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The vaccine is detailed in a paper published Sept. 11 in the journal Nature.
"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," study researcher Louis Picker, of Oregon
A new approach
Previous HIV and related Simian Immunodeficiency Virus (SIV) vaccines have failed repeatedly or had limited success - they did not produce a strong enough immune response, or couldn't stop the virus from integrating into the genetic material of the cell.
Picker said that "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."
So typically, once HIV or SIV has infected a host, it's a done deal. There's no getting rid of it.
Drugs can contain the virus, but they can't clear it out completely because it inserts itself into the DNA of cells.
By attacking a specific set of white blood cells, the new vaccine can prevent SIV from taking over the bodies of about half of infected monkeys. That's still a pretty low rate of efficacy for a vaccine, but it's a start.
The big question is if the same approach could be used in a vaccine against HIV to prevent infection in humans.
How does it work?
Generally, vaccines work by triggering your immune system to attack the foreign invader. They do so by creating antibodies to a certain part of the invader, say a protein on the outside of a virus. The body then has an easier time of seeing and attacking the invader than it did before.
Specifically, this SIV vaccine is a protein inserted into a cytomegalovirus (CMV) - a virus that doesn't cause disease but does cause a powerful immune system response. The scientists gave the monkeys the vaccine and then exposed them to a highly pathogenic strain of SIV called SIVmac239.
Even though SIV persisted in some of the monkeys for months, by 18 months, 50% of the monkeys had no measurable SIV in their blood. The scientists used ultrasensitive tests and analyses but did not find any presence of SIV or its genes in the monkey's white blood cells.
All of the monkeys who cleared the virus from their systems were still clear years later. The researchers are now testing to see if the vaccine can be used on monkeys previously exposed to SIV to treat and possibly even cure them.
Relating the study to HIV
The SIV vaccine was designed to trigger a specific set of white blood cells - those that recognize and remember harmful cells and target future invaders. Think of them as immune system's SWAT team - they are armed with a much better targeting system and better weapons than other white blood cells. And they are specifically targeting the SIV virus.
An HIV vaccine that also targets a reaction from these white blood cells may be the key to creating a vaccine to provide long-term suppression and maybe even contribute to a cure for the virus. By pairing the same kind of vaccine with HIV, Picker's team hopes to see the same results in humans.
Picker told BBC news that he hopes to try the first clinical trials on humans within the next two years.