Transcriptome profiling of plerocercoid and adult developmental stages of the neglected medical tapeworm Spirometra erinaceieuropaei
Graphical Abstract
Introduction
Diseases from parasitic tapeworms in humans cause major socioeconomic impacts (Wen et al, 2019). Despite their significance, many of them have been substantially neglected in terms of research and their control, especially for spirometrid tapeworms (Diphyllobothriidae: Spirometra) (Scholz et al, 2019). Within the genus Spirometra, the plerocercoid larva (sparganum) of S. erinaceieuropaei is the main aetiological agent of human sparganosis, which can cause local tissue damage, paralysis, blindness and even death (Kuchta et al, 2021). The incidence of sparganosis has been mostly reported in Eastern and Southeastern Asian countries, less frequently, cases of spirometrid cestode infection in humans and animals have also been reported in Africa, South America and Europe (Liu et al., 2015; Almeida et al, 2016; Kondzior et al, 2018; Czyżewska et al, 2019; Zhang et al, 2019; McHale et al, 2020; Bagrade et al, 2021). Human infection results mainly from ingesting uncooked frogs or snakes infected with plerocercoids, drinking water contaminated with copepods that have been infected with procercoids, or placing frogs or snakes flesh on open wounds (Zhang et al, 2020). In humans, the ingested sparganum can invade various organs including subcutaneous tissues, abdominal walls, eyes, brains, spinal cords, lungs, and breasts (Chotmongkol et al, 2021). Although several radiologic examinations and serodiagnostic tests have been introduced in diagnosis, and methods such as surgery and drugs (praziquantel, albendazole or mebendazole) are choices for treatment (Li et al, 2019), precision medicine for sparganosis still has a long way to go.
Understanding the intricacies of the biology of S. erinaceieuropaei and its interactions with hosts is central to developing new intervention strategies. However, little is known about the molecular basis of the developmental biology of S. erinaceieuropaei. Thus, addressing this knowledge gap is an urgent matter. Developments in next-generation transcriptome sequencing now provide an opportunity for the rapid and cost effective generation of genome-scale data (Pomaznoy et al, 2016; Kim et al, 2018; Bartolomé et al, 2021). In recent years, a large number of transcriptional datasets across a broad range of Cestoda have been deposited in GenBank (Hébert et al, 2016; Li et al, 2017; Huang et al, 2017; Basika et al, 2019; Zhang, 2019). For S. erinaceieuropaei, the first draft genome was sequenced (Bennett et al, 2014), and the expressed sequence tags (ESTs) were functionally analysed (Kim et al, 2014). Recently, phosphoproteomic analysis of S. erinaceieuropaei plerocercoid was performed to acquire knowledge of the protein phosphorylation networks of Spirometra tapeworms (Liu et al, 2020). These pioneering works provided a solid basis to explore the transcriptional profiles of S. erinaceieuropaei at different developmental stages.
In this study, we performed a comparative transcriptome analysis between larval and adult stages of S. erinaceieuropaei using a novel transcript quantification method of Salmon. Salmon is a tool for quantifying the expression of transcripts using RNA-seq data; that uses new algorithms to provide accurate expression estimates very quickly (Patro et al, 2017). More specifically, the following objectives were addressed: (1) the differential transcription between plerocercoid and adult stages of S. erinaceieuropaei was characterized using RNA-Seq (Illumina technology); and (2) key molecules inferred to be associated with the development, reproduction, feeding and survival of this neglected tapeworm were identified.
Section snippets
Ethical approval
This study was approved by the Life Science Ethics Committee of Zhengzhou University (Permit code. SYXK 2019-0737). The animals were handled in accordance with good animal practices required by the Animal Ethics Procedures and Guidelines of the People's Republic of China.
Collection and identification of S. erinaceieuropaei
The plerocercoid larvae were collected from infected frogs (Pelophylax nigromaculatus) from Zhengzhou city in central China using previously described methods (Zhang et al, 2017). To collect an adult worm, a single plerocercoid
Sequencing and annotation
Illumina high throughput sequencing produced 39,597,469 and 40,157,786 raw reads for plerocercoids and adults, respectively. After quality filtration, 35,219,744 (plerocercoid) and 38,730,324 (adult) high quality clean reads were obtained for assembly. The Q20 and Q30 of the transcriptome library were 100% and 98.85%, respectively. Based on the pooled clean reads, a total of 81,632 unigenes were produced from all samples (plerocercoids and adults) after removing short unigenes (< 200 nt), with
Discussion
Sparganosis caused by plerocercoid larvae of Spirometra spp. remains a neglected parasitic zoonosis . However, as a causative agent of human and animal sparganosis, little is known about the transcriptome of S. erinaceieuropaei. Hence, we sequenced and assembled the transcriptome of S. erinaceieuropaei. We did not analysis each developmental stage of the whole life cycle; rather, we analysed plerocercoids and adults, which are essential for the successful establishment of tapeworm infection in
Conclusions
In the present study, we provided the first report on a detailed transcriptome analysis of the plerocercoid and adult stages of S. erinaceieuropaei using RNA-seq. A large number of candidate DEGs involved in various biological processes in these two key developmental stages were identified. DEGs enriched in the plerocercoid stage were associated with parasite immunoevasion. In the adult stage, more upregulated DEGs were associated with metabolic activity. Moreover, the characterization of the
Authors’ contributions
XZ designed this study. SNL, XYS, WQC, JWY, JRL and PJ performed the experiments. XZ analysed the data with the assistance of SNL. XZ, JC and ZQW wrote the manuscript. All authors read and approved the final manuscript.
Consent for publication
Not applicable.
Supplementary information
Table S1 Primers of cox1 gene used in this study.
Table S2 Primer sets used in real time PCR analysis.
Table S3 Top 30 most abundant unigenes in the plerocercoid stage of S. erinaceieuropaei.
Table S4 Top 30 most abundant unigenes in the adult stage of S. erinaceieuropaei.
Fig. S1 The reads distribution across genomic regions in the map-based assembly.
Fig. S2 KEGG annotations of unigenes in S. erinaceieuropaei transcriptome. The top15 terms for each KEGG category are shown.
Fig. S3 Protein-protein
Declaration of Competing Interest
The authors declare that they have no competing interests.
Funding
This work was supported by National Natural Science Foundation of China (81971956 and U1704189) and Natural Science Foundation of Henan Province of China (212300410070).
Availability of data and materials
The data supporting the conclusions of this article are included within the article.
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