Development and In Vivo Evaluation of a MGF110-1L Deletion Mutant in African Swine Fever Strain Georgia

African swine fever (ASF) is currently causing an epizootic, affecting pigs throughout Eurasia, and causing significant economic losses in the swine industry. ASF is caused by African swine fever virus (ASFV) that consists of a large dsDNA genome that encodes for more than 160 genes; few of these genes have been studied in detail. ASFV contains four multi-gene family (MGF) groups of genes that have been implicated in regulating the immune response and host specificity; however, the individual roles of most of these genes have not been well studied. Here, we describe the evaluation of the previously uncharacterized ASFV MGF110-1L open reading frame (ORF) using a deletion mutant of the ASFV currently circulating throughout Eurasia. The recombinant ASFV lacking the MGF110-1L gene (ASFV-G-ΔMGF110-1L) demonstrated in vitro that the MGF110-1L gene is non-essential, since ASFV-G-ΔMGF110-1L had similar replication kinetics in primary swine macrophage cell cultures when compared to parental highly virulent field isolate Georgia2007 (ASFV-G). Experimental infection of domestic pigs with ASFV-G-ΔMGF110-1L produced a clinical disease similar to that caused by the parental ASFV-G, confirming that deletion of the MGF110-1L gene from the ASFV genome does not affect viral virulence.