title: Inhibition of dendritic cell maturation by malaria is dose dependent and does not require Plasmodium falciparum erythrocyte membrane protein 1.
abstract: Red blood cells infected with Plasmodium falciparum (iRBCs) have been shown to modulate maturation of human monocyte-derived dendritic cells (DCs), interfering with their ability to activate T cells. Interaction between Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) and CD36 expressed by DCs is the proposed mechanism, but we show here that DC modulation does not require CD36 binding, PfEMP1, or contact between DCs and infected RBCs and depends on the iRBC dose. iRBCs expressing a PfEMP1 variant that binds chondroitin sulfate A (CSA) but not CD36 were phagocytosed, inhibited lipopolysaccharide (LPS)-induced phenotypic maturation and cytokine secretion, and abrogated the ability of DCs to stimulate allogeneic T-cell proliferation. CD36- and CSA-binding iRBCs showed comparable inhibition. P. falciparum lines rendered deficient in PfEMP1 expression by targeted gene knockout or knockdown also inhibited LPS-induced phenotypic maturation, and separation of DCs and iRBCs in transwells showed that inhibition was not contact dependent. Inhibition was observed at an iRBC:DC ratio of 100:1 but not at a ratio of 10:1. High doses of iRBCs were associated with apoptosis of DCs, which was not activation induced. Lower doses of iRBCs stimulated DC maturation sufficient to activate autologous T-cell proliferation. In conclusion, modulation of DC maturation by P. falciparum is dose dependent and does not require interaction between PfEMP1 and CD36. Inhibition and apoptosis of DCs by high-dose iRBCs may or may not be physiological. However, our observation that low-dose iRBCs initiate functional DC maturation warrants reevaluation and further investigation of DC interactions with blood-stage P. falciparum.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia. elliott@wehi.edu.au
authors.forename: Salenna R
authors.initials: SR
authors.lastname: Elliott
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Spurck
authors.forename: Joelle M
authors.initials: JM
authors.lastname: Dodin
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Maier
authors.forename: Till S
authors.initials: TS
authors.lastname: Voss
authors.forename: Francisca
authors.initials: F
authors.lastname: Yosaatmadja
authors.forename: Paul D
authors.initials: PD
authors.lastname: Payne
authors.forename: Geoffrey I
authors.initials: GI
authors.lastname: McFadden
authors.forename: Alan F
authors.initials: AF
authors.lastname: Cowman
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Rogerson
authors.forename: Louis
authors.initials: L
authors.lastname: Schofield
authors.forename: Graham V
authors.initials: GV
authors.lastname: Brown
mesh_terms: D000818:Animals; D018955:CD36 Antigens / Q000378:metabolism*; D016466:CHO Cells; D002448:Cell Adhesion; D002454:Cell Differentiation / Q000276:immunology*; D002478:Cells, Cultured; D002809:Chondroitin Sulfates / Q000378:metabolism; D018920:Coculture Techniques; D006224:Cricetinae; D003412:Cricetulus; D003713:Dendritic Cells / Q000166:cytology* / Q000276:immunology* / Q000502:physiology; D004912:Erythrocytes / Q000469:parasitology* / Q000502:physiology; D006801:Humans; D008213:Lymphocyte Activation; D016778:Malaria, Falciparum / Q000276:immunology* / Q000469:parasitology; D010587:Phagocytosis; D010963:Plasmodium falciparum / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity*; D015800:Protozoan Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D018955:CD36 Antigens; D015800:Protozoan Proteins; C085731:erythrocyte membrane protein 1, Plasmodium falciparum; D002809:Chondroitin Sulfates