Uptake and survival of Leishmania amazonensis in Acanthamoeba castellanii: An infection organism model?

Leishmaniasis is a neglected tropical disease. Parasite strategies and the evaluation of drugs and vaccines are inferred from studies carried out using mouse models and macrophages. The development of model organisms with no ethical restrictions will contribute to our knowledge of leishmaniasis. Acanthamoeba castellanii, a free-living protozoan, is known to interact with various microorganisms. In this study, the interaction between the amoeba A. castellanii and the trypanosomatid Leishmania amazonensis was investigated by combining quantitative kinetics analysis, optical, fluorescence, electronic, confocal, and live video microcopy. We sought to standardize protocols for the co-culture; the optimal experimental conditions were: RPMI medium + 10% SFB at 26{degrees}C. L. amazonensis invades A. castellanii through its acanthopods, and the promastigotes interact with the trophozoites via their flagellum, which also occurs when parasites infect mammalian macrophages. The forms of L. amazonensis inside the amoeba become rounded and lose their flagellum; they are similar to amastigotes. These round forms were isolated from trophozoites after 3 h of co-culture and differentiated into promastigotes, demonstrating their viability inside amoeba. The percentage of amoebas with L. amazonensis was reduced overtime. Thus, considering that A. castellanii can clear Leishmania, this interaction could serve as an effective model of cellular leishmanicidal mechanisms.