Abstract
Picornavirus capsids are assembled from 60 copies of a capsid precursor via a pentameric assembly intermediate or ‘pentamer’. Upon completion of virion assembly, a maturation event induces a final cleavage of the capsid precursor to create the capsid protein VP4, which is essential for capsid stability and entry into new cells. For the picornavirus foot-and-mouth disease virus (FMDV), intact capsids are temperature and acid-labile and can disassemble into pentamers. During disassembly, capsid protein VP4 is lost, presumably altering the structure and properties of the resulting pentamers. The purpose of this study was to compare the characteristics of recombinant “assembly” and “disassembly” pentamers. We generated recombinant versions of these different pentamers containing an engineered cleavage site to mimic the maturation cleavage. We compared the sedimentation and antigenic characteristics of these pentamers using sucrose density gradients and reactivity with an antibody panel. Pentamers mimicking the assembly pathway sedimented faster than those on the disassembly pathway suggesting that for FMDV, in common with other picornaviruses, assembly pentamers sediment at 14S whereas only pentamers on the disassembly pathway sediment at 12S. The reactivity with anti-VP4 antibodies was reduced for the 12S pentamers, consistent with the predicted loss of VP4. Reactivity with other antibodies was similar for both pentamers suggesting that major antigenic features may be preserved between the VP4 containing assembly pentamers and the disassembly pentamers lacking VP4.
Highlights
IntroductionThe Picornaviridae are a family of viruses with small (approximately 30 nm) nonenveloped icosahedral capsids containing a single copy of positive sense RNA genome
The Picornaviridae are a family of viruses with small nonenveloped icosahedral capsids containing a single copy of positive sense RNA genome
The viral RNA is infectious and when it enters the cytoplasm of cells, a single open reading frame (ORF) is translated into a polyprotein containing both structural and non-structural proteins [2]
Summary
The Picornaviridae are a family of viruses with small (approximately 30 nm) nonenveloped icosahedral capsids containing a single copy of positive sense RNA genome. The family contains many important pathogens of humans and animals including poliovirus, human rhinovirus and foot-and-mouth disease (FMD) virus (FMDV). The global burden of FMD on livestock is significant and can incur large economic costs due to production losses, trade restrictions and control strategies including vaccination [1]. The FMDV capsid assembles via multimerisation of precursor subunits which encapsidate a single copy of the viral RNA genome. The viral RNA is infectious and when it enters the cytoplasm of cells, a single open reading frame (ORF) is translated into a polyprotein containing both structural (capsid precursor) and non-structural proteins [2]. During translation the capsid precursor, P1-2A, is released from the polyprotein by cleavage at its
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