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Studies on the antibody responses to foot-and-mouth disease vaccine and the carrier state of virus in swine
Chuan, Tan Aik
Serum neutralization test
Liquid-phase blocking enzyme-linked immunosorbent assay
Reverse transcription-polymerase chain reaction
|摘要:||針對四場曾感染口蹄疫豬場之母豬及小豬進行血清學及帶原狀態之追蹤研究。血清及咽喉液樣本採自曾感染口蹄疫之母豬及以不同商業化油劑疫苗免疫後之小豬，和組織樣本採自二月齡前之小豬。以血清中和試驗(Serum Neutralization Test)及液相-阻斷酵素免疫吸附法(Liquid-phase blocking Enzyme-linked Immunosorbent Assay) 檢測其抗體力價。以及應用反轉錄-聚合鏈反應(Reverse transcription-polymerase chain reaction, RT-PCR) 技術偵測咽喉食道液及組織樣本中之病毒核酸。結果顯示大部份供試母豬血清中和抗體力價皆大於等於724倍，ELISA抗體於試驗期間都很高，部份高達2896倍，小豬於一月齡時之移行抗體力價也都很高（平均中和抗體:log2 7.19-8.9, 平均ELISA抗體: log2 6.7-8.8）。小豬經免疫後，幾乎沒有中和抗體反應，而四場中呈現ELISA抗體反應僅有二場。以RT-PCR 偵測咽喉液及組織樣本並沒有檢出病毒的核酸。另外，為探討本省豬口蹄疫感染場使用口蹄疫疫苗後之抗體反應，取二豬場分別為A及B場，A場70頭仔豬分為四組(A-1, A-2, A-3, A-4)，B場60頭仔豬分為三組（B-1, B-2, B-3）。A場前三組及B場三組之仔豬，以不同廠牌O1 Campos口蹄疫油劑疫苗免疫。A-1及B-1組於3週齡，A-2及B-2組於5週齡和A-3及B-3組於8週齡各免疫一次，各組隔一個月後再補強一次。A場之A-4組則於21週齡以二劑量免疫一次。血清中和試驗及ELISA檢測結果顯示仔豬於一週齡時之移行抗體很高（平均中和抗體可達log2 9.5, 平均ELISA抗體可達log2 10.1）。於12週齡以後免疫小豬有呈現中和抗體反應，而於8週齡以後免疫就有呈現ELISA抗體反應。仔豬之移行抗體很高時，經口蹄疫油劑疫苗免疫後，其抗體反應會受到移行抗體之干擾。同時，為了解小豬移行抗體之衰減，取三組小豬於出生後至8週齡或至105日齡期間採取血液樣本。以血清中和試驗檢測其中和抗體力價，移行抗體之半衰期分別為10.25、13.09及9.21天。然而，本試驗結果顯示，為了降低對本病具感受性豬隻的比率，應在移行抗體下降後於適當時間免疫豬隻。本試驗結果可供有關單位及相關業者對口蹄疫免疫計畫與防疫策略的擬定或修正之參考。|
The following studies on serologic surveillance and carrier state to aim directly at four Foot-and-mouth disease (FMD) infected pig farms were carried out. Samples of serum and esophageal-pharyngeal fluid were collected from the sows of four pig farms with FMD history and piglets after vaccination with different commercial oil emulsified vaccines. Tissue samples were also collected from the piglets before two months old. The antibody titers were detected by using both methods of serum neutralization test (SNT) and liquid-phase blocking enzyme-linked immunosorbent assay (LPB-ELISA). Viruses in esophageal-pharyngeal fluid and tissue samples were monitored by reverse transcription-polymerase chain reaction (RT-PCR) technique. The result indicated that the neutralizing and ELISA antibody titers of sow sera were extremely high level during experiment period and also piglets aged one month had high level of maternal antibodies. Almost no neutralizing antibody responses were obtained, but ELISA antibody responses of 2 farms were observed after vaccination. No virus was evident in esophageal-pharyngeal fluid and tissue samples by detection of RT-PCR. On the other hand, to search for understanding the antibody response of vaccinated piglets from the farm with FMD history, seventy and 60 piglets were selected from two A and B, and divided into 4 (A-1, A-2, A-3, A-4) and 3 (A-1, B-2, B-3) groups, respectively. Serum samples were taken regular interval for five to six months from piglets. First three groups of both farm piglets which had been vaccinated at 3 (A-1, B-1), 5 (A-2, B-2) and 8 (A-3, B-3) weeks old and boosted at one month after first vaccination and group A-4 was vaccinated at 21 weeks old with two dose FMD vaccine once. The results indicated that all piglets at one week old having high maternal antibodies were detected by SNT and LPB-ELISA. Neutralizing antibody responses were obtained for piglets vaccinated after 12 weeks old, and the ELISA antibody responses of the piglets with vaccinated after 8 weeks old were obtained. Meanwhile, in order to understanding the decline of maternal antibody, three groups of the piglets were selected and blood samples were collected from piglets periodically for 8 weeks or until 105 days after birth and antibody titers were detected by using SNT. The observed half life of maternally antibodies were 10.25, 13.09 and 9.21 days, respectively. A certain degree of suppression of postvaccinal response was observed during the high maternal antibody of piglets. However, our results suggest that in order to reduce the proportion of pigs susceptible to infection it is advisable to immunize pigs when the maternal antibody is declined. This result could provide a reference to draw up or revise the vaccination program and prevention strategy for relative producer and administrator.
|Appears in Collections:||獸醫學系所|
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