Host and Viral Determinants of Interferon Resistance During HIV-1 Transmission

上下文为了维持自身，所有病毒都必须传播到新的宿主。因此，干预病毒生命周期这一阶段的策略可能对人类健康、福祉和生产力产生巨大影响。疫苗接种、基本卫生、无菌医疗设备和血液制品筛查等干预措施非常有益，因为它们可以完全预防感染（而不是治疗已经感染的患者）。因此，我们迫切需要提高对病毒传播的认识，因为这一知识将成为未来病毒感染预防战略的基础。尽管有能力的人可以获得有效的HIV-1治疗，但全世界每年有200多万人新感染HIV-1。感染者每毫升血液中可能含有超过100万个HIV-1病毒颗粒。但是，即使病毒载量很高，大多数新的HIV-1感染都源于单一病毒颗粒的感染。人们对了解这些特殊颗粒成功传播的确切原因非常感兴趣，因为专门阻断这些颗粒传播的干预措施可以防止终身感染。干扰素是对入侵病原体的早期防御，可以发出感染信号并警告细胞提高其抗病毒防御水平。由于这些防御在对干扰素的反应中增加，因此它们被称为干扰素刺激基因（ISG）。由于ISG造成的恶劣环境，大多数病毒（包括HIV-1）在干扰素存在下的复制能力较低。然而，与一般的HIV-1变体不同，传播的HIV-1颗粒对干扰素介导的抑制作用的抵抗力要大得多。这一观察结果支持了这样的观点，即宿主干扰素应答是HIV-1传播的实质性障碍，因此干扰素抗性的HIV-1变体更有可能成功传播。目标。关于哪些ISG限制HIV-1传播以及传播的HIV-1如何避免这种抑制，我们知之甚少。我们的总体目标是阐明HIV-1生命周期这一重要而脆弱阶段的分子细节。我们将通过确定：（i）传播HIV-1克服的宿主因素，以及（ii）使传播的HIV-1抵抗干扰素抑制的机制细节。为了定位HIV-1传播颗粒中干扰素抗性的决定因素，我们将制备由干扰素敏感和干扰素抗性HIV-1病毒组成的杂交病毒，以定位HIV-1中赋予干扰素抗性的特定区域。我们还将在干扰素存在的情况下培养干扰素敏感的HIV-1，以了解病毒如何适应这种抑制。然后，我们可以检查HIV-1序列数据（来自感染患者）中任何已识别的耐药基序，以确定这些基序是否可能影响HIV-1的传播。为了确定被传播的HIV-1抵抗的宿主因素，我们将进行筛选，以系统地测量数百个个体ISG抑制HIV-1的能力。至关重要的是，我们将比较传播的干扰素耐药HIV-1病毒变异体与干扰素抑制HIV-1变异体，以确定传播的HIV-1特异性抵抗的ISG。在这个奖项的时间范围内，我们计划照亮HIV-1生物学的一个令人兴奋的领域，并刺激进一步的研究。从长远来看，我们的研究定义了HIV-1传播的分子细节，应该有助于设计针对HIV-1传播的新型预防/干预策略（如疫苗）。此外，由于可持续传播是大流行性病毒的一个基本方面，我们的工作将提供关于HIV-1传播的见解，这将提高我们评估其他新出现的病毒病原体大流行潜力的能力。

Context. To sustain themselves, all viruses must be transmitted to a new host. Accordingly, strategies interfering with this stage of the viral lifecycle can have an enormous impact on human health, wellbeing and productivity. Interventions such as vaccination, basic hygiene, sterile medical devices and the screening of blood products have been hugely beneficial because they can prevent infection altogether (rather than treating an already infected patient). Thus, there is an urgent need to improve our understanding of virus transmission as this knowledge will underpin future strategies of viral infection prevention.Although effective HIV-1 treatments are available for those who can afford them, more than 2 million people become newly infected with HIV-1 every year worldwide. Infected patients can have more than a million HIV-1 virus particles in a single ml of blood. But even as viral loads can be high, the majority of new HIV-1 infections originate from infection by a single virus particle. There is great interest in understanding exactly why these particular particles are successfully transmitted, as interventions that specifically block transmission of these particles could prevent lifelong infection.Interferons are an early defence against invading pathogens that can signal infection and alert cells to increase the levels of their antiviral defences. Because these defences are increased in response to interferons, they are known as interferon-stimulated genes (ISGs). As a result of the hostile environment created by ISGs, most viruses (including HIV-1) are less able to replicate in the presence of interferons. However, unlike the average HIV-1 variant, the transmitted HIV-1 particles are far more resistant to interferon-mediated inhibition. This observation underpins the idea that host interferon responses are a substantial barrier to HIV-1 transmission, such that an HIV-1 variant that is interferon resistant is more likely to be successfully transmitted. Aims. Very little is known about which ISGs constrain HIV-1 transmission and how transmitted HIV-1 avoids this inhibition. Our overall aim is to illuminate the molecular details of this important and vulnerable stage of the HIV-1 lifecycle. We will do this by identifying: (i) the host factors that transmitted HIV-1 overcomes, and (ii) the mechanistic details that enable transmitted HIV-1 to resist interferon inhibition. To map the determinants of interferon resistance in transmitted HIV-1 particles, we will make hybrid viruses comprised of interferon sensitive and interferon resistant HIV-1 viruses, in order to locate the specific region(s) of HIV-1 that confer interferon resistance. We will also grow interferon sensitive HIV-1 in the presence of interferons, in order to learn how the virus adapts to this inhibition. We can then examine any identified resistance motifs in HIV-1 sequence data (from infected patients) to determine whether these motifs might influence HIV-1 transmission. To identify the host factors resisted by transmitted HIV-1 we will carry out screens to systematically measure the ability of hundreds of individual ISGs to inhibit HIV-1. Crucially, we will compare transmitted interferon resistant HIV-1 virus variants to interferon inhibited HIV-1 variants to identify ISGs that are specifically resisted by transmitted HIV-1.Applications and benefits. During the timeframe of this award we plan to illuminate an exciting area of HIV-1 biology and stimulate further research. In the longer term, our research defining the molecular details of HIV-1 transmission should aid the design of novel prevention/intervention strategies (such as vaccines) designed to target transmitted HIV-1. Furthermore, because sustainable transmission is an essential facet of pandemic viruses, the insight our work will provide on transmission of HIV-1 should improve our ability to assess the pandemic potential of other emerging viral pathogens.