In a study published yesterday in the journal Science Translational Medicine, a group of researchers have developed a topical gel containing an antiviral drug that could be effective in preventing Human Immunodeficiency Virus (HIV) infection in women up to 3 hours after unprotected sex. 

The life cycle of HIV is complex, involving multiple stages taking place at different areas of the cell. Researchers have taken advantage of this, because it means that drugs can be developed to target a number of these steps; bombarding the virus with different drugs that attack different stages of the life cycle decreases the likelihood of drug resistance, which has been a large barrier in effective HIV treatment. Since the advent of the classical first-line drugs such as Zidovudine (AZT), which blocks the stage where HIV makes a DNA copy from its RNA genome, scientists have developed drugs that can block numerous other stages of the life cycle, such as entry and integration. 

Integration was the step focused on in this study. HIV, like all viruses, does not possess the means to replicate itself. That means that they have to hijack the host cell in order to do so. Many viruses contain genomes that don't require an integration step, because their genome can be used directly to make viral constituents. HIV, however, needs to insert its DNA copy in the host genome before it can start to make any new virus particles. The researchers found that after cell infection, integration does not begin for around 6 hours; this gave the scientists a window to work with. Using a monkey (macaque) model, they assessed the efficacy of the application of a vaginal gel containing 1% of the drug Raltegravir. They found that this gel was effective at preventing infection of 5/6 monkeys when either applied 30 minutes before exposure, or 3 hours after exposure (the placebo group all became infected).

As with any disease; prevention is better than treatment, and although current HIV drugs have seen the conversion of HIV infection as a death sentence to a chronic, manageable disease, there is a need for over the counter products that could decrease new infection rates. The most common transmission route of HIV is unprotected sex, and a large worldwide effort is underway to change this. Although there exists drugs which can be taken before (PrEP; pre-exposure prophylaxis) or after exposure (PEP; post-exposure prophylaxis), these drugs are not always available and are not 100% effective.

Although methods such as these can prevent new HIV infection, they don't prevent the spread of other STDs - so don't forget about that trusty condom! But if things happen in the heat of the moment, this gel could provide a safe and simple means to severely decrease the likelihood of onset of infection.