Development of Novel In Vitro Models for Hepatitis B Virus and Hepatitis C Virus Infection and Replication

Hepatitis B virus (HBV) and Hepatitis C virus (HCV) are hepatotropic viruses that can cause acute and chronic diseases in liver after infection. Up to 2 billion people have been infected by HBV in the world. Among those approximately 350 million of people have developed chronic Hepatitis B and the annual death is greater than 600,000 (Ganem and Prince, 2004). Global HCV infection has been estimated to be in excess of 170 million individuals, with more than 350,000 deaths per annum due to HCV-related liver disease (Te and Jensen, 2010). Although anti-HBV and anti-HCV drugs have been developed to treat patients, HBV or HCV are hard to completely eradicate. In addition, long-term drug regimes are expensive to both patients and healthcare providers. Chronic HBV or HCV infection is therefore a major cause of morbidity and mortality and major medical requirement exists to develop a better understanding of viral infection, replication which will lead to the development of more effective medicines.

Detailed research on HBV or HCV infection and lifecycle has been hampered by difficulties in sourcing and culturing the human gold standard model, primary human hepatocytes (PHHs). PHHs are a scarce resource that are isolated from low quality tissue fragment and lose function following limited period of in vitro culture (2-4 days). Therefore, alternative models have been sought and developed. Animal hepatocytes, HCC cell lines, or transgenic mouse models have contributed to understanding the pathogenesis of HBV and HCV. However, despite their successes there are a number of shortcomings in those models and as a consequence they do not properly model the in vivo situation.

The project proposed will examine an alternative and renewable source of hepatocytes which have the potential to overcome previous limitations, and in the future may offer a platform to screen for novel medicines to treat HBV and HCV infected individuals.

References:
Ganem D and Prince AM (2004) N Engl J Med, 350, 1118-1129.
Te HS and Jensen DM (2010) Clin Liver Dis, 14, 1-21, vii.

Human embryonic stem cells (hESCs) self-renew and have the capacity to differentiate into a wide range of cell types. Harnessing these properties to generate specific cell types is very attractive. The scarcity of primary human liver material means that a renewable source of fully functional hepatocytes would be very valuable to the research community and pharmaceutical industry for modelling human viral infection and lifecycle.

Our hypothesis is that hESC derived hepatocytes have an important role to play in developing accurate in vitro models of HBV and HCV infection and lifecycle. To demonstrate this we will produce defined models in a format amenable to high throughput screening.

We will accomplish this through the following specific aims:
(i) Demonstrate, refine and optimise HBV and HCV infection using hESC-derived hepatocytes.
(ii) Demonstrate model manufacture in serum free conditions to improve reproducibility of data output and cost effective large scale manufacture.
(iii) Demonstrate that our defined model can be manufactured in a format suitable for high throughput screening.

1. Key social and economic impacts
This project will provide a significant advance in the understanding of Hepatitis C virus (HCV) and Hepatitis B virus (HBV) infection and lifecycle in human hepatocytes. Moreover, the development of a high fidelity screening model will have a major future impact on the quality of life, morbidity and mortality of this patient population. Such improvements will have significant benefits in terms of direct and indirect healthcare costs, social welfare costs and has the potential to increase the productivity of the work force as a result of improved health status. In addition, by addressing an unmet medical need, the project has a great potential for wealth creation for the UK. In order to develop the impacts we shall engage:
(a). The Pharmaceutical Industry
Dr Hay has built up a strong relationship with the pharmaceutical industry and his laboratory is well positioned to deliver robust and stable models for industrial application. The benefits for the pharmaceutical industry have the potential to be realised within only a few months of completion of the project. Academic research groups could also utilise the technology within a similar time frame.
(b). Clinical practitioners
Engagement with the relevant clinical practitioners has already been established (Prof John Iredale, Prof Stuart Forbes, Prof Peter Hayes). A better understanding of viral infection and replication may lead to more effective clinical strategies to treat HCV and HBV infection using current medicines. Moreover there is the potential to develop novel anti-virals using the model developed in our proposal. The development of better understanding and interventions may reduce the current death totol per annum for Hepatitis B (greater than 600,000) and Hepatitis C (greater than 350,000).
(c). Government / Regulatory Authorities
The introduction of a new screening method may lead to the development of new treatment regimes using existing anti-virals and/or the development of a new therapeutic drug(s). The identification and clinical development of a new anti-viral strategies would be managed by the relevant regulatory authorities who evaluate safety, efficacy and cost effectiveness of new treatments.