German scientists are working on a new therapeutic vaccine against hepatitis B that could make the disease curable. Indeed, around 260 million people worldwide suffer from chronic hepatitis B, for which there is currently no cure. Although there is an effective hepatitis B vaccine, 880,000 people die every year from the hepatitis B virus infection. In particular, infection in early childhood leads to a chronic disease.
While the available antiviral agents can stem the growth of the viruses, they can not cure the disease. When treatment is discontinued, the hepatitis B viruses will re-emerge. The reason is a small, circular form of viral DNA that is deposited in the nucleus of infected liver cells, which allows the virus to survive and repopulate when treatment ceases. Even with a low viral load, patients suffering from chronic hepatitis B carry the risk of developing liver cirrhosis or liver cancer.
Thus, new curative treatment approaches are urgently needed. “We have developed a therapeutic vaccine that could offer a chance of recovery for the first time through two successive vaccinations,” explains Ulrike Protzer from the Technical University of Munich (TUM) and the Helmholtz Zentrum München, a German agency responsible for studying environmental health issues.
The scientists have already successfully performed pre-clinical tests. But, now, in a joint project with other research institutions, a first clinical study on humans is to be prepared. For the innovative therapeutic vaccine, two different components are combined: in a first step — described as the prime step — specific hepatitis B proteins are used as antigens to trigger the formation of neutralizing antibodies and to prepare T cells for their use. Then using the body’s own defense subsequently, the defense reaction is boosted — the boosting step — by the use of a poxvirus vector, which is incorporated in the gene sequences of the hepatitis B virus. This viral vector is said to enhance the production of specific T cells against the virus. The T cells are important immune cells in our body that can kill cells affected by viruses.
In pre-clinical models, this “prime-boost vaccine” was successful. The viral load and spread in the blood was reduced, T cells were formed and scientists were able to neutralize the affected liver cells. This showed that the approach is suitable to solve the problem of virus persistence and thus to cure the disease. More research and trial are needed to develop the vaccine further.
According to the Centers for Disease Control and Prevention (CDC), between 850,000-2.2 million people suffer from chronic hepatitis B in the United States.