Structure and dynamics of picornavirus capsids to inform vaccine design

Thesis

The physical properties of viral capsids are major determinants of vaccine efficacy for several picornaviruses which impact on human and animal health. Current picornavirus vaccines are frequently produced from inactivated virus. Inactivation often reduces the stability of the virus capsid, causing a problem for Foot and Mouth Disease Virus (FMDV) where certain serotypes fall apart into pentameric assemblies below pH 6.5 or at temperatures slightly above 37°C, destroying their effectiveness in eliciting a protective immune response. As a result, vaccines require a cold chain for storage and animals need to be frequently immunised.

FMDV is a member of the Aphthovirus genus of the Picornaviridae. Globally there are seven FMDV serotypes: O, A, Asia1, C and SAT-1, -2 and -3, contributing to a dynamic pool of antigenic variation. As part of collaboration between the Division of Structural Biology, Oxford University, The Pirbright Institute, Reading University and ARC, Ondespoort, South Africa we sought to rationally engineer thermo-stable FMDV capsids either as infectious copy virus or recombinant empty capsids with improved thermo-stability for improved vaccines. In this project, in silico molecular dynamics (MD) simulations, molecular modelling, free energy calculations, X-ray crystallography, electron microscopy and various biochemical/biophysical techniques were used to design and help characterise the capsids.

For the most unstable FMDV serotypes (O and SAT2), panels of stabilising mutants were characterised by MD. Promising candidates were then engineered and shown to confer increased thermo- and pH-stability. Thus, in silico predictions translate into marked stabilisation of both infectious and recombinant empty viral capsids. A novel in situ method was used to determine crystal structures for quality assessment and to verify that no unanticipated structural changes have occurred as a consequence of the modifications made. The structures of the wildtype and two of the stabilised mutants were solved and the antigenic surfaces shown to be unchanged.

Animal trials showed stabilised particles can generate a similar or improved neutralising antibody response compared to the traditional vaccines and may therefore lead to a new generation of stable and safe vaccines.

Authors: Kotecha, A

• Publication date: 2014
• DOI: 10.5287/ora-aovkmwxya
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: Oxford University, UK
• Language: English
• Keywords: Viruses; Picronavirus; Vaccine; FMDV
• Subjects: Vaccinology; Viruses; Bioinformatics (biochemistry); Molecular biophysics (biochemistry); Computational biochemistry; Biochemistry