A recently discovered, natural immune response to HIV may become a vital piece in the larger vaccine puzzle. Researchers from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) consortium have identified two women whose immune systems reacted to HIV by producing “broadly neutralizing antibodies” that can kill 88 percent of the virus types found around the world. After they were initially infected with HIV, the women first produced less potent antibodies, which pressured the virus to cover a key point of its surface with sugar, or “glycan.” This point became an Achilles’ heel for HIV after the women then developed broadly neutralizing antibodies that targeted the site. The researchers hope that a series of vaccinations could one day mimic this evolution, but without the presence of the virus—empowering immune systems to effectively battle HIV on their own.