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

2007 ◽  
Vol 81 (13) ◽  
pp. 6869-6878 ◽  
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.

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

2001 ◽  
Vol 75 (22) ◽  
pp. 10815-10828 ◽  
Author(s):  
José R. Castón ◽  
Jorge L. Martı́nez-Torrecuadrada ◽  
Antonio Maraver ◽  
Eleuterio Lombardo ◽  
José F. Rodrı́guez ◽  
...  
Keyword(s):  
Capsid Protein ◽  
Disease Virus ◽  
Infectious Bursal Disease Virus ◽  
Major Capsid Protein ◽  
Rna Virus ◽  
Three Dimensional ◽  
Infectious Bursal Disease ◽  
Capsid Assembly ◽  
C Terminus ◽  
Bursal Disease

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.

scholarly journals The expression in plants of an engineered VP2 protein of Infectious Bursal Disease Virus induces formation of structurally heterogeneous particles that protect from a very virulent viral strain

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0247134
Author(s):  
Carla Marusic ◽  
Charifa Drissi Touzani ◽  
Alessio Bortolami ◽  
Marcello Donini ◽  
Claudia Zanardello ◽  
...  
Keyword(s):  
Disease Virus ◽  
Infectious Bursal Disease Virus ◽  
Neutralizing Antibodies ◽  
Sucrose Density Gradient ◽  
Bursa Of Fabricius ◽  
Infectious Bursal Disease ◽  
Structural Protein ◽  
Vp2 Protein ◽  
Bursal Disease ◽  
Specific Pathogen

Infectious Bursal Disease Virus (IBDV), the etiological agent of Gumboro disease, causes mortality and immunosuppression in chickens and major losses to poultry industry worldwide. The IBDV major capsid protein VP2 is considered the best candidate for the production of novel subunit vaccines. This structural protein contains the major conformational epitopes responsible for the induction of IBDV neutralizing antibodies in chickens and has been demonstrated able to form supramolecular structures in yeast and insect cells. The aim of this study was to express an engineered version of the VP2 protein (His-pVP2) to verify its ability to self-assemble into virus-like particles in plants. The recombinant VP2 was transiently expressed by agroinfiltration in Nicotiana benthamiana and transmission electron microscopy of sucrose density gradient fractions revealed the presence of a mixed population of differently shaped particles ranging from spherical capsids, with a diameter between ~25 and ~70 nm, to tubular structures, with variable length (from 100 to 400 nm). The recombinant VP2-based particles when used for the intramuscular immunization of specific-pathogen-free chicks resulted able to induce the production of anti-IBDV specific antibodies at titers comparable to those induced by a commercial vaccine. Moreover, all the immunized birds survived to the challenge with a Moroccan very virulent IBDV strain with no major histomorphological alterations of the Bursa of Fabricius, similarly to what obtained with the commercial inactivated vaccine.

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