Uptake and survival of Leishmania amazonensis in Acanthamoeba: an adequate model organism?FIRST REVIEW ROUND - REVIEWERS' COMMENTSREVIEWERS' COMMENTSREVIEWERS' COMMENTS.

Abstract

Background: Research on Leishmania pathogenesis, as well as drug and vaccine discovery, primarily relies on complex mammalian models that raise ethical concerns. To overcome these limitations, we tested a simpler and more accessible experimental system. In this study, we examined the interaction between Leishmania amazonensis and Acanthamoeba, a widespread free-living protozoan that interacts with various microorganisms.

Objectives: To provide a deeper morphological and kinetic characterisation of the interaction between L. amazonensis and Acanthamoeba.

Methods: The parasite interaction was characterised using light microscopy, fluorescence microscopy, scanning electron microscopy (SEM), confocal microscopy, and live-cell imaging.

Findings: Co-culture was most optimal in RPMI medium at 26ºC. L. amazonensis promastigotes invaded Acanthamoeba trophozoites via their flagellum; trophozoites phagocytosed parasites through acanthopodia. Inside the amoeba, L. amazonensis became rounded and shortened, with no visible flagellum. These forms, isolated after 3 h of co-culture, differentiated back into promastigotes and were viable. The percentage of amoebas with L. amazonensis decreased over time.

Main conclusions: Acanthamoeba trophozoites can interact and clear out L. amazonensis. This model is unsuited for sustained infection studies necessary for drug screening. However, it could be an effective model for exploring cellular leishmanicidal mechanisms.