AIDS virus initially more destructive than first thought

Mar 28 2005

The AIDS virus destroys more than half of the immune cells that might recognize and help fight it, within days of infection according to US researchers, and this revelation might necessitate a re-evaluation of how the deadly infection should be tackled.

In two separate studies in monkeys Dr Mario Roederer, of the National Institute of Allergy and Infectious Diseases (NIAID) and Dr Ashley Haase and colleagues at the University of Minnesota Medical School, made similar findings which could mean a rethink of strategies to design HIV drugs and vaccines is needed.

The studies found that SIV, the monkey version of the human immunodeficiency virus or HIV, attacked CD4 memory T-cells right away and wiped out more than half of them which could mean a rethink of strategies to design HIV drugs and vaccines is needed. Not only did the virus directly kill the CD4 cells, they found, but it also caused them to them to commit cell suicide.

The virus immediately attacked the CD4 T-cells that had the correct configuration for the virus. Normally during an infection such cells would recognize and latch onto an invader, helping other components of the immune system destroy it.

HIV is different because it targets the immune system, and the two studies have revealed how quickly it makes it impossible for its victims to launch a defense.

Both teams, worked with monkeys that they infected with SIV and then monitored what happened to their immune cells.

Although the findings will be difficult to replicate in people, SIV is a good model and works in a similar way.Most people do not know the moment they are infected with the AIDS virus and their immune system is gradually destroyed leaving them vulnerable to numerous infections.

Dr Roederer's team used new, sensitive tests to show just how the virus moved so quickly and they found that 30 per cent to 60 per cent of CD4 memory T-cells throughout the body are infected by SIV at the peak of infection, and most of these infected cells disappear within four days.

Their data also demonstrated that the depletion of memory CD4 T-cells occurs to a similar extent in all tissues. As a consequence, over one-half of all memory CD4 T-cells in SIV-infected macaques are destroyed directly by viral infection during the acute phase that heralds subsequent immunodeficiency.

Any attempt to vaccinate against HIV or to provide efficient treatment must stop this process right away. There is no cure for HIV infection, which killed more than 3 million people globally last year.

Drug cocktails can control the infection, but it comes back quickly if they are stopped. More than two dozen vaccines are being tested, but experts do not expect any of them to prevent HIV infection in substantial numbers of people.