Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2004
Publication Date: 3/1/2005
Citation: Risatti, G.R., Borca, M.V., Kutish, G.F., Lu, Z., Holinka, L.G., French, R., Tulman, E., Rock, D.L. 2005 The E2 Glycoprotein of Classical Swine Fever Virus Affects Viral Virulence in Swine. Journal of Virology.79: 3787-3796.
Interpretive Summary: The report describes by the first time that CSFV glycoprotein E2 is a virulent factor during the viral infection in swine. Chimeric recombinant viruses containing the E2 gene from an attenuated vaccine strain is able to induce complete attenuation in pig when inserted in the backbone of a highly virulent CSFV strain.
Technical Abstract: To identify genetic determinants of classical swine fever virus (CSFV) virulence and host range, chimeras of the highly pathogenic Brescia strain and the attenuated vaccine strain CS were constructed and evaluated for viral virulence in swine. Upon initial screening, only chimeras 138.8v and 337.14v, the only chimeras containing the E2 glycoprotein of CS, were attenuated in swine despite exhibiting unaltered growth characteristics on primary porcine macrophage cell cultures. Additional viral chimeras were constructed to confirm the role of E2 in virulence. Chimeric virus 319.1v, which contained only the CS E2 glycoprotein in the Brescia background, was markedly attenuated in pigs, exhibiting significantly decreased virus replication in tonsils, a transient viremia, limited generalization of infection, and decreased virus shedding. Chimeras encoding all Brescia structural proteins in a CS genetic background remained attenuated, indicating that additional mutations outside the structural region are important for CS vaccine virus attenuation. These results demonstrate that CS E2 alone is sufficient for attenuating Brescia, indicating a significant role for the CSFV E2 glycoprotein in swine virulence.