Faculty of Science, University of Ostrava, 710 00, Ostrava, Czech Republic.
University of Stockholm, Stockholm, Sweden.
BMC Biol. 2023 Sep 12;21(1):191. doi: 10.1186/s12915-023-01687-y.
Trypanosomatids are parasitic flagellates well known because of some representatives infecting humans, domestic animals, and cultural plants. Many trypanosomatid species bear RNA viruses, which, in the case of human pathogens Leishmania spp., influence the course of the disease. One of the close relatives of leishmaniae, Leptomonas pyrrhocoris, has been previously shown to harbor viruses of the groups not documented in other trypanosomatids. At the same time, this species has a worldwide distribution and high prevalence in the natural populations of its cosmopolitan firebug host. It therefore represents an attractive model to study the diversity of RNA viruses.
We surveyed 106 axenic cultures of L. pyrrhocoris and found that 64 (60%) of these displayed 2-12 double-stranded RNA fragments. The analysis of next-generation sequencing data revealed four viral groups with seven species, of which up to five were simultaneously detected in a single trypanosomatid isolate. Only two of these species, a tombus-like virus and an Ostravirus, were earlier documented in L. pyrrhocoris. In addition, there were four new species of Leishbuviridae, the family encompassing trypanosomatid-specific viruses, and a new species of Qinviridae, the family previously known only from metatranscriptomes of invertebrates. Currently, this is the only qinvirus with an unambiguously determined host. Our phylogenetic inferences suggest reassortment in the tombus-like virus owing to the interaction of different trypanosomatid strains. Two of the new Leishbuviridae members branch early on the phylogenetic tree of this family and display intermediate stages of genomic segment reduction between insect Phenuiviridae and crown Leishbuviridae.
The unprecedented wide range of viruses in one protist species and the simultaneous presence of up to five viral species in a single Leptomonas pyrrhocoris isolate indicate the uniqueness of this flagellate. This is likely determined by the peculiarity of its firebug host, a highly abundant cosmopolitan species with several habits ensuring wide distribution and profuseness of L. pyrrhocoris, as well as its exposure to a wider spectrum of viruses compared to other trypanosomatids combined with a limited ability to transmit these viruses to its relatives. Thus, L. pyrrhocoris represents a suitable model to study the adoption of new viruses and their relationships with a protist host.
锥虫是一种寄生鞭毛生物，因其某些代表种感染人类、家畜和文化植物而广为人知。许多锥虫种携带有 RNA 病毒，这些病毒在人类病原体利什曼原虫属的情况下会影响疾病的进程。利什曼原虫的近亲之一，嗜人锥虫，先前已被证明携带其他锥虫中未记录的病毒群。同时，这种物种分布广泛，在其世界性的红火蚁宿主的自然种群中普遍存在。因此，它代表了研究 RNA 病毒多样性的一个有吸引力的模型。
我们调查了 106 株嗜人锥虫的无菌培养物，发现其中 64 株（60%）显示出 2-12 个双链 RNA 片段。下一代测序数据分析揭示了四个病毒群，有七个种，其中多达五个种同时在单个锥虫分离物中被检测到。在嗜人锥虫中，只有两种种，一种类似于 Tumbus 的病毒和一种 Ostravirus，以前有过记录。此外，还有四种属于 Leishbuviridae 科的新的利什曼病毒，该科包括锥虫特异性病毒，以及一种来自无脊椎动物宏转录组的新的 Qinviridae 科的病毒。目前，这是唯一一种有明确宿主的 qinvirus。我们的系统发育推断表明，由于不同锥虫株的相互作用，类似于 Tumbus 的病毒发生了重组。两个新的 Leishbuviridae 成员在该科的系统发育树中较早分支，并显示出昆虫 Phenuiviridae 和冠 Leishbuviridae 之间基因组片段减少的中间阶段。
一种原生动物物种中前所未有的广泛病毒范围，以及在单个嗜人锥虫分离物中同时存在多达五种病毒种，表明这种鞭毛虫的独特性。这可能是由其红火蚁宿主的特殊性决定的，红火蚁是一种高度丰富的世界性物种，具有多种习性，确保了其广泛的分布和丰富度，以及与其他锥虫相比，它暴露于更广泛的病毒谱，并结合了将这些病毒传播给其亲属的有限能力。因此，嗜人锥虫代表了一个合适的模型，可以研究新病毒的采用及其与原生动物宿主的关系。
