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Department of Microbiology, A Leader in Microbiology and Microbial Pathogenesis Research and Training.

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Stephanie Schittone, Ph.D.

Tyler Lab


​​​THESIS

 

     Complete Title of Thesis:

"Reovirus Myelitis:  development and analysis of mechanisms of spinal cord injury in a novel model of viral myelitis."

 

     Prepared under the direction of: Kenneth L Tyler, MD

 

SUMMARY

      Virus infection of the central nervous system (CNS) including myelitis and encephalitis are important causes of morbidity and mortality throughout the world. Current treatment options for these devastating illnesses are limited and often only marginally effective. We developed an experimental model of viral myelitis utilizing reovirus infection, a classic experimental system that has been extensively utilized to study viral pathogenesis. Two neurotropic strains of reovirus, type 3 Abney and Dearing, induce a progressive paralysis in 90% of infected mice. Investigation of mechanisms of injury found apoptosis of reovirus-infected neurons by co-localization of active caspase 3 and reovirus antigen in lumbar spinal cord (SC) sections. Western blot analysis found activation of the protease Calpain; as well as increases in inducible nitric oxide synthase (iNOS) and heme-oxygenase 1, markers of oxidative stress. Laser scanning confocal microscopy of infected SC illustrated dramatic activation and proliferation of microglia and astrocytes (“gliosis”) in SCs of infected animals, indicating an innate immune response of these uninfected cells to reovirus infection of neurons. Further evaluation of the innate immune response identified up-regulation of interferon stimulated genes including genes known to sensitize cells to apoptosis when over-expressed. Up-regulation of inflammatory cytokines and chemokines were found in microglia-enriched fractions of SC cellular suspensions. Even though the neonatal mice used in our studies have immature immune systems, a T-cell response was detected in paralyzed animals. Ex vivo SC slice cultures established that CNS trafficking of hematopoietically derived inflammatory cells was not required for reovirus induced CNS tissue destruction or up-regulation of inflammatory cytokines and chemokines. The cardinal clinical, pathological and immunological features of reovirus myelitis, closely parallel those seen in important types of human viral myelitis, thereby establishing this as a relevant experimental model system. New model systems are required to study the basis of virus-induced spinal cord injury and to test potential therapeutic interventions. Future studies utilizing knock-out mice with defined immune deficits in both the SC ex vivo slice system and in in vivo infection will enable us to evaluate the timing and role of specific inflammatory cell types and their mediators in the pathogenesis of viral myelitis. ​​