some of you (zob) didn't watch the video. They genetically modified the HIV virus so that it DOESN'T kill immune cells, only modifies (programs) them to become immune cells that kill the virus. They took out the code in the HIV's DNA that makes cells replicate it and replaced it with something that boosts the immune power of the cells. And look at that girl in the video. She had a terminal cancer and was going to die very soon and then they injected her with that virus. Now she's alive, healthy, and cancer-free. The sickness she got was her immune system going into overdrive to defeat the cancer and it worked.