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 with the human immunodeficiency virus (HIV) before and after they were put on antiretrovirals.
On average, these individuals had a CD4 count of 204 cells per microlitre 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 microlitre on average.
HIV levels were also suppressed, to below 50 copies of the virus per microlitre, 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 microlitre had a CD4 count "approaching the level seen in HIV-negative individuals," Mocroft says.
On average, the boost was around 50 cells per microlitre 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 microlitre) before they began therapy.
Those who began with more than 500 CD4 cells per microlitre saw the least relative improvement.
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 microlitre, the authors warn.
CD4 cells are frontline guardians of the immune system and their levels are closely watched 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 AIDS viruses in the blood -- of 1,000 and 400 copies per microlitre, 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.