Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA.
Department of Microbiology, Harvard Medical School, Boston, Massachusetts, USA.
J Virol. 2024 Feb 20;98(2):e0159423. doi: 10.1128/jvi.01594-23. Epub 2024 Jan 30.
The human immunodeficiency virus (HIV-1) envelope (Env) glycoprotein precursor (gp160) trimerizes, is modified by high-mannose glycans in the endoplasmic reticulum, and is transported via Golgi and non-Golgi secretory pathways to the infected cell surface. In the Golgi, gp160 is partially modified by complex carbohydrates and proteolytically cleaved to produce the mature functional Env trimer, which is preferentially incorporated into virions. Broadly neutralizing antibodies (bNAbs) generally recognize the cleaved Env trimer, whereas poorly neutralizing antibodies (pNAbs) bind the conformationally flexible gp160. We found that expression of bNAbs, pNAbs, or soluble/membrane forms of the receptor, CD4, in cells producing HIV-1 all decreased viral infectivity. Four patterns of co-expressed ligand:Env were observed: (i) ligands (CD4, soluble CD4-Ig, and some pNAbs) that specifically recognize the CD4-bound Env conformation resulted in uncleaved Envs lacking complex glycans that were not incorporated into virions; (ii) other pNAbs produced Envs with some complex carbohydrates and severe defects in cleavage, which were relieved by brefeldin A treatment; (iii) bNAbs that recognize gp160 as well as mature Envs resulted in Envs with some complex carbohydrates and moderate decreases in virion Env cleavage; and (iv) bNAbs that preferentially recognize mature Envs produced cleaved Envs with complex glycans in cells and on virions. The low infectivity observed upon co-expression of pNAbs or CD4 could be explained by disruption of Env trafficking, reducing the level of Env and/or increasing the fraction of uncleaved Env on virions. In addition to bNAb effects on virion Env cleavage, the secreted bNAbs neutralized the co-expressed viruses.IMPORTANCEThe Env trimers on the HIV-1 mediate virus entry into host cells. Env is synthesized in infected cells, modified by complex sugars, and cleaved to form a mature, functional Env, which is incorporated into virus particles. Env elicits antibodies in infected individuals, some of which can neutralize the virus. We found that antibodies co-expressed in the virus-producing cell can disrupt Env transit to the proper compartment for cleavage and sugar modification and, in some cases, block incorporation into viruses. These studies provide insights into the processes by which Env becomes functional in the virus-producing cell and may assist attempts to interfere with these events to inhibit HIV-1 infection.
人类免疫缺陷病毒（HIV-1）包膜（Env）糖蛋白前体（gp160）三聚体化，在内质网中被高甘露糖聚糖修饰，并通过高尔基体和非高尔基体分泌途径运输到感染细胞表面。在高尔基体中，gp160 被部分修饰为复合碳水化合物，并被蛋白水解切割，生成成熟的功能性 Env 三聚体，该三聚体优先被掺入病毒粒子中。广谱中和抗体（bNAb）通常识别切割的 Env 三聚体，而弱中和抗体（pNAb）则结合构象灵活的 gp160。我们发现，表达 bNAb、pNAb 或受体 CD4 的可溶性/膜形式均可降低 HIV-1 的病毒感染力。观察到四种共表达配体：Env 的模式：（i）专门识别 CD4 结合的 Env 构象的配体（CD4、可溶性 CD4-Ig 和一些 pNAb）导致未切割的 Env 缺乏复杂糖，这些糖不能被掺入病毒粒子中；（ii）其他 pNAb 产生具有一些复杂碳水化合物和严重切割缺陷的 Env，用布雷菲德菌素 A 处理可缓解这些缺陷；（iii）识别 gp160 以及成熟 Env 的 bNAb 导致具有一些复杂碳水化合物和中度降低病毒粒子 Env 切割的 Env；和（iv）优先识别成熟 Env 的 bNAb 在细胞和病毒粒子上产生具有复杂糖的切割 Env。共表达 pNAb 或 CD4 时观察到的低感染性可以通过破坏 Env 运输来解释，这会降低 Env 的水平和/或增加病毒粒子上未切割 Env 的比例。除了 bNAb 对病毒粒子 Env 切割的影响外，分泌的 bNAb 还中和了共表达的病毒。重要性 HIV-1 上的 Env 三聚体介导病毒进入宿主细胞。Env 在受感染的细胞中合成，经过复杂的糖修饰，然后切割形成成熟的、功能性的 Env，该 Env 被掺入病毒颗粒中。Env 在受感染的个体中引发抗体，其中一些可以中和病毒。我们发现，在产生病毒的细胞中共表达的抗体可以破坏 Env 向适当的切割和糖修饰隔室的转运，在某些情况下，阻止其掺入病毒中。这些研究提供了关于 Env 在产生病毒的细胞中变得功能化的过程的见解，并可能有助于尝试干扰这些事件以抑制 HIV-1 感染。
