Bovine herpesvirus 5 encodes a unique pattern of microRNAs compared with bovine herpesvirus 1

Bovine herpesvirus type 5 (BoHV-5) and bovine herpesvirus 1 (BoHV-1) are two closely related viruses. However, BoHV-5 is responsible for fatal meningitis in calves, while BoHV-1 is associated with infectious rhinotracheitis in cattle, and the mechanism by which the two viruses cause different symptoms is not well understood. In this study, we identified 11 microRNA (miRNA) genes, encoded by the BoHV-5 genome, that were processed into 16 detectable mature miRNAs in productive infection as determined by deep sequencing. We found that 6 out of 16 miRNA genes were present as two copies in the internal repeat and terminal repeat regions, resulting in a total of 17 miRNA-encoding loci distributed in both DNA strands. Surprisingly, BoHV-5 shared only one conservative miRNA with BoHV-1, which was located upstream of the origin of replication. Furthermore, in contrast to BoHV-1, no miRNAs were detected in the unique short region and locus within or near the bovine infected-cell protein 0 and latency-related genes. Variations in both the 5' and 3' ends of the reference sequence were observed, resulting in more than one isoform for each miRNA. All of the 16 miRNAs were detectable by stem-loop reverse transcriptase-PCR. The miRNAs with high read numbers were subjected to Northern blot analysis, and all pre-miRNAs and one mature miRNA were detected. Collectively, the data suggest that BoHV-5 encodes a different pattern of miRNAs, which may regulate the life cycle of BoHV-5 and might account for the different pathogenesis of this virus compared with BoHV-1.