Department of Infectious Diseases, Virology, University Hospital Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany.
Eur J Cell Biol. 2011 Nov;90(11):913-21. doi: 10.1016/j.ejcb.2010.09.010. Epub 2010 Nov 1.
Nef, a HIV-1 pathogenesis factor, elevates virus replication in vivo and thus progression to AIDS by incompletely defined mechanisms. As one of its biological properties, Nef enhances the infectivity of cell-free HIV-1 particles in single round infections, however it fails to provide a significant and amplifying growth advantage for HIV-1 on such virus producing cells. A major difference between HIV-1 cell-free single round infections and virus replication kinetics on T lymphocytes consists in the predominant role of cell-associated virus transmission rather than cell-free infection during multiple round virus replication. HIV-1 cell-to-cell transmission occurs across close cell contacts also referred to as virological synapse (VS) and involves polarization of the F-actin cytoskeleton, formation of F-actin rich membrane bridges as well as virus budding to cell-cell contacts. Since Nef potently interferes with triggered actin remodelling in several cell systems to reduce e.g. cell motility and signal transduction, we set out here to address whether Nef also affects organization and possibly function of the T lymphocyte VS. We find that in addition to increasing infectivity of cell-free virions, Nef can also moderately enhance single rounds of HIV-1 cell-cell transmission between Jurkat T lymphocytes. This occurs without affecting cell conjugation efficiencies or polarization of F-actin and HIV-1 p24Gag at the VS, identifying actin remodelling at the VS as an example of Nef-insensitive host cell actin rearrangements. However, Nef-mediated enhancement of single round cell-free infection or cell-to-cell transmission does not potentiate over multiple rounds of infection. These results suggest that Nef affects cell-free and cell-associated HIV-1 infection by the same mechanism acting on the intrinsic infectivity of HIV-1 particles. They further indicate that the high efficacy of cell-to-cell transmission can compensate such infectivity defects. Nef therefore selectively interferes with actin remodelling processes involved in antiviral host cell defense while actin driven processes that promote virus propagation remain unaltered.
Nef 是 HIV-1 发病机制的一个因素，通过不完全定义的机制提高病毒在体内的复制，从而导致艾滋病的进展。作为其生物学特性之一，Nef 增强了无细胞 HIV-1 颗粒在单次感染中的感染性，但它不能为 HIV-1 在产生病毒的细胞上提供显著和放大的生长优势。无细胞 HIV-1 单次感染与 T 淋巴细胞中的病毒复制动力学之间的一个主要区别在于，在多次病毒复制过程中，细胞相关病毒传播而不是无细胞感染起主要作用。HIV-1 细胞间传播发生在紧密的细胞接触中，也称为病毒学突触（VS），涉及 F-肌动蛋白细胞骨架的极化、富含 F-肌动蛋白的膜桥的形成以及病毒出芽到细胞-细胞接触。由于 Nef 强烈干扰几个细胞系统中触发的肌动蛋白重塑，以减少例如细胞迁移和信号转导，我们在这里着手研究 Nef 是否也影响 T 淋巴细胞 VS 的组织和可能的功能。我们发现，除了增加无细胞病毒粒子的感染力外，Nef 还可以适度增强 Jurkat T 淋巴细胞之间 HIV-1 的单次细胞间传播。这不会影响细胞连接效率或 VS 处 F-肌动蛋白和 HIV-1 p24Gag 的极化，将 VS 处的肌动蛋白重塑鉴定为 Nef 不敏感的宿主细胞肌动蛋白重排的一个例子。然而，Nef 介导的单次无细胞感染或细胞间传播的增强不会增强多次感染。这些结果表明，Nef 通过作用于 HIV-1 颗粒的固有感染力来影响无细胞和细胞相关的 HIV-1 感染。它们进一步表明，细胞间传播的高效性可以弥补这种感染力缺陷。Nef 因此选择性地干扰涉及抗病毒宿主细胞防御的肌动蛋白重塑过程，而促进病毒传播的肌动蛋白驱动过程则保持不变。
