Nervous Necrosis Virus-like Particle (VLP) Vaccine Stimulates European Sea Bass Innate and Adaptive Immune Responses and Induces Long-Term Protection against Disease.

Sofie Barsøe,Dagoberto Sepúlveda,Niels Lorenzen,Kerstin Skovgaard,Ansgar Stratmann,Niccolò Vendramin

doi:10.3390/pathogens10111477

Sofie Barsøe, Dagoberto Sepúlveda + Show 4 more

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https://doi.org/10.3390/pathogens10111477

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Journal: Pathogens	Publication Date: Nov 12, 2021
Citations: 10	License type: CC BY 4.0

Affiliation: Technical University of Denmark

Abstract

The rapidly increasing Mediterranean aquaculture production of European sea bass is compromised by outbreaks of viral nervous necrosis, which can be recurrent and detrimental. In this study, we evaluated the duration of protection and immune response in sea bass given a single dose of a virus-like particle (VLP)-based vaccine. Examinations included experimental challenge with nervous necrosis virus (NNV), serological assays for NNV-specific antibody reactivity, and immune gene expression analysis. VLP-vaccinated fish showed high and superior survival in challenge both 3 and 7.5 months (1800 and 4500 dd) post-vaccination (RPS 87 and 88, OR (surviving) = 16.5 and 31.5, respectively, p < 0.01). Although not providing sterile immunity, VLP vaccination seemed to control the viral infection, as indicated by low prevalence of virus in the VLP-vaccinated survivors. High titers of neutralizing and specific antibodies were produced in VLP-vaccinated fish and persisted for at least ~9 months post-vaccination as well as after challenge. However, failure of immune sera to protect recipient fish in a passive immunization trial suggested that other immune mechanisms were important for protection. Accordingly, gene expression analysis revealed that VLP-vaccination induced a mechanistically broad immune response including upregulation of both innate and adaptive humoral and cellular components (mx, isg12, mhc I, mhc II, igm, and igt). No clinical side effects of the VLP vaccination at either tissue or performance levels were observed. The results altogether suggested the VLP-based vaccine to be suitable for clinical testing under farming conditions.

Highlights

Introduction published maps and institutional affilThe European sea bass (Dicentrarchus labrax) is one of the main cultured species in the Mediterranean region, with increasing production every year [1]
The virus-like particle (VLP) were previously characterized [26],[26], sincesince this was production batch, the morphology was confirmed via transmission electron microscopy tion batch, the morphology was confirmed via transmission electron microscopy (Figure 1)
Each serum/coating combination was made in duplicate wells, and the results presented from sea bass hyperimmunized with either red-spotted grouper nervous necrosis virus (RGNNV) VLP, commercial vaccine, or phosphate-buffered saline (PBS)

Summary

Introduction

The European sea bass (Dicentrarchus labrax) is one of the main cultured species in the Mediterranean region, with increasing production every year [1]. The production cycle takes two to three years until the plate-sized sea bass are harvested. Sea bass are exposed to various pathogens. One of these is red-spotted grouper nervous necrosis virus (RGNNV), which causes viral nervous necrosis (VNN) or viral encephalo- and retinopathy. VNN may result in high mortalities— at the larval stage, where up to 100% mortality has been reported [2,3,4,5]—and is considered the main viral pathogen of concern for the sea bass production [6]. RGNNV belongs to the genus of Betanodavirus, which are small (~30–35 nm), icosahedral, nonenveloped, single-stranded, positive-sense RNA viruses with a bisegmented genome [7]

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