DataSheet_1_Co-infection of Phlebotomus papatasi (Diptera: Psychodidae) gut bacteria with Leishmania major exacerbates the pathological responses of BALB/c mice.docx

Clinical features and severity of the leishmaniasis is extremely intricate and depend on several factors, especially sand fly-derived products. Bacteria in the sand fly’s gut are a perpetual companion of Leishmania parasites. However, consequences of the concomitance of these bacteria and Leishmania parasite outside the midgut environment have not been investigated in the infection process. Herein, a needle infection model was designed to mimic transmission by sand flies, to examine differences in the onset and progression of L. major infection initiated by inoculation with “low” or “high” doses of Enterobacter cloacae and Bacillus subtilis bacteria. The results showed an alteration in the local expression of pro- and anti-inflammatory cytokines in mice receiving different inoculations of bacteria. Simultaneous injection of two bacteria with Leishmania parasites in the low-dose group caused greater thickness of ear pinna and enhanced tissue chronic inflammatory cells, as well as resulted in multifold increase in the expression of IL-4 and IL-1β and a decrease in the iNOS expression, without changing the L. major burden. Despite advances in scientific breakthroughs, scant survey has investigated the interaction between micro and macro levels of organization of leishmaniasis that ranges from the cellular to macro ecosystem levels, giving rise to the spread and persistence of the disease in a region. Our findings provide new insight into using the potential of the vector-derived microbiota in modulating the vertebrate immune system for the benefit of the host or recommend the use of appropriate antibiotics along with antileishmanial medicines.

利什曼病（leishmaniasis）的临床特征与严重程度极为复杂，受多种因素调控，尤以白蛉（sand fly）来源的产物影响最为显著。白蛉肠道内的细菌是利什曼原虫（Leishmania parasite）的恒定伴随共生伙伴。然而，目前尚未有研究探讨这些细菌与利什曼原虫在中肠外环境中共存对感染进程的影响。本研究构建针具感染模型以模拟白蛉的传播过程，探究分别接种低剂量或高剂量阴沟肠杆菌（Enterobacter cloacae）、枯草芽孢杆菌（Bacillus subtilis）后，大型利什曼原虫（Leishmania major, L. major）感染的发病与进展差异。结果显示，接受不同细菌接种的小鼠体内，促炎与抗炎细胞因子的局部表达发生显著改变。低剂量组中，将两种细菌与利什曼原虫联合注射可导致小鼠耳郭厚度明显增加，组织内慢性炎症细胞浸润增强，同时使IL-4（白细胞介素4）、IL-1β（白细胞介素1β）的表达呈多倍上调，诱导型一氧化氮合酶（inducible nitric oxide synthase, iNOS）的表达下降，但未改变大型利什曼原虫的载量。尽管当前科学研究已取得诸多突破，但针对利什曼病从细胞层面到宏观生态系统层面的微观与宏观组织水平间的相互作用的相关研究仍十分匮乏，而这类相互作用正是促成该疾病在区域内传播与持续存在的关键因素。本研究结果为利用传播媒介来源菌群调节脊椎动物免疫系统以造福宿主提供了新的见解，同时也建议在抗利什曼病治疗中联合使用合适的抗生素。