狂犬病病毒脑内感染MyD88-/-小鼠对肺脏病理变化的影响

Effects of MyD88-/- mice with rabies virus intracerebral infection on lung pathological changes

  • 摘要: 【目的】明确狂犬病病毒(RABV)脑内感染MyD88基因敲除(MyD88-/-)小鼠对肺脏病理变化的影响,探索MyD88基因缺失对狂犬病发病进程的延迟作用,为进一步揭示RABV的致病机理打下基础。【方法】以RABV的弱毒株rRC-HL和标准强毒株CVS-24分别脑内感染MyD88-/-和野生型(MyD88+/+)小鼠,攻毒剂量1000 FFU/只,以相同方式和剂量接种DMEM作为对照。观察脑内感染后小鼠的临床症状及体质量变化,采集脑内感染后第4和7 d的脑组织和肺脏,通过实时荧光定量PCR检测小鼠脑组织及肺脏内病毒基因和细胞因子的表达情况,并制作肺脏组织切片观察其病理变化。【结果】 MyD88+/+和MyD88-/-小鼠脑内感染弱毒株rRC-HL后出现轻微的临床症状,而标准强毒株CVS-24对MyD88+/+和MyD88-/-小鼠均具有致死性。与MyD88+/+小鼠相比,MyD88-/-小鼠的发病时间和死亡时间均延迟1~2 d,弱毒株rRC-HL脑内感染2种小鼠均从第10 d开始恢复体质量,且临床症状逐渐消失,但MyD88-/-小鼠较MyD88+/+小鼠恢复得更快。脑内感染RABV后,小鼠脑组织相关细胞因子(IFN-α、IFN-γ、IL-1β、MCP-1和TNF-α)的表达发生明显变化,而在肺脏中的表达差异倍数只有少部分超过2.00倍,且随感染时间的推移其变化呈现不规律性。濒死期小鼠肺脏组织切片观察发现,MyD88+/+小鼠肺脏组织切片的细胞核染着色深,肺泡壁稍微增厚,有轻微炎症变化,有巨噬细胞出现; MyD88-/-小鼠肺脏组织切片的细胞核着色浅,肺泡壁增厚不明显,炎症变化较轻,有少量巨噬细胞浸润。【结论】脑内感染后第7 d是RABV在小鼠脑组织中复制能力最强的时段,且脑组织相关细胞因子的表达差异倍数随病程的推移发生明显变化;肺脏组织切片并未发现典型的特征性病理变化,但RABV感染对MyD88-/-小鼠肺脏病理的影响小于MyD88+/+小鼠,即MyD88基因缺失有利于小鼠对抗RABV感染,抑制炎症产生及延迟机体发病。

     

    Abstract: 【Objective】 To clarify the effects of intracerebral infection withrabies virus(RABV) of myD88 gene elimination(MyD88-/-) miceon pulmonary pathology,and to explore the delay effect of myD88 gene loss on the pathogenesis of rabies,so as to lay the foundation for further elucidation of the pathogenesis of RABV.【Method】 Using MyD88-/- and wild-type(MyD88+/+) mice intracerebrally-infected with the weakened strain rRC-HL of RABV and the standard strain CVS-24 respectively,the attack dose was 1000 FFU/mouse for each group. Also,DMEM was vaccinated with the same method and dose as comparisons. Through observing symptoms and changes in body mass of mice after the intracerebral poisoning,collecting brain tissue and lungs on the 4th and 7th days after intracranial poisoning,and detecting the expression of viral genes and cytokines in each group's brain tissue and lungs through real-time fluorescence quantitative PCR, lung tissue sections were prepared to observe the pathological changes.【Result】 MyD88+/+ and MyD88-/- mice showed mild symptoms after brain infection with the weak strain rRC-HL,while the standard strain CVS-24 was fatal to both groups of mice. Compared with MyD88+/+ mice, MyD88-/- mice had delayed onset time and death time by 1 to 2 d. The group of mice which was intracerebrally infected with both species of the weak strain rRC-HL recovered from the 10th day and the symptoms gradually disappeared,but MyD88-/- mice recovered faster than MyD88+/+ mice. After intracerebral infection with RABV,the expression of relevant cytokines(IFN-α,IFN-γ,IL-1β,MCP-1,and TNF-α) in the brain tissue of mice was changed,while only a small portion of the differential multiplicity of the expression in the lungs was more than 2.00 times,and the changes showed irregularities with the time of the attack. In addition,the observation of lung tissue sections from near-death mice revealed that the MyD88+/+ mice had deep nuclear staining, slight thickening of the alveolar wall,slight inflammatory changes,and macrophages. At the same time,MyD88-/- mice lung tissue section cells were lightly pigmented,alveolar wall thickening was not obvious,inflammatory changes were mild,and there were a small number of macrophages infiltration.【Conclusion】 The 7th day after intracerebral poisoning is the period when RABV has the strongest ability to replicate in mouse brain tissue,and the expression difference in brain tissue-related cytokines changes greatly with the course of the disease. Also,lung tissue sections did not reveal typical characteristic pathological changes,but the effect of RABV infection on lung pathology in MyD88-/- mice is less than that of MyD88+/+ mice. In conclusion,the loss of the MyD88 gene helps mice fight RABV infection,inhibits inflammation,and delays the pathogenesis of the body.

     

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