The Anisakis Transcriptome Provides a Resource for Fundamental and Applied Studies on Allergy-Causing Parasites

Abstract

BackgroundFood-borne nematodes of the genus Anisakis are responsible for a wide range of illnesses (= anisakiasis), from self-limiting gastrointestinal forms to severe systemic allergic reactions, which are often misdiagnosed and under-reported. In order to enhance and refine current diagnostic tools for anisakiasis, knowledge of the whole spectrum of parasite molecules transcribed and expressed by this parasite, including those acting as potential allergens, is necessary.Methodology/Principal FindingsIn this study, we employ high-throughput (Illumina) sequencing and bioinformatics to characterise the transcriptomes of two Anisakis species, A. simplex and A. pegreffii, and utilize this resource to compile lists of potential allergens from these parasites. A total of ~65,000,000 reads were generated from cDNA libraries for each species, and assembled into ~34,000 transcripts (= Unigenes); ~18,000 peptides were predicted from each cDNA library and classified based on homology searches, protein motifs and gene ontology and biological pathway mapping. Using comparative analyses with sequence data available in public databases, 36 (A. simplex) and 29 (A. pegreffii) putative allergens were identified, including sequences encoding ‘novel’ Anisakis allergenic proteins (i.e. cyclophilins and ABA-1 domain containing proteins).Conclusions/SignificanceThis study represents a first step towards providing the research community with a curated dataset to use as a molecular resource for future investigations of the biology of Anisakis, including molecules putatively acting as allergens, using functional genomics, proteomics and immunological tools. Ultimately, an improved knowledge of the biological functions of these molecules in the parasite, as well as of their immunogenic properties, will assist the development of comprehensive, reliable and robust diagnostic tools.

Comparative Transcriptomics Reveals Clues for Differences in Pathogenicity between Hysterothylacium aduncum, Anisakis simplex sensu stricto and Anisakis pegreffii

“…The transcriptome of this parasite was here compared with those A. pegreffii and A. simplex sensu stricto, and to the Anisakis genome available in Wormbase, as a further attempt to corroborate the potential pathogenic role of specific molecules enriched in the pharyngeal tissues [17] The de-novo assembly approach provided a similar number of transcripts for the three species and, after filtering for expression, the number of predicted genes was similar to those inferred from previous studies of Anisakis spp. and of other non-model species of parasitic nematodes [16,17,34]. As previously stated, a de-novo assembly approach was preferred to a genome-guided assembly based on the available draft genome sequence for A. simplex.…”

“…[14], according to the European Food Safety Authority, the latter is the only parasite in fishery products implicated in human sensitization and allergy [15]. Recently, high throughput transcriptomics has been applied to investigations of the potential mechanisms of pathogenicity of Anisakis larvae, with particular emphasis on molecules with potential roles in parasitic migrating through tissues and allergen sensitization [16][17][18][19]; nevertheless, the pathogenic potential of several marine parasitic nematodes other than Anisakis is still underinvestigated.…”

De novo transcriptome sequencing and analysis of Anisakis pegreffii (Nematoda: Anisakidae) third-stage and fourth stage larvae

“…Allergic reactions are one of the clinical symptoms caused by Anisakis nematodes infection in humans JOURNAL OF NEMATOLOGY Figure 1: GO analysis of DEGs in A. pegreffii transcriptomes (A. pegreffii L3 vs A. pegreffii L4). (Nieuwenhuizen and Lopata, 2013;Baird et al, 2016). Currently, 15 allergens in total have been described from A. simplex (s.s.) according to the WHO/IUIS Allergen Nomenclature Database (Pomés et al, 2018), but the exact number and characteristics of potential allergen molecules in anisakid nematodes are yet to be defined.…”

“…Currently, 134 parasitic or free-living nematodes genomes or transcriptomes are available in databases (http://www.wormbase.com, accessed on November 25, 2019) and the numbers will be increased. For anisakid nematodes, several transcriptomic analyses have been focused on A. simplex, a well-known cause of human anisakidosis or on comparative studies with a sibling species, A. pegreffii (Baird et al, 2016;Cavallero et al, 2018;Llorens et al, 2018), but not on A. pegreffii itself. In this study, we obtained transcriptomes of A. pegreffii L3 (APL3) and in vitro-induced L4 by RNA-seq and de novo assembly.…”

Gene expression profiles of antigenic proteins of third stage larvae of the zoonotic nematode Anisakis pegreffii in response to temperature conditions

“…infection [24,31,41,49,58]. Other putative allergens/molecules involved in the pathogenicity have recently been suggested by an RNAseq transcriptomic analysis [5,10,30]. Characterisation of transcriptomes by RNAseq analysis of affected tissues from rats infected with A. pegreffii L3 recently indicated regulated expression modulation of host immune-related genes in response to the larval infection [8,27,53].…”