Protective microbiomes can limit the evolution of host pathogen defense
Protective microbiomes can limit the evolution of host pathogen defense
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DOI：
10.1002/evl3.140
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发表时间：
2019-09-11
影响因子：
5
通讯作者：
Koskella, Britt
中科院分区：
文献类型：
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作者：
Metcalf, C. Jessica E.;Koskella, Britt
宿主免疫力的进化发生在微生物组的背景下，但几乎没有理论可以预测耐受和调节肠道微生物群的需要如何影响对病原体的抗性。我们提出了一个通用模型，以探索在宿主免疫力的最佳投资的条件下，宿主可以，与不能很容易地区分细菌与病原菌，当细菌微生物群可以，与不能保护宿主免受病原体感染的影响。我们发现，随着进化时间的推移，与先天免疫相关的免疫警惕性丧失可能是由于区分病原体和其他微生物物种的挑战。此外，我们发现微生物组物种的保护作用越大，直接或通过与病原体的竞争发挥作用，或者免疫成本越高，免疫警惕性丧失的可能性就越大。相反，当病原体增加宿主死亡率时，这种影响可以逆转。一般来说，当微生物组和病原体物种彼此最相似（就宿主识别而言）时，以及当对病原体的免疫作用较弱时，预测允许免疫警惕性降低的演变所需的免疫成本的大小最低。我们的模型框架明确了在微生物组/病原体歧视的背景下可能塑造免疫进化的核心权衡。我们将讨论这如何告知自然系统中的模式和过程的解释，包括对病原体出现的脆弱性。
The evolution of host immunity occurs in the context of the microbiome, but little theory exists to predict how resistance against pathogens might be influenced by the need to tolerate and regulate commensal microbiota. We present a general model to explore the optimal investment in host immunity under conditions in which the host can, versus cannot easily distinguish among commensal versus pathogenic bacteria, and when commensal microbiota can, versus cannot protect the host against the impacts of pathogen infection. We find that a loss of immune vigilance associated with innate immunity over evolutionary time can occur due to the challenge of discriminating between pathogenic and other microbe species. Further, we find the greater the protective effect of microbiome species, acting either directly or via competition with a pathogen, or the higher the costs of immunity, the more likely the loss of immune vigilance is. Conversely, this effect can be reversed when pathogens increase host mortality. Generally, the magnitude of costs of immunity required to allow evolution of decreased immune vigilance are predicted to be lowest when microbiome and pathogen species most resemble each other (in terms of host recognition), and when immune effects on the pathogen are weak. Our model framework makes explicit the core trade-offs likely to shape the evolution of immunity in the context of microbiome/pathogen discrimination. We discuss how this informs interpretation of patterns and process in natural systems, including vulnerability to pathogen emergence.