C Terminus of Infectious Bursal Disease Virus Major Capsid Protein VP2 Is Involved in Definition of the T Number for Capsid Assembly

ABSTRACT Infectious bursal disease virus (IBDV), a member of the Birnaviridae family, is a double-stranded RNA virus. The IBDV capsid is formed by two major structural proteins, VP2 and VP3, which assemble to form a T=13 markedly nonspherical capsid. During viral infection, VP2 is initially synthesized as a precursor, called VPX, whose C end is proteolytically processed to the mature form during capsid assembly. We have computed three-dimensional maps of IBDV capsid and virus-like particles built up by VP2 alone by using electron cryomicroscopy and image-processing techniques. The IBDV single-shelled capsid is characterized by the presence of 260 protruding trimers on the outer surface. Five classes of trimers can be distinguished according to their different local environments. When VP2 is expressed alone in insect cells, dodecahedral particles form spontaneously; these may be assembled into larger, fragile icosahedral capsids built up by 12 dodecahedral capsids. Each dodecahedral capsid is an empty T=1 shell composed of 20 trimeric clusters of VP2. Structural comparison between IBDV capsids and capsids consisting of VP2 alone allowed the determination of the major capsid protein locations and the interactions between them. Whereas VP2 forms the outer protruding trimers, VP3 is found as trimers on the inner surface and may be responsible for stabilizing functions. Since elimination of the C-terminal region of VPX is correlated with the assembly of T=1 capsids, this domain might be involved (either alone or in cooperation with VP3) in the induction of different conformations of VP2 during capsid morphogenesis.

Download Full-text

Simultaneous alteration of residues 279 and 284 of the VP2 major capsid protein of a very virulent Infectious Bursal Disease Virus (vvIBDV) strain did not lead to attenuation in chickens

Virology Journal ◽

10.1186/s12985-014-0199-7 ◽

2014 ◽

Vol 11 (1) ◽

Cited By ~ 6

Author(s):

Nawel Ben Abdeljelil ◽

Neila Khabouchi ◽

Selma Kassar ◽

Khaled Miled ◽

Samir Boubaker ◽

...

Keyword(s):

Capsid Protein ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Major Capsid Protein ◽

Infectious Bursal Disease ◽

Bursal Disease

Download Full-text

Infectious Bursal Disease Virus Capsid Assembly and Maturation by Structural Rearrangements of a Transient Molecular Switch

Journal of Virology ◽

10.1128/jvi.00077-07 ◽

2007 ◽

Vol 81 (13) ◽

pp. 6869-6878 ◽

Cited By ~ 37

Author(s):

Daniel Luque ◽

Irene Saugar ◽

José F. Rodríguez ◽

Nuria Verdaguer ◽

Damiá Garriga ◽

...

Keyword(s):

Capsid Protein ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Scaffolding Protein ◽

Infectious Bursal Disease ◽

Capsid Assembly ◽

Protein Oligomerization ◽

Structural Protein ◽

Bursal Disease ◽

Α Helix

ABSTRACT Infectious bursal disease virus (IBDV), a double-stranded RNA (dsRNA) virus belonging to the Birnaviridae family, is an economically important avian pathogen. The IBDV capsid is based on a single-shelled T=13 lattice, and the only structural subunits are VP2 trimers. During capsid assembly, VP2 is synthesized as a protein precursor, called pVP2, whose 71-residue C-terminal end is proteolytically processed. The conformational flexibility of pVP2 is due to an amphipathic α-helix located at its C-terminal end. VP3, the other IBDV major structural protein that accomplishes numerous roles during the viral cycle, acts as a scaffolding protein required for assembly control. Here we address the molecular mechanism that defines the multimeric state of the capsid protein as hexamers or pentamers. We used a combination of three-dimensional cryo-electron microscopy maps at or close to subnanometer resolution with atomic models. Our studies suggest that the key polypeptide element, the C-terminal amphipathic α-helix, which acts as a transient conformational switch, is bound to the flexible VP2 C-terminal end. In addition, capsid protein oligomerization is also controlled by the progressive trimming of its C-terminal domain. The coordination of these molecular events correlates viral capsid assembly with different conformations of the amphipathic α-helix in the precursor capsid, as a five-α-helix bundle at the pentamers or an open star-like conformation at the hexamers. These results, reminiscent of the assembly pathway of positive single-stranded RNA viruses, such as nodavirus and tetravirus, add new insights into the evolutionary relationships of dsRNA viruses.

Download Full-text

The Last C-Terminal Residue of VP3, Glutamic Acid 257, Controls Capsid Assembly of Infectious Bursal Disease Virus

Journal of Virology ◽

10.1128/jvi.78.7.3296-3303.2004 ◽

2004 ◽

Vol 78 (7) ◽

pp. 3296-3303 ◽

Cited By ~ 31

Author(s):

Christophe Chevalier ◽

Jean Lepault ◽

Bruno Da Costa ◽

Bernard Delmas

Keyword(s):

Glutamic Acid ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Virus Assembly ◽

Infectious Bursal Disease ◽

Capsid Assembly ◽

Assembly Process ◽

Small Proteins ◽

C Terminus ◽

Bursal Disease

ABSTRACT Infectious bursal disease virus (IBDV) is a nonenveloped virus with an icosahedral capsid composed of two proteins, VP2 and VP3, that derive from the processing of the polyprotein NH2-pVP2-VP4-VP3-COOH. The virion contains VP1, the viral polymerase, which is both free and covalently linked to the two double-stranded RNA (dsRNA) genomic segments. In this study, the virus assembly process was studied further with the baculovirus expression system. While expression of the wild-type polyprotein was not found to be self-sufficient to give rise to virus-like particles (VLPs), deletion or replacement of the five C-terminal residues of VP3 was observed to promote capsid assembly. Indeed, the single deletion of the C-terminal glutamic acid was sufficient to induce VLP formation. Moreover, fusion of various peptides or small proteins (a green fluorescent protein or a truncated form of ovalbumin) at the C terminus of VP3 also promoted capsid assembly, suggesting that assembly required screening of the negative charges at the C terminus of VP3. The fused polypeptides mimicked the effect of VP1, which interacts with VP3 to promote VLP assembly. The C-terminal segment of VP3 was found to contain two functional domains. While the very last five residues of VP3 mainly controlled both assembly and capsid architecture, the five preceding residues constituted the VP1 (and possibly the pVP2/VP2) binding domain. Finally, we showed that capsid formation is associated with VP2 maturation, demonstrating that the protease VP4 is involved in the virus assembly process.

Download Full-text

Partial protection against infectious bursal disease virus through DNA-mediated vaccination with the VP2 capsid protein and chicken IL-2 genes

Vaccine ◽

10.1016/j.vaccine.2003.09.021 ◽

2004 ◽

Vol 22 (9-10) ◽

pp. 1249-1259 ◽

Cited By ~ 30

Author(s):

Diane J Hulse ◽

Carlos H Romero

Keyword(s):

Capsid Protein ◽

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Infectious Bursal Disease ◽

Partial Protection ◽

Bursal Disease

Download Full-text

Genomic sequence of infectious bursal disease virus from Zambia suggests evidence for genome re-assortment in nature

Onderstepoort Journal of Veterinary Research ◽

10.4102/ojvr.v79i2.473 ◽

2012 ◽

Vol 79 (2) ◽

Cited By ~ 2

Author(s):

Christopher J. Kasanga ◽

T. Yamaguchi ◽

H.M. Munang’andu ◽

P.N. Wambura ◽

K. Ohya ◽

...

Keyword(s):

Disease Virus ◽

Infectious Bursal Disease Virus ◽

Genomic Sequence ◽

Rna Virus ◽

Virulent Strain ◽

Amino Acid Sequences ◽

Infectious Bursal Disease ◽

Nucleotide Homology ◽

Reassortant Strain ◽

Bursal Disease

Infectious bursal disease virus (IBDV) is a bi-segmented RNA virus, which belongs to the genus Avibirnavirus of the family Birnaviridae. Two serotypes, 1 and 2, exist in IBDV. The serotype 1 IBDVs are the causative agents of infectious bursal disease (IBD) in chickens worldwide and lead to immunosuppression in young birds. Genome re-assortment has been speculated to occur and contribute to the emergence of new IBDV strains. However, evidence was lacking until recently when two re-assortant viruses were detected in China. In this study, we determined the complete nucleotide sequence of an IBDV, designated KZC-104, from a confirmed natural IBD outbreak in Lusaka, Zambia in 2004. The genome consisted of 3074 and 2651 nucleotides in the coding regions of segments A and B, respectively. Alignment of both nucleotide and deduced amino acid sequences, and phylogenetic analysis revealed that the genome segment A of KZC-104 was derived from a very virulent strain, whereas its segment B was derived from a classical attenuated strain. On BLAST search, the full-length segments A and B sequences showed 98% closest nucleotide homology to the very virulent strain D6948 and 99.8% closest nucleotide homology to the classical attenuated strain D78, respectively. This is a unique IBDV reassortant strain, which has emerged in nature involving segment B of a live attenuated vaccine. This observation provides direct evidence for the involvement of vaccine strains in the emergence of reassortant IBDV in the field. Taken together, these findings suggest an additional risk of using live IBDV vaccines, which may act as genetic donors for genome re-assortment. Further studies are required to investigate the epidemiology and biological characteristics of reassortant strains so that the appropriate and safe IBDV vaccines can be recommended.

Download Full-text