Highly conserved motifs in NS1 and PB1-F2 proteins of highly pathogenic avian influenza viruses and their functionalities in virulence, immune responses and pathological alterations like acute lung injury (ALI)

据世界卫生组织估计，呼吸道感染占全球死亡人数的6%以上。重要的是，在所有能够感染呼吸道的病原体中，甲型流感病毒(IAV)是最常见和最具破坏性的。除了数百万人住院和数千人死亡外，这些病原体在每年的季节性流感期间还会导致巨大的经济损失。更令人担忧的是，IAV有可能导致大流行暴发，数百万受害者，如1918年的西班牙流感爆发，IAV被认为是即将到来的危及生命的大流行的潜在病原体。IAV的人畜共患病潜力是自1997年以来人类大流行爆发和H5N1亚型高致病性禽类IAV(HPAI)持续零星传播的根本原因。60%的高病死率强调了了解人类HPAI感染生物学的必要性。为了理解这一高病死率，人们对不同的病毒蛋白进行了多种方法的研究。除了HPAI的血凝素蛋白对其毒力和最终传播的贡献外，人们还研究了聚合酶蛋白在提高H5N1禽流感病毒复制效率方面的作用。到目前为止，对非结构蛋白NS1和PB1-F2的研究工作较少。这两种蛋白都具有免疫调节和干扰素拮抗特性，被描述为毒力决定因素。总体而言，在季节性人类和HPAI中存在差异的氨基酸基序成为了解HPAI感染严重性的重点。关于NS1蛋白，几乎所有H5N1分离株都存在SH3结合基序(aa212-217)，而季节性的人IAV则不存在这一基序。在PB1-F2的背景下，四个氨基酸(促炎症基序；L62、R75、R79和L82)被鉴定为细胞因子释放和炎症反应的贡献者，并且在禽类IAV中高度存在，包括在人H5N1分离株中的高流行率。在本研究中，描述的NS1和PB1-F2基序对HPAI的毒力、免疫应答的调节以及最终不同宿主(鸟类和哺乳动物)的免疫病理和急性肺损伤的影响将被广泛地研究。了解人类HPAI毒力的基本机制和这些基序的影响可能会加强对HPAI感染进行更有指导的监测和建立额外治疗选择的能力。

As estimated by the World Health Organization, infections of the respiratory tract are responsible for more than 6 percent of all deaths worldwide. Importantly, among all pathogens having the capability to infect the respiratory tract, influenza A viruses (IAV) are among the most common and devastating. In addition to millions of hospitalizations and thousands of deaths, these pathogens lead to enormous economic losses during the seasonal influenza each year. Even more worrisome, IAV have the potential to cause pandemic outbreaks with several million victims, such as the Spanish flu outbreak in 1918 and IAV are discussed as potential causative agent for upcoming life-threatening pandemics. The zoonotic potential of IAV is fundamental for the occurrence of pandemic outbreaks in humans and the ongoing, sporadic transmission of highly pathogenic avian IAV (HPAI) of the subtype H5N1 to humans since 1997. The high case fatality rate of 60%, emphasizes the need to understand the biology of HPAI infection of humans. To understand this high case fatality rate, multiple approaches focusing on different viral proteins have been conducted. Beside the contribution of the hemagglutinin protein of HPAI to their virulence and finally transmission, the polymerase proteins have been studied for their role in increasing replication efficiency of H5N1 IAV. Less effort has been put into study of the non-structural proteins NS1 and PB1-F2 to this point. Both proteins carry immune modulatory and interferon antagonistic properties and are described as virulence determinants. In general, amino-acid motifs, which are differentially present in seasonal human and HPAI came into focus of interest for understanding the severeness of HPAI infections. Regarding the NS1 protein, a SH3 binding motif (aa212-217) is present in almost all avian IAV isolates with a special position of H5N1 isolates in contrast to seasonal human IAV lacking this motif. In the context of PB1-F2, four amino acids (pro-inflammatory motif; L62, R75, R79 and L82) have been identified as contributor to cytokine release and inflammatory responses and are highly present in avian IAV, including a high prevalence in human H5N1 isolates.In this study, the impact of the depicted motifs in NS1 and PB1-F2 on virulence of HPAI, modulation of immune responses and finally immune pathology and acute lung injury in different hosts (avian and mammalian) will be broadly investigated. Understanding the basal mechanisms of HPAI virulence in humans and the impact of these motifs potentially strengthen the ability of more guided surveillance and set up of additional treatment options for HPAI infections.