Research and Development Section, Deltamune Pty. Ltd., Lyttelton, South Africa.
Zoetis Inc., Kalamazoo, MI, USA.
Avian Pathol. 2023 Jun;52(3):176-184. doi: 10.1080/03079457.2023.2181145. Epub 2023 May 2.
Highly pathogenic avian influenza (HPAI) viruses from the Goose/Guangdong/96-lineage emerged in Southeast Asia and subsequently spread to the Middle East, Africa and Europe, infecting a range of birds and mammals (including humans). This lineage of H5 viruses can efficiently establish itself in wild birds after circulating among gallinaceous poultry, facilitating reassortment with low pathogenic avian influenza (LPAI) virus strains, enhancing dispersal over long distances and contributing to endemicity. The detection of HPAI H5N8 virus (clade 2.3.4.4B) in 2017 in the Mpumalanga Province of South Africa marked the beginning of an epidemic that devastated the South African poultry industry. Vaccines were tested to assess protection against the circulating field strain. This article describes the performance of a reverse genetics inactivated H5N1 vaccine from Zoetis (RG-H5N1), with 96.1% identity to the circulating HPAI H5N8 virus. Two locally formulated benchmarks, one containing an H5N8 antigen homologous to the field strain (Benchmark-H5N8), the other containing a heterologous (87.6% identity to field virus) LPAI H5N1 antigen (Benchmark-H5N1), were included for comparison. Efficacy was assessed in specific pathogen-free (SPF) chickens using a prime-boost approach (injections at days 21 and 45), followed by a challenge with a South African HPAI H5N8 isolate (70 days of age). The Zoetis RG-H5N1 vaccine and Benchmark-H5N8 outperformed the Benchmark-H5N1 in terms of humoral response against the H5N8 antigen and reduction of shedding. The Zoetis RG-H5N1 vaccine protected 100% of the chickens against clinical disease and death. This study confirmed that antigenically matched inactivated vaccines could induce robust protection and markedly reduce viral shedding.Conditionally licensed vaccine protected against HPAI H5N8 (clade 2.3.4.4B).Complete protection against clinical disease and mortality.Drastic reduction of viral shedding after challenge.
高致病性禽流感（HPAI）病毒源自广东鹅/96 株系，出现在东南亚，随后传播到中东、非洲和欧洲，感染了多种鸟类和哺乳动物（包括人类）。这种 H5 病毒株系在在鸡鸭等家禽中传播后，能够在野生鸟类中有效地建立自身种群，促进与低致病性禽流感（LPAI）病毒株的重配，增强长距离传播能力，并导致地方性流行。2017 年在南非姆普马兰加省检测到 HPAI H5N8 病毒（2.3.4.4B 分支），标志着一场摧毁南非家禽业的疫情的开始。疫苗被测试以评估对循环田间株的保护作用。本文描述了 Zoetis（RG-H5N1）的一种反向遗传灭活 H5N1 疫苗的性能，该疫苗与循环 HPAI H5N8 病毒有 96.1%的同一性。两个当地制定的基准，一个包含与田间株同源的 H5N8 抗原（基准-H5N8），另一个包含异源（与田间病毒有 87.6%的同一性）的 LPAI H5N1 抗原（基准-H5N1），被包括在内进行比较。使用初免-加强免疫方案（第 21 天和 45 天注射）在无特定病原体（SPF）鸡中评估效力，然后用南非 HPAI H5N8 分离株（70 日龄）进行攻毒。Zoetis RG-H5N1 疫苗和基准-H5N8 在针对 H5N8 抗原的体液反应和减少脱落方面优于基准-H5N1。Zoetis RG-H5N1 疫苗保护 100%的鸡免受临床疾病和死亡。本研究证实，抗原匹配的灭活疫苗可诱导强大的保护作用，并显著减少病毒脱落。有条件批准的疫苗可预防 HPAI H5N8（2.3.4.4B 分支）。完全预防临床疾病和死亡率。攻毒后病毒脱落明显减少。
