Multiple Nucleocapsid Structural Forms of Shrimp White Spot Syndrome Virus Suggests a Novel Viral Morphogenetic Pathway

Abstract

White spot syndrome virus (WSSV) is a very large dsDNA virus. The accepted shape of the WSSV virion has been as ellipsoidal, with a tail-like extension. However, due to the scarcity of reliable references, the pathogenesis and morphogenesis of WSSV are not well understood. Here, we used transmission electron microscopy (TEM) and cryogenic electron microscopy (Cryo-EM) to address some knowledge gaps. We concluded that mature WSSV virions with a stout oval-like shape do not have tail-like extensions. Furthermore, there were two distinct ends in WSSV nucleocapsids: a portal cap and a closed base. A C14 symmetric structure of the WSSV nucleocapsid was also proposed, according to our Cryo-EM map. Immunoelectron microscopy (IEM) revealed that VP664 proteins, the main components of the 14 assembly units, form a ring-like architecture. Moreover, WSSV nucleocapsids were also observed to undergo unique helical dissociation. Based on these new results, we propose a novel morphogenetic pathway of WSSV.

In Silico Evaluation of the PCR Performance of Different Tests for Detection of WSSV

“…The primers described by Durand and Lightner [18], Lo et al [22], Nunan and Lightner [40], Yuan et al [44], and Zhu and Quan [45], target different regions of the ORF wsv419, which encodes VP664, the major WSSV structural protein of the nucleocapsid and the largest viral structural protein known, which is distributed with a periodicity that matches the characteristic stacked ring subunits that appear as striations [69]. The alignment of the sequences that the primers described by Durand and Lightner [18] amplify is highly conserved, with no gaps or insertions detected.…”