A tenth of children have a "monkey-like" immune system that stops them developing Aids, a study suggests.
The study, in Science Translational Medicine, found the children's immune systems were "keeping calm", which prevented them being wiped out.
An untreated HIV infection will kill 60% of children within two and a half years, but the equivalent infection in monkeys is not fatal.
The findings could lead to new immune-based therapies for HIV infection.
The virus eventually wipes out the immune system, leaving the body vulnerable to other infections, what is known as acquired human immunodeficiency syndrome (Aids).