A recent study by an international team of researchers opens up new possibilities for research into the pathogenesis of hepatitis B viruses. The basis for this is a newly discovered, unusual HB virus in shrews.
Chronification of the HBV infection, which occurs particularly frequently in newborn babies or in children and adolescents and often remains undetected for decades, is one of the essential characteristics of this viral disease. In all known HB viruses of mammals, including humans, the viral protein HBeAg (hepatitis B e-antigen) enables the infection’s chronification.
This protein forms the virus during infection. As an immunomodulator, it suppresses the body's specific immune defense against HBV, so that the infection cannot heal, and hence runs chronically - often with very high virus concentrations in the blood. In the absence of this viral protein, however, the body's immune system can successfully fight the incipient infection.
The newly discovered HBV in shrews (such as the Suncus murinus, Suncus etruscus, etc) surprisingly do not have the genetic ability to produce the immunomodulator HBeAg. Despite the absence of HBeAg, the infected animals still showed high HBV virus concentrations in the blood. "This indicates a very successful but unusual infection characteristic and spread of shrew HBV in its hosts," said the researchers. "Since the virus is not able to infect human liver cells, an infection of humans with these viruses can very probably be ruled out. A danger for the population in contact with HBV-infected shrews is therefore not to be assumed."
The second special feature of the newly discovered virus is that it does not use the liver gallic acid transporter previously known from human and monkey HBV to enter its target cells, but takes a previously unknown path into the cell.
The scientists now hope to further investigate the unusual infection behavior of this shrew HBV, which functions without the central immunomodulator HBeAg. Despite enormous international efforts, no effective therapy for the treatment of chronic hepatitis B has yet been developed. One of the reasons for this is that there are no simple animal models that can be used to investigate the complex interactions of the virus infection with the host's immune system. However, the recently discovered of shrews’ HBV makes a suitable model for the investigation of HBV infection further within reach.