It turns out that the half-dozen amino acid variants that have protected Massie against AIDS are the same ones the Harvard-led team has found in others of European descent, those of African descent and Hispanics.

With the discovery, a number of other findings are falling neatly into place.

For instance, scientists have previously shown that people whose immune systems can control HIV are more likely to have certain “flavors” of an important immune trait called HLA (for Human Leukocyte Antigen). The HLA system allows the body to distinguish between its own healthy cells and those infected by foreign invaders, such as viruses.

But until now, scientists didn’t know what it was about the more favorable HLA subtypes that conferred protection against HIV.