Scientists have discovered tiny variations in human cells that make it possible for some HIV-positive people to lead healthy lives without taking medication.

Variations in a protein called HLA-B may make a big difference in the body's ability to fight an HIV infection, said study researcher Dr. Florencia Pereyra, an investigator at Massachusetts General Hospital, Massachusetts Institute of Technology and Harvard University. Variations in HLA-B determine whether a person is an HIV controller, meaning he or she will stay healthy despite being infected, or whether the infected person will need medication to stave off the development of full-blown AIDS.

HLA-B works by derailing HIV once it gets inside cells. When HIV enters the cell, "it builds a factory where more viruses are produced," Pereyra told MyHealthNewsDaily.

The HLA-B protein grabs a piece of the virus and displays it on the cell surface — akin to posting a sign in a factory window, Pereyra said — to alert the immune system the cell has been infected. Then, the body's antibodies can destroy the cell and the virus, she said.

Certain structural changes are what allow HLA-B to grab tightly a piece of the virus and display it on the cell surface. Without these changes, it can't grab the virus the right way or tightly enough, making it impossible for an immune cell to see the "sign" and know to destroy the cell, Pereyra said.

"By finding this specific crucial position in the way the protein holds the virus, we're able to tell unequivocally it's the nature of the interaction … that determines whether a person can mount an immune response that's effective and able to control [the virus], or an immune response that's ineffective," she said.

Researchers from around the world combed the genomes of nearly 1,000 HIV controllers and 2,600 people with progressive HIV infections to find the variations. The search turned up DNA sequences for five amino acids — the building blocks of proteins — within HLA-B that determine whether it can grab the virus and post the signal to the immune system.

About 1 in 300 people with HIV have an immune system that controls their HIV infection without the need for medication, according to the International HIV Controllers Study, through which the HIV controllers for Pereyra's study were recruited.

The finding is the first step in developing a vaccine that could mimic the natural immune response of a cell, Pereyra said, and it opens the door for new investigations to nail down how the mechanism can work so effectively.

The findings might also be applied to other viruses, such as hepatitis C, Pereyra said.

The researchers are now trying to model the interaction between the amino acids of HLA-B and the virus to design a future vaccine, Pereyra said.

The study was published online Nov. 4 in the journal Science.