Yeast-Elicited Cross-Reactive Antibodies to HIV Env Glycans Efficiently Neutralize Virions Expressing Exclusively High-Mannose N-Linked Glycans
Yeast-Elicited Cross-Reactive Antibodies to HIV Env Glycans Efficiently Neutralize Virions Expressing Exclusively High-Mannose N-Linked Glycans
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DOI：
10.1128/jvi.01349-10
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发表时间：
2011-01-01
影响因子：
5.4
通讯作者：
Doms, Robert W.
中科院分区：
文献类型：
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作者：
Agrawal-Gamse, Caroline;Luallen, Robert J.;Doms, Robert W.
HIV包膜蛋白(Env)用一层厚厚的多糖来掩盖保守结构域，逃避宿主体液免疫反应。广谱中和抗体2G12与HIV Env上的一组特定的高甘露糖多聚糖结合，表明多糖保护层也可以作为中和抗体的靶标。我们已经描述了一个三重突变的酿酒酵母菌株，它表达与2G12结合的高甘露糖糖蛋白。当用来免疫兔子时，这种酵母会产生与gp120相关的糖链结合的抗体，但不能中和病毒。在这里，我们试图确定这些不一致结果的原因。三种2G12活性酵母糖蛋白结合的血清的亲和纯化表明，这些蛋白可以吸附80%与gp120糖链结合的抗体。尽管这些甘露糖特异性抗体与单体gp120结合，但不能结合细胞表面表达的三聚体环境蛋白。然而，当在甘露糖苷酶抑制剂Kifunensine存在的情况下表达Env以迫使高甘露糖在所有位置保留时，纯化的抗体获得了结合三聚体Env的能力，并能够强烈和广泛地中和在这些条件下产生的病毒。综上所述，这些数据表明，三重突变酵母菌株能够诱导出与HIV包膜上的高甘露糖结合的抗体，但只有当它们以天然环境三聚体中没有的方式显示时才能产生抗体。这意味着，用于呈现高甘露糖多聚糖的蛋白质支架的潜在结构可能对于激发识别三聚体环境并中和病毒的抗体至关重要。
The HIV envelope (Env) protein uses a dense coat of glycans to mask conserved domains and evade host humoral immune responses. The broadly neutralizing antibody 2G12, which binds a specific cluster of high-mannose glycans on HIV Env, shows that the glycan shield can also serve as a target for neutralizing antibodies. We have described a triple mutant Saccharomyces cerevisiae strain that expresses high-mannose glycoproteins that bind to 2G12. When used to immunize rabbits, this yeast elicits antibodies that bind to gp120-associated glycans but fail to neutralize virus. Here we sought to determine the reason for these discordant results. Affinity purification of sera over columns conjugated with three 2G12-reactive yeast glycoproteins showed that these proteins could adsorb 80% of the antibodies that bind to gp120 glycans. Despite binding to monomeric gp120, these mannose-specific antibodies failed to bind cell surface-expressed trimeric Env. However, when Env was expressed in the presence of the mannosidase inhibitor kifunensine to force retention of high-mannose glycans at all sites, the purified antibodies gained the abilities to bind trimeric Env and to strongly and broadly neutralize viruses produced under these conditions. Combined, these data show that the triple mutant yeast strain elicits antibodies that bind to high-mannose glycans presented on the HIV envelope, but only when they are displayed in a manner not found on native Env trimers. This implies that the underlying structure of the protein scaffold used to present the high-mannose glycans may be critical to allow elicitation of antibodies that recognize trimeric Env and neutralize virus.