Herpes vaccine proves effective in rodents

Researchers from the University of Pennsylvania have developed a vaccine to protect against genital herpes. Tested on both mice and guinea pigs, the immunisation was found to lead to mostly sterilising immunity from the virus — the strongest type of immunity. The results were published in the journal Science Immunology.

Genital herpes, also called Herpes simplex virus type 2 or HSV-2, is the most common sexually transmitted disease. HSV-2 may lead to painful sores, which can spread to other areas of the body. The virus also increases one’s risk of contracting HIV, and infected pregnant women may pass herpes onto their foetus or to their baby during delivery.

“Along with physical symptoms, HSV-2 takes an emotional toll,” said Professor Harvey Friedman, principal investigator on the new study. “People worry over transmission of the disease, and it can certainly have a negative effect on intimate relationships.”

Since herpes is so widespread but also often undetected, as it is only visible during an outbreak, researchers say a successful vaccine would be invaluable to many adults across the world. This led the Penn researchers to develop their vaccine as part of a collaboration with European biotech firm BioNTech, with funding from the National Institutes of Health.

Building on the approaches of many cutting-edge cancer and immunotherapy researchers, the team filled their vaccine with specific messenger RNA (mRNA), which can create proteins necessary for a strong immune response. This vaccine stimulates three types of antibodies: one that blocks the herpes virus from entering cells and two others that ensure the virus doesn’t ‘turn off’ innate immune system protective functions. This approach differs from other herpes vaccines, which often only rely on blocking the virus’s entry as the mode to attack the virus.

The researchers delivered the vaccine to 64 mice and then exposed them to genital herpes. After 28 days, 63 of the mice were found to have sterilising immunity, meaning there was no trace of herpes infection or disease after the exposure. The one remaining mouse developed dormant infection without any prior genital disease. Similarly, 10 guinea pigs, which have responses to herpes infections that more closely resemble that of humans, were also given the vaccine and exposed to the virus. No animal developed genital lesions and only two showed any evidence that they became infected, but the infection was not in a form that animals could transmit the virus.

“We’re extremely encouraged by the substantial immunising effect our vaccine had in these animal models,” Prof Friedman said. “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.”

Image credit: ©stock.adobe.com/au/Kateryna_Kon

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