Chapter 7 - Molecular epidemiology studies of bluetongue virus

Abstract

There are 24 distinct serotypes of bluetongue virus (BTV), whose identity is determined by the specificity of reactions between the proteins involved in cell attachment and penetration on the surface of the viral capsid, and the neutralizing antibodies that are generated during infection of the mammalian host. The BTV genes encoding these outer-capsid proteins show nucleotide sequence variations that correlate with both virus serotype and the geographical origin of the virus isolate. “Molecular epidemiology” studies can compare the RNA sequences of individual or multiple genome segments from novel BTV isolates, with those of existing strains from known locations and dates, identifying both virus serotype and topotype. Molecular epidemiology studies of BTV depend on the development of sequence databases for the RNA segments of individual virus isolates from defined locations with well-documented isolation dates and passage histories. Studies of BTV strains, which were generated by exchange (reassortment) of genome segments between two different BTV serotypes, have demonstrated that both of the BTV outer-capsid proteins VP2 and VP5 can influence the specificity of reactions between the virus particle and the neutralizing antibodies. Further sequencing studies will help to clarify relationships between the European field and vaccine strains of BTV.