Application of next generation phage display technology to development of a Differentiation of Infected from Vaccinated Animals (DIVA) strategy

迄今为止影响牲畜的外来或未知的病毒性疾病的入侵近年来似乎越来越频繁。气候变化和日益加剧的全球化被认为是促成因素；因此，这一趋势似乎将继续下去。最近的例子是施马伦贝格病毒的出现，这种病毒会导致牛羊出生缺陷和流产。诊断测试，包括测量病毒抗体的测定，得到了迅速发展，一种全病毒灭活疫苗在相对较短的时间内获得了紧急许可证。然而，施马伦贝格病毒造成的经济损失是巨大的，特别是由于没有这种疾病的国家对来自受影响地区的动物（及其产品，如精液）实行贸易限制。区分受感染动物与接种疫苗动物（DIVA）策略是指一种方法，其中诊断分析检测自然感染动物中存在的抗体，而在接种疫苗的动物中不存在抗体。这样的试验证明，即使动物接种了预防疾病的疫苗，它们也不会受到感染。就某些病毒性疾病而言，缺乏这种战略可能意味着国际贸易限制和捕杀动物被视为控制疫情的最佳选择。很难区分针对灭活全病毒疫苗产生的抗体，因为在感染中产生抗体反应的所有相同结构的病毒成分都存在。然而，我们假设在疫苗制备过程中用于灭活病毒的化学处理将改变病毒蛋白的结构并导致抗体库的微妙变化。下一代噬菌体展示（NGPD）是一项强大的新兴技术，我们建议以一种新颖的方式应用于识别任何代表线性表位或病毒蛋白构象表位的半模位的区域，这些区域的差异足以使自然感染奶牛的抗体与接种奶牛的抗体区分开来。这些肽可以应用于DIVA测试。施马伦伯格病毒被选为“原理证明”。如果成功，该方法可以应用于现在或将来对英国牲畜构成威胁的其他新出现的病毒，允许快速反应，不仅包括灭活疫苗，还包括附带的DIVA测试，从而提供全面的控制策略，而不需要任何相关产品出口限制。

Incursions of hitherto exotic or unknown viral diseases affecting livestock animals appear to have been increasing in frequency in recent years. Climate change and increasing globalisation are thought to be contributing factors; therefore it seems likely that this trend will continue. The most recent example was the emergence of Schmallenberg virus, which causes birth defects and abortions in cattle and sheep. Diagnostic tests, including assays to measure antibodies against the virus, were rapidly developed and an inactivated whole virus vaccine was granted an emergency license in a relatively short time-frame. However, economic losses as a result of Schmallenberg virus have been substantial, particularly as a result of countries that have remained free of the disease imposing trade restrictions on animals (and products from them such as semen) from affected regions. A differentiation of infected from vaccinated animals (DIVA) strategy refers to an approach in which a diagnostic assay detects antibodies that are present in naturally-infected animals but not in animals that have been vaccinated. Such a test allows demonstration that animals are free of infection even if they have been vaccinated to protect them from disease. In the case of some virus diseases, the lack of such a strategy can mean that international trade restrictions and killing animals are seen as the best option for controlling an outbreak. It is difficult to distinguish between antibodies raised to an inactivated whole virus vaccine because all of the same structural virus components that generate an antibody response in infection are present. However, we hypothesise that the chemical treatments used to inactivate the virus in the preparation of vaccines will modify the structure of viral proteins and lead to subtle changes in the antibody repertoire. Next generation phage display (NGPD) is a powerful emerging technology that we propose to apply in a novel way to identify any regions that represent linear epitopes or mimotopes of conformational epitopes of the virus proteins that differ sufficiently to allow antibodies from naturally-infected cows to be distinguished from those from vaccinated cows. These peptides could then be applied in a DIVA test. Schmallenberg virus has been chosen to provide 'proof-of-principle'. If successful, the approach could be applied to other emerging viruses that pose a threat to UK livestock now or in the future allowing a rapid response to include not only an inactivated vaccine but an accompanying DIVA test thereby providing a comprehensive control strategy without any associated product export restrictions.