RAY SUAREZ: In the global war on AIDS, there's a new southern front in Peru. And, in the country's capital, Lima, an international investigation is taking shape.
Juan Carlos Hurado, a doctor specializing in treating HIV-infected patients, examines a very rare HIV-positive patient, one that is perfectly healthy. And the patient, who asked that we only use his first name, Hans, isn't just healthy now. In the eight years since he tested positive for HIV, Hans has never been sick and has never been on medication.
HIV PATIENT (through translator): I feel normal, just like anybody else, and I just live as normal as possible.
RAY SUAREZ: Hans' unusual ability to stay healthy without medication has placed him in a special class of HIV-infected individuals researchers call elite controllers. This select group has the ability to control the HIV virus by suppressing it.
Peru has identified 600 so-called elites, whose HIV infections have not progressed into life-threatening AIDS, and researchers are looking at them and other identified elites from around the world to understand why.
Dr. Bruce Walker at the Ragon Institute in Boston is heading up the elite investigation. It's a joint venture with MIT, Harvard, and Massachusetts General Hospital.
DR. BRUCE WALKER, The Ragon Institute: These are people that have no adverse effects from their infection that we can tell. They -- they have -- they feel completely healthy. They don't need to take medications. Their CD4 counts, which is a measure of immune functions, that immune function is normal. And some of these people, we now know, have been infected for over 30 years, and yet are still doing entirely well.
RAY SUAREZ: Walker hopes clues will emerge from studying elite controllers that will ultimately lead to an HIV vaccine.
DR. BRUCE WALKER: If we had a vaccine that could keep the virus level as low as these people keep it, we would expect them to have much less chance of transmitting to somebody else and much less chance of any kind of disease progression themselves.
And that would basically reverse the epidemic, if we could do that. So, our goal, in studying these elite controllers, is to find out how it is that they're able make HIV irrelevant to them, and are able to control it on their own, because we believe that -- that therein lies the solution that we're looking for to the HIV epidemic.
RAY SUAREZ: So, how did Peru end up being one the few centers of research around the world trying to figure out how these people control their virus?
Well, for one thing, the government has been urging testing for years, so a lot of people know their status, and there's a well-identified set of what are called elite viral controllers. For another thing, there's geographic and racial diversity here.
DR. BRUCE WALKER: I believe what we will find is something that's common across these different -- across these different groups. And that's certainly the hope, because what you would ultimately like to do is have a vaccine that you can pull off the shelf and give to a patient here in Boston, and you can pull the same vaccine off the shelf in Peru or South Africa and give it to a patient there and have it be equally protective.
RAY SUAREZ: Globally, an estimated 33 million people have HIV, a deadly condition for which there is no cure. Researchers suspect that one in 300 infected individuals could be elite controllers.
But, because elites are healthy, they are less likely to realize they have contracted HIV. In fact, most are living life unaware of their condition. This makes them hard for researchers to find. They are also much less likely to infect others.
Hans only decided to get the HIV test after he found out his partner was sick with the virus. Now aware of his unusual status, he hopes others will follow his lead.
HIV PATIENT (through translator): It would be better if more people like me volunteered for the investigation, so that we can find some kind of cure for this illness.
RAY SUAREZ: Twenty-nine-year-old Peruvian Juan is an elite controller with a different experience. When he first contracted the virus four years ago, Juan got sick. But almost as quickly as it appeared, the infection retreated, falling to almost undetectable levels. That's when doctors asked Juan to participate.
HIV PATIENT (through translator): I know it is a responsibility for me, because doctors don't understand. And maybe, through me, they can understand why I have this special response.
RAY SUAREZ: Why was Juan's immune system able to deliver a punch so strong, it knocked the HIV virus into submission?
To understand that response, doctors have turned to the technological wizards of MIT. Here at the Massachusetts Institute of Technology, Darrell Irvine and his crew are using new imaging technology so precise, it can mimic how a single cell can kill an HIV target.
DARRELL J. IRVINE, Massachusetts Institute of Technology: The thing that we have seen is that that first kill that they carry out, the first execution of an infected cell that they carry out, is extremely efficient. And with almost 100 percent effectiveness, if they see that first target they encounter, they kill it very quickly.
So, what, to us, that suggests is that what may be needed, what may distinguish the elite controllers is this very effective first attack, and that what you would want in a vaccine is a large number of these cells to quickly come in and rapidly attack and kill that first wave of infected cells at the site of infection.
RAY SUAREZ: The critical cells are called killer T cells. And rather then putting them in a lab dish together with HIV, where the T cells have an easy target, Irvine has figured out a way to recreate what really happens in the body and measure how fast the elite T cells move from one target to another.
DARRELL J. IRVINE: They begin killing them, so you see them turning green as they are getting killed. And you see many fewer of these target cells running around, because they have all been grabbed by the T cells.
You also, noticeably, see that the T cells themselves have stopped moving as soon as they have grabbed their target. And we think this is part of the key biology that we're trying to understand here. How long do these T cells remain stopped? How long does it take them to kill one target and then move on to another? And how is it that they track down and kill these very fast-moving target cells that are able to move as rapidly as they can?
RAY SUAREZ: The study has recently received a boost from the Bill and Melinda Gates Foundation to expand its research. The foundation also funds the NewsHour's global health coverage.
Doctors hope these early steps in understanding the molecular mechanics of HIV are early steps in finding a vaccine that has eluded researchers for 30 years.