title: Comparative real-time kinetic analysis of human complement killing of Leishmania infantum promastigotes derived from axenic culture or from Phlebotomus perniciosus.
abstract: Although Leishmania metacyclic promastigotes are generally considered resistant to human complement, studies of in vitro-cultured axenic stationary promastigotes using serum concentrations that approximate physiological plasma conditions indicate complement sensitivity. Natural Leishmania infection is caused by sand fly-inoculated promastigotes, whose complement resistance has not been analyzed systematically. We compared Leishmania susceptibility to human complement in L. infantum promastigotes derived from in vitro cultures and from sand flies. Phlebotomus perniciosus sand flies were fed with axenic promastigotes, L. infantum-infected U-937 cells, or spleen cells from L. infantum-infected hamsters. On selected days post-feeding, flies were dissected and promastigotes isolated; in addition, axenic promastigotes were obtained from culture at equivalent days of growth. In near-physiological serum concentration and temperature conditions, measurement of real-time kinetics of propidium iodide uptake showed that approximately 90% of axenic- and sand fly-derived promastigotes were rapidly killed by complement. We found no substantial differences between promastigotes from axenic culture, those isolated from flies on different post-feeding days, or those generated in flies fed with distinct inocula. The results indicate that Leishmania susceptibility to human complement is independent of promastigote developmental stage in the sand fly mid-gut and in axenic culture.
authors.affiliation: Servicio de Inmunología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Ctra. Majadahonda-Pozuelo Km 1.5, Majadahonda, E-28220 Madrid, Spain.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Moreno
authors.forename: Ricardo
authors.initials: R
authors.lastname: Molina
authors.forename: Alfredo
authors.initials: A
authors.lastname: Toraño
authors.forename: Edurne
authors.initials: E
authors.lastname: Laurin
authors.forename: Esther
authors.initials: E
authors.lastname: García
authors.forename: Mercedes
authors.initials: M
authors.lastname: Domínguez
mesh_terms: D000818:Animals; D003165:Complement System Proteins / Q000276:immunology* / Q000494:pharmacology; D006224:Cricetinae; D003470:Culture Media; D004285:Dogs; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology*; D007700:Kinetics; D018314:Leishmania infantum / Q000187:drug effects* / Q000254:growth & development*; D007898:Leishmaniasis, Visceral / Q000276:immunology / Q000469:parasitology; D008647:Mesocricetus; D010691:Phlebotomus / Q000469:parasitology*; D020298:U937 Cells
chemical_list: D003470:Culture Media; D003165:Complement System Proteins