Interferon Gamma Induces the Increase of Cell-Surface Markers (CD80/86, CD83 and MHC-II) in Splenocytes From Atlantic Salmon

Type II interferon gamma (IFNγ) is a pleiotropic cytokine capable of modulating the innate and adaptive immune responses which has been widely characterized in several teleost families. In fish, IFNγ stimulates the expression of cytokines and chemokines associated with the pro-inflammatory response and enhances the production of nitrogen and oxygen reactive species in phagocytic cells. This work studied the effect of IFNγ on the expression of cell-surface markers on splenocytes of Atlantic salmon (Salmo salar). In vitro results showed that subpopulations of mononuclear splenocytes cultured for 15 days were capable of increasing gene expression and protein availability of cell-surface markers such as CD80/86, CD83 and MHC II, after being stimulated with recombinant IFNγ. These results were observed for subpopulations with characteristics associated with monocytes (51%), and features that could be related to lymphocytes (46.3%). In addition, a decrease in the expression of zbtb46 was detected in IFNγ-stimulated splenocytes. Finally, the expression of IFNγ and cell-surface markers was assessed in Atlantic salmon under field conditions. In vivo results showed that the expression of ifnγ increased simultaneously with the up-regulation of cd80/86, cd83 and mhcii during a natural outbreak of Piscirickettsia salmonis. Overall, the results obtained in this study allow us to propose IFNγ as a candidate molecule to stimulate the phenotypic progression of a small population of immune cells, which will increase antigen presenting cells markers. Thereby, modulatory strategies using IFNγ may generate a robust and coordinated immune response in fish against pathogens that affect aquaculture.

Induction of foxp3 during the Crosstalk between Antigen Presenting Like-Cells MHCII+CD83+ and Splenocytes CD4+IgM- in Rainbow Trout

Simple Summary

In aquatic biological models, the communication between cells from the immune system remains poorly characterized. In this work, to determine the gene expression of master transcriptional factors that coordinate the polarization of T cells, co-cultures of rainbow trout splenocytes are analyzed after stimulation with Interferon-gamma and/or Piscirickettsia salmonis. The results showed an upregulation of foxp3 compared to the other transcriptional factors, suggesting a potential communication between cells in the spleen, which may induce a Treg phenotype.

Abstract

In fish, the spleen is one of the major immune organs in the animal, and the splenocytes could play a key role in the activation and modulation of the immune response, both innate and adaptive. However, the crosstalk between different types of immune cells in the spleen has been poorly understood. In this work, an in vitro strategy is carried out to obtain and characterize mononuclear splenocytes from rainbow trout, using biomarkers associated with lymphocytes (CD4 and IgM) and antigen-presenting cells (CD83 and MHC II). Using these splenocytes, co-cultures of 24 and 48 h are used to determine the gene expression of master transcriptional factors that coordinate the polarization of T cells (t-bet, gata3, and foxp3). The results show a proportional upregulation of foxp3 (compared to t-bet and gata3) in co-cultures (at 24 h) of IFNγ-induced splenocytes with and without stimulation of Piscirickettsia salmonis proteins. In addition, foxp3 upregulation was established in co-cultures with IFNγ-induced cells and in cells only stimulated previously with P. salmonis proteins at 48 h of co-culture. These results show a potential communication between antigen-presenting-like cells and lymphocyte in the spleen, which could be induced towards a Treg phenotype.

ICU outcomes and survival in patients with severe COVID-19 in the largest health care system in central Florida

Background

Observational studies have consistently described poor clinical outcomes and increased ICU mortality in patients with severe coronavirus disease 2019 (COVID-19) who require mechanical ventilation (MV). Our study describes the clinical characteristics and outcomes of patients with severe COVID-19 admitted to ICU in the largest health care system in the state of Florida, United States.

Methods

Retrospective cohort study of patients admitted to ICU due to severe COVID-19 in AdventHealth health system in Orlando, Florida from March 11^th until May 18th, 2020. Patients were characterized based on demographics, baseline comorbidities, severity of illness, medical management including experimental therapies, laboratory markers and ventilator parameters. Major clinical outcomes analyzed at the end of the study period were: hospital and ICU length of stay, MV-related mortality and overall hospital mortality of ICU patients.

Results

Out of total of 1283 patients with COVID-19, 131 (10.2%) met criteria for ICU admission (median age: 61 years [interquartile range (IQR), 49.5–71.5]; 35.1% female). Common comorbidities were hypertension (84; 64.1%), and diabetes (54; 41.2%). Of the 131 ICU patients, 109 (83.2%) required MV and 9 (6.9%) received ECMO. Lower positive end expiratory pressure (PEEP) were observed in survivors [9.2 (7.7–10.4)] vs non-survivors [10 (9.1–12.9] p = 0.004]. Compared to non-survivors, survivors had a longer MV length of stay (LOS) [14 (IQR 8–22) vs 8.5 (IQR 5–10.8) p< 0.001], Hospital LOS [21 (IQR 13–31) vs 10 (7–1) p< 0.001] and ICU LOS [14 (IQR 7–24) vs 9.5 (IQR 6–11), p < 0.001]. The overall hospital mortality and MV-related mortality were 19.8% and 23.8% respectively. After exclusion of hospitalized patients, the hospital and MV-related mortality rates were 21.6% and 26.5% respectively.

Conclusions

Our study demonstrates an important improvement in mortality of patients with severe COVID-19 who required ICU admission and MV in comparison to previous observational reports and emphasizes the importance of standard of care measures in the management of COVID-19.

Impact of down-stream processing on functional properties of yeasts and the implications on gut health of Atlantic salmon (Salmo salar)

Yeasts are becoming popular as novel ingredients in fish feeds because of their potential to support better growth and concomitantly ensure good fish health. Here, three species of yeasts (Cyberlindnera jadinii, Blastobotrys adeninivorans and Wickerhamomyces anomalus), grown on wood sugars and hydrolysates of chicken were subjected to two down-stream processes, either direct heat-inactivation or autolysis, and the feed potential of the resulting yeast preparations was assessed through a feeding trial with Atlantic salmon fry. Histological examination of distal intestine based on widening of lamina propria, showed that autolyzed W. anomalus was effective in alleviating mild intestinal enteritis, while only limited effects were observed for other yeasts. Our results showed that the functionality of yeast in counteracting intestinal enteritis in Atlantic salmon was dependent on both the type of yeast and the down-stream processing method, and demonstrated that C. jadinii and W. anomalus have promising effects on gut health of Atlantic salmon.

Comparison of Circulating Markers and Mucosal Immune Parameters from Skin and Distal Intestine of Atlantic Salmon in Two Models of Acute Stress

Ensuring salmon health and welfare is crucial to maximize production in recirculation aquaculture systems. Healthy and robust mucosal surfaces of the skin and intestine are essential to achieve this goal because they are the first immunological defenses and are constantly exposed to multistressor conditions, such as infectious diseases, suboptimal nutrition, and environmental and handling stress. In this work, Atlantic salmon, split from a single cohort, were subjected to acute hypoxia stress or 15-min crowding stress and observed over a 24-h recovery period. Samples were collected from fish at 0, 1, 3, 6, 12 and 24 h post-stress to analyze plasma-circulating markers of endocrine function (cortisol), oxidative stress (glutathione peroxidase) and immune function (interleukin 10 (IL-10), annexin A1). In addition, mucosal barrier function parameters were measured in the skin mucus (Muc-like protein and lysozyme) and distal intestine (simple folds, goblet cell size and goblet cell area). The results showed that both acute stress models induced increases of circulating cortisol in plasma (1 h post-stress), which then returned to baseline values (initial control) at 24 h post-stress. Moreover, the hypoxia stress was mostly related to increased oxidative stress and IL-10 production, whereas the crowding stress was associated with a higher production of Muc-like protein and lysozyme in the skin mucus. Interestingly, in the distal intestine, smaller goblet cells were detected immediately and one hour after post-hypoxia stress, which could be related to rapid release of the cellular content to protect this organ. Finally, the correlation of different markers in the hypoxic stress model showed that the circulating levels of cortisol and IL-10 were directly proportional, while the availability of Muc-like proteins was inversely proportional to the size of the goblet cells. On the other hand, in the crowding stress model, a proportional relationship was established between plasma cortisol levels and skin mucus lysozyme. Our results suggest key differences in energy partitioning between the two acute stress models and support the need for further investigation into the interplay of multistressor conditions and strategies to modulate immunological aspects of mucosal surfaces.

Size matters: Zebrafish (Danio rerio) as a model to study toxicity of nanoplastics from cells to the whole organism

The contamination of the aquatic environment by plastic nanoparticles is becoming a major concern due to their potential adverse effects in aquatic biota. Therefore, in-depth knowledge of their uptake, trafficking and effects at cellular and systemic levels is essential to understand their potential impacts for aquatic species. In this work, zebrafish (Danio rerio) was used as a model and our aims were: i) to determine the distribution, uptake, trafficking, degradation and genotoxicity of polystyrene (PS) NPs of different sizes in a zebrafish cell line; ii) to study PS NPs accumulation, migration of immune cells and genotoxicity in larvae exposed to PS NPs; and iii) to assess how PS NPs condition the survival of zebrafish larvae exposed to a pathogen and/or how they impact the resistance of an immunodeficient zebrafish. Our results revealed that the cellular distribution differed depending on the particle size: the 50 nm PS NPs were more homogeneously distributed in the cytoplasm and the 1 μM PS NPs more agglomerated. The main endocytic mechanisms for the uptake of NPs were dynamin-dependent internalization for the 50 nm NPs and phagocytosis for the 1 μm nanoparticles. In both cases, degradation in lysosomes was the main fate of the PS NPs, which generated alkalinisation and modified cathepsin genes expression. These effects at cellular level agree with the results in vivo, since lysosomal alkalization increases oxidative stress and vice versa. Nanoparticles mainly accumulated in the gut, where they triggered reactive oxygen species, decreased expression of the antioxidant gene catalase and induced migration of immune cells. Finally, although PS NPs did not induce mortality in wild-type larvae, immunodeficient and infected larvae had decreased survival upon exposure to PS NPs. This fact could be explained by the mechanical disruption and/or the oxidative damage caused by these NPs that increase their susceptibility to pathogens.

NK-lysin, dicentracin and hepcidin antimicrobial peptides in European sea bass. Ontogenetic development and modulation in juveniles by nodavirus

Antimicrobial peptides (AMPs) are considered to be amongst the most powerful tools for the fight against pathogens in fish, since they form part of the innate immune response, which is especially vital in eggs and early larval stages, when the immune system is developing. The fish responsible for a large part of the profits in Mediterranean aquaculture is European sea bass (Dicentrarchus labrax), a species greatly susceptible to nodavirus (NNV), especially in the larval and juvenile stages. In this work, polyclonal antibodies were developed and used to detect and quantify NK-lysin, dicentracin and hepcidin AMPs in European sea bass eggs and during larval development, as well as to evaluate their regulation in juvenile specimens upon NNV infection. Basal and detectable levels of all the AMPs studied were present in eggs, confirming the maternal transfer of peptides, which increased in one or two waves during larval development up to 69 days post-fertilization. After NNV infection, the mRNA of all the AMPs analysed was up-regulated five days after infection in most of the tissues, whilst peptide quantification of all three AMPs decreased in the brain, the target tissue for NNV, but increased in the head-kidney 5 days after infection. Further research should be carried out to ascertain the role of AMPs in fish innate immunity and to understand how NNV evades the immune response to be disseminated.

The immune response of the scallop Argopecten purpuratus is associated with changes in the host microbiota structure and diversity

All organisms live in close association with a variety of microorganisms called microbiota. Furthermore, several studies support a fundamental role of the microbiota on the host health and homeostasis. In this context, the aim of this work was to determine the structure and diversity of the microbiota associated with the scallop Argopecten purpuratus, and to assess changes in community composition and diversity during the host immune response. To do this, adult scallops were immune challenged and sampled after 24 and 48 h. Activation of the immune response was established by transcript overexpression of several scallop immune response genes in hemocytes and gills, and confirmed by protein detection of the antimicrobial peptide big defensin in gills of Vibrio-injected scallops at 24 h post-challenge. Then, the major bacterial community profile present in individual scallops was assessed by denaturing gradient gel electrophoresis (DGGE) of 16S rDNA genes and dendrogram analyses, which indicated a clear clade differentiation of the bacterial communities noticeable at 48 h post-challenge. Finally, the microbiota structure and diversity from pools of scallops were characterized using 16S deep amplicon sequencing. The results revealed an overall modulation of the microbiota abundance and diversity according to scallop immune status, allowing for prediction of some changes in the functional potential of the microbial community. Overall, the present study showed that changes in the structure and diversity of bacterial communities associated with the scallop A. purpuratus are detected after the activation of the host immune response. Now, the relevance of microbial balance disruption in the immune capacity of the scallop remains to be elucidated.

Fish Red Blood Cells Modulate Immune Genes in Response to Bacterial Inclusion Bodies Made of TNFα and a G-VHSV Fragment

Fish Red-Blood Cells (RBCs) are nucleated cells that can modulate the expression of different sets of genes in response to stimuli, playing an active role in the homeostasis of the fish immune system. Nowadays, vaccination is one of the main ways to control and prevent viral diseases in aquaculture and the development of novel vaccination approaches is a focal point in fish vaccinology. One of the strategies that has recently emerged is the use of nanostructured recombinant proteins. Nanostructured cytokines have already been shown to immunostimulate and protect fish against bacterial infections. To explore the role of RBCs in the immune response to two nanostructured recombinant proteins, TNFα and a G-VHSV protein fragment, we performed different in vitro and in vivo studies. We show for the first time that rainbow trout RBCs are able to endocytose nanostructured TNFα and G-VHSV protein fragment in vitro, despite not being phagocytic cells, and in response to nanostructured TNFα and G-VHSV fragment, the expression of different immune genes could be modulated.

Rainbow Trout Red Blood Cells Exposed to Viral Hemorrhagic Septicemia Virus Up-Regulate Antigen-Processing Mechanisms and MHC I&II, CD86, and CD83 Antigen-presenting Cell Markers

Nucleated teleost red blood cells (RBCs) are known to express molecules from the major histocompatibility complex and peptide-generating processes such as autophagy and proteasomes, but the role of RBCs in antigen presentation of viruses have not been studied yet. In this study, RBCs exposed ex vivo to viral hemorrhagic septicemia virus (VHSV) were evaluated by means of transcriptomic and proteomic approaches. Genes and proteins related to antigen presentation molecules, proteasome degradation, and autophagy were up-regulated. VHSV induced accumulation of ubiquitinated proteins in ex vivo VHSV-exposed RBCs and showed at the same time a decrease of proteasome activity. Furthermore, induction of autophagy was detected by evaluating LC3 protein levels. Sequestosome-1/p62 underwent degradation early after VHSV exposure, and it may be a link between ubiquitination and autophagy activation. Inhibition of autophagosome degradation with niclosamide resulted in intracellular detection of N protein of VHSV (NVHSV) and p62 accumulation. In addition, antigen presentation cell markers, such as major histocompatibility complex (MHC) class I & II, CD83, and CD86, increased at the transcriptional and translational level in rainbow trout RBCs exposed to VHSV. In summary, we show that nucleated rainbow trout RBCs can degrade VHSV while displaying an antigen-presenting cell (APC)-like profile.

IFIT5 Participates in the Antiviral Mechanisms of Rainbow Trout Red Blood Cells

Viral hemorrhagic septicemia virus (VHSV) infection appears to be halted in rainbow trout nucleated red blood cells (RBCs). Diverse mechanisms are thought to be related to the antiviral immune response of rainbow trout RBCs to VHSV. However, the specific rainbow trout RBC proteins that interact directly with VHSV are still unknown. In an attempt to identify VHSV-RBC protein interactions, we characterized the immunoprecipitated (IP) proteome of RBCs exposed to VHSV using an antibody against the N protein of VHSV. The IP proteomic characterization identified 31 proteins by mass spectrometry analysis. Among them, we identified interferon-induced protein with tetratricopeptide repeats 5 (IFIT5), a protein belonging to a family of proteins that are induced after the production of type I interferon. Importantly, IFIT5 has been implicated in the antiviral immune response. We confirmed the participation of IFIT5 in the rainbow trout RBC antiviral response by examining the expression profile of IFIT5 in RBCs after VHSV exposure at transcriptional and protein levels. We detected a correlation between the highest IFIT5 expression levels and the decline in VHSV replication at 6 h post-exposure. In addition, silencing ifit5 resulted in a significant increase in VHSV replication in RBCs. Moreover, an increase in VHSV replication was observed in RBCs when the IFIT5 RNA-binding pocket cavity was modulated by using a natural compound from the SuperNatural II database. We performed a proximity ligation assay and detected a significant increase in positive cells among VHSV-exposed RBCs compared to unexposed RBCs, indicating protein-protein colocalization between IFIT5 and the glycoprotein G of VHSV. In summary, these results suggest a possible role of IFIT5 in the antiviral response of RBCs against VHSV.

SAT-LB032 Young Adult LEW.1WR1 Rats Develop Increased Glucose Intolerance on a Moderately Increased Sucrose Diet

FAT10 is an ubiquitin-like protein and Type 1 Diabetes (T1D) susceptibility gene that may play a role in age-related inflammation, adiposity, and cancer risk. The LEW.1WR1(1WR1) rat overexpresses FAT10 and has higher fasting concentrations of blood insulin and triglyceride during the induction of T1D. FAT10 is hypothesized to play a role in the expression of adipogenic genes; however, it is unclear if overexpression of FAT10 directly affects insulin sensitivity and glucose metabolism. We hypothesize that young adult 1WR1 rats will have increased glucose intolerance due to the poor regulation of insulin secretion which over time leads to reduced insulin sensitivity and increased adiposity. To test this hypothesis, we monitored glucose and insulin tolerance by glucose (GTT) or insulin tolerance (ITT) test and weight gain throughout 12 weeks on high fat and high sucrose (HFD) or moderate sucrose (MS) diet. The LEW/ssNHsd (SsNHsd) rat serves as a control rat. All experiments contain seven rats per group. We observed that at four weeks, the HFD diet rat groups had increased but non-significant fasting blood glucose levels during an ITT (109 +/- 4 mg/dL 1WR1-MS; 113 +/- 5 mg/dL SsNHsd-MS; 132 +/- 6 mg/dL 1WR1 HFD; or 131 +/- 13 mg/dL SsNHsd-HFD.) At ten weeks, the 1WR1-MS rats were more glucose intolerant than the control SsNHsd-MS rat (311.7 +/- 64 mg/dL vs. 194 +/- 53 mg/dL; p=0.09.) We compared the eight week GTT of the 1WR1-MS rats to a GTT before starting the diets (zero weeks) and the thirty minute time points are significantly different for the 1WR1-MS after 8 weeks on the MS diet compared to both the 1WR1-MS and SsNHsd-MS prior to the MS diet ( 164 +/- 27 mg/dL zero weeks 1WR1; 167 +/- 26 mg/dL zero weeks SsNHsd; 311 +/-64 mg/dL eight weeks 1WR1-MS p< 0.0001). 1WR1 rats on both diets also gained weight at similar rates, yet the total abdominal fat mass of the 1WR1-MS rats was not increased compared to the SsNHsd-MS (17.43 +/- 3.48 g 1WR1-MS vs. 16.42 +/- 2.73 g SsNHsd-MS p=0.94 and 24.64 +/- 4.27 g 1WR1-HFD p=0.004) and 1WR1 rat epididymal fat was not significantly different between the two diets compared to the significant difference in SsNHsd rats groups (5.85+/-1.01 1WR1-MS vs. 7.27+/- 1.42 1WR1-HFD p=0.07; 4.63 +/- 0.81 vs. 6.77 +/- 0.65 p=0.0052.) This data suggests that metabolic shifts are occurring in the 1WR1 rat, due to either increased sucrose intake or aging. These shifts reflected the increased glucose intolerance after eight weeks and the changes in abdominal fat pads relative to body mass. This study lays the groundwork for characterizing how alterations in FAT10 increase metabolic dysfunction through aging, glucose metabolism, insulin secretion/signaling, and lipid metabolism/catabolism. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Stocking density induces differential expression of immune-related genes in skeletal muscle and head kidney of fine flounder (Paralichthys adspersus)

Immunity can be modulated by different internal and external factors, being stress one of the most important. However, the stress effects on the immunocompetence of the skeletal muscle has not been studied in detail in earlier vertebrates. Here, we examine the effect of chronic (4 and 7 weeks) crowding stress on the immunocompetence of skeletal muscle and head kidney in the fine flounder (Paralichthys adspersus). Corticosteroid receptor transcript levels and their target genes; pro-inflammatory cytokines, and Toll-, NOD-, and RIG-like receptors were quantified by qPCR. The results indicate that chronic stress down-regulates the expression of these genes in muscle, compromising skeletal muscle immunocompetence, while the expression of these genes is upregulated in head kidney after seven weeks of crowding stress. The data suggests that chronic stress modulates the expression of these immune-related genes in a tissue-specific manner.

NK-lysin from skin-secreted mucus of Atlantic salmon and its potential role in bacteriostatic activity

NK-lysin, despite being a direct effector of cytotoxic T and natural killer cells, is an antimicrobial peptide (AMP) with known antibacterial function in vertebrates and so in fish. Its presence has been described in different tissues of teleost fish. One of the strongest antimicrobial barriers in fish is skin-secreted mucus; however, this mucus has been found to contain only a small number of AMPs. The present study describes for the first time the constitutive expression of NK-lysin in Atlantic salmon (Salmo salar) mucus produced by the skin, recording the AMP at a higher concentration than in serum with greater bacteriostatic activity. Hepcidin may be involved to a greater extent in systemic responses since it was expressed to a higher degree in serum which was more potent for alternative complement and peroxidase activities.

Reproduction Immunity Trade-Off in a Mollusk: Hemocyte Energy Metabolism Underlies Cellular and Molecular Immune Responses

Immune responses, as well as reproduction, are energy-hungry processes, particularly in broadcast spawners such as scallops. Thus, we aimed to explore the potential reproduction-immunity trade-off in Argopecten purpuratus, a species with great economic importance for Chile and Peru. Hemocytes, key immunological cells in mollusks, were the center of this study, where we addressed for the first time the relation between reproductive stage, hemocyte metabolic energetics and their capacity to support immune responses at cellular and molecular levels. Hemocyte metabolic capacity was assessed by their respiration rates, mitochondrial membrane potential and citrate synthase (CS) activity. Cellular immune parameters such as the number of circulating and tissue-infiltrating hemocytes and their reactive oxygen species (ROS) production capacity were considered. Molecular immune responses were examined through the transcriptional levels of two pattern recognition receptors (ApCLec and ApTLR) and two anti-microbial effectors (ferritin and big defensin). Their expressions were measured in hemocytes from immature, matured and spawned scallops under basal, and one of the following challenges: (i) in vitro, where hemocytes were challenged with the β glucan zymosan, to determine the immune potentiality under standardized conditions; or (ii) in vivo challenge, using hemocytes from scallops injected with the pathogenic bacteria Vibrio splendidus. Results indicate a post-spawning decrease in the structural components of the immune system (hemocyte number/quality) and their potential capacity of performing immune functions (with reduced ATP-producing machinery and exhaustion of energy reserves). Both in vitro and in vivo challenges demonstrate that hemocytes from immature scallops have, in most cases, the best metabolic potential (increased CS activity) and immune performances, with for example, over threefold higher ROS production and tissue-infiltration capacity than those from mature and spawned scallops after the bacterial challenge. Agreeing with cellular responses, hemocytes from immature individuals induced the highest levels of immune receptors and antimicrobial effectors after the bacterial challenge, while spawned scallops presented the lowest values. Overall, results suggest a trade-off between resource allocation in reproduction and the immune responses in A. purpuratus, with hemocyte energy metabolic capacity potentially underlying cellular and molecular immune responses. Further research would be necessary to explore regulatory mechanisms such as signaling pleiotropy which may potentially be underlying this trade-off.

Offline Lower-Limb Kinematic Decodification by Segments of EEG Signals

In this work, hip and knee angles were decoded from low frequency EEG components recorded during the execution of two tasks. In order to compare their performance, three decoders based on multiple linear regression (MLR) models were applied under different conditions; which consisted in considering the processed data as a whole or divided into segments. Results suggest that, when the segments are related to specific tasks, the segmentation provides a better performance than applying the decoding method to unsegmented data.

Cloning and molecular characterization of two ferritins from red abalone Haliotis rufescens and their expressions in response to bacterial challenge at juvenile and adult life stages

Ferritins are ubiquitous proteins with a pivotal role in iron storage and homeostasis, and in host defense responses during infection by pathogens in several organisms, including mollusks. In this study, we characterized two ferritin homologues in the red abalone Haliotis rufescens, a species of economic importance for Chile, USA and Mexico. Two ferritin subunits (Hrfer1 and Hrfer2) were cloned. Hrfer1 cDNA is an 807 bp clone containing a 516 bp open reading frame (ORF) that corresponds to a novel ferritin subunit in H. rufescens. Hrfer2 cDNA is an 868 bp clone containing a 516 bp ORF that corresponds to a previously reported ferritin subunit, but in this study 5'- and 3'-UTR sequences were additionally found. We detected a putative Iron Responsive Element (IRE) in the 5'-UTR sequence, suggesting a posttranscriptional regulation of Hrfer2 translation by iron. The deduced protein sequences of both cDNAs possessed the motifs and domains required in functional ferritin subunits. Expression patterns of both ferritins in different tissues, during different developmental stages, and in response to bacterial (Vibrio splendidus) exposure were examined. Both Hrfer1 and Hrfer2 are most expressed in digestive gland and gonad. Hrfer1 mRNA levels increased about 34-fold along with larval developmental process, attaining the highest level in the creeping post-larvae. Exogenous feeding is initiated at the creeping larva stage; thus, the increase of Hrfer1 may suggest and immunity-related role upon exposure to bacteria. Highest Hrfer2 expression levels were detected at trochophore stage; which may be related with early shell formation. Upon challenge with, the bacteria an early mild induction of Hrfer2 (2 h post-challenge), followed by a stronger induction of Hrfer1 at 15 h post-challenge, was observed in haemocytes from adult abalones. While maximal upregulation of both genes in the whole individual occurred at 24 h post-challenge, in juveniles. A significant increase in ferritin protein levels from 6 h to 24 h post-challenge was also detected. Our results suggest an involvement of Hrfer1 and Hrfer2, and of ferritin proteins in the immune response of H. rufescens to bacterial infection.

Rainbow Trout Erythrocytes ex vivo Transfection With a DNA Vaccine Encoding VHSV Glycoprotein G Induces an Antiviral Immune Response

Fish red blood cells (RBCs), are integral in several biologic processes relevant to immunity, such as pathogen recognition, pathogen binding and clearance, and production of effector molecules and cytokines. So far, one of the best strategies to control and prevent viral diseases in aquaculture is DNA immunization. DNA vaccines (based on the rhabdoviral glycoprotein G [gpG] gene) have been shown to be effective against fish rhabdoviruses. However, more knowledge about the immune response triggered by DNA immunization is necessary to develop novel and more effective strategies. In this study, we investigated the role of fish RBCs in immune responses induced by DNA vaccines. We show for the first time that rainbow trout RBCs express gpG of viral hemorrhagic septicaemia virus (VHSV) (GVHSV) when transfected with the DNA vaccine ex vivo and modulate the expression of immune genes and proteins. Functional network analysis of transcriptome profiling of RBCs expressing GVHSV revealed changes in gene expression related to G-protein coupled receptor (GPCR)-downstream signaling, complement activation, and RAR related orphan receptor α (RORA). Proteomic profile functional network analysis of GVHSV-transfected RBCs revealed proteins involved in the detoxification of reactive oxygen species, interferon-stimulated gene 15 (ISG15) antiviral mechanisms, antigen presentation of exogenous peptides, and the proteasome. Conditioned medium of GVHSV-transfected RBCs conferred antiviral protection and induced ifn1 and mx gene expression in RTG-2 cells infected with VHSV. In summary, rainbow trout nucleated RBCs could be actively participating in the regulation of the fish immune response to GVHSV DNA vaccine, and thus may represent a possible carrier cells for the development of new vaccine approaches.

The expression of TRPV channels, prostaglandin E2 and pro-inflammatory cytokines during behavioural fever in fish

A fever, or increased body temperature, is a symptom of inflammation, which is a complex defence reaction of the organism to pathogenic infections. After pathogens enter the body, immune cells secrete a number of agents, the functions of which stimulate the body to develop a functional immune and fever response. In mammals it is known that PGE₂ is the principal mediator of fever. The extent to which PGE₂ and other pro-inflammatory cytokines such as TNF-α, IL-6, or IL-1β could be involved in the induction of behavioural fever in fish remains to be clarified. Several members of the transient receptor potential (TRP) family of ion channels have been implicated as transducers of thermal stimuli, including TRPV1 and TRPV2, which are activated by heat. Here we show that members of the TRP family, TRPV1 and TRPV4, may participate in the coordination of temperature sensing during the behavioural fever. To examine the behavioral fever mechanism in Salmo salar an infection with IPNV, infectious pancreatic necrosis virus, was carried out by an immersion challenge with 10 × 10⁵ PFU/mL^-1 of IPNV. Behavioural fever impacted upon the expression levels of both TRPV1 and TRPV4 mRNAs after the viral challenge and revealed a juxtaposed regulation of TRPV channels. Our results suggest that an increase in the mRNA abundance of TRPV1 is tightly correlated with a significant elevation in the expression of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α and PGE₂) in the Pre-Optic Area (POA) and cytokine release in plasma. Together, these data indicate that the reduction of TRPV4 expression during behavioural fever may contribute to the onset of behavioural fever influencing movement toward higher water temperatures. Our data also suggest an effect of TRPV channels in the regulation of behavioural fever through activation of EP3 receptors in the central nervous system by PGE₂ induced by plasma-borne cytokines. These results highlight for first time in mobile ectotherms the key role of pro-inflammatory cytokines and TRPV channels in behavioural fever that likely involves a complex integration of prostaglandin induction, cytokine recognition and temperature sensing.