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"Protecting the health and informed consent rights of children since 1982." =============================================

Note from BLFisher:

 

This article details the biological factors which make it so difficult to

develop an AIDS vaccine that will be safe and effective for all individuals

and all populations in the world. And yet, because the past is prologue,

there is no question that when an AIDS vaccine is developed and licensed as

safe and effective, it will be mandated for everyone.

 

http://www.SeattleTimes.com

Sunday, August 26, 2001 - 12:00 a.m. Pacific

 

Scientists buoyed by series of tests for AIDS vaccine

 

By Daniel Q. Haney

The Associated Press

 

ATLANTA  The scientists trying to create a vaccine to prevent AIDS suddenly

seem optimistic, even bullish, words not heard much in this perennially

gloomy field.

AIDS Q&A

 

 

Q: How soon do researchers think an AIDS vaccine might be available?

A: If the only one in large-scale testing fails, it will be at least six to

10 years.

 

Q: Will it prevent everyone from contracting AIDS?

 

A: Probably not. The most-promising vaccines under development don't prevent

HIV infection; most would keep the virus under control so it doesn't cause

illness.

 

Q: Would the vaccine prevent AIDS from spreading?

 

A: Probably not completely. Usual safeguards using condoms and drug users

not sharing needles  still would be recommended.

 

Q: Would such a vaccine be given to everyone?

 

A: No. Until a vaccine is perfected and found to prevent HIV infection, it

probably would be used on target populations at very high risk, such as drug

addicts.

 

 

The Associated Press

 

 

Many researchers for the first time appear confident a vaccine is possible.

 

More than anything else, monkeys are responsible for the change in attitude.

Scientists for two decades have used monkeys to test theories about AIDS

treatment and prevention. But a vaccine that would safely protect a monkey

from dying of AIDS was elusive. Until now.

 

Now there are monkeys such as Godot, a blond, 4-year-old macaque living in

the level-2 biohazard-containment facility at the Yerkes Regional Primate

Research Center on the leafy fringes of Emory University. More than a year

ago, Godot received a big dose of SHIV, an especially nasty, lab-made

amalgam of HIV and SIV, the human and monkey versions of the AIDS virus. He

ordinarily would have been dead in six to eight months.

 

Anyone entering Godot's living space must dress head to toe in protective

clothing, because SHIV circulates in his bloodstream. But his curious, alert

stare at visitors peeking through a window shows he is outwardly unscathed.

Godot is infected, but otherwise healthy.

 

Seven months before he was infected, Godot received an experimental new AIDS

vaccine, one that experts hope will be the model for a shot to control the

worldwide epidemic.

 

Two other variations have been tested on monkeys at Harvard Medical School

and Merck, the U.S. drugmaker, with similar results. The Merck vaccine is in

first-stage human testing, and the Yerkes and Harvard versions should start

within six months.

 

Vaccine discovery has been a notoriously discouraging area of AIDS research.

But, thanks to this impressive series of monkey experiments, many

researchers have grown upbeat in the past year.

 

An AIDS vaccine is still no sure bet, they say. But many think they are at

least on a rational path toward finding one.

 

Chances of success? "Very good," predicted Harriet Robinson, who oversaw

experiments involving Godot and about 80 other monkeys. Why? "Because of the

monkeys," she said. "We are not all that different from monkeys."

 

How different humans are from monkeys is key and a matter of debate among

scientists.

 

Still, similarities are striking. In both monkey and man, the virus destroys

its victims' cells, a crucial branch of the immune defenses. In monkeys, the

vaccine seems to blunt this attack. Maybe it will in people, too.

 

"Suddenly there is a sense for the first time that perhaps we have the tools

in hand today to make a substantial impact on the dynamic of the HIV

epidemic," Harvard's Norman Letvin said. "Now there is an absolute stampede

to get these technologies into humans and ask the question: Can we translate

these monkey findings into the human situation?"

 

Researchers hope to know soon whether these experimental shots launch the

same, early immune-system defenses seen in vaccinated monkeys. This would be

an encouraging hint of the vaccine's eventual power. Some answers could be

offered at an international AIDS vaccine conference early next month.

 

However, vaccine development is frustratingly slow. Even if all goes

flawlessly, Yerkes' Robinson estimated that large-scale experiments with her

vaccine won't begin until 2005. Many estimate these vaccines are still a

decade or more away.

 

With clear answers so far off, is all this optimism realistic?

 

"I ask myself whether it is justified based on the science," said Peggy

Johnston, assistant director for AIDS vaccines at the National Institute of

Allergy and Infectious Diseases. "And my conclusion is yes."

 

One reason is that scientists have lowered the bar. Until now, all useful

vaccines prevented infections. However, the human immune system cannot turn

back an HIV infection, and no one knows how to make a vaccine that

accomplishes something the human body cannot do for itself.

 

So the new vaccines are designed to accomplish the next-best thing: Train

immune defenses to hold an infection in check without preventing it

entirely.

 

"For a long time, people assumed that the only successful vaccine would

completely prevent infection," said Robert Schooley of the University of

Colorado. "The new studies suggest that a vaccine might also have a

moderating influence on the disease process itself."

 

Scientists agree that blocking an infection requires the production of

powerful antibodies. This is how standard vaccines work: They show the

immune system a protein that is unique to the germ. If the bug ever enters

the body, the defenses will blaze back with antibodies that latch onto the

protein, blocking the germ and destroying it.

 

HIV, however, is a moving target. It mutates so rapidly that it constantly

changes proteins on its surface. So a vaccine that triggers an attack

against one strain of HIV may be powerless against another. Furthermore, the

virus covers its surface with sugar, which hides its proteins from

antibodies.

 

Back to basics

 

When all of this became clear in the 1990s, scientists went back to basics.

How is it, they asked, that people often live with HIV for eight or 10 years

before falling sick with AIDS? And why do some never seem to become ill at

all?

 

The answer turns out to be killer cells, another line of defense against

germs. Unlike antibodies, which guard against free-floating microbes, killer

cells recognize infected cells and destroy them.

 

HIV's favorite target is a blood cell called the helper cell. This

complicates matters enormously, since one of the helper cells' most

important jobs is nourishing and managing killer cells.

 

In the first days of an infection, HIV burrows into helper cells by the

billions, taking over their machinery, forcing them to build new copies of

the virus and obliterating them in the process.

 

Eventually, though, killer cells awaken and destroy most of the infected

cells before they can release more virus. Virus levels fall and then level

off.

 

In the years that follow, the war is nearly a stalemate. The body produces

new helper cells almost as quickly as the virus ruins them. But their levels

gradually slide too far. At this point, virus-killing drugs can restore the

balance, but otherwise the result is AIDS and death.

 

New vaccines are designed to start the opening counterattack by killer cells

more quickly, so fewer helper cells become infected, and the virus

eventually plateaus at a much lower level.

 

"By doing relatively subtle things during the first hours to weeks of

infection, we think we can have a dramatic payoff in allowing the body's own

immune response over the long haul to contain this viral infection," Letvin

said.

 

Instead of dying from AIDS, vaccinated people who become infected might live

with the virus for decades or even a lifetime.

 

Details of the vaccines developed by Yerkes, Harvard and Merck differ, but

all involve the same strategy: First come injections of several HIV genes,

which are taken in by muscle cells that use them as blueprints to make viral

proteins. Next comes an immune-system booster, such as a smallpox virus that

has been rebuilt to carry some of the HIV genes. The ultimate goal is still

a vaccine that will block HIV infection. Experts think a vaccine is the only

thing that will tame an epidemic that has killed 20 million people and

infects 15,000 more daily.

 

 

While much of the attention is on novel strategies, a more traditional

vaccine is in final-stage testing. The AIDSVax, developed by VaxGen of

Brisbane, Calif., has been given to 7,900 volunteers in North America,

Europe and Thailand.

 

The vaccine is made from the outer wrapper of the AIDS virus and is intended

to trigger antibodies to prevent infection. Many AIDS experts are skeptical,

because the approach has been disappointing in monkeys, and some early

volunteers contracted HIV after being vaccinated.

 

Promising data

 

However, VaxGen's president, Donald Francis, says more promising data from

chimp experiments suggest it has as good a chance as any other approach.

Researchers will take their first look at the results in November.

 

Next in development is a vaccine by Aventis Pasteur of Paris. It consists of

a canarypox virus engineered to carry HIV genes, followed by a boost with

AIDSVax. The Walter Reed Army Institute of Research plans to start testing

on 16,000 volunteers in Thailand next summer.

 

 

Still, a few dozen healthy monkeys such as Godot do not prove an AIDS

vaccine is on the horizon. Some in the field worry that the wish for one has

dissolved healthy scientific skepticism.

 

"We tend to swing from momentous lows to momentous highs in the AIDS field,"

said Mark Mulligan of the University of Alabama at Birmingham. "We may be in

an Alan Greenspan time of irrational exuberance, because we need this so

desperately."

 

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