A genetically engineered live attenuated HIV vaccine has been developed at the University of Western Ontario, and US FDA approval was announced in mid-December of 2011. The vaccine has already been proven to stimulate immune response in animal subjects, and Phase I testing in HIV-infected human subjects began in January. The efforts of UWO and Sumagen Canada were also recently bolstered by a $728,000 boost from the Bill and Melinda Gates Foundation.
I'll try and dig up more information on how exactly this vaccine works, and what the genetic modification entails. I'm sure we all remember the Sabin vaccine controversy...