重组幽门螺杆菌疫苗免疫保护机制的研究

Study of protective immune response induced by attenuated Salmonella typhimurium expressing H.pylori antigens in mice

目的 研究以减毒鼠伤寒沙门菌为载体构建的重组幽门螺杆菌 (Hp)疫苗诱导小鼠产生保护性免疫应答的机制。方法 将表达Hp尿素酶B亚单位 (UreB)、黏附素 (HpaA)及尿素酶B亚单位/黏附素融合蛋白 (UreB/HpaA)的减毒鼠伤寒沙门菌 (Salmonellatyphimurium)给小鼠分别灌胃 ,另设单纯减毒鼠伤寒沙门菌和生理盐水免疫鼠为对照。免疫 4周后以Hp活菌攻击 ,观察各组小鼠的免疫保护率 ,攻击前后血清中抗Hp抗体IgG1、IgG2a和IgA的变化 ,小鼠脾脏和胃黏膜中γ干扰素 (IFN γ)和白介素 4 (IL 4 )mRNA表达变化。结果 UreB、HpaA及UreB/HpaA组的免疫保护率分别为 5 0 % ,4 1%和 77%。和生理盐水组相比 ,攻击前各鼠伤寒沙门菌免疫组IgG1、IgG2a均轻度升高而IgA无变化 ,攻击后各鼠伤寒沙门菌免疫组IgG2a升高显著并以UreB/HpaA组为最 ,而IgG1和IgA的升高无统计学差异。胃黏膜攻击前生理盐水组无IFN γ表达 ,其余各组均 10 0 %表达 ;攻击后生理盐水组IFN γ轻度表达 ,但仍明显低于各鼠伤寒沙门菌免疫组。IL 4在攻击前后各组均无表达。脾IFN γ和IL 4在所有组攻击前后均全部表达。

Objective To study the protective immune response induced by attenuated Salmonella typhimurium expressing Helicobacter pylori (H. pylori) antigens in mice. Methods Mice were orally immunized with attenuated Salmonella typhimurium expressing one of the following H. pylori antigens: UreB, HpaA and UreB/HpaA fusion protein. Mice immunized with attenuated Salmonella typhimurium and normal saline respectively were used as control. Four weeks after immunization mice were challenged with H. pylori. The protective rate after challenge, serum anti H.pylori IgG1,IgG2a and IgA antibodies, IFN γ and IL 4 mRNA expression of gastric mucosa and spleen in different groups were studied before and after challenge. Results Protective rates of UreB, HpaA and UreB/HpaA groups were 50%, 41% and 77% respectively. When compared with those of normal saline group, both IgG1 and IgG2a of all Salmonella typhimurium immunized groups were increased mildly before challenge while IgA was not increased; After challenge all Salmonella typhimurium immunized groups especially UreB/HpaA group had a significant high levels of IgG2a but not the levels of IgG1 and IgA when compared with normal saline group. Expression rate of IFN γ in the gastric mucosa of all Salmonella typhimurium immunized groups was higher than that of normal saline group both before and after H.pylori challenge. However, IL 4 expression was not detected in all groups before and after challenge. Both IFN γ and IL 4 were expressed in spleen of all groups before and after challenge. Conclusions Attenuated Salmonella typhimurium expressing H. pylori antigens can induce a predominant TH 1 protective immune response in mice.