Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute , Boston, Massachusetts, USA.
Department of Microbiology, Harvard Medical School , Boston, Massachusetts, USA.
J Virol. 2023 Sep 28;97(9):e0059223. doi: 10.1128/jvi.00592-23. Epub 2023 Sep 11.
The human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer mediates entry into host cells by binding receptors, CD4 and CCR5/CXCR4, and fusing the viral and cell membranes. In infected cells, cleavage of the gp160 Env precursor yields the mature Env trimer, with gp120 exterior and gp41 transmembrane Env subunits. Env cleavage stabilizes the State-1 conformation, which is the major target for broadly neutralizing antibodies, and decreases the spontaneous sampling of more open Env conformations that expose epitopes for poorly neutralizing antibodies. During HIV-1 entry into cells, CD4 binding drives the metastable Env from a pretriggered (State-1) conformation into more "open," lower-energy states. Here, we report that changes in two dissimilar elements of the HIV-1 Env trimer, namely particular gp120 glycans and the gp41 fusion peptide-proximal region (FPPR), can independently modulate the stability of State 1. Individual deletion of several gp120 glycans destabilized State 1, whereas removal of a V1 glycan resulted in phenotypes indicative of a more stable pretriggered Env conformation. Likewise, some alterations of the gp41 FPPR decreased the level of spontaneous shedding of gp120 from the Env trimer and stabilized the pretriggered State-1 Env conformation. State-1-stabilizing changes were additive and could suppress the phenotypes associated with State-1-destabilizing alterations in Env. Our results support a model in which multiple protein and carbohydrate elements of the HIV-1 Env trimer additively contribute to the stability of the pretriggered (State-1) conformation. The Env modifications identified in this study will assist efforts to characterize the structure and immunogenicity of the metastable State-1 conformation. IMPORTANCE The elicitation of antibodies that neutralize multiple strains of HIV-1 is an elusive goal that has frustrated the development of an effective vaccine. The pretriggered shape of the HIV-1 envelope glycoprotein (Env) spike on the virus surface is the major target for such broadly neutralizing antibodies. The "closed" pretriggered Env shape resists the binding of most antibodies but is unstable and often assumes "open" shapes that elicit ineffective antibodies. We identified particular changes in both the protein and the sugar components of the Env trimer that stabilize the pretriggered shape. Combinations of these changes were even more effective at stabilizing the pretriggered Env than the individual changes. Stabilizing changes in Env could counteract the effect of Env changes that destabilize the pretriggered shape. Locking Env in its pretriggered shape will assist efforts to understand the Env spike on the virus and to incorporate this shape into vaccines.
人类免疫缺陷病毒 1（HIV-1）包膜糖蛋白（Env）三聚体通过结合受体 CD4 和 CCR5/CXCR4 并融合病毒和细胞膜来介导进入宿主细胞。在受感染的细胞中，gp160Env 前体的裂解产生成熟的 Env 三聚体，具有 gp120 外和 gp41 跨膜 Env 亚基。Env 的裂解稳定了 State-1 构象，这是广泛中和抗体的主要靶标，并降低了更开放的 Env 构象自发采样的可能性，这些构象会暴露出对中和作用较差的抗体的表位。在 HIV-1 进入细胞的过程中，CD4 结合促使不稳定的 Env 从预先触发（State-1）构象转变为更“开放”、能量更低的状态。在这里，我们报告说，HIV-1 Env 三聚体中两个不同元素的变化，即特定的 gp120 聚糖和 gp41 融合肽近端区（FPPR），可以独立地调节 State1 的稳定性。单独删除几个 gp120 聚糖会使 State1 不稳定，而删除一个 V1 聚糖会导致更稳定的预先触发的 Env 构象表型。同样，gp41 FPPR 的一些改变降低了 gp120 从 Env 三聚体自发脱落的水平，并稳定了预先触发的 State-1 Env 构象。稳定 State-1 的变化是累加的，并且可以抑制 Env 中与稳定 State-1 破坏变化相关的表型。我们的结果支持这样一种模型，即 HIV-1 Env 三聚体的多个蛋白和碳水化合物元素累加有助于预先触发（State-1）构象的稳定性。本研究中鉴定的 Env 修饰将有助于表征不稳定的 State-1 构象的结构和免疫原性。
重要性 诱导中和多种 HIV-1 株的抗体是一个难以实现的目标，这使得有效的疫苗开发受挫。HIV-1 包膜糖蛋白（Env）刺突在病毒表面的预触发形状是此类广泛中和抗体的主要靶标。“封闭”的预先触发的 Env 形状抵抗大多数抗体的结合，但不稳定，并且经常呈现出产生无效抗体的“开放”形状。我们确定了 Env 三聚体中蛋白质和糖成分的特定变化，这些变化稳定了预先触发的形状。这些变化的组合甚至比单个变化更有效地稳定预触发的 Env。稳定 Env 可以抵消使预触发形状不稳定的 Env 变化的影响。将 Env 锁定在其预先触发的形状将有助于理解病毒上的 Env 刺突并将该形状纳入疫苗中。
