Bovine leukaemia virus antisense transcription is required for viral replication

Abstract

The bovine leukaemia virus (BLV) is a deltaretrovirus naturally infecting B-cells in cattle, which can lead in 5% of cases to an aggressive condition called enzootic bovine leukosis. The recent discovery of antisense transcripts, continuously expressed in both asymptomatic and leukaemic cells, opens new perspectives for understanding viral replication or pathogenesis. The objective of this work is to evaluate the importance of BLV antisense transcription in viral replication. Results show that a two-nucleotides mutation of the SP1 binding site drastically inhibits the transcriptional activity of the minimal 3’LTR promoter. In the context of a full-length provirus, this mutation induces a significant decrease of antisense transcripts in cell culture, and in a drastic reduction of proviral loads in infected animals. Antisense transcription thus plays a crucial role in viral replication.