Scientists say they have found new evidence as to why a tiny minority of individuals infected HIV have a natural ability to fight off the AIDS virus.
The study involved scientists from the United States, Canada, Japan and Germany and was published in the Nature Immunology journal.
More from GlobalPost: US reveals nearly $1.5 billion in unspent AIDS money
AFP explains that the study looked at 10 infected people -- five of whom took antiretroviral drugs and five "elite controllers" or or "long-term non-progressors" who remained naturally healthy -- and concluded that "the secret lies not in the number of infection-killing cells a person has, but in how well they work."
It says that previous research has found that only one person in about 300 has the strain of "killer" cells called cytotoxic T lymphocyte (CTL) which allow them to control HIV without drugs. This latest study says that the strain has molecules called receptors that are better able to identify HIV-infected white blood cells for attack.
"We have been scratching our heads since then, asking how, with so many killer cells around, people are getting AIDS. It turns out there is a special quality that makes them (some cells) better at killing," Bruce Walker, co-author and an infectious diseases expert at the Ragon Institute in Massachusetts, is quoted as saying.
More from GlobalPost: Activists question Obama's AIDS plan
"This is another example of HIV revealing its secrets. Having been in this field for 30 years, the remarkable thing is that we just keep learning more," Walker told the website.