Identification of the Nucleocapsid, Tegument, and Envelope Proteins of the Shrimp White Spot Syndrome Virus Virion

Abstract

The protein components of the white spot syndrome virus (WSSV) virion have been well established by proteomic methods, and at least 39 structural proteins are currently known. However, several details of the virus structure and assembly remain controversial, including the role of one of the major structural proteins, VP26. In this study, Triton X-100 was used in combination with various concentrations of NaCl to separate intact WSSV virions into distinct fractions such that each fraction contained envelope and tegument proteins, tegument and nucleocapsid proteins, or nucleocapsid proteins only. From the protein profiles and Western blotting results, VP26, VP36A, VP39A, and VP95 were all identified as tegument proteins distinct from the envelope proteins (VP19, VP28, VP31, VP36B, VP38A, VP51B, VP53A) and nucleocapsid proteins (VP664, VP51C, VP60B, VP15). We also found that VP15 dissociated from the nucleocapsid at high salt concentrations, even though DNA was still present. These results were confirmed by CsCl isopycnic centrifugation followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and liquid chromatography-nanoelectrospray ionization-tandem mass spectrometry, by a trypsin sensitivity assay, and by an immunogold assay. Finally, we propose an assembly process for the WSSV virion.White spot syndrome virus (WSSV) is a widespread and disastrous viral pathogen of cultured shrimp that also attacks crabs and crayfish as well as many other crustaceans (3,10,16,22). The WSSV virion is an enveloped particle of approximately 275 by 120 nm with an olivaceous-to-bacilliform shape, and it has a nucleocapsid (300 by 70 nm) with periodic striations (22,25). The most obvious feature of WSSV is the presence of a thread-like extension at one end of the virion (2, 25), which gives this virus the family name Nimaviridae (13).A virion is a complex assembly of macromolecules exquisitely suited for the protection and delivery of viral genomes. Its structural proteins are particularly important, since these proteins are the first molecules to interact with the host, and they therefore play critical roles in cell targeting as well as in the triggering of host defenses. Recently, thanks to the introduction of proteomic methods, the total number of known WSSV structural proteins increased to 39 (5, 17).Immunogold electron microscopy (IEM) has been used to identify VP28, VP26, VP31, VP51C, VP36B, VP41A, VP12B, and VP180 as envelope proteins (4,5,8,9,(28)(29)(30) and VP664 as a nucleocapsid protein (7). Other studies (1,6,(18)(19)(20) that combined detergent treatment and Western blotting confirmed and expanded most of these results (VP28, VP19, and VP73 as envelope proteins; VP24, VP15, and VP35 as nucleocapsid proteins) but also identified VP26 as a nucleocapsid protein.Here for the first time we embark on a systematic study of the structural proteins of WSSV that not only allows us to resolve the question of VP26's location but also reveals the existence of a previously unreported component of the WSSV virion. This co...

Pathological changes in Fenneropenaeus indicus experimentally infected with white spot virus and virus morphogenesis

“…The observations are similar to that of P. monodon (Durand et al, 1997;Wang et al, 1999;Tsai et al, 2006) except the formation of a tail like extension by the envelop. We could not find such an elongation of envelop in any of our preparation, instead fusion of trilaminar circular vesicles containing nuclear materials with the enveloped capsid was observed.…”

VP292 of White spot syndrome virus Interacts with VP26

“…Both VP37 and VP292 interacting with VP26 suggested that the similar domain of VP37 and VP292 might interact with VP26. VP26 is considered to be a tegument protein and it lies between the virus envelope and nucleocapsid [10]. VP26 was found to interact with viral nucleocapsid in vitro [14], as well as VP28 [16].…”

“…It is an enveloped virus with a 305 kb double-stranded circular DNA genome and approximately 180 open reading frames (ORFs) [12,17]. Over 50 structural protein genes and several non-structural protein genes have been characterized [6,10,16,18]. Envelope proteins are important for virus infection and assembly.…”

CHARACTERISTICS OF VIRAL PROTEIN, VP-15, OF WHITESPOT SYNDROME VIRUS ISOLATED FROM INFECTED TIGER SHRIMP Penaeus monodon (Fabricius, 1798)

“…Recently, the smallest nucleocapsid protein was discovered in WSSV and called VP-15. It is thought to be involved in WSSV genomic packaging based on its DNA binding and condensing abilities (Ying, 2004); Tsai et al, 2006;Sangsuriya et al, 2011).…”