Molecular Mechanism of IMD (NF-kB) Inhibition by Dengue Virus in the Mosquito Aedes Aegypti, and Implications for Transmission and Emergence

登革热病毒是引起人类疾病的最重要的蚊媒病毒。世界上几乎一半的人口面临登革热病毒感染的风险，主要是在热带低收入和中等收入国家。每年约有4亿人受到感染，其中约有1亿例严重流感样登革热病例和50万例更严重和可能致命的登革出血热病例。除了造成重大痛苦和生命损失及经济生产力外，登革热的主要影响是，在许多国家几乎每年都会发生的疫情期间，欠发达的卫生保健系统不堪重负，影响到常规和紧急医疗服务。目前没有治疗登革热的药物，唯一获得许可的疫苗并不完善，不建议在全球广泛使用。登革热病毒由蚊子传播，不能在人与人之间直接传播。当蚊子以感染者为食时，它也会感染登革热病毒。当蚊子叮咬另一个人时，病毒就会传播，导致第二个人被感染。因此，预防通过蚊子传播是减少全球疾病负担的有效途径。通常传播登革热病毒的蚊子是“黄热病蚊子”（拉丁名埃及伊蚊）。和人类一样，蚊子也有免疫系统，可以保护它们免受病毒性疾病的侵害。当黄热病蚊子被病毒感染时，它的免疫反应就会启动，但并不是免疫系统的所有分支都能对抗登革热病毒。我们发现这是因为登革热病毒主动阻断了免疫反应的某些部分。这笔拨款将研究登革热病毒如何从免疫系统的这些分支中逃脱，这是对任何蚊媒病毒的首次研究。最终，这将使我们能够开发加强蚊子免疫系统的方法，以阻止它们感染登革热病毒，这将减少传播并保护人们免受登革热疾病的侵害。我们的第一个目标是弄清楚登革热病毒是如何阻断蚊子的免疫反应的。登革热病毒感染蚊子时会产生10种蛋白质，我们预测其中一种蛋白质会破坏蚊子的免疫反应。我们将确定哪种蛋白质可以做到这一点，以及如何做到这一点。我们的第二个目标将从一个不同的角度来看待这个问题，即询问蚊子免疫反应的某些部分对对抗登革热感染有多重要。我们将通过观察当我们在蚊子细胞中培养缺乏这些部分免疫反应的病毒时会发生什么来做到这一点。前两个目标将使用取自蚊子的细胞进行研究，这些细胞很容易在实验室中使用，并且有助于发现登革热病毒如何躲避蚊子免疫系统的细节。然而，我们不能用这些细胞来研究传播。出于这个原因，这笔拨款的第三个也是最后一个目标是在实验室里用黄热病蚊子重复前两个目标的关键实验，以检查我们的结果是否与实际蚊子的情况有关。登革热病毒有四种不同的毒株，其中一些毒株的行为彼此非常不同，因此我们还将检查我们的结果是否可以外推到所有四种登革热毒株。总之，我们的实验将告诉我们登革热病毒如何阻断蚊子的免疫反应，以及逃避某些蚊子免疫反应的能力对登革热病毒的传播有多重要。今后，这些信息将使我们能够通过增强黄热病蚊子的免疫反应，更好地对抗登革热病毒，从而减少登革热的全球负担，以防止疾病传播。

Dengue virus is the most important mosquito-borne virus causing human disease. Almost half the world's population is at risk of dengue virus infection, mostly in tropical low and middle-income countries. Approximately 400 million people are infected each year, with about 100 million cases of the severe flu-like dengue fever and 500,000 cases of the more severe and potentially fatal dengue haemorrhagic fever. The major impact of dengue disease, on top of significant suffering and loss of life and economic productivity, is that underdeveloped healthcare systems are overwhelmed during the almost annual epidemics experienced by many countries, affecting routine and emergency medical care. There are no medicines to treat dengue and the only licensed vaccine is imperfect and not recommended for widespread global use.Dengue virus is transmitted by mosquitoes and cannot spread directly between humans. When a mosquito feeds on an infected person, it too becomes infected with dengue virus. The virus is passed on when the mosquito feeds on another person, causing that second person to become infected. Preventing transmission through the mosquito is therefore an effective way of reducing the global disease burden.The mosquito that usually transmits dengue virus is the 'yellow fever mosquito' (Latin name Aedes aegypti). Like humans, mosquitoes have an immune system that protects them against viral diseases. The immune response of the yellow fever mosquito springs into action when the insect is infected with viruses, but not all arms of the immune system are able to fight dengue virus. We discovered that this is because dengue virus actively blocks certain parts of the immune response. This grant will investigate how dengue virus escapes from these arms of the immune system, a first for any mosquito-borne virus. Ultimately, this will allow us to develop ways of strengthening the immune system of mosquitoes to stop them from being infected with dengue virus, which will reduce transmission and protect people from dengue disease.Our first goal is to work out how dengue virus blocks mosquito immune responses. Dengue virus makes ten proteins when it infects a mosquito, and we predict that one of these proteins disrupts mosquito immune responses. We will identify which protein can do this, and how. Our second goal will look at this question from a different angle by asking how important certain arms of the mosquito's immune response are for fighting dengue infection. We will do this by looking at what happens to the virus when we grow it in mosquito cells that lack these parts of the immune response. These first two goals will be researched using cells taken from mosquitoes, which are easy to work with in the lab and useful for finding out the fine details of how dengue virus hides from the mosquito immune system. However, we cannot use these cells to study transmission. For this reason, the third and final goal of this grant is to repeat key experiments from the first two goals in yellow fever mosquitoes in the laboratory to check that our results are relevant to what happens in an actual mosquito. There are four different strains of dengue virus, some of which behave very differently from one another, so we will also check whether our results can be extrapolated to all four dengue strains.Together, our experiments will tell us how dengue virus blocks mosquito immune responses, and how important the ability to escape certain mosquito immune responses is for the transmission of dengue virus. In the future, this information will allow us to reduce the global burden of dengue disease by making the yellow fever mosquito's immune response stronger and better able to fight dengue virus in order to prevent disease transmission.