Virus adaptation and selection following challenge of animals vaccinated against classical swine fever virus

Ulrik Fahnøe, Anders Gorm Pedersen, Camille Melissa Johnston, Richard J. Orton, Dirk Höper, Martin Beer, Jens Bukh, Graham J. Belsham, Thomas Bruun Rasmussen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

6 Citations (Scopus)
133 Downloads (Pure)

Abstract

Vaccines against classical swine fever have proven very effective in protecting pigs from this deadly disease. However, little is known about how vaccination impacts the selective pressures acting on the classical swine fever virus (CSFV). Here we use high-throughput sequencing of viral genomes to investigate evolutionary changes in virus populations following the challenge of naïve and vaccinated pigs with the highly virulent CSFV strain "Koslov". The challenge inoculum contained an ensemble of closely related viral sequences, with three major haplotypes being present, termed A, B, and C. After the challenge, the viral haplotype A was preferentially located within the tonsils of naïve animals but was highly prevalent in the sera of all vaccinated animals. We find that the viral population structure in naïve pigs after infection is very similar to that in the original inoculum. In contrast, the viral population in vaccinated pigs, which only underwent transient low-level viremia, displayed several distinct changes including the emergence of 16 unique non-synonymous single nucleotide polymorphisms (SNPs) that were not detectable in the challenge inoculum. Further analysis showed a significant loss of heterogeneity and an increasing positive selection acting on the virus populations in the vaccinated pigs. We conclude that vaccination imposes a strong selective pressure on viruses that subsequently replicate within the vaccinated animal.

Original languageEnglish
Article number932
JournalViruses
Volume11
Issue number10
ISSN1999-4915
DOIs
Publication statusPublished - 2019

Keywords

  • Classical swine fever virus
  • CSFV
  • Deep sequencing
  • Haplotype selection
  • Vaccination
  • Viral populations
  • Virulence
  • Virus evolution

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