EHEC O157∶H7基因缺失突变株口服免疫小鼠的实验研究

Oral immunization of mice with stx/ler deletion mutant of EHEC O157: H7

目的 研究肠出血性大肠杆菌O15 7∶H7基因缺失突变疫苗候选株EHEC 86 - 2 4 (Δstx/ler)的安全性和免疫保护效果 ,为进一步的临床实验提供依据。方法 对出生 7d昆明鼠经口服途径进行免疫 ,分别在一次免疫和加强免疫 14d后以O15 7∶H7强毒株EDL933(NalR)攻毒 ,观察小鼠的发病情况、疫苗候选株的保护率及攻毒后的带菌消长情况。同时又作了被动免疫实验 ,成年母鼠间隔 14d口服免疫两次 ,所生乳鼠 7d攻毒。结果 疫苗株以 10倍于强毒株最小致死剂量口服接种无致病作用。疫苗株一次免疫保护率可达 6 0 %。因小鼠的易感性随日龄和体重的增加而降低 ,加强免疫后 ,对照组未能全部致死 (死亡 4 0 % ) ,而免疫组全部存活 ;攻毒后免疫组比对照组排菌时间显著缩短 (2 4h/ 2 16h)。两次口服免疫后血清IgG抗体效价达 1∶16 0 0。被动免疫保护率 10 0 %。结论 该突变株通过口服接种能够引起特异性免疫应答反应 。

To investigate the security and immunogenicity of stx/ler deletion mutant strain of Enterohemorrhagic Escherichia Coli O157∶H7,the first group of suckling mice was immunized orally with the mutant strain at 7 days of age and challenged with O157∶ H7 EDL933(Nal R) at 21 days of age. And the second group of suckling mice immunized orally twice at 7 days was 17 days of age and was infected orally with O157 EDL933 (Nal R) at 31 days of age. In another experiment, pregnant mice were vaccinated orally twice at intervals of 14 days. Subsequently, the titre of serum IgG of pregnant mice was tested by ELISA assay and whose suckling mice were infected orally at 7 days of age. The results showed that the ratio of immune protection of the first group was 60%. Immunized mice of the second group survived and no symptoms appeared after challenge. In contrast, 40% of unimmunized mice died after infection. And the time of the existence of O157∶H7 in the intestines of immunized mice was less than that of unimmunized mice (24 hours/216 hours). The titre of serum IgG of the immunized pregnant mice was 1∶1600. And the ratio of passive protection was 100%. It concludes that oral immunization can induce specific immune responses,and the mutant strain can be used as an attenuated vaccine candidate against EHEC O157∶H7.