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Sun, 18 Dec 2005 17:27:18 -0800 (PST)

U.S. Team Will Test Live-Virus Bird Flu Vaccine

 

 

 

 

 

Avian flu outbreaks may no longer be confined to bird populations.

Looks like that the bird flu is about to get a helping hand in jumping

the species barrier. W.

 

 

 

http://www.healthcentral.com/newsdetail/408/1507443.html

 

 

U.S. Team Will Test Live-Virus Bird Flu Vaccine

 

Researchers at the U.S. National Institutes of Health will soon

recruit 30 human volunteers to test the effectiveness of a vaccine

containing a live but weakened form of the H5N1 bird flu virus.

 

According to the Associated Press, this flu shot would differ from the

standard influenza vaccines distributed each year because it contains

live rather than killed virus -- potentially rendering it more

powerful in inducing an immune response.

 

The live virus used in the upcoming trial will be genetically altered,

however, so that it won't make people sick. Its hoped that the new

vaccine will prime the volunteer's immune systems to recognize a more

deadly strain of H5N1 if and when it appears.

 

Up till now, avian flu outbreaks have been mostly confined to bird

populations, although experts believe 70 people have died worldwide

from H5N1 infection after picking up the virus from poultry. The real

fear, experts say, is that the pathogen will mutate to allow for

human-to-human transmission. In that case, a pandemic could kill

millions worldwide.

 

Thats why a potentially potent vaccine containing live virus is " a

great, great idea, " flu expert Dr. John Treanor of the University of

Rochester told the AP. " In theory, a live-virus vaccine might actually

work better [than a killed-virus shot], " he said. " We don't know that

because we've never tried one before. "

 

Tests this summer using a vaccine made with another, less dangerous

strain (H9N2), showed the method might be safe and effective. Lead

researcher Dr. Kanta Subbarao told the AP that the trial involving the

weakened H5N1 strain is set to begin in April, pending U.S. Food and

Drug Administration approval.

 

-----

 

2005 ScoutNews LLC. All rights reserved.

 

 

 

http://www.washingtonpost.com/wp-dyn/content/article/2005/12/17/AR2005121700484.\

html

 

 

 

NIH Uses Live Viruses for Bird Flu Vaccine

 

By LAURAN NEERGAARD

The Associated Press

Saturday, December 17, 2005; 11:37 PM

 

WASHINGTON -- In an isolation ward of a Baltimore hospital, up to 30

volunteers will participate in a bold experiment: A vaccine made with

a live version of the most notorious bird flu will be sprayed into

their noses.

 

First, scientists are dripping that vaccine into the tiny nostrils of

mice. It doesn't appear harmful _ researchers have weakened and

genetically altered the virus so that no one should get sick or spread

germs _ and it protects the animals enough to try in people.

 

This is essentially FluMist for bird flu, and the hope is that, in the

event of a flu pandemic, immunizing people through their noses could

provide faster, more effective protection than the troublesome shots _

made with a killed virus _ the nation now is struggling to produce.

 

And if it works, this new vaccine frontier may not just protect

against the bird flu strain, called H5N1, considered today's top

health threat. It offers the potential for rapid, off-the-shelf

protection against whatever novel variation of the constantly evolving

influenza virus shows up next _ through a library of live-virus nasal

sprays that the National Institutes of Health plans to freeze.

 

" It's high-risk, high-reward " research, said Dr. Brian Murphy, who

heads the NIH laboratory where Dr. Kanta Subbarao is brewing the nasal

sprays _ including one for a different bird-flu strain that appeared

safe during the first crucial human testing last summer.

 

" It might fail, but if it's successful, it might prevent hundreds of

thousands of cases " of the next killer flu, Murphy said.

 

FluMist is the nation's nasal-spray vaccine that prevents regular

winter flu. Developed largely through Murphy's lab, it's the only flu

vaccine made with live but weakened influenza viruses.

 

The new project, a collaboration with FluMist manufacturer MedImmune

Inc., piggybacks cutting-edge genetics technology onto that vaccine to

create a line of FluMist-like sprays against different bird flus.

 

" That is a great, great idea, " said Dr. John Treanor of the University

of Rochester, among the flu specialists closely watching the project.

 

Regular winter flu shots are made with killed influenza viruses, and

the government is stockpiling experimental bird-flu vaccine made the

same way. But those bird-flu shots don't work as well as hoped. They

require an incredibly high dose, delivered in two separate injections,

to spark a protective immune response in people.

 

" In theory, a live-virus vaccine might actually work better. We don't

know that because we've never tried one before, " Treanor said.

 

Influenza is like a magician, constantly changing its clothes to avoid

detection, thus making it difficult to develop effective vaccines.

 

Studding the virus' surface are two proteins called hemagglutinin _

the H in H5N1 _ and neuraminidase, the " N " . They act as a wardrobe:

There are 16 known hemagglutinin versions, and nine neuraminidases.

 

They're also what triggers the immune system to mount an attack,

particularly hemagglutinin, the protein the body aims for when it

makes flu-fighting antibodies.

 

When people catch the flu, they usually get H1 or H3 flu strains,

which their bodies can recognize because variations have circulated

among humans for decades.

 

Occasionally, genetically unique strains emerge. Until 1997, H5

strains had never been seen outside of birds. The virus essentially

put on a coat that human immune systems didn't recognize. The result:

Since 2003, a particularly strong H5N1 strain has infected more than

130 people in Asia, killing at least 70.

 

H9 and H7 strains also recently have jumped from birds to people,

although so far they haven't been nearly as dangerous.

 

Researchers hope to create at least one live-virus nasal spray for

each " H " subtype, a project costing about $16 million of the NIH's

annual $67 million budget for flu vaccine research.

 

" The hemagglutinin is the major protective antigen, so that is what

we're focusing on, " explained Subbarao, a molecular geneticist who

heads the project.

 

First on her list are the riskiest known bird flus: H5N1, with human

tests planned for April. H9N2, which recently underwent the first

round of human testing in an isolation ward at Johns Hopkins Bayview

Medical Center. Then an H7 strain, followed by an H6 strain believed

to share genes with the H5N1.

 

" By no means are we confident we're picking the right strain " to make

first, because flu mutates so easily, Subbarao cautioned.

 

She chooses vaccine strains from those that U.S. scientists who are

monitoring influenza in Asia cull from ducks, chickens and geese, and

ship home for research.

 

Subbarao must customize those strains for safe vaccination: First,

using a new technique called reverse genetics, she selects genes for

bird-flu H and N antigens and removes genetic segments that make them

dangerous. Then she adds the remaining gene segments to the regular

weakened FluMist virus.

 

Stocks of the custom virus are grown in fertilized chicken eggs. Each

is then carefully cracked by hand to drain out virus-loaded liquid

that in turn is purified and put into a nasal spray.

 

In a high-security section of the lab, Subbarao dons a biohazard suit

and exposes vaccinated mice to various bird flu strains.

 

Then it's time for human testing _ in a hospital isolation ward just

in case the weakened virus could infect someone.

 

It shouldn't, because " those problems don't exist in FluMist, " said

Murphy, citing studies of regular FluMist in day-care centers where

youngsters routinely pass viruses back and forth.

 

Some studies have found that people can shed virus shortly after

receiving regular FluMist. But, " to spread infection, you'd need much

more (virus) than replicates in the nose, " he said.

 

Hopkins researchers gave the first of Subbarao's vaccine candidates _

the H9N2 spray _ to 30 volunteers last summer. To be sure they

couldn't spread the virus by coughing or sneezing, the volunteers

underwent daily tests of their noses and throats.

 

The vaccine appeared safe. Scientists now are analyzing whether it

also spurred production of flu-fighting antibodies, a sign that people

would be protected if they encountered the H9N2 strain. Subbarao

expects results by February.

 

In April, pending final Food and Drug Administration permission,

Subbarao will put an H5N1 spray to a similar test.

 

Here's the catch: Each flu strain has subtypes. An Indonesian version

of H5N1, for example, was recently discovered that differs from a

Vietnamese strain on which Subbarao's nasal spray _ and the

government's stockpiled shots _ are based. She's now testing whether

her vaccine protects mice against that new Indonesian strain.

 

If a novel flu strain begins spreading among people, how will Subbarao

tell if her stored nasal vaccines are a good match to fight it?

 

NIH also will store blood samples from the people who test those

sprays. Say a new H9 strain sparks an outbreak. That virus will be

tested against those blood samples, and NIH could predict within a day

which spray candidates work. If one does, the government could order

doses manufactured from that frozen stock; if none do, scientists

would have to try to brew a new vaccine.

 

How quickly doses could be manufactured is a different issue. All

influenza vaccines, shots or spray, currently are brewed in chicken

eggs, a time-consuming process that other research is seeking to improve.

 

" These are research projects, " Murphy stresses _ the nasal-spray

concept could fail.

 

But he's optimistic. Live-virus vaccines, he maintains, are better

immune stimulators.

© 2005 The Associated Press

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