Pathogenicity, genomic analysis and structure of abalone asfa-like virus: evidence for classification in the family Asfarviridae

Abstract

This paper presents the rationale for classifying abalone asfa-like virus (AbALV) in the family Asfarviridae based on analyses of the host, whole genome and electron microscopic observations. AbALV caused >80 % cumulative mortality in an experimentally infected mollusc, Haliotis madaka. The AbALV genome was found to be linear, approximately 281 kb in length, with a G+C content of 31.32 %. Of the 309 predicted ORFs, 48 of the top hits with African swine fever virus (ASFV) genes in homology analysis were found to be in the central region of the genome. Synteny in the central region of the genome was conserved with ASFV. Similar to ASFV, paralogous genes were present at both ends of the genome. The pairwise average amino acid identity (AAI) between the AbALV and ASFV genomes was 33.97 %, within the range of intra-family AAI values for Nucleocytoviricota. Electron microscopy analysis of the gills revealed ~200 nm icosahedral virus particles in the cytoplasm of epithelial cells, and the size and morphology resembled ASFV. In addition to swine, ASFV also infects ticks, which are protostomes like abalone. The overall genome structure and virion morphology of AbALV and ASFV are similar, and both viruses infect protostomes, suggesting that AbALV is a new member of the family Asfarviridae.