Research with female monkeys at the Tulane National Primate Research Center has for the first time shown that three different anti-viral agents in a vaginal gel protect the animals against an HIV-like virus.
The research suggests that a microbicide using compounds that inhibit the processes by which HIV attaches to and enters target cells could potentially provide a safe, effective and practical way to prevent HIV transmission in women.
The study, published in the journal Nature was funded principally by the National Institute of Allergy and Infectious Diseases ( NIAID ) of the National Institutes of Health.
Women make up nearly half of all people living with HIV worldwide, and 80 percent of new cases of HIV infection in women result from heterosexual intercourse. A vaginal gel containing microbicides could be applied topically to reduce the transmission of HIV and other sexually transmitted infections.
Ronald Veazey, at the Tulane National Primate Research Center, lead author of the paper, conducted the research with simian-human immunodeficiency virus ( SHIV ), a hybrid virus made in the laboratory from HIV and SIV, which infects only monkeys.
The Tulane team tested gels containing two small molecules and a peptide -- alone and in combination -- designed to block SHIV from fusing with its target cells at or near the tissue lining of the vagina, to see whether this would prevent the virus from entering the monkeys' bodies.
To test the microbicides, the Tulane team first gave the monkeys a long-acting hormonal form of birth control ( Depo-Provera ) to synchronize their menstrual cycles and thin the vaginal membrane, which increases susceptibility to virus infection, Veazey says. During testing, researchers placed the experimental gels in the animals' vaginas. Thirty minutes later, the animals were exposed to high-dose SHIV.
The three inhibitors were each effective when used alone and also when tested in combination. Of 20 monkeys given two microbicides in combination, 16 were protected from infection. All three monkeys given the triple combination of microbicides remained virus-free. None of the monkeys experienced vaginal irritation or inflammation from the experimental gels.
" We felt these inhibitors were likely to be pretty safe. Compounds similar to them have a good safety record in humans, at least so far," Veazey says.
" This study demonstrates that combination microbicides are feasible," says NIAID director Anthony Fauci. " We need to build on these promising animal studies and move toward establishing the safety and effectiveness of combination microbicides in women."
Source: Tulane University, 2005