Research published today in Virology Journal describes a new model to study chronic hepatitis B virus (HBV) infection, which could be used to determine risk factors and test treatments for the disease. HBV is estimated to infect one third of the world’s population at some point in their lives, leading to cirrhosis of the liver and in some cases liver cancer. The virus usually causes an acute, self-limiting, infection but it can also persist in the liver leading to chronic hepatitis and a greatly increased risk of hepatocellular carcinoma (HCC). With over 240 million people chronically infected worldwide, this makes HBV a major cause of cancer. Although there is a successful vaccine, there is currently no effective treatment to remove the virus from those chronically infected, who are at greatest risk of HCC. One obstacle to developing new antiviral drugs is the lack of an animal model to study the virus, as HBV only infects humans and some other primates.
The tree shrew (Tupaia belangeri chinensis) has emerged as an important animal model to study HBV infection. This non-rodent, primate-like, animal is similar enough to humans to be infected acutely, and develops many of the same symptoms. Until now, however, a chronic infection had not been established. Wang et al. established a chronic infection by inoculating neonatal tree shrews with serum from infected humans or infected tree shrews, containing millions of virus particles. Neonates were chosen because humans show a higher rate of chronic infection when they are infected during birth. They found that 13% of the neonates showed clear evidence of chronic infection, with HBV antigens and DNA detected in the liver and serum up to 228 weeks after inoculation. As well as using the new model for anti-viral drugs, the authors suggest that their model “might enable genetic and immunologic investigations which would allow determination of underlying molecular causes favouring susceptibility for chronic HBV infection.”