Selection Versus Mutation: Reducing the Risk of Vaccine Reversion

选择与突变：降低疫苗回复的风险

• 批准号: BB/L003988/1
• 负责人: Paul Britton
• 金额: $ 43.17万
• 依托单位: The Pirbright Institute
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FL003988%2F1
• 关键词: Selection; Versus; Mutation; Reducing; Risk

Vaccination against numerous endemic pathogens is an essential component of the poultry industry. Without these vaccines chickens would succumb to infection at an early age reducing the productivity of the industry well below sustainable levels. IBV is an endemic virus that causes severe disease outbreaks in chickens worldwide. Effective and economically viable vaccines against IBV are available and mainly produced from pathogenic virus strains by passing in eggs approximately one hundred times. During these passages the virus accumulates multiple sequence variations from the original pathogenic sequence. This ultimately leads to attenuation of the virus and the production of a live attenuated vaccine. These vaccines have lost their ability to cause disease but still elicit a protective immune response in the chicken, thus protecting the bird from future infections. However, as these are live viruses the potential for to revert back to a pathogenic form is considerable considering the few sequence changes between wild and vaccine strains.Despite the importance of these vaccines to the poultry industry and the risk of reversion, the processes that occur and the selective forces that drive virus attenuation during egg passage are unknown. Importantly, the differential contribution of virus sequence mutation compared to the selection of minor variants already present in the virus population has not been determined. Understanding these basic processes is essential to the development of future vaccines to reduce the threat of reversion.This study will use passaged pathogenic IBV strains produced in the same way as vaccines. In parallel we will use a unique system that allows us to passage a single virus clone rather than a mixed virus population. Using contemporary deep sequencing technology we will study the molecular changes that occur at fine resolution during the attenuation process. This will for the first time reveal how a mixed population of virus changes during vaccine manufacture and the extent to which individual viruses can mutate. These results will then inform a series of studies that manipulates the forces that drive virus change. The first will use IBV strains that contain a protein from another strain that influences the immune response in the chicken, and the second will use viruses that mutate much faster than wild type viruses. By passaging and deep sequencing these viruses in the same way as the wild type viruses, we will understand how different forces drive virus sequence mutation. These recombinant passaged viruses will then be tested to determine if this process has led to attenuation and also if they maintain the potential to infect other chickens that are exposed to vaccinated birds. Ultimately this research will reveal how IBV is attenuated by egg passage and identify key regions of the genome that prevent the virus from causing disease but do not impair its potential as a vaccine. Moreover, we will further develop our understanding of how different pressures influence the attenuation process and potentially identify ways to improve the process of vaccine design by engineering attenuated viruses. By understanding and manipulating the processes that govern virus attenuation and vaccine production we aim to identify ways of reducing the danger of vaccine strains reverting and causing damaging disease outbreaks.

针对许多地方性病原体的疫苗接种是家禽业的重要组成部分。如果没有这些疫苗，鸡只会在幼年时感染，使该行业的生产力大大低于可持续水平。IBV是一种地方性病毒，在全世界范围内引起鸡的严重疾病爆发。针对IBV的有效且经济上可行的疫苗是可获得的，并且主要通过在蛋中传代约100次从致病性病毒株产生。在这些传代过程中，病毒积累了原始致病序列的多个序列变异。这最终导致病毒的减毒和减毒活疫苗的生产。这些疫苗已经失去了致病的能力，但仍能在鸡体内引发保护性免疫反应，从而保护鸡免受未来的感染。然而，由于这些病毒是活病毒，考虑到野生毒株和疫苗毒株之间很少的序列变化，回复到致病形式的可能性是相当大的。尽管这些疫苗对家禽业很重要，而且存在回复的风险，但在鸡蛋传代过程中发生的过程和驱动病毒减毒的选择性力量尚不清楚。重要的是，尚未确定病毒序列突变与选择病毒群体中已存在的微小变异相比的差异贡献。了解这些基本过程对未来疫苗的开发至关重要，以减少逆转的威胁。本研究将使用传代的致病性IBV毒株，以同样的方式生产疫苗。同时，我们将使用一个独特的系统，使我们能够通过一个单一的病毒克隆，而不是混合的病毒种群。使用当代深度测序技术，我们将研究在衰减过程中以精细分辨率发生的分子变化。这将首次揭示混合病毒种群在疫苗生产过程中的变化以及单个病毒的变异程度。这些结果将为一系列操纵驱动病毒变化的力量的研究提供信息。第一种方法将使用IBV毒株，该毒株含有来自另一种毒株的蛋白质，该蛋白质会影响鸡的免疫反应，第二种方法将使用比野生型病毒突变快得多的病毒。通过以与野生型病毒相同的方式对这些病毒进行传代和深度测序，我们将了解不同的力量如何驱动病毒序列突变。然后将对这些重组传代病毒进行检测，以确定该过程是否导致减毒，以及它们是否保持感染暴露于接种疫苗禽类的其他鸡的潜力。最终，这项研究将揭示IBV是如何通过鸡蛋传代来减毒的，并确定基因组的关键区域，这些区域可以防止病毒引起疾病，但不会损害其作为疫苗的潜力。此外，我们将进一步发展我们对不同压力如何影响减毒过程的理解，并可能通过工程化减毒病毒来确定改进疫苗设计过程的方法。通过理解和操纵控制病毒减毒和疫苗生产的过程，我们的目标是确定减少疫苗株回复和导致破坏性疾病爆发的危险的方法。

项目成果

Transient dominant selection for the modification and generation of recombinant infectious bronchitis coronaviruses.

• DOI: 10.1007/978-1-4939-2438-7_12
• 发表时间: 2015
• 期刊: Methods in molecular biology (Clifton, N.J.)
• 作者: Keep SM;Bickerton E;Britton P
• 通讯作者: Britton P

Partial purification of IBV and subsequent isolation of viral RNA for next-generation sequencing.

• DOI: 10.1007/978-1-4939-2438-7_11
• 发表时间: 2015
• 期刊: Methods in molecular biology (Clifton, N.J.)
• 作者: Keep SM;Bickerton E;Britton P
• 通讯作者: Britton P

Multiple novel non-canonically transcribed sub-genomic mRNAs produced by avian coronavirus infectious bronchitis virus.

• DOI: 10.1099/jgv.0.001474
• 发表时间: 2020-10
• 期刊: The Journal of general virology
• 作者: Keep S;Oade MS;Lidzbarski-Silvestre F;Bentley K;Stevenson-Leggett P;Freimanis GL;Tennakoon C;Sanderson N;Hammond JA;Jones RC;Britton P;Bickerton E
• 通讯作者: Bickerton E