ANÁLISE DO LÓCUS DE SENSIBILIDADE À MILTEFOSINA EM ISOLADOS CLÍNICOS DE Leishmania infantum ORIUNDOS DE PACIENTES EM UMA ÁREA DE ALTA ENDEMIA

Abstract

Chemotherapy constitutes the primary treatment strategy for visceral leishmaniasis (VL). However, first-line drugs, such as pentavalent antimonial (Glucantime®) and Amphotericin B (Amb), present high toxicity and require parenteral administration, which hinders patient therapy adherence. Miltefosine (MT) emerges as a promising alternative, although its efficacy varies among Leishmania species, especially Leishmania (L.) infantum. Previous studies demonstrate that the low response of this species to MT in Brazil is associated with natural drug resistance, related to the deletion of the MSL locus (Miltefosine Sensitivity Locus) in the parasite. Therefore, this study investigated the relationship between MSL locus deletion and in vitro miltefosine resistance in clinical isolates of Leishmania (L.) infantum from visceral leishmaniasis patients in an endemic area. Miltefosine susceptibility was tested in promastigote forms through the MTT assay and in intracellular amastigotes using an in vitro infection model in macrophages to count the infection rate after miltefosine treatment. Sequences were mapped, and read coverage in the MSL regions was estimated to determine gene deletions. Results demonstrated intraspecific variability in MT sensitivity in both parasite stages. IC50 in promastigote forms ranged from 5.84 to 25.17 μM, while intracellular amastigote forms were more sensitive, with EC50 between 1.56 and 7.36 μM. Moreover, among the 10 sequenced isolates, 4 presented MSL locus deletion. The association between MSL locus presence/absence and MT sensitivity showed a statistically significant difference in EC50 between parasites with and without deletion (p < 0.0001), indicating that MSL- parasites are more tolerant to Miltefosine. These findings reinforce that MSL locus deletion in Leishmania (L.) infantum genome is inferring in vitro response to miltefosine treatment. Thus, the presence or absence of this locus should be considered during treatment selection in endemic areas to avoid successive therapeutic failure cases.