A long-awaited vaccination against genital herpes could be on the horizon following successful tests of the shot on animals.
Scientists from the University of Pennsylvania have developed a vaccine to protect against genital herpes caused by the herpes simplex 2 virus (HSV2). While only tested on mice and guinea pigs so far, it’s hoped the success of the study will lead to further tests on humans in the coming years.
Reporting in the journal Science Immunology, researchers gave the vaccine to 64 mice and then exposed them to the genital herpes virus. A month on, 63 of the mice showed no signs of the genital lesions that characterize the condition. The same vaccine was then tested on guinea pigs because they tend to express the virus in a very similar way to humans. None of these animals developed genital lesions and two showed some indication of being infected, although they would not be able to pass on the virus.
Researchers have been attempting to develop a potential herpes vaccine for humans since the 1920s, but all attempts have fallen flat. In fact, a long list of potential candidates has fizzled out within the past couple of years after undergoing clinical trials with humans.
It isn’t quite clear why an effective vaccine is so tough to develop, however, it’s known that the herpes virus has more complicated DNA than most treatable infections and can survive undetected by our immune systems.
Most vaccinations work by introducing an inactivated, weakened, or partial form of a pathogen to help the body's immune system recognize and fight that specific disease if it ever encounters it again. However, given the slippery nature of HSV2 infections, the researchers on this new project adopted a different approach that uses messenger RNA (mRNA) molecules that code for HSV2 proteins. This stimulates three types of antibodies that both stop the herpes virus from entering cells and ensure the virus stays in the sights of the immune system.
"We're extremely encouraged by the substantial immunizing effect our vaccine had in these animal models," lead author Dr Harvey Friedman, a professor of infectious diseases, said in a statement.
"Based on these results, it is our hope that this vaccine could be translated into human studies to test both the safety and efficacy of our approach."
The herpes simplex virus is categorized into two types: HSV1 (associated with cold sores on the lips) and HSV2 (associated with genital sores). According to the World Health Organization, up to 11 percent of people aged 15-49 are infected by HSV2 and up to 67 percent of people under 50 have HSV1 infections globally, although most infections are asymptomatic. While the most common symptom is blisters or ulcers at the site of infection, the disease is also associated with an increased risk of acquiring and transmitting HIV infections due to the lesions it creates.
"Along with physical symptoms, HSV-2 takes an emotional toll," noted Friedman. "People worry over transmission of the disease, and it can certainly have a negative effect on intimate relationships."