by Julie Steenhuysen
December 17, 2009
US researchers have
discovered antiviral proteins in cells
fight off influenza infections, a finding that may lead
to better ways to
make vaccines and protect people against the flu.
They said a family of genes act as cell sentries that guard cells
from an invading influenza virus, the team reported on Thursday in
the journal Cell.
"This prevents the virus from even
getting into the cell," said Stephen Elledge of Harvard
Medical School and a Howard Hughes Investigator at
Brigham & Women's Hospital.
"It is out there fighting the flu all of the time," Elledge said
in a telephone interview.
Elledge and colleagues used a new
research technique called RNA interference in which they
systematically turned off individual genes and then exposed cells to
the flu virus.
Using this method, they discovered a small family of flu-fighting
proteins called interferon-indicible transmembrane proteins
that boost the body's natural resistance to viral infection.
"If you get rid of it (the protein),
the virus can replicate 5 to 10 times faster. What that means is
your cells have a mechanism that can block 80 to 90 percent of
the virus that gets in," Elledge said.
They also showed that if they make the
cell overproduce the protein, they become more resistant to the flu.
"If you crank it up, it really shuts
down the flu," he said.
The team showed that a specific protein
in the family -
IFITM3 - protected against several
viruses, including strains of influenza A now found in seasonal flu,
the West Nile virus and dengue virus.
The proteins did not offer any protection against HIV or the
hepatitis C virus, but lab tests suggested they may defend
against other viruses, including yellow fever virus.
The team showed that if the virus evades this first-line protein
defense and makes it inside the cell, this activates an alarm system
called the interferon immune response that gets pumped out of cells
and alerts the rest of the body to make more of the natural
The findings offer new insights into the body's natural defenses
against influenza and other viruses, Elledge said.
"We really did not know how our
bodies were stopping the flu."
They also may lead to better ways to
protect people from influenza and other viral infections.
"By making this protein be expressed
in poultry or pigs, we can make them resistant to the flu. That
can help protect people by protecting animals from the flu," he
It also may lead to more reliable
vaccine production by creating a more friendly environment for the
virus to grow in chicken eggs, he said.
"If we take our gene away from the
cells in which the virus is growing, it will grow much faster.
You can actually produce vaccines much faster," he said.