A "Morning Before" Pill to Prevent HIV InfectionS

In the next decade, people may begin taking HIV medications to prevent contracting the AIDS virus, much the same way people take malaria pills. A somewhat odd study of macaques done by a group of researchers with the CDC demonstrated that two anti-retroviral medications, Emtricitabine and Tenofovir, were relatively successful at stopping HIV-like infections in the monkeys. This is great news if it turns out to work in humans. The weird part was how the researchers chose to expose the macaques to the disease. Let's say they really went for realism.

Each macaque was exposed "rectally" to the virus, repeatedly over a series of weeks. A release about the study said:

To simulate a common route of HIV transmission in humans, the researchers exposed the macaques to low weekly doses of [HIV-esque virus] 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 results showed 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.
I understand the need to recreate the circumstances surrounding HIV transmission in humans. But isn't it just as likely that a human might get HIV from a dirty needle or transfusion? Plus, anal sex isn't the only way HIV is transmitted — in Africa, where AIDS is a far more devastating problem than in the West, it's transmitted from penis-in-vagina sex.

I guess the researchers in this study really wanted to focus on preventing the spread of HIV via anal sex. Fair enough. People who think they might be at risk for contracting HIV through sex could go on a course of Emtricitabine or Tenofovir and worry less about wrapping themselves in layers of latex. I can't wait for the day when clinics in San Francisco have giant candy dishes full of HIV drugs next to the shiny trays of condoms. Image by rselph.

Prevention of Rectal SHIV Transmission in Macaques by Daily or Intermittent Prophylaxis with Emtricitabine and Tenofovir [PLoS Medicine]