title: Plasmodium falciparum: Rosettes do not protect merozoites from invasion-inhibitory antibodies.
abstract: Rosetting is a parasite adhesion phenotype associated with severe malaria in African children. Why parasites form rosettes is unknown, although enhanced invasion or immune evasion have been suggested as possible functions. Previous work showed that rosetting does not enhance parasite invasion under standard in vitro conditions. We hypothesised that rosetting might promote invasion in the presence of host invasion-inhibitory antibodies, by allowing merozoites direct entry into the erythrocytes in the rosette and so minimising exposure to plasma antibodies. We therefore investigated whether rosetting influences invasion in the presence of invasion-inhibitory antibodies to MSP-1. We found no difference in invasion rates between isogenic rosetting and non-rosetting lines from two parasite strains, R29 and TM284, in the presence of MSP-1 antibodies (P = 0.62 and P = 0.63, Student's t test, TM284 and R29, respectively). These results do not support the hypothesis that rosettes protect merozoites from inhibitory antibodies during invasion. The biological function of rosetting remains unknown.
authors.affiliation: Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Kings Buildings, EH9 3JT Edinburgh, UK.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Deans
authors.forename: J Alexandra
authors.initials: JA
authors.lastname: Rowe
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D004912:Erythrocytes / Q000276:immunology / Q000469:parasitology*; D006801:Humans; D016778:Malaria, Falciparum / Q000276:immunology*; D020066:Merozoite Surface Protein 1 / Q000276:immunology; D018512:Parasitemia / Q000276:immunology*; D010963:Plasmodium falciparum / Q000276:immunology*; D011817:Rabbits; D012397:Rosette Formation
chemical_list: D000913:Antibodies, Protozoan; D020066:Merozoite Surface Protein 1