HIV infection theory challenged

T cells are lost at a slow rate. 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 killed.

Modelling by UK and US researchers suggests that, if
that was true, cells would die out in months not
years. The study, led by Emory University in Atlanta and the Institute of Child Health in London, was published in the journal PLoS Medicine.

If the specific process by which HIV depletes this
kind of white blood cell can be identified, it could
pave the way for potential new approaches to treatment

Professor Jaroslav Stark The researchers 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.

If the theory were correct, then T helper cell numbers
would fall to very low levels over a number of months,
not years

Lack of certainty
Researcher Professor Jaroslav Stark, from Imperial
College London, said: "Scientists have never had a
full understanding of the processes by which T helper
cells are depleted in HIV, and therefore they've been
unable to fully explain why HIV destroys the body's
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 HIV's distinctive slow process of
cellular destruction."

The researchers think one possible explanation could
be that the virus slowly adapts itself over the course
of the infection.

But they stress that further analysis is needed to
verify this alternative theory.

Professor Stark said: "If the specific process by
which HIV depletes this kind of white blood cell can
be identified, it could pave the way for potential new
approaches to treatment."

Roger Pebody, a treatment advisor at HIV charity
Terrence Higgins Trust, said: "HIV is an incredibly
complex virus and research is ongoing to try and
establish exactly how it works.

"We need more studies in this area before we can draw
any clear conclusions."

Ken Auma
P.R.O YAFNet