Anisakiasis is an emerging zoonotic disease caused by nematodes of the genus Anisakis and characterized by gastrointestinal, ectopic or allergic reactions, following the ingestion of infected raw or undercooked fish or mollusks.
Despite its increasing public health awareness, most of the mechanisms of infection and clinical outcomes in humans are still unknown.
As parasitic nematodes are masterclass of host immune manipulation, establishing successful long-term infections, exosomal microvesicles carrying non-coding RNAs recently emerged as relevant players in intercellular signaling and parasite-host interactions. To disentangle the host-parasite crosstalk, we have recently identified molecules putatively involved in penetration of host tissues, by completing Anisakis larval and pharyngeal transcriptome analyses and we are currently analyzing larval and exosomal miRNAs content providing the first Anisakis miRNAs catalogue.
Few attempts are available so far for the in-vitro analysis of inflammatory response in a suitable model for anisakiasis.
The present project aims at evaluating the appropriate in-vitro model for studying Anisakis-human cells interactions and to study cellular response after the exposure to culture media incubated with infective Anisakis larvae, supposedly releasing extracellular vesicles as exosomes containing regulatory miRNAs. They play crucial roles in post-transcriptional regulation of target host genes, as reported for other nematodes of public health concern as Brugia malayi and Ascaris suum.
Analysis of cellular response will complement the ongoing analysis on Anisakis miRNAs, and such evidences may together shed light on the early mechanisms of host manipulation by anisakid nematodes and may help the development of early diagnostic biomarkers, as well as allergen-specific, preventive and therapeutic targets.
Parasitic nematodes show a great biological complexity and a great spectrum of interactions with the host, features that have impeded research progresses on anthelmintic discovery and on specific immunological screening test, as well as on control of infections.
This is furtherly complicated in anisakiasis, as humans are accidental hosts. Despite evolutive pathways shaping the Anisakis production of molecules interacting with hosts are not directly related to humans (as they develop in marine mammals), several pathogenetic mechanisms seem to be shared by phylogenetically related parasitic nematodes of mammals, and those related to miRNAs activity are even more broadly shared.
In fact, as for other intestinal human helminths, humans display several symptoms and clinical signs of gastrointestinal and allergic nature.
The assessment of studies for non-model nematodes and especially pathogens (not-free living organisms) is fundamental to clarify important biological issues, such as mechanisms that underlie infectivity. In fact, the use of predictive tools to explore the crosstalk between parasitic molecules and host genes could be relevant to depict general and specific mechanisms related to pathogenic behavior, and in a broad-spectrum may favor the development of new diagnostic and screening tools based on antigen-antibody study as well as it may facilitate drugs target discovery. At comparative level, information of this kind will aid in understanding of both conserved and divergent aspects of nematode biology in biomedical research.
The proposed in-vitro model based on Caco2 cell lines has not been widely used to infer the interface between the host tissues and intestinal parasites, with particular regard to gastro-intestinal nematodes. In this context the present study could open the way to a series of researches on a wide array of nematodes of human health concern (i.e. Ascaris, Trichuris). In particular, this model will be used to study the role of Anisakis-derived miRNAs on cellular inflammatory response unveiling the importance of parasite-human crosstalk.
Nowadays, the exosomes-associated miRNAs represent the way to transfer information between cells and organisms across all three kingdoms of life. Moreover, they act in the host-pathogen interaction by exerting immuno-modulating functions (Coakley et al 2015 Trends Parasitol 31:477).
Anisakiasis is worldwide distributed, with major impact in countries with a large consumption of raw fish. Anisakiasis usually presents with variable and unspecific gastrointestinal and/or allergic symptoms, which account for the high rate of misdiagnosed cases. Moreover, Anisakis exposure has been associated to occupational work risk to develop allergic diseases such as asthma and urticaria.
The potential impact of such kind of project in the detection of molecules to be potentially implemented in the development of new diagnostic tool for the early discovering of exposure is of great interest. In fact the available and routinely used diagnostic methods for the detection of allergy due to Anisakis (e.g. skin prick test) demonstrated to be poorly specific (somatic antigens largely share epitopes with other organisms, such as arthropods).
It should be pointed out that exosomes may also function as protein carrier and that the deep analysis of processes mediated by exosomes may provide the basis for the identification of potential targets for the improvement of highly specific diagnostic tools for parasite-driven allergies. It may result in the development of early diagnostic biomarkers, as well as allergen-specific, preventive and therapeutic.
Although the risk related to Anisakis infections is of raising concern, the knowledge on the specific mechanisms underlying host-parasite interactions and on the molecules directly involved in such interactions are still very scarce.
The importance of the present project is the development of an appropriate in-vitro model to study Anisakis-host interaction extending the knowledge in this field. Furthermore, this model can be widened to other intestinal parasites, highlighting the potentiality to create new knowledge in host-parasite relationship.