Abstract：
Leishmania major is responsible for zoonotic cutaneous leishmaniasis. Therapy is mainly based on the use of antimony-based drugs; however, treatment failures and illness relapses were reported. Although studies were developed to understand mechanisms of drug resistance, the interactions of resistant parasites with their reservoir hosts and vectors remain poorly understood. Here we compared the development of two L. major MON-25 trivalent antimony-resistant lines, selected by a stepwise in vitro Sb(III)-drug pressure, to their wild-type parent line in the natural vector Phlebotomus papatasi. The intensity of infection, parasite location and morphological forms were compared by microscopy. Parasite growth curves and IC50 values have been determined before and after the passage in Ph. papatasi. qPCR was used to assess the amplification rates of some antimony-resistance gene markers. In the digestive tract of sand flies, Sb(III)-resistant lines developed similar infection rates as the wild-type lines during the early-stage infections, but significant differences were observed during the late-stage of the infections. Thus, on day 7 p. i., resistant lines showed lower representation of heavy infections with colonization of the stomodeal valve and lower percentage of metacyclic promastigote forms in comparison to wild-type strains. Observed differences between both resistant lines suggest that the level of Sb(III)-resistance negatively correlates with the quality of the development in the vector. Nevertheless, both resistant lines developed mature infections with the presence of infective metacyclic forms in almost half of infected sandflies. The passage of parasites through the sand fly guts does not significantly influence their capacity to multiply in vitro. The IC50 values and molecular analysis of antimony-resistance genes showed that the resistant phenotype of Sb(III)-resistant parasites is maintained after passage through the sand fly. Sb(III)-resistant lines of L. major MON-25 were able to produce mature infections in Ph. papatasi suggesting a possible circulation in the field using this vector.
摘要：
主要利什曼原虫是人畜共患皮肤利什曼病的原因。治疗主要基于使用基于锑的药物；然而，报告了治疗失败和疾病复发。尽管有研究来了解耐药机制，抗性寄生虫与其水库宿主和载体的相互作用仍然知之甚少。在这里，我们比较了两种主要的MON-25三价锑抗性系的发展，通过逐步的体外Sb(III)-药物压力选择，天然载体Plebotomuspapatasi中的野生型亲本系。感染的强度，通过显微镜比较了寄生虫的位置和形态形式。寄生虫生长曲线和IC50值已在通过之前和之后确定。帕帕塔西.qPCR用于评估一些锑抗性基因标记的扩增速率。在沙蝇的消化道中，Sb（III）抗性品系在早期感染期间发展出与野生型品系相似的感染率，但在感染后期观察到显著差异。因此，在第7天下午，与野生型菌株相比，耐药品系显示出较低的重度感染与造口阀瓣定植的比例和较低的脂环前精子形式的比例。观察到的两个抗性品系之间的差异表明，Sb（III）抗性的水平与载体中的发育质量呈负相关。然而，几乎一半的受感染的沙蝇中，这两个耐药品系都出现了成熟的感染，并存在感染性元环形式。寄生虫通过沙蝇内脏并不会显着影响它们在体外繁殖的能力。抗锑基因的IC50值和分子分析表明，抗Sb（III）寄生虫在通过沙蝇后保持了抗性表型。主要的M.MON-25的Sb（III）抗性系能够在Ph中产生成熟的感染。papatasi建议使用此向量在野外可能的循环。
