A drug currently prescribed to treat a rare enzyme deficiency can help cells clear the herpes simplex viruses -- a virus causing contagious sores, most often around the mouth or on the genitals, say researchers, including one of Indian-origin.

The data, published in the journal Science Advances, shows that the antiviral activity of the drug -- called phenylbutyrate, or PBA -- was even better when used along with acyclovir, a common HSV-1 treatment.

When used in combination, less acyclovir is needed to effectively suppress the virus compared to acyclovir alone -- this is important because acyclovir is also known to have toxic side effects in the kidneys.

"There are very few drugs available to treat herpes simplex viruses, so when new drugs become available, especially drugs that enable fewer side effects, it is a welcome discovery," said study researchers Deepak Shukla from the University of Illinois at Chicago.

"Acyclovir can have very toxic effects on the kidneys, especially when it is given in higher doses for HSV-induced encephalitis, which is rare but can be deadly. By combining acyclovir with PBA, we need less acyclovir to effectively treat HSV-1," Shukla added.

Treatment for both infections often includes acyclovir -- a systemic medication taken orally. However, long-term use often results in resistance to the drug as well as kidney damage.

The research team investigated the antiviral effects of PBA and found that in cells the drug disrupts the ability of the virus to hijack the cellular machinery used to produce proteins.

Normally, viruses infect cells and force them to produce viral proteins so the virus can replicate itself.

But the cell also continues to produce proteins for its own use, leading to a lot of stress in the structure -- called the endoplasmic reticulum, or ER for short -- that makes protein.

The researchers found that in cells, PBA alone was able to clear HSV-1 from cells of donated human corneas or from donated human skin tissue just as well as acyclovir.

In a mouse model of ocular HSV-1 infection, PBA administered intraperitoneally was able to clear the virus from the eyes.

In an animal model of HSV-2 vaginal infection, mice that received PBA had no signs of the HSV-2 virus in tissues, similar to mice treated with acyclovir.

When they tested a combination of PBA with acyclovir cells infected with HSV-1, the drug combo was able to completely clear the virus from the cells faster and better than either drug alone.

"PBA is an exciting new therapeutic for treating herpes infections that can help reduce side effects associated with long term or high dose use of acyclovir, a commonly prescribed medication to treat herpes viruses," Shukla said.