Abstract
African swine fever virus (ASFV) is the causative agent of African swine fever, a disease currently causing significant economic losses in Europe and Asia. Specifically, the highly virulent ASFV strain Georgia 2010 (ASFV-G) is producing disease outbreaks in this large geographical region. The ASFV genome encodes for over 150 genes, most of which are still not experimentally characterized. I8L is a highly conserved gene that has not been studied beyond its initial description as a virus ORF. Transcriptional analysis of swine macrophages infected with ASFV-G demonstrated that the I8L gene is transcribed early during the virus replication cycle. To assess the importance of I8L during ASFV-G replication in vitro and in vivo, as well as its role in virus virulence in domestic swine, we developed a recombinant virus lacking the I8L gene (ASFV-G-ΔI8L). Replication of ASFV-G-ΔI8L was similar to parental ASFV-G replication in primary swine macrophage cultures, suggesting that the I8L gene is not essential for ASFV-G replication in vitro. Similarly, replication of ASFV-G-ΔI8L in swine intramuscularly inoculated with 102 HAD50 displayed replication kinetics similar to ASFV-G. In addition, animals inoculated with ASFV-G-ΔI8L presented with a clinical disease indistinguishable from that induced by the same dose of the virulent parental ASFV-G isolate. We conclude that deletion of the I8L gene from ASFV-G does not affect virus replication in vitro or in vivo, nor changes the disease outcome in swine.
Highlights
Introduction affiliationsAfrican swine fever virus (ASFV), the only member of the virus family Asfarviridae, is the etiological agent of African swine fever (ASF), a contagious disease currently affecting a large geographical area across central Europe, China, and South Asia [1,2]
We demonstrated that deletion of the I8L gene from the genome of the ASFV Georgia 2010 (ASFV-G) isolate does not affect virus replication or virulence in swine, producing a clinical profile nearly identical to the virulent Georgia 2010 isolate
Results demonstrated that the ASFV I8L gene encodes for a protein that is abundantly expressed early in the virus replication cycle
Summary
Primary swine macrophage cultures were prepared from defibrinated blood, as previously described [15]. Growth curves of ASFV-G-∆I8L and parental ASFV-G were performed in primary swine macrophage cell cultures using 6-well plates. Cultures were infected at a MOI of. 0.01 (based on HAD50 previously determined in primary swine macrophage cell cultures). At 2, 24, 48, 72, and 96 h post-infection (hpi), the cells were frozen at ≤−70 ◦ C until the thawed lysates were used to determine titers by HAD50 /mL in primary swine macrophage cell cultures. Virus titration was performed in 96-well plates of primary swine macrophages, the presence of virus was assessed by hemadsorption (HA), and virus titers were calculated as previously described [22]
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