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Journal of Virology, March 2005, p. 2743-2753, Vol. 79, No. 5
0022-538X/05/$08.00+0 doi:10.1128/JVI.79.5.2743-2753.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
1s Is a Determinant of Reovirus Virulence and Influences the Kinetics and Severity of Apoptosis Induction in the Heart and Central Nervous System
Departments of Immunology,1 Neurology,3 Pediatrics,4 Microbiology,5 Medicine,2 Program in Neurosciences, University of Colorado Health Sciences Center,6 Denver Veterans Affairs Medical Center, Denver, Colorado7
Received 25 May 2004/ Accepted 11 October 2004
The mechanisms by which viruses kill susceptible cells in target organs and ultimately produce disease in the infected host remain poorly understood. Dependent upon the site of inoculation and strain of virus, experimental infection of neonatal mice with reoviruses can induce fatal encephalitis or myocarditis. Reovirus-induced apoptosis is a major mechanism of tissue injury, leading to disease development in both the brain and heart. In cultured cells, differences in the capacity of reovirus strains to induce apoptosis are determined by the S1 gene segment, which also plays a major role as a determinant of viral pathogenesis in both the heart and the central nervous system (CNS) in vivo. The S1 gene is bicistronic, encoding both the viral attachment protein sigma-1 and the nonstructural protein sigma-1-small (
1s). Although
1s is dispensable for viral replication in vitro, we wished to investigate the expression of
1s in the infected heart and brain and its potential role in reovirus pathogenesis in vivo. Two-day-old mice were inoculated intramuscularly or intracerebrally with either
1s or
1s+ reovirus strains. While viral replication in target organs did not differ between
1s and
1s+ viral strains, virus-induced caspase-3 activation and resultant histological tissue injury in both the heart and brain were significantly reduced in
1s reovirus-infected animals. These results demonstrate that
1s is a determinant of the magnitude and extent of reovirus-induced apoptosis in both the heart and CNS and thereby contributes to reovirus pathogenesis and virulence.
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