Transcriptional suppression of antiviral immune responses by HIV-1 Vpu

人类免疫缺陷病毒1型(HIV-1)是获得性免疫缺陷综合征(艾滋病)的病原体，全世界已有7000多万人感染。虽然人类具有各种固有的、先天的和适应性的抗病毒免疫反应，但HIV-1已经进化出复杂的逃避策略。其中许多策略涉及病毒辅助蛋白VPU、Nef、Vif和Vpr，它们干扰宿主因素，以确保病毒在体内有效复制。虽然直接的拮抗机制已经被详细研究，但对转录调控的了解相对较少，尽管后者可能对免疫激活产生全局影响。由于慢性免疫激活是HIV感染者疾病进展的重要驱动因素，更好地了解病毒因子如何调节宿主细胞转录不仅将增加我们对艾滋病进展决定因素的了解，而且最终还可能导致确定新的治疗和预防靶点。拟议的项目侧重于病毒蛋白VPU对免疫激活的调节。VPU被证明有效地阻断了转录因子NF-κB的激活，该转录因子是先天性和获得性免疫反应的关键调节因子。因此，我假设VPU是一种有效的抗病毒免疫反应的转录抑制因子。值得注意的是，核因子-κB的激活水平也决定了HIV-1基因的表达，因此在病毒潜伏和重新激活方面发挥了重要作用。因此，我想通过结合不同的前沿系统生物学方法来研究NF-κB中和作用对免疫激活和病毒复制的影响。首先，我将对感染了HIV-1初级分离株的初级CD4+T细胞进行下一代RNA测序，以破译HIV-1 VPU对细胞基因表达的影响，特别是涉及抗病毒免疫信号的基因。其次，我将使用两种创新的蛋白质组学方法来确定VPU对蛋白质泛素化和降解的整体影响，以确定VPU靶向的新的细胞因子，并阐明VPU介导的抑制NF-κB的机制。最后，将验证已识别的HITS，并测试它们与免疫激活、转录调节和病毒复制的相关性。这项研究的结果不仅将为决定免疫激活从而进展为艾滋病的因素提供重要的见解，而且还可能推动当前的治疗方法，即以NF-κB为靶点，重新激活并从潜伏的宿主中消除艾滋病毒-1。综上所述，这项建议旨在描述HIV-1抑制抗病毒免疫反应的独特途径。

The Human immunodeficiency virus 1 (HIV-1) is the causative agent of the acquired immunodeficiency syndrome (AIDS) and has infected more than 70 million people worldwide. Although humans are equipped with a variety of intrinsic, innate, and adaptive antiviral immune responses, HIV-1 has evolved sophisticated evasion strategies. Many of these strategies involve the viral accessory proteins Vpu, Nef, Vif and Vpr, which interfere with host factors to ensure efficient viral replication in vivo. While direct counteraction mechanisms have been investigated in detail, relatively little is known about transcriptional regulation, despite the fact that the latter may exert global effects on immune activation. As chronic immune activation is an important driver of disease progression in HIV infected individuals, a better understanding of how viral factors modulate host cell transcription will not only increase our understanding of the determinants of AIDS progression, but may ultimately also result in the identification of novel targets for therapy and prevention. The proposed projects focuses on the modulation of immune activation by the viral protein Vpu. Vpu was shown to efficiently block activation of the transcription factor NF-κB, a key regulator of innate and adaptive immune responses. I therefore hypothesize that Vpu is a potent transcriptional suppressor of antiviral immune responses. Notably, NF-κB activation levels also determine expression of HIV-1 genes and thus play an important role in viral latency and reactivation. I would therefore like to investigate the impact of NF-κB counteraction on immune activation and viral replication by combining different leading-edge systems biology approaches. First, I will perform next generation RNA-sequencing of primary CD4+ T cells infected with primary HIV-1 isolates to decipher the effects of HIV-1 Vpu on cellular gene expression, with a specific focus on genes involved in antiviral immune signaling. Second, I will use two innovative proteomics approaches to determine the global effects of Vpu on protein ubiquitination and degradation in order to identify novel cellular factors that are targeted by Vpu and elucidate the mechanisms underlying Vpu-mediated inhibition of NF-κB. Eventually, the identified hits will be validated and their relevance for immune activation, transcriptional regulation and viral replication will be tested. The results of this study will not only provide important insights into the factors determining immune activation and thus progression to AIDS, but may also advance current therapeutic approaches, in which NF-κB is targeted to reactivate and eliminate HIV-1 from latent reservoirs. In summary, this proposal aims at characterizing a unique pathway by which HIV-1 suppresses the antiviral immune response.