title: Leishmania major parasite stage-dependent host cell invasion and immune evasion.
abstract: Leishmania pathogenesis is primarily studied using the disease-inducing promastigote stage of Leishmania major. Despite many efforts, all attempts so far have failed to culture the disease-relevant multiplying amastigote stage of L. major. Here, we established a stably growing axenic L. major amastigote culture system that was characterized genetically, morphologically, and by stage-specific DsRed protein expression. We found parasite stage-specific disease development in resistant C57BL/6 mice. Human neutrophils, as first host cells for promastigotes, do not take up amastigotes. In human macrophages, we observed an amastigote-specific complement receptor 3-mediated, endocytotic entry mechanism, whereas promastigotes are taken up by complement receptor 1-mediated phagocytosis. Promastigote infection of macrophages induced the inflammatory mediators TNF, CCL3, and CCL4, whereas amastigote infection was silent and resulted in significantly increased parasite numbers: from 7.1 ± 1.4 (after 3 h) to 20.1 ± 7.9 parasites/cell (after 96 h). Our study identifies Leishmania stage-specific disease development, host cell preference, entry mechanism, and immune evasion. Since the amastigote stage is the disease-propagating form found in the infected mammalian host, the newly developed L. major axenic cultures will serve as an important tool in better understanding the amastigote-driven immune response in leishmaniasis.
authors: Division of Immunology, Federal Institute for Vaccines and Biomedicines, Paul-Ehrlich-Straße, Langen, Germany.
authors: Ulf Alexander
authors: UA
authors: Wenzel
authors: Elena
authors: E
authors: Bank
authors: Christian
authors: C
authors: Florian
authors: Sabine
authors: S
authors: Förster
authors: Nicole
authors: N
authors: Zimara
authors: Jochen
authors: J
authors: Steinacker
authors: Matthias
authors: M
authors: Klinger
authors: Norbert
authors: N
authors: Reiling
authors: Uwe
authors: U
authors: Ritter
authors: Ger
authors: G
authors: van Zandbergen
mesh_terms: D000818:Animals; D061245:Axenic Culture / Q000379:methods; D004705:Endocytosis / Q000276:immunology; D005260:Female; D015870:Gene Expression / Q000502:physiology; D006790:Host-Parasite Interactions / Q000276:immunology; D006801:Humans; D018320:Leishmania major / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D016773:Leishmaniasis, Cutaneous / Q000276:immunology* / Q000469:parasitology*; D008264:Macrophages / Q000276:immunology / Q000469:parasitology* / Q000648:ultrastructure; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008855:Microscopy, Electron, Scanning; D009504:Neutrophils / Q000276:immunology / Q000469:parasitology* / Q000648:ultrastructure; D010587:Phagocytosis / Q000276:immunology