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第19号公告板 - Fall 2004
18th IPVS Congress, Hamburg, Germany, 2004Porcine Reproductive and Respiratory Syndrome (PRRS)
MCCAW M, MURTAUGH M, LASTER S, ROBERTS J, ERICKSON G
PRRSV rORF specific ELISA antibody responses following repeated homologous wild-type virus challenges
Proceedings of the 18th IPVS Congress, Hamburg, Germany, 2004 - Volume 1:36
Previous studies have already shown that, following multiple immunizations with an homologous PRRSV strain, sows could still result ELISA seronegative a few weeks after the last immunization. This study reports the same results in 68 PRRSV-negative 6-month old barrows which received a total of 6 injections of the same PRRSV virulent strain each at a one-month interval. Blood samples collected in all animals 3 weeks following each injection were tested PRRSV ELISA and serum neutralization (SN) antibodies. Unlike ELISA antibodies, SN antibodies were still detected 4 months after the last immunization. In addition, ORF7 nucleocapsid protein curve was shown to follow that of ELISA antibodies whereas ORF5 envelope protein and ORF6 matrix protein were shown to have the same dynamic as SN antibodies. This suggest that the antibody response is initially directed against nucleocapsid protein and is subsequently redirected against envelope and matrix proteins, which could explain the rapid return to ELISA seronegative status observed in vaccinated or infected pigs. Consequently, a low ELISA antibody response following vaccination or infection could indicate a shift toward a protective immune response.
