Novel Insights on the Regulation of B Cell Functionality by Members of the Tumor Necrosis Factor Superfamily in Jawed Fish

Circulating immunoglobulins and transient lymphocytopenia in a sub-study of CAPRISA 012B, testing HIV monoclonal antibodies in a phase 1 trial

Acute, transient lymphocytopenia, not clinically significant was observed in the CAPRISA 012B phase 1 clinical trial following administration of broadly neutralizing antibodies (bnAb)-CAP256V2LS alone or with VRC07-523LS. Lymphocytopenia was assigned upon a > 50% decline in absolute lymphocyte counts following bnAb administration. We posited that systemic immunoglobulins (Igs), and cytokine profiles of eight women who developed lymphocytopenia were different to the 12 women without lymphocytopenia. Plasma Ig subclasses (IgG)/isotypes (IgM/IgA), and 27 cytokines were measured at enrolment (prior to bnAbs) and at days 1, 7, 28, 56 post-bnAb administration. IgG subclasses, IgM and total lymphocyte counts were significantly lower prior to bnAbs in women with gradable lymphocytopenia than those without. Gradable lymphocytopenia compared to non-lymphocytopenia women had significantly higher MIP-1β from enrolment up to day 56. TNF-α was significantly lower in gradable lymphocytopenia compared to non-lymphocytopenia women for enrolment, days 7, 28 and 56 except for day 1. Within the gradable and within the non-lymphocytopenia women, from enrolment to day 1, significantly elevated IL-6, IL-8, IP-10, MCP-1, G-CSF and IL-1RA were found. Additionally, within the gradable lymphocytopenia women, 9 additional cytokines (TNF-α, MIP-1α, MIP-1β, RANTES, Basic FGF, eotaxin, IFN-γ, IL-17A and IL-4) were significantly elevated at day 1 post-bnAbs compared to enrolment. This sub study presents preliminary findings to support the monitoring of baseline immunological markers including lymphocyte counts for assessing the development of transient lymphocytopenia. In high-risk settings conducting clinical trials testing bnAbs for HIV prevention, understanding factors that could amplify rates of lymphocytopenia, even if transient, remain undefined.

Examining B-cell dynamics and responsiveness in different inflammatory milieus using an agent-based model

INTRODUCTION

B-cells are essential components of the immune system that neutralize infectious agents through the generation of antigen-specific antibodies and through the phagocytic functions of naïve and memory B-cells. However, the B-cell response can become compromised by a variety of conditions that alter the overall inflammatory milieu, be that due to substantial, acute insults as seen in sepsis, or due to those that produce low-level, smoldering background inflammation such as diabetes, obesity, or advanced age. This B-cell dysfunction, mediated by the inflammatory cytokines Interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-α), increases the susceptibility of late-stage sepsis patients to nosocomial infections and increases the incidence or severity of recurrent infections, such as SARS-CoV-2, in those with chronic conditions. We propose that modeling B-cell dynamics can aid the investigation of their responses to different levels and patterns of systemic inflammation.

METHODS

The B-cell Immunity Agent-based Model (BCIABM) was developed by integrating knowledge regarding naïve B-cells, short-lived plasma cells, long-lived plasma cells, memory B-cells, and regulatory B-cells, along with their various differentiation pathways and cytokines/mediators. The BCIABM was calibrated to reflect physiologic behaviors in response to: 1) mild antigen stimuli expected to result in immune sensitization through the generation of effective immune memory, and 2) severe antigen challenges representing the acute substantial inflammation seen during sepsis, previously documented in studies on B-cell behavior in septic patients. Once calibrated, the BCIABM was used to simulate the B-cell response to repeat antigen stimuli during states of low, chronic background inflammation, implemented as low background levels of IL-6 and TNF-α often seen in patients with conditions such as diabetes, obesity, or advanced age. The levels of immune responsiveness were evaluated and validated by comparing to a Veteran's Administration (VA) patient cohort with COVID-19 infection known to have a higher incidence of such comorbidities.

RESULTS

The BCIABM was successfully able to reproduce the expected appropriate development of immune memory to mild antigen exposure, as well as the immunoparalysis seen in septic patients. Simulation experiments then revealed significantly decreased B-cell responsiveness as levels of background chronic inflammation increased, reproducing the different COVID-19 infection data seen in a VA population.

CONCLUSION

The BCIABM proved useful in dynamically representing known mechanisms of B-cell function and reproduced immune memory responses across a range of different antigen exposures and inflammatory statuses. These results elucidate previous studies demonstrating a similar negative correlation between the B-cell response and background inflammation by positing an established and conserved mechanism that explains B-cell dysfunction across a wide range of phenotypic presentations.

Relationship between inflammatory-related cytokines with aortic dissection

Aortic dissection, characterized by severe intramural hematoma formation and acute endometrial rupture, is caused by excessive bleeding within the aortic wall or a severe tear within the intimal layer of the aorta, which subsequently promotes the separation or dissection in the layers of the aortic wall. Epidemiological surveys showed that aortic dissection was most observed among those patients from 55 to 80 years of age, with a prevalence of approximately 40 cases per 100,000 individuals per year, posing serious risks to future health and leading to high mortality. Other risk factors of aortic dissection progression contained dyslipidemia, hypertension, and genetic disorders, such as Marfan syndrome. Currently, emerging evidence indicates the pathological progression of aortic dissection is significantly complicated, which is correlated with the aberrant infiltration of pro-inflammatory cells into the aortic wall, subsequently facilitating the apoptosis of vascular smooth muscle cells (VSMCs) and inducing the aberrant expression of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interferon (IF). Other pro-inflammatory-related cytokines, including the colony-stimulating factor (CSF), chemotactic factor, and growth factor (GF), played an essential function in facilitating aortic dissection. Multiple studies focused on the important relationship between pro-inflammatory cytokines and aortic dissection, which could deepen the understanding of aortic dissection and further guide the therapeutic strategies in clinical practice. The present review elucidated pro-inflammatory cytokines' functions in modulating the risk of aortic dissection are summarized. Moreover, the emerging evidence that aimed to elucidate the potential mechanisms wherebyvarious pro-inflammatory cytokines affected the pathological development of aortic dissection was also listed.

Dietary Debaryomyces hansenii promotes skin and skin mucus defensive capacities in a marine fish model

The present study explores the effects of two supplementation levels of Debaryomyces hansenii (1.1% and 2.2%) as a probiotic in a reference low fish meal-based diet on the skin mucosal tissue in Sparus aurata. This study includes the evaluation of fish performance coupled with a holistic study of the skin mucosa: i) a transcriptomic study of the skin tissue, and ii) the evaluation of its secreted mucus both in terms of skin mucosal-associated biomarkers and its defensive capacity by means of co-culture analysis with two pathogenic bacteria. Results showed that after 70 days of diet administration, fish fed the diet supplemented with D. hansenii at 1.1% presented increased somatic growth and a better feed conversion ratio, compared to fish fed the control diet. In contrast, fish fed the diet including 2.2% of the probiotic presented intermediate values. Regarding gene regulation, the probiotic administration at 1.1% resulted in 712 differentially expressed genes (DEGs), among which 53.4% and 46.6% were up- and down-regulated, respectively. In particular, D. hansenii modulated some skin biological processes related to immunity and metabolism. Specifically, D. hansenii administration induced a strong modulation of some immune biological-related processes (61 DEGs), mainly involved in B- and T-cell regulatory pathways. Furthermore, dietary D. hansenii promoted the skin barrier function by the upregulation of anchoring junction genes (23 DEGs), which reinforces the physical defense against potential skin damage. In contrast, the skin showed modulated genes related to extracellular exosome and membrane organization (50 DEGs). This modulated functioning is of great interest, particularly in relation to the increased skin mucus defensive capacity observed in the bacterial co-culture in vitro trials, which could be related to the increased modulation and exudation of the innate immune components from the skin cells into the mucus. In summary, the modulation of innate immune parameters coupled with increased skin barrier function and cell trafficking potentiates the skin's physical barrier and mucus defensive capacity, while maintaining the skin mucosa's homeostatic immune and metabolic status. These findings confirmed the advantages of D. hansenii supplementation in low fish meal-based diets, demonstrating the probiotic benefits on cultured marine species.

Potential therapeutic targets of macrophages in inhibiting immune damage and fibrotic processes in musculoskeletal diseases

Macrophages are a heterogeneous cell type with high plasticity, exhibiting unique activation characteristics that modulate the progression and resolution of diseases, serving as a key mediator in maintaining tissue homeostasis. Macrophages display a variety of activation states in response to stimuli in the local environment, with their subpopulations and biological functions being dependent on the local microenvironment. Resident tissue macrophages exhibit distinct transcriptional profiles and functions, all of which are essential for maintaining internal homeostasis. Dysfunctional macrophage subpopulations, or an imbalance in the M1/M2 subpopulation ratio, contribute to the pathogenesis of diseases. In skeletal muscle disorders, immune and inflammatory damage, as well as fibrosis induced by macrophages, are prominent pathological features. Therefore, targeting macrophages is of great significance for maintaining tissue homeostasis and treating skeletal muscle disorders. In this review, we discuss the receptor-ligand interactions regulating macrophages and identify potential targets for inhibiting collateral damage and fibrosis in skeletal muscle disorders. Furthermore, we explore strategies for modulating macrophages to maintain tissue homeostasis.

Regulatory roles of cytokines in T and B lymphocytes-mediated immunity in teleost fish

T and B lymphocytes (T and B cells) are immune effector cells that play critical roles in adaptive immunity and defend against external pathogens in most vertebrates, including teleost fish. In mammals, the development and immune response of T and B cells is associated with cytokines including chemokines, interferons, interleukins, lymphokines, and tumor necrosis factors during pathogenic invasion or immunization. Given that teleost fish have evolved a similar adaptive immune system to mammals with T and B cells bearing unique receptors (B-cell receptors (BCRs) and T-cell receptors (TCRs)) and that cytokines in general have been identified, whether the regulatory roles of cytokines in T and B cell-mediated immunity are evolutionarily conserved between mammalians and teleost fish is a fascinating question. Thus, the purpose of this review is to summarize the current knowledge of teleost cytokines and T and B cells as well as the regulatory roles of cytokines on these two types of lymphocytes. This may provide important information on the parallelisms and dissimilarities of the functions of cytokines in bony fish versus higher vertebrates, which may aid in the evaluation and development of adaptive immunity-based vaccines or immunostimulants.

Local Immunoglobulin E in nasal polyps: Role and modulation

In the airway, IgE is traditionally regarded as a key mediator in allergic diseases, such as AR and allergic asthma. However, growing evidence demonstrates the importance of local IgE in airway inflammatory diseases, irrespective of the presence of allergy. In this review, we discuss the most recent evidence for IgE in chronic rhinosinusitis with nasal polyps(CRSwNP), including the local IgE’s characteristics, the modulation of its synthesis, and its function. The levels of local IgE are significantly elevated in polyps independently of IgE serum levels and atopic status. Local IgE, which is correlated with type 2 inflammation, is polyclonal and functional. IgE is produced by active B cells and is dependent on the class switch recombination(CSR). In NPs, this process is triggered by not only allergens but also microbial colonization, especially the superantigen- Staphylococcus aureus. The production of local IgE is modulated by lymphocytes(such as Tfh, ILC2s, iTreg), cytokines(such as IL-4, IL-13, IFN-γ, TGF-β, IL-2, IL-21), transcription factors, and B cell-intrinsic factor. Due to the central role of IgE in NPs, it is regarded as an ideal target for therapy and has been proved to be clinically successful. Based on this knowledge, we believe that exploring the trigger and regulatory factors for the activation of local B cells and CSR to IgE will provide more valuable information for us to recognize the pathological mechanisms of local IgE and offer the possible option for new therapeutic targets of nasal polyps.

Molecular Characterization, Evolution and Expression Analysis of TNFSF14 and Three TNFSF Receptors in Spotted Gar Lepisosteus oculatus

The tumor necrosis superfamily (TNFSF) and their receptors (TNFRs) play an essential role in inflammatory responses. In this study, tnfsf14, tnfrsf1a, tnfrsf1b and tnfrsf14 were identified in spotted gar. All the genes have conserved genomic organization and synteny with their respective homologs in zebrafish and humans. The putative TNFSF protein contains a typical TNF homology domain in the extracellular region. All three TNFRSFs possess characteristic cysteine-rich domains. TNFRSF1a has a death domain in the cytosolic region which is absent in the TNFRSF1b and TNFRSF14. Notably, TNFRSF14 lacks a transmembrane domain and is predicted to be secreted. Protein structure modeling revealed that the key residues involved in the interaction between TNFSF14 and TNFRSF14 are well conserved in spotted gar. All four genes were ubiquitously expressed in the spleen, liver, kidney, gills and intestine. Infection with Klebsiella pneumoniae resulted in remarkable downregulation of tnfsf14 and tnfrsf14 in tissues but upregulation of tnfrsf1a and tnfrsf1b. The results indicate that tnfsf14, tnfrsf1a, tnfrsf1b and tnfrsf14 are involved in the immune response to bacterial infection, and expand knowledge on the TNF system in the primitive ray-finned fish.

A Bioactive Extract Rich in Triterpenic Acid and Polyphenols from Olea europaea Promotes Systemic Immunity and Protects Atlantic Salmon Smolts Against Furunculosis

In the present study, the modulation of the transcriptional immune response (microarray analysis) in the head kidney (HK) of the anadromous fish Atlantic salmon (Salmo salar) fed a diet supplemented with an olive fruit extract (AQUOLIVE^®) was evaluated. At the end of the trial (133 days), in order to investigate the immunomodulatory properties of the phytogenic tested against a bacterial infection, an in vivo challenge with Aeromonas salmonicida was performed. A total number of 1,027 differentially expressed genes (DEGs) (805 up- and 222 downregulated) were found when comparing the transcriptomic profiling of the HK from fish fed the control and AQUOLIVE^® diets. The HK transcripteractome revealed an expression profile that mainly favored biological processes related to immunity. Particularly, the signaling of i-kappa B kinase/NF-kappa and the activation of leukocytes, such as granulocytes and neutrophils degranulation, were suggested to be the primary actors of the innate immune response promoted by the tested functional feed additive in the HK. Moreover, the bacterial challenge with A. salmonicida that lasted 12 days showed that the cumulative survival was higher in fish fed the AQUOLIVE^® diet (96.9 ± 6.4%) than the control group (60.7 ± 13.5%). These results indicate that the dietary supplementation of AQUOLIVE^® at the level of 0.15% enhanced the systemic immune response and reduced the A. salmonicida cumulative mortality in Atlantic salmon smolts.

Molecular characterization of non-specific immune genes of endangered golden mahseer (Tor putitora) and their expression during embryonic and larval development

The present study was undertaken to characterize and analyze the expression of non-specific immune genes to get an insight into the early immune status of endangered golden mahseer. In this study, the full-length mRNA sequence of IFNγ, TNFα, C3, and IL10 was 927, 1409, 5125 and 1177 bp with an ORF of 558, 765, 4938, and 540 bp, encoding a putative protein of 185, 254, 1645, and 179 amino acid residues, respectively. The deduced amino acid sequences of these genes shared highly conserved structures with those from other cyprinids. Ontogenic real-time qPCR results indicated that expression of IFNγ and TNFα was lower until the morula stage and increased from blastula stage and found maximum at the organogenesis stage. Expression of the C3 gene was lower until the gastrula stage, followed by a linear increase from organogenesis to the pre-metamorphosis stage. The expression of IL10 was significantly lower during early developmental stages (till gastrula stage) and reached maximum at organogenesis. The level of IL1β was found maximum in unfertilized eggs and remained elevated till the morula stage. TLR4 expression remained lower during the initial developmental stages and reached the maximum at the organogenesis stage. The expression level of defensin1 was substantially low until the organogenesis stage. In comparison, hepcidin1 was found considerably high until the blastula stage and remained significantly lower during later stages of development. Overall, the data generated improves knowledge on the immune status of endangered golden mahseer during embryonic and larval development, which may help develop effective immunomodulatory interventions during nursery rearing of golden mahseer to produce fry with better fitness.

The unique structure of the zebrafish TNF-α homotrimer

In the current study, zebrafish TNF-α1 (zTNF-α1) was crystallized, and the structure was analyzed. The zTNF-α1 trimer is composed of three monomers whose height and width are 50 Å and 60 Å, respectively. Compared with human TNF-α, zTNF-α1 shows only ~30% amino acid identity, the EF loop of each monomer lacks three amino acids, the CD loop is increased by four amino acids, and the AA'' loop is increased by one amino acid. In addition, an A″-β-chain is added to the zTNF-α1 monomer, forming two β-sheet layers with 6:5 β-chains. The top of the trimer is missing three amino acids and the inner coil because the EF loop seals the central hole at the top, forming a unique structure. In conclusion, the results elucidated the structure of the zTNF-α1 trimer, providing immunological knowledge for studying TNF-α function in the zebrafish animal model and structural information for exploring TNF-α family evolution.

Propagation of activated B cells by in vitro SFTSV infection of human peripheral blood mononuclear cells

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging, life-threatening tick-borne viral hemorrhagic fever (VHF) caused by SFTS virus (SFTSV). Transient appearance of plasmablastic lymphocytes in the peripheral blood of SFTS cases has been reported; however, the pathological significance of this transient burst in peripheral blood plasmablastic lymphocytes is unclear. Here, we show that SFTSV infection of human peripheral blood mononuclear cells (PBMCs) in vitro induced propagation of atypical lymphocytes. These atypical lymphocytes were activated B cells, which were induced by secretory factors other than viral particles; these factors were secreted by SFTSV-infected B cells. Activated B cells shared morphological and immunophenotypic characteristics with B cells of plasmablast lineage observed in peripheral blood and autopsy tissues of SFTS cases. This suggests that SFTSV-infected B cells secrete factors that induce B cell differentiation to plasmablasts, which may play an important role in pathogenesis of SFTS through the SFTSV-B cell axis.

The Ancient Cytokine BAFF- and APRIL-like Molecule Regulates the Functionality of Teleost IgM+ B Cells Similarly to BAFF and APRIL

TNF superfamily (TNFSF) members, such as BAFF and a proliferation-inducing ligand (APRIL), emerged in vertebrates as key regulators of B cell homeostasis and activation. Many cartilaginous and teleost fish contain an additional gene, designated as BAFF- and APRIL-like molecule (BALM), of unknown function and lost in tetrapods. In this study, we have performed a wide characterization of the functions of BALM on naive B cells for the first time, to our knowledge, in teleosts using rainbow trout (Oncorhynchus mykiss) as a model. Similar to BAFF and APRIL, BALM increased the survival and promoted the proliferation of peripheral blood IgM⁺ B cells and cooperated with BCR cross-linking to increase the proliferation rate of IgM⁺ B cells. BALM also seemed to be a differentiating factor for trout IgM⁺ B cells, as it increased IgM secretion and increased cell size. Additionally, BALM appeared to increase the Ag-presenting properties of IgM⁺ B cells, augmenting MHC class II surface expression and upregulating the phagocytic capacity of these cells. Finally, the fact that there was no synergy between BALM and BAFF/APRIL in any of these functions strongly suggests that BALM signals through the same receptors as BAFF and APRIL to carry out its functions. This hypothesis was further supported in competitive BALM binding assays. The results presented provide relevant information for understanding how these TNFSF members cooperate in teleost fish to regulate B cell functionality, helping us to interpret the evolutionary relations between molecules of this family.

Intestinal Transcriptome Analysis Reveals Soy Derivative-Linked Changes in Atlantic Salmon

Intestinal inflammation in farmed fish is a non-infectious disease that deserves attention because it is a major issue linked to carnivorous fishes. The current norm is to formulate feeds based on plant-derived substances, and the ingredients that have antinutritional factors are known to cause intestinal inflammation in fishes such as Atlantic salmon. Hence, we studied inflammatory responses in the distal intestine of Atlantic salmon that received a feed rich in soybean derivatives, employing histology, transcriptomic and flow cytometry techniques. The fish fed on soy products had altered intestinal morphology as well as upregulated inflammation-associated genes and aberrated ion transport-linked genes. The enriched pathways for the upregulated genes were among others taurine and hypotaurine metabolism, drug metabolism-cytochrome P450 and steroid biosynthesis. The enriched gene ontology terms belonged to transmembrane transporter- and channel-activities. Furthermore, soybean products altered the immune cell counts; lymphocyte-like cell populations were significantly higher in the whole blood of fish fed soy products than those of control fish. Interestingly, the transcriptome of the head kidney did not reveal any differential gene expression, unlike the observations in the distal intestine. The present study demonstrated that soybean derivatives could evoke marked changes in intestinal transport mechanisms and metabolic pathways, and these responses are likely to have a significant impact on the intestine of Atlantic salmon. Hence, soybean-induced enteritis in Atlantic salmon is an ideal model to investigate the inflammatory responses at the cellular and molecular levels.

The role of soluble mediators in the clinical course of EBV infection and B cell homeostasis after kidney transplantation

Epstein-Barr virus (EBV) reactivation can lead to serious complications in kidney transplant patients, including post-transplant lymphoproliferative disorder (PTLD). Here, we have assessed the impact of EBV on B cell homeostasis at cellular and humoral level. In a multicenter study monitoring 540 kidney transplant patients during the first post-transplant year, EBV reactivation was detected in 109 patients. Thirteen soluble factors and B cell counts were analyzed in an EBV+ sub-cohort (N = 54) before, at peak and after EBV clearance and compared to a control group (N = 50). The B cell activating factor (BAFF) was significantly elevated among EBV+ patients. No additional soluble factors were associated with EBV. Importantly, in vitro experiments confirmed the proliferative effect of BAFF on EBV-infected B cells, simultaneously promoting EBV production. In contrast, elevated levels of BAFF in EBV+ patients did not lead to B cell expansion in vivo. Moreover, diminished positive inter-correlations of soluble factors and alterations of the bi-directional interplay between B cell and soluble factors were observed in EBV+ patients at peak and after clearance. Our data suggest that such alterations may counteract the proliferative effect of BAFF, preventing B cell expansion. The role of these alterations in lymphoma development should be analyzed in future studies.

Concurrent metformin and silibinin therapy in diabetes: assessments in zebrafish (Danio rerio) animal model

Objective

In this study, zebrafish was used as a biological model to induce type 2 diabetes mellitus through glucose. Then, the effect of metformin and silibinin combination was examined on elevated blood glucose, intestinal tissues, liver enzymes, and TNF-α, IFN-γ, INL1β genes as inflammation marker genes.

Methods

The liver enzymes (AST, ALT, and ALP) derived from fish viscera homogenate supernatants were assayed in an auto-analyzer. The expression of target genes was quantified on RNA extracted from the tails by an in-house RT-PCR method, with fine intestine tissue staining performed by hematoxylin and eosin protocol (H&E).

Result

In the glucose-free treatments, metformin and silymarin decreased the levels of AST, ALT, and ALP enzymes in the blood. The combination of these two drugs had also a significant role in reducing glucose levels. The body weight increased significantly in the control group which was affected by glucose concentration, with the lowest body weight gain observed in the metformin group. The expression of INL-1β gene was significantly enhanced in the control group and the highest IFN-γ expression was observed in both control groups with glucose (G + CTRL) and without glucose (G-CTRL) (p < 0.05). The lowest level of TNF-α gene expression was observed in the control + glucose group (G + CTRL) (p < 0.05). Diabetic state causes weak absorption whereby the fish body demands to increase absorption level by enhancing the amount of acidic goblet cells thereby acidifying the environment in the gastric tracts.

Conclusion

Collectively, this study indicated that treatment with metformin and Silibinin could improve metabolic-mediated performances by reducing the expression of inflammatory genes and blood glucose, modulating liver enzymes, and ameliorating the intestinal inflammation in type 2 diabetic zebrafish model.

Epigenomics and Early Life Human Humoral Immunity: Novel Paradigms and Research Opportunities

The molecular machinery controlling immune development has been extensively investigated. Studies in animal models and adult individuals have revealed fundamental mechanisms of disease and have been essential to understanding how humans sense and respond to cellular stress, tissue damage, pathogens and their environment. Nonetheless, our understanding of how immune responses originate during human development is just starting to emerge. In particular, studies to unveil how environmental and other non-heritable factors shape the immune system at the beginning of life offer great promise to yield important knowledge about determinants of normal inter-individual immune variation and to prevent and treat many human diseases. In this review, we summarize our current understanding of some of the mechanisms determining early life antibody production as a model of an immune process with sequential molecular checkpoints susceptible to influence by non-heritable factors. We discuss the potential of epigenomics as a valuable approach that may reveal not only relevant gene-environment interactions but important clues about immune developmental processes and homeostasis in early life. We then highlight the novel paradigm of human immunology as a complex field that nowadays requires a longitudinal systems-biology approach to understand normal variation and developmental changes during the first few years of life.

Quantitative trait loci and genes associated with salmonid alphavirus load in Atlantic salmon: implications for pancreas disease resistance and tolerance

Salmonid alphavirus infection results in pancreas disease causing severe economic losses for Atlantic salmon aquaculture. Knowledge about genes and pathways contributing to resistance is limited. A 54 K SNP panel was used to genotype 10 full-sibling families each consisting of ~ 110 offspring challenged with salmonid alphavirus subtype 3. Relative heart viral load was assessed at 4- and 10-weeks post-infection using quantitative PCR. A moderate genomic heritability of viral load at 4 weeks (0.15–0.21) and a high positive correlation with survival (0.91–0.98) were detected. Positions of QTL detected on chromosome 3 matched those for survival detected by other studies. The SNP of highest significance occurred in the 3′ untranslated region of gig1, a fish-specific antiviral effector. Locus B of immunoglobulin heavy chain mapped to an area containing multiple SNPs with genome-wide association. Heart mRNA-seq comparing parr from families with high- versus low-genomic breeding value, and matching sample genotypes for SNPs, identified two eQTL for salmonid alphavirus load. Immune genes associated with trans-eQTL were numerous and spread throughout the genome. QTL regions contained several genes with known or predicted immune functions, some differentially expressed. The putative functional genes and variants identified could help improve marker-based selection for pancreas disease resistance.

Recent Advances on Phagocytic B Cells in Teleost Fish

The momentous discovery of phagocytic activity in teleost B cells has caused a dramatic paradigm shift from the belief that phagocytosis is performed mainly by professional phagocytes derived from common myeloid progenitor cells, such as macrophages/monocytes, neutrophils, and dendritic cells. Recent advances on phagocytic B cells and their microbicidal ability in teleost fish position B cells at the crossroads, bridging innate with adaptive immunity. Most importantly, an increasing body of experimental evidence demonstrates that, in both teleosts and mammals, phagocytic B cells can recognize, take up, and destroy particulate antigens and then present those processed antigens to CD4⁺ T cells to elicit adaptive immune responses and that the phagocytosis is mediated by pattern recognition receptors and involves multiple cytokines. Thus, current findings collectively indicate that teleost phagocytic B cells, as well as their counterpart mammalian B1-B cells, can be considered one kind of professional phagocyte. The aim of this review is to summarize recent advances regarding teleost phagocytic B cells, with a particular focus on the recognizing receptors and modulating mechanisms of phagocytic B cells and the process of antigen presentation for T-cell activation. We also attempt to provide new insights into the adaptive evolution of the teleost fish phagocytic B cell on the basis of its innate and adaptive roles.

Inclusion of dietary Ulva ohnoi 5% modulates Solea senegalensis immune response during Photobacterium damselae subsp. piscicida infection

Macroalgae represent valuable sources of functional ingredients for fish diets, and the influence of supplemented aquafeeds on growth performance has been studied for some fish and seaweed species. In the present work, the potential immunomodulation exerted by U. ohnoi (5%) as dietary ingredient was investigated in Senegalese sole. After feeding with the experimental diets for 90 d, fish immune response before and after challenge with Photobacterium damselae subsp. piscicida (Phdp) was assessed. In absence of infection, systemic immune response was not modified by 5% U. ohnoi dietary inclusion for 90 d. Thus, no differences in liver and head kidney immune gene transcription or serum lysozyme, peroxidase, antiprotease and complement activities were observed based on the diet received by Senegalese sole specimens. Regarding mucosal immune parameters, no changes in gene transcription were detected in the skin and gills, whilst only tnf, cd4 and cd8 were significantly up-regulated in the intestine of fish fed with U. ohnoi, compared to the values obtained with control diet. On the contrary, when S. senegalensis specimens were challenged with Phdp, modulation of the immune response consisting in increased transcription of genes encoding complement (c1q4, c3, c9), lysozyme g (lysg), tumor necrosis factor alpha (tnfα) as well as those involved in the antioxidant response (gpx, sodmn) and iron metabolism (ferrm, hamp-1) was observed in the liver of fish fed with U. ohnoi. In parallel, decreased inflammatory cytokine and complement encoding gene transcription was displayed by the spleen of fish receiving the algal diet. Though mortality rates due to Phdp challenge were not affected by the diet received, lower pathogen loads were detected in the liver of soles receiving U. ohnoi diet. Further research to investigate the effects of higher inclusion levels of this seaweed in fish diets, feeding during short periods as wells as to assess the response against other pathogens needs to be carried out.

Molecular evolution of the tnfr gene family and expression profiles in response to pathogens in lamprey(Lethenteron reissneri)

Tumor necrosis factor receptor superfamilies (TNFRSF) are one of essential cytokines and can trigger inflammation, apoptosis, participating lymphocyte homeostasis and tissue development in vertebrates. To gain insights into the evolution and characterization of tnfr genes in lamprey, a jawless vertebrate, we performed a genome-wide and transcriptome survey and identified 7 tnfr genes in the lamprey (Lethenteron reissneri) database. Based on the molecular phylogenetic analysis, 7 L-tnfr genes are divided into three different clusters, and multiple members of tnfr genes family have appeared in lamprey. Meanwhile, protein domains and motifs analysis reveals that TNFRSF are conserved and have typical cysteine-rich domains (CRDs). Synteny results indicates that the L-tnfr neighborhood genes have taken place great changes compared to jawed vertebrates. Real-time quantitative results demonstrate that tnfr gene family plays an important role in the immune defense. This study has a new understanding for origin and evolution of the tnfr gene family in different vertebrates.

Rainbow Trout IgM+ B Cells Preferentially Respond to Thymus-Independent Antigens but Are Activated by CD40L

In the absence of class switch recombination and germinal centers, the mechanisms through which B cells from teleost fish mount extrafollicular immunoglobulin M (IgM) memory responses remains mostly unexplored. In this report, we demonstrate that teleost IgM⁺ B cells respond to CD40L, a thymus-dependent activation signal, similarly to mammalian B2 cells. However, when stimulated with different types of antigens, fish IgM⁺ B cells only reach a general activation state in response to antigens cataloged as thymus-independent 1 (TI-1) in mammals, as established through both functional assays and RNA sequencing. Interestingly, fish IgM⁺ B cells remained completely unresponsive to TI-2 antigens, suggesting that the engagement of innate receptors provided by TI-1 antigens is required for the activation of teleost B cells. Finally, a synergy between CD40L and TI-1 antigens was also demonstrated, further supporting that there is no clear dichotomy between thymus-dependent and TI responses in teleost fish.

Role of teleost B cells in viral immunity

Teleost fish possess all the necessary elements to mount an adaptive immune response. Despite this, the important physiological and structural differences between the mammalian and the teleost fish immune system, anticipate significant changes regarding how this response is coordinated and executed. B cells are key players in adaptive immune responses through the production of antibodies. However, recent studies performed in mammals and other species including fish point to many additional functions of B cells within both the adaptive and the innate immune system, in many occasions taking part in the crosstalk between these two arms of the immune response. Furthermore, it should be taken into account that fish B cells share many functional and phenotypical features with innate B cell populations from mammals, which will surely condition their response to antigens. Concerning viral infections, although most studies undertaken to date in fish have been focused on characterizing antibody production, some recent studies have demonstrated that fish B cells are able to interact with viruses at different levels. In this sense, in the current review, we have tried to provide an overview of what is currently known regarding the role of teleost B cells in antiviral immunity.

Regulation of IgM+ B Cell Activities by Rainbow Trout APRIL Reveals Specific Effects of This Cytokine in Lower Vertebrates

Tumor necrosis factor ligand superfamily members such as B cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL) have been identified in mammals as key regulators of B cell homeostasis and activation. However, the immune functions of APRIL are not as well defined as those of BAFF. Furthermore, while BAFF is present in all vertebrates, APRIL is missing in some animal groups, suggesting that BAFF has compensated the functions of APRIL in these species. In this context, we thought of great interest to explore the effects of APRIL on teleost B cells, given that APRIL appears for the first time in evolution in bony fish. Thus, in this study, we have performed an extensive analysis of the effect of APRIL on B cells using rainbow trout (Oncorhynchus mykiss) as a model species. Our results demonstrate that APRIL induces a specific proliferation of IgM⁺ B cells by itself and increases IgM secretion without promoting a terminal differentiation to plasma cells. APRIL also increased the levels of surface MHC II and augmented the capacity of these cells to process antigen, effects that were exclusively exerted on IgM⁺ B cells. Although our results point to a highly conserved role of APRIL on B cell homeostasis and activation throughout evolution, some specific differential effects have been observed in fish in comparison to the effects of APRIL previously described in mammals. Finally, the effects that APRIL induces on rainbow trout IgM⁺ B cells described in this paper have been compared with those previously reported in response to BAFF.

Cytokines in aortic dissection

Aortic dissection (AD) is one of the most dangerous forms of vascular disease, characterized by endometrial rupture and intramural hematoma formation. Generally, the pathological process is complicated and closely related to the infiltration of inflammatory cells into the aortic wall and apoptosis of vascular smooth muscle cells. Currently, multiple cytokines, including interleukins, interferon, the tumor necrosis factor superfamily, colony stimulating factor, chemotactic factor, growth factor and so on, have all been demonstrated to play a critical role in AD. Additionally, studies of the link between cytokines and AD could deepen our understanding of the disease and may guide future treatment therapies; therefore, this review focuses on the role of cytokines in AD.