Hep B exposure bolsters infant immunity
Hepatitis B viral protein (stained green) in cord blood cells from HBV-positive mothers
Mothers with chronic hepatitis B may be doing their unborn infants a favour by exposing them to the disease, because in doing so they could be improving their offspring's immunity to infections, found Duke-NUS Graduate Medical School (Duke-NUS) scientists. This research presents a paradigm shift in the approach to treatment of patients with the disease.
The discovery was made by a team led by Professor Antonio Bertoletti from the Duke-NUS Emerging Infectious Diseases Program, in collaboration with the National University Hospital in Singapore and Universitaria di Parma in Italy. It was published in the journal Nature Communications on 25 March.
One out of 35 Singaporeans is a chronic carrier, and about 300 million people worldwide are affected by the disease. The majority of HBV chronic infections, widespread in Asia, are acquired at birth. Even though a safe and effective vaccine is available, 5 to 10 per cent of babies born to HBV-positive mothers still contract the infection. The hepatitis B virus (HBV) can cause liver inflammation and cancer in chronically infected adults.
The study challenges conventional understanding of HBV infection that transpires from mother to child immediately before and after birth. Previously, it was believed that children and young adults who acquired an HBV infection at birth from their mothers had no protective response to the disease and, therefore, were unable to react to treatment. The virus was thought to exploit the immaturity of the neonatal immune system to establish persistent infection. The newfound knowledge suggests, however, that babies exposed to the virus may actually have more mature immune systems.
Examination of the infant's immune cells in the cord blood of HBV-positive mothers showed that the cells responded better to bacteria challenge, a phenomenon known as "trained immunity. From this observation, the scientists deduced that these immune cells may be more acclimatised to dealing with potential bacterial infections than the cells from cord blood of healthy mothers. In other words, babies born to HBV-positive mothers may have a better survival advantage than babies born to healthy mothers early in life.
The paper's first author, Duke-NUS Research Fellow Dr Michelle Hong, is heartened about contributing to the understanding of a disease that is endemic in the region.
"Our work contributes to the understanding of how HBV exposure before birth shapes the global immune response of newborn infants and transforms the way we look at HBV. Despite causing diseases later in life, HBV might actually be beneficial to humans early in life, she said.
Moving forward, the researchers plan to examine the impact of HBV infection in paediatric patients, aged between 2 and 12, to determine how their immune system reacts to the virus. The results of this proposed study, combined with the team's previous research, has the potential to shape the guidelines for chronic HBV treatment in young adults or even younger patients.
