A longstanding theory of how HIV slowly depletes the body’s capacity to fight infection is wrong, scientists say. HIV attacks human immune cells, called T helper cells. Loss of these cells is gradual, often taking many years.

It was thought infected cells produced more HIV particles and that this caused the body to activate more T cells which in turn were infected and died.

Imperial College London modelling suggests that, if that was true, cells would die out in months not years.

The imperial team used a mathematical model of the processes by which T cells are produced and eliminated.

Using this they showed that the current theory of an uncontrolled cycle of T cell activation, infection, HIV production and cell destruction – dubbed the "runaway" hypothesis – was flawed.

They concluded that it could not explain the very slow pace of depletion that occurs in HIV infection.

They showed that if the theory was correct, then T helper cell numbers would fall to very low levels over a number of months, not years.

Link & Image: BBC