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  • Innate immune-gene expression during experimental amyloodiniosis in European seabass (Dicentrarchus labrax).

Innate immune-gene expression during experimental amyloodiniosis in European seabass (Dicentrarchus labrax).

Veterinary immunology and immunopathology (2021-03-02)
Omkar Byadgi, Michela Massimo, Ron P Dirks, Alberto Pallavicini, James E Bron, Jacquie H Ireland, Donatella Volpatti, Marco Galeotti, Paola Beraldo
ABSTRACT

The ectoparasite protozoan Amyloodinium ocellatum (AO) is the causative agent of amyloodiniosis in European seabass (ESB, Dicentrarchus labrax). There is a lack of information about basic molecular immune response mechanisms of ESB during AO infestation. Therefore, to compare gene expression between experimental AO-infested ESB tissues and uninfested ESB tissues (gills and head kidney) RNA-seq was adopted. The RNA-seq revealed multiple differentially expressed genes (DEG), namely 679 upregulated genes and 360 downregulated genes in the gills, and 206 upregulated genes and 170 downregulated genes in head kidney. In gills, genes related to the immune system (perforin, CC1) and protein binding were upregulated. Several genes involved in IFN related pathways were upregulated in the head kidney. Subsequently, to validate the DEG from amyloodiniosis, 26 ESB (mean weight 14 g) per tank in triplicate were bath challenged for 2 h with AO (3.5 × 106/tank; 70 dinospores/mL) under controlled conditions (26-28 °C and 34‰ salinity). As a control group (non-infested), 26 ESB per tank in triplicate were also used. Changes in the expression of innate immune genes in gills and head kidney at 2, 3, 5, 7 and 23 dpi were analysed using real-time PCR. The results indicated that the expression of cytokines (CC1, IL-8) and antimicrobial peptide (Hep) were strongly stimulated and reached a peak at 5 dpi in the early infestation stage, followed by a gradual reduction in the recovery stage (23 dpi). Noticeably, the immunoglobulin (IgM) expression was higher at 23 dpi compared to 7 dpi. Furthermore, in-situ hybridization showed positive signals of CC1 mRNA in AO infested gills compared to the control group. Altogether, chemokines were involved in the immune process under AO infestation and this evidence allows a better understanding of the immune response in European seabass during amyloodiniosis.

MATERIALS
Product Number
Brand
Product Description

Roche
DIG Nucleic Acid Detection Kit, sufficient for 40 blots (10 cm x 10 cm each), kit of 1 (5 components), suitable for hybridization, suitable for Northern blotting
Sigma-Aldrich
Proteinase K from Tritirachium album, lyophilized powder, Molecular Biology, BioUltra, ≥30 units/mg protein
Sigma-Aldrich
Dextran sulfate sodium salt from Leuconostoc spp., Molecular Biology, average Mw >500,000 (dextran starting material), contains 0.5-2% phosphate buffer