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BEI Inactivated Vaccine Induces Innate and Adaptive Responses and Elicits Partial Protection upon Reassortant Betanodavirus Infection in Senegalese Sole.

ABSTRACT: Nervous necrosis virus (NNV), the causative agent of viral encephalopathy and retinopathy (VER), is one of the most threatening viruses affecting marine and freshwater fish species worldwide. Senegalese sole is a promising fish species in Mediterranean aquaculture but also highly susceptible to NNV and VER outbreaks, that puts its farming at risk. The development of vaccines for aquaculture is one of best tools to prevent viral spread and sudden outbreaks, and virus inactivation is the simplest and most cost-effective method available. In this work, we have designed two inactivated vaccines based on the use of formalin or binary ethylenimine (BEI) to inactivate a reassortant NNV strain. After vaccination, the BEI-inactivated vaccine triggered the production of specific IgM-NNV antibodies and stimulated innate and adaptive immune responses at transcriptional level (rtp3, mx, mhcii and tcrb coding genes). Moreover, it partially improved survival after an NNV in vivo challenge, reducing the mid-term viral load and avoiding the down-regulation of immune response post-challenge. On the other hand, the formalin-inactivated vaccine improved the survival of fish upon infection without inducing the production of IgM-NNV antibodies and only stimulating the expression of herc4 and mhcii genes (in head-kidney and brain, respectively) during the vaccination period; this suggests that other immune-related pathways may be involved in the partial protection provoked. Although these vaccines against NNV showed encouraging results, further studies are needed to improve sole protection and to fully understand the underlying immune mechanism.

SUBMITTER: Valero Y

PROVIDER: S-EPMC8147993 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Betanodaviruses (VNNV) are the causative agents of the viral nervous necrosis, a disease that affects cultured Senegalese sole (Solea senegalensis). VNNV reassortant strains, combining genomic segments from the RGNNV and SJNNV genotypes, have previously been isolated from wild and farmed several fish species. The wild reassortant wSs160.03 isolated from sole has been proved to be more virulent for sole than the parental genotypes (RGNNV and SJNNV), causing 100% mortality. Mutations of wSs160.03 strain performed by reverse genetic, have allow to obtain a mutant reassortant strain (rSs160.03247+270) with mutations at amino acids 247 (serine to alanine) and 270 (serine to asparagine), which provoke a 40% decreased mortality. In the current study, the RNA-Seq technology has been used to compare the Senegalese sole transcriptomes in two organs (head-kidney and eye/brain) after infection with the wild reassortant strain and the mutant reassortant strain. A total of 633 genes were differentially expressed (DEGs) in animals infected with the wSs160.03 strain, whereas only 393 genes were differentially expressed in animals infected with the rSs160.03247+270 strain, indicating a 37.9% decrease in the number of DEGs after infection with the mutated reassortant strain. An inversion in the proportion of genes up/down-regulated in nervous tissue of these animals was also obtained for both reassortants. To understand the biological functions of identified DEGs involved in VNNV infection, a gene ontology (GO) enrichment analysis was performed with fold change > 1.5 (up- or down-regulated) and p-value < 0.05. Different profiles of GO were obtained in the subclasses biological process, cellular component, and molecular function for each reassortant strains. Regarding the immune response, genes coding for proteins acting as mediators of IFN type I expression (DHX58, IRF3, IRF7) and IFN-stimulated genes (ISG15, Mx, PKR, Gig1, ISG12, IFI44, IFIT-1, to name a few) were up-regulated in animals infected with the wild type reassortant, whereas no-differential expression of these genes was observed in animals infected with the mutant reassortant. The different transcriptomic profiles obtained could help to better understand VNNV pathogenesis in Senegalese sole, setting up the importance as virulence determinants of amino acids at positions 247 and 270 within the RNA2 segment.

Project description:BACKGROUND: Several miRNAs are known to control myogenesis in vertebrates. Some of them are specifically expressed in muscle while others have a broader tissue expression but are still involved in establishing the muscle phenotype. In teleosts, water temperature markedly affects embryonic development and larval growth. It has been previously shown that higher embryonic temperatures promoted faster development and increased size of Senegalese sole (Solea senegalensis) larvae relatively to a lower temperature. The role of miRNAs in thermal-plasticity of growth is hitherto unknown. Hence, we have used high-throughput SOLiD sequencing to determine potential changes in the miRNA transcriptome in Senegalese sole embryos that were incubated at 15°C or 21°C until hatching and then reared at a common temperature of 21°C. RESULTS: We have identified 320 conserved miRNAs in Senegalese sole, of which 48 had not been previously described in teleosts. mir-17a-5p, mir-26a, mir-130c, mir-206-3p, mir-181a-5p, mir-181a-3p and mir-199a-5p expression levels were further validated by RT- qPCR. The majority of miRNAs were dynamically expressed during early development, with peaks of expression at pre-metamorphosis or metamorphosis. Also, a higher incubation temperature (21°C) was associated with expression of some miRNAs positively related with growth (e.g., miR-17a, miR-181-5p and miR-206) during segmentation and at hatching. Target prediction revealed that these miRNAs may regulate myogenesis through MAPK and mTOR pathways. Expression of miRNAs involved in lipid metabolism and energy production (e.g., miR-122) also differed between temperatures. A miRNA that can potentially target calpain (miR-181-3p), and therefore negatively regulate myogenesis, was preferentially expressed during segmentation at 15°C compared to 21°C. CONCLUSIONS: Temperature has a strong influence on expression of miRNAs during embryonic and larval development in fish. Higher expression levels of miR-17a, miR-181-5p and miR-206-3p and down-regulation of miR-181a-3p at 21°C may promote myogenesis and are in agreement with previous studies in Senegalese sole, which reported enhanced growth at higher embryonic temperatures compared to 15°C. Moreover, miRNAs involved in lipid metabolism and energy production may also contribute to increased larval growth at 21°C compared to 15°C. Taken together, our data indicate that miRNAs may play a role in temperature-induced phenotypic plasticity of growth in teleosts.

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BEI Inactivated Vaccine Induces Innate and Adaptive Responses and Elicits Partial Protection upon Reassortant Betanodavirus Infection in Senegalese Sole.

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