. >> reporter: for patients like 49-year-old john caldera, and his physician, steve deeks, the promise of a simple cure is alluring, but remote. >> i've been on at least 10 research studies where it was experimental drugs, and i rolled the dice. i would love to see a future where there is no h.i.v., and i think were very close. >> reporter: but deeks, a clinical professor at u.c. san francisco, isn't so sure a cure is imminent. >> with some of these more aggressive approaches, gene therapy and stem cell transplants and so forth, the risk is much greater, but the reward is also potentially much greater. because it's theoretically possible to cure people with a single intervention, it's possible, i don't think anyone thinks its likely. but its certainly worth trying. >> reporter: deeks says the few patients who have been cured of a.i.d.s. so far lead to one conclusion: >> there's going to be many roads, many paths to take. and its going to be a combination of shock and kill, increase in the capacity of the immune system to kill the virus, and increases in the capacity of the immune syste