; P = 0.002) and sharing of razors (AOR, 1.69; 95% CI, 1.03??2.79; P = 0.04) were independent predictors of HBsAg positivity. Alanine aminotransferase (ALT) level was elevated (>40 IU/L) in 43% of the HBsAg-positive group; the proportion of elevated ALT was higher in HBeAg-positive (65%) compared with HBeAg-negative (39%) (P = 0.02). Based on data from the seroprevalence study, other prevalence estimates and HBV natural history parameters, a mathematical model was used to estimate HBV-related liver disease burden in Vietnam. Estimated chronic HBV prevalence increased from 6.4 million cases in 1990 to around 8.4 million cases in 2005 and was projected to decrease to 8.0 million by 2025. Estimated HBV-related liver cirrhosis and hepatocellular carcinoma (HCC) incidence increased linearly from 21 900 and 9400 in 1990 to 58 650 and 25 000 in 2025. Estimated HBV-related mortality increased from 12 600 in 1990 to 40 000 in 2025. To estimate HBV-related HCC incidence among Australians born in the Asia-Pacific region (APR), a mathematical modelling was developed utilising HBV natural history parameters, HBV prevalence estimates in APR countries and immigration data. Chronic HBV cases among the APR-born population increased rapidly from the late 1970s, reaching a peak of 4182 in 1990. Chronic HBV prevalence increased to more than 53 000 in 2005. Estimates of HBV-related HCC increased linearly from one in 1960 to 140 in 2005, with a projected increase to 250 in 2025. Universal HBV vaccination programs in countries of origin had limited impact on projected HBV-related HCC to 2025. HBV-related HCC survival was analysed in a population-based linkage study in New South Wales (NSW), Australia. Between 1994 and 2002, 278 HCC cases notified to the NSW Cancer Registry were linked to chronic HBV infection notifications to the NSW Health Department. The majority of cases were male (83.5%) and overseas born (93.6%); Asian-born cases accounted for 72.1%. Median survival following HCC diagnosis was 15 months. HCC survival was poorer among older age groups (P <0.001), and among cases with regional spread (HR 3.23; 95% CI, 1.83??5.69; P <0.001) and distant metastases (HR 3.85; 95% CI, 2.44??6.08; P <0.001). Sex, region of birth, and study period (1994??1997 versus 1998??2002) were not associated with HCC survival. The results of these studies show that HBV infection remains a major public health challenge in highly endemic countries such as Vietnam. HBV-related liver disease burden in Vietnam was estimated to increase for at least two decades despite the introduction of a universal infant HBV-vaccination program. Similarly, HBV-related HCC among Australians born in the APR was estimated to continue to increase over the next two decades. Survival for HBV-related HCC even in settings such as Australia continues to be extremely poor. Strategies are required to expand HBV treatment to individuals with chronic HBV infection who are at greatest risk of progression to advanced liver disease.

Bibliography: leaves 184-218. / xx, 218, [135] leaves, [15] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The research in this thesis describes the development and use of assays to detect cellular immune responses in ducks with application to duck hepatitis B virus (DHBV) infections. This animal model is used to provide an additional area of research which complements the study of hepadnaviruses. The introduction contains an outline of the significance of hepadnavirus research, including hepatitis B virus (HBV) epidemiology, structure, replication and clinical manifestations of the diseases caused by the virus. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1997

Hepatitis B virus (HBV) is a global public health problem with an estimated number of 350 million carriers world wide who are at risk of development of severe liver disease and hepatocellular carcinoma. Despite currently available nucleoside analogue therapies no general therapeutic breakthrough, which completely clears infection has been achieved after more then two decades of research. Therefore there is a continuing need to identify new antiviral targets that may be translated into useful therapies. / Hepatitis B fusion represents a possible novel antiviral target. However, its mechanism and the envelope proteins involved remain unknown, due to the lack of an efficient infection system to study the early stages of virus infection. On the other hand, the study of the related duck hepatitis B virus (DHBV) and the ability to carry out an in vitro infection of primary duck hepatocytes has provided some insight into the hepadnaviral mechanism of entry and the role of envelope proteins domains in this process. ( For complete abstract open document)

Bibliography: leaves 184-218. / xx, 218, [135] leaves, [15] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The research in this thesis describes the development and use of assays to detect cellular immune responses in ducks with application to duck hepatitis B virus (DHBV) infections. This animal model is used to provide an additional area of research which complements the study of hepadnaviruses. The introduction contains an outline of the significance of hepadnavirus research, including hepatitis B virus (HBV) epidemiology, structure, replication and clinical manifestations of the diseases caused by the virus. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology and Immunology, 1997

Improved methods for the in situ hybridisation detection of messenger RNA ( mRNA ) in sections of liver tissue, were derived by use of an experimental system. This involved the use of tritiated-poly ( dT ) probes to detect poly ( A ) sequences attached to the 3 ' end of mRNA in sections of mouse liver that had been processed in various ways. The improved - methods were applied to the detection of hepatitis B virus ( HBV ) - and hepatitis delta virus ( HDV ) - RNA. In situ hybridisation and immunostaining techniques were then applied to studies of the pathogenesis of HBV and duck hepatitis B virus ( DHBV ) infection. In situ hybridisation studies of liver biopsy tissue from HBV - infected immunosuppressed renal transplant patients demonstrated an anatomical association between piecemeal necrosis and HBV replication at the cellular level in some patients. However, widespread replicative infection of hepatocytes also occurred in some patients in the presence of normal hepatocyte morphology and mild inflammatory changes indicating that at the cellular level virus replication was not necessarily a direct cytopathic process. These findings supported the view that hepatocyte Injury may : ( i ) result from immune - mediated damage directed against cells undergoing replicative, but not restricted infection ; ( ii ) eliminate cells undergoing replicative infection and favour clonal regeneration of cells undergoing restricted infection. Localisation of interferon - alpha ( IFN - alpha ) expression in liver tissue chronically infected with HBV and HDV, identified mononuclear cells and fibroblasts ( but not hepatocytes ) as the main producers of IFN - alpha. IFN - alpha - positive cells were associated with areas of liver tissue containing cells supporting virus replication and exhibiting the greatest degree of liver damage, suggesting that locally produced IFN - alpha may be a natural regulator of virus replication in chronic liver disease. Experimental DHBV infection of Pekin - Aylesbury ducks showed that virus inoculated either intravenously or intraperitoneally, gained access to randomly distributed hepatocytes without first replicating in other cell types in the liver. Virus was seen to disseminate to contiguous cells following anatomical boundaries by the third day post - inoculation. Markers of DHBV infection in liver and serum showed reproducible kinetics, and duck hepatocytes in this system appeared to be highly permissive as large amounts of DHBV DNA and DHBsAg were produced intracellularly without the development of ongoing cytopathology. Hepatocytes were the major cell type responsible for early significant DHBV replication, in contrast to pancreas, kidney, spleen and circulating mononuclear cells where significant levels of infection were detected only after the first week of infection and the onset of viraemia. / Thesis (Ph.D.)--Department of Microbiology and Immunology, 1989.

This research investigated a number of issues regarding hepatitis B virus (HBV) in the silvery gibbon (Hylobates moloch). Due to the relatively recent discovery of the virus in nonhuman primate populations, specific knowledge of the biological behaviour of the virus is presently lacking, with current information largely extrapolated from the behaviour of HBV in human infections. In order to manage the captive and wild populations of this critically endangered species, information regarding the behaviour of the virus in gibbons and the likely impact of the viral infection is essential. The research was performed at Perth Zoo, with the study population consisting of the current and historical members of the zoo’s silvery gibbon colony. Because this gibbon species is critically endangered, the study was conducted with minimal intervention to the population with samples collected largely on an opportunistic basis from a small study population. Review of the history of the virus within the Perth Zoo colony provided epidemiological evidence to indicate vertical transmission in three gibbons (Hecla, Uban and Jury). It would appear that vertical transmission is the primary mode of transmission leading to dispersal of the virus through the captive population of silvery gibbons. Elevated concentrations of the liver enzymes alanine aminotransferase and aspartate aminotransferase were found in three gibbons (Perth 2, Uban and Jury), and may suggest a pathogenic role of the virus in this species. Histological examination of the livers of Uban and Perth 2 failed to demonstrate definitive evidence of cirrhosis, however mild fibrosis was seen in both cases and may represent an early stage of liver pathology associated with chronic hepatitis B infection. The vaccination protocol developed at Perth Zoo was successful in preventing neonatal transmission of the virus from a high infectivity carrier mother in at least two individuals, and was also successful in producing a protective level of immunity against the virus in all three of the individuals tested. Sequencing of the complete hepatitis B genome from one gibbon (Hecla) revealed that she was infected with GiHV (Gibbon hepatitis B virus), an indigenous strain of HBV previously identified in a number of gibbon species, but not previously confirmed in the silvery gibbon. Hecla's strain of HBV was shown to be more closely related to other nonhuman primate strains of HBV than to any of the human strains of HBV. 100% nucleotide similarity to two of Hecla’s siblings indicates that infection in all three animals was the result of vertical transmission from their mother. Partial sequencing of the virus from a second gibbon (Uban) identified another strain of GiHBV which supports the results of the epidemiological study. Neither gibbon showed a high sequence similarity to the virus sequenced from Ivan, the father of the third carrier gibbon (Jury), although only limited sequence data was available from Ivan. Consequently it is likely that at least three different strains of GiHBV are present within the silvery gibbon population. The information contained in this thesis will assist in the understanding and management of hepatitis B infection in silvery gibbons, as well as the numerous other species of nonhuman primates now shown to be susceptible to this virus.

Thesis (Ph.D.)--University of Melbourne, Dept. of Microbiology and Immunology, The Macfarlane Burnet Institute for Medical Research and Public Health, 2006. / Typescript. Includes bibliographical references (leaves 155-177).