engleski

Worms under the microscope: how TEM and transcriptomics give us a holistic picture

The immense biodiversity of marine habitats and organisms of the visible size-scale, is nothing compared to the micro word of marine parasites and the myriad of their devious ways of interacting with the hosts. From simple and sacculous exogenous crustaceans with direct life cycle attached to the gills of 200 kg-large tuna swimming 70 km/h and larval hibernating nematodes secluded in the visceral cavity of a sardine dangerous for men, to the gonochoristic digeneans that stay firmly locked their whole adult life embedded in pairs in a tissue cysts, molecular communication between parasite and host remains the most fascinating key to understand their long- lasting evolution. Despite their diversity however, helminths elicit consistent immune responses characterised by hypereosinophilia, considerable plasma cell IgE production, mucous mastocytosis, and goblet cells hyperplasia, accompanied by the production of the cytokines interleukin-4 (IL-4), IL-5, IL-9, IL-10, IL-13, collectively known as T- helper 2 (Th2) immune response (Anthony et al. 2007 ; Moreau & Chauvin 2010). Interconnected with Th2 response, pro-inflammatory Th1 response is characterised by production of IL-2, IFN-γ, lymphotoxin (LT-α), TNF-α and other chemokines that stimulate phagocytosis, the oxidative burst, intracellular killing of microbes and antigen presentation to T cells. Collateral damage of activated immune response and the mechanical impact of the parasite reflects mostly on epithelial and connective host tissues, therefore its healing potential is important indicator of parasite pathogenicity. For example, while digeneans in tuna gills induced down-regulation of metabolic and signalling groups functionally associated with endocrine, digestive and nervous host system, and an immunity-related pathway consisting of complement and coagulation cascades bideractionally perturbed, anisakid nematodes show versatility in respect to the type of the organism they infect ; in fish as a paratenic hosts they induce fast tissue remodelling after migration, and in rat as a model of accidental host, they induce extreme inflammatory reaction. The possibility of complimenting in situ visualisation of the parasite by SEM, TEM and confocal microscopy, with analysis of target genes expressions, microarray and RNA sequencing, enables a deeper understanding of intricate patterns of host- parasite convivence, but still opens more questions than offers clear answers. Herein are presented some of the most interesting and novel cases of marine host-parasite systems where microscopy and transcriptomics helped in building up a more holistic picture. Acknowledgements: This research was supported by Croatian Science Fundation HRZZ, project Angel (Anisakis spp: Genomic Epidemiology, grant number 5576). References: 1. R.M. Anthony et al., Nature Rev. Immunol. 7 (2007) 975–987. 2. E. Moreau, A. Chauvin J. Biomed. Biotechnol. (2010) Article ID 428593.

parasites, SEM, TEM, gene expression

Financirano od HRZZ, #5576 Angel.