Steps taken in herpes prevention

Yale professor Akiko Iwasaki is in the process of creating a new method of vaccination that may be the first step in preventing the spread of genital herpes, also known as herpes simplex virus.

Iwasaki, a professor of immunobiology at the Yale School of Medicine and member of the molecular virology program at the Yale Cancer Center, worked alongside immunobiology postdoctoral fellow Haina Shin to develop an alternative approach to traditional herpes vaccines. In the study, which was published Oct. 17 in the online scientific journal Nature, researchers used mice to test what Iwasaki calls the “prime and pull approach”, which distinguishes this method from previous herpes vaccines.

Priming consists of activating the body’s T-cells — a type of white blood cell that protects the body from infection­ — using a conventional vaccine. Once responsive, the T-cells are “pulled,” or chemically drawn to the vaginal tissue by chemokines, proteins that activate white blood cells, she added. The recruited T-cells were able to “establish a long-term niche” in the vaginal tissue of the mice, protecting them from contracting herpes, according the study.

“Tissue-resident memory T-cells are crucial for protection against genital herpes,” Iwasaki said.

Scientists have tried to produce a vaccination for genital herpes in the past, but none have been entirely effective, researchers said.

Typical methods of vaccination do not produce a memory T-cell response in the genital tract, a major obstacle to creating a successful genital herpes vaccine, Iwasaki said. Thus far, the vaccine has only been tested with vaginal tissue, as there is little known about the target cells in the penile tissue, she added. However, the “prime and pull” approach used in vaginal tissue alone could still prove effective.

“If we can protect women, the benefit will trickle down to men and population as a whole,” Iwasaki said.

Although the vaccine has only been tested on female mice and is not yet ready to be tested on humans, Iwasaki said she has high hopes for the vaccine when it reaches that stage. The mice she tested showed very few side effects, and the vaccine lasted up to 13 weeks in the mice, a relatively long time, she added.

Paul Aronson, assistant professor of pediatrics at the medical school, said the method of priming and pulling could potentially inhibit the transmission of genital herpes from mother to infant in the process of childbirth. Though there is no existing cure for the virus, Iwasaki said there is hope that the treatment could be used to prevent the reactivation of pre-existing genital herpes. She added that the method could possibly also be applied to other STIs including HIV-1.

Robert Siegel, an associate professor of microbiology and immunology at Stanford University, noted the difficulties that Iwasaki and her colleagues face. He compared creating a vaccine for herpes with discovering the vaccine for chicken pox.

“We might get lucky again, but all obvious strategies haven’t worked,” he said.

The next step of the research process will be to test this technique on non-human primates, Iwasaki said.

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