Herpes Vaccine Developed at HMS Licensed for Preclinical Trials

Liza Green, HMS Media Services

A candidate herpes vaccine developed in the lab of David Knipe has stimulated strong antibody and T cell responses in two animal models of herpes infection.

A herpes vaccine developed in the lab of David Knipe, the Higgins professor of microbiology and molecular genetics and head of the HMS PhD Program in Virology, has been licensed by the British company Acambis to undergo preclinical testing; the company looks forward to submitting an investigational new drug application in 2009.

Called dl5-29, the vaccine is based on a live mutant strain of herpes simplex virus 2 (HSV-2) that has two genes deleted so it cannot replicate. HSV-2 causes most cases of genital herpes while HSV-1 causes ulcers of the lip, mouth, and face.
Under the agreement, established through the Harvard Office of Technology Development, Acambis holds an exclusive worldwide license to manufacture and sell the vaccine.

Genital herpes is one of the most widespread sexually transmitted infections on Earth. Its prevalence has reached 50 percent in some developing countries, where it also may fuel the spread of HIV. The World Health Organization estimates that in the United States, 40 to 60 million people harbor the infection, making it one of the most common sexually transmitted diseases in this country, as well. The cost of herpes infections to the U.S. health care system was an estimated $1.8 billion in 2000 and is projected to rise to $2.5 billion by 2015.

Herpesvirus infections are lifelong since the pathogen becomes latent and causes recurrent disease. Although it is incurable, HSV-2 infection typically does not cause major health problems, but it can be life-threatening in immunocompromised people and newborns infected by their mothers.

Studies of dl5-29 in mice and guinea pigs already conducted by Knipe’s team showed that the replication-defective vaccine induces strong HSV-2–specific antibody and T cell responses, can protect against challenge with a wild-type HSV-2 virus, and greatly reduces the severity of recurrent disease (see Focus, Jan. 14, 2005). It also provides cross-protection against HSV-1 and is unable to revert to a virulent state or become latent.

To date, there are no licensed HSV vaccines. Herpes infections are treated with antiviral medication, which suppresses symptoms without curing
the disease.

“The dl5-29 vaccine candidate is immunogenic and induces protective immunity in two animal model infection systems,” Knipe said. “We are pleased that Acambis is developing and producing it for human clinical trials, which is the ultimate test of the vaccine concept.”