Hepatitis Molecular Virology

Laboratory Leader: Dr Joseph Torresi (MBBS, BMedSci, FRACP, PhD) Infectious Diseases Physician and Senior Lecturer

Staff: Dr Ruth Chin, Linda Earnest-Silveira

Students: Emily Ericsson, Duang Thammanichanon

Go to: Techniques | Publications

Research Interests

Hepatitis B Virus

Hepatitis B virus (HBV) is endemic in many regions of the world and is a major health concern in developing countries, where chronic carrier rates range from 10–20% and both perinatal and childhood infection is common. There are more than 300 million chronic carriers globally and approximately 50% of these will have chronic hepatitis.

Hepatitis C virus

Hepatitis C virus (HCV) is a major cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HCV infects 3% of the world's population (170 million individuals) and causes an estimated 476,000 deaths per year as a result of complications of end-stage liver disease. The pathogenesis of HCV is not well understood, as the virus does not appear to be cytopathic in infected hepatocytes. An effective vaccine against HCV is still lacking. The research performed by the Hepatitis Molecular Virology Research Laboratory, and through its collaborations, encompasses projects that examine humoral and cellular immune responses to HCV and technologies to incorporate important epitopes into vaccine candidates.

Identification and characterisation of cellular and humoral epitopes to hepatitis C virus

The development of a vaccine for HCV has been hampered by difficulties in culturing the virus, and the limited understanding of the immune response essential for clearance of infection. Viral infection leads to humoral and cellular immune responses, and although antibodies can be neutralising the effectiveness of the antibody response in clearing infection is limited because escape mutant viruses arise that are not neutralised. Viral clearance is associated with a vigorous CD4+ T cell response, the provision of T cell help for the induction of antibody responses, and the induction and maintenance of CD8+ cytotoxic T cells.  

A major problem inherent in the design of an effective vaccine against HCV is to address the antigenic variation that arises as quasispecies emerge within the infected individual. It is apparent that a HCV vaccine must elicit vigorous and broad based antibody, CTL and helper T cell responses. Our research has centred on the incorporation of HCV epitopes into immunogenic structures that are recognised by antibody, CD4+ or CD8+ T cells isolated from patient blood samples and which could form the basis of an effective vaccine.

Hepatitis B and C, MAPK, JAK/STAT/SOCS cell signalling and viral persistence

The mechanisms by which HBV and HCV are able to stimulate cell survival and proliferation is not clear. Infection with HBV and HCV activates a complex interplay between several components of the mitogen-activated protein kinase (MAPK) and the JAK/STAT/SOCS signalling pathways. This network of highly complex signalling processes is activated in response to a diverse array of extracellular stimuli such as cytokines, growth factors, toxins, radiation and infections, and results in the various cellular responses that regulate gene expression, cytokine production, cell survival, maturation and differentiation, proliferation and apoptosis. Significantly, activation of MAPK pathways by HBV and HCV and the interaction between these pathways and the JAK/STAT/SOCS pathways is associated with cell proliferation, viral persistence and oncogenesis.

The interactions that occur between HBV and HCV and the MAPK network are complex and it is difficult to establish a coherent theme that can provide a mechanism for the observed effects. Interpreting the many and varied effects of HBV and HCV infection is limited by the inability to grow both viruses in culture and, consequently, studies have been limited to the effects of individual viral proteins on cell signalling networks. Our unique approach of infecting liver derived cells in culture with recombinant adenoviruses expressing HBV and HCV more closely mimics events that occur in natural infection, and provides important insight into viral-viral interactions and mechanisms of viral pathogenesis and oncogenesis.

Techniques

• Molecular biology
• Cloning
• Site directed mutagenesis
• Cell culture
• Recombinant protein expression
• Transfection of mammalian cells in culture
• Southern blot hybridization
• Northern blot hybridization
• DNA sequencing
• PCR
• Real Time PCR
• ELISA

Publications

Hepatitis

1. Torresi J, Bharadwaj M, Jackson DC & Gowans EJ (2004). Neutralising antibody, CTL and dendritic cell responses to hepatitis C virus: A preventative vaccine strategy. Curr. Drug Targets, 5(1):41–56.

2. Gouskos T, Wightman F, Chang J, Earnest-Silveira L, Sasadeusz J, Lewin SR & Torresi J (2004). Severe hepatitis and prolonged hepatitis B virus-specific CD8 T-cell response after selection of hepatitis B virus YMDD variant in an HIV/hepatitis B virus-co-infected patient. AIDS, 20 August, 12:1734–7.

3. Chua BY, Healy A, Cameron P, Stock O, Rizkalla M, Zeng W, Torresi J, Brown LE, Fowler NL, Gowans EJ & Jackson DC (2003). Maturation of dendritic cells with lipopeptides that represent vaccine candidates for hepatitis C virus. Immunology and Cell Biology, 81:67–72.

4. Torresi J, Earnest-Silveira L, Deliyannis G, Edgtton K, Zhuang H, Locarnini SA, Fyfe J, Sozzi T & Jackson DC (2002). Vaccine induced anti-HBsAg antibody escape mutants of hepatitis B virus arising as a consequence of sequence changes in the overlapping polymerase gene that are selected by lamivudine therapy. Virology, 293:305–13.

5. Torresi J, Earnest-Silveira L, Civitico G, Walters T, Lewin S, Fyfe J, Locarnini SA, Manns M, Trautwein C & Bock T (2002). Restoration of replication phenotype of lamivudine resistant hepatitis B virus mutants by compensatory changes in the 'fingers' sub-domain of the viral polymerase selected as a consequence of mutations in the overlapping S gene. Virology, 20 July, 299(1):88.

6. Bock TC, Tillmann HL, Torresi J, Klempnauer J, Locarnini S, Manns MP & Trautwein C (2002). Molecular characterization of lamivudine enhanced HBV mutants in patients with sudden onset of liver failure following liver transplantation. Gastroenterology, 122:264–73.

7. Chin R, Shaw T, Torresi J, Sozzi V, Trautwein C, Bock T, Manns M, Isom H, Furman P & Locarnini S (2001). In vitro susceptibility of wild type and drug resistant hepatitis B virus to (-)- b -D-2, 6 diaminopurine dioxolane (DAPD) and 2'-fluoro-5-methyl-?-L-arabinofuranosyluracil (L-FMAU). Antimicrobial Agents and Chemotherapy, 45:2495–501.

8. Delaney WE iv, Edwards R, Colledge D, Shaw T, Torresi J, Miller TG, Isom HC, Bock CT, Manns MP, Trautwein C & Locarnini, S (2001). Cross-Resistance testing of antihepadnaviral compounds using novel recombinant baculoviruses which encode drug-resistant strains of hepatitis B virus. Antimicrobial Agents and Chemotherapy, 45:1705–13.

9. Torresi J & Locarnini SA (2000). Antiviral chemotherapy for the treatment of hepatitis B virus infections. Gastroenterology, 118:83–103.

Travel Medicine

1. Leder K, Black J, O'Brien D, Greenwood Z, Kain K, Schwartz E, Brown G & Torresi J (2004). Malaria in travelers: A review of the GeoSentinel Surveillance Network. Clinical Infectious Diseases, 39:1104–12

2. Brown G, Torresi J & Flint S (2004). Delayed onset of malaria – Implications for chemoprophylaxis. N Engl J Med, 350: 195–7.

3. Yung A, Ruff T, Torresi J, Leder K & O'Brien D (2004). Manual of Travel Medicine (2nd edn).

4. Leder K, Sundararajan V, Weld L, Pandey P, Brown G & Torresi J (2003). Respiratory tract infections in travellers: A review of the GeoSentinel Surveillance Network. Clinical Infectious Diseases, 36:399–406.

5. Elliott JH, Kunze M & Torresi J (2002). Hepatitis A vaccine failure. Lancet, 1 June:1948–9.

6. O'Brien D, Tobin S, Brown GV & Torresi J (2001). Fever in returned travellers: A review of hospital admissions over a three-year period. Clinical Infectious Diseases, 33:603–09.