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Development of Novel Vaccine Strategies for Duck Hepatitis B Virus Infection

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Development of Novel Vaccine Strategies for Duck Hepatitis B Virus Infection Development of Novel Vaccine Strategies for Duck Hepatitis B Virus Infection A thesis submitted for the degree of Doctor of Philosophy as a portfolio of publications by Darren Scott Miller School of Molecular and Biomedical Science Discipline of Microbiology and Immunology The University of Adelaide Adelaide South Australia ***************** January, 2008 Abstract ............................................................................................................................iv Declaration......................................................................................................................vii Acknowledgements........................................................................................................viii Publications and patent arising ........................................................................................ix Conference presentations and abstracts arising.................................................................x Awards arising ..................................................................................................................x Statement of Authorship: Chapter 2.........................................................................xi Statement of Authorship: Chapter 3...................................................................... xvii Statement of Authorship: Chapter 4....................................................................... xxi Statement of Authorship: Chapter 5..................................................................... xxvi Chapter 1: Introduction .....................................................................................................1 1.1 Hepatitis B Virus.................................................................................................. 1 1.1.1 HBV genome organisation ....................................................................2 1.1.2 The HBV Receptor ...................................................................................4 1.1.3 The life cycle of hepadnaviruses..........................................................4 1.1.4 HBV transmission and clinical outcomes.............................................6 1.2 Patterns of HBV Infection ................................................................................. 7 1.2.1 Acute HBV infection ...............................................................................7 1.2.2 Chronic HBV infection ............................................................................8 1.3 Overview of animal models of hepadnavirus infection........................... 10 1.3.1 DHBV....................................................................................................... 11 1.3.2 DHBV virion and genome organisation............................................ 11 1.3.3 The DHBV receptor .............................................................................. 12 1.4 Patterns of DHBV infection............................................................................. 13 1.4.1 Acute DHBV infection.......................................................................... 14 1.4.2 Chronic DHBV infection ...................................................................... 14 1.5 The duck immune system............................................................................... 15 1.6 Development of assays to analyse outcomes of DHBV infection .......... 16 1.7 Overview of immunity to viral infection....................................................... 17 1.7.1 Innate immune responses................................................................... 17 1.7.2 Adaptive immune responses ............................................................. 18 1.7.2.1 Humoral immune responses ............................................................... 18 1.7.2.2 Cellular immune responses................................................................. 19 1.8 Major histocompatability complexes (MHC) ............................................. 19 1.8.1 MHC I...................................................................................................... 19 ii 1.8.2 MHC II..................................................................................................... 20 1.9 Cell types involved in induction of adaptive immune responses........... 20 1.9.1 Dendritic cells ....................................................................................... 20 1.9.2 B cells...................................................................................................... 21 1.9.3 T lymphocytes (T cells)......................................................................... 23 1.9.4 CD4+ T cells............................................................................................ 23 1.9.5 CD8+ T cells............................................................................................ 24 1.9.6 NK cells................................................................................................... 26 1.9.7 Natural Killer T cells (NKT) .................................................................... 27 1.9.8 Regulatory T cells (Treg) ........................................................................ 28 1.10 Immunity to HBV infection.............................................................................. 28 1.11 Hepadnaviral vaccines.................................................................................. 30 1.11.1 The current HBV vaccine .................................................................... 30 1.11.2 Novel hepadnaviral vaccine studies ............................................... 32 1.11.3 DNA vaccines....................................................................................... 32 1.11.4 Development of DNA vaccines against DHBV infection.............. 34 1.11.5 Hepadnaviral nucleocapsid containing vaccines........................ 36 1.11.6 Whole cell vaccines ............................................................................ 37 1.11.7 Development of whole-cell DNA vaccines expressing DHBcAg. 38 1.12 Family Poxviridae............................................................................................. 39 1.12.1 Poxvirus Vaccines................................................................................. 41 1.12.2 Fowlpox virus ......................................................................................... 42 1.12.3 Poxvirus vaccines developed to treat hepadnavirus infection... 43 1.13 Antiviral treatment of chronic HBV infection.............................................. 45 1.14 Development of a combination treatment against DHBV infection..... 48 Chapter 2.........................................................................................................................50 Studying host immune responses against duck hepatitis B virus infection. ...... 51 Chapter 3.........................................................................................................................52 DNA vaccines expressing the duck hepatitis B virus surface proteins lead to reduced numbers of infected hepatocytes and protect ducks against the development of chronic infection in a virus dose-dependent manner........... 53 Chapter 4:........................................................................................................................54 Vaccination of ducks with a whole-cell vaccine expressing duck hepatitis B virus core antigen elicits antiviral immune responses that enable rapid resolution of de novo infection. ............................................................................... 55 Chapter 5:........................................................................................................................56 iii Antiviral therapy with Entecavir combined with post-exposure “prime-boost” vaccination eliminates duck hepatitis B virus infected hepatocytes and prevents the development of persistent infection. .............................................. 57 Chapter 6: Discussion .....................................................................................................58 6.1 Assay development........................................................................................ 58 6.2 DNA Vaccine studies...................................................................................... 61 6.3 ETV Treatment in Combination with Prime-Boost Vaccine Strategies.... 64 6.4 How these studies relate to HBV infection .................................................. 70 6.5 Concluding remarks........................................................................................ 73 Chapter 7: References .....................................................................................................74 iv Abstract Hepatitis B virus (HBV) is a life-threatening pathogen with major economic significance. Acute infection in adults is common, albeit usually self-limiting. Importantly, infection in infants typically results in chronic infection and increased incidence of hepatocellular carcinoma (HCC). Furthermore, the infectious carrier state is perpetuated in chronically infected individuals. Successful immuno-therapeutic vaccination would reduce the incidence of chronic infection and of HCC as well as reduce transmission of the disease. Recovery from acute and chronic HBV infection typically occurs in the presence of robust antigen-specific humoral and cellular immune responses (CMI), whereas these responses are low or absent in chronically HBV-infected individuals. Therefore,
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