POZ - Treatment News : Further Possible Benefits of PrEP

Intermittent use of Truvada (tenofovir plus emtricitabine) by an HIV-negative gay man who had multiple instances of unprotected anal sex didn’t prevent him from becoming infected, but did appear to help preserve a strong immune response to the virus. His case report was published online September 2 ahead of print in the Journal of Acquired Immune Deficiency Syndromes (JAIDS).

A number of clinical trials are ongoing around the world to determine whether pre-exposure prophylaxis (PrEP)—where HIV-negative people take antiretroviral drugs (ARVs) daily to prevent HIV infection—will be effective. In the meantime, it has become common in some cities for people to take a short course of ARV drugs before, or immediately after (post-exposure prophylaxis, or PEP), a high-risk exposure in hopes of preventing infection.

In this case, a 38-year-old gay man from New York City engaged in unprotected anal intercourse with multiple partners between September and November 2006. In each instance of high-risk sex, the man either began taking Truvada on the day after possible HIV exposure as PEP, or was already taking Truvada as PEP for a previous exposure when he engaged in unprotected anal sex again. HIV antibody tests of his blood remained negative until mid-December, at which point he sought care at the Aaron Diamond AIDS Research Center (ADARC) in Manhattan.

Though the ADARC report authors have been unable to determine when, precisely, the man became infected, he has maintained very low levels of virus and high CD4 counts since 2006. He has experienced little loss of CD4 cells in lymph nodes in his gut, compared with massive declines typically seen in newly infected patients. Extensive testing of the man’s blood, virus and his genes suggests that he carries neither any genetic mutations that would naturally protect him from disease progression nor a weakened strain of HIV.

This case, the authors write, validates research in monkeys showing that when PEP and PrEP failed to prevent SIV infection (the simian form of HIV), it led to much slower disease progression and consistently low levels of virus.

The researchers also point out that because this man’s virus never spiked into the hundreds of thousands, or even millions of copies, as is often the case during acute infection, his risk of transmitting the virus to others during his acute phase of infection was low. If this proves true in other cases, PrEP may still help prevent ongoing transmission of the virus by keeping the viral loads low in those undergoing the initial throes of HIV infection.