London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Bluetongue virus (BTV) is an insect vectored emerging pathogen of wild ruminants and livestock causing disease in sheep, goats, and cattle with mortality reaching 70% in some breeds of sheep. The virus is transmitted by several species of biting midges in the Culicoides genus, which determine its geographic distribution. BTV is endemic in many tropical and sub-tropical countries and including India, but since 1998 incursions of BTV into mainland Europe have been common events, reaching as far north as France and Holland in 2006 and now in UK, Denmark and Switzerland. Climate change may have contributed to the emergence of BTV in Europe through the increased distribution and size of insect vector populations. Since 1998, BTV has resulted in considerable economic lost. BTV is the prototype of Orbivirus genus within the Reoviridae family. BTV virions are architecturally complex structures composed of 7 discrete proteins that are organised into two shells enclosing a genome of 10 double-stranded (ds) RNA segments. In my laboratory, BTV has been the subject of extensive molecular, genetic and structural studies for the last 20 years. The combination of structural and molecular studies have provided a much finer level of understanding of the overall structural organisation of the virus and has improved our understanding of the functional basis of replication and “who does what” in the virus life cycle. Information gained from these studies allowed us to produce highly efficacious safe vaccines for bluetongue and related diseases. More recently we have been successful in demonstrating that it is possible to establish BTV infection entirely from BTV messenger sense RNA, without the presence of a helper virus. This discovery is a breakthrough in the field as all previous studies have indicated that helper virus is essential to the recovery of infectious virus for eukaryotic viruses with a dsRNA genome. Further, we were able to exploit the system in incorporating heterologous BTV transcripts made from DNA plasmids. Our goal is to use the system for manipulation of the virus genome in order to develop economically feasible and safer vaccines for BTV and other related viruses.
