The time course of cytoadhesion, immunoglobulin binding, rosette formation, and serum-induced agglutination of Plasmodium falciparum-infected erythrocytes.

Abstract

Abstract. We describe morphologic characteristics of acridine orange-stained Plasmodium falciparum-infected erythrocytes and the sequential expression of several adhesion phenomena. In particular, we have studied when the adhesive and antigenic modifications appear on the infected erythrocyte surface that mediate binding to C32 melanoma cells (cytoadherence) or to erythrocytes (rosette formation) during a complete 48-hr life cycle of the parasite. The C32 melanoma cell binding started at about 12 hr and was seen during the whole life cycle with a peak around 28 hr (650 infected erythrocytes/100 C32 melanoma cells). Rosettes started to appear and immunoglobulin was found bound to the parasitized red blood cell (PRBC) somewhat later (16-20 hr). These adhesive events culminated at the mid-trophozoite/schizont stage (24-36 hr) with rosette formation and an immunoglobulin binding rate of about 50%, which decreased to about half of the peak values at the end of the life cycle. Serum-induced agglutination of the infected erythrocytes was also most extensive at 24-36 hr, but agglutination was seen with all late stage parasites, i.e., both trophozoites and schizonts at 24-48 hr of age. Taken together, adhesion to C32 melanoma cells starts prior to that of rosette formation, immunoglobulin binding, or serum-induced agglutination.The incidence of Plasmodium falciparum malaria has been estimated to be 100 million new infections each year with 90% seen in tropical Africa.1 Estimates of malaria mortality vary from 1.5 to 2.7 million deaths annually affecting mainly children, with the two main causes of death being cerebral malaria and severe anemia.1-3 The current theories about the mechanisms leading to the development of cerebral and other forms of severe malaria are based on the fact that parasitized red blood cells (PRBC) sequester in the deep microvasculature of many organs and that excessive sequestration leads to vaso-occlusion, a histologic finding also seen at autopsy in the affected organs.4-9 Two forms of adhesive capacity have been identified that underlie the sequestration: cyto-adhesion to the vascular endothelium, 10-12 and rosette formation, the binding of uninfected red blood cells (RBC) to PRBC. [13][14][15][16] An in vitro correlation has been found between binding of PRBC to CD36-expressing cells and pulmonary disease, 17 and several studies have shown a strong association between the capacity in vitro to form rosettes and the severe forms of malaria. [18][19][20][21] Antibodies that block cytoadherence or disrupt rosettes seem important for development of the immunity that protects against severe disease. 18, 19 Taken together, it appears that the causation of severe malaria is at least partly due to various adhesive events that are modulated by anti-adhesive antibodies.In this study, two in vitro propagated strains of P. falciparum (FCR3S1 and TM284), selected either for rosette formation or cytoadherence to C32 melanoma cells, were investigated for their time course of adhesion. The parasites in culture...

Improved In Vitro Culture of Plasmodium falciparum Permits Establishment of Clinical Isolates with Preserved Multiplication, Invasion and Rosetting Phenotypes

“…This study further emphasizes the importance of human serum during the cultivation of P. falciparum isolates and laboratory strains to guarantee the display of the parasite’s adhesive phenotype and correct expression of PfEMP1. Various parasite lines depend on human immunoglobulins for the formation of rosettes [23], [34], [35], [36], [38], [44]; in addition, rosetting requires complementary serum factors [37]. Studies investigating the rosetting phenomena need to take into consideration that the display of the rosetting phenotype and expression of PfEMP1, and possibly other parasite ligands, can be dependent on the presence of human serum.…”

Taenia solium Oncosphere Adhesion to Intestinal Epithelial and Chinese Hamster Ovary Cells In Vitro

“…The number of oncospheres adhering to viable monolayer CHO-K1 cells was compared to the number of oncospheres adhering to fixed monolayer CHO-K1 cells after 48 h of cell culture. The fixed monolayer CHO cells were treated with 1% formaldehyde for 1 h and subsequently stored in PBS at 4°C until they were used (34). Viable and fixed monolayer cells were incubated with 2,500 T. solium activated oncospheres in binding medium at 37°C for 1.5 h. After incubation, the unbound oncospheres were rinsed three times with binding medium, and the oncospheres bound to the cells were fixed with 1% glutaraldehyde in PBS and stained with PAS.…”

Molecular Aspects of Severe Malaria

“…Why nonimmune Igs bind to the pRBC surface remains to be explained. In several subsequent investigations, it was found that a majority of rosetting parasites engage in Ig-binding activities, but some nonrosetting parasites also bind IgM and/or IgG (109,110,118). Some pRBCs bind only one class of Ig (IgM or IgG), while most bind both classes of Igs.…”