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Research Project: Intervention Strategies to Control and Eradicate Foreign Animal Diseases of Swine

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Title: Evaluation of the deletion of ASFV MGF110-5L-6L on swine virulence and its potential use as a DIVA vaccine marker gene

item Ramirez-Medina, Elizabeth
item VUONO, ELIZABETH - University Of Mississippi
item Pruitt, Sarah
item RAI, AYUSHI - Oak Ridge Institute For Science And Education (ORISE)
item VALLADARES, ALYSSA - Oak Ridge Institute For Science And Education (ORISE)
item Espinoza, Nallely
item Velazquez, Lauro
item Gladue, Douglas
item Borca, Manuel

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2021
Publication Date: 2/12/2021
Citation: Ramirez Medina, E., Vuono, E., Pruitt, S.E., Rai, A., Valladares, A., Espinoza, N.N., Velazquez Salinas, L., Gladue, D.P., Borca, M.V. 2021. Evaluation of the deletion of ASFV MGF110-5L-6L on swine virulence and its potential use as a DIVA vaccine marker gene. Viruses.

Interpretive Summary: African swine fever virus (ASFV) causes a devastating disease in swine, called African swine fever (ASF), that is currently spreading across Europe and Asia. There is no available vaccine for ASF, and currently only experimental live attenuated vaccines are derived from deletions of individual genes in the ASFV genome. In this study we were able to delete an antigenic protein in ASFV, however deletion of this protein did not have any effect on virus replication or virulence. When introduced into a vaccine candidate, vaccine efficacy was lost

Technical Abstract: African swine fever virus (ASFV) is responsible for an on-going pandemic that is affecting central Europe and Asia. ASFV was also recently detected in the Dominican Republic, the first report of the disease in the western hemi-sphere in more than 40 years. ASFV is a large, complex virus with a dsDNA genome that encodes for more than 150 genes, most of which have not been studied. Here we assess the MGF110-5L-6L gene during virus replication in cell cultures and experimental infection studies in swine. A recombinant virus with a deletion of MGF110-5L-6L (ASFV-G-'MGF110 5.6) was developed using the highly virulent ASFV Georgia (ASFV-G) isolate as a template. ASFV-G-'MGF110-5L-6L replicates in swine macrophage cultures as efficiently as the parental virus ASFV-G, in-dicating the MGF110-5L-6L gene is non-essential for virus replication. Similarly, domestic pigs inoculated with ASFV-G-'MGF110 5.6 presented with a clinical disease undistinguishable from that caused by the parental ASFV-G, confirming the MGF110-5L-6L gene is not involved in producing disease in swine. Sera from animals in-oculated with an efficacious vaccine candidate, ASFV-G-'MGF, strongly recognize the protein encoded by the MGF110-5L-6L gene is a potential target for the development of an antigenic marker DIVA vaccine. To test this hypothesis, the MGF110-5L-6L gene was deleted from the highly efficacious ASFV vaccine candidate ASFV-G-'I177L, generating the recombinant ASFV-G-'I177L/'MGF110-5L-6L. Animals inoculated with ASFV-G-'I177L/'MGF110-5L-6L developed an ASFV-specific antibody response detected by ELISA. The sera strongly recognized ASFV p30 expressed in eukaryotic cells but did not recognize ASFV MGF110-5L-6L protein, demonstrating that deletion of the MGF110-5L-6L gene can enable DIVA capabilities in pre-existing vaccine can-didates.