expensive and safer ways for scientists to develop lines of research
and theories. It should be emphasized that a number of the pathogens
associated with ME and CFS in subsets of patients target the brain and
possibly the brain through the gut. One possible line of research
would be to determine whether other viruses cause the same effects in
mice and to then to use tissue banks to study the brain tissue of
humans.
The authors of this study are also quick to point out that while not
directly causative, an infection might be a contributing factor,
perhaps even precipitating disease in someone already at risk. This
might be because of previous infections, co-infections, severity of
the infection or genetics for example. All of which are variables to
be controlled for in subsequent studies.
Bird flu leaves tracks in brain
Virus might create vulnerability to neurological disorders, research
in mice suggests
By=A0Laura Sanders/Science News Magazine
Web edition=A0: Tuesday, January 31st, 2012
After surviving a bout of virulent bird flu, mice=92s brains show
short-term reductions of a key brain chemical and long-lasting signs
of infection, a new study finds. The research suggests this type of
flu might leave people more vulnerable to brain disorders such as
Parkinson=92s disease.
While most people think of influenza as a disorder of the body,
certain kinds of flu also infect the brain. Recent studies have found
that the bird flu virus known as H5N1, which kills about half the
people it infects, can set up shop in the brain. But exactly what
happens next has been a mystery.
In the new study, scientists at St. Jude Children=92s Research Hospital
in Memphis, Tenn., examined the brains of mice that had survived an
initial H5N1 infection. As in people, the virus kills about half of
mice affected.
=93The first goal with H5N1 was to characterize the neurological
effects,=94 says study coauthor Richard Smeyne.
After being infected with H5N1 isolated from a Vietnamese boy who died
from the flu, some mice initially got very sick, but then seemed to
recover completely after about 21 days. Yet the story wasn=92t so simple
in the brain, the team reports in the Feb. 1=A0Journal of Neuroscience.
Nerve cells that make one of the brain=92s key messengers =97 the
neurotransmitter dopamine, which helps regulate movement =97 shut down
production about 10 days after infection. These nerve cells, which are
the same cells that degenerate in people with Parkinson=92s disease,
=93basically take a time out,=94 Smeyne says. =93All efforts are to
survive.=94
By day 60, the dopamine starts to reappear, and levels are back to
normal 90 days later. Signs of inflammation in the brain remain,
though.
Just three days into the infection, the brains of these mice showed
evidence of a strong inflammatory response, and this response appeared
to linger over time. Proteins that accompany inflammation, and cells
that patrol the brain looking for threats, were still present and on
duty in parts of the brain 90 days after the initial infection.
Scientists don=92t know whether the response ever goes away. =93My guess
is that it=92s permanent,=94 Smeyne says.
He notes that it=92s unlikely that an influenza infection could cause
neurological diseases such as Parkinson=92s, but an infection might be a
contributing factor, perhaps even precipitating the disease in someone
already at risk.
The results are intriguing because they offer a way to understand
H5N1=92s consequences in the brain, says neuroimmunologist Stephanie
Bissel of the University of Pittsburgh School of Medicine. Future
experiments on such survivor mice could reveal whether the mice show
behavioral signs of neurological impairment, she says.
The research team has evidence that H5N1 breaks into the brain by
traveling along the vagus nerve from nerve cells in the gut. The virus
might also enter the brain from the nose by crawling along the
olfactory nerve, Smeyne says.
http://www.sciencenews.org/view/generic/id/338071/title/Bird_flu_leaves_tra=
cks_in_brain
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