Abstract
In recent years, porcine circovirus type 2d (PCV2d) has achieved a dominant position worldwide. Various PCV2d capsid-based vaccines have been used to alleviate concerns regarding the emergence of the variant. This study aimed to determine the dosage of recombinant PCV2d capsid protein to induce protective efficacy against experimental challenge with a virulent PCV2d strain. Conventional 3-week-old pigs were intramuscularly inoculated with different doses of the protein (60, 20, 10 and 2 µg). Four weeks after vaccination, all pigs were challenged with pathogenic PCV2d (SNU140003), which was isolated from a farm severely experiencing PCV2-associated disease in Korea. Vaccination with greater than 10 µg of the capsid protein caused a significant (p < 0.05) reduction in PCV2d viremia, lymphoid lesions and lymphoid PCV2 antigen levels in vaccinated challenged pigs compared to unvaccinated challenged pigs. The vaccination also resulted in significantly higher (p < 0.05) titers of neutralizing antibodies against PCV2d. However, the pigs vaccinated with 2 µg had significantly lower neutralizing antibody titers than the other vaccinated groups. They showed a similar level of challenged PCV2d in serum and lymphoid lesion score compared to unvaccinated challenged pigs. The difference in efficacy among the vaccinated groups indicates that there may be a baseline dosage to induce sufficient neutralizing antibodies to prevent viral replication in pigs. In conclusion, at least 10 µg dosage of capsid protein is essential for stable protective efficacy against PCV2d in a pig model.
Highlights
Porcine circovirus type 2 virus (PCV2)-associated disease (PCVAD) is one of the most severe threats to the swine industry
Post-weaning multisystemic wasting syndrome and porcine dermatitis and nephropathy syndrome have been associated with PCVAD [3,4,5]
Based on numerous etiological and pathological evidence, PCV2 has been an obligatory agent for PCVAD, but several other infectious and noninfectious factors have been reported to contribute to the manifestation of the symptoms through various mechanisms [6]
Summary
Porcine circovirus type 2 virus (PCV2)-associated disease (PCVAD) is one of the most severe threats to the swine industry. PCV2a was the predominant genotype among the PCV2 variants when the initial vaccine was being developed [9,10]. After the first commercial PCV2a-based vaccine was launched in 2007, PCV2b supplanted PCV2a as the predominant genotype worldwide to avoid vaccine immunity [11,12,13]. Another genotypic shift has occurred with PCV2d becoming the predominant strain in the global pig population, replacing PCV2a and PCV2b [14]. In terms of an outbreak of PCVAD caused by PCV2d in PCV2a-vaccinated herds, this second shift has raised questions about the efficacy of the PCV2a vaccine against the PCV2d genotype [15,16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
