Key result
Classical swine fever vaccination reduces viral heterogeneity via strong selective pressure, driving 16 unique SNPs.
Why the study?
Little is known about how vaccination impacts the selective pressures acting on the classical swine fever virus.
Vaccination against classical swine fever virus imposes strong selective pressure on the virus, leading to distinct evolutionary changes and emergence of novel SNPs in vaccinated animals.
Answers are grounded in this paper and cite their sources.
May select for CSFV variants in swine; leaves open implications for vaccine durability and surveillance.
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.
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Fahnøe et al. (2019) studied Classical swine fever. Vaccination against classical swine fever vs. Naïve pigs was evaluated on Evolutionary changes in virus populations. Vaccination against classical swine fever imposed strong selective pressure on the virus, leading to the emergence of 16 unique non-synonymous SNPs and a loss of viral heterogeneity.
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