Two different studies, from the USA and Brazil, have used mice infected with herpes viruses to understand more about viral infections, as well as develop better treatments.

To understand how to better treat herpes, a US study at the Fred Hutchinson Cancer Center, Seattle, tested a gene editing application using CRISPR (called a gene drive), that spreads a specific gene from one person to another.

Herpes (herpes simplex virus or HSV), is common in humans (up to 65%) causing an infection that can result in painful blisters or ulcers. While it is treatable there is no current cure.

The researchers engineered HSV-1, a type of herpes usually spread orally, to have a specific genetic modification that made it glow red. When this was introduced into mice infected with a different type of HSV-1, that glows yellow, the team saw, under a microscope, that different tissues in the animals began to turn red over time. This showed that the engineered HSV-1 had successfully ‘copy and pasted’ its DNA into cells.

Although the study was done to demonstrate the feasibility of this method (proof-of-concept), it highlights that gene drives could be useful to disable harmful herpes viruses by altering their ability to infect.

First author Marius Walter said: “We’re trying to see if we can use the technique as a way to prevent or cure disease. You’re basically using herpes to target herpes.”

Meanwhile, an international team, led by the University of São Paulo (USP), Brazil, has analysed mice infected with HSV-1 to understand how pain arises as this is one of the first signs of a herpes infection.

The researchers saw that the sensation was triggered in the mice when the virus’s DNA was recognised by a protein, called STING, which is present in the nerve cell endings that initiate the sensation of pain.

Removing STING from these nerve cell endings therefore resulted in significantly reduced pain in the animals (as indicated by different signs, such as shaking and licking) – suggesting that STING is directly linked to pain in this context, and may also apply to other types of viral infection, such as Covid-19, and bacterial infections.