Structural glycoprotein E2 of classical swine fever virus binding to host protein dynactin subunit (DCTN6) is necessary for virus virulence in swine

Authors: Borca, Manuel; VUONO, ELIZABETH - Mississippi State University; RAMIREZ-MEDINA, ELIZABETH - University Of Connecticut; Azzinaro, Paul; BERGGREN, K. - Princeton University; SINGER, M. - Fordham University; RAI, AYUSHI - Oak Ridge Institute For Science And Education (ORISE); PRUITT, SARAH - Oak Ridge Institute For Science And Education (ORISE); SILVA, EDIANE - Kansas State University; VELAZQUEZ-SALINAS, LAURO - Kansas State University; CARRILLO, CONSEULO - Animal And Plant Health Inspection Service (APHIS); Gladue, Douglas

Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2019
Publication Date: 12/12/2019
Citation: Borca, M.V., Vuono, E.A., Ramirez-Medina, E., Azzinaro, P.A., Berggren, K.A., Singer, M., Rai, A., Pruitt, S., Silva, E., Velazquez-Salinas, L., Carrillo, C., Gladue, D.P. 2019. Structural glycoprotein E2 of classical swine fever virus binding to host protein dynactin subunit (DCTN6) is necessary for virus virulence in swine. Journal of Virology. https://doi.org/10.1128/JVI.01642-19.
DOI: https://doi.org/10.1128/JVI.01642-19

Interpretive Summary: Classical swine fever virus causes a devastating disease in swine. We are exploring the mechanisms the virus uses to cause disease in pigs and, with this information develop better prevention measures such as vaccines. The current study describes that a viral protein that is part of the external structure of the virus interacts with a cellular protein during infection in pigs. Using genetic engineering, we prevented this viral protein from interacting with the pig protein and as a result the modified virus no longer causes disease. This suggests that the viral protein binding to the host proteins is necessary for the virus to cause disease in pigs. Understanding how viral proteins interact with the host cellular proteins is important information that can be used to help designing better vaccines.

Technical Abstract: The E2 protein in swine fever virus (CSFV) is the major virus structural glycoprotein and an essential component of the viral particle. E2 has been shown to be involved in several functions including virus adsorption, induction of protective immunity and virulence in swine. Using the yeast two-hybrid system, we previously identified a swine host protein, dynactin subunit 6 (DCTN6), which is a component of the cell dynactin complex, as a specific binding partner for E2. We confirmed the interaction between DCTN6 and E2 proteins in CSFV-infected swine cells by using two additional independent methodologies, co-immunoprecipitation and proximity ligation assay. E2 residues critical to mediate the protein-protein interaction with DCTN6 were mapped by a reverse yeast-two-hybrid approach using a randomly mutated E2 library. A recombinant CSFV mutant, E2'DCTN6v, harboring specific substitutions in those critical residues was developed to assess the importance of the E2-DCTN6 protein-protein interaction for viral replication and virulence in swine. CSFV E2'DCTN6v shows reduced replication than the parental virus in an established swine cell line, SK6, and in primary swine macrophage cultures. Remarkably, animals infected with CSFV E2'DCTN6v remained clinically normal during the 21-day observational period indicating that the ability of CSFV E2 to bind host DCTN6 protein efficiently during the infection plays a critical role in virus virulence.