Abstract
BackgroundPost-weaning multisystemic wasting syndrome (PMWS) associated with PCV2 is one of the most costly diseases currently faced by the swine industry. The development of effective vaccines against PCV2 infection has been accepted as an important strategy in the prophylaxis of PMWS.MethodsIn the present study, a PK-15 cell-adapted formalin-inactivated prototype vaccine candidate was prepared using a strain of PCV2 from China. Inactivation of the virus was accomplished using a standard formalin inactivation protocol. The protective properties of the inactivated PCV2 vaccine were evaluated in piglets. Ten 28-day-old pigs were randomly assigned to two groups, each with five. Group 1 was vaccinated intramuscularly with the inactivated virus preparation; Group 2 received sterile PBS as a placebo. By 28 days post-vaccination (DPV), Groups 1 and 2 were challenged intranasally and intramuscularly with 5 × 107 TCID50 of a virulent PCV2 isolate.ResultsThe vaccinated pigs seroconverted to PCV2 and had high levels of serum antibodies to PCV2 at 28 days after vaccination, whereas the control pigs remained seronegative. No significant signs of clinical disease were recorded following the challenge with PCV2, but moderate amounts of PCV2 antigen were detected in most lymphoid organs of the control pigs. PCV2 was detected in two out of the five vaccinated pigs. Furthermore, pathological lesions and viremia were milder in the vaccinated group.ConclusionsThe obtained results indicate that the inactivated PCV2 virus vaccine with an oil adjuvant induce an immunological response in pigs that appears to provide protection from infection with PCV2. The vaccine, therefore, may have the potential to serve as a vaccine aimed to protect pigs from developing PMWS.
Highlights
Post-weaning multisystemic wasting syndrome (PMWS) associated with PCV2 is one of the most costly diseases currently faced by the swine industry
PCV2 has been associated with other swine diseases, such as porcine dermatitis and nephropathy syndrome (PDNS), porcine respiratory disease complex (PRDC) and reproductive failure, which are collectively referred to as PCVAD or PCV2-associated diseases, a name that the American Association of Swine Veterinarians (AASV) uses to group together all the diseases attributed to PCV2, including PMWS [14]
Previous studies have demonstrated that ORF1, -2 and −3 encode a 35.7 kDa replication (Rep) protein involved in virus replication [17], a 27.8 kDa capsid (Cap) protein involved in PCV2 immunogenicity [18,19,20] and a protein involved in PCV2-induced apoptosis [21], respectively
Summary
Post-weaning multisystemic wasting syndrome (PMWS) associated with PCV2 is one of the most costly diseases currently faced by the swine industry. The development of effective vaccines against PCV2 infection has been accepted as an important strategy in the prophylaxis of PMWS. Various PCV2 vaccines, including DNA vaccines [22,23], chimeric PCV1-2 vaccines [24] and subunit vaccines [25], have been described for the control of PCV2 infections Both DNA vaccination and subunit vaccination based on the ORF2 gene have shown relatively satisfactory immunization against PCV2, DNA vaccination is not suitable for clinical application because of the possibility of carcinogenesis [26]. The use of formalin inactivation for virus vaccine development is attractive from a safety perspective as the virus cannot revert to a virulent form, because there is no virus replication during immunization. The use of formalin to inactivate viruses is attractive from a manufacturing perspective as the inactivation process is relatively simple to develop
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