Bioinformatics Department, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, ul Pawinskiego 5a, 02-106 Warszawa, Poland.
Infect Genet Evol. 2012 Dec;12(8):1911-6. doi: 10.1016/j.meegid.2012.07.023. Epub 2012 Sep 8.
It was observed that pressure of host immune system leads to diversifying selection (which can be measured in terms of pN/pS ratio). In this research we checked whether Plasmodium falciparum proteins containing experimentally evident epitopes from the IEDB database are subject to diversifying selection. We also investigated which life stage of this parasite and which proteins are subject to the strongest immune pressure. To answer these questions we used information about experimentally evident epitopes from P. falciparum, that interact with human immune system and sequences of different isolates of P. falciparum obtained from PlasmoDB. We confirmed the expectations that proteins containing IEDB epitopes are subject to stronger diversifying selection which is evidenced by higher pN/pS ratio. A stage characterized by the highest average pN/pS ratio is that of the sporozoite. The greatest fraction of putative antigens is also present at this stage. We also found that the sporozoite stage is particularly interesting for further analysis as it potentially contains the highest number of unidentified epitopes.
研究表明,宿主免疫系统的压力会导致多样化选择(可以用 pN/pS 比值来衡量)。在这项研究中,我们检查了是否含有 IEDB 数据库中实验性明显表位的疟原虫蛋白受到多样化选择的影响。我们还研究了寄生虫的哪个生活阶段和哪些蛋白质受到最强的免疫压力。为了回答这些问题,我们使用了来自疟原虫的与人类免疫系统相互作用的实验性明显表位的信息,以及从 PlasmoDB 获得的不同疟原虫分离株的序列。我们证实了这样的预期,即含有 IEDB 表位的蛋白质受到更强的多样化选择,这表现在更高的 pN/pS 比值上。以最高平均 pN/pS 比值为特征的阶段是子孢子阶段。在这个阶段也存在最大比例的假定抗原。我们还发现,子孢子阶段特别值得进一步分析,因为它可能包含最高数量的未识别表位。