TOPICS > Health

AIDS Breakthroughs

February 2, 1999 at 12:00 AM EDT


PHIL PONCE: A major conference on AIDS is being held in Chicago this week, and already several important new studies have been released, including one that may have solved the riddle of the origin of the AIDS virus. Here to tell us about that and more are Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, and Laurie Garrett, a medical writer with Newsday. Welcome both.

PHIL PONCE: Dr. Fauci, if you would, briefly summarize what it is the researchers found regarding where AIDS comes from.

DR. ANTHONY FAUCI: Well, investigators were able to show that it is highly likely, not yet definitive but highly likely that the H.I.V.-1, which is the predominant virus that infects man, actually originated in the chimpanzee and probably co-evolved with the chimpanzee during the evolution of the chimp. And sometime probably decades ago there was a jump in species from the chimpanzee to humans, probably more than one jump, at least maybe three separate ones that were documented, which is now getting us closer to solving the mystery of what we suspected all along, that the origin of H.I.V.-1 actually did come from a chimpanzee. So it’s of considerable historical interest. The importance of it remains to be determined when we have tests, for example, that try and figure out why the chimpanzee, who’s been infected for such a long period of time, does not apparently get ill from the virus. And that’s the scientific question that needs to be answered.

PHIL PONCE: Before we get to the scientific question, just to make sure we understand how that jump you talked about was made, chimpanzees in that part of Africa are hunted for food and hunters will dress them out in the field and it’s a bloody business where — and the belief is what, that that’s how the virus entered the bloodstreams of humans?

DR. ANTHONY FAUCI: It’s very likely that though during the period of time when you are butchering and preparing the meat that you get nicks and cuts in your hand, and the most like likely explanation is that that’s how it gets transmitted, because we know, as a matter of fact, from our experience with H.I.V. that when you have cuts that get into contact with exposed blood that you can actually transmit it. And it is likely that’s how the first transmissions came from the chimpanzee to human. And then once it was in human, it was spread by sexual contact.

PHIL PONCE: Laurie Garrett, one of the things Dr. Fauci said earlier was the hope or the possibility that if scientists can figure out how it is chimpanzees were able to live with the virus without getting sick that the same kind of lesson might be applicable to humans.

LAURIE GARRETT: That would be a wonderful possibility, no? There’s only a 1.5 percent DNA difference between humans and chimps. So whatever it is, if something is conferring protection to those chimps, it’s something very subtle, something very small, and possibly something that, well, we can get to the bottom of and find that difference between chimps and humans. And so that’s very exciting.

PHIL PONCE: Laurie Garrett, what are the next questions that people have to ask as they explore– what are the next questions – you were having trouble with your ear piece, it seemed — what are the next questions people have to ask to figure out if in fact that promise is there?

LAURIE GARRETT: Well, it seems a key thing is being able to observe large numbers of wildly infected chimpanzees to see how are they getting infected. We assume it’s the same ways that we see in monkeys, which is mostly sexual, but we don’t know if that’s for sure, and also some idea of how they’re protected. But really Dr. Fauci can answer that question much more than I can.

PHIL PONCE: Dr. Fauci.

DR. ANTHONY FAUCI: If it’s something immunological, namely, if there’s something within the immune system of the chimp that’s protecting the chimp from progressing to a clinical disease whereby they’re still infected, if that particular factor or factors can be identified, then that could be a target either for the development of a vaccine that can induce this particular factor in people who are uninfected, or in infected individuals something that could actually induce the enhancement of this factor so that the people who are infected can have the same sorts of protection that apparently the chimp has. So it really is a question of pinpointing what are the factor and factors that allow the chimp to be able to live with the virus and not progress to clinical disease. That’s the really first important scientific question that needs to be asked and answered, hopefully.

LAURIE GARRETT: I think there’s another scientific question that’s very exciting to look at because working backwards, creating a sort of backwards family tree, Dr. Betty Korber, Los Alamos, has computed that probably this event, this jump from the chimps to humans, occurred sometime between about 1924 and 1946. So then you can begin to ask questions, what were the human activities in this part of the world that would have put them in contact with the chimpanzees, that would have facilitated this event occurring? And beginning to answer questions like that has implications not just for H.I.V. but for a whole host of microbes that may make the jump from chimpanzees and have in the past made the jump from chimpanzees or monkeys to human beings.

PHIL PONCE: So Laurie Garrett, if I’m understanding you, you’re saying that in possibly the same way that humans started encountering those host animals that were carrying these viruses, that, what, there are other – potentially there are other viruses or other hosts out there that humans might be encountering in the same way?

LAURIE GARRETT: Absolutely. Absolutely. We are moving into rain forest areas at pell-mell pace now. But we started our big steps in these areas during the colonial days. And that would certainly coincide with the time period we’re talking about, in the 1930’s, for example, beginning to exploit resources in those countries. So whatever happened, however that jump event occurred, must have coincided with human historical events going on in that area. And, you know, it’s interesting that Gabon Cameroon area and the Thai rain forest is also a site that has brought us two chimpanzee outbreaks of the deadly Ebola virus, which causes a hemorrhagic fever disease and whatever harbors that virus normally is in that same region. And there are untold possibilities of other microbes that may be either in the chimps or monkeys or primates in this same time part of the world.

PHIL PONCE: Dr. Fauci, let’s move on to another study. There was a study having to do with the way in which the transmission of AIDS takes place between mother and infant and some new approaches to address that. Tell us about that.

DR. ANTHONY FAUCI: Well, we know from studies done a few years ago that you can substantially block — not completely but substantially — the transmission from an infected mother to the infant by treating the mother for a considerable period of time during the pregnancy and then treating the infant immediately after the pregnancy for a few weeks. Although that works, that’s really not feasible for developing countries that can’t afford that amount of anti-viral drug. The study that was spoken about today is a study in which the drug — two drugs, AZT and 3-2-C, were given at the very latter part of pregnancy for the last three weeks and then for a week to the mother and to the infant thereafter, and the decrease in the transmissibility was substantial. In fact, if you even just gave it at the very time of delivery and to then again to the mother and the infant after delivery, you were still left with a significant decrease in the transmissibility. That’s really very important because the very long protracted therapy just is not feasible in countries that can’t afford it. If this indeed holds up to be true, then we can talk about the possibility of having a significant impact on the transmissibility of the virus from an infected pregnant woman to the infant in countries that apparently cannot afford this very protracted course of therapy. So that’s an important finding.

PHIL PONCE: And Laurie Garrett, speaking of medication and the effectiveness of drugs, some new research on the — on the, what, apparent increasing lack of effectiveness of some of drugs?

LAURIE GARRETT: Well, there are several papers here showing that what’s called HAART — highly active anti-retroviral therapy — this combination cocktail therapy that has been responsible for some tremendous breakthroughs in declining death rates and progression to AIDS rates and so on in this country is not an absolute thing. Even before we came to this meeting, at any number of AIDS-associated meetings, we’ve been hearing more and more reports about people failing on heart therapy. And basically what seems to happen is that one of two things eventually catches up with them — either the toxicity of the drugs and particularly their effects on their livers and GI tract, or the virus acquires the capacity to resist the drugs and then to resist another set of drugs and then another set so that the virus becomes more and more capable of withstanding exposure to the very medicines meant to wipe it out. And that seems to be a time-valued event. In other words, the longer you’re on these drugs, it generally seems the greater the likelihood that resistance will emerge, you’ll have to switch and each time you switch — try another drug cocktail — it seems that the time to the necessity to switch again shortens. This is speaking in very generalized terms, of course. There are patients for whom HAART therapy is very, very successful and the first round works.

PHIL PONCE: Dr. Fauci, there was a feeling at some point that this mix of drugs was increasingly effective and there was a sense of optimism. Was that misplaced?

DR. ANTHONY FAUCI: Well, I think the optimism about immediate eradication of the virus certainly was misplaced a couple of years ago. Now we’re seeing the sobering realization that although things are still much, much better than they were before these combinations of drugs were available, this concept that in the vast majority, 90 percent of the people, then the problem is over, you’re just going to treat them and then that’s it — we’re seeing now, as was reported from a number of studies, one from Alabama, that the original percentage, 85/90 percent is really down now somewhere around 60 percent or less, such that each month or year, or what have you, that goes by, more and more people break through as Laurie had said. That fortifies and underscores the need to develop new and better drugs, not only that are as powerful, if not more powerful, than the ones we have but also ones that are less toxic and more user friendly.

PHIL PONCE: Dr. Fauci, Laurie Garrett, that’s all the time we have. I thank you both very much.