Bluetongue virus (BTV): propagation, quantification, and storage.

As an obligate intracellular parasite, the genome of the Bluetongue virus (BTV) contains ten double-stranded RNA segments which are encapsidated by viral proteins, forming "transport vesicles" that can transmit the viral progeny cell-to-cell efficiently and that can also be transmitted animal-to-animal by a biting midge. BTV is a cytoplasmic virus, and its five major steps of viral infection: attachment, entry, uncoating, assembly, and release, occur only in the cytosol within the infected host cell. Viral replication, suppression of cellular processes, and subsequent pathological damage disrupt many cellular pathways, leading to cellular apoptosis. All of these steps are under very rapid, tight, and efficient control. BTV infects both domestic and wild ruminants, especially sheep, but not humans. BTV is also the prototype in the Orbivirus genus of the Reoviridae family, and has been studied very extensively for the last 25 years. The experimental protocols presented here describe most of the methods that have been used routinely and reproducibly in our lab for our studies of the BTV biosystems.