ERYTHROCYTE ADHESION IN FALCIPARUM MALARIA

恶性疟原虫每年造成150万至270万人死亡。 脑型疟疾是恶性疟原虫感染的并发症，与脑血管中红细胞的隔离有关，并且是由于疟疾感染的红细胞（PE）粘附到微循环内衬的内皮细胞（EC）。 孕妇胎盘中PE的隔离导致并发症，包括胎儿出生体重低和死亡风险增加。 目前，没有一种疟疾疗法专门针对与隔离相关的粘附现象。 描述PE和EC表面的分子结构对于理解导致螯合的机制和开发抗粘附处理至关重要。 已知PE的增加是由于寄生虫诱导的红细胞膜蛋白带3的变化以及寄生虫编码蛋白的表面暴露。 虽然已经鉴定了对粘附至关重要的条带3的氨基酸序列，但尚不知道这种粘附素是如何形成的。 为了确定带3聚集和/或蛋白水解在诱导构象变化中的可能作用，将通过冷冻断裂显微镜和与粘附位点的电子显微免疫定位相协调，以及通过使用荧光光漂白恢复、偏振荧光耗尽和发光猝灭来评价带3在双层内的横向分布。 此外，为了对条带3中可能影响粘附序列分布的结构变化进行生物化学表征，将尝试分离条带3的截短形式和鉴定的裂解位点。 免疫沉淀，免疫印迹以及抗体结合的竞争性抑制将被用来确定在带3相关的和寄生虫编码的粘附素恶性疟原虫红细胞膜蛋白-1的共同的粘附基序;估计其对细胞粘附的贡献将被确定。 其他PE粘附素以及EC配体的微血管在人脑中，真皮和骨髓结合PE将被确定和其特征在于通过使用单克隆抗体，噬菌体展示和合成组合库技术，和肽亲和层析。 一旦确定，就有可能设计出能够抑制或逆转隔离的药物（即肽模拟物、小分子、抗体），从而为恶性疟疾患者提供更好和更安全的治疗方式。

Plasmodium falciparum contributes to 1.5-2.7 million deaths annually. Cerebral malaria, a complication of P. falciparum infections, is associated with sequestration of erythrocytes in the blood vessels of the brain and is due to the adhesion of malaria-infected erythrocytes (PE) to the endothelial cells (EC) lining the microcirculation. Sequestration of PE in the placenta of pregnant women leads to complications that include low fetal birth weight and an increased risk of death. At present none of the therapies for malaria specifically target the adhesive phenomena associated with sequestration. Describing the molecular architecture of the PE and EC surfaces is critical to understanding the mechanisms that lead to sequestration and for developing anti-adhesive treatments. It is known that increased adhesiveness of the PE is due to parasite-induced changes in the erythrocyte membrane protein, band 3, as well as the surface exposure of parasite-encoded proteins. Though the amino acid sequences of band 3 critical to adhesion have been identified it is not known how this adhesin is formed. To define the possible role of band 3 aggregation and/or proteolysis in inducing conformational change, the lateral distribution of band 3 within the bilayer will be evaluated by freeze fracture microscopy and coordinated with electron micrographic immunolocalization of adhesive sites, as well as by the use of fluorescence photobleaching recovery, polarized fluorescence depletion and luminescence quenching. In addition, to biochemically characterize the structural changes in band 3 that could influence the disposition of adhesive sequences, attempts will be made to isolate truncated forms of band 3 and cleavage sites identified. Immunoprecipitation, immunoblotting as well as competitive inhibition of antibody binding will be used to identify common adhesive motifs in the band 3-related and the parasite-encoded adhesin Plasmodium falciparum erythrocyte membrane protein-1; estimates of their contribution to cytoadherence will be determined. Other PE adhesins as well as EC ligands of microvessels in the human brain, dermis and bone marrow that bind PE will be identified and characterized through the use of monoclonal antibodies, phage display and synthetic combinatorial library technologies, and peptide affinity chromatography. Once identified, it should be possible to design drugs (i.e. peptidomimetics, small molecules, antibodies) that could inhibit or reverse sequestration thus allowing for better and safer therapeutic modalities for individuals suffering from falciparum malaria.