中文摘要：

目的建立一种新型的与临床相关的研究动物免疫反应的体系,该体系能够使研究者在同一宿主体内观察到不同基因型细菌对抗机体免疫的差异,为致病微生物的防治提供新的思路。方法首先向小鼠注射环磷酰胺构建粒缺小鼠模型,再向小鼠腹腔注射不同基因型的大肠杆菌模式菌株Escherichia coli K-12的2株混合菌株,一定时间后将小鼠处死并取小鼠各组织液,将这些样品涂布,长出的每个菌落先后经过菌落PCR以及荧光显微镜观察来确定其基因型,并统计2种菌的比例。结果小鼠腹腔注射环磷酰胺后外周血中性粒细胞降至原来水平的10%左右,骨髓中性粒细胞降至原水平的5%左右;向粒缺小鼠腹腔按照1∶1比例注射不同基因型的2株E.coli K-12的菌后,在第3天二者在小鼠腹腔以及各脏器内的比值从原先的1左右升高到了5左右,且有显著性差异（P〈0.01）;而向粒缺小鼠腹腔按照1∶1比例注射2株不同荧光蛋白标记的相同的E.coli K-12野生型菌株后,2株菌在小鼠体内的存活并没有明显的差异（保持在1左右）。结论我们建立的这种新型免疫反应评价体系能够准确反应出不同基因型细菌在粒缺的小鼠体内对抗机体免疫的能力。此体系中,实验菌株和对照菌株同时注射到同一受鼠,很好的解决了小鼠个体间差异的问题,这种新的实验系统的建立对研究放化疗患者的免疫应答机制和抗感染治疗策略的制定具有重要指导意义。

英文摘要：

Chemo-and radiotherapy are extensively used to treat various hematological malignancies and solid tumors. Neutropenia and related infection are the most important dose-limiting toxicities of these anti-cancer treatments, impacting on quality of life and clinical outcomes, with the potential to cause death. Here, we developed a novel clinically relevant mouse model to accurately assess the response of bacteria to host immune defense system in the neutropenic patients. Neutropenia was induced in mice by cyclophosphamide（CPA）, a commonly used anticancer drug. To minimize the mouse-to-mouse variability, we mixed isogenic WT and mutant Escherichia coli K-12 cells, and the mixture（1∶1 ratio）was intra-peritoneally（i.p.） injected into the CPA treated mice. The mice were sacrificed at 0-3 days and the cardiac blood, peritoneal lavage fluid, and homogenizedorgans were collected. Then the total number of viable bacterial cells in each compartment was assessed by platingsamples on LB agar plates; the phenotype and the identity of each colony were determined by PCR and directobservation under fluorescence microscope. The ratio of the two input bacterial stains was calculated thereafter. Datashowed that CPA treatment significantly reduced granulocyte count to 10% of the normal level in peripheral bloodand to 5% of the normal level in the bone marrow. Three days after the injection of a 1∶1 mixed bacterial populationcontaining WT E.coli K-12 bacteria and mutated E.coli K-12 bacteria with lower proliferation rate, the ratio of theviable WT bacteria to mutated bacteria in the inflamed peritoneal cavity and several other organs significantlyincreased from 1 to 5（P〈0.01）. As a control, the ratio of the viable WT bacteria to WT bacteria under the samecondition remained unaltered. Thus, in this study, we have established a new clinical relevant mouse model, whichcould be used to accurately measure the in vivo response of bacteria to host immune defense system. This modelshould be of importance and can facilitate