Mystery of HIV "reservoirs" in the body deepens

The conclusion was that a relatively small number of infected cells hole up in hidden "reservoirs" in the body, only to re-emerge and multiply as soon as the drugs are stopped. One of the suspected latent reservoirs is the body’s lymph glands.

Researchers at the US National Institutes of Health (NIH), writing in July’s issue of the journal Nature, say they now believe that the virus has additional other ways of hiding.

They carried out tests on nine patients who had been receiving the cocktail, called highly active anti-retroviral therapy (HAART), and whose level of HIV infection in the blood had slipped below detectable levels for an average of 21.8 months. HAART was discontinued, and HIV levels in the bloodstream quickly rose again — but in four of the nine cases, the virus was genetically different from the one initially treated.

"These results indicate the existence of other persistent HIV reservoirs that could prompt rapid emergence of plasma viremia after cessation of HAART," the NIH researchers write.

In an adjoining commentary, leading researchers David Ho and Zhang Linqi of the Aaaron Diamond AIDS Research Center at New York’s Rockefeller University said the findings highlight the prevailing ignorance about how the latent reservoirs work. "In tackling the issue of HIV-1 eradication, we should not be content with ‘pounding away’ at the virus using only existing anti-retroviral drugs. Instead, we must undertake studies to unravel the fundamental mechanism responsible for the residual viral replication," they write.

HAART has several drawbacks, including side-effects and cost. Annual treatment is around 2,900 dollars per person per year, putting it way beyond the reach of HIV victims in Africa, by far the most affected region for AIDS.

Meanwhile, Swiss scientists called for clinical trials of a drug, mycophenolic acid, saying it had the potential to boost the effectiveness of HAART. The drug is already used in conjunction with other treatments to prevent organ rejection after transplants.

In a Pilot clinical study, also published in Nature Medicine, the team from the University Hospital in Vadois found that mycophenolic acid, when used with HAART, reduced the amount of infection as well as the numbers of two types of blood cells that are hijacked by the virus and used as a vehicle for replication.