Thesis (M.D.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 239-283) Also available in print.

Mainz, Univ., Diss., 2001.

The purpose of this study was to identify mutations in the basic core promoter and enhancer II region a* the hepatitis B virus (HBV) that might result in the hepatitis B virus e antigen (HBeAg)-negative phenotype and contribute to hepatocarcinogenesis in black African carriers of the virus. The basic core promoter/enhancer II overlaps the X gene. HBV DNAfrom serum of 47 asymptomatic carriers and 50 patients with hepatocellular carcinoma and from 29 tumorous and 10 nontumorous liver tissues was amplified and sequenced directly. That part of the enhancer II region not overlapping the basic core promoter was reasonably well conserved in all samples. Missense mutations at positions 1809 and 1812 were found in 80% of all sequences and may represent wiidtype sequence in southern African isolates. Nucleotide and amino acid divergences were higher in the basic core promoter of hepatocellular carcinoma patients than of asymptomatic carriers (p<0.0001). This applied particularly to the paired 1762 adenine to thymine (1762T) and 1764 guanine to adenine (1764*) missense mutations, the prevalence of which was 66% in patients with hepatocellular carcinoma compared with 11% in asymptomatic carriers (p<0.0001). There was no association between the presence of 1762T1764A and the rate of HBeAg negativity, although these mutations suppressed HBeAg titres in HBeAg-positive patients. Suppression of HBeAg expression as well as alteration of amino acid sequence of the X protein may be contributing factors in the development of hepatocarcinogenesis.

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Medicine Johannesburg, 2017 / Hepatitis B is a global health problem that kills about 600 000 people annually. It is an infectious disease caused by the Hepatitis B Virus (HBV), which infects the liver and leads to liver inflammation and secondary complications such as cirrhosis and Hepatocellular Carcinoma (HCC). The available therapies are only partially effective and are associated with adverse side effects and viral drug resistance. RNA interference (RNAi) pathway is a gene silencing pathway found in diverse living systems including mammals. Harnessing of this pathway to inhibit HBV replication has shown a lot of promise, with highly effective anti-HBV RNAi activator sequences designed. However, the lack of safe and efficient delivery and expression systems for these sequences is one of the obstacles that need to be overcome before RNAi effectors can reach clinical application. For easy assessment of transduction efficiency, Helper Dependent Adenoviral vectors (HDAd) expressing β-galactosidase (encoded by lac Z gene) are commonly used to deliver anti-viral RNAi activators. However, this reporter protein has been blamed for induction of innate immune response and concomitant clearance of the HDAds by the host. For the first time, this study explored the use of lac Z-deficient HDAds to deliver anti-HBV RNAi activators expressed under the control of a liver-specific phosphoenolpyruvate carboxykinase (PEPCK) promoter. HDAd expressing Firefly luciferase resulted in a significant luminescence detected in cell culture lysates and a sustained bioluminescence in mice. HDAds expressing anti-HBV sequences transduced the liver efficiently and did not induce a pronounced inflammatory response or liver toxicity in mice. However, this did not translate into maximal anti-HBV sequence expression and HBV replication inhibition in vitro and in vivo. This suggests that the PEPCK promoter is inadequate for RNAi activator expression. This study highlights the importance of careful RNAi activator regulatory elements selection and presents the therapeutic potential and utility of HDAd vectors for hepatotropic delivery of antiviral sequences with markedly attenuated immune response stimulation and toxicity. For improved anti-HBV RNAi activator expression and HBV knockdown, a different liver specific promoter mouse transthyretin receptor (MTTR) promoter is currently being investigated in our lab. / MT2017

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, 2002 / Hepatitis B virus (HBV) infection is endemic to several populous regions and is often complicated by cirrhosis and hepatocellular carcinoma (HCC). Present treatment of chronic HBV infection is usually ineffective and novel therapeutic approaches are an important medical objective. The X open reading frame (ORF) of HBV, HBx, is a conserved sequence that overlaps with the polymerase ORF and viral c/'s-elements, and is present within all viral transcripts. In addition, the HBx ORF encodes a 17 kDa transactivator protein, HBx, which is required for the establishment of viral infection and has been implicated in HBV-associated hepatocarcinogenesis. The HBx sequence thus represents a compelling target for applying nucleic acid hybridisation-based therapeutic agents for the inhibition of HBV gene expression and replication. / IT2018

Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 221-251.

published_or_final_version / abstract / Microbiology / Doctoral / Doctor of Philosophy

ABSTRACT Infection with the hepatitis B virus (HBV) is still a major global health problem with an estimated 6% of the world’s population chronically infected with the virus. Chronic infection with HBV subgenotype A1, which is hyperendemic to southern Africa, is associated with a particularly high incidence of liver cancer and cirrhosis. Understanding HBV replication and developing effective HBV treatment to prevent liver cancer remain important medical priorities. Although there is a preventative vaccine for HBV, efficacy of currently available treatment of established infection is limited. Exploiting the RNA interference (RNAi) pathway through the use of small interfering (siRNA) and short hairpin RNA (shRNA) is an attractive new approach for the development gene therapies against HBV infection. Our laboratory has designed and demonstrated the efficacy both in vitro and in vivo of several shRNAs designed to target the X open reading frame (ORF) of HBV. Thus, the objective of this study was to construct a replication competent plasmid vector of the A1 subgenotype, a reporter plasmid vector of HBV and to assess the efficacy of RNAi effecters against these vectors both in vitro and in vivo. The first HBV replication competent vector, pCR-HBVA1 1.3x, containing the sequence of an HBV subgenotype A1 isolate, was successfully constructed by generating a greater than genome length sequence of HBV, that starts just upstream of endogenous HBV basic core promoter (BCP) and ends just downstream of the unique HBV polyadenylation (pA) site. Human hepatoma (Huh7) cells transfected with this plasmid secreted HBV surface antigen (HBsAg) into Abstract viii culture supernatants. In the murine hydrodynamic injection model of HBV replication, serum HBsAg, hepatitis B e antigen (HBeAg) and viral particle levels as well as relative surface and core mRNA levels were shown to be significantly elevated as compared to mock-injected mice. The second HBV vector, pCH-FLuc, was successfully generated by replacing the surface ORF with the sequence encoding Firefly Luciferase. The ability of pCH-FLuc to express Firefly Luciferase was demonstrated in a liver cell line (Huh7 cells). Co-transfection of the reporter plasmid, pCH-FLuc, with shRNAs targeted to HBV caused a significant reduction in Luciferase expression. Co-transfection/injection of the pCR-HBVa1 1.3x with shRNAs caused significant inhibition in the level of viral antigens (HBsAg, HBeAg and hepatitis B core antigen (HBcAg) as well as relative surface and core mRNA levels. This was observed both in vitro and in vivo. Our results demonstrate the potential this model allows for the study of HBV replication as well as the assessment of potential therapeutic strategies in a regionally significant subgenotype of HBV.

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Health Sciences, 2013.

Thesis (MPH))University of Limpopo (Medunsa Campus), 2011. / Introduction: Hepatitis B virus (HBV) is a highly infectious virus responsible for considerable morbidity and mortality world wide. Chronic HBV carriers can transmit HBV parenterally in a hospital setting putting healthcare workers (HCWs) and their patients at risk of infection. Aim and objectives: This study aimed to investigate knowledge, attitudes and practices towards prevention and control of HBV amongst nurses, doctors and laboratory personnel. Objectives were to determine: (a) the knowledge; (b) the attitudes; (c) the practices of nurses, doctors and laboratory personnel; (d) if there are any associations between (1) knowledge and practice, and (2) attitudes and practice; (e) the predictors of HBV vaccination uptake. Materials and Methods: This was a cross-sectional descriptive study. Self-administered questionnaires were distributed to doctors, laboratory staff and nurses at Princess Marina Hospital. Results: Two hundred questionnaires were distributed and a total of 117 were returned, giving an overall response rate of 58.5%. More doctors had good knowledge (38.9% [7/18]), followed by 20% (4/20) of laboratory staff and 11.4% (9/79) of nurses. Most staff (100% [20/20] of laboratory staff; 97.5% [77/79] of nurses; 94.4% [17/18] of doctors) had positive attitudes. More laboratory staff (100 [20/20]) displayed good practices, followed by nurses (94.9% [75/79]); and lastly doctors (88.9% [16/18]). There were no significant associations between knowledge or attitudes and practices. Vaccination was inadequate, with 50.9% (59/116) of HCWs having received at least one dose, and of these only 61% (36/59) receiving all 3 doses. Needle stick injuries occurred in 31.6% (37/117), while 33.9% (39/115) reported blood or body fluid splashes. None of the HCWs accessed PEP after exposure. Being a laboratory worker (OR: 148.4) or doctor (OR: 125.7) were the only predictors of vaccination uptake. Conclusion: There is need to increase knowledge of HCWs, vaccination availability, vaccination uptake, PEP, and reduce the exposures of HCWs.