约氏疟原虫两个虫株的生存竞争与疟原虫属基于coxⅢ基因的系统进化研究

发布时间：2018-03-07 08:29

  本文选题：疟原虫　切入点：混合感染　出处：《厦门大学》2009年硕士论文　论文类型：学位论文

【摘要】： 混合感染在疟原虫感染中是一种极为普遍的现象,混合感染发生后,宿主-寄生虫系统会发生一系列比单独感染时更为复杂的相互作用,可能对疟原虫毒力进化产生重要的影响。另一方面,可能会对宿主免疫应答的产生及效应强度产生重要的影响。由此看来,为了深入阐明疟原虫感染宿主机体免疫应答的机制,以对疫苗开发做出更好的指导作用,加大开展混合感染对于宿主免疫系统应答的影响是非常必要的。 为了对同种而基因型有差异的虫株进行分型与定量,我们采用了实时荧光定量PCR(RTQ-PCR)的方法。本研究中找到了合适的分子标记标识约氏疟原虫两个虫株17XNL与265BY,运用相对定量来对混合感染进程中两个虫株的比例进行了实时监测。实验结果表明两种毒力不同的虫株在宿主体内发生竞争作用时,毒力强的一方总是占据着主动地位,它们总能在竞争中获胜。当17XNL:265BY=5:5感染小鼠时,265BY在群体中在12天时已经占据了81%的比例。 结合感染进程中宿主存活率,原虫血症水平等数据,我们能比较充分地了解两种毒力不同的虫株混合感染时的生存竞争状况及其宿主免疫反应的表征。当混合感染发生时,虫株群体数量的变化并不简单等同于两种虫株单独感染时数量的简单叠加,不论虫株毒力强弱抑或混合感染时虫株的比例不同,其中每一种虫株都受到了不同程度的抑制作用。以初始感染比例17XNL:265BY分别为1:9和9:1为例,前者在14天时17XXL被抑制的程度达到了98%,而后者中265BY在14天时被抑制的程度为60%。虽然目前还不清楚这种动态变化的发生与宿主免疫系统影响的具体关联,但是本实验为下一步探寻宿主免疫应答的细胞因子的变化,阐明保护性和病理性免疫应答动态平衡的调控机制奠定了一定的基础。 本论文亦以厦门某医院一位自然感染间日疟原虫患者的血液样本为研究材料,提取基因组DNA,扩增coxⅢ基因序列,并以之作为分子标记,构建系统发生树,探讨了coxⅢ是否可以作为疟原虫属不同种之间分子系统进化研究的合适基因。通过本文中选取的疟原虫属13个种加上本实验获得的间日疟原虫种,依据coxⅢ基因建立的系统进化树来看,它可以很好地反映疟原虫属不同物种之间的遗传亲缘关系。今后的研究中可以利用coxⅢ这一有效的工具开展寄生虫生物分类及系统发育关系的研究工作。
[Abstract]:Mixed infection is an extremely common phenomenon in Plasmodium infection, where a host-parasite system has a series of more complex interactions than a single infection. May have an important impact on the virulence evolution of Plasmodium. On the other hand, it may have an important effect on the generation and intensity of host immune response. Therefore, in order to further elucidate the mechanism of immune response of host body infected by Plasmodium, In order to provide better guidance for vaccine development, it is necessary to increase the effect of mixed infection on host immune system response. In order to type and quantify the strains of the same species with different genotypes, We used the method of real-time fluorescence quantitative PCRQ-PCR.A suitable molecular marker was found to identify two plasmodium strains 17XNL and 265BY. the proportion of two strains in the process of mixed infection was measured by relative quantification. The results showed that when two different virulence insect strains compete in the host, The virulent side always takes the initiative, and they always win the competition. When 17XNL: 265BY5: 5 infects the mice, 265BY already accounts for 81% of the population at 12 days. Based on the data of host survival rate and protozoemia level in infection process, we can fully understand the survival competition and host immune response of two different virulence strains in mixed infection. The variation of population number is not simply equivalent to the simple superposition of the two strains when they are infected alone, regardless of whether the virulence or the proportion of mixed strains are different. For example, the initial infection ratios of 17XNL: 265BY were 1: 9 and 9: 1, respectively. The former was inhibited by 17XXL at the 14th day to 98 percent, while the latter by 265BY was inhibited to the extent of 60 percent at the 14th day, although it is not clear whether this dynamic change is related to the host immune system. However, this study laid a foundation for further exploring the changes of cytokines in host immune response and elucidating the regulatory mechanism of dynamic balance between protective and pathological immune responses. In this paper, a blood sample from a naturally infected Plasmodium vivax patient in a hospital in Xiamen was used to extract genomic DNA, amplify the sequence of cox 鈪，

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