The role of glycosylation in determining the immunogenicity of influenza C virus glycoprotein

本研究的目的是了解糖基化在确定流感病毒糖蛋白gp88免疫原性中的作用。为此，利用7株抗C/Ann Arbor/1/50株gp88的单抗，比较了gp88与在衣霉素存在下合成的非糖基化形式(T76)的抗原性。这些单抗可分为A和B两组，A组抑制病毒的血凝、溶血和传染性，而B组不抑制病毒的凝集、溶血和传染性。放射免疫沉淀实验显示，B组3株抗体均与T76和gp88呈阳性反应。相反，A组的4个抗体中有3个根本不沉淀T76，仅与该组的另一抗体沉淀少量的多肽。Western印迹分析还表明，变性的gp88与B组抗体发生反应，但不与A组抗体反应。由此，我们得出结论，gp88的糖基化选择性地影响A组抗体识别的生物活性和构象依赖表位的完整性。因此，可以合理地假设，在没有糖基化的情况下，gp88糖蛋白可能无法达到适当的构象，因此可能无法诱导中和抗体。

The aim of this study is to understand the role of glycosylation in determining the immunogenicity of influenza C virus glycoprotein, gp88. To this goal, the antigenicity of gp88 was compared with its nonglycosylated form (T76) synthesized in the presence of tunicamycin, utilizing seven monoclonal antibodies raised against gp88 of the C/Ann Arbor/1/50 strain. These monoclonal antibodies could be classified into two groups, A and B. Group A inhibits hemagglutination, hemolysis and infectivity of the virus whereas group B does not. Radioimmunoprecipitation experiments revealed that three antibodies in group B were all reactive with T76 as well as with gp88. In contrast, three out of four antibodies in group A did not precipitate T76 at all, and only a limited amount of the polypeptide was precipitated with the other antibody of this group. Western blot analysis also showed that denatured gp88 blotted on nitrocellulose was reactive with group B antibodies but not with group A. From these observations, we conclude that glycosylation of gp88 selectively influences the integrity of biologically active and conformation-dependent epitopes recognized by group A antibodies. It is reasonable to assume, therefore, that in the absence of glycosylation, the gp88 glycoprotein may fail to attain an appropriate conformation, and as a result, may be unable to elicit neutralizing antibodies.