Genome segment reassortment identifies non-structural protein NS3 as a key protein in African horsesickness virus release and alteration of membrane permeability.

The role of African horsesickness virus (AHSV) nonstructural membrane protein NS3 in determining the effects of AHSV infection on Vero cells was examined. NS3 protein sequences are highly variable and cluster into three phylogenetic groups, alpha, beta, and gamma. Three AHSV strains, with NS3 from alpha, beta, or gamma, were shown to have quantitatively different phenotypes in Vero cells. Reassortants between these strains, in which the S10 genome segment encoding NS3 was exchanged alone or with other segments, were generated and compared to parental strains. Exchange of the NS3 gene resulted in changes in virus release, membrane permeability and total virus yield, indicating an important role for NS3 in these viral properties. Differences in the cytopathicity and the effect on cell viability between the parental strains could not be associated with NS3 alone, and it is likely that a number of viral and host factors play a role.