Gene reassortment in bluetongue virus
The main focus of this project was that the vaccination strategy developed by the consortium of researchers would be efficacious. There are many factors that may interfere with this goal. The one under study in this instance was the possibility of mixing of genotypes from the live attenuated (or modified) virus and strains of the virus that occur naturally in the field. The infective mechanism involves the midge, Culicoides a natural vector. Reassortment of genes of this nature may render a vaccine useless against newly created strains. Mixing of gene sequences is a common occurrence naturally and is thought to be largely responsible for varied gene pools available throughout evolution. Researchers at Onderstepoort Veterinary Institute have discovered indirect evidence that this may have occurred within bluetongue virus. Samples were taken from random animals (both cows and sheep) and tested for reassortants. One of these taken from a cow was found to be 'vaccine like'. This means that this may have been vector transmitted as there is no vaccination programme for bovines in South Africa. The results of this particular study have far-reaching implications for the control of BTV in southern Europe as reassortment may create strains with unknown virulence. This reinforces the importance of developing inactivated vaccines integrating engineered 'virus-like particles' (VLPs). Further research could open the way to the commercial production of VLP-based vaccines and help to prevent further serious losses following incursions of the disease.
