中文摘要：

目的：比较基于恒定链片段的两种载体的免疫效果和作用机理。方法：分别构建了含新城疫病毒抗原表位F306和Ii不同片段的三个嵌合体（Ii-key/F306、Ii-key/F306/ND（两个氨基酸残基）和用抗原表位取代Ii-CLIP的Ii/F306）,经纯化后的融合蛋白免疫小鼠,并用ELISA检测其抗体效价。同时嵌合体与Mhc共转染COS7细胞,观察两者的细胞定位与结合。结果：Ii-key/F306免疫组比单独F306抗原肽免疫组的抗体效价提高2倍,Ii-key/F306/ND免疫组增至4倍,而Ii-F306免疫组只增强2.5倍。在与Mhc共转染的COS7细胞和免疫共沉淀中,Ii-key/F306和Ii-key/F306/ND既没有与MHCⅡ分子的膜共定位作用,也不能与后者结合;而Ii-F306却能与MHCⅡ分子在浆膜共定位,并与后者结合。结论：这些结果表明,嵌合体都具有增强免疫效果的作用,并提示Ii片段促进了抗原肽与MHCⅡ分子结合。

英文摘要：

Objective：To compare the effects of two vectors based on invariant chain（Ii） segments on the immune response.Methods： Three hybrids containing NDV epitope F306 and Ii segments,Ii-key/F306,Ii-key/F306/ND（two residues） and Ii/F306 in which CLIP was replaced by epitope F306,were reconstructed respectively.BALB/c mice were immunized with the purified fusion proteins and the antibody titers were detected with ELISA respectively.Meanwhile the hybrids and Mhc were co-transfected in COS7 cells to observe their location and binding.Results： The groups immunized with Ii-key/F306 or Ii-key/F306/DN had two-fold or four-fold higher antibody titers than that immunized with F306 alone respectively,but the group immunezed with Ii-F306 enhanced only two and a half-fold higher antibody titers.In the co-transfected COS7 cells,neither Ii-key/F306 nor Ii-key/F306/DN could co-locate on the plasma membrane or bind with MHC class Ⅱ molecule.However,Ii-F306 could co-locate and bind with MHC class Ⅱ molecule.Conclusion： These results showed that these hybrids could increase the immune response and suggested that Ii segments improved binding of the epitope to MHC class Ⅱ molecule.