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Bulletin No. 22 - Summer 2005
VirologyPMWS-PCV2-PCVD-PDNS
THOMAS P, OPRIESSNIG T, MC KEOWN N, MENG XJ, HALBUR P
Effect of PCV2 passive antibody levels on immunization with chimeric PCV1-2 vaccine and challenge with wild-type PCV2.
American Association of Swine Veterinarians - Proceedings, 2005, 23-25
In a previous study (see Bibliographical Bulletin of July 2004), the ORF2 capsid protein of PCV2 expressed by a chimeric PCV1-2 resulted immunogenic and the infection with the chimeric PCV1-2 induced only a limited infection with mild pathological lesions. In this study, the interference of different levels (negative/low/high) of passively-acquired antibodies with vaccine-induced protective immunity was investigated. The experimental design was based on 7 groups of 3-week old piglets consisting of 2 groups of pigs considered negative for antibody to PCV2 (ELISA S/P ratio <0.2), 2 groups of pigs with low antibody titers (ELISA S/P ratio of 0.2-0.5), 2 groups of pigs with high antibody titers (ELISA S/P ratio >0.5) and one group with variable titers. Each group with negative/low/high titers was either vaccinated with PCV1-2 chimera or inoculated a wild type PCV2. All groups were subsequently challenged with a wild type PCV2 6 weeks following vaccination/inoculation (at 9 weeks of age). A protective immunity against wild type PCV2 challenge was achieved in PCV1-2 chimera-vaccinated pigs with negative and low (S/P<0.5) passive antibody levels. In conclusion, a clear interference between vaccination and passively-acquired antibodies has been evidenced. Therefore, a vaccination of piglets with the chimeric PCV1-2 that takes place 6 weeks prior to the expected exposure to PCV2 may give good results if piglets have low PCV2 antibody titers.
