The characteristic tubules that are produced during the orbivirus infection cycle are composed of a major viral nonstructural protein, NS1. To characte`rize the NS1 gene and gene product of African horsesickness virus (AHSV), a full-length cDNA copy of the NS1 gene of AHSV-6 was cloned and the nucleotide sequence determined. NS1 was highly conserved within the AHSV serogroup with between 95–98% conservation of amino acids among NS1 of AHSV-6, AHSV-4 and AHSV-9. The structure of AHSV NS1 tubules was investigated by in vitro translation of the AHSV-6 NS1 gene followed by expression of the gene in insect cells. The NS1 protein assembled in tubular structures with a diameter of approximately 23 nmand lengths of up to 4 μm. The absence of a ladder-like structure and lower sedimentation value of AHSV NS1 tubules clearly distinguished them from those of blue- tongue virus.
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