Malaria causes a half a million deaths annually. The parasite intraerythrocytic lifecycle in the human bloodstream is the major cause of morbidity and mortality. Apical organelles of merozoite stage parasites are involved in the invasion of erythrocytes. A limited number of apical organellar proteins have been identified and characterized for their roles during erythrocyte invasion or subsequent intraerythrocytic parasite development. To expand the repertoire of identified apical organellar proteins we generated a panel of monoclonal antibodies against Plasmodium falciparum schizont-rich parasites and screened the antibodies using immunofluorescence assays. Out of 164 hybridoma lines, 12 clones produced monoclonal antibodies yielding punctate immunofluorescence staining patterns in individual merozoites in late schizonts, suggesting recognition of merozoite apical organelles. Five of the monoclonal antibodies were used to immuno-affinity purify their target antigens and these antigens were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two known apical organelle protein complexes were identified, the high-molecular mass rhoptry protein complex (PfRhopH1/Clags, PfRhopH2, and PfRhopH3) and the low-molecular mass rhoptry protein complex (rhoptry-associated proteins complex, PfRAP1, and PfRAP2). A novel complex was additionally identified by immunoprecipitation, composed of rhoptry-associated membrane antigen (PfRAMA) and rhoptry neck protein 3 (PfRON3) of P. falciparum. We further identified a region spanning amino acids Q₂₂₁-E₄₈₁ within the PfRAMA that may associate with PfRON3 in immature schizonts. Further investigation will be required as to whether PfRAMA and PfRON3 interact directly or indirectly.

疟疾每年导致半百万人死亡。人血中的寄生虫红细胞生命周期是发病率和死亡率的主要原因。裂殖子阶段寄生虫的顶端细胞器参与红细胞的入侵。已经确定了数量有限的根尖细胞器蛋白，并对其在红细胞入侵或随后的红细胞内寄生虫发育过程中的作用进行了表征。为了扩大已鉴定的根尖细胞器蛋白的库，我们生成了一系列针对恶性疟原虫富含裂殖体的寄生虫，并使用免疫荧光测定法筛选抗体。在164个杂交瘤细胞系中，有12个克隆产生了单克隆抗体，可在裂殖体后期的各个裂殖子中产生点状免疫荧光染色模式，这表明对裂殖子顶端细胞器的识别。五个单克隆抗体用于免疫亲和纯化其靶抗原，并通过液相色谱-串联质谱（LC-MS / MS）鉴定这些抗原。鉴定出两种已知的顶端细胞器蛋白复合物，即高分子量的rhoptry蛋白复合物（PfRhopH1 / Clags，PfRhopH2和PfRhopH3）和低分子量的rhoptry蛋白复合物（rhoptry相关蛋白复合物，PfRAP1和PfRAP2）。通过免疫沉淀另外鉴定了一种新型复合物，恶性疟原虫。我们进一步在PfRAMA中确定了一个跨氨基酸Q ₂₂₁ -E ₄₈₁的区域，该区域可能与未成熟裂殖体中的PfRON3相关。将需要进一步研究PfRAMA和PfRON3是直接还是间接相互作用。