Ultrastructure and morphogenesis of White Spot Syndrome Baculovirus (WSSV)
Diseases of Aquatic Organisms
Since 1993 non-occluded baculoviruses, associated with a syndrome with high mortalities, have been reported in cultured penaeid shrimp from Asia and the Indo-Pacific region. Infections are typically accompanied by the presence of white spots on the cuticle. Numerous names were given to the virus(es) in early reports on the disease, but the syndrome is increasingly known as White Spot Syndrome (\YSS) and its viral agent(s) as White Spot Syndrome Baculovirus (WSSV). The \YSS virion is a stocky
... rion is a stocky rod-shaped particle w~t h an apical envelope extension. The nucleocdpsid is cylindr~cal with asymmetric ends, and has a superfic~al segmented appearance. The pattern of degradat~on confirms that the nucleocapsid is a cylinder formed by stacks of rlngs, which are in turn composed of 2 robvs of regularly spaced subunits. WSSV replication takes place in the nucleus and is f~rst indicated by chromatin margination and nuclear hypertrophy. Viral morphogenesis begins by the formation of membranes d e novo in the nucleoplasm and by the elaboration of segmented, empty, long tubules. These tubules break into fragments to form naked empty nucleocapsids. After that, membranes envelop the capsids leavlng an open extremity. The nucleoproteins, which have a filamentous appearance, enter the capsid through this open end. When the core is completely formed, the envelope narrows at the open end and forms the apical tail of the mature virion.