Efficiently cleaved HIV-1 Envs are the closest mimics of functional Envs as they specifically expose only bNAb (broadly neutralizing antibody) epitopes and not non-neutralizing ones, making them suitable for developing vaccine immunogens. We have previously identified several efficiently cleaved Envs from clades A, B, C and B/C. We also described that truncation of the CT (C-terminal tail) of a subset of these Envs, but not others, impairs their ectodomain conformation/antigenicity on the cell surface in a CT conserved hydrophilic domain (CHD) or Kennedy epitope (KE)-dependent manner. Here, we report that those Envs (4 − 2.J41 and JRCSF), whose native-like ectodomain conformation/antigenicity on the cell surface is disrupted upon CT truncation, but not other Envs like JRFL, whose CT truncation does not have an effect on ectodomain integrity on the cell surface, are also defective in retrograde transport from early to late endosomes. Restoration of the CHD/KE in the CT of these Envs restores wild-type levels of distribution between early and late endosomes. In the presence of retrograde transport inhibitor Retro 2, cell surface expression of 4 − 2.J41 and JRCSF Envs increases [as does in the presence of Rab7a DN and Rab7b DN (DN: dominant negative)] but particle formation decreases for 4 − 2.J41 and JRCSF Env pseudotyped viruses. Our results show for the first time a correlation between CT-dependent, CHD/KE regulated retrograde transport and cell surface expression/viral particle formation of these efficiently cleaved Envs. Based on our results we hypothesize that a subset of these efficiently cleaved Envs use a CT-dependent, CHD/KE-mediated mechanism for assembly and release from late endosomes.

有效切割的 HIV-1 包膜是功能性包膜最接近的模拟物，因为它们只特异性暴露 bNAb（广泛中和抗体）表位，而不暴露非中和表位，这使得它们适合开发疫苗免疫原。我们之前已经从进化枝 A、B、C 和 B/C 中鉴定了几个有效切割的 Env。我们还描述了这些 Env 的一部分（而不是其他）的 CT（C 端尾部）截断会损害其在 CT 保守亲水结构域 (CHD) 或肯尼迪表位 (KE) 中细胞表面的胞外域构象/抗原性依赖方式。在这里，我们报告了这些 Env（4 − 2.J41 和 JRCSF），其细胞表面上的类天然胞外域构象/抗原性在 CT 截断时被破坏，但其他 Env（如 JRFL）则不然，其 CT 截断不会产生影响细胞表面的胞外域完整性，从早期内体到晚期内体的逆行运输也存在缺陷。这些 Envs CT 中 CHD/KE 的恢复恢复了早期内体和晚期内体之间分布的野生型水平。在逆行转运抑制剂 Retro 2 存在的情况下，4 − 2.J41 和 JRCSF Envs 的细胞表面表达增加[与 Rab7a DN 和 Rab7b DN（DN：显性失活）存在时的情况一样]，但 4 − 2 的颗粒形成减少.J41 和 JRCSF Env 假型病毒。我们的结果首次显示了 CT 依赖性、CHD/KE 调节的逆行转运与这些有效切割的 Env 的细胞表面表达/病毒颗粒形成之间的相关性。根据我们的结果，我们假设这些有效切割的 Env 的一部分使用 CT 依赖性、CHD/KE 介导的机制来组装并从晚期内体释放。