Researchers from the University of North Carolina and Merck have found promising leads in the search for drugs that may purge HIV from the body.

Up till now, anti-retrovirals (ARVs) only remove the virus from the blood and other tissues. When taken properly, they can reduce the virus to undetectable levels. But that does not mean the person is HIV negative. The virus runs away from the blood to hide in the resting CD4 cells where it is safe from the ARV attack. It can remain silent within a resting CD4 cell for many years, provided it is not stimulated to reproduce and invade the blood again.

Researchers David Margolis and Nancie Archin reported in the September 15 edition of AIDS, that they had discovered drugs (a group of compounds called class 1 HDAC inhibitors), which can provoke the HIV virus to leave its resting place and return to the blood where ARVs can completely destroy it.

Researchers believe the only way to cure AIDS is by purging the body of all places where HIV can hide. Because even when HIV hides in very small quantities, it is enough to burst out of hiding and resurge into action when ARVs are stopped.

The only way to purge the hiding places, according to current thinking, is by provoking the virus to return to the blood, while giving ARVs to kill it and prevent further infection.

Up to now, scientists have not been able to find drugs which can reach the virus once it enters its hiding place. So a person living with HIV has to take ARVs continuously.

HDAC inhibitors have now been proposed as a way of throwing the virus out of its hiding place. In their experiments, the University of North Carolina group took a variety of HDAC inhibitors and tested their ability to summon up HIV from its resting place in the CD4 cells gathered from people on ARVs but whose blood had started testing undetectable in viral load.

They found that while not all HDAC inhibitors got the virus out to the same extent, some particular inhibitors may be particularly efficient.

The findings are likely to lead to new interests in identifying which HDAC inhibitors and how they can be used by people who have reduced their viral load to undetectable levels. This quest will focus on identifying those compounds that interfere as little as possible with the body. To continue with the study, researchers must prove that HDAC is not harmful to the body too.