Zhang Jun, Gu Ying, Ge Sheng X, Li Shao W, He Zhi Q, Huang Guo Y, Zhuang Hui, Ng Mun H, Xia Ning S
The Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, China.
Vaccine. 2005 Apr 22;23(22):2881-92. doi: 10.1016/j.vaccine.2004.11.065.
The dimeric form of the recombinant peptide (E2), comprising amino acid 394-606 of the capsid protein of hepatitis E virus (HEV), is strongly recognized by HEV reactive human serum, and when used as a vaccine, it protects rhesus monkeys against experimental HEV infection. In this work, the relationship of E2 to HEV has been probed using three murine monoclonal antibodies, 8C11, 13D8 and 8H3, all of which react predominantly against the E2 dimer, and can effect immune capture of the virus as well. 8C11 and 8H3 were further found to neutralize HEV infectivity in animals. Cross-blocking patterns between these antibodies discerned two spatially separate antigenic domains, one identified by 8C11 and 13D8, and the other, by 8H3. Kinetic studies using BIAcore biosensor suggest that the epitope to which 8H3 is directed is partially masked, and thus has limited access by the native antibody. However, this is not the case with the smaller Fab. Access to the 8H3 epitope was enhanced by the binding of 8C11, and inhibited by the binding of 13D8 to a distal site on the peptide. Similar to the effects of binding 8H3 to E2, 8C11 was found to enhance immune capture by 8H3, while 13D8 was inhibitory. Moreover, 8C11 and 8H3 act synergistically to neutralize HEV infectivity. The parallel cross-reaction patterns that these antibodies exhibit against the peptide and the virus, respectively, implicate two interacting conformationally dependent neutralization sites on the HEV particle. These sites might cooperate in the adsorption and penetration of the HEV virus.
重组肽（E2）的二聚体形式由戊型肝炎病毒（HEV）衣壳蛋白的394 - 606位氨基酸组成，能被HEV反应性人血清强烈识别，用作疫苗时可保护恒河猴免受实验性HEV感染。在本研究中，使用三种鼠单克隆抗体8C11、13D8和8H3探究了E2与HEV的关系，这三种抗体均主要与E2二聚体反应，且都能实现病毒的免疫捕获。进一步发现8C11和8H3可中和动物体内的HEV感染性。这些抗体之间的交叉阻断模式识别出两个空间上分离的抗原结构域，一个由8C11和13D8识别，另一个由8H3识别。使用BIAcore生物传感器进行的动力学研究表明，8H3所针对的表位部分被掩盖，因此天然抗体对其的识别受限。然而，较小的Fab片段情况并非如此。8C11的结合增强了对8H3表位的识别，而13D8与肽远端位点的结合则抑制了这种识别。与8H3与E2结合的效果类似，发现8C11可增强8H3的免疫捕获作用，而13D8则具有抑制作用。此外，8C11和8H3协同作用以中和HEV感染性。这些抗体分别针对肽和病毒所表现出的平行交叉反应模式，暗示了HEV颗粒上两个相互作用的构象依赖性中和位点。这些位点可能在HEV病毒的吸附和穿透过程中协同发挥作用。
