高致病性禽流感病毒(HPAIV)通常从H5和H7亚型的低致病性禽流感病毒(LPAIV)从野生水禽溢出到家禽中。从LPAIV到HPAIV的转化的特征在于在病毒结合和融合蛋白的蛋白水解切割位点获得多碱性切割位点(MBCS),血凝素(HA),导致广泛表达的弗林蛋白酶样蛋白酶切割和激活HA。随后的HPAIV在鸡家禽中全身传播,具有内皮功能,并导致高死亡率的出血性疾病。野生水鸟的HPAIV感染通常较温和,通常无症状,通常与全身播散或内皮功能无关。由于宿主蛋白酶的MBCS切割是家禽中HPAIV的主要毒力决定因素,我们着手确定宿主蛋白酶对HPAIVHA的裂解是否会影响观察到的物种特异性发病机制和嗜性。这里,我们测序了,克隆,并对鸭弗林的表达和功能进行了表征。鸡和鸭之间的弗林蛋白序列非常保守,和鸭弗林蛋白酶在过表达系统中切割HPAIV和四碱基HA,确认其功能。弗林蛋白酶在鸭和鸡组织中广泛表达,表达程度相似,包括原代鸭内皮细胞,维持H5N1HPAIV而不是LPAIV的多周期复制。总之,野生水鸟和鸡家禽之间的弗林蛋白酶样蛋白酶生物学差异不太可能在很大程度上决定在HPAIV的物种特异性发病机理中观察到的明显差异。由于家禽的健康风险,HPAIV疫情是全球关注的问题,野生动物,和人类及其主要经济影响。LPAIV到HPAIV转换的次数,这与从野鸟到家禽的溢出有关,近几十年来一直在增加。此外,来自A/鹅/广东/1/96谱系的H5HPAIV已在候鸟中传播,在家禽和野生鸟类中引起越来越频繁的流行病。候鸟的轻度症状允许HPAIV长距离扩散,证明了解野生鸟类HPAIV发病机理的重要性。这里,我们研究了宿主蛋白酶是否可能是解释鸟类之间HPAIV系统传播程度差异的候选酶.这是第一个报告显示furin的功能和表达在鸡和鸭之间是相当的,这使得弗林蛋白酶样蛋白酶差异不太可能影响HPAIV物种特异性的发病机理和向性。
Highly pathogenic avian influenza viruses (HPAIVs) typically emerge from low-pathogenic avian influenza viruses (LPAIVs) of the H5 and H7 subtypes upon spillover from wild aquatic birds into poultry. The conversion from LPAIV to HPAIV is characterized by the acquisition of a multibasic cleavage site (MBCS) at the proteolytic cleavage site in the viral binding and fusion protein, hemagglutinin (HA), resulting in cleavage and activation of HA by ubiquitously expressed furin-like proteases. The ensuing HPAIVs disseminate systemically in gallinaceous poultry, are endotheliotropic, and cause hemorrhagic disease with high mortality. HPAIV infections in wild aquatic birds are generally milder, often asymptomatic, and generally not associated with systemic dissemination nor endotheliotropic. As MBCS cleavage by host proteases is the main virulence determinant of HPAIVs in poultry, we set out to determine whether cleavage of HPAIV HA by host proteases might influence the observed species-specific pathogenesis and tropism. Here, we sequenced, cloned, and characterized the expression and functionality of duck furin. The furin sequence was strongly conserved between chickens and ducks, and duck furin cleaved HPAIV and tetrabasic HA in an overexpression system, confirming its functionality. Furin was expressed ubiquitously and to similar extents in duck and chicken tissues, including in primary duck endothelial cells, which sustained multicycle replication of H5N1 HPAIV but not LPAIVs. In conclusion, differences in furin-like protease biology between wild aquatic birds and gallinaceous poultry are unlikely to largely determine the stark differences observed in species-specific pathogenesis of HPAIVs. IMPORTANCE HPAIV outbreaks are a global concern due to the health risks for poultry, wildlife, and humans and their major economic impact. The number of LPAIV-to-HPAIV conversions, which is associated with spillover from wild birds to poultry, has been increasing over recent decades. Furthermore, H5 HPAIVs from the A/goose/Guangdong/1/96 lineage have been circulating in migratory birds, causing increasingly frequent epizootics in poultry and wild birds. Milder symptoms in migratory birds allow for dispersion of HPAIVs over long distances, justifying the importance of understanding the pathogenesis of HPAIVs in wild birds. Here, we examined whether host proteases are a likely candidate to explain some differences in the degree of HPAIV systemic dissemination between avian species. This is the first report to show that furin function and expression is comparable between chickens and ducks, which renders the hypothesis unlikely that furin-like protease differences influence the HPAIV species-specific pathogenesis and tropism.