Immunostimulant Bathing Influences the Expression of Immune- and Metabolic-Related Genes in Atlantic Salmon Alevins.

Zuobing Zhang,Filipe Figueiredo,Jacques Godfroid,Stefano Peruzzi,Xiaoli Xu,Kim Præbel,Harald Kristoffersen,Roy Ambli Dalmo,Shripathi Bhat

doi:10.3390/biology10100980

Zuobing Zhang, Filipe Figueiredo + Show 7 more

Open Access

https://doi.org/10.3390/biology10100980

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Journal: Biology	Publication Date: Sep 29, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: Shanxi University, UiT The Arctic University of Norway

Abstract

Simple SummaryActivation of immune cells is bioenergetically expensive, requiring precise control of cellular metabolism. This applies also to innate immune cells. The current study shows that the immunostimulants, Astragalus, Hyaluronic acid, Imiquimod, and Poly I:C can modulate the expression of genes involved in the innate antiviral immune, as well as genes associated with metabolism, in the early life stages of Atlantic salmon.Disease resistance of fish larvae may be improved by bath treatment in water containing immunostimulants. Pattern recognition receptors, such as TLR3, TLR7, and MDA5, work as an “early warning” to induce intracellular signaling and facilitate an antiviral response. A single bath of newly hatched larvae, with Astragalus, upregulated the expression of IFNα, IFNc, ISG15, MDA5, PKR, STAT1, TLR3, and TLR7 immune genes, on day 4 post treatment. Similar patterns were observed for Hyaluronic acid and Poly I:C. Increased expression was observed for ISG15, MDA5, MX, STAT1, TLR3, TLR7, and RSAD2, on day 9 for Imiquimod. Metabolic gene expression was stimulated on day 1 after immunostimulant bath in ULK1, MYC, SLC2A1, HIF1A, MTOR, and SIX1, in Astragalus, Hyaluronic acid, and Imiquimod. Expression of NOS2 in Poly I:C was an average fourfold above that of control at the same timepoint. Throughout the remaining sampling days (2, 4, 9, 16, 32, and 45 days post immunostimulant bath), NOS2 and IL1B were consistently overexpressed. In conclusion, the immunostimulants induced antiviral gene responses, indicating that a single bath at an early life stage could enable a more robust antiviral defense in fish. Additionally, it was demonstrated, based on gene expression data, that cell metabolism was perturbed, where several metabolic genes were co-regulated with innate antiviral genes.

Highlights

Atlantic salmon (Salmo salar) is, by far, the most economically important species in European aquaculture, in Norway
Due to the importance of the innate immune system in antiviral response, it is hypothesized that stimulating disease resistance by upregulating the expression of key antiviral genes may be beneficial to afford increased protection during the delicate alevin stage
We found a positive correlation between mechanistic target of rapamycin (MTOR) and TLR3 and TLR7 expression, which is in line with prior knowledge

Summary

Introduction

Atlantic salmon (Salmo salar) is, by far, the most economically important species in European aquaculture, in Norway. Building knowledge on the innate immunity of nonmodel organisms such as Atlantic salmon can contribute towards a better understanding of the fish immune and physiological responses to pathogens. The yolk sac period (without feeding) in Atlantic salmon is relatively prolonged, as alevins start feeding at approximately 300 day degrees (dd) after hatching. Throughout this period, the fish larva must rely mostly on innate immunity to protect themselves from infection [3]

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