ANALYSES OF MECHANISMS FOR PLASMODIUM ADAPTATION TO THE HOST ERYTHROCYTES

为了获得开发疟疾疫苗和新的抗疟疾药物所需的基础知识，在分子和细胞水平上研究了疟疾寄生虫适应宿主红细胞的机制。研究结果如下：1.疟疾感染细胞代谢物的膜转运。(1)恶性疟原虫在人红细胞膜上生长良好，哇巴因可显著降低红细胞钾含量。(2)感染约氏疟原虫的细胞膜上出现小孔，导致细胞对2-脱氧-D-葡萄糖的摄取增加。穿过红细胞内寄生虫质膜的质子的电势与2-脱氧-D-葡萄糖的上行主动摄取相耦合。(3)约氏疟原虫线粒体具有内负膜电位。II.恶性疟原虫裂殖子表面抗原的多态性。(1)克隆了恶性疟原虫裂殖子表面主要抗原前体(P190)基因。对几个寄生虫分离株的p190基因进行了比较，发现了保守区和变异区。(2)序列变异不是多态的，但可分为两种类型。对14个分离株基因组DNA的Southern杂交分析表明，p190基因是二态等位基因。提示p190等位基因的基因内重组导致了该抗原的多态性。III.感染疟疾的红细胞钙代谢。(1)钙离子载体、钙拮抗剂和钙调素抑制剂对感染约氏疟原虫和恶性疟原虫的细胞钙代谢的干扰可导致其死亡。

To obtain fundamental knowledge necessary for developing malaria vaccines and new antimalarials, mechanisms for adaptation by malaria parasites to their host erythrocytes have been studied at the molecular and cellular levels. Results are as follows:I. Membrane transport of metabolites in malaria-infected cells. (1) Plasmodium falciparum grows well in human erythrocytes, whose potassium levels ae reduced greatly by treatment with ouabain. (2) An appearance of small pores in the membranes of P. yoelii-infected cells lead to increase in the uptake of 2-deoxy-D-glucose. An electrical potential of protons across the plasma membrane of intraerythrocytic parasites is coupled to an uphill active uptake of 2-deoxy-D-glucose. (3) The mitochondrion of P. yoelii has an inside negative membrane potential.II. Polymorphism of a surface antigen of P. falciparum merozoite. (1) The gene for a precursor (p190) to major merozoite surface antigens of P. falciparum has been cloned and sequenced. Comparisons of the p190 gene from several parasite isolates has revealed both conserved and variable regions. (2) Variations in the sequence are not widely polymorphic but fall into two types. Southern blot analyses of genomic DNA from 14 isolates has shown that the p190 gene is dimorphic alles. it is suggested that intragenic recombination of the p190 alles creates the antigen's polymorphism.III. Calcium metabolism of malaria-infected erythrocytes. (1) Disturbance of calcium metabolism of P. yoelii- and P. falciparum-infected cells by Ca^<2+> ionophore, calcium antagonists and calmodulin inhibitors results in the death of the parasites.