John C Martin Foundation.

No abstract

Chronic hepatitis B virus (HBV) infection is a major health concern worldwide, frequently leading to liver cirrhosis, liver failure and hepatocellular carcinoma. Evidence exists that high viral antigen load may play a role in chronicity. Production of viral proteins is thought to depend on transcription of viral covalently closed circular DNA (cccDNA). In a human clinical trial with ARC-520, a RNA interference (RNAi)-based therapeutic targeting HBV transcripts, HBV S antigen (HBsAg) was strongly reduced in treatment-naïve patients positive for HBV e antigen (HBeAg) but was reduced significantly less in patients that were HBeAg negative or had received long-term therapy with nucleos(t)ide viral replication inhibitors (NUCs). The molecular basis for this unexpected differential response was investigated in chimpanzees chronically infected with HBV. Several independent lines of evidence demonstrated that HBsAg was expressed not only from the episomal cccDNA minichromosome, but also from transcripts arising from HBV DNA integrated into the host genome. The latter was the dominant source in HBeAg negative chimpanzees. Many of the integrants detected in chimpanzees lacked target sites for the siRNAs in ARC-520, explaining the reduced response in HBeAg negative chimpanzees and by extension in HBeAg negative patients. Our results uncover a heretofore under-recognized source of HBsAg that may represent a strategy adopted by HBV to maintain chronicity in the presence of host immune surveillance and could alter trial design and endpoint expectations of new therapies for chronic HBV.

Hepatocellular carcinoma (HCC) is the predominant primary liver cancer in many countries and is the third most common cause of cancer-related death in the Asia-Pacific region. The incidence of HCC is higher in men and in those over 40 years old. In the Asia-Pacific region, chronic hepatitis B virus and hepatitis C virus infections are the main etiological agents; in particular, chronic hepatitis B infection (CHB) is still the major cause in all Asia-Pacific countries except for Japan. Over the past two decades, the incidence of HCC has remained stable in countries in the region except for Singapore and Hong Kong, where the incidence for both sexes is currently decreasing. Chronic hepatitis C infection (CHC) is an important cause of HCC in Japan, representing 70% of HCCs. Over the past several decades, the prevalence of CHC has been increasing in many Asia-Pacific countries, including Australia, New Zealand, and India. Despite advancements in treatment, HCC is still an important health problem because of the associated substantial mortality. An effective surveillance program could offer early diagnosis and hence better treatment options. Antiviral treatment for both CHB and CHC is effective in reducing the incidence of HCC.