Deletion of the ASFV dUTPase Gene E165R from the Genome of Highly Virulent African Swine Fever Virus Georgia 2010 Does Not Affect Virus Replication or Virulence in Domestic Pigs

Abstract

African swine fever (ASF) is a frequently lethal disease of domestic and wild swine currently producing a pandemic affecting pig production in Eurasia. The causative agent, ASF virus (ASFV) is a structurally complex virus with a large genome harboring over 150 genes. One of them, E165R, encodes for a protein belonging to the dUTPase family. The fine structure of the purified protein has been recently analyzed and its dUTPase activity tested. In addition, it has been reported that a BA71 mutant virus, adapted to growth in Vero cells, lacking the E165R gene presented a drastic decreased replication in swine macrophages, its natural target cell. Herein, we report the development of a recombinant virus, ASFV-G-∆E165R, harboring the deletion of the E165R gene from the genome of the highly virulent field isolate ASFV Georgia 2010 (ASFV-G). Interestingly, ASFV-G-∆E165R replicates in primary swine macrophage cultures as efficiently as the parental virus ASFV-G. In addition, ASFV-G-∆E165R also replicates in experimentally inoculated domestic pigs with equal efficacy as ASFV-G and produced a lethal disease almost indistinguishable from that induced by the parental virus. Therefore, results presented here clearly demonstrated that E165R gene is not essential or important for ASFV replication in swine macrophages nor disease production in domestic pigs.

Evaluation of the Function of ASFV Gene E66L in the Process of Virus Replication and Virulence in Swine

“…This fact was consistent with the increased number of putative nonsynonymous mutations predicted between the two genetic groups. Interestingly, this situation contrasted with our previous predictions at, A859L [ 34 ], A151R [ 35 ], A104R [ 36 ], E165R [ 37 ], EP296R [ 38 ], and H108R [ 39 ], where variable dN/dS rates <1 were predicted; therefore, indicating that positive selection is the dominant force shaping the evolution of E66L gene.…”

African Swine Fever Virus Gene B117L Encodes a Small Protein Endowed with Low-pH-Dependent Membrane Permeabilizing Activity

“…2B). Interestingly, as published in our previous studies (15), the phylogenetic relationship among isolates using B117L from different genotypes contrasts with the relationships predicted by the reference p72 gene indicating the complex evolutionary dynamics among different ASFV genes, suggesting that one single gene may not be used to reflect the relationship among ASFV isolates (40).…”

“…To infer the evolutionary dynamics of B117L gene in nature, we used a systematic approach previously published in ASFV (15,16,17) and SARS-CoV-2 (18). This approach considers the different modes by which natural selection can be manifested (diversifying: including episodic and pervasive selection, or purifying), and is associated to the combination of multiple maximum likelihood evolutionary algorithms that infer rates of synonymous (dS) and nonsynonymous substitutions on a per site basis in a codon base phylogenetic framework (19).…”

Deleting the C84L Gene from the Virulent African Swine Fever Virus SY18 Does Not Affect Its Replication in Porcine Primary Macrophages but Reduces Its Virulence in Swine

“…With researchers’ continuous study on ASFV in recent years, the various functions of the ASFV gene have gradually been elucidated. Deleting the C962R or E165R genes from the wild-type strain did not affect the replication of the virus in primary macrophages, nor did it affect the virulence of the virus in pigs [ 32 , 33 ]. Deleting similar genes can serve as a continuous fluorescent marker for viruses to investigate further the molecular mechanisms of the pathogenicity of the strain [ 34 ].…”