Variation in Immune Defense Shapes Disease Outcomes in Laboratory and Wild Daphnia
Variation in Immune Defense Shapes Disease Outcomes in Laboratory and Wild Daphnia
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DOI：
10.1093/icb/icz079
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发表时间：
2019-11-01
影响因子：
2.6
通讯作者：
Caceres, Carla E.
中科院分区：
文献类型：
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作者：
Merrill, Tara E. Stewart;Hall, Spencer R.;Caceres, Carla E.
宿主易感性可能是传染病传播的关键，了解其基础是生态免疫学的目标。在这里，我们采用了一系列的机械测试，以评估四个因素通常假设影响主机的易感性：寄生虫暴露，感染障碍，免疫反应，和身体大小。我们测试了这些因素在水生宿主寄生虫系统（水蚤dentifera和真菌寄生虫，Metschnikowia bicuspidata）使用实验室饲养和现场收集的主机。我们发现支持每个因素作为感染的驱动力。通过消耗感染性真菌孢子而发生的寄生虫暴露增加了宿主感染的可能性。宿主的肠道上皮作为感染的屏障，但在相反的方式，我们预测：薄前肠上皮细胞比厚上皮细胞更耐感染孢子。这种关系可能是介导的结构属性与上皮细胞的高度。真菌孢子突破宿主的肠道屏障引起强度依赖性血细胞反应，降低了一些水蚤感染的可能性。虽然较大的身体大小与孢子摄入水平的增加有关，但较大的宿主也具有较低的寄生虫攻击频率，较低的穿透性肠道屏障和较强的血细胞反应。在研究了宿主易感性的机制之后，我们提出了一个问题：这四个因素对感染结果的影响是相等的还是不对称的？信息理论方法揭示，宿主免疫防御（屏障和免疫反应）在介导感染结果中发挥了最大的作用。这两个免疫学特征可能是有价值的指标，连接主机易感性传染病的传播。
Synopsis Host susceptibility may be critical for the spread of infectious disease, and understanding its basis is a goal of ecological immunology. Here, we employed a series of mechanistic tests to evaluate four factors commonly assumed to influence host susceptibility: parasite exposure, barriers to infection, immune responses, and body size. We tested these factors in an aquatic host-parasite system (Daphnia dentifera and the fungal parasite, Metschnikowia bicuspidata) using both laboratory-reared and field-collected hosts. We found support for each factor as a driver of infection. Elevated parasite exposure, which occurs through consumption of infectious fungal spores, increased a host's probability of infection. The host's gut epithelium functioned as a barrier to infection, but in the opposite manner from which we predicted: thinner anterior gut epithelia were more resistant to infectious spores than thick epithelia. This relationship may be mediated by structural attributes associated with epithelial cell height. Fungal spores that breached the host's gut barrier elicited an intensity-dependent hemocyte response that decreased the probability of infection for some Daphnia. Although larger body sizes were associated with increased levels of spore ingestion, larger hosts also had lower frequencies of parasite attack, less penetrable gut barriers, and stronger hemocyte responses. After investigating which mechanisms underlie host susceptibility, we asked: do these four factors contribute equally or asymmetrically to the outcome of infection? An information-theoretic approach revealed that host immune defenses (barriers and immune responses) played the strongest roles in mediating infection outcomes. These two immunological traits may be valuable metrics for linking host susceptibility to the spread of infectious disease.