Critical domains for HIV-1 entry through atypical coreceptor usage

描述（由申请人提供）：绝大多数 HIV-1 毒株通过与 CCR5 和 CXCR4 两个辅助受体之一相互作用进入 CD4 靶细胞。人们认为替代辅助受体不用于原发性临床感染。然而，我们最近发现了一种传播/创始人（T/F）病毒（ZP6248），其在体外利用多种 CD4 细胞系以及原代人 CD4 T 细胞和巨噬细胞上的 CCR5 和 CXCR4 辅助受体的能力严重受损，但在急性感染期间复制到高血浆病毒载量。与总是使用 CCR5 作为辅助受体的所有其他 T/F 病毒相比，ZP6248 在体外测定中最有效地使用辅助受体 GPR15。 ZP6248 罕见的 V3 冠尖中的单一突变 (E314G) 恢复了其在 CCR5 细胞中的感染性，但降低了其在 GPR15 细胞中的复制能力。在其他病毒骨架中的同一位置引入谷氨酸会导致辅助受体使用的显着改变，但不会使它们在 GPR15 细胞中具有感染性。这是第一个证明 HIV-1 可以使用 CCR5 和 CXCR4 以外的辅助受体来建立临床感染的病例。因此，了解在不使用 CCR5 或 CXCR4 作为辅助受体的情况下在人类中建立原发性 HIV-1 感染所涉及的机制非常重要。此外，令人惊讶的是，V3 冠尖的单个氨基酸替换导致不同病毒主链中辅助受体的使用显着改变。这些发现提供了一个独特的模型来研究 V3 冠尖和各种辅助感受器之间的精确相互作用。因此，我们将使用这种独特的病毒作为模型来解决以下基本生物学问题，这些问题对于理解这种不断进化的病毒病原体的辅助受体向性至关重要：（i）具有非典型辅助受体使用的传播的HIV-1变体使用哪些新的感染机制，以及控制辅助受体向性的包膜糖蛋白中的基序是什么； (ii)，V3 冠尖中的单个氨基酸取代引起的构象变化如何使病毒能够采样替代的辅助受体以建立临床感染。这项工作对于我们理解和预期病毒-宿主协同进化至关重要，这种进化将推动 HIV-1 流行病的未来。

DESCRIPTION (provided by applicant): The great majority of HIV-1 strains enter CD4+ target cells by interacting with one of two coreceptors, CCR5 and CXCR4. It has been considered that alternative coreceptors are not been used for primary clinical infection. However, we recently discovered a transmitted/founder (T/F) virus (ZP6248) that was profoundly impaired in its ability to utilize CCR5 and CXCR4 coreceptors on multiple CD4+ cell lines as well as primary human CD4+ T cells and macrophages in vitro, yet replicated to a high plasma viral load during acute infection. In contrast to all other T/F viruses that invariably use CCR5 as a coreceptor, ZP6248 uses the coreceptor GPR15 most efficiently in in vitro assays. A single mutation (E314G) in the rare V3 crown tip of ZP6248 restored its infectivity in CCR5+ cells, but reduced its ability to replicate in GPR15+ cells. Introduction of glutamic acid at this same position in other virus backbones leads to significant alterations of coreceptor usage, but does not render them infectious in GPR15+ cells. This is the first case demonstrating that HIV-1 can use coreceptors other than CCR5 and CXCR4 to establish clinical infection. Thus, it will be important to understand what are the mechanisms involved in establishing a primary HIV-1 infection in humans without the use of CCR5 or CXCR4 as coreceptors. In addition, it is striking that a single amino acid substitution at the V3 crown tip leads to significantly altered coreceptor usage in different virus backbones. These findings provide a unique model to study the precise interactions between the V3 crown tip and various coreceptors. Thus, we will use this unique virus as a model to address the following fundamental biological questions that are critical for understanding of coreceptor tropism of this evolving viral pathogen: (i), what novel infection mechanisms are used by a transmitted HIV-1 variant with atypical coreceptor usage and what are the motifs in the envelope glycoprotein that govern the coreceptor tropism; (ii), how conformational changes caused by a single amino acid substitution in the V3 crown tip allows the virus to sample alternative coreceptors to establish clinical infection. This work is central t our understanding and anticipation of virus-host coevolution that will drive the future of the HIV-1 epidemic.