19 July 2007

Clue to HIV immunity

Patients who successfully respond to drugs that combat the Aids virus can see a key marker of immune health rebound to a level enjoyed by people without HIV, a study finds.

Patients who successfully respond to drugs that combat the Aids virus can see a key marker of immune health rebound to a level enjoyed by people without HIV, a study published online Wednesday by The Lancet says.

The paper sheds light on poorly understood conditions as to why some people on antiretroviral drugs can boost and maintain their CD4 immune cells, others see a slower increase in these key defenders while other individuals fail, sometimes tragically so.

Investigators led by Amanda Mocroft of London's Royal Free Centre for HIV Medicine looked at 1 835 people HIV-positive people before and after they were put on antiretrovirals.

On average, these individuals had a CD4 count of 204 cells per micro litre of blood at the start of the study.

In the first year of taking antiretrovirals, there was a big spurt in the CD4 count, of around 100 cells per micro litre on average.

Virus levels suppressed
HIV levels were also suppressed, to below 50 copies of the virus per micro litre, which is considered a key goal in antiretroviral treatment.

Over the next few years, lower - but still significant - improvements in the CD4 count continued.

In fact, after three years, patients who had started therapy with a CD4 count of more than 350 cells per micro litre had a CD4 count "approaching the level seen in HIV-negative individuals," Mocroft says.

On average, the boost was around 50 cells per micro litre annually, and this continued even up to the fifth year of treatment, which by the standards of HIV therapy is a long time indeed.

Most rewarding of all was that this enduring improvement was seen among patients who had had low CD4 cells (of less than 200 cells per micro litre) before they began therapy.

Those who began with more than 500 CD4 cells per micro litre saw the least relative improvement.

Only when patients respond
The upturn in CD4 cells only occurs, though, if patients continue to respond well to the drugs and can keep their HIV count to below 50 copies per micro litre, the authors warn.

CD4 cells are frontline guardians of the immune system and their levels are closely watched as barometers of a patient's ability to fight off opportunistic disease and death.

Previous research in this field has been more pessimistic, suggesting that CD4 counts tend to plateau after several years of treatment.

But those studies used less strict criteria for determining whether the drugs were working.

Their benchmark was a viral load - the number of HI-viruses in the blood - of 1 000 and 400 copies per micro litre, whereas the new study sets a far tougher standard of 50 copies or less.

The paper is published by The Lancet ahead of a meeting in Sydney from Sunday to July 25 of the International AIDS Society, which will focus especially on HIV treatment. – (Sapa-AFP)

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HIV/Aids Centre
HIV/Aids Centre

July 2007


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Dr Sindisiwe van Zyl qualified at the University of Pretoria before working for an HIV/AIDS NPO in Soweto for many years. She was named one of the Mail & Guardian's Top 200 Young South Africans in 2012.

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