The World Health Organization estimates that over 500 million people have Herpes Simplex Virus Type 2 (HSV-2), a sexually-transmitted version of herpes responsible for genital herpes. With no vaccine currently available, researchers from the US have created a new vaccine for the virus that has shown promise in early trials.
The vaccine consists of a genetically edited form of Herpes Simplex Virus Type 1 (HSV-1), known to cause cold sores on the lips. In particular, the researchers modified region 2 (R2) of the virus, preventing it from advancing deep into the nervous system, where it causes havoc.
For their study, the researchers tested the vaccine on guinea pigs with HSV-2. They also tested another promising vaccine candidate for HSV-2 on another groups of guinea pigs, and a placebo as a control.
Not only did the R2 vaccine lead to a significant increase in the number of virus-combatting antibodies in the animals; it also left them with fewer lesions on their genitals, less viral replication, and less viral shedding, something that leads to viral spread to others.
All in all, the researchers found that just one of the 12 guinea pigs injected with the R2-modified form of HSV-1 developed acute lesions, whereas five of the 12 receiving another promising vaccine candidate developed lesions. The R2 vaccine also reduced the number of days in which the guinea pigs were able to shed the virus from 29 days to 13, whereas the other vaccine candidate had no effect.
What's more, the researchers also found that guinea pigs receiving the R2 vaccine showed no signs of HSV-2 in the cluster of brain cells they are normally found post-infection. They also found that those who received the R2 vaccine had three times the levels of neutralizing antibodies of those inoculated with the other vaccine.
“The fact that the viral shedding was knocked down so much with the R2 vaccine is really important, because it’s the viral shedding — even if it doesn’t cause lesions - that can then pass on the virus,” says Gary Pickard, one of the authors of the study.
“If you have genital herpes, you can pass that on to your significant other, not knowing that you’re doing it. It’s very problematic. So the fact that the shedding was knocked down so much is a really good sign.”
The researchers say that the vaccine could also work in cattle and hogs, where it can cause respiratory disease and curb appetite at a high cost to the livestock industry. While a vaccine for herpes virus currently exists for livestock, it suffers from inefficacies that, they believe, the R2 vaccine could address.