Investigation on neutralizing efficacy against verotoxin and resistance to protease of bovine immune colostral antibody in mice and beagle dogs

口服后2小时，牛初乳抗Verotoxin2(VT2)抗体未灭活。然而，Beagle犬的血清抗体活性比给药前降低了15%。此外，S-Ig A的抗体活性没有变化，但口服2小时后，Ig G和Ig M的抗体活性下降。给Beagle犬口服无抗体牛初乳乳清，接种产生VT2的大肠杆菌O157：H7后，粪便中VT2含量逐渐下降，接种后第5天回升，而牛初乳抗体在口服牛初乳抗体后第二天显著降低粪便中VT2含量。用VT2、血清抗体或牛初乳抗体免疫的奶牛，在注射VT2后1h分别口服从牛初乳乳清中分离出的免疫球蛋白类抗体。给予无菌生理盐水作为对照，所有小鼠均死亡。接种S-Ig A或Ig M类抗体或牛初乳抗体后，小鼠存活率为93.3%。免疫球蛋白抗体和血清抗体的存活率分别为80%和60%。这些结果表明，抗VT的牛初乳抗体通过抵抗蛋白酶而中和了小肠中的VT的活性。

The bovine colostral antibody against verotoxin2 (VT2) was not inactivated after 2 hours after oral administration. However, the activity of serum antibody reduced 15% of prior administration in the small intestine of beagle dogs. Furthermore, the antibody activity of S-IgA did not change; however, the activity of IgG and IgM antibodies decreased after 2 hours of oral administration. With oral administration of bovine colostral whey without antibody in beagle dogs inoculated Escherichia coli (E.coli) O157:H7 producing VT2, the amount of VT2 in feces decreased gradually after administration and increased again at 5 days after inoculation, while bovine colostral antibody significantly reduced the amount of VT2 in feces the day after oral administration of bovine colostral antibody. Mice were administered orally each immunoglobulin class antibody isolated from bovine colostral whey obtained from cows immunized with VT2, serum antibody or bovine colostral antibody at 1h after administration of VT2. All mice died after administration of sterilized saline as control. The survival rate was 93.3% after administration of S-IgA or IgM class antibody, or bovine colostral antibody. The survival rates for IgG class antibody and serum antibody were 80% and 60%, respectively. These results suggest that bovine colostral antibody against VT neutralized the activity of in small intestine by resistance to protease.