Abstract：
Apicomplexans are a protozoan phylum of obligate parasites which may be highly virulent during acute infections, but may also persist as chronic infections which appear to have little fitness cost. Babesia microti is an apicomplexan haemoparasite that, in immunocompromised individuals, can cause severe, potentially fatal disease. However, in its natural host, wild field voles (Microtus agrestis), it exhibits chronic infections that have no detectable impact on survival or female fecundity. How is damage minimized, and what is the impact on the host\'s immune state and health? We examine the differences in immune state (here represented by expression of immune-related genes in multiple tissues) associated with several common chronic infections in a population of wild field voles. While some infections show little impact on immune state, we find strong associations between immune state and B. microti. These include indications of clearance of infected erythrocytes (increased macrophage activity in the spleen) and activity likely associated with minimizing damage from the infection (anti-inflammatory and antioxidant activity in the blood). By analysing gene expression from the same individuals at multiple time points, we show that the observed changes are a response to infection, rather than a risk factor. Our results point towards continual investment to minimize the damage caused by the infection. Thus, we shed light on how wild animals can tolerate some chronic infections, but emphasize that this tolerance does not come without a cost.
摘要：
顶丛是专性寄生虫的原生动物门，在急性感染期间可能具有高毒力。但也可能持续作为慢性感染，这似乎有很少的健身费用。微型巴贝斯虫是一种顶复性血寄生虫，在免疫受损的个体中，会导致严重的，潜在的致命疾病。然而,在它的自然宿主中，野田田鼠（田鼠），它表现出慢性感染，对存活或女性繁殖力没有可检测的影响。如何将损害最小化，以及对宿主的免疫状态和健康有什么影响？我们研究了与野生田鼠种群中几种常见慢性感染相关的免疫状态差异（此处由多个组织中免疫相关基因的表达表示）。虽然有些感染对免疫状态影响不大，我们发现免疫状态和B.microti之间有很强的关联。这些包括被感染的红细胞的清除(脾脏中巨噬细胞活性增加)和可能与感染的损害最小化相关的活性(血液中的抗炎和抗氧化活性)。通过分析同一个体在多个时间点的基因表达，我们表明观察到的变化是对感染的反应，而不是风险因素。我们的结果指向持续投资，以最大程度地减少感染造成的损害。因此，我们揭示了野生动物如何耐受一些慢性感染，但强调这种宽容不是没有代价的。
