Chinese National Influenza Center, State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Viral Disease Control and Prevention, China CDC, Xuanwu District Beijing, China.
Influenza Other Respir Viruses. 2009 Nov;3(6):287-95. doi: 10.1111/j.1750-2659.2009.00104.x.
Highly pathogenic H5N1 avian influenza viruses currently circulating in birds have caused hundreds of human infections, and pose a significant pandemic threat. Vaccines are a major component of the public health preparedness for this likely event. The rapid evolution of H5N1 viruses has resulted in the emergence of multiple clades with distinct antigenic characteristics that require clade-specific vaccines. A variant H5N1 virus termed clade 2.3.4 emerged in 2005 and has caused multiple fatal infections. Vaccine candidates that match the antigenic properties of variant viruses are necessary because inactivated influenza vaccines elicit strain-specific protection.
To address the need for a suitable seed for manufacturing a clade 2.3.4 vaccine, we developed a new H5N1 pre-pandemic candidate vaccine by reverse genetics and evaluated its safety and replication in vitro and in vivo.
A reassortant virus termed, Anhui/PR8, was produced by reverse genetics in compliance with WHO pandemic vaccine development guidelines and contains six genes from A/Puerto Rico/8/34 as well as the neuraminidase and hemagglutinin (HA) genomic segments from the A/Anhui/01/2005 virus. The multi-basic cleavage site of HA was removed to reduce virulence.
The reassortant Anhui/PR8 grows well in eggs and is avirulent to chicken and ferrets but retains the antigenicity of the parental A/Anhui/01/2005 virus.
These results indicate that the Anhui/PR8 reassortant lost a major virulent determinant and it is suitable for its use in vaccine manufacturing and as a reference vaccine virus against the H5N1 clade 2.3.4 viruses circulating in eastern China, Vietnam, Thailand, and Laos.
目前在禽类中流行的高致病性 H5N1 禽流感病毒已导致数百人感染，对人类构成了重大的大流行威胁。疫苗是对此类可能发生的事件进行公共卫生防范的重要组成部分。H5N1 病毒的快速进化导致了多个具有不同抗原特征的分支的出现，这些分支需要分支特异性疫苗。一种称为 2.3.4 分支的变异 H5N1 病毒于 2005 年出现，并已导致多次致命感染。需要与变异病毒的抗原特性相匹配的疫苗候选物，因为灭活流感疫苗可引发针对特定毒株的保护。
为满足生产 2.3.4 分支疫苗的适宜种子的需求，我们通过反向遗传学开发了一种新的 H5N1 大流行前疫苗候选物，并评估了其在体外和体内的安全性和复制能力。
按照世界卫生组织大流行疫苗开发指南，通过反向遗传学生产了一种名为 Anhui/PR8 的重组病毒，它包含六个来自 A/Puerto Rico/8/34 的基因以及来自 A/Anhui/01/2005 病毒的神经氨酸酶和血凝素（HA）基因组片段。HA 的多碱性裂解位点被删除以降低毒力。
重组 Anhui/PR8 在鸡蛋中生长良好，对鸡和雪貂均无毒性，但保留了亲本 A/Anhui/01/2005 病毒的抗原性。
这些结果表明，Anhui/PR8 重组病毒失去了一个主要的毒力决定因素，适合用于疫苗生产，并可作为针对在中国东部、越南、泰国和老挝流行的 H5N1 2.3.4 分支病毒的参考疫苗病毒。
