Herpes vaccine to be tested in humans after best result yet in animals

A vaccine for herpes could be on the horizon Jonnie Miles/Getty Images

Hopes have been raised that we will soon have a vaccine to halt the spread of genital herpes, following an animal study that has achieved better results than any previous trial. More than 1 in 10 people worldwide are infected by the virus.

The herpes simplex 2 virus (HSV2) is spread by vaginal, anal or oral sex. People remain infected for life, as some of the HSV2 viruses hide away in nerve cells where they lie dormant.

Most people never realise they are infected but others suffer from outbreaks of painful symptoms, including genital lesions. The virus can also cause complications such as meningitis, and is occasionally passed on to babies during birth with fatal results.

People are most infectious when they have genital lesions but even those with no symptoms often still shed the virus and can infect others.

So far efforts to develop a vaccine have failed. But an experimental vaccine developed by Harvey Friedman at the University of Pennsylvania has prevented genital lesions in all mice and guinea pigs tested.

In 98 per cent of mice and 80 per cent of guinea pigs it also prevented the low-level “hidden” infections. Other experimental vaccines regarded as promising enough to test in humans have failed to prevent these hidden infections in animals.

“Our results in mice and guinea pigs are very encouraging – better than anything we have seen in the literature,” say Friedman. “But we won’t know if this vaccine will work until it is tested in humans.”

Many vaccines consist of modified or inactivated viruses. Friedman’s vaccine is unusual in that it consists of messenger RNA (mRNA) molecules that code for three HSV2 proteins. When these mRNAs get inside cells in the body, the cells produce the viral proteins, triggering an immune response. No mRNA-based vaccine has yet been approved, but some are already in human trials.

Friedman’s team is now testing whether the vaccine can also protect against herpes simplex 1, or the cold sore virus. Seven out of 10 people worldwide are infected with HSV1.

Read more: Hope for herpes vaccine after it wipes out virus in monkeys

If the vaccine does prove effective, Friedman envisions it being given to teenagers alongside the highly successful HPV vaccine. The HPV virus causes almost all cervical cancers, and also throat and mouth cancers in both sexes.

Some researchers are working on ways of destroying dormant viruses inside nerve cells using the CRISPR gene editing technique. But preventing infections in the first place is clearly the best option.

Journal reference: Science Immunology, DOI: 10.1126/sciimmunol.aaw7083