The Analysis of Live-Attenuated Piscirickettsia salmonis Vaccine Reveals the Short-Term Upregulation of Innate and Adaptive Immune Genes in Atlantic Salmon (Salmo salar): An In Situ Open-Sea Cages Study.

Deborah Vargas,Eva Vallejos-Vidal,Sebastián Reyes-Cerpa,Aarón Oyarzún-Arrau,Ana María Sandino,Felipe E Reyes-López,Mónica Imarai,Claudio Acuña-Castillo

doi:10.3390/microorganisms9040703

Abstract

Piscirickettsia salmonis, the etiological agent of the Salmon Rickettsial Septicemia (SRS), is one the most serious health problems for the Chilean salmon industry. Typical antimicrobial strategies used against P. salmonis include antibiotics and vaccines, but these applications have largely failed. A few years ago, the first attenuated-live vaccine against SRS (ALPHA JECT LiVac® SRS vaccine) was released to the market. However, there is no data about the agents involved in the activation of the immune response induced under field conditions. Therefore, in this study we evaluated the expression profile of a set of gene markers related to innate and adaptive immunity in the context of a cellular response in Atlantic salmon (Salmo salar) reared under productive farm conditions and immunized with a live-attenuated vaccine against P. salmonis. We analyzed the expression at zero, 5-, 15- and 45-days post-vaccination (dpv). Our results reveal that the administration of the attenuated live SRS LiVac vaccine induces a short-term upregulation of the cellular-mediated immune response at 5 dpv modulated by the upregulation of ifnα, ifnγ, and the cd4 and cd8α T cell surface markers. In addition, we also registered the upregulation of il-10 and tgfβ. Altogether, the results suggest that a balanced activation of the immune response took place only at early times post-vaccination (5 dpv). The scope of this short-term upregulation of the cellular-mediated immune response against a natural outbreak in fish subjected to productive farm conditions deserves further research.

Highlights

IntroductionThe contribution of world aquaculture to world fish production has constantly increased, reaching 46.0% in 2016–2018, valued at USD 250 billion
In 2018, about 88% of the 179 million tons of total fish production was utilized for direct human consumption, a share that has increased significantly in recent decades.The contribution of world aquaculture to world fish production has constantly increased, reaching 46.0% in 2016–2018, valued at USD 250 billion
The strategy included the analysis of innate (complement component 3 (c3); interferon alpha) and adaptive genes related to T helper (Th) response (ifn gamma for T helper 1 (Th1); interleukin-10 for Th2), regulatory mechanisms, and immune cell surface markers

Summary

Introduction

The contribution of world aquaculture to world fish production has constantly increased, reaching 46.0% in 2016–2018, valued at USD 250 billion. Chile has seen sustained export revenue growth on the back of strong global demand for salmonids throughout the Americas, Europe and Asia and an increase in prices, reaching export revenues of USD 6.6 billion [1]. Fish may be exposed to several environmental and husbandry related stimuli that may have a potential noxious or stressful effect. All these factors have negative impacts on fish welfare, overall performance, and protective immune response, increasing the susceptibility to disease [3]

Methods

Results

Conclusion