Scientists have refuted a longstanding theory of how HIV slowly depletes the bodys capacity to fight infection, in new research published today.
The researchers were looking at T helper cells, a class of white blood cells which recognise infection and co-ordinate the bodys immune defences. They are attacked by HIV, and their numbers gradually decline in HIV positive patients. It has long been a major puzzle why this process of depletion is so slow, often taking 10 years or more.
One popular theory has been the runaway hypothesis, which says that T cells infected by HIV produce more HIV virus particles, which activate more T cells, that in turn become infected, leading to an uncontrolled cycle of T cell activation, infection, HIV production and cell destruction.
However, todays new study in PLoS Medicine shows that this theory cannot explain the very slow pace of depletion that occurs in HIV infection. The research team used a mathematical model of the processes by which T cells are produced and eliminated to show that if the runaway theory was correct, then T helper cell numbers would fall to very low levels over a number of months, not years.
One of the papers authors is Jaroslav Stark, Professor of Mathematics at Imperial College London, and Director of the Centre of Integrative Systems Biology at Imperial. He said: Scientists have never had a full understanding of the processes by which T helper cells are depleted in HIV, and therefore theyve been unable to fully explain why HIV destroys the bodys supply of these cells at such a slow rate. Our new interdisciplinary research has thrown serious doubt on one popular theory of how HIV affects these cells, and means that further studies are required to understand the mechanism behind HIVs distinctive slow process of cellular destruction.
The research team think that one possible explanation could be that the virus slowly adapts itself over the course of the infec
Contact: Danielle Reeves
Imperial College London