Fatal progression of experimental visceral leishmaniasis is associated with intestinal parasitism and secondary infection by commensal bacteria, and is delayed by antibiotic prophylaxis
Fatal progression of experimental visceral leishmaniasis is associated with intestinal parasitism and secondary infection by commensal bacteria, and is delayed by antibiotic prophylaxis
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DOI：
10.1371/journal.ppat.1008456
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发表时间：
2020-04-01
期刊：
影响因子：
6.7
通讯作者：
Sacks, David L.
中科院分区：
文献类型：
--
作者：
Lewis, Michael D.;Paun, Andrea;Sacks, David L.
内脏利什曼病（VL）是一种潜在致命的被忽视的传染病，广泛分布于南亚、东非、南美洲和地中海地区。VL是由原生动物寄生虫杜氏利什曼原虫感染引起的。感染者可能保持无症状或进展，以不同的速度发展为VL疾病，影响肝脏，脾脏和血液。临床结果差异如此之大的原因尚不清楚。我们决定调查宿主的肠道微生物群是否可能是一个相关因素。我们用抗生素治疗小鼠和仓鼠，破坏它们的肠道微生物群，然后用L。donovani。在小鼠中未观察到影响，然而，经处理的仓鼠VL的发作和进展较慢，肝脏和脾脏的严重肿大程度较低，死亡率降低。这伴随着关键免疫反应因子水平的改变。我们还在仓鼠中发现了与肠道及其微生物群相关的症状性VL的新方面。具体地说，肠道组织本身被L. donovani和肝组织同时感染两种L.杜氏菌和源自肠道的革兰氏阴性菌。总的来说，我们的研究结果支持将抗菌治疗作为VL治疗策略的一部分。杜氏利什曼原虫导致内脏利什曼病（VL），这是典型的致命的不治疗。个体之间的疾病进展率、治疗反应和治疗后后遗症（特别是黑热病后皮肤利什曼病（PKDL））的发生率存在很大差异。然而，大多数感染者是无症状的携带者。仓鼠和小鼠通常分别用作致死性和非致死性VL的模型。宿主和寄生虫遗传学可能是重要的因素，但一般来说，人类和动物模型中异质性疾病表现的原因知之甚少。宿主微生物群已被确定为皮肤形式的利什曼病的一个因素，但尚未在VL中研究。我们通过在小鼠和仓鼠的饮用水中长期使用广谱抗生素来诱导肠道生态失调。在微生态小鼠中，疾病表现没有显著差异。相反，感染L. donovani延迟了体重减轻的发作和进展。与ABX处理的动物相比，一半的对照仓鼠具有快速进展表型，并且与未处理的对照组相比，9个月存活率显著提高（40% vs. 10%）。抗生素治疗的仓鼠也有显着不太严重的肝脾肿大，这是伴随着一个独特的细胞因子基因表达谱。保护作用不能用寄生虫负荷或血液学特征的差异来解释。我们进一步发现证据表明，肠-肝轴是仓鼠中致命VL进展的关键方面，包括肠道寄生虫、细菌移位至肝脏、软斑病和铁螯合，其中没有一个发生在非进展性小鼠VL中。从VL受影响的肝脏中培养出不同的细菌属，其中啮齿类细菌在ABX处理的仓鼠中特别缺乏，表明这种致病菌可能在促进疾病进展中发挥作用。结果为抗生素预防继发性细菌感染作为人类VL患者的辅助治疗提供了实验支持。
Author summaryVisceral leishmaniasis (VL) is a potentially fatal neglected infectious disease that is widespread in South Asia, East Africa, South America and the Mediterranean region. VL is caused by infections with the protozoan parasite Leishmania donovani. Infected people may remain asymptomatic or progress, at variable rates, to develop VL disease affecting the liver, spleen and blood. The reasons why clinical outcomes vary so much is not well understood. We decided to investigate whether a host's gut microbiota might be a relevant factor. We treated mice and hamsters with antibiotics to disrupt their gut microbiota and then infected them with L. donovani. No effect was observed in mice, however, treated hamsters had slower onset and progression of VL, less severe enlargement of the liver and spleen, and had a reduced mortality rate. This was accompanied by alterations in the levels of key immune response factors. We also found novel aspects of symptomatic VL in hamsters relating to the gut and its microbiota. Specifically, the gut tissues themselves were parasitized by L. donovani and liver tissues became co-infected with both L. donovani and Gram negative bacteria originating from the gut. Overall, our findings support the inclusion of anti-bacterial therapy as part of VL treatment strategies.Leishmania donovani causes visceral leishmaniasis (VL), which is typically fatal without treatment. There is substantial variation between individuals in rates of disease progression, response to treatment and incidence of post-treatment sequelae, specifically post-kala-azar dermal leishmaniasis (PKDL). Nevertheless, the majority of infected people are asymptomatic carriers. Hamsters and mice are commonly used as models of fatal and non-fatal VL, respectively. Host and parasite genetics are likely to be important factors, but in general the reasons for heterogeneous disease presentation in humans and animal models are poorly understood. Host microbiota has become established as a factor in cutaneous forms of leishmaniasis but this has not been studied in VL. We induced intestinal dysbiosis in mice and hamsters by long-term treatment with broad-spectrum antibiotics in their drinking water. There were no significant differences in disease presentation in dysbiotic mice. In contrast, dysbiotic hamsters infected with L. donovani had delayed onset and progression of weight loss. Half of control hamsters had a rapid progression phenotype compared with none of the ABX-treated animals and the nine-month survival rate was significantly improved compared to untreated controls (40% vs. 10%). Antibiotic-treated hamsters also had significantly less severe hepatosplenomegaly, which was accompanied by a distinct cytokine gene expression profile. The protective effect was not explained by differences in parasite loads or haematological profiles. We further found evidence that the gut-liver axis is a key aspect of fatal VL progression in hamsters, including intestinal parasitism, bacterial translocation to the liver, malakoplakia and iron sequestration, none of which occurred in non-progressing murine VL. Diverse bacterial genera were cultured from VL affected livers, of which Rodentibacter was specifically absent from ABX-treated hamsters, indicating this pathobiont may play a role in promoting disease progression. The results provide experimental support for antibiotic prophylaxis against secondary bacterial infections as an adjunct therapy in human VL patients.