Amphibian innate immunity and impact of environmental stress

全球超过7000种两栖动物中有三分之一受到威胁。病因是复杂的，与新兴的病原体的近端原因。真菌和病毒感染导致的两栖动物大规模死亡表明，环境破坏了青蛙免疫系统抵御感染的能力。在先天免疫的最前沿，抵抗病原体的第一道防线是皮肤上皮屏障和表面分泌的宿主防御肽（HDPs）。它们共同充当有机体外部和内部环境之间的界面。在两栖动物中发现了多种多样的HDPs，研究证明了它们对广谱病原体的抗菌活性。最近在哺乳动物中的发现表明HDP是多方面的，并且通过分子和细胞网络的协调在免疫调节中发挥重要作用。尽管如此，由于缺乏可行的体外系统来研究它们的活性，对两栖动物HDP的研究受到了很大的阻碍。我的研究计划旨在解决这一知识差距，以了解青蛙HDP对青蛙上皮细胞的免疫调节活性，这种活动如何影响对病原体的抵抗力，以及这些宿主-病原体相互作用如何受到气候变化导致的环境温度变化的影响，导致疾病易感性和两栖动物死亡率。最近，我的实验室已经产生并表征了非洲爪蟾背部皮肤上皮细胞系（Xela DS 2），该细胞系易受已知青蛙病原体（青蛙病毒3，FV 3）感染，使我的实验室处于独特的（也是唯一的）位置，以阐明青蛙HDP作为免疫调节剂的分子和功能作用。我的研究将使用从转录组学到细胞内通路激活到细胞功能和病原体挑战的全球系统方法来阐明关键免疫基因（细胞因子，趋化因子，HDPs）的调节并确定新的基因靶点。这种创新的方法将整合HDP驱动的分子事件与上皮细胞功能和FV 3易感性，重点关注与气候变化相关的温度变化如何在皮肤上皮屏障水平上扰乱这些宿主-病原体动态。这些新的方法将被翻译为本地北美林蛙，已经进化到能够承受极端的温度变化，以阐明宿主免疫和对环境压力反应的保守和不同机制。我的研究将大大推进我们对复杂的宿主-病原体-环境相互作用可能影响加拿大青蛙物种的理解，并将探索HDP疗法作为预防或治疗策略的实用性，以减轻病原体相关的两栖动物死亡。这些研究有助于设计病原体预防策略和实施政策，在加拿大两栖动物保护。

One third of >7000 amphibian species are threatened globally. The etiology is complex, with emerging pathogens the proximal cause. Mass amphibian die-offs resulting from fungal and viral infections suggest an environment that undermines frog immune system competency to defend against infection. At the forefront of innate immunity, the first line of defense against pathogens, is the skin epithelial barrier and the surface secreted host defense peptides (HDPs). Together they act as the interface between an organism's external and internal environments. Great diversity of HDPs is found amongst amphibians and studies have documented their antimicrobial activity against a broad-spectrum of pathogens. Recent discoveries in mammals suggest HDPs are multifaceted and play an important role in immune modulation through coordination of molecular and cellular networks. Despite this, studies on amphibian HDPs have been greatly hampered due to a lack of feasible in vitro systems to study their activity. My research program aims to address this knowledge gap in order to understand the immune modulating activity of frog HDPs on frog epithelial cells, how this activity impacts resistance to pathogens, and how these host-pathogen interactions may be affected by changes in environmental temperature as a result of climate change, leading to disease susceptibility and amphibian mortality. Recently, my lab has generated and characterized a Xenopus laevis dorsal skin epithelial cell line (Xela DS2) that is susceptible to infection with a known frog pathogen (Frog virus 3, FV3), placing my laboratory in a unique (and only) position to elucidate the molecular and functional roles of frog HDPs as immune modulators. My research will use a global systems approach from transcriptomics to intracellular pathway activation to cell function and pathogen challenge to elucidate the regulation of key immune genes (cytokines, chemokines, HDPs) and identify novel gene targets. This innovative approach will integrate HDP-driven molecular events with epithelial cell function and FV3 susceptibility, focusing on how temperature shifts associated with climate change perturb these host-pathogen dynamics at the level of the skin epithelial barrier. These novel approaches will be translated to the native North American wood frog that has evolved to withstand extreme changes in temperature to illuminate conserved and divergent mechanisms of host immunity and response to environmental stress. My research will significantly advance our understanding of how complex host-pathogen-environment interactions may be impacting Canadian frog species and will explore the utility of HDP therapy as a prevention or treatment strategy to mitigate pathogen-related amphibian deaths. These studies are instrumental for the design of pathogen prevention strategies and implementation of policies for amphibian conservation in Canada.