Location: Virus and Prion ResearchTitle: Development and utilization of an infectious clone for porcine deltacoronavirus strain USA/IL/2014/026
|DENG, XUFANG - Loyola University|
|PILLATZKI, ANGELA - South Dakota State University|
|BAKER, SUSAN - Loyola University|
Submitted to: Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2020
Publication Date: 11/13/2020
Citation: Deng, X., Buckley, A.C., Pillatzki, A., Lager, K.M., Baker, S.C., Faaberg, K.S. 2020. Development and utilization of an infectious clone for porcine deltacoronavirus strain USA/IL/2014/026. Virology. 553:35-45. https://doi.org/10.1016/j.virol.2020.11.002.
Interpretive Summary: Porcine deltacoronavirus (PDCoV) appeared in the United States swine herd in 2013, causing gastrointestinal disease in young piglets. There is no vaccine against PDCoV. To advance the research into PDCoV disease, an infectious clone of wild-type PDCoV (icPDCoV) was developed. Two mutants were engineered in order to examine potential virulence domains, icEnUmut and icDelNS6/nG. Swine cells were infected with the icPDCoV and the two mutant viruses to study how the viruses replicated within a cell, and for their ability to upregulate molecules important in the innate immune response, particularly interferon. Part of a cell’s response to a virus infection is the production of interferon, and it is common for viruses to develop an anti-interferon strategy that involves virus-specific proteins. The wild-type icPDCoV was found to inhibit the interferon response of the swine cells as expected. In contrast, icEnUmut did not indicating that the genome region that was mutated may be responsible for interferon inhibition of parental wild-type PDCoV. This research demonstrates how the virus may function in the host which provides opportunities to mutate the virus to produce a potential vaccine.
Technical Abstract: We report the generation of a full-length infectious cDNA clone for porcine deltacoronavirus strain USA/IL/2014/026. The rescued recombinant virus, icPDCoV, replicated as efficiently as the parental strain in cell culture and in animals. An endoribonuclease-inactive mutant of PDCoV, icEnUmut, was then generated. Unlike icPDCoV, this mutant virus stimulated a robust interferon response in PK1 cells, consistent with the endoribonuclease (EnU) that resides in nonstructural protein 15 acting as a conserved interferon antagonist. In addition, to investigate whether nonstructural protein 6 (NS6) suppressed the interferon response, an NS6-deletion virus was engineered (icDelNS6/nG) by replacing the NS6 gene with the coding sequence of mNeonGreen protein. By comparing icDelNS6/nG infection of PK1 cells to that of icPDCoV and icEnUmut, we found that icDelNS6/nG elicited similar mRNA levels of interferon as icPDCoV and indicated that NS6 does not act as an interferon antagonist. Taken together, the construction of a full-length infectious clone and the identification of EnU as an interferon antagonist will aid in the development of a live-attenuated vaccine.