Improving existing vaccine platforms to minimise the economic impact of emerging Bluetongue virus (BTV) serotypes

蓝舌病是由蓝舌病病毒（BTV）引起的家畜（主要是羊和牛）的一种主要传染病。BTV通过叮咬的蠓从受感染的动物传播到未受感染的动物。从历史上看，蓝舌病几乎只在世界上的温带和热带地区被描述，那里温暖的温度有利于易感昆虫媒介种群的传播，也有利于媒介内的病毒复制周期。然而，在过去的十年中，BTV在南欧广泛传播，并且出乎意料地在北方欧洲（包括英国）也广泛传播，远远超出其已知的地理上限，并对动物健康和经济造成严重问题。有趣的是，全世界有24种不同的BTV“类型”（称为“血清型”）。基本上，这些不同的血清型具有形成病毒颗粒外壳的略微不同的蛋白质。从本质上讲，蓝舌病可以被认为是由24种不同病毒引起的单一疾病！这是因为如果动物接种了针对BTV血清型1的疫苗，例如（BTV-1），那么它将仅针对BTV-1的感染而不是针对其他23种BTV血清型的感染而受到保护。自1998年以来，已有9种不同血清型的13种BTV入侵欧洲。安全有效的灭活疫苗的开发对预防和限制BTV流行产生了巨大的有益影响。然而，任何新血清型的显著侵入都迫使选择相关的新病毒用于疫苗生产。由于BTV是通过昆虫媒介传播的，因此它具有季节性模式。大多数蓝舌病疫情在传入后的第一个病媒季节传播有限，但在第二年将大幅传播并造成广泛损害。因此，疫苗生产的时间轴对于阻止新引入的血清型的传播是绝对关键的。目前，疫苗生产商从田间获得新的BTV毒株大约需要1至6个月，另外需要14至20个月来开发、测试和生产新疫苗。快速生产疫苗将确保遏制蓝舌病。例如，据估计，英国BTV-8疫情的控制为英国经济节省了4.85亿英镑和10，000个工作岗位。这一成功的疫苗接种活动使英国免于第二个BTV-8“季节”。然而，前一年没有BTV-8疫苗可以阻止该疾病在几个中欧国家的第二年爆发。该提案的总体目标是：（i）缩短将新引入的BTV血清型的适当疫苗推向市场所需的时间;（ii）收集确定（和优化）BTV疫苗制备中使用的毒株选择标准所需的数据;（iii）设计能够引发免疫应答的病毒，以保护免受多种BTV血清型的侵害。通过使用新的基因工程技术，我们将开发和表征BTV“合成”病毒，这些病毒可以作为疫苗开发的“现成”毒株。该系统有可能减少制造商从现场获得新菌株所需的时间。我们将研究这些合成病毒如何在组织培养中发挥作用，以及它们在接种疫苗的绵羊中诱导保护性免疫的能力。此外，我们将确定BTV疫苗的哪些部分在接种动物中诱导免疫应答，我们将尝试设计可用作疫苗的病毒，以保护动物免受多种血清型的侵害。该提案的完成提供了开发工具的可能性，以避免未来新引入的BTV血清型引起的大部分经济损失。

Bluetongue is a major infectious disease of livestock (sheep and cattle mainly) caused by a virus known as Bluetongue virus (BTV). BTV is transmitted from infected to uninfected animals by the biting midges. Historically, bluetongue has been described almost exclusively in temperate and tropical areas of the world where the warm temperatures favoured both the spread of the susceptible insect vector population and also the viral replication cycle within the vector. However, in the last decade BTV has spread extensively in Southern Europe and, unexpectedly, also in Northern Europe (including the United Kingdom) reaching well beyond its known geographical upper limits and causing serious problems to both animal health and the economy. Interestingly there are worldwide 24 different 'types' (known as 'serotypes') of BTV. Basically, these different serotypes possess slightly different proteins that form the outside shell of the viral particle. In essence bluetongue can be considered a single disease caused by 24 different viruses! This is because if an animal is vaccinated against serotype 1 of BTV for example(BTV-1), it will then be protected only against infection by BTV-1 but not against the other 23 BTV serotypes. Since 1998 there have been 13 BTV incursions into Europe of 9 different serotypes. The development of safe and effective inactivated vaccines has had an enormous beneficial impact in preventing and limiting the BTV epidemic. However, any significant incursion of a new serotype forces the selection of the relevant new virus for vaccine production. Because BTV is transmitted by an insect vector it has a seasonal pattern. Most bluetongue outbreaks will have a limited diffusion in the first vector season after introduction, but will spread considerably and cause extensive damage in the following year. Thus, the timeline of vaccine production can be absolutely critical to halting the spread of a newly introduced serotype. At present it takes approximately 1 to 6 months for a vaccine manufacturer to acquire a new BTV strain from the field and a further 14-20 months to develop, test and produce a new vaccine. Rapid production of vaccines will assure containment of bluetongue. For example, it has been estimated that the control of the BTV-8 outbreak in the UK saved the UK economy £ 485M and 10,000 jobs. That successful vaccination campaign saved the UK from its second BTV-8 'season'. However, the previous year there was no BTV-8 vaccine ready to halt the devastating outbreak of the disease in its second year in several Central European countries. The overarching objectives of this proposal are to: (i) reduce the time needed to bring to market an appropriate vaccine for a newly introduced BTV serotype; (ii) collect the data necessary to determine (and optimize) the criteria of strain selection used in BTV vaccine preparations; (iii) engineer viruses that elicit an immune response able to protect against multiple BTV serotypes. By using new genetic engineering techniques, we will develop and characterize BTV 'synthetic' viruses that can function as 'off-the-shelf' strains for vaccine development. This system has the potential to reduce the time required by manufacturers to obtain a new strain from the field. We will study how these synthetic viruses function in tissue culture and their ability to induce a protective immunity in vaccinated sheep. In addition we will determine which portions of the BTV vaccines induce an immune response in the vaccinated animal and we will attempt to engineer viruses that can be used as vaccines to protect the animals against multiple seroptypes. The completion of this proposal offers the possibility to develop the tools to avoid in the future most of the economical damages induced by newly introduced BTV serotypes.