A vaccine has successfully cleared the monkey version of HIV from the bloodstreams of infected animals, leading scientists to believe they may be able to replicate the effect for humans with HIV.
"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 Oregon Health and Science University Vaccine and Gene Therapy Institute, said in a press release. "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 U.S. Department of Health & Human Services reports that about 1.2 million people in the U.S. are living with the human immunodeficiency virus (HIV), the virus that causes AIDS. One in five people living with HIV are not aware that they are infected.
The researchers tested a vaccine for a specific kind of simian immunodeficiency virus (SIV) called SIVmac239 on 16 rhesus macaque monkeys. This version is up to 100 times more deadly than HIV, and monkeys typically die within two years.
The vaccine used the cytomegalovirus (CMV), which is part of the herpes family. Researchers modified the virus' natural ability to spread through the body, instead having it tell all the various parts of the immune system -- particularly the T-cells that can fight off SIV infection -- to target the SIV.
All the monkeys were vaccinated and then exposed to SIVmac239. In nine of the cases, the monkeys' immune systems were able to fight off infection and destroy the virus. Those monkeys remained infection free between 1.5 to three years later.
"It's always tough to claim eradication -- there could always be a cell which we didn't analyze that has the virus in it," Picker told the BBC. "But for the most part, with very stringent criteria... there was no virus left in the body of these monkeys."
Researchers are still trying to determine why it worked in some of the monkeys but not others.
"It could be the fact that SIV is so pathogenic that this is the best you are ever going to get," Picker explained. "There is a battle going on, and half the time the vaccine wins and half the time it doesn't."
In July, doctors at Brigham and Women's Hospital in Boston reported that two previously HIV-positive men who received stem cell transplants to treat their lymphoma cancers.
Another HIV-positive patient who received a stem cell transplant to treat his leukemia, Timothy Brown,. While researchers found traces of HIV in his tissue in June 2012, Brown said that virus is dead and cannot replicate.
In Brown's case, the donor for the stem cells was part of the 1 percent of Caucasians that has a genetic mutation called delta 32 that makes them resistant to HIV. The two Boston patients' bone marrow donors did not have the delta 32 mutation.
In another highly publicized case,was reportedly cured of the virus as well. The child was immediately placed on a three-drug infusion treatment within 30 hours after birth, something that is not typically done so quickly. Doctors did not know her mother was HIV positive until she was in labor.
The researchers in the latest monkey study want to try the vaccine method on humans with HIV, but acknowledge that they still have to make sure it is safe. They hope the first human clinical trials can start within two years.
The research was published in Nature on Sept. 11.