In vitro effect of new formulations of amphotericin B on amastigote and promastigote forms of Leishmania infantum

The in vitro antileishmanial activities of various new amphotericin B (AMB) formulations were investigated, including microspheres of hydrophilic albumin with three AMB aggregation forms (monomeric, dimeric and multiaggregate) and the polymers of polylactic-co-glycolic acid, Resomer RG502 and RG503 with the multiaggregate AMB form. This in vitro study was performed on the extracellular promastigote form and the intracellular amastigote form of a canine strain of Leishmania infantum (UCM 20) using the infected J774 murine macrophage-like cell line. Albumin-encapsulated forms did not show any toxicity for murine cells and had lower median effective concentration (EC50) values (ca. 0.003 μg/mL) for L. infantum amastigotes than free formulations (0.03 μg/mL). In addition, the aggregation state of AMB had a notable effect on the antileishmanial activity of the drug. Results obtained in vitro point towards interest in monomeric AMB encapsulated in microspheres in the chemotherapeutic control of leishmaniasis.