title: A virulent isolate of yellow head nidovirus contains a deformed envelope glycoprotein gp116.
abstract: Yellow head virus (YHV) is a highly virulent pathogen of penaeid shrimp. An isolate obtained from Penaeus vannamei during a yellow head disease outbreak in February 2006 in Ratchaburi Province, Thailand was purified following passage in experimentally infected shrimp. SDS-PAGE of purified virions indicated that envelope glycoprotein gp116 in the Ratchaburi/2006 isolate was smaller and relatively less abundant than in the Chachoengsao/1998 YHV reference strain. The variant gp116 reacted poorly in immunoblots with a gp116 mouse monoclonal antibody and a rabbit anti-serum to a baculovirus-expressed, C-terminally truncated, [His](6)-tagged gp116 that reacted strongly with gp116 of the homologous Chachoengsao/1998 strain. The anti-gp116 polyclonal serum also failed to neutralise the infectivity of the Ratchaburi/2006 isolate in in-vivo assays conducted in P. vannamei, but effectively neutralised the infectivity of the reference strain. Sequence analysis of the approximately 6.0 kb structural protein gene region and 3'UTR of the Ratchaburi/2006 isolate indicated >99.9% overall nucleotide identity with the Chachoengsao/1998 strain. However, in Ratchaburi/2006 a deletion in ORF3, corresponding to 54 amino acids near the N-terminal signal peptidase cleavage site of gp116, resulted in the loss of six conserved cysteine residues and two predicted N-glycosylation sites. Analysis of this ORF3 region in 25 viruses representing each of the six genotypes in the yellow head complex identified this modified form of gp116 in two other virulent YHV isolates classified as genotype 1b. The data indicate that, although the deletion causes a significant structural deformation of gp116 which reduces its incorporation into virions and eliminates the major neutralisation sites, the virus remains highly infectious, virulent and fit for survival.
authors.affiliation: National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency, Phathumthani, Thailand.
authors.forename: Nusra
authors.initials: N
authors.lastname: Sittidilokratna
authors.forename: Charoonroj
authors.initials: C
authors.lastname: Chotwiwatthanakun
authors.forename: Priyanjalie K M
authors.initials: PK
authors.lastname: Wijegoonawardane
authors.forename: Sasimanas
authors.initials: S
authors.lastname: Unajak
authors.forename: Anutara
authors.initials: A
authors.lastname: Boonnad
authors.forename: Watcharakorn
authors.initials: W
authors.lastname: Wangnai
authors.forename: Sarawut
authors.initials: S
authors.lastname: Jitrapakdee
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Cowley
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Walker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D004196:Disease Outbreaks; D005838:Genotype; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics; D006458:Hemolymph / Q000821:virology; D051379:Mice; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D030341:Nidovirales Infections / Q000235:genetics*; D016366:Open Reading Frames; D033561:Penaeidae / Q000235:genetics* / Q000821:virology; D011817:Rabbits; D046828:Roniviridae / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D016415:Sequence Alignment; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics*; D014764:Viral Proteins / Q000302:isolation & purification; D014774:Virulence
chemical_list: D006023:Glycoproteins; D014759:Viral Envelope Proteins; D014764:Viral Proteins