Altering Virus Coats May Halt Flu Spread

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Altering Virus Coats May Halt Flu Spread

By LAURAN NEERGAARD, The Associated Press

Friday, February 2, 2007; 7:48 PM

WASHINGTON -- Making a small change in the outer coating of the lethal

1918 flu virus was enough to stop it from spreading, a discovery that

may help scientists monitor today's bird flu and other influenza

strains for signs of the next pandemic.

The 1918 pandemic was triggered by a bird virus that mutated into one

that could attack humans, going on to kill a staggering 50 million

people worldwide in a matter of months.

To learn what caused that catastrophic bird-to-human transformation,

scientists with the Centers for Disease Control and Prevention turned

back the clock: They worked with recreated batches of the actual H1N1

flu strain that spawned the 1918 pandemic, but they altered two spots

in a key protein to make that virus a little more birdlike again.

Then the researchers dripped the altered virus into the noses of

ferrets, who catch and spread influenza like humans do.

The infected ferrets still sickened and died as the flu ravaged their

lungs. But remarkably, they didn't infect healthy ferrets caged right

next to them, the CDC team reports in Friday's edition of the journal

Science.

Why not? Most flu spreads when an infected person coughs or sneezes

out droplets of virus. Ferrets infected with the altered 1918 virus

didn't sneeze at all.

The research suggests that for a new flu strain to become a pandemic

threat, a protein called hemagglutinin that coats the virus' surface

must prefer attaching to cells found mostly in the human nose and

windpipe, where it can be sneezed easily.

That's good news when it comes to the notorious Asian bird flu that

scientists are watching anxiously today. That strain known as H5N1

bears hemagglutinin _ the H in its name _ that still prefers cells

mostly found in the gastrointestinal tracts of birds. While it has

killed at least 164 people worldwide and killed or prompted the

slaughter of millions of birds across Asia since late 2003, the H5N1

virus can't yet spread easily from person to person.

" This is very, very elegant work, " said Dr. Schaffner, an

infectious disease specialist at Vanderbilt University who advises the

federal government on flu issues.

" It may not be exactly the same mutations that would change an H5

virus, " Schaffner cautioned. Still, he said, " We appear to be

narrowing down our understanding of the kinds of mutations it might

take to change a bird-specific virus to one that could be transmitted

readily among humans. "

The CDC's next step, in fact, is to study these same changes in

hemagglutinin amino acids, the protein's building blocks, in H5N1.

But it will almost certainly take additional genetic changes to turn

the H5N1 bird flu into a major human killer, changes that probably

involve other proteins than just hemagglutinin, contends lead

researcher Dr. Terrence Tumpey, a CDC microbiologist.

" I think that researchers may discover that the combination of genes

needed is maybe unlikely to occur in nature, " he said.

http://www.washingtonpost.com/wp-dyn/content/article/2007/02/02/AR2007020201484.\

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This undated image provided by the journal Science shows a negative

stained transmission electron micrograph (TEM) recreating a 1918

influenza virions that were collected from supernatants of

1918-infected Madin-Darby Canine Kidney (MDCK) cells cultures. (AP

Photo/ Goldsmith,CDC, Science)