January 5, 2012
Experimental Potential HIV Vaccine Proves Promising In Monkeys
An experimental vaccine tested in rhesus monkeys helped protect them from getting infected with Simian Immunodeficiency Virus (SIV) -- the primate version of HIV and AIDS -- and appears to make the disease more manageable in those who aren´t protected, researchers reported on Wednesday.
The vaccine reduced the risk of infection by 80 percent among the monkeys exposed to SIV, while monkeys that became infected had lower amounts of the virus in their blood, the research team reported in the journal Nature.
The findings are further evidence that after decades of disappointments and failures, scientists are now making slow progress toward an AIDS vaccine for humans. The research, which appears online in Nature on 4 January, was co-funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), and also by the Ragon Institute, a Boston-based charity.
“We think this is both a theoretical advance as well as a practical one,” said Dan A. Barouch of Beth Israel Deaconess Medical Center at Harvard Medical School, who led the research. “This study allowed us to evaluate the protective efficacy of several prime-boost vaccine combinations, and these data will help guide the advancement of the most promising candidates into clinical trials,” he noted.
“As far as animal trials go, this is a solid step in trying to track down the [biological markers] of immunity,” said Anthony S. Fauci, director of the NIAID. “It is an important advance in knowledge.”
Scientists are especially excited because the study helped identify a key part of the immune system that is needed to offer protection from human immunodeficiency virus (HIV).
“It is nailing down in a more precise way what kind of an immune response a vaccine needs to induce to protect against the acquisition of infection as well as suppression of virus if someone happens to get infected,” Fauci told Reuters in an interview.
Barouch and his colleagues from 10 institutions tested four real and one fake vaccine on rhesus monkeys. The vaccines used modified cold and herpes viruses to either carry the immunogens or boost the immune response, and sometimes for both.
The best-performing vaccine -- one that used two different strains of adenovirus that normally causes colds -- reduced the animal´s chance of becoming infected by SIV by 80 percent (however, with enough exposure, infection was inevitable).
But once the vaccinated monkey became infected, there was less virus replicating and circulating in the bloodstream than there was in unvaccinated monkeys with the disease. That finding shows evidence that the vaccine helps boost immune response to fight the infection.
“This type of protection, and the extent of protection, in non-human primates has not been previously seen,” Barouch said.
When a piece of the SIV´s outer shell was removed from the vaccine, the animals had no protection, confirming previous suggestions that shell proteins will be an essential component of any AIDS vaccine likely to work.
The researchers also tested the animals that were best able to suppress the growth of SIV after infection. They identified nine components of the immune response (of about 35 measured) that correlated with control of the virus -- information that will also be useful in future studies.
The results are promising enough that researchers plan to test the vaccine in humans starting in January 2013.
The researchers are working closely with vaccine maker Crucell, a unit of Johnson & Johnson.
While there is no known cure for AIDS, cocktails of drugs can keep the disease from overtaking the body from many years. New research shows they can prevent the virus from spreading to sexual partners. But because HIV can be spread so easily through many outlets, there is no single easy way to prevent infection and a vaccine is still considered the best hope for conquering the virus.
Some 34 million people globally are infected with HIV and more than 25 million people have died of AIDS, according to the United Nations agency UNAIDS.
On the Net:
- National Institute of Allergy and Infectious Diseases (NIAID)
- National Institutes of Health (NIH)
- Ragon Institute
- Beth Israel Deaconess Medical Center