重组戊型肝炎病毒抗原免疫恒河猴及其对病毒攻击的保护

目的：了解重组抗原免疫恒河猴的抗体应答情况及其对病毒攻击的保护作用。方法：利用大肠杆菌表达的戊型肝炎（HEV）病毒3个不同的片段,分别为Agl(ORF2 C端431aa)、Ag2(ORF2 C端128aa片段）、Ag3[ORF3 122aa与ORF2 6287－6404碱基编码的39aa片段以及C端128aa依次以（Gly)n短臂连接的嵌合抗原]免疫恒河猴,用ELISA方法检测IgG抗体水平,3周后达到较高水平应答时,用HEV阳性粪便样静脉注射进行攻击,经肝脏病理切片观察、血清IgG、丙氨酸转氨酶（ALT）水平测定及粪便排毒的RT－nPCR检测来评价抗原对病毒攻击的保护作用。结果：对照组3只猴中两只发现肝脏组织产生明显的病理性改变,而免疫了抗原的试验组12只猴正常;对照组均在攻毒后3－4周发生ALT异常,为正常值的10－20倍,而试验组有部分猴不同程度轻微的ALT异常,其余正常;试验组免疫抗原后IgG水平迅速上升,滴度可达1：12800;对照组粪便中病毒RNA的检出在攻毒后7－50d左右,而试验组7－21d内以低水平存在。结论：重组的抗原片段诱发机体产生针对HEV的抗体应签,能够抑制HEV感染引起的肝炎症状的产生。

Vaccination of rhesus monkeys with recombinant antigen fragments and protection from hepatitis E virus infection

OBJECTIVE: To observe anti-HEV IgG response to vaccination of recombinant antigen fragments and evaluate its protection from Hepatitis E Virus infection in rhesus monkeys (Macaca mulatta). METHODS: Twelve monkeys were divided into three groups and immunized respectively with three different recombinant antigens: namely Ag1 (carboxyl terminal 431 amino acids of ORF2), Ag2 (128aa fragment at the carboxyl terminal of ORF2), and Ag3 (full length ORF3 ligated with two ORF2 fragments encoded by 6743-7126nt and 6287-6404nt). The monkeys were challenged intravenously with fecal suspension from experimentally infected rhesus monkeys, and the other three monkeys served as the placebo group for challenge with HEV. The dynamic changes of the levels of ALT and anti-HEV IgG were examined. Pathological changes of liver tissue were observed by light microscope. Excretion of virus was detected by RT-nPCR. RESULTS: Hepatic histopathology of two monkeys in the placebo group was consistent with acute viral hepatitis, and ALT was elevated 3-4 weeks after inoculated with virus, up to 10-20 times higher than normal level. The liver tissue of monkeys immunized with antigen kept normal, ALT in several monkeys elevated mildly, and anti-HEV IgG conversation occurred at 1-2 weeks after vaccination, with the titer reaching 1:12,800. The virus RNA could be detected by RT-nPCR from days 7 to 50 in monkeys of control group, and from days 7 to 21 in vaccinated monkeys after challenged with virus. CONCLUSIONS: The recombinant antigens could induce the production of anti-HEV IgG, which protected rhesus monkeys from acute Hepatitis symptoms related to HEV infection.