| Summary: | 碩士 === 國立中興大學 === 獸醫學系 === 94 === Atrophic rhinitis (AR), of which the major causative factor has been determined to be the toxin of Pasteurella multocida (PMT), is a widely prevalent, contagious disease of swine, which can cause atrophy of nasal turbinate bones, abnormal skeleton development, and growth retardation, and leading to severe economic losses in the swine industry. Direct application of PMT as vaccine has been proved to be effective in prevention of AR (Boring et al., 1990). However, low yield of PMT from the culture, which was usually regarded as a major difficulty in its vaccine preparation, has prompted scientist to use recombinant PMT as subunit vaccine, of which the effectiveness has also been confirmed via nasal application in animal trials.
The attempt of this study was to employ Lactobacillus reuteri, the producer of a wide-spectrum antimicrobial substance termed reuterin, as a vaccine carrier, bringing PMT into animal’s gastrointestinal tract to induce the mucous membrane-immune response. Hence, the nucleotide sequence of the Tox1 fragment in PMT (PMT-Tox1), being verified to have a strong immune nature, was selected and cloned into the plasmid p203, an expression-secretion vector constructed by our laboratory, to generate the recombinant plasmid p203-T1, which was subsequently transformed into L. reuteri DSM20016 and Lac. reuteri 3-3, respectively.
As expression of the cloned PMT-Tox1 in both L. reuteri strains transformed with p203-T1 (L. reuteri /p203-T1 vaccine) was confirmed to be successful, mice experiment was immediately followed to evaluate the efficacy of our vaccine system. Preliminary results had shown that significant IgA-ELISA titer (P<0.05) was detected in mice applied with L. reuteri /p203-T1, while IgG-ELISA titer in the same experiment was also raised, but not significant. To the effects of different bacteria strains in carrying p203-T1, L. reuteri 3-3/ p203-T1 was found to have a better immune response than that of L. reuteri DSM20016/p203-T1. Also noteworthy was that nasal application in this study generally induce a higher antibody titer than that via the oral administration.
In conclusion, a novel AR vaccine system, which can induce a significant IgA-ELISA titer (P<0.05) against PMT, has been developed in this study. Further swine experiment is needed to evaluate its efficacy in protecting animals from AR infection.
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