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How the immune system eliminates mosquito-borne viruses--new insights. (EH Update).

Researchers at the Johns Hopkins Bloomberg School of Public Health have determined that neurons throughout the central nervous system react differently to the body's immune defenses to rid themselves of viruses that cause encephalitis, such as the West Nile and eastern equine encephalitis viruses. Encephalitis is an inflammation of the brain and can cause neurological problems including seizures, coma, and death.

In a study published in the July 13, 2001, issue of Science, researchers discovered that T-cells produce a protein, interferon-[gamma], 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 could lead to new approaches to the treatment of viral encephalitis.

"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," said Diane Griffin, M.D., Ph.D., professor and chair of the W. Harry Feinstone Department of Molecular Microbiology and Immunology. "Normally, T-cells control virus infections by destroying infected cells, but that would be counter-productive for neurons, because the body does not make new neurons," explained Dr. Griffin.

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 the Sindbis virus, a mosquitoborne virus related to the West Nile virus and the eastern equine encephalitis virus.

During the experiments, Gwendolyn Binder, a graduate student, observed that, using interferon-[gamma], CD4 and CD8 T-cells both successfully cleared the virus in the neurons from the spinal cord and brain stem. The neurons in the brain cortex, however, did not react to the interferon-[gamma] in the same manner. This result indicated a site-specific response among neurons to the clearance mechanism. In addition, the researchers observed that another protein produced by the T-cells, tumor necrosis factor [alpha], was unable to clear the virus from the central nervous system.

"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," added Dr. Griffin.
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Publication:Journal of Environmental Health
Article Type:Brief Article
Geographic Code:1USA
Date:May 1, 2002
Words:406
Previous Article:Science and theory. (Tools for Environmental Health).
Next Article:A new phage may help control pathogens on fresh-cut produce. (EH Update).
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