Roles of galectins in viral infection of mucosal epithelia using the zebrafish model system

病毒性疾病可能对人类和动物种群产生严重影响，包括养殖和天然鱼类种群。甲型流感病毒、狂犬病病毒、呼吸道合胞病毒、冠状病毒(COVID19)等病毒使用各种各样的策略附着和进入宿主的上皮细胞。然而，在其中许多例子中，详细的机制仍然不清楚，迫切需要进行研究，以获得关键信息，从而能够开发针对病毒疾病的创新预防和治疗战略。本研究项目使用斑马鱼模型系统来解决有关病毒感染机制的问题，重点是糖结合蛋白(Galectins)在病毒黏附中的作用(S)。鱼和人类中都存在几种类型的半乳凝素，它们具有抵御病毒感染的功能。研究人员最近的一项研究显示，一种特殊的Galectin类型(Galectin-9)促进了病毒的传染性。这些观察结果为Galectins作为抗病毒防御因子的作用建立了一个新的范式，因为它们表明一些病毒已经进化成“劫持”Galectins以促进病毒宿主进入。通过使用创新的实验方法和最先进的分子工具，该项目旨在阐明Galectin-9促进病毒感染的分子机制。这项研究将为与人类和兽医相关的病毒感染提供关键和有用的信息，包括商业水产养殖。重要的是，这些研究还将有助于研究生、本科生和高中生的教育和实践培训，包括来自代表性不足的少数族裔的学生。传染性造血坏死病毒(IHNV)是世界范围内自然和养殖种群中最重要的鱼类病原体之一。环境压力和高密度水产养殖可能导致灾难性的IHNV暴发。甲型肝炎病毒的感染涉及病毒包膜糖蛋白尖峰与鱼类上皮细胞上的糖蛋白受体(S)的相互作用，但机制尚不清楚。研究人员的实验室使用小鼠和非哺乳动物模型(如斑马鱼)，研究在传染病中宿主表达的糖结合蛋白的结构/功能方面，如Galectins。已经描述了几种结构上不同的Galectin类型(例如Galectin-1、Gal1、Gal3和Gal9)。斑马鱼Gal1和Gal3阻碍IHNV病毒黏附，而Gal9含有两个糖识别结构域，促进病毒感染性。这导致了一种假设，即斑马鱼Gal9通过将病毒包膜糖蛋白与鱼类上皮多聚糖交联来增强病毒附着，并且在环境压力下，表皮粘液的保护作用减弱。这一假说将通过最先进的生化、分子和遗传学实验方法进行验证，调查Gal9介导的IHNV进入宿主上皮细胞的机制(S)，以及病毒复制的潜在增加，表皮粘液的保护作用，以及应激环境条件的有害影响。这项研究将检验长期持有的半乳糖凝集素作为抵御传染病的因素的概念，并将揭示与人类和兽医相关的其他包膜病毒(例如流感、狂犬病和冠状病毒)相关的基本感染机制。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Viral diseases can have a severe impact on both human and animal populations, including farmed and natural fish populations. Viruses such as influenza A virus, rabies, respiratory syncytial virus, coronaviruses (COVID19), use a wide variety of strategies to attach to and enter their hosts’ epithelial cells. In many of these examples, however, the detailed mechanisms still remain unclear and urgent research is needed to gain the key information that would enable the development of innovative preventive and therapeutic strategies for viral disease. This research project uses the zebrafish model system to address questions about the mechanisms involved in viral infection, with focus on the role(s) of sugar-binding proteins (galectins) in viral adhesion. Several galectin types are present in both fish and humans, and function in defense against viral infection. A recent study by the investigators revealed that a particular galectin type (galectin-9) promotes viral infectivity. These observations established a new paradigm for the role of galectins as anti-viral defense factors, as they suggest that some viruses have evolved to “hijack” galectins to facilitate viral host entry. By the use of innovative experimental approaches and state-of-the-art molecular tools, this project is aimed at elucidating the molecular mechanisms by which galectin-9 promotes viral infection. The research will provide critical and useful information for viral infections relevant to human and veterinary medicine, including commercial aquaculture. Importantly, these studies will also contribute to the education and hands-on training of graduate, undergraduate, and high school students, including students from underrepresented minorities. The infectious hematopoietic necrosis virus (IHNV) is one of the most important fish pathogens in natural and farmed populations worldwide. Environmental stress and high-density aquaculture can lead to catastrophic IHNV outbreaks. Infection by IHNV involves interaction of the viral envelope glycoprotein spikes with glycoprotein receptor(s) on the fish epithelia, but the mechanisms remain unknown. The investigator’s lab addresses structural/functional aspects of sugar-binding proteins expressed by the host, such as galectins, in infectious disease using both murine and non-mammalian models, such as zebrafish. Several structurally different galectin types have been described (e.g. galectin-1, Gal1; Gal3; and Gal9). While the zebrafish Gal1 and Gal3 hinder IHNV viral adhesion, Gal9, which houses two sugar-recognition domains, promotes viral infectivity. This led to the hypothesis that zebrafish Gal9 enhances viral attachment by crosslinking the viral envelope glycoprotein to fish epithelial glycans, and that under environmental stress the protective role of epidermal mucus is diminished. The hypothesis will be tested by investigating though state-of-the-art biochemical, molecular, and genetic experimental approaches the mechanism(s) involved in Gal9-mediated enhancement of IHNV entry into the host epithelial cell, and potential increase of viral replication, the epidermal mucus’ protective role, and the detrimental effect of stressful environmental conditions. This research will be examine the long-held concept of galectins as defense factors against infectious disease, and will unravel basic infection mechanisms pertinent to other enveloped viruses (e.g. influenza, rabies, and coronavirus) of human and veterinary relevance.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.