Abstract
Porcine circovirus type 2, the causative agent of porcine circovirus associated diseases (PCVAD), consists of three major genotypes PCV2a, 2b and 2d. Current commercial vaccines contain the first-identified PCV2a’s capsid protein or whole virions. Outbreaks of PCVAD, caused by the recently identified PCV2d in vaccinated herds have raised concerns regarding the efficacy of current PCV2a vaccines against PCV2d. Thus, the primary objective of this study was to assess the efficacy of a two-dose regimen for the recently reformulated Fostera PCV MetaStim vaccine, to determine if reformulation with the squalene oil adjuvant and two-dose regimen improves the threshold of protection enough to eliminate viremia in a vaccination and challenge model. Two groups of seven pigs each were vaccinated with the commercial vaccine or PBS, and challenged with the PCV2d virus. Strong pre-challenge virus neutralizing responses were detected against all three genotypes. Post-challenge viremia was not completely eliminated as expected but a 2 log10 mean reduction in viral load was achieved in vaccinated pigs. Vaccinated pigs had a mean score of 0 for pathological evaluation, while unvaccinated pigs had a score of 6.6. In conclusion, the reformulated Fostera PCV MetaStim PCV2a-based vaccine provided significant heterologous protection and was effective against PCV2d.
Highlights
Porcine circovirus type 2 (PCV2) is a small DNA virus, which causes post-weaning multi-systemic wasting disease syndrome (PMWS) in weanling piglets
All the 14 pigs selected for the study had a detectable but low PCV2 antibody titer
The antibody titers for vaccinated pigs were significantly higher than the unvaccinated group at all the time points after days post vaccination (DPV) 18 (Figure 1)
Summary
Porcine circovirus type 2 (PCV2) is a small DNA virus, which causes post-weaning multi-systemic wasting disease syndrome (PMWS) in weanling piglets. Despite the availability of effective commercial vaccines, PCV2 continues to be a significant economic burden on the swine industry, both as a primary pathogen and due to its effects in exacerbating coinfections [3,4]. The first PCV2 genotype that was distinguished both clinically and serologically from the non-pathogenic variant called PCV1, was designated as PCV2a. PCV2a were introduced in the U.S market in 2006 They were highly effective in preventing clinical signs and curtailing economic losses [5,6]. A DNA virus, the rates of mutation for PCV2 are comparable to that of RNA viruses. Co-infections of the same host with multiple genotypes of the virus, recombination and mutation events are factors that facilitate the emergence of new PCV2 variants in the field [7,8].
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