Combating avian influenza through systematic analysis of antigenic drift, genetic variation, and development of novel diagnostic tools and vaccines

全球家禽业在增加具有成本效益的动物蛋白生产以应对粮食安全挑战方面显示出巨大的希望。家禽生产对发展中国家经济转型中的经济增长作出了重大贡献；它帮助实现了减轻贫穷和减少农村失业，特别是妇女失业的目标。然而，H5N1型高致病性禽流感（HPAI）的出现和传播，以及低致病性禽流感（LPAI）亚型在许多国家广泛流行，给商业家禽和后院家禽生产造成重大损失，威胁到该部门的可持续性。禽类中高致病性禽流感和低致病性禽流感亚型的快速遗传进化和潜在的重新组合仍然是大流行出现的可靠威胁。控制这些病毒对公共卫生和兽医基础设施提出了巨大挑战。干预规划需要准确和及时地发现病毒亚型，通常包括对有风险的禽群进行环状扑杀、限制流动和贸易以及开展疫苗接种运动。在贫穷国家，由于经济、生态和伦理原因，大规模扑杀已变得不切实际，因为这些病毒在广大地区和多种不同的禽类中流行。目前可用的诊断工具和疫苗的有效性和适宜性受到实验室能力不足、野生型传播病毒固有多样性以及疫苗递送机制不完善的限制。拟议的研究将利用下一代生物技术方法来获得新知识和改进控制战略，以尽量减少家禽业因流感造成的经济损失，并减轻出现大流行的风险。我们将研究越南和巴基斯坦不同的流感流行病学和生态学，以及两国家禽业工业化水平的差异，并深入了解影响禽流感可持续控制的不同途径。这些研究将促进我们对遗传和抗原多样性如何影响疫苗的保护功效和诊断技术的敏感性/特异性的理解。对鸡鸭保护性免疫诱导至关重要的抗原表位的精确测定将为设计更广泛有效的疫苗提供信息。这些具有广泛交叉反应性和保护性的AIV抗原将被整合到已证实的病毒疫苗载体中；我们将对鸭肠炎病毒（DEV）和火鸡疱疹病毒（HTV）进行基因改造，生产出能够分别保护鸭或鸡免受AIV、鸭鼠疫和马立克病感染的多价重组活疫苗。这些下一代疫苗将通过大规模疫苗接种战略（在蛋内）提供，并将容易区分受感染的禽类和接种疫苗的禽类（DIVA）。我们将开发新的快速诊断方法，以区分在畜栏旁感染家禽的主要AIV亚型。这些技术有可能改变控制策略，使农民能够在早期阶段识别受感染的鸡群，而且对高度流行的经济上重要疾病（鸭瘟和马立克病）的双重保护将促进疫苗的吸收。通过我们基于社区的研究站点，我们将探索农民对疾病干预的态度和看法，并评估新技术的影响。越南和巴基斯坦控制和管理AIV的知识和改进的定制工具将减少生产损失，并有助于预防人畜共患感染高风险的疫情。除了对农业社区的直接效益外，改进的控制措施还可能在国家和全球范围内为更广泛的社区提供大量间接的经济、公共卫生、环境和社会效益。

The global poultry industry has shown great promise for increased, cost-effective production of animal protein to meet food security challenges. Poultry production has contributed significantly to economic growth in transitioning the economies of developing nations; it has helped meet goals in poverty alleviation and reduction in rural unemployment, particularly amongst women. However, the emergence and spread of the highly pathogenic avian influenza (HPAI) H5N1, and the widespread endemic presence of low pathogenicity avian influenza (LPAI) subtypes in many countries has threatened the sustainability of the sector through incurring heavy losses in both commercial and backyard poultry production. The rapid genetic evolution and potential reassortment of HPAI and LPAI subtypes in birds remains a credible threat for pandemic emergence. Control of these viruses presents formidable challenges to public health and veterinary infrastructures. Intervention programs require accurate and timely detection of virus subtypes, and typically involve ring culling of at-risk flocks, movement and trade restrictions, and vaccination campaigns. In poor countries, large scale culling has become impractical for economic, ecological and ethical reasons, since the viruses are endemic over wide regions and in multiple diverse avian species. The effectiveness and suitability of currently available diagnostic tools and vaccines is limited by insufficient laboratory capacity, the inherent diversity of wild type circulating viruses, and inadequate vaccine delivery mechanisms. The proposed research will exploit next generation biotechnological approaches to gain new knowledge and improve control strategies to minimize economic losses due to influenza within the poultry sector, and to mitigate the risk of pandemic emergence. We will examine the different epidemiology and ecology of influenza in Vietnam and Pakistan, in relationship to differing levels of industrialization of their poultry sectors, and to provide insight into the different pathways that impact on sustainable control of AIV. These studies will advance our understanding of how genetic and antigenic diversity influences the protective efficacy of vaccines and the sensitivity/specificity of diagnostic technologies. The precise determination of antigenic epitopes critical for induction of protective immunity in chickens and ducks will inform the design of more broadly effective vaccines. These broadly cross-reactive and protective AIV antigens will be integrated into proven viral vaccine vectors; we will engineer duck enteritis virus (DEV) and the herpesvirus of turkeys (HTV) to produce multivalent recombinant live vaccines capable of protecting ducks or chickens against AIV, as well as duck plague and Marek's disease, respectively. These next generation vaccines be delivered through mass vaccination strategies (in ovo) and will allow easy differentiation of infected from vaccinated birds (DIVA). We will develop novel rapid diagnostics to differentiate major AIV subtypes infecting poultry at the pen-side. These technologies have the potential to transform control strategies by empowering farmers to identify infected flocks at an early stage, and the dual protection against highly prevalent economically important diseases (duck plague and Marek's disease) will motivate uptake of the vaccine. Through our community-based study sites, we will explore farmer attitudes and perceptions regarding disease interventions, and assess the impact of novel technologies. The knowledge and improved tailored-made tools for control and management of AIV in Vietnam and Pakistan will reduce production losses and help prevent outbreaks with a high risk of zoonotic infections. In addition to direct benefits to farming communities, the improved control measures may offer substantial indirect economic, public health, environmental and social benefits to wider communities on both the national and global scale.