Babies exposed to hepatitis B virus (HBV) in the womb have a more developed immune system against bacterial
infections than babies born to healthy mothers, says a Singapore-led study.
The surprising result showed that while causing diseases later in life, HBV might actually be helpful in early life, according to scientists based at the Duke-National University of Singapore (NUS) Graduate Medical School in a study published in Nature Communications (25 March).
Hepatitis B is one of the world’s most common and serious infectious diseases, affecting about one-third of the population, mostly in Asia. A quarter go on to develop serious Liver diseases, causing about a million deaths each year.
Previously, it was thought that infants born from mothers with HBV are immune tolerant to HBV, which means they have no protective response to the virus and are unable to react to treatment.
However, failure of this hypothesis to explain, among other things, the efficacy of HBV vaccination in infants born to HBV positive mothers prompted researchers to investigate further.
The research team looked at umbilical cord blood taken from new born child in HBV positive mothers and found cytokine (proteins produced by immune cells to regulate immune responses) profiles similar to those found in the blood of mature adults.
Their findings indicated that exposure to the virus in the uterus induces a phenomenon called “trained immunity”, where both the innate and adaptive immune cells are more activated and mature, responding better to bacteria challenge.
The study raises questions whether current treatment practices are the most effective approach to combatting the disease. Currently, treatment is focused on those who experience active Liver disease as a result of the infection, which usually occurs past the age of 30.
But Michelle Hong, a co-author of the paper, says that in an earlier study by their same research group, they found chronically infected adolescents did not display tolerogenic T cell features (capable of producing immunological tolerance), and in fact had an active immune profile.