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.

This thesis investigated how virologic and serologic kinetics of the hepatitis B virus (HBV) could influence the natural history and treatment of chronic hepatitis B (CHB). Virologic kinetics were described in the first five studies, with serologic kinetics being described in the next five. The first study delineated the HBV DNA profiles of 1,400 treatment-naive Asian CHB patients. Increasing viremia was noted with increasing age, highlighting the large therapeutic demand in Asian patients with hepatitis B e antigen (HBeAg)-negative CHB. The second study analyzed the association between viral load and liver histology in 319 patients, showing HBV DNA levels to have strong association with HBeAg-negative disease severity. The next three studies investigated the efficacy of baseline and on-treatment HBV DNA levels in predicting clinical outcomes in 117, 165 and 222 patients on telbivudine, lamivudine plus adefovir and entecavir respectively. Absolute on-treatment HBV DNA levels at week 12 or 24 predicted favorable outcome with telbivudine and lamivudine / adefovir therapy, while excellent viremic suppression with very low rate of resistance development was shown in the entecavir study. The following three studies examined the role of serum HBsAg measurements in different disease phases of CHB. First, histology specimens of 140 HBeAg-positive patients were analyzed together with HBsAg levels. High HBsAg titers (>25,000 IU/mL) were found to be predictive of insignificant fibrosis. In the next study involving 300 treatment-naive HBeAg-negative patients stratified by their viral loads, combination of low HBsAg and HBV DNA levels predicted significant HBsAg decline. This is followed by a study comparing HBsAg levels of 203 CHB patients achieving HBsAg seroclearance with 203 age- and sex-matched controls over a 3-year period. Serum HBsAg <200 IU/mL and a significant annual HBsAg reduction were found to be predictive of HBsAg seroclearance. The penultimate study investigated the usage of two novel HBV serologic markers, linearized HBsAg and hepatitis B core-related antigen, in 329 CHB patients achieving HBsAg seroclearance with a conventional HBsAg assay. More than 40% of patients had seropositivity to one or both serologic tests. Finally, the last study of this thesis investigated and compared the changes in serum HBsAg, intrahepatic HBV DNA and covalently closed circular DNA (cccDNA) after 1 year of nucleoside analogue therapy. Minimal changes in both serum HBsAg and intrahepatic cccDNA were noted after 1 year of therapy, but in patients with a significant decline in serum HBsAg levels, there was a corresponding significant reduction in cccDNA. This series of studies illustrated how the monitoring of serum HBV DNA and HBsAg levels could assist in optimizing management strategies for CHB. / published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Medicine / Master / Doctor of Medicine

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (M. Med. Sc.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 51-58).

Mainz, Univ., Diss., 2001.