Public Release: 

HIV's effect on white blood cells questioned by new research

Imperial College London

Scientists have refuted a longstanding theory of how HIV slowly depletes the body's 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 body's 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, today's 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 paper's 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 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 research team think that 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 adds: "If the specific process by which HIV depletes this kind of white blood cells can be identified, it could pave the way for potential new approaches to treatment."

###

Notes to Editors:

  1. 'Understanding the slow depletion of memory CD4+ cells in HIV infection', PLoS Medicine, 21 May 2007

    Andrew Yates (1, 2), Jaroslav Stark (3, 4), Nigel Klein (5), Rustom Antia (1), Robin Callard (2, 5).

    (1) Department of Biology, Emory University, Atlanta, Georgia, USA

    (2) Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, UCL, London, UK

    (3) Department of Mathematics, Imperial College London, London, UK

    (4) Centre for Integrative Systems Biology at Imperial College, Imperial College London, London, UK

    (5) Immunology Unit, Institute of Child Health, London, UK

  2. About Imperial College London Rated as the world's ninth best university in the 2006 Times Higher Education Supplement University Rankings, Imperial College London is a science-based institution with a reputation for excellence in teaching and research that attracts 11,500 students and 6,000 staff of the highest international quality.

Innovative research at the College explores the interface between science, medicine, engineering and management and delivers practical solutions that improve quality of life and the environment - underpinned by a dynamic enterprise culture.

With 62 Fellows of the Royal Society among our current academic staff and distinguished past members of the College including 14 Nobel Laureates and two Fields Medallists, Imperial's contribution to society has been immense. Inventions and innovations include the discovery of penicillin, the development of holography and the foundations of fibre optics. This commitment to the application of our research for the benefit of all continues today with current focuses including interdisciplinary collaborations to tackle climate change and mathematical modelling to predict and control the spread of infectious diseases.

The College's 100 years of living science will be celebrated throughout 2007 with a range of events to mark the Centenary of the signing of Imperial's founding charter on 8 July 1907.

Website: www.imperial.ac.uk

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.