In Gothenburg, Sweden, scientists have found a protein that acts like a key, letting the virus that causes genital herpes sneak into the nervous system. The discovery, published in the journal PLOS Pathogens, could one day lead to a vaccine against a disease that millions of people live with worldwide. Researchers at the University of Gothenburg made the breakthrough by studying mice infected with the herpes virus (HSV-2). Their work reveals how the virus causes lifelong infections — by hiding in nerve cells where it can stay dormant for years and resurface later. Genital herpes spreads through sexual contact and is one of the most common viral infections on the planet, though many people who carry it never notice any symptoms. Others experience recurring pain, blisters, or sores that current medicines can soothe but not cure. There is still no approved vaccine. The new study focused on a protein called glycoprotein G, which sits on the surface of the virus and infected cells. When researchers removed a specific form of this protein from the virus, the virus could still multiply in mucous membranes — the moist tissues where infection starts — but it lost the ability to travel deeper into the nervous system and the central nervous system. 'This suggests that glycoprotein G plays a critical role in the virus's ability to reach and infect the nervous system,' said microbiologist and researcher Ebba Könighofer. The team also discovered that the protein works two ways: it helps the virus spread, but it can also be used to train the immune system to fight back. When mice were given glycoprotein G as a kind of practice target, their bodies produced strong antibody responses and strong T-cell responses — two important weapons in the immune system's arsenal. Those mice were protected from genital herpes and from the virus spreading to their nerves. The researchers also found that the sugar molecules naturally attached to glycoprotein G matter a great deal. When those sugar structures were removed, the T-cell response and the protective effect grew weaker. 'Our results identify glycoprotein G as both a virulence factor and a promising vaccine target,' said Rickard Nordén, a microbiologist and associate professor at the university. 'This provides a strong rationale for including the glycosylated form of the protein in future herpes vaccine development.' For the 500 million people worldwide living with genital herpes, the road to a vaccine is still long. But for the first time, scientists have a clearer map of the destination.