Targeted gene expression profiling in Leishmania braziliensis and Leishmania guyanensis parasites isolated from Brazilian patients with different antimonial treatment outcomes

Abstract

In Brazil, cutaneous leishmaniasis represents a serious public health problem, and chemotherapy is an important element of the clinical management of this disease. However, treatment efficacy is variable, a phenomenon that might be due to host and parasite (e.g., drug resistance) factors. To better understand the possible contribution of parasite factors to this phenomenon, we characterised 12 Leishmania braziliensis (LB) and 25 Leishmania guyanensis (LG) isolates collected from patients experiencing different antimonial treatment outcomes. For each isolate, promastigote cultures were grown in duplicate and were harvested at the late-log and stationary phases of growth. The RNA expression profiles of six genes encoding proteins with roles in antimony metabolism (AQP1, MRPA, GSH1, GSH2, TRYR and TDR1) were assessed by means of real-time quantitative PCR. Molecular data were compared to the clinical phenotypes. Within LB, we did not find statistically significant differences in the expression levels of the examined genes among isolates from patients with different treatment outcomes. In LG, GSH1 (encoding gamma-glutamylcysteine synthetase, gamma-GCS) was overexpressed in therapeutic failure isolates regardless of the growth curve phase. This finding reveals the predictive potential of promastigote expression curves for the prognosis of cutaneous leishmaniasis caused by LG in Brazil.

Heterogeneity of Molecular Resistance Patterns in Antimony-Resistant Field Isolates of Leishmania Species from the Western Mediterranean Area

“…Additionally, neither amplification nor overexpression of TRYR, HSP83, SKCRP, and MDR1 was observed, although these genes have displayed differential gene numbers or mRNA levels between sensitive and resistant parasites in other studies (19,45,46,49,50). These negative results could be due to the geographical particularities of mechanisms of resistance in western Mediterranean countries.…”

“…In fact, AQP1 is a membranous channel through which the trivalent antimony enters the parasite, and AQP1 overexpression is typically observed in susceptible isolates (11,45,47). However, a few cases of AQP1 overexpression in L. donovaniresistant clinical isolates have been reported (18,19). As the regulation of gene expression in Leishmania occurs primarily at the posttranscriptional level, the overexpression of AQP1 may be modulated at the protein level.…”

“…However, our molecular results correlated with the resistance phenotype observed in vitro for only 13 out of 24 (54%) resistant isolates. Several studies have defined a significant threshold as a 2-fold increase in RNA levels compared with the levels in a drug-sensitive reference strain (19,45,51). Applying such a threshold automatically increases the number of strains exhibiting gene overexpression, although it also introduces the risk of assigning biological significance to measurement variations associated with the technique.…”

“…Most of these studies were performed with in vitro-selected mutants of various Leishmania strains, mainly of the nonpatho-genic species Leishmania tarentolae (9,14,16,17). The few studies conducted on field isolates highlighted concordance with molecular patterns identified within in vitro-selected mutants; however, several discrepancies have also been reported (10,(18)(19)(20)(21)(22).…”

Nanoliposomal Buparvaquone Immunomodulates Leishmania infantum-Infected Macrophages and Is Highly Effective in a Murine Model

“…Other drugs used for treatment include amphotericin B, miltefosine, and pentamidine, but all of these current treatments have limitations. Therefore, novel, safe, and low-cost treatments are still needed (5).…”