Vaccines and molecular tools for the control of the emerging bunyavirus, severe fever with thrombocytopenia syndrome phlebovirus (SFTSV)

新形成的布尼亚病毒目病毒通常是节肢动物传播的，其中许多成员能够引起人类、动物和疾病。世卫组织已经确定了几种布尼亚病毒作为关键的新出现病原体，而这一题为“加速疫苗开发的一种卫生方法”的呼吁也强调了对这类病毒的兴趣。该项目重点关注布尼亚病毒中发热病毒科的发热伴血小板减少综合征静脉病毒（SFTS静脉病毒；SFTSV），该病毒还包括亚洲和美国的重要新发病原体（心脏地带病毒，HRTV）。迄今为止，中国报告了2500多例SFTSV病例，韩国报告了172例，日本报告了96例，病死率从8.2%到32.6%不等。在所有流行国家，报告的年发病率都在增加，例如在中国，2010年报告了53例，而2013年为676例。为了应对新出现的布尼亚病毒构成的威胁，mrc -格拉斯哥大学病毒研究中心（CVR）的科学家开发了一种“反向遗传学”系统，可以利用该系统操纵SFTSV，并允许合理设计合理减毒的候选病毒疫苗。这种反向遗传系统能够从编码病毒基因组RNA cDNA拷贝的质粒中快速恢复具有复制能力的布尼亚病毒。这项技术有助于绘制体液和细胞免疫应答的表位，以及识别和操纵病毒编码的毒力因子。许多布尼亚病毒的NSs蛋白被认为是毒力因子，因为它们具有抵抗哺乳动物先天免疫反应的能力。因此，这些基于反向遗传学的策略为开发新出现的布尼亚病毒疾病的合理候选疫苗提供了一种现实的手段，同时也为开发有助于进一步阐明感染和病毒发病机制的免疫反应的病毒提供了一种现实的手段。我们现在已经产生了一种重组nss缺失的SFTSV（称为SFTSVdelNSs），它不能对抗感染后产生的I型干扰素反应。这有助于研究先天免疫反应在控制SFTSV中的作用，以及在缺乏毒力因子NSs的情况下的体内组织趋向性和发病机制，从而评估这些潜在的减毒病毒作为候选疫苗。基于反向遗传学方法生产重组布尼亚病毒的优势超出了生产减毒病毒候选疫苗的范围。该系统还允许开发和生产病毒样颗粒（vlp）。可以测试重组病毒和VLPs在免疫动物和保护性候选疫苗中诱导免疫反应的能力。本项目将联合北京生命科学研究院（BIOLS）的研究人员，阐明SFTSV感染的宿主免疫应答和发病机制，开发重组病毒候选疫苗和工具，以进一步研究SFTSV。目的1。目的：阐明SFTSV NSs在体内组织趋向性和发病机制中的作用。我们还将评估重组SFTSV（缺乏NSs； SFTSVdelNSs）作为候选疫苗与VLPs的比较。目标2。生产新的SFTSV中和抗体，用于基础研究和潜在的治疗药物。我们将使用一种表达报告基因的新型SFTS病毒来研究抗体反应，以研究患者血清和感染动物的免疫反应。这将使我们能够确定中和抗体反应的广度，并绘制病毒粒子上的抗原决定因子。SFTSV Gn结构蛋白（抗体应答的已知靶标）的抗原变异和逃逸将通过突变分析进行研究。该项目还将包括为合作伙伴BIOLS提供反向遗传学技术培训。

Viruses in the newly formed order Bunyavirales are frequently arthropod-transmitted with many members capable of causing substantial human, animal and disease. The WHO has identified several bunyaviruses as key emerging pathogens, and this call entitled "One health approaches to accelerate vaccine development" also emphasizes interest in this group of viruses. This project focuses on severe fever with thrombocytopenia syndrome phlebovirus (SFTS phlebovirus; SFTSV) of the Phenuiviridae family of bunyaviruses which also includes significant emerging pathogens in both Asia and the USA (Heartland virus, HRTV). To date, over 2500 SFTSV cases have been reported in China, 172 cases in South Korea and 96 cases in Japan, with case fatality rates ranging from 8.2% to 32.6%. The annual incidence of reporting is increasing in all endemic countries, e.g. in China where 53 cases were reported in 2010, compared to 676 in 2013. To address the threat posed by novel, emerging bunyaviruses, scientists at the MRC-University of Glasgow Centre for Virus Research (CVR) have developed a "reverse genetics" system with which SFTSV can be manipulated, and which permit the rational design of rationally attenuated virus vaccine candidates. Such reverse genetics systems enable the rapid recovery of replication competent bunyaviruses from plasmids encoding cDNA copies of the viral genomic RNA. This technology facilitates the mapping of epitopes targeted by the humoral and cellular immune response as well as the identification and manipulation of virally-encoded virulence factors. The NSs proteins of many bunyaviruses are recognised as virulence factors due to their ability to counteract the mammalian innate immune responses. Hence, these reverse genetics-based strategies offer a realistic means to develop rational vaccine candidates for emerging bunyaviral diseases, as well as the development of viruses that help to further elucidate the immune responses mounted to infection and viral pathogenesis. We have now generated a recombinant NSs-deletant SFTSV (called SFTSVdelNSs) which is unable to antagonise type I interferon responses mounted in response to infection. This facilitates the studies into the role of innate immune responses in controlling SFTSV, as well as in vivo tissue tropism and pathogenesis in absence of the virulence factor NSs, leading to the evaluation of such potentially attenuated viruses as vaccine candidates. The strengths of reverse genetics-based approaches to producing recombinant bunyaviruses extends beyond the production of attenuated virus vaccine candidates. The system also allows the development and production of virus-like particles (VLPs). Both recombinant viruses and VLPs can be tested for their ability to induce immune responses in immunised animals as well as protective vaccine candidates. This proposal will bring together CVR and Beijing Institutes of Life Science (BIOLS) researchers to elucidate host immune responses to SFTSV infection and pathogenesis, the development of recombinant virus vaccine candidates and tools to further study SFTSV.Aim 1. To elucidate the contribution of SFTSV NSs to in vivo tissue tropism and pathogenesis. We will also assess a recombinant SFTSV (lacking NSs; SFTSVdelNSs) as vaccine candidate in comparison to VLPs.Aim 2. To produce novel neutralising antibodies against SFTSV for basic research and as potential therapeutic agents. We will investigate antibody responses using a novel SFTS viruses expressing reporter genes to study immune responses in both patient sera and infected animals. This will allow us to define the breadth of the neutralising antibody responses and to map antigenic determinants on the virion. Antigenic variation and escape from neutralisation of the SFTSV Gn structural protein (known target for antibody responses) will be investigated through mutational analysis. The project will also include training in reverse genetics technology for the partner BIOLS.