Abstract

BackgroundLarval stages of the sibling species of parasitic nematodes Anisakis simplex (sensu stricto) (s.s.) (AS) and Anisakis pegreffii (AP) are responsible for a fish-borne zoonosis, known as anisakiasis, that humans aquire via the ingestion of raw or undercooked infected fish or fish-based products. These two species differ in geographical distribution, genetic background and peculiar traits involved in pathogenicity. However, thus far little is known of key molecules potentially involved in host-parasite interactions. Here, high-throughput RNA-Seq and bioinformatics analyses of sequence data were applied to the characterization of the whole sets of transcripts expressed by infective larvae of AS and AP, as well as of their pharyngeal tissues, in a bid to identify transcripts potentially involved in tissue invasion and host-pathogen interplay.ResultsApproximately 34,000,000 single-end reads were generated from cDNA libraries for each species. Transcripts identified in AS and AP encoded 19,403 and 10,424 putative peptides, respectively, and were classified based on homology searches, protein motifs, gene ontology and biological pathway mapping. Differential gene expression analysis yielded 226 and 339 transcripts upregulated in the pharyngeal regions of AS and AP, respectively, compared with their corresponding whole-larvae datasets. These included proteolytic enzymes, molecules encoding anesthetics, inhibitors of primary hemostasis and virulence factors, anticoagulants and immunomodulatory peptides.ConclusionsThis work provides the scientific community with a list of key transcripts expressed by AS and AP pharyngeal tissues and corresponding annotation information which represents a ready-to-use resource for future functional studies of biological pathways specifically involved in host-parasite interplay.

Highlights

  • Larval stages of the sibling species of parasitic nematodes Anisakis simplex (s.s.) (AS) and Anisakis pegreffii (AP) are responsible for a fish-borne zoonosis, known as anisakiasis, that humans aquire via the ingestion of raw or undercooked infected fish or fish-based products

  • 31 larvae collected from the Atlantic mackerel were identified as AS, and 34 larvae collected from European anchovies and European pilchards were identified as AP following restriction analysis with HinfI [24]

  • The Anisakis simplex (s.s.) and A. pegreffii transcriptomes A total of 32,859,191 and 37,606,372,125 bp reads were generated for each whole larva (WL) and PX of AS, while 23,397,005 and 36,382,470 reads were generated from WL and PX of AP, respectively (Table 1)

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Summary

Introduction

Larval stages of the sibling species of parasitic nematodes Anisakis simplex (sensu stricto) (s.s.) (AS) and Anisakis pegreffii (AP) are responsible for a fish-borne zoonosis, known as anisakiasis, that humans aquire via the ingestion of raw or undercooked infected fish or fish-based products. These two species differ in geographical distribution, genetic background and peculiar traits involved in pathogenicity. Food-borne diseases are caused by a variety of chemical insults and pathogenic organisms, including parasites, with Anisakis spp. being the only fish-borne parasites able to trigger an allergic response in humans [1]. The occurrence of larval nematodes in fish fillets is of particular medical

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