The integration of a macrophage-adapted live vaccine strain of equine infectious anaemia virus (EIAV) in the horse genome

Integration is an important feature of retroviruses and retrovirus-based therapeutic transfection vectors. The non-primate lentivirus equine infectious anaemia virus (EIAV) primarily targets macrophages/monocytes in vivo . Investigation of the integration features of EIAV DLV121 strains, which are adapted to donkey monocyte-derived macrophages (MDMs), is of great interest. In this study, we analysed the integration features of EIAV DLV121 in equine MDMs during in vitro infection. Our previously published integration sites (IS) for EIAV FDDV13 in fetal equine dermal (FED) cells were also analysed in parallel as references. Sequencing of the host genomic regions flanking the viral IS showed that reference sequence (RefSeq) genes were preferentially targeted for integration by EIAV DLV121 . Introns, AT-rich regions, long interspersed nuclear elements (LINEs) and DNA transposons were also predominantly biased toward viral insertion, which is consistent with EIAV FDDV13 integration into the horse genome in FED cells. In addition, the most significantly enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, specifically gag junctions for EIAV DLV121 and tight junctions for EIAV FDDV13 , are regulators of metabolic function, which is consistent with the common bioprocesses, specifically cell cycle and chromosome/DNA organization, identified by gene ontology (GO) analysis. Our results demonstrate that EIAV integration occurs in regions that harbour structural and topological features of local chromatin in both macrophages and fibroblasts. Our data on EIAV will facilitate further understanding of lentivirus infection and the development of safer and more effective gene therapy vectors.