Microsporidia-host interactions in beneficial arthropods: Factors that influence chronic disease

有益节肢动物中微孢子虫与宿主的相互作用：影响慢性疾病的因素

• 批准号: RGPIN-2014-05335
• 负责人: Bjornson, Susan
• 金额: $ 2.26万
• 依托单位: Saint Mary's University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=707964
• 关键词: Microsporidia; host; interactions; beneficial; arthropods

Microsporidia are spore forming, eukaryotic pathogens that cause chronic infections in a wide range of invertebrate and vertebrate hosts. Depending on the host infected, these pathogens cause economic loss and are of veterinary and medical importance. Microsporidia live inside host cells and are fully dependent on their hosts for survival. These pathogens lack functional mitochondria and their reduced genome has resulted in the loss of many metabolic pathways. As a result, microsporidia require host energy for their reproduction and survival. Microsporidia are being described with increased frequency from beneficial arthropods, both those that provide pest control in nature and those that are mass-reared for use as natural enemies in biological control programs. Although microsporidia are defined as pathogens (organisms that grow and develop at the detriment of the host), recent studies have shown that microsporidia do not always cause negative effects with respect to host fitness. In some cases, microsporidia cause chronic debilitating disease, whereas other related hosts remain seemingly unaffected even though the pathogen is able to exploit the latter for its development and proliferation. The characteristics/factors that permit microsporidia to be successful pathogens in some hosts, while remaining unsuccessful in other related hosts, remains poorly understood. The purpose of this proposed study is to evaluate some of the factors that may be associated with pathogen success and could ultimately influence the impact of chronic disease. Our past efforts have focused on the identification and interaction of microsporidia in beneficial insects used for biological pest control, recently including microsporidian pathogens among several lady beetle species. Our more current studies have provided some insight on host specificity of microsporidia and host-pathogen effects. Microsporidia seem to have a relatively broad host range in lady beetles, oftentimes having pronounced effects on larval development while having no observable, detrimental effect on adults. Furthermore, microsporidia affect some lady beetle species profoundly whereas others closely-related species seem to remain unaffected. In some cases, the latter become filled with microsporidian spores (evidence that they serve as a suitable host for the pathogen) and even transmit the pathogen while remaining unaffected. Because microsporidia are designated as pathogens in the strict sense, the question remains as to what role these pathogens play in the many hosts that they infect and what enables microsporidia to become successful pathogens in some hosts while remaining rather benign in others. The proposed study will focus on factors that may influence the success of microsporidia as pathogens that cause chronic disease. These include (1) the impact of stress on the pathogen and disease progression, (2) the effects of multiple infections (more than one pathogen per host) on disease development and host fitness, and (3) the role secondary defense chemicals (alkaloids) in lady beetles on pathogen development and host fitness. Information gained during this study will help contribute toward our current understanding of disease epizootics and the role that chronic disease plays in the regulation of beneficial arthropod populations. Our increased understanding of chronic disease is important to help ensure that beneficial arthropods remain a viable alternative to chemical pest control in agriculture. Furthermore, microsporidia infections are becoming more common in humans, primarily those with a compromised immune system. As a result, microsporidia are emerging pathogens of increasing medical importance.

微孢子虫是一种能形成孢子的真核病原体，可引起多种无脊椎动物和脊椎动物宿主的慢性感染。根据感染的宿主，这些病原体造成经济损失，并具有兽医和医学重要性。微孢子虫生活在宿主细胞内，完全依赖宿主生存。这些病原体缺乏功能性线粒体，其减少的基因组导致许多代谢途径的丧失。因此，微孢子虫需要宿主的能量来繁殖和生存。 微孢子虫在有益节肢动物中的描述频率越来越高，无论是在自然界中提供害虫控制的节肢动物，还是在生物控制计划中作为天敌大量饲养的节肢动物。虽然微孢子虫被定义为病原体（在对宿主不利的情况下生长和发育的生物体），但最近的研究表明，微孢子虫并不总是对宿主适应性造成负面影响。在某些情况下，微孢子虫引起慢性衰弱性疾病，而其他相关宿主似乎不受影响，即使病原体能够利用后者进行发育和增殖。允许微孢子虫在某些宿主中成为成功病原体，而在其他相关宿主中保持不成功的特征/因素仍然知之甚少。 这项拟议研究的目的是评估一些可能与病原体成功相关的因素，并最终影响慢性疾病的影响。我们过去的努力集中在微孢子虫的识别和相互作用的有益昆虫用于生物防治，最近包括微孢子虫病原体之间的几个瓢虫物种。我们最近的研究提供了一些微孢子虫的宿主特异性和宿主-病原体效应的见解。微孢子虫似乎在瓢虫中具有相对广泛的宿主范围，通常对幼虫发育有显著影响，而对成虫没有明显的有害影响。此外，微孢子虫影响一些瓢虫物种深刻，而其他密切相关的物种似乎不受影响。在某些情况下，后者变得充满微孢子虫孢子（证据表明它们作为病原体的合适宿主），甚至传播病原体而不受影响。由于微孢子虫被指定为严格意义上的病原体，问题仍然是这些病原体在它们感染的许多宿主中发挥什么作用，以及是什么使微孢子虫在某些宿主中成为成功的病原体，而在其他宿主中保持相当良性。 这项拟议的研究将集中在可能影响微孢子虫作为导致慢性疾病的病原体的成功因素上。这些包括（1）压力对病原体和疾病进展的影响，（2）多重感染（每个宿主不止一种病原体）对疾病发展和宿主适应性的影响，以及（3）瓢虫中的二级防御化学物质（生物碱）对病原体发展和宿主适应性的作用。 在这项研究中获得的信息将有助于我们目前对疾病流行病学的理解和慢性疾病在有益节肢动物种群的调节中所起的作用。我们对慢性病的了解的增加对于帮助确保有益的节肢动物仍然是农业中化学害虫控制的可行替代品非常重要。此外，微孢子虫感染在人类中越来越常见，主要是那些免疫系统受损的人。因此，微孢子虫是医学重要性日益增加的新兴病原体。