- Researchers at the Johns Hopkins Bloomberg School of
Public Health have determined that neurons in the central nervous system
react differently to the body's immune defenses to rid themselves of viruses
that cause encephalitis, such as West Nile and Eastern Equine Encephalitis
viruses. Encephalitis is an inflammation of the brain and can cause neurological
problems including, seizures, coma, and death.
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- In a study published in the July 13, 2001 issue of Science,
researchers discovered that T-cells produce a protein, interferon-, which
can clear the virus in neurons located in the spinal cord and brain stem,
but not in neurons located in the cerebral cortex. Neurons are cells that
conduct and generate electrical impulses to carry information throughout
the central nervous system. The findings add to the understanding of lymphocytes
in the immune system and interactions of the central nervous system and
could lead to new approaches to the treatment of viral encephalitis.
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- "Our previous research indicated that antibodies
successfully clear infection from the central nervous system. With this
study, we wanted to see if lymphocytes could also clear viral infections
from the neurons," says Diane Griffin, MD, PhD, professor and chair
of the W. Harry Feinstone Department of Molecular Microbiology and Immunology
at the Johns Hopkins Bloomberg School of Public Health. "Normally,
T-cells control virus infections by destroying infected cells, but that
would be counterproductive for neurons, because the body does not make
new neurons," explains Dr. Griffin.
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- For the study, the researchers observed mice that did
not have the ability to produce antibodies and compared them to normal
mice. The mice were infected with Sindbis virus, a mosquito-borne virus
related to other causes of encephalitis transmitted by mosquitoes, such
as West Nile and Eastern Equine encephalitis viruses.
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- During the experiments, Gwendolyn Binder, a graduate
student in the laboratory of Dr. Griffin, observed that CD4 and CD8 T-cells
both successfully cleared the virus from the neurons from the spinal cord
and brain stem using interferon-. However, the neurons in the brain cortex
did not react to the interferon- in the same manner. This indicated a site-specific
response to this clearance mechanism among the neurons. In addition, the
researchers observed that another protein, TNF-, produced by the T-cells
was unable to clear the virus from the central nervous system.
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- "This research shows that virus-infected neurons
do not all respond to the lymphocyte immune system in the same way to clear
infection. Therefore, different combinations of antibody and T-cell immunity
may be needed for control of infection and recovery from encephalitis depending
on the parts of the brain or spinal cord that are infected," adds
Dr. Griffin.
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- B.Schofield assisted with imaging and photography for
the study. Support was provided by grants from the Markey Foundation (G.K.B.)
and from the National Institute of Neurological Diseases and Stroke (D.E.G.).
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- Public Affairs Media Contacts Tim Parsons or Ming Tai
@ 410.955.6878 or paffairs@jhsph.edu
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