Changes in the genome of African swine fever virus (Asfarviridae: Asfivirus: African swine fever virus) associated with adaptation to reproduction in continuous cell culture

Abstract

African swine fever virus (ASFV) is a large, double-stranded DNA virus in the Asfarviridae family. It is the causative agent of African swine fever (ASF). Only the genome of BA71V strain, adapted to Vero cell culture, was fully analyzed.The aim of this study was analyzing the complete genome sequence of two strains of adapted to the growth in CV-1 cell culture (CC) ASFV obtained after 30 and 50 passages, in comparison to the parental virus. ASFV isolate Odintsovo 02/14 (parental), ASFV adapted variants ASFV/ARRIAH/CV-1/30 and ASFV/ARRIAH/CV-1/50 were all used to extract genomic DNA (gDNA). Sequencing library was constructed using the «Nextera XT DNA library preparation kit» («Illumina», USA). Genomes of ASFV/ARRIAH/CV-1/30 and ASFV/ARRIAH/CV-1/50 consisted of 186 529 bp and 186 525 bp, respectively. Total 78 single nucleotide polymorphisms (SNPs) were identified between the parental Odintsovo 02/14 and the two high passaged strains, as well as a 2947 bp large-size deletion in the 3' variable region of adapted viruses was detected. ASFV as a DNA-containing virus may not have a very high level of mutation, but this is the second study showing that adaptation to growth in continuous CC leads to large deletions in the genome of the virus. Mutations in the protein-coding regions of the genome can be synonymous and non-synonymous, i.e. leading to amino acid substitution. Additional research is needed to understand the influence of the mutations described in the adaptation process on the reproduction of the virus and its virulence.