恶性疟原虫次黄嘌呤—鸟嘌呤—黄嘌呤磷酸核糖转移酶细胞免疫保护作用的研究

发布时间：2018-01-05 21:31

本文关键词：恶性疟原虫次黄嘌呤—鸟嘌呤—黄嘌呤磷酸核糖转移酶细胞免疫保护作用的研究　出处：《第二军医大学》2006年硕士论文　论文类型：学位论文

【摘要】：疟疾目前仍然是严重威胁人类健康的寄生虫病,由于疟原虫抗药性以及蚊媒抗杀虫剂的产生和扩散,使疟疾防治面临严重困难。因此,研制有效的疟疾疫苗已成为疟疾防治重要潜在的替代途径。研制疟疾红内期疫苗对降低疟疾的发病率和死亡率具有重要作用。针对红内期原虫免疫保护机制的研究,早期工作主要集中在体液免疫的作用。事实上红内期原虫确能诱导产生保护性抗体,这类抗体在体外能完全抑制疟原虫生长,许多动物试验结果也表明抗体在清除红内期原虫感染中发挥重要作用。由于红细胞表面缺乏MHC分子,因此细胞毒性T淋巴细胞(CTL)对红内期原虫不能发挥效应作用。但实验表明,在B细胞缺陷的小鼠模型中进行免疫攻击感染试验,结果显示免疫小鼠能产生对疟原虫攻击感染的免疫保护效力。尽管这种免疫力不能完全清除攻击感染的疟原虫,但可控制原虫密度在很低水平。显然,该免疫保护效力是由细胞免疫介导的。此外,CD4~+T细胞过继免疫小鼠也能对疟原虫攻击感染产生保护作用。这些结果表明在疟原虫的红内期免疫机制中,体液免疫和CD4~+T细胞介导的细胞免疫均发挥重要的作用。近年来,许多红内期疫苗候选抗原陆续得到鉴定,但这些抗原中绝大多数是针对保护性体液免疫的抗原。最近Makobongo等将所有红内期原虫抗原进行组分化并建立各组分的CD4~+T细胞品系,通过过继免疫和攻击感染试验确定了具有保护保护作用的T细胞品系,并初步鉴定疟原虫次黄嘌呤-鸟嘌呤-黄嘌呤-磷酸核糖转移酶(hypoxanthine guanine xanthine phosphoribosyl transferase,HGXPRT)为这种保护性CD4~+T细胞的靶抗原。HGXPRT是嘌呤核苷酸补救合成途径中的一个酶,可催化5-磷酸核糖焦磷酸(PRPP)与嘌呤反应生成嘌呤核苷酸。在哺乳动物体内,除有补救合成途径外,还有嘌呤核苷酸从头合成途径,但在疟原虫仅有补救合成途径,只能利用补救途径合成生命所必需的核苷酸,故而HGXPRT对于疟原虫便显得尤为重要,成为广泛关注的抗疟疾药物的靶标。因此有必要制备重组蛋白建立特异T细胞品系,以进一步确定其细胞免疫的免疫保护作用,并在此基础上鉴定其保护性T细胞表位。本实验室利用毕氏酵母系统表达并纯化了恶性疟原虫HGXPRT重组蛋白,
[Abstract]:Malaria is still a serious parasitic disease threatening human health. Malaria control is facing serious difficulties due to the resistance of malaria parasites and the emergence and spread of mosquito vectors. Therefore, the development of effective malaria vaccine has become an important potential alternative way for malaria control.
The development of malaria erythrocytic stage vaccine plays an important role in reducing malaria morbidity and mortality. The research on protective immunity mechanism of blood stage, early work focused on the role of humoral immunity. In fact erythrocytic protozoa can induce protective antibodies, the antibody can completely inhibit parasite growth in vitro and many animal experiments also showed that antibodies play an important role in eliminating parasite of blood stage. Due to the lack of red blood cell surface MHC molecules, so the cytotoxic T lymphocyte (CTL) of erythrocytic protozoa can not play effect. But the experiment showed that the immune attack experimental infection in a mouse model of B cell defects in the results show, immunized mice can produce immune protection effect on Plasmodium infection. Although this attack cannot completely eliminate infection immunity to Plasmodium, but can control the density of protozoa In a very low level. Obviously, is mediated by cell immunity the protective immunity. In addition, CD4~+T cell adoptive immunized mice can produce protective effects on parasite infection attacks. These results suggest that the immune mechanism in the Plasmodium falciparum erythrocytic stage, cell immunity Humoral immunity and CD4~+T cell mediated both play an important role.
In recent years, many erythrocytic stage vaccine candidate antigens have been identified, but most of these antigens is the protective humoral immune antigen. Recently Makobongo all erythrocytic protozoa antigen and establish CD4~+T cell differentiation group strain components, T cell lines with the protective effect is determined by the adoptive immune attack and infection test, and preliminary identification of Plasmodium hypoxanthine guanine xanthine phosphoribosyltransferase (hypoxanthine guanine xanthine phosphoribosyl transferase, HGXPRT) as the target antigen of.HGXPRT in the protective CD4~+T cell is an enzyme of purine salvage synthesis pathway, catalyzes the 5- phosphoribosyl pyrophosphate (PRPP) and the reaction of purine purine nucleotides. In mammals, in addition to a salvage pathway, and de novo purine nucleotide synthesis pathway, but in Plasmodium Only the salvage pathway, can only use the nucleotide salvage pathway for the synthesis of life, so it is very important to HGXPRT for Plasmodium, become a widespread concern of anti malaria drug targets. So it is necessary for the preparation of recombinant proteins to establish specific T cell lines, to further determine the immune protective effect of immune cells, and then based on the identification of the protective T cell epitope.
In this laboratory, the recombinant protein of Plasmodium falciparum HGXPRT was expressed and purified by the Pichia yeast system.

【学位授予单位】：第二军医大学
【学位级别】：硕士
【学位授予年份】：2006
【分类号】：R392

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