A unique change in the outer covering of the virus allowed for antibodies to attach and neutralize 88% if HIV types around the world. This is known as a broadly neutralizing antibody response and was due to the body pressuring the virus to change its surface coating to have a sugar (glycan) ‘tag’ in the 332 position which then allowed the immune systems antibodies to attack it.
According to Professor Salim Abdool Karim, president of the Medical Research Council, “Broadly neutralizing antibodies are considered to be the key to making an AIDS vaccine. This discovery provides new clues on how vaccines could be designed to elicit broadly neutralizing antibodies.”
Though, because the weak point at position 332 is only in ~70% of the subtype C viruses (the subtype most common in Africa), antibodies will need to be developed that can target more glycans on the virus.
Via nature.com in the article “Evolution of an HIV glycan-dependent broadly neutralizing antibody epitope through immune escape”