Qiu Z, Tufaro F, Gillam S
Department of Pathology, University of British Columbia, Research Centre, Vancouver, Canada.
Virology. 1992 Oct;190(2):876-81. doi: 10.1016/0042-6822(92)90929-j.
Rubella virus E1 glycoprotein contains three functional N-linked glycosylation sites. The role of N-linked glycosylation on the antigenicity and immunogenicity of E1 glycoprotein was studied using vaccinia recombinants expressing E1 glycosylation mutants. Expressed E1 glycosylation mutant proteins were recognized by a panel of E1-specific monoclonal antibodies in radioimmunoprecipitation, immunofluorescence, and immunoblotting, indicating that carbohydrate side chains on E1 are not involved in the constitution of epitopes recognized by these monoclonal antibodies. This observation was further supported by the fact that removal of oligosaccharides on E1 by glycosidase digestion did not significantly change the antigenicity of E1. All the glycosylation mutants were capable of eliciting anti-RV E1 antibodies. The single glycosylation mutants (G1, G2, and G3), but not the double mutant (G23) or the triple mutant (G123), were found to be capable of inducing virus neutralizing antibodies. Among the single glycosylation mutants, only G2 and G3 were active in producing hemagglutination inhibition antibodies in mice. Our findings suggest that although carbohydrate on E1 is not directly involved in the antigenic structures of E1, it is important in maintaining proper protein folding and stable conformation for expression of immunological epitopes on E1.
风疹病毒E1糖蛋白含有三个功能性N - 连接糖基化位点。利用表达E1糖基化突变体的痘苗重组体研究了N - 连接糖基化对E1糖蛋白抗原性和免疫原性的作用。在放射免疫沉淀、免疫荧光和免疫印迹实验中，表达的E1糖基化突变体蛋白被一组E1特异性单克隆抗体识别，这表明E1上的碳水化合物侧链不参与这些单克隆抗体所识别表位的构成。糖苷酶消化去除E1上的寡糖后，E1的抗原性没有显著变化，这一事实进一步支持了该观察结果。所有糖基化突变体均能够引发抗风疹病毒E1抗体。发现单糖基化突变体（G1、G2和G3）能够诱导病毒中和抗体，而双突变体（G23）和三突变体（G123）则不能。在单糖基化突变体中，只有G2和G3在小鼠体内产生血凝抑制抗体方面具有活性。我们的研究结果表明，虽然E1上的碳水化合物不直接参与E1的抗原结构，但它对于维持E1上免疫表位表达的正确蛋白质折叠和稳定构象很重要。
