Trappeniers Katrien, Matetovici Irina, Van Den Abbeele Jan, De Vooght Linda
Department of Biomedical Sciences, Institute of Tropical Medicine Antwerp, Antwerp, Belgium.
Front Microbiol. 2019 Jul 24;10:1650. doi: 10.3389/fmicb.2019.01650. eCollection 2019.
, a vertically transmitted facultative symbiont of the tsetse fly, is a bacterium in the early/intermediate state of its transition toward symbiosis, representing an important model for investigating how the insect host immune defense response is regulated to allow endosymbionts to establish a chronic infection within their hosts without being eliminated. In this study, we report on the establishment of a tsetse fly line devoid of only, allowing us to experimentally investigate (i) the complex immunological interactions between a single bacterial species and its host, (ii) how the symbiont population is kept under control, and (iii) the impact of the symbiont on the vector competence of the tsetse fly to transmit the sleeping sickness parasite. Comparative transcriptome analysis showed no difference in the expression of genes involved in innate immune processes between symbiont-harboring ( ) and -free ( ) flies. Re-exposure of ( ) flies to the endosymbiotic bacterium resulted in a moderate immune response, whereas exposure to pathogenic or to a close non-insect associated relative of , i.e., , resulted in full immune activation. We also showed that densities are not affected by experimental activation or suppression of the host immune system, indicating that is resistant to mounted immune attacks and that the host immune system does not play a major role in controlling proliferation. Finally, we demonstrate that the absence or presence of in the tsetse fly does not alter its capacity to mount an immune response to pathogens nor does it affect the fly's susceptibility toward trypanosome infection.
作为采采蝇的一种垂直传播的兼性共生菌，处于向共生转变的早期/中期状态，是研究昆虫宿主免疫防御反应如何被调节以使内共生菌在其宿主体内建立慢性感染而不被清除的重要模型。在本研究中，我们报道了建立一种仅缺乏[共生菌名称]的采采蝇品系，这使我们能够通过实验研究：（i）单一细菌物种与其宿主之间复杂的免疫相互作用；（ii）共生菌群体如何被控制；（iii）共生菌对采采蝇传播昏睡病寄生虫的媒介能力的影响。比较转录组分析表明，携带共生菌的（[有菌采采蝇名称]）和无菌的（[无菌采采蝇名称]）采采蝇在先天免疫过程相关基因的表达上没有差异。将（[有菌采采蝇名称]）采采蝇重新暴露于内共生菌会引发适度的免疫反应，而暴露于致病性[细菌名称]或与其亲缘关系较近的非昆虫相关菌，即[相关菌名称]，则会导致完全免疫激活。我们还表明，[共生菌名称]的密度不受宿主免疫系统实验性激活或抑制的影响，这表明[共生菌名称]对宿主发动的免疫攻击具有抗性，并且宿主免疫系统在控制[共生菌名称]增殖方面不发挥主要作用。最后，我们证明采采蝇中[共生菌名称]的有无不会改变其对病原体产生免疫反应的能力，也不会影响采采蝇对锥虫感染的易感性。
