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

病毒性疾病可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。病毒如甲型流感病毒、狂犬病病毒、呼吸道合胞病毒、冠状病毒（COVID 19）使用多种策略附着并进入其宿主的上皮细胞。然而，在许多这些例子中，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，从而能够开发病毒性疾病的创新预防和治疗策略。该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（半乳糖凝集素）在病毒粘附中的作用。几种半乳糖凝集素类型存在于鱼类和人类中，并在防御病毒感染中发挥作用。研究人员最近的一项研究表明，一种特殊的半乳糖凝集素类型（半乳糖凝集素-9）促进了病毒的感染性。这些观察结果为半乳糖凝集素作为抗病毒防御因子的作用建立了新的范例，因为它们表明一些病毒已经进化为“劫持”半乳糖凝集素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，该项目旨在阐明半乳糖凝集素-9促进病毒感染的分子机制。该研究将为人类和兽医学（包括商业水产养殖）相关的病毒感染提供关键和有用的信息。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民族的学生。 传染性造血细胞坏死病毒（IHNV）是世界范围内自然和养殖鱼类中最重要的病原体之一。环境压力和高密度水产养殖可导致IHNV的灾难性爆发。IHNV感染涉及病毒包膜糖蛋白刺突与鱼上皮细胞上的糖蛋白受体的相互作用，但其机制尚不清楚。研究者的实验室解决了宿主表达的糖结合蛋白的结构/功能方面，例如半乳糖凝集素，在感染性疾病中使用小鼠和非哺乳动物模型，例如斑马鱼。已经描述了几种结构上不同的半乳糖凝集素类型（例如半乳糖凝集素-1，Gal 1; Gal 3;和Gal 9）。虽然斑马鱼Gal 1和Gal 3阻碍IHNV病毒粘附，但含有两个糖识别结构域的Gal 9促进病毒感染性。这导致了这样的假设，即斑马鱼Gal 9通过将病毒包膜糖蛋白与鱼上皮聚糖交联来增强病毒附着，并且在环境应激下，表皮粘液的保护作用减弱。将通过最先进的生物化学、分子和遗传实验方法研究涉及Gal 9介导的增强IHNV进入宿主上皮细胞的机制、病毒复制的潜在增加、表皮粘液的保护作用和应激环境条件的有害作用来测试该假设。这项研究将检验半乳糖凝集素作为抗传染病防御因子的长期概念，并将揭示与人类和兽医相关的其他包膜病毒（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知识价值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.