对应用遗传工程活菌苗E.coli C_(600)(pMMO85)免疫母猪所产仔猪的攻击试验

应用遗传工程活菌苗E.coli C_(600)(pMMO85),在母猪预产前15～20d,经口服和皮下注射两种途径免疫接种。对免疫母猪所生仔猪,每头攻击E.coli C_(83549)(O149:k91:k(?)8_(?))强毒菌600亿后,再让其吸吮母乳,观察仔猪发生腹泻和排菌情况。结果,对照组3(?)头,在攻击后8～12h均发生腹泻,死亡31头(81.58％),存活仔猪7头,腹泻时间平均2.60d,排菌时间平均5d;而吸吮经两种途径免疫母猪乳汁的仔猪87头,发育正常,仅个别仔猪在攻击1d后发生轻度腹泻,一二天内均能自愈,排菌时间也较对照组大为缩短,平均1.28～1.35d。

Challenge Test of Suckling Piglets Borne by Pregnant Sows being Immunized with Recombinant Live Vaccine E. coli C600 (pMM085)

E.coli C600(PMMO85) constructed by genetic engineering efficiently expresses both K88ac and LT-B subunit antigens yet has no toxicity. Its protection efficacy was examined by challenge test. Newborn piglets suckled on immunized sows were significantly protected against death from diarrhea when challenged with virulent strain C83549 of E. coli bearing the homologous fimbriae and toxin. All 38 piglets in control group developed severe diarrhea, but only a few piglets in immune groups either by oral or injection means developed mild diarrhea. The average duration of diarrhea in control group, oral immune and injection group were 2.60, 0.60 and 0.26 days and bacterial excretion lasted 5.0, 1.35 and 1.28 days respectively. The mortality of control group was 81.58% (31/38), but all piglets of both immune groups survived. The results showed that protection efficacy of this vaccine is very remarkable.