How the immune system eliminates mosquito-borne viruses--new insights. (EH Update).Researchers at the Johns Hopkins Bloomberg School of Public Health The Johns Hopkins Bloomberg School of Public Health is part of Johns Hopkins University in Baltimore, Maryland, U.S. It was the first institution of its kind in the world. Founded in 1916 by William H. Welch and John D. 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 encephalitis (ĕnsĕf'əlī`təs), general term used to describe a diffuse inflammation of the brain and spinal cord, usually of viral origin, often transmitted by mosquitoes, in contrast to a bacterial infection of the meninges , 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 spinal cord, the part of the nervous system occupying the hollow interior (vertebral canal) of the series of vertebrae that form the spinal column, technically known as the vertebral column. and brain stem, but not in neurons located in the cerebral cortex cerebral cortex Layer of gray matter that constitutes the outer layer of the cerebrum and is responsible for integrating sensory impulses and for higher intellectual functions. . (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 viral encephalitis Viral meningoencephalitis Neurology, infectious disease A general term for nonpurulent–'aseptic' viral infection of the CNS Etiology Coxsackie A and B–eg, A7, enterovirus 71, herpes simplex, etc Clinical If the viral load is extreme, . "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 Sindbis virus n. An alphavirus that is the causative agent of Sindbis fever. , a mosquitoborne virus related to the West Nile virus West Nile virus, microorganism and the infection resulting from it, which typically produces no symptoms or a flulike condition. The virus is a flavivirus and is related to a number of viruses that cause encephalitis. 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 tumor necrosis factor n. Abbr. TNF A protein that is produced in the presence of an endotoxin, especially by monocytes and macrophages, is able to attack and destroy tumor cells, and exacerbates chronic inflammatory diseases. [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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