A vaginal gel containing compounds that block HIV from fusing with host cells may offer protection against HIV transmission, studies in lab monkeys suggest.

Dr. John P. Moore, from Weill Medical College of Cornell University in New York, and his associates evaluated the protective capability of three small-molecule compounds that interfere in different ways with the ability of HIV to get inside cells.

In test tube experiments, all three compounds inhibited infection of T cells and specimens of cervical tissue, the researchers note in their report, published online in the journal Nature.

They then dissolved the compounds in a gel, applied them vaginally to macaque monkeys and tested how well each compound protected the animals against a vaginal challenge with simian-human immunodeficiency virus (SHIV) - a virus that mimics the effects of HIV in monkeys.

In total, 21 of 28 macaques treated with one inhibitor 30 minutes before challenge were protected from infection.

When the triple combination was administered, the three treated animals were protected. Moore’s group also observed that sustained protection was provided when the drugs were administered up to 6 hours before challenging with SHIV.

“Countering transmission during primary infection may be both critically important and difficult,” the investigators note, leading them to suggest using multiple inhibitors at the highest practical concentrations.

They also point out that using these small molecule inhibitors is likely to be more feasible than using biological compounds, which “may be prohibitively expensive in the ... amounts likely to be needed per application.”

SOURCE: Nature, October 30, 2005.