story
cautious optimism in hunt for AIDS vaccine
originally aired April 17, 2003
Severe Acute Respiratory Syndrome has been grabbing the health headlines of late, but work continues on that other disruptive global epidemic: AIDS. It's been a little more than a month since a company named VaxGen released the results from the world's first full-scale human trial of an H-I-V vaccine. The company says the vaccine may have provided some protection for people from a few ethnic populations, but for the most part it was a failure. The Health Show's Greg Dahlmann tells us what's next in the hunt for a vaccine against AIDS.
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Talk to people in the vaccine business and they’ll tell you the results from the VaxGen trial are disappointing... but the findings aren’t really discouraging anyone. Dr. Patricia Fast is the medical director for the International AIDS Vaccine Initiative -- or IAVI... a non-profit that’s trying to help fund and coordinate research in this area. She says one good thing to come out of the study was that VaxGen demonstrated you could run a solid, responsible AIDS vaccine clinical trial.
{PF: move on} :10
“But the results were clear that this particular approach wasn’t the answer and that leaves the field free to move forward on different approaches.”
And that’s nothing new... the global AIDS vaccine effort has been based on finding new and different approaches to do the job.
The classic method of developing a vaccine involves using a dead or weakened form of the target virus. For example... the flu shot is actually made of dead viruses that will give your body’s immune system a good idea of what it will probably encounter during flu season. That head start helps you fight off the infection. The problem is… H-I-V won’t play along with that method. For one thing... it doesn’t prompt the body to mount a response when its dead... and doctors aren’t confident they can weaken the virus enough to safely administer it to people. So, researchers have focused on making an AIDS vaccine out of just parts of H-I-V.
In the case of VaxGen... that meant trying to use the protein that forms the virus’ outer coating to help the body generate something called neutralizing antibodies... they’re kind of like chemical handcuffs for microbes. But H-I-V is a tough opponent... in large part because it’s highly variable. There are many different strains roaming the world and they’re changing slightly all the time. So, it’s really hard to get a vaccine that will help the body to recognize all these different strains... which are – in a sense – all wearing slightly different coats. It’s so daunting a challenge... that Dr. Robert Gallo – one of H-I-V’s co-discovers – says by the end of the 1980s... most researchers had given up on the idea.
{RG: field was depressed} :14
“Then the field kind of became depressed... and many people left it. Actually, I temporarily left it as well... we always had something part time in it... but I thought that I thought that ‘oh my god’ this just isn’t something we’re getting on top of”
The researchers who stayed in the field turned their attention to a new approach. If doctors couldn’t get the body to develop neutralizing antibodies... maybe they could train a different part of the immune system to do the job. In the body’s immunological army... there are soldiers called killer T-cells which – as you might guess – like get to rough with microbial invaders. In most cases... when the body confronts a foreign microbe... it’s able to tag the offending party and the T-cells come along to chew it up. H-I-V escapes this fate because it never gives the immune system a chance to call in the killer T-cells. But... if researchers could train these cells before H-I-V entered the body... maybe that would tip things in favor of the immune system.
IAVI’s Dr. Fast says there are a lot of theoretical reasons a vaccine aimed at killer T-cell response would also jump that long standing stumbling block... H-I-V’s ever changing coats.
{PF: DNA vac} :20
“They can see a lot of small pieces of the virus. They can see pieces that are inside... that are so key to the structure of the virus that it would be really hard for the virus vary them. So, they’re less likely to change as the virus tries to change to escape the immune system.”
Dr. Fast says the idea is very promising... it’s just a matter of making it all work. One of the primary issues is figuring out the best way of introducing these parts of H-I-V to the immune system. There are basically two different routes... you could inject the naked pieces directly into the body... or you could integrate the parts into a harmless virus or bacterium. There are a number of vaccines based on these approaches... some of which are heading into human trials. The results are still four to five years off, though.
As promising as the T-cell aimed vaccines are... don’t count out the antibodies just yet. During the last ten years scientists have gotten a much better understanding of how H-I-V works itself into human cells. It turns out that when the virus links up with a cell... its coat changes shape at the very last moment... and when that happens... it exposes what amounts to a chemical target common to all forms of H-I-V. Robert Gallo and a team of researchers at the University of Maryland’s Institute of Human Virology think this information presents a an opportunity. They’re one of a handful of teams working to find a way to get the body to recognize that target as a place for aiming neutralizing antibodies. Dr. Gallo says people are optimistic about the approach... but cautiously so.
{RG: learned respect} :13
“If this was 1985, 1984 this was the holy grail... what we were looking for. It would then be greeted with enormous excitement at that time. But since then we’ve learned respect for the virus, so we don’t get so excited until we get the results.”
Dr. Gallo says his team is eager to get its vaccine into human trials... but they’re struggling with the decision about where to stop. He says new information comes along all the time and they want to be certain they’re sending the best candidate into trial.
The ultimate solution to the AIDS Vaccine problem may not be the T-cell approach or the recently discovered antibody target... it may be both. Doctors have found that the best treatment for people already infected with AIDS involves a number of different drugs aimed at different aspects of the virus. Dr. Peggy Johnston is the assistant director for AIDS vaccines at the National Institute of Allergy and Infectious Disease.
{PJ: might take combo} :14
“If that is any indicator for us in vaccines, then finding ways to attack the virus in as many places as we can may prove more effective than one that does just one thing or another.”
It’s just going to take time to figure out what works. It may seem like researchers have already had a lot of that... the medical community has been tracking AIDS since the early 1980s. But Peggy Johnston says history shows us vaccine research is a slow process... and the fact we don’t have a vaccine yet for AIDS doesn’t mean the field is off course.
{PJ: optimistic about min vac} :21
“Given the number of people working on this, the number of products in the pipeline... I’m optimistic that we can attain a vaccine that at a minimum may not prevent infections, but could allow people to live a normal healthy life and prevent them from spreading the virus to other people.”
Dr. Johnston says one key to keeping this momentum moving forward is money. Just a single vaccine candidate can take tens of millions of dollars to develop and test. And there are currently about 15 solid candidates already in the running. Private funding has increased over the last five years... thanks in large part to the Gates Foundation. But Peggy Johnston says government also needs to keep the dollars flowing because in the end... the marketplace will probably not provide enough incentive for drug makers to fund the necessary research.
Of course, when you talk about public money, you have to talk about politics. It’s a sign of the scale of the AIDS problem that the disease has become a major political issue around the world. Just this January, we heard President Bush talk about it in the state of the union. The International AIDS Vaccine Initiative’s Patricia Fast says there’s a good reason for governments to pay attention.
{PF: stable world} :07
“From a global standpoint, if we want a world that’s safe and economically stable... we need to get rid of HIV.”
It’s estimated that almost 60-million people worldwide have been infected with H-I-V. Twenty-two million have died as a result.
For the Health Show... I’m Greg Dahlmann.