Browsing by Author "Leal Acosta, Yeny"

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    Remodelación estructural y funcional en la respuesta transcriptómica de salmón del Atlántico frente a patógenos que afectan a la salmonicultura.
    (Universidad de Concepción, 2023) Leal Acosta, Yeny; Gallardo Escárate, Cristian
    Salmon farming, as one of the most important economic activities in Chile, faces constant challenges such as infectious diseases and the environmental impact generated by treatments. Among the main diseases affecting Atlantic salmon farming are caligidosis and rickettsial salmonid septicemia. The use of vaccines as an active immunostimulation strategy in Atlantic salmon is a promising solution to prevent diseases and reduce pollution. Understanding how Atlantic salmon responds at the molecular level to these stimuli or the presence of pathogens is crucial for developing effective management and control strategies. In this regard, RNA transcriptome sequencing technology (RNA-seq) has greatly contributed to understanding the molecular and functional changes that occur in an organism in the presence of stimulation, leading to a structural and functional remodeling of its transcriptomic response as a defense mechanism. In this context, this doctoral thesis aims to evaluate the transcriptomic, structural, and functional remodeling mechanisms of the response of Atlantic salmon to different immunological stimuli, whether pathogenic infections or vaccination processes. For this, in vitro and in vivo study models were used to evaluate the different potential mechanisms of remodeling the immune response of Atlantic salmon against different immunomodulatory stimuli. As a first stage, the transcriptomic response of the SHK-1 cell line stimulated with the recombinant protein Cr-cathepsin from Caligus rogercresseyi and the Atlantic salmon head kidney injected with the same protein were compared. The results of this study showed a differential transcriptomic profile of both study models, however, 24.15% of the transcriptomic response was shared, which was mainly associated with antigen stimulation. Enriched pathways related to the immune system and signal transduction were identified in both tissues, highlighting the MAPK signaling pathway, Toll-like receptor signaling, and melanogenesis, among others. In addition, expression analysis of lncRNAs revealed a specific transcription pattern for each model, where the main shared lncRNAs were found to be highly correlated with various transcripts involved in the immune response, iron homeostasis, the inflammatory response, and apoptosis, evidencing a possible functional remodeling through lncRNA caused by stimulation of the recombinant protein Cr-cathepsin. In turn, this study demonstrates that it is possible to use cell lines for the initial detection of antigens to develop vaccines against sea lice, reducing the time consumption associated with antigen selection. As a second stage of the study, the transcriptomic remodeling, based on alternative splicing (AS), of these two study models against infection with Psicirickettsia salmonis was explored. For this, SHK-1 cells were infected with the bacterium, and samples were taken at 0, 7 and 14 days after infection (dpi) for transcriptome sequencing. On the other hand, RNA-Seq data sets from Atlantic salmon head kidney infected with the same P. salmonis strain was used. For both study models, the highest number of differential alternative splicing (DAS) events was observed at 7 dpi. In SHK 1 cells infected with P. salmonis, a high presence of DAS genes related to nucleotide metabolism was observed, evidencing the competition of the bacteria for these micronutrients. Therefore, the cells would increase their production capacity to supply the nucleotide deficit, where AS processes would play a fundamental role. In contrast, the salmon head kidney exhibited many GO terms associated with the immune response, indicating the functional importance of AS in the functional remodeling of complex processes against bacterial infection. As a third stage of this study, the transcriptomic response in Atlantic salmon blood cells to vaccination and exposure to C. rogercresseyi and P. salmonis was evaluated. Four experimental groups were designed that included vaccination with the recombinant IpathÒ chimera and two commercial vaccines against P. salmonis: BlueGuard + Livac, BlueGuard + Livac + IpathÒ, IpathÒ and Control (adjuvanted PBS). Each group was infested with C. rogercresseyi, and after 25 dpi was infected with P. salmonis. Fish blood cells from each group were extracted at 12 dpi and used for transcriptome sequencing. In this work, the global transcriptomic patterns of Atlantic salmon blood cells from the four experimental groups showed differential expression levels. The experimental group vaccinated with IpathÒ showed a higher transcriptomic response compared to the commercial vaccines used. Notably, the annotations of the differentially expressed genes (DEGs) shared by the three experimental groups showed an enrichment of genes related to iron homeostasis and metabolism. Additionally, the behavior of different signaling pathways and their possible transcriptomic remodeling in each experimental group were analyzed, with the group vaccinated with IpathÒ being the most represented in all pathways, in terms of DEGs. The HIF-1 signaling pathway and ferroptosis were significantly activated, which could predict that vaccination with IpathÒ could be regulating hypoxia due to iron deficiency, or cell death due to ferroptosis, which could occur in Atlantic salmon during a C. rogercresseyi and P. salmonis exposition. The present study revealed transcriptomic remodeling in response to different immunostimulations, allowing us to delve into the molecular mechanisms involved in the immune response of Atlantic salmon. This approach explores in detail the changes in gene expression and AS that occur in different tissues, providing valuable information on the adaptive immune response and plasticity of the Atlantic salmon immune system. In addition, it highlights the importance of integrating different study models to obtain a comprehensive view of the immune response at different levels and contexts. This work provides valuable information to contribute to the development of disease management strategies in salmon farming, including the identification of molecular markers of immune response, the selection of resistant strains, and the design of more effective vaccines.
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