Highly Pathogenic Avian Influenza (HPAI) H5N1 virus in Finland in 2021–2023 – Genetic diversity of the viruses and infection kinetics in human dendritic cells

Highly pathogenic avian influenza (HPAI) H5N1 is known for its virulence and zoonotic potential, infecting birds and mammals, thus raising public health concerns. Since 2021 its spread among birds has led to cross-species transmission causing epizootics among mammals, eventually impacting fur animal farms in Finland in 2023. To analyze the infectivity of the Finnish H5N1 isolates in human cells, representatives of diverse H5N1 isolates were selected based on the genetic differences, host animal species, and the year of occurrence. The infection kinetics of the selected H5N1 isolates from wild pheasant and fox, and fur animals blue fox and white mink were examined in human monocyte-derived dendritic cells (moDCs) with H5N1 human isolate as a control. Although the isolate from pheasant (a wild bird) showed weakly reduced replication and viral protein expression in human cells compared to mammalian isolates, no discernible differences in virus replication in moDCs was observed. This study revealed similar infectivity in human moDCs for all five H5N1 isolates, regardless of the observed genetic differences. While H5N1 human infections remain rare, the virus poses a risk for widespread epizootics in mammals such as fur animal farms and, more recently, dairy cattle.

高致病性禽流感（Highly Pathogenic Avian Influenza, HPAI）H5N1亚型以其强致病性与人畜共患潜力著称，可感染鸟类与哺乳动物，由此引发公共卫生领域的广泛担忧。自2021年起，该病毒在鸟类间的传播引发跨物种传播事件，导致哺乳动物暴发兽疫，最终于2023年波及芬兰的毛皮动物养殖场。为分析芬兰H5N1分离株在人体细胞中的感染性，研究团队基于遗传差异、宿主动物种类与分离年份，选取了不同H5N1分离株的代表性毒株。研究以H5N1人类分离株为对照，在人单核细胞源性树突状细胞（monocyte-derived dendritic cells, moDCs）中检测了野生雉鸡、狐狸来源以及蓝狐、白色水貂来源的选定H5N1分离株的感染动力学特征。尽管与哺乳动物来源的分离株相比，野生雉鸡来源的分离株在人体细胞中的复制水平与病毒蛋白表达量仅出现轻微下降，但在moDCs中未观察到病毒复制存在显著差异。本研究显示，无论遗传差异如何，所有5株H5N1分离株在人moDCs中均表现出相近的感染性。尽管人类感染H5N1的病例仍较为罕见，但该病毒对哺乳动物（如毛皮动物养殖场畜禽）乃至近期受波及的乳牛均存在引发大规模兽疫的风险。