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Genital HSV Vaccine Provides Powerful Protection in Preclinical Trials

JAN 27, 2017 | KRISTI ROSA
Around the world, about half a billion individuals are infected with herpes simplex virus type 2 (HSV-2), the virus that most commonly causes genital herpes. With a number this staggering, researchers around the world have been channeling their efforts into the development of a safe and effective vaccine that will put an end to this global pandemic once and for all.

None of the past vaccine candidates have been successful, but a new trivalent vaccine coming from scientists at the Perelman School of Medicine at the University of Pennsylvania may be the one that will change it all. In preclinical tests, the trivalent vaccine—which produces antibodies that fight three different parts of the virus—proved to provide “powerful protection” in preclinical trials, according to a recent press release.

According to senior investigator Harvey M. Friedman, MD, professor of Infectious Diseases at Penn, “It’s a novel strategy, and it works beautifully. I know of no other HSV2 vaccine candidate with published results that are as promising as this study.”  

It is estimated that about one in six individuals who are between the ages of 15 and 49 are plagued by genital herpes, and this is just in the United States. On a grander scale, there are countries that have been hit particularly hard with the virus, such as Africa, where it is estimated that about half of the adult population is infected. In some adults, these infections result in genital lesions, or ulcers, and they can be particularly painful, while in others the infection may remain dormant, according to the study. Anyone who is infected has the potential to transmit the virus to others, and in fact, the infection is reported to “increase the likelihood of HIV transmission.”

Many of the vaccine candidates that were developed in the past targeted a glycoprotein called gD2, which would attach to the outer envelope of the virus and assist the virus in getting into the host cells. Although on the right track, researchers found that targeting gD2 alone didn't provide the desired amount of protection. Dr. Friedman told Contagion®, "The prior gD2 vaccine did show good effectiveness in animal models but not as good in humans."

Therefore, Dr. Friedman and his team decided to take an alternative approach by creating a trivalent vaccine that would target two other viral glycoproteins—gC2 and gE2—in addition to gD2. These two glycoproteins have been known to block immune response, which would allow HSV2 to persist within its hosts long-term.

When speaking with Contagion® on how this vaccine is different, Dr. Friedman explained, "Our vaccine builds upon the protection provided by the gD2 protein. We have taken the approach of adding two other proteins, glycoprotein C (gC2) and glycoprotein E (gE2). The virus uses gC2 and gE2 to escape immune attack. By including these proteins in the vaccine, antibodies made to the proteins block the ability of the virus to escape immune attack, including the immune attack generated by the vaccine."

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