Nonstructural Protein capital sigma 1s Is a Determinant of Reovirus Virulence and Influences the Kinetics and Severity of Apoptosis Induction in the Heart and Central Nervous System

• Published in: Journal of virology Vol. 79; no. 5; pp. 2743 - 2753
• Main Authors: Hoyt, Cristen C, Richardson-Burns, Sarah M, Goody, Robin J, Robinson, Bridget A, Debiasi, Roberta L, Tyler, Kenneth L
• Format: Journal Article
• Language: English
• Published: 01-03-2005
• Subjects: Reovirus
• ISSN: 0022-538X

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 ( capital sigma 1s). Although capital sigma 1s is dispensable for viral replication in vitro, we wished to investigate the expression of capital sigma 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 capital sigma 1s super(-) or capital sigma 1s super(+) reovirus strains. While viral replication in target organs did not differ between capital sigma 1s super(-) and capital sigma 1s super(+) viral strains, virus- induced caspase-3 activation and resultant histological tissue injury in both the heart and brain were significantly reduced in capital sigma 1s super(-) reovirus- infected animals. These results demonstrate that capital sigma 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.