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1.
Int J Mol Sci ; 25(12)2024 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-38928053

RESUMO

The innate immune response in Salmo salar, mediated by pattern recognition receptors (PRRs), is crucial for defending against pathogens. This study examined DDX41 protein functions as a cytosolic/nuclear sensor for cyclic dinucleotides, RNA, and DNA from invasive intracellular bacteria. The investigation determined the existence, conservation, and functional expression of the ddx41 gene in S. salar. In silico predictions and experimental validations identified a single ddx41 gene on chromosome 5 in S. salar, showing 83.92% homology with its human counterpart. Transcriptomic analysis in salmon head kidney confirmed gene transcriptional integrity. Proteomic identification through mass spectrometry characterized three unique peptides with 99.99% statistical confidence. Phylogenetic analysis demonstrated significant evolutionary conservation across species. Functional gene expression analysis in SHK-1 cells infected by Piscirickettsia salmonis and Renibacterium salmoninarum indicated significant upregulation of DDX41, correlated with increased proinflammatory cytokine levels and activation of irf3 and interferon signaling pathways. In vivo studies corroborated DDX41 activation in immune responses, particularly when S. salar was challenged with P. salmonis, underscoring its potential in enhancing disease resistance. This is the first study to identify the DDX41 pathway as a key component in S. salar innate immune response to invading pathogens, establishing a basis for future research in salmonid disease resistance.


Assuntos
Doenças dos Peixes , Imunidade Inata , Filogenia , Piscirickettsia , Infecções por Piscirickettsiaceae , Renibacterium , Salmo salar , Animais , Piscirickettsia/genética , Imunidade Inata/genética , Salmo salar/microbiologia , Salmo salar/genética , Salmo salar/imunologia , Doenças dos Peixes/microbiologia , Doenças dos Peixes/imunologia , Doenças dos Peixes/genética , Infecções por Piscirickettsiaceae/microbiologia , Infecções por Piscirickettsiaceae/imunologia , Infecções por Piscirickettsiaceae/genética , Infecções por Piscirickettsiaceae/veterinária , Renibacterium/genética , Renibacterium/imunologia , Proteínas de Peixes/genética , Proteínas de Peixes/metabolismo , Proteínas de Peixes/imunologia , RNA Helicases DEAD-box/genética , RNA Helicases DEAD-box/metabolismo , Evolução Molecular
2.
Front Immunol ; 14: 1187209, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37187753

RESUMO

Nutritional immunity regulates the homeostasis of micronutrients such as iron, manganese, and zinc at the systemic and cellular levels, preventing the invading microorganisms from gaining access and thereby limiting their growth. Therefore, the objective of this study was to evaluate the activation of nutritional immunity in specimens of Atlantic salmon (Salmo salar) that are intraperitoneally stimulated with both live and inactivated Piscirickettsia salmonis. The study used liver tissue and blood/plasma samples on days 3, 7, and 14 post-injections (dpi) for the analysis. Genetic material (DNA) of P. salmonis was detected in the liver tissue of fish stimulated with both live and inactivated P. salmonis at 14 dpi. Additionally, the hematocrit percentage decreased at 3 and 7 dpi in fish stimulated with live P. salmonis, unchanged in fish challenged with inactivated P. salmonis. On the other hand, plasma iron content decreased during the experimental course in fish stimulated with both live and inactivated P. salmonis, although this decrease was statistically significant only at 3 dpi. Regarding the immune-nutritional markers such as tfr1, dmt1, and ireg1 were modulated in the two experimental conditions, compared to zip8, ft-h, and hamp, which were down-regulated in fish stimulated with live and inactivated P. salmonis during the course experimental. Finally, the intracellular iron content in the liver increased at 7 and 14 dpi in fish stimulated with live and inactivated P. salmonis, while the zinc content decreased at 14 dpi under both experimental conditions. However, stimulation with live and inactivated P. salmonis did not alter the manganese content in the fish. The results suggest that nutritional immunity does not distinguish between live and inactivated P. salmonis and elicits a similar immune response. Probably, this immune mechanism would be self-activated with the detection of PAMPs, instead of a sequestration and/or competition of micronutrients by the living microorganism.


Assuntos
Piscirickettsia , Salmo salar , Animais , Manganês , Piscirickettsia/genética , Ferro
3.
Microb Pathog ; 180: 106122, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37094756

RESUMO

Piscirickettsia salmonis is one of the main pathogens causing considerable economic losses in salmonid farming. The DNA gyrase of several pathogenic bacteria has been the target of choice for antibiotic design and discovery for years, due to its key function during DNA replication. In this study, we carried out a combined in silico and in vitro approach to antibiotic discovery targeting the GyrA subunit of Piscirickettsia salmonis. The in silico results of this work showed that flumequine (-6.6 kcal/mol), finafloxacin (-7.2 kcal/mol), rosoxacin (-6.6 kcal/mol), elvitegravir (-6.4 kcal/mol), sarafloxacin (-8.3 kcal/mol), orbifloxacin (-7.9 kcal/mol), and sparfloxacin (-7.2 kcal/mol) are docked with good affinities in the DNA binding domain of the Piscirickettsia salmonis GyrA subunit. In the in vitro inhibition assay, it was observed that most of these molecules inhibit the growth of Piscirickettsia salmonis, except for elvitegravir. We believe that this methodology could help to significantly reduce the time and cost of antibiotic discovery trials to combat Piscirickettsia salmonis within the salmonid farming industry.


Assuntos
Doenças dos Peixes , Piscirickettsia , Animais , Antibacterianos/farmacologia , Piscirickettsia/genética , DNA Girase/genética , Doenças dos Peixes/tratamento farmacológico , Doenças dos Peixes/microbiologia
4.
Fish Shellfish Immunol ; 125: 120-127, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35537671

RESUMO

The intensive salmon farming is associated with massive outbreaks of infections. The use of antibiotics for their prevention and control is related to damage to the environment and human health. Antimicrobial peptides (AMPs) have been proposed as an alternative to the use of antibiotics for their antimicrobial and immunomodulatory activities. However, one of the main challenges for its massive clinical application is the high production cost and the complexity of chemical synthesis. Thus, recombinant DNA technology offers a more sustainable, scalable, and profitable option. In the present study, using an AMPs function prediction methodology, we designed a chimeric peptide consisting of sequences derived from cathelicidin fused with the immunomodulatory peptide derived from flagellin. The designed peptide, CATH-FLA was produced by recombinant expression using an easy pre-purification system. The chimeric peptide was able to induce IL-1ß and IL-8 expression in Salmo salar head kidney leukocytes, and prevented Piscirickettsia salmonis-induced cytotoxicity in SHK-1 cells. These results suggest that pre-purification of a recombinant AMP-based chimeric peptide designed in silico allow obtaining a peptide with immunomodulatory activity in vitro. This could solve the main obstacle of AMPs for massive clinical applications.


Assuntos
Doenças dos Peixes , Piscirickettsia , Infecções por Piscirickettsiaceae , Salmo salar , Animais , Antibacterianos , Doenças dos Peixes/microbiologia , Doenças dos Peixes/prevenção & controle , Flagelina , Rim Cefálico , Piscirickettsia/genética , Infecções por Piscirickettsiaceae/veterinária , Salmão
5.
J Fish Dis ; 44(5): 495-504, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33455005

RESUMO

Piscirickettsia salmonis is the causative agent of Piscirickettsiosis, a systemic disease generating high mortality rates in farmed salmon cultures of southern Chile. Proteolytic enzymes are important virulence factors since they play a key role in bacterial invasion and proliferation within the host. Bacteria growing in muscle tissues are known to secrete proteases, but no proteolytic enzymes have been described in P. salmonis to date. A battery of putative protease genes was found in the genomes and available strains of P. salmonis by bioinformatics analyses, and their identity was established through comparison with protease genes in databases. The transcript levels of five candidate genes were analysed by in vitro infection and qPCR. All strains were found to generate protease activity to varying degrees, and this was significantly increased when bacteria infected a salmon cell line. Gene expression of several types of proteases was also evidenced, with the highest levels corresponding to the type 1 secretion system (T1SS), which is also involved in the transport of haemolysin A, although transcripts with significant levels of peptidase M4 (thermolysin) and CLP protease were also found.


Assuntos
Doenças dos Peixes/microbiologia , Genes Bacterianos/genética , Piscirickettsia/genética , Infecções por Piscirickettsiaceae/veterinária , Salmo salar , Fatores de Virulência/genética , Animais , Infecções por Piscirickettsiaceae/microbiologia
6.
J Fish Dis ; 44(2): 181-190, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33006764

RESUMO

Piscirickettsiosis is a fish disease caused by the facultative intracellular bacterium, Piscirickettsia salmonis. Even though entry routes of P. salmonis in fish are not fully clear yet, the skin seems to be the main portal in some salmonid species. Despite the importance of fish mucous skin barrier in fighting waterborne pathogens, the interaction between salmonid skin mucus and the bacterium is unknown. This study seeks to determine the in vitro changes in the growth of two Chilean P. salmonis strains (LF-89-like and EM-90-like genotypes) and the type strain LF-89T under exposures to skin mucus from Salmo salar and Oncorhynchus mykiss, as well as changes in the cytotoxic effect of P. salmonis on the SHK-1 cells following exposures. The results suggest that the growth of three P. salmonis strains was not significantly negatively affected under exposures to skin mucus (adjusted at 100 µg total protein ml-1 ) of O. mykiss (69 ± 18 U lysozyme ml-1 ) and S. salar (48 ± 33 U lysozyme ml-1 ) over time. However, the cytotoxic effect of P. salmonis, pre-exposed to salmonid skin mucus, on the SHK-1 cell line was reliably identified only towards the end of the incubation period, suggesting that the mucus had a delaying effect on the cytotoxic response of the cell line to the bacterium. These results represent a baseline knowledge to open new avenues of research intended to understand how P. salmonis faces the fish mucous skin barrier.


Assuntos
Muco/imunologia , Piscirickettsia/crescimento & desenvolvimento , Infecções por Piscirickettsiaceae/veterinária , Animais , Linhagem Celular , Doenças dos Peixes/imunologia , Doenças dos Peixes/microbiologia , Genótipo , Muco/microbiologia , Oncorhynchus mykiss/imunologia , Piscirickettsia/genética , Infecções por Piscirickettsiaceae/imunologia , Infecções por Piscirickettsiaceae/microbiologia , Salmo salar/imunologia , Pele/imunologia , Pele/microbiologia
7.
FEMS Microbiol Lett ; 367(21)2020 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-33128546

RESUMO

Piscirickettsia salmonis is a facultative intracellular bacterium that generates piscirickettsiosis affecting salmonids in Chile. The bacterium has the adaptability to survive in the marine environment under multiple stressful conditions. In this sense, this work focused on the analysis of a gene battery associated with biofilm formation under different culture conditions and on the adaptability of this biofilm to different media. The results indicated that the strains LF-89, IBM-034 and IBM-040 were strong biofilm producers, evidencing adaptability to the media by increasing the amount of biofilm through successive growths. Transcript levels of six genes described in various bacteria and P. salmonis, considered to have metabolic functions, and playing a relevant role in biofilm formation, were analyzed to evaluate bacterial functionality in the biofilm. The genes mazE-mazF, implicated in biofilm and stress, were markedly overexpressed in the biofilm condition in the three strains. For its part, gene gltA, an indicator of metabolic activity and related to virulence inhibition in Salmonella typhimurium, also seems to restrain the pathogenesis process in P. salmonis by inhibiting the expression of the virulence-associated genes liso and tcf. Finally, the expression of the glnA gene suggests the use of glutamine as an essential element for the growth of the biofilm.


Assuntos
Biofilmes/crescimento & desenvolvimento , Doenças dos Peixes/microbiologia , Piscirickettsia/genética , Piscirickettsia/patogenicidade , Infecções por Piscirickettsiaceae/microbiologia , Fatores de Virulência/genética , Animais , Chile , Perfilação da Expressão Gênica , Genes Bacterianos/genética , Piscirickettsia/metabolismo , Salmonidae/microbiologia
8.
Sci Rep ; 10(1): 12224, 2020 07 22.
Artigo em Inglês | MEDLINE | ID: mdl-32699383

RESUMO

Piscirickettsia salmonis is the causative agent of piscirickettsiosis, a disease with high socio-economic impacts for Chilean salmonid aquaculture. The identification of major environmental reservoirs for P. salmonis has long been ignored. Most microbial life occurs in biofilms, with possible implications in disease outbreaks as pathogen seed banks. Herein, we report on an in vitro analysis of biofilm formation by P. salmonis Psal-103 (LF-89-like genotype) and Psal-104 (EM-90-like genotype), the aim of which was to gain new insights into the ecological role of biofilms using multiple approaches. The cytotoxic response of the salmon head kidney cell line to P. salmonis showed interisolate differences, depending on the source of the bacterial inoculum (biofilm or planktonic). Biofilm formation showed a variable-length lag-phase, which was associated with wider fluctuations in biofilm viability. Interisolate differences in the lag phase emerged regardless of the nutritional content of the medium, but both isolates formed mature biofilms from 288 h onwards. Psal-103 biofilms were sensitive to Atlantic salmon skin mucus during early formation, whereas Psal-104 biofilms were more tolerant. The ability of P. salmonis to form viable and mucus-tolerant biofilms on plastic surfaces in seawater represents a potentially important environmental risk for the persistence and dissemination of piscirickettsiosis.


Assuntos
Biofilmes/crescimento & desenvolvimento , Piscirickettsia/crescimento & desenvolvimento , Infecções por Piscirickettsiaceae/microbiologia , Animais , Aquicultura/métodos , Linhagem Celular , Chile , Doenças dos Peixes/microbiologia , Genótipo , Rim Cefálico/microbiologia , Piscirickettsia/genética , Salmo salar/microbiologia
9.
J Fish Dis ; 42(12): 1645-1655, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31591746

RESUMO

The aetiological agent of Piscirickettsiosis is Piscirickettsia salmonis, a Gram-negative intracellular pathogen, and high doses of antibiotics have regularly been employed to treat this infection. Seven florfenicol and/or oxytetracycline resistance genes (tet pump, tetE, Tclor/flor, Tbcr, TfloR, ompF and mdtN) were identified in strains by in silico genome analyses. Later, the number of single nucleotide polymorphisms (SNPs) and its relationship with the resistance to these antibiotics were identified and analysed, using the original LF-89 strain as reference. Trials to determine and compare the minimum inhibitory concentration (MIC) of oxytetracycline and florfenicol in each strain, as well as to quantify the gPCR transcripts levels in the selected genes, were performed. Therefore, variations in the resistance to both antibiotics were observed, where the strain with fewer SNPs showed the highest susceptibility. Consistently, the in silico 3D analyses of proteins encoded by the selected genes revealed structural changes, evident in the sequences with the highest number of SNPs. These results showed that the bacterial resistance to oxytetracycline was mainly linked to the presence of SNPs in relevant sites, antibiotic resistance genes and an OmpF porin, leading to important changes in the protein structure.


Assuntos
Resistência Microbiana a Medicamentos/genética , Genes Bacterianos , Piscirickettsia/genética , Polimorfismo de Nucleotídeo Único , Animais , Doenças dos Peixes/microbiologia , Testes de Sensibilidade Microbiana , Oxitetraciclina , Piscirickettsia/efeitos dos fármacos , Infecções por Piscirickettsiaceae/microbiologia , Infecções por Piscirickettsiaceae/veterinária , Tianfenicol/análogos & derivados
10.
Front Immunol ; 10: 434, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30941123

RESUMO

Piscirickettsia salmonis is a facultative intracellular pathogen and etiological agent of the systemic disease salmonid rickettsial septicemia. It has been suggested that P. salmonis is able to survive in host macrophages, localized within a vacuole like-compartment which prevents lysosomal degradation. However, the relevant aspects of the pathogenesis of P. salmonis as the host modulation that allow its intracellular survival have been poorly characterized. In this study, we evaluated the role of lysosomes in the response to P. salmonis infection in macrophage-enriched cell cultures established from Atlantic salmon head kidneys. Bacterial infection was confirmed using confocal microscopy. A gentamicin protection assay was performed to recover intracellular bacteria and the 16S rDNA copy number was quantified through quantitative polymerase chain reaction in order to determine the replication of P. salmonis within macrophages. Lysosomal activity in Atlantic salmon macrophage-enriched cell cultures infected with P. salmonis was evaluated by analyzing the lysosomal pH and proteolytic ability through confocal microscopy. The results showed that P. salmonis can survive ≥120 h in Atlantic salmon macrophage-enriched cell cultures, accompanied by an increase in the detection of the 16S rDNA copy number/cell. The latter finding suggests that P. salmonis also replicates in Atlantic salmon macrophage-enriched cell cultures. Moreover, this bacterial survival and replication appears to be favored by a perturbation of the lysosomal degradation system. We observed a modulation in the total number of lysosomes and lysosomal acidification following infection with P. salmonis. Collectively, the results of this study showed that infection of Atlantic salmon macrophages with P. salmonis induced limited lysosomal response which may be associated with host immune evasion mechanisms of P. salmonis that have not been previously reported.


Assuntos
Doenças dos Peixes/imunologia , Macrófagos/imunologia , Piscirickettsia , Infecções por Piscirickettsiaceae/imunologia , Salmo salar/imunologia , Animais , Células Cultivadas , DNA Ribossômico , Rim Cefálico/citologia , Rim Cefálico/imunologia , Lisossomos/imunologia , Macrófagos/microbiologia , Piscirickettsia/genética , Infecções por Piscirickettsiaceae/veterinária
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