Some of the human immune system's own defences against the dengue fever virus actually backfire by enabling the virus to infect even more cells, a recent study by scientists from Imperial College London has revealed.
According to the researchers, their new findings could help with the design of a vaccine against the dengue virus.
The study also brings scientists closer to understanding why people who contract dengue fever more than once usually experience more severe and dangerous symptoms the second time around.
Dengue fever is transmitted by a mosquito bite and is prevalent in sub-tropical and tropical regions including South East Asia and South America. Symptoms include high fever, severe aching in the joints and vomiting. The dengue virus can also cause hemorrhagic fever, which can be fatal.
Professor Gavin Screaton, the lead author of the study from Imperial College London, and his colleagues identified a set of antibodies, produced by the human immune system to fight off the dengue virus, that they believe scientists should avoid including in any new vaccine to prevent dengue fever.
The new research shows that these precursor membrane protein (prM) antibodies do not do a very effective job of neutralising the virus. Moreover, these antibodies actually help the virus to infect more cells.
The study suggests that when a person who has already been infected with one strain of dengue virus encounters a different strain of dengue virus, the prM antibodies awakened during the first infection spring into action again. However, rather than protecting the body from the second infection, these prM antibodies help the virus to establish itself.
This activity of the prM antibodies could explain why a second infection with a different strain of the virus can cause more harm than the first infection. The researchers believe that if a dengue virus vaccine contained prM antibodies, this could cause similar problems.
The researchers reached their conclusions after analysing individual antibodies to the dengue virus extracted from blood samples donated by infected volunteers.
The new research has been published in the journal Science.