Electron microscopy of the Plasmodium falciparum trophozoites and the tissues these have infected in severe tropical malaria

The paper provides the results of the comprehensive electron microscopic examination of the venous blood and internal organ tissue samples obtained when studying the imported case of tropical malaria. The study was aimed to assess the fine structure of the erythrocytic stages of Plasmodium falciparum and alterations of the affected tissues in severe tropical malaria. The venous blood, cerebral cortical tissue and myocardial samples were examined by light microscopy and electron (scanning and transmission) microscopy. Numerous Plasmodium falciparum trophozoites were found in blood. Multiple Maurer's clefts were found in the cytoplasm of the infected erythrocytes. Abnormal intercellular contacts between the infected and unaffected erythrocytes were revealed, which resulted in their adhesion and rosette formation (erythrocyte rosetting/e-rosetting). When studying cortical tissue and myocardial samples, fixation of the affected erythrocytes on the endothelium (erythrocyte adhesion) was noted in the capillary lumen. Rosetting and erythrocyte adhesion lead to capillary thrombosis, disruption of microcirculation and sequestration of tissues in vital organs (parasite sequestration). The identified morphological features of the pathogens causing tropical malaria and the affected tissues determine the parasites’ capability of changing properties of the infected erythrocytes’ cell membranes, which leads to formation of abnormal intercellular contacts and constitutes one of the main mechanisms underlying the Plasmodium falciparum virulence.

1. Venkatesan P. The 2023 WHO World malaria report. The Lancet Microbe. 2024.

2. Lee WC, Russell B, Rénia L. Evolving perspectives on rosetting in malaria. Trends in Parasitology. 2022; 38 (10): 882–9.

3. Abdi A, Yu L, Goulding D, Rono MK, Bejon P, Choudhary J, et al. Proteomic analysis of extracellular vesicles from a Plasmodium falciparum Kenyan clinical isolate defines a core parasite secretome. Wellcome open research. 2017; 2.

4. Heiber A, Kruse F, Pick C, Grüring C, Flemming S, Oberli A, et al. Identification of new PNEPs indicates a substantial non-PEXEL exportome and underpins common features in Plasmodium falciparum protein export. PLoS pathogens. 2013; 9 (8): e1003546.

5. McHugh E, Carmo OM, Blanch A, Looker O, Liu B, Tiash S, et al. Role of Plasmodium falciparum protein GEXP07 in Maurer’s cleft morphology, knob architecture, and P. falciparum EMP1 trafficking. MBio. 2020; 11 (2): 10–1128.

6. Yadavalli R, Peterson JW, Drazba JA, Sam-Yellowe TY. Trafficking and Association of Plasmodium falciparum MC-2TM with the Maurer’s Clefts. Pathogens. 2021; 10 (4): 431.

7. Ortolan LS, Avril M, Xue J, Seydel KB, Zheng Y, Smith JD. Plasmodium falciparum parasite lines expressing DC8 and Group A PfEMP1 bind to brain, intestinal, and kidney endothelial cells. Frontiers in Cellular and Infection Microbiology. 2022; 12: 813011.

8. Jensen AR, Adams Y, Hviid L. Cerebral Plasmodium falciparum malaria: The role of PfEMP1 in its pathogenesis and immunity, and PfEMP1‐based vaccines to prevent it. Immunological reviews. 2020; 293 (1): 230–52.

9. Juillerat A, Lewit-Bentley A, Guillotte M, Gangnard S, Hessel A, Baron B, et al. Structure of a Plasmodium falciparum PfEMP1 rosetting domain reveals a role for the N-terminal segment in heparin-mediated rosette inhibition. Proceedings of the National Academy of Sciences. 2011; 108 (13): 5243–8.

10. Mwenda MC, Fola AA, Ciubotariu II, Mulube C, Mambwe B, Kasaro R, et al. Performance evaluation of RDT, light microscopy, and PET-PCR for detecting Plasmodium falciparum malaria infections in the 2018 Zambia National Malaria Indicator Survey. Malaria Journal. 2021; 20: 1–10.

11. Soulard V, Bosson-Vanga H, Lorthiois A, Roucher C, Franetich JF, Zanghi G, et al. Plasmodium falciparum full life cycle and Plasmodium ovale liver stages in humanized mice. Nature communications. 2015; 6 (1): 1–9.

12. Liffner B, Diaz AKC, Blauwkamp J, Anaguano D, Frolich S, Muralidharan V, et al. Atlas of Plasmodium falciparum intraerythrocytic development using expansion microscopy. Elife. 2023; 12: RP88088.

13. Laboratornaja diagnostika maljarii i babeziozov: Metodicheskie ukazanija. M.: FBUZ «Federal'nyj centr gigieny i jepidemiologii» Rospotrebnadzora, 2015; 43 s. Russian.

14. Borovskaya MK, Kuznecova YeYe, Gorohova VG, Korjakina LB, Kurilskaya TE, Pivovarov YuI. Strukturno-funkcional'naja harakteristika membrany jeritrocita i ee izmenenija pri patologijah raznogo geneza. Acta Biomedica Scientifica. 2010; 3 (73): 334–54. Russian.

15. Melcher M, Muhle RA, Henrich PP, Kraemer SM, Avril M, Vigan-Womas I, et al. Identification of a role for the PfEMP1 semiconserved head structure in protein trafficking to the surface of Plasmodium falciparum infected red blood cells. Cellular microbiology. 2010; 12 (10): 1446–62.

16. Kilian N, Zhang Y, LaMonica L, Hooker G, Toomre D, Mamoun CB, et al. Palmitoylated Proteins in Plasmodium falciparum-Infected Erythrocytes: Investigation with Click Chemistry and Metabolic Labeling. BioEssays. 2020; 42 (6): 1900145.

17. McDonald J, Merrick CJ. DNA replication dynamics during erythrocytic schizogony in the malaria parasites Plasmodium falciparum and Plasmodium knowlesi. PLoS Pathogens. 2022; 18 (6): e1010595.

18. Ostera G, Tokumasu F, Oliveira F, Sa J, Furuya T, Teixeira C, Dvorak J. Plasmodium falciparum: food vacuole localization of nitric oxide-derived species in intraerythrocytic stages of the malaria parasite. Experimental parasitology. 2008; 120 (1): 29–38.

19. Mundwiler-Pachlatko E, Beck HP. Maurer's clefts, the enigma of Plasmodium falciparum. Proceedings of the National Academy of Sciences. 2013; 110 (50): 19987–94.

20. Nigra AD, Casale CH, Santander VS. Human erythrocytes: cytoskeleton and its origin. Cellular and Molecular Life Sciences. 2020; 77: 1681–94.

21. Avril M, Bernabeu M, Benjamin M, Brazier AJ, Smith JD. Interaction between endothelial protein C receptor and intercellular adhesion molecule 1 to mediate binding of Plasmodium falciparum-infected erythrocytes to endothelial cells. MBio. 2016; 7 (4): 10–1128.