Yeast as in bear, wine, and bread yeast may be used to vaccinate against HIV and maybe even cancer. It was something along the lines of them implanting a bit of HIV DNA inside the yeast bacteria. This bacteria was ID'd as a HIV cell, which spurrs production of anti-HIV T-cells. These T-cells attack to infected and mutated immunio cells that have HIV and tell them to commit suicide. I don't have a link, but you can probably go to CNN, Fox News Channel, or MSNBC for more info. Though someone might be intrested.