The typhoid toxin of Salmonella Typhi - a new disease mechanism and a strategy for combatting drug-resistant typhoid and chronic carriage in humans

抗菌素耐药性(AMR)是社会面临的一个决定性问题。这是由伤寒沙门氏菌的AMR谱系引起的伤寒流行的缩影，每年有2100万例伤寒病例和16.8万人死亡。例如，在马拉维，2010年前只有7%的伤寒病例对多种药物产生抗药性。到2015年，97%的伤寒病例抵抗多种药物治疗。因此，领导抗击伤寒沙门氏菌的全球性组织，如伤寒疫苗加速联盟(TyVAC)，旨在根除伤寒。然而，还有第二个问题：伤寒沙门氏菌也会在没有明显临床症状的情况下引起人类的慢性感染。这些所谓的“慢性携带者”会在人群中保留并传播伤寒沙门氏菌。我们对慢性携带伤寒知之甚少，这阻碍了全球根除伤寒的努力。为了对抗伤寒和制定根除病原体的策略，我们必须解决导致伤寒和慢性携带的决定性机制。值得注意的是，伤寒和慢性携带的致命症状是通过一种名为伤寒毒素的单一伤寒毒力因子促进的，它会对我们细胞中的DNA造成损害，并激活细胞DNA损伤反应(DDR)。这种毒素是如何操纵DDR的，以及这是如何介导伤寒和慢性携带的，目前还不清楚。我的实验室有两个重大发现，有可能解开毒素的机制，并为抗击伤寒和慢性携带提供一种新的方法。我们发现：(I)这种毒素通过触发人类细胞的衰老来驱动感染。衰老的细胞释放的因子会诱导邻近细胞的衰老，在整个种群中产生多米诺骨牌效应。令我们惊讶的是，衰老的细胞对沙门氏菌细胞内感染的敏感性增加，这揭示了毒素诱导细胞衰老驱动感染的新作用。(Ii)毒素通过细菌基因毒素(环)诱导的独特的DDR反应诱导衰老。环型意味着一种新的毒力机制，由毒素诱导的DNA复制位点的破坏驱动，DNA复制是细胞分裂的基础。新颖性和重要性是显而易见的。如果该毒素促进伤寒症状和通过DDR的慢性携带，那么我们需要(I)解决支撑环状表型的DNA损伤机制，以及(Ii)了解衰老如何促进细胞和动物模型中的沙门氏菌感染(四年计划的目标)。通过实现四年规划目标，我将揭示对毒素机制至关重要的细胞因子的身份，并揭示潜在的生物标志物，这些生物标志物将帮助我通过我的七年规划解决伤寒和人类慢性携带的问题。这将通过研究人类体内的毒素机制来实现，使用临床样本来揭示有助于诊断和疾病监测的潜在生物标记物，并通过筛选新的治疗方法来抵消伤寒和慢性携带的毒素。为了最大限度地提高项目影响和我的领导潜力，我设计了一个研究员发展计划，该计划与研究目标相结合，并朝着7年计划的翻译目标迈进。发展计划包括：(I)在美国的伤寒临床试验和根除计划方面的经验；(Ii)在越南对伤寒沙门氏菌的实地研究；(Iii)在英国领导以伤寒为重点的研究会议；(Iv)探讨伤寒的公众参与经验；以及(V)与该领域的现有领导者接触，他们就有关伤寒的政策向英国政府和世界卫生组织提供建议。建议的UKRI FLF旨在通过揭示伤寒毒素如何导致伤寒和慢性病，为全球抗击伤寒沙门氏菌的努力做出贡献。它有可能通过影响伤寒控制战略和根除方案来改善人类健康

Antimicrobial resistance (AMR) is a defining problem facing society. This is epitomised by epidemics of typhoid fever caused by AMR lineages of the bacterial pathogen Salmonella Typhi that underlies 21 million typhoid cases and 168,000 deaths each year. For example, in Malawi, only 7% of typhoid cases were resistant to multiple drugs before 2010. By 2015, 97% of typhoid cases resisted multi-drug treatments. Thus, global organisations who lead the fight against S.Typhi, such as the Typhoid Vaccine Acceleration Consortium (TyVAC), aim to eradicate typhoid. However, there's a second problem: S.Typhi also causes chronic infections in humans without obvious clinical symptoms. These so-called 'chronic carriers' retain and transmit S.Typhi in the population. We know remarkably little about chronic carriage, which impedes global efforts to eradicate typhoid. To combat S.Typhi and develop pathogen eradication strategies, we must resolve the decisive mechanisms responsible for typhoid fever and chronic carriage.Remarkably, the mortal symptoms of typhoid and chronic carriage are facilitated through a single S.Typhi virulence factor called the typhoid toxin, which causes damage to DNA in our cells and activates the cellular DNA damage response (DDR). How the toxin manipulates the DDR and how this mediates typhoid fever and chronic carriage is not understood.My laboratory has made two major discoveries that have the potential to unlock the toxin mechanism and provide a new way to combat typhoid fever and chronic carriage. We discovered that:(i) The toxin drives infections by triggering senescence in human cells. The senescent cells released factors that induced senescence in neighbouring cells creating a domino-like effect throughout the population. To our surprise, the senescent cells have increased susceptibility to intracellular Salmonella infections, which reveals a new role for the toxin - inducing cellular senescence to drive infection.(ii) The toxin induces senescence via a unique DDR Response Induced by a bacterial Genotoxin (RING). The RING phenotype signifies a new virulence mechanism driven by toxin-induced damage at sites of DNA replication, which underpins cell division. The novelty and importance are clear. If the toxin facilitates typhoid fever symptoms and chronic carriage through the DDR, then we need to (i) resolve the DNA damage mechanisms underpinning the RING phenotype, and (ii) understand how senescence facilitates Salmonella infections in cells and animal models (Aims of the 4-year plan). By achieving the 4-year plan objectives, I will unveil the identity of cellular factors that are crucial to the toxin mechanism and reveal potential biomarkers that will help me address the problem of typhoid and chronic carriage in humans via my 7-year plan. This will be achieved by investigating the toxin mechanism in humans using clinical samples to reveal potential biomarkers that will help diagnosis and disease surveillance, and by screening for novel therapeutics, which counteract the toxin underlying typhoid and chronic carriage.To maximise project impact and my leadership potential, I have designed a Fellow Development Plan that integrates with the research aims and builds towards the translational goals of the 7-year plan. The Development Plan includes: (i) experience in typhoid clinical trials and eradication programmes with TyVAC in the USA, (ii) field research on AMR S.Typhi in Vietnam, (iii) leading a typhoid-focussed research meeting in the UK, (iv) 'Take on Typhoid' public engagement experience, and (v) engaging with current leaders in the field who advise the UK government and the World Health Organisation on policy regarding typhoid.The proposed UKRI FLF aims to contribute to global efforts against AMR S.Typhi by revealing how the toxin drives typhoid and chronic disease, which has the potential to improve human health by impacting typhoid control strategies and eradication programmes