Washington, Feb 5 : Antiretroviral drugs that are used to treat HIV can also protect people from getting the AIDS virus, especially if two drugs are taken in combination before exposure to the virus occurs, suggests a new study in macaques.
The study, led by Jose Gerardo Garca-Lerma and Walid Heneine from the US Centres for Disease Control and Prevention, found that macaques which were repeatedly exposed to SHIV (a virus closely related to HIV) but received antiretroviral drugs were less likely to become infected than exposed macaques that received no anti-HIV medication. The best protection was seen in macaques that had received a combination of two drugs.
Pre-exposure prophylaxis (PrEP), the prevention of infection by treating people with drugs before they are exposed to the germ in question, is often used to prevent malaria, but has not yet been shown to be effective against sexual transmission of HIV.
To create a common route of HIV transmission in humans, the researchers exposed the macaques to low weekly doses of SHIV that were given rectally.
Five groups of macaques were all exposed to the virus in the same way, but they were given different dosages and combinations of antiretroviral drugs. Three groups received drugs daily: the first was only injected with one anti-HIV drug, emtricitabine (FTC); the second group received a daily dose of this drug by mouth in combination with an oral form of another anti-HIV drug called tenofovir; the third was injected with FTC and a high dose of tenofovir every day.
A fourth group was also injected with FTC and a high dose of tenofovir, but macaques in this group were only treated shortly before and after the weekly exposures to HIV. For comparison a fifth group of macaques received no anti-HIV drugs.
The analysis if the study revealed that macaques from any of the four groups that received drugs were less likely to become infected than those in the fifth (control) group.
All of the macaques receiving the combination of both FTC and the high dosage of tenofovir were protected from infection, whether they were from the group that received these drugs daily, or only around the time of exposure to infection.
The results suggest that higher doses and combinations of drugs worked better than single or low doses, and also that PrEP may not need to be taken every day to be effective.
The study is published in the open access journal PLoS Medicine.