Systematic Veterinary Virology

MORPHOLOGY

• The virus measures approximately 55-70nm in diameter. The virions not enveloped and hence are not ether sensitive. The capsid shell of virion is composed of three layers (outer, middle and inner capsids). The virus has icosahedral symmetry.
• The genome of AHS virus (AHSV) is composed of ten double-stranded RNA segments comprising 18000 nucleotides, which encode seven structural proteins (VP1-7) and four nonstructural proteins (NS1, NS2, NS3, NS3A). Proteins VP2 and VP5 form the outer capsid of the virion, and proteins VP3 and VP7 are the major inner capsid (middle) proteins. Proteins VP1, VP4 and VP6 constitute minor inner capsid proteins. VP2 protein is highly variable and is responsible for serotype variations.