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September 12, 2013

Researchers Say Vaccine 'Completely Clears' AIDS Virus from Monkeys

by VOA News

An experimental HIV/AIDS vaccine appears to have completely cleared a primate form of HIV from test monkeys. The primate version of HIV, called simian immunodeficiency virus, or SIV, causes AIDS in monkeys.

Researchers at Oregon Health & Science University hope an HIV-form of the vaccine can soon be tested in humans.

"To date, HIV infection has only been cured in a very small number of highly-publicized but unusual clinical cases in which HIV-infected individuals were treated with anti-viral medicines very early after the onset of infection or received a stem cell transplant to combat cancer,” said Louis Picker, M.D., associate director of the OHSU Vaccine and Gene Therapy Institute. “This latest research suggests that certain immune responses elicited by a new vaccine may also have the ability to completely remove HIV from the body.”

To develop the vaccine, scientists used cytomegalovirus, or CMV, a common virus already carried by a large percentage of the population, and paired it with SIV. They found that a modified version of CMV engineered to express SIV proteins generates T-cells, a type of white blood cell, that are “capable of searching out and destroying SIV-infected cells.”

About 50 percent of monkeys given highly pathogenic SIV after being vaccinated with this vaccine became infected with SIV, but over time eliminated all traces of SIV from the body.

“Through this method we were able to teach the monkey's body to better 'prepare its defenses' to combat the disease," said Picker. “Our vaccine mobilized a T-cell response that was able to overtake the SIV invaders in 50 percent of the cases treated. Moreover, in those cases with a positive response, our testing suggests SIV was banished from the host. We are hopeful that pairing our modified CMV vector with HIV will lead to a similar result in humans.”

The Picker lab is now investigating the possible reasons why only a subset of the animals treated had a positive response in hopes that the effectiveness of the proposed vaccine can be further increased.

These research results were published online today by the journal Nature. The results will also appear in a future print version of the publication.