Discovering new host-pathogen interactions to develop antivirals and vaccine strategies against PRRSV

猪繁殖与呼吸综合征(PRRS)是猪的一种病毒性疾病，可造成重大经济损失。该病的病原体是PRRS病毒(PRRSV)，它是一种快速进化的、小的、被包裹的正义RNA病毒。事实证明，改装后的活疫苗在交叉保护方面往往无效，有些疫苗已被证明会导致传播感染。因此，PRRS仍然对动物的健康和福利产生重大影响，导致妊娠减少或失去，仔猪死亡，所有感染PRRSV的猪的生长速度下降。PRRSV是宿主免疫反应的主要调节器。该病毒感染先天免疫反应的细胞，特别是巨噬细胞和树突状细胞的某些亚群。在PRRSV感染后，细胞因子的分泌和天然宿主细胞的反应被病毒感染主动下调，导致天然免疫和获得性免疫反应的调节。I型干扰素反应受到多种非结构蛋白和结构蛋白的积极干扰，目前还远未完全了解[1]。PRRSV对免疫系统的干扰影响超出了PRRSV感染本身。由于缺乏免疫反应，与其他病原体的混合感染会增加。因此，重要的是要了解PRRSV是如何干扰宿主免疫系统的，并确定参与这一过程的病毒因素。这将为我们提供合理减毒PRRSV的工具，以产生更有效和更安全的疫苗。病毒是强制性的细胞内寄生虫，利用细胞机械入侵并操纵宿主复制病毒粒子。因此，了解病毒与宿主的相互作用对于设计抗病毒策略至关重要，例如抗病毒药物、疫苗、基因选择或基因组编辑目标。FDA批准的药物都针对细胞途径，因此是在原代巨噬细胞上用于识别感染期间PRRSV利用的宿主机制的理想起点。这些被确定为抗病毒的药物不仅可以进一步研究宿主和病原体的相互作用，而且这些药物和类似的化合物可能被开发用于抗病毒治疗。在这个项目中，我们的目标是识别与干扰素反应下调有关的病毒基因，并设计合理的疫苗减毒策略。我们还将研究干扰素诱导的鸟苷结合蛋白(GBP)家族已知的抗病毒基因的作用，最近发现该家族的多态在抵抗PRRSV感染方面发挥了作用(2)。将通过与Jason Mercer博士(MRC LMCB，伦敦)的实验室合作进行FDA批准的药物筛选，并对已鉴定的化合物进行跟踪，以确定它们在病毒复制周期中的作用，从而研究原始肺泡巨噬细胞中宿主与病原体的相互作用机制。这个为期4年的案例学习将在生物学的各个领域提供出色的培训，涵盖基因组学和遗传学、系统生物学、病毒学、细胞生物学、先天免疫学、生物化学和分子生物学的各个方面。成功的候选人将学习和应用各种技术，例如病毒学技术(滴定、纯化)、原代细胞和永生化细胞系的细胞培养、荧光激活细胞分选、Western blotting、荧光显微镜等等。参考文献1。孙勇，韩明，金C，卡尔弗特JG，Yoo D.2012。干扰素介导的天然免疫与猪繁殖与呼吸综合征病毒之间的相互作用。病毒4：424-446.2。首页--期刊细介绍--期刊题录与文摘--期刊详细文摘内容育苗猪对猪繁殖与呼吸综合征反应的宿主遗传学。兽医微生物学209：107-113。

Porcine Reproductive and Respiratory Syndrome (PRRS) is a viral disease of pigs leading to major economic losses. The causative agent of the disease is PRRS virus (PRRSV), a rapidly evolving, small, enveloped positive-sense RNA virus. Modified live vaccines often prove ineffective in cross-protection and some have been shown to cause spreading infections. Thus, PRRS still has major impacts on animal health and welfare, resulting in reduction or loss of pregnancies, death in young piglets, and decreased growth rates in all PRRSV infected pigs. PRRSV is a master modulator of the host immune response. The virus infects cells of the innate immune response, specifically certain subsets of macrophages and dendritic cells. Upon PRRSV infection cytokine secretion and the innate host cell response are actively downregulated by the viral infection resulting in modulation of both the innate and adaptive immune response. The type I interferon (IFN) response is actively interfered with by multiple non-structural and structural proteins and is far from being fully understood (1). The interference of PRRSV with the immune system has impacts beyond PRRSV infection itself. Co-infections with other pathogens are enhanced due to the lack of immune response. Therefore, it is important to understand how PRRSV interferes with the host immune system and to identify viral factors involved in this process. This will give us tools to rationally attenuate PRRSV to generate more effective and safer vaccines.Viruses are mandatory intracellular parasites and use the cellular machinery to invade and manipulate the host to replicate the virions. Therefore, understanding the virus-host interaction is crucial to devising antiviral strategies, such as antiviral drugs, vaccines, genetic selection, or genome editing targets. FDA-approved drugs all target cellular pathways and are therefore an ideal starting point to use on primary macrophage cells to identify host machinery exploited by PRRSV during infection. Not only will the drugs identified as being antiviral allow further investigation into the host-pathogen interaction but the drugs and similar compounds may be developed for use in antiviral treatment.In this project we aim to identify viral genes involved in the downregulation of the IFN response and devise rational attenuation strategies for vaccines. We will also investigate the role of known antiviral genes of the interferon-inducible guanylate-binding protein (GBP) family, polymorphisms in which recently were shown to play a role in resilience towards PRRSV infection (2). Host-pathogen interaction mechanisms in primary alveolar macrophage cells will be investigated by performing an FDA-approved drug screen in collaboration with the lab of Dr Jason Mercer (MRC LMCB, London) and identified compounds followed up to identify their role in the viral replication cycle. This 4-year CASE studentship will provide excellent training in a variety of fields of biology, covering aspects of genomics and genetics, systems biology, virology, cell biology, innate immunology, biochemistry, and molecular biology. The successful candidate will learn and apply a wide variety of techniques, e.g. virological techniques (titration, purification), cell culture of primary cells and immortalized cell lines, fluorescence-activated cell sorting, western blotting, fluorescence microscopy, and many more. References1. Sun Y, Han M, Kim C, Calvert JG, Yoo D. 2012. Interplay between interferon-mediated innate immunity and porcine reproductive and respiratory syndrome virus. Viruses 4:424-446.2. Dekkers J, Rowland RRR, Lunney JK, Plastow G. 2017. Host genetics of response to porcine reproductive and respiratory syndrome in nursery pigs. Veterinary microbiology 209:107-113.