| Summary: | 博士 === 國立中興大學 === 獸醫學系 === 94 === In this study, three recombinant subunit Pasteurella multocida toxins (rsPMTs) were constructed and expressed successfully. These rsPMTs were non-toxic both in mice and swine and could induce PMT-specific antibody-secreting cells and cellular immunity in spleen. The rsPMT-immunized mice could survive the lethal dose challenge of authentic PMT, and the PMT-specific antibody-secreting cells (ASCs) increased significantly. In addition, immunized piglets generated higher neutralizing antibody titers after authentic PMT challenge or homologous antigen boost. Furthermore, pregnant sows immunized with rsPMT exhibited higher levels of maternal antibodies in colostrum than did those immunized with a conventional toxoid vaccine. Offspring from rsPMT vaccinated sows had better survival rate after challenge with a 5-fold lethal dose of authentic PMT and had better growth performance after challenge with a sublethal dose of toxin.
A total of 542 sows from 15 conventional farms were selected to evaluate the vaccine efficacy in field trials. The results indicated that 78.3% of multipara sows could generate higher protective maternal antibody titers than those with less parity. Moreover, there were 39.4% of gilts could still mount good protective antibody titer with 1:16 or higher. Furthermore, a conventional farm which had suffered from severe progressive atrophic rhinitis (PAR) was selected to estimate the vaccine efficacy. Twelve months after vaccination, the clinical symptoms of PAR were significantly decreased and the growth performance of fattening pigs improved remarkably as the period of gaining sufficient body weight for marketing was decreased by 14 days. These results demonstrated that a non-toxic AR-rsPMT is a potential candidate for the development of new generation vaccines against PAR in pigs.
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