Analysis of Bluetongue Virus mRNA in Baby Hamster Kidney Cells and Sheep Tissues by Real-time Reverse Transcription Polymerase Chain Reaction

Abstract

Bluetongue virus (BTV), a member of the genus Orbivirus of the family Reoviridae, is the causative agent of bluetongue. The present study further characterizes the replication of Taiwan prototype BTV2/KM/2003 in baby hamster kidney cell line BHK-21 and in formalin-fixed paraffin-embedded tissues of an infected sheep. Messenger RNA transcribed from the BTV genes was measured by a real-time reverse transcription polymerase chain reaction. In the infected BHK-21 cells, the three most transcribed genes were NS2, VP4, and VP7 genes. The abundance of BTV mRNA species in the tissues of infected sheep demonstrated a different pattern, wherein NS1-3 genes were most frequently transcribed. Among all tissues examined, NS1-3 genes were detected at relatively higher levels, indicated by the lower Ct values, in the tongue, haired lip, ear pinna and cerebrum, consistent with the low virulence of the Taiwan BTV2/KM/2003 to Corriedal sheep as previously characterized. The tongue, haired lip, ear, and cerebrum are located primarily in the craniofacial regions and are closer to the inoculation site of contralateral ear pinna. The inoculated BTV should have low or moderate penetration capability, so that the viral gene expressions in the more distant tissues were relatively low, despite the establishment of viremia and the permissiveness of tissues to the virus. Alternatively BTV may have higher tropism for these craniofacial tissues.