New Vaccine Eliminates Primate form of HIV in 50 Percent of Monkeys

A new vaccine appears to clear the primate form of HIV from monkeys, according to researchers who, following further development, hope to produce an HIV version that 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," Dr. Louis Picker, associate director of the OHSU Vaccine and Gene Therapy Institute, said in a statement. "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."

The vaccine involves the pairing of cytomegalovirus (CMV), already carried by a large portion of the population, with simian immunodeficiency viruses (SIV). In mixing these two, the researchers discovered that a modified form of CMV engineered to express SIV proteins created and maintained "effector memory" T-cells.

T-cells represent a key part of the immune system; however, those found in conventional vaccines of SIV are not enough to eliminate the virus. Only those SIV-specific T-cells elicited by the modified CMV had a shot at combating the pathogen, the researchers found.

Of those monkeys treated with the vaccine prior to exposure to a highly pathogenic SIV, 50 percent eliminated all trace of the virus from their body after becoming infected.

According to Picker, the vaccine essentially teaches the "monkey's body to better 'prepare its defenses' to combat the disease."

"Our vaccine mobilized a T-cell response that was able to overtake the SIV invaders in 50 percent of the cases treated," he said. "Moreover, in those cases with a positive response, our testing suggests SIV was banished from the host. "

Going forward, Picker said his lab is investigating the reasons why only a subset of the vaccinated animals exhibited a positive response. In doing so, the researchers hope to create an even more effective vaccine.