Why developing an HIV vaccine is so hard

In an interview with Scientific American, Anthony Fauci, the director of NIAID (National Institute of Allergy and Infectious Diseases), discussed why developing a vaccine for HIV/AIDS is so challenging. The short version is that unlike other diseases, HIV doesn't seem to illicit a "neutralizing antibody response"; without this response, we have no natural model of infection which can be used as a basis for building a vaccine. This really is an article worth reading, as Fauci goes to great lengths to explain why after nearly three decades of research, an effective vaccine still remains elusive.