A research team, led by investigators from the Centers for Disease Control and Prevention, has developed a new vaginal gel that they say could protect women from HIV, even if it is applied hours after sex.

This is according to a study recently published in the journal Science Translational Medicine.

In the past, scientists have developed microbicides – gels that can kill or neutralize viruses and bacteria – containing antiretroviral drugs to protect against HIV (human immunodeficiency virus) transmission.

But the researchers of this most recent study note that these microbicides contain entry or reverse transcriptase inhibitors – antiretroviral drugs that block the early processes involved in HIV infection.

This means such gels need to be given as a pre-exposure dose, which the team says can reduce compliance because gel application interferes with sexual practices.

Therefore, the researchers decided to create a microbicide gel containing integrase inhibitors – antiretroviral drugs that block processes after HIV infection, meaning the gel could be applied after sexual intercourse.

Study author Walid Heneine, of the Department of HIV Control and Prevention at the Centers for Disease Control and Prevention (CDC), told Medical News Today:

“If we can develop a microbicide gel that can be used after sex, that would improve desirability and acceptability by a woman and encourage them to use it more effectively.”

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Researchers say the new vaginal gel can protect against HIV hours after sex by stopping the virus’ DNA from entering the DNA of animal cells – a process that usually happens around 6 hours after initial infection.

The gel contains a 1% solution of an antiretroviral drug called raltegravir (Isentress).

The researchers explain that approximately 6 hours after initial infection, the DNA of the virus moves into the DNA of animal cells. Raltegravir blocks this process, and in turn, stops HIV in its tracks.

To test the efficacy of the gel against HIV infection, the research team applied it to three female macaque monkeys 30 minutes before exposure to HIV, while a group of 10 monkeys received a placebo gel. The gels were applied twice a week for a total of 7 weeks.

Of the monkeys that received the antiretroviral gel, two out of three remained HIV-free, compared with only one of the 10 monkeys that were given the placebo gel.

The researchers then applied the antiretroviral gel to six monkeys 3 hours after HIV exposure, while four monkeys were given a placebo gel. The gels were applied twice a week for 2.5 months.

The antiretroviral gel protected five of the six monkeys from HIV, while all four monkeys who received the placebo gel contracted the virus.

Commenting on the findings, the researchers say:

We provide a proof of concept that topically applied integrase inhibitors protect against vaginal SHIV (simian/human immunodeficiency virus) infection when administered shortly before or 3 hours after virus exposure.”

However, the researchers say they need to improve the gel’s effectiveness before it can be entered into human clinical trials.

“We have to evaluate acceptability, safety and efficacy, so the timeframe can be somewhere around 5 years or more,” explained Heneine.

Furthermore, they point out that although the gel protected the majority of monkeys against HIV, it may not necessarily have the same effect in humans.

But the researchers hope their study will prompt other researchers in the field to look to the use of integrase inhibitors in HIV prevention.

“There is already increased interest in this new class of drugs for HIV prevention, and I think our data will offer support for further research into using these drugs,” Heneine told us.

Medical News Today recently reported on the creation of a vaginal cream with silver nanoparticles that researchers say can block HIV transmission.