Innate Immune Function Research Articles

Abrupt-mediated control of Ninjurins regulates Drosophila sessile hemocyte compartments.

Macrophage-like cells called hemocytes are key effectors of Drosophila cellular innate immune function. Larval hemocytes exist either in circulation or localise to segmentally-repeated sessile hemocyte compartments (SHCs). While numerous functions have been proposed for SHCs, the mechanisms directing hemocytes to them are unclear. Here, we have exploited the developmentally-regulated dispersal of SHCs that occurs at pupariation to identify the Abrupt (Ab) transcription factor (TF) and Ninjurin cell adhesion molecules as regulators of hemocyte recruitment to SHCs. We show that larval hemocytes express Ninjurins which are required for targeting hemocytes to SHCs. However, at pupariation, ecdysteroid signaling stimulates Ab expression, which collaborates with TFs including Blimp-1 and Hr3 to repress Ninjurins and disperse hemocytes. We observe that experimental manipulations that antagonise Ninjurin function in larval hemocytes cause premature SHC dispersal, while stabilization of Ninjurins in hemocytes blocks developmentally-regulated SHC remodeling and increases sensitivity to immune challenges. Cumulatively, our data indicate that control of Ninjurin activity provides a common target through which diverse developmental, environmental, and immune stimuli can be integrated to control hemocyte dispersal and immune function.

Benzoic Acid potentiates intestinal IgA response in broiler chickens against Salmonella enterica Serovar Typhimurium infection

As a feed additive, Benzoic Acid (BA) has been demonstrated to significantly enhance feed conversion efficiency, regulate gastrointestinal pH, and improve overall animal health. Young animals, highly susceptible to S. Typhimurium infection, suffer from high mortality rates and substantial economic losses due to this pathogen. Despite promising indications of BA's immunomodulatory potential in boosting intestinal immunity, its underlying mechanisms remain insufficiently understood. This study investigates how BA strengthens intestinal anti-infection defenses in young animals via immunomodulatory pathways, focusing on its impact on macrophage polarization and IgA-mediated immune responses. Employing in vitro cell experiments and animal models, we examined the macrophage phenotypic alterations following BA treatment. We assessed the expression of immune-related genes in the intestine through immunofluorescence staining, Western blotting, and quantitative real-time PCR. The results demonstrate that BA promotes M2 macrophage polarization by activating the mTOR/PPAR-γ/STAT3 signaling pathways. Furthermore, BA enhances the intestinal expression of the polymeric immunoglobulin receptor (PIgR), B-cell activating factor (BAFF) from the TNF family, and activation-induced cytidine deaminase (AID), thereby enhancing IgA production by B-cells. These results underscore the potential of BA to bolster innate immune functions in young chickens, mitigate intestinal damage caused by S. Typhimurium infection, and ultimately promote both animal health and food safety.

Immune response to topical sodium lauryl sulfate differs from classical irritant and allergic contact dermatitis.

Sodium lauryl sulfate (SLS) is used as a control irritant in patch testing for allergic contact dermatitis (ACD). However, up to 20% of those tested react to SLS, whereby the pathophysiological basis of this reaction is still unclear. To mimic patch test reactions, we repeatedly applied SLS to the skin of wild-type mice. Reactions were compared with those in a classical ACD model induced by oxazolone and an irritant contact dermatitis (ICD) model induced by croton oil. Skin inflammation was assessed with ear thickness measurements, immunohistochemistry, qRT-PCR, and flow cytometry. Topical SLS treatment was further investigated in Flg/Hrnr-/-, Myd88/Tlr3-/-, and Rag1-/- mouse models. All three compounds caused ear swelling with different courses. Oxazolone treatment, compared with the ICD model, resulted in a greater influx of immune cells (CD4+, MHCII+, CD11b+). Similarly, SLS did not induce immune cell infiltration or expression of selected inflammatory and regulatory cytokines. SLS induced the most pronounced keratinocyte proliferation. Compared with wild-type mice, topical SLS application did not increase ear swelling in skin barrier deficient Flg/Hrnr-/- mice, but led to significantly delayed swelling in mice with defects in innate or adaptive immune functions (Myd88/Tlr3-/-, Rag1-/-). SLS-induced contact dermatitis differed from classical ACD and ICD, as it elicited less pronounced immune alterations. Skin barrier impairment does not affect SLS-induced contact dermatitis, whereas both innate and adaptive components are involved in SLS skin reactions.

Comparative analysis of innate immune responses in Sonali and broiler chickens infected with tribasic H9N2 low pathogenic avian influenza virus

BackgroundH9N2 avian influenza viruses have been circulating in Bangladesh since 2006, affecting multiple avian species and resulting in economic losses. The recent emergence of tribasic strains, along with co-infections, has increased the risk to poultry health. Therefore, the study aimed to compare the immune responses of Sonali (crossbred) and commercial broiler chickens infected with tribasic H9N2 low pathogenic avian influenza (LPAI) virus.MethodsFollowing H9N2 infection, proinflammatory (IL-6, IL-8, IL-1β and TNF-α) and antiviral (IFN-β and IFN-γ) cytokine expressions were observed in the trachea, lungs, intestine, and lymphoid tissues in Sonali and broiler chickens from 1 day post infection (dpi) to 10 dpi by qPCR.ResultsSonali chickens exhibited significantly higher proinflammatory and antiviral cytokine expressions in the trachea at 3–7 days post infection (dpi), while broiler chickens showed lower immune responses. Broiler chickens displayed prolonged IL-6, IL-8, and IL-1β expression in lungs at 3–10 dpi compared to Sonali chickens. In the intestine, broiler chickens showed higher IL-6 and IL-8 expression that peaks at 1–3 dpi, while in Sonali chickens only IL-1β elevated at 10 dpi. In response to the H9N2 viruses, broiler chickens exhibited a stronger early IFN-β responses and a delayed IFN-γ responses in their lymphoid organs compared to Sonali chickens.ConclusionThis suggests distinct immune profiles between the chicken types in response to the H9N2 infection. The information sheds light on the function of innate immunity in the pathophysiology of currently circulating tribasic H9N2 virus and could assist in effective controlling of avian influenza virus spread in poultry and designing vaccines.

Factors Associated with Increased Risk of Contamination in Bone Marrow Transplants.

Hematopoietic cell transplantation (HCT) remains the definitive therapeutic modality for numerous malignant and non-malignant hematologic disorders. Conventional bone marrow remains a viable donor source for HCT. However, microbial contamination of bone marrow harvests may present a risk to immunocompromised recipients. This analysis sought to identify clinical factors associated with bone marrow contamination. We analyzed a single institution experience comprising 667 unique bone marrow harvests collected between 1999 and 2021. We trended the yearly microbial contamination rate over this time span. Harvest type (autologous vs allogenic), donor age, donor sex, physician experience, total nucleated cell (TNC) count, volume collected, and TNC concentration were included in a univariate (UV) and multivariate (MV) logistic model to assess which factors were associated with contamination. Males comprised 55.8% of the donor population and the median age of the cohort was 35 [IQR: 27-45]. There were 19 autologous, 151 related allogenic, and 497 unrelated allogenic transplants in this cohort. 87 of the 667 (13.0%) harvests were contaminated and essentially all contaminants were common skin flora. The yearly contamination rates displayed substantial variability, ranging from 0% to 42.9%, with no discernible trend. Harvest type did not exhibit a significant association with contamination risk. However, male donor sex was found to be significantly associated with a higher contamination rate (18%) compared to female sex (6.8%, p < 0.001). In both UV and MV logistic models, male sex emerged as the sole factor linked to contamination risk (OR: 2.90, 95% CI: 1.65 - 5.35). This analysis represents the largest single center investigation of bone marrow harvest microbial contamination rates. Notably, it is the first to establish an association between contamination and male donor sex. We propose that this association may be attributed to differences in skin flora composition or innate immune function between sexes, general hygiene practices or possibly the result of the frequent clipping of body hair in males prior to the harvest procedure. Further research is warranted to explore the underlying mechanisms and clinical implications of this novel finding.

Impact of Senescent Cell-Derived Extracellular Vesicles on Innate Immune Cell Function.

Extracellular vesicles (EVs) are components of the senescence-associated secretory phenotype (SASP) that influence cellular functions via their cargo. Here, the interaction between EVs derived from senescent (SEVs) and non-senescent (N-SEVs) fibroblasts and the immune system is investigated. Via endocytosis, SEVs are phagocytosed by monocytes, neutrophils, and B cells. Studies with the monocytic THP-1 cell line find that pretreatment with SEVs results in a 32% (p < 0.0001) and 66% (p < 0.0001) increase in lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-α) production when compared to vehicle control or N-SEVs respectively. Interestingly, relative to vehicle control, THP-1 cells exposed to N-SEVs exhibit a 20% decrease in TNF-α secretion (p < 0.05). RNA sequencing reveals significant differences in gene expression in THP-1 cells treated with SEVs or N-SEVs, with vesicle-mediated transport and cell cycle regulation pathways featuring predominantly with N-SEV treatment, while pathways relating to SLITS/ROBO signaling, cell metabolism, and cell cycle regulation are enriched in THP-1 cells treated with SEVs. Proteomic analysis also reveals significant differences between SEV and N-SEV cargo. These results demonstrate that phagocytes and B cells uptake SEVs and drive monocytes toward a more proinflammatory phenotype upon LPS stimulation. SEVs may therefore contribute to the more proinflammatory immune response seen with aging.

Characterization of cellular and molecular immune components of the painted white sea urchin Lytechinus pictus in response to bacterial infection.

Sea urchins are basal deuterostomes that share key molecular components of innate immunity with vertebrates. They are a powerful model for the study of innate immune system evolution and function, especially during early development. Here we characterize the morphology and associated molecular markers of larval immune cell types in a newly developed model sea urchin, Lytechinus pictus. We then challenge larvae through infection with an established pathogenic Vibrio and characterize phenotypic and molecular responses. We contrast these to the previously described immune responses of the purple sea urchin Strongylocentrotus purpuratus. The results revealed shared cellular morphologies and homologs of known pigment cell immunocyte markers (PKS, srcr142) but a striking absence of subsets of perforin-like macpf genes in blastocoelar cell immunocytes. We also identified novel patterning of cells expressing a scavenger receptor cysteine rich (SRCR) gene in the coelomic pouches of the larva (the embryonic stem cell niche). The SRCR signal becomes further enriched in both pouches in response to bacterial infection. Collectively, these results provide a foundation for the study of immune responses in L. pictus. The characterization of the larval immune system of this rapidly developing and genetically enabled sea urchin species will facilitate more sophisticated studies of innate immunity and the crosstalk between the immune system and development.

The impact of trauma relevant concentrations of prostaglandin E2 on the anti-microbial activity of the innate immune system.

The mechanisms underlying the state of systemic immune suppression that develops following major trauma are poorly understood. A post-injury increase in circulating levels of prostaglandin E2 (PGE2) has been proposed as a contributory factor, yet few studies have addressed how trauma influences PGE2 biology. Blood samples from 95 traumatically-injured patients (injury severity score ≥8) were collected across the pre-hospital (≤2 hours), acute (4-12 hours) and subacute (48-72 hours) post-injury settings. Alongside ex vivo assessments of lipopolysaccharide (LPS)-induced cytokine production by monocytes, neutrophil reactive oxygen species production and phagocytosis, serum concentrations of PGE2 and its scavenger albumin were measured, and the expression of enzymes and receptors involved in PGE2 synthesis and signalling analysed. Leukocytes from trauma patients were treated with cyclooxygenase (COX) inhibitors (indomethacin or NS-398), or the protein kinase A inhibitor H89, to determine whether injury-induced immune suppression could be reversed by targeting the PGE2 pathway. The effect that trauma relevant concentrations of PGE2 had on the anti-microbial functions of neutrophils, monocytes and monocyte-derived macrophages (MDMs) from healthy controls (HC) was examined, as was the effect of PGE2 on efferocytosis. To identify factors that may trigger PGE2 production post-trauma, leukocytes from HC were treated with mitochondrial-derived damage associated molecular patterns (mtDAMPs) and COX-2 expression and PGE2 generation measured. PGE2 concentrations peaked in blood samples acquired ≤2 hours post-injury and coincided with significantly reduced levels of albumin and impaired LPS-induced cytokine production by monocytes. Significantly higher COX-2 and phospholipase A2 expression was detected in neutrophils and/or peripheral blood mononuclear cells isolated from trauma patients. Treatment of patient leukocytes with indomethacin, NS-398 or H89 enhanced LPS-induced cytokine production and neutrophil extracellular trap generation. Exposure to physiological concentrations of PGE2 suppressed the anti-microbial activity of monocytes, neutrophils and MDMs of HC, but did not influence efferocytosis. In a formyl-peptide receptor-1 dependent manner, mtDAMP treatment significantly increased COX-2 protein expression in neutrophils and monocytes, which resulted in increased PGE2 production. Physiological concentrations of PGE2 suppress the anti-microbial activities of neutrophils, monocytes and MDMs. Targeting the PGE2 pathway could be a therapeutic approach by which to enhance innate immune function post-injury.

Loss of function in Drosophila transcription factor Dif delays brain development in larvae resulting in aging adult brain

Drosophila NF-κB transcription factor Dif has been well known for its function in innate immunity, and recent study also reveals its role in neuronal cells. However, the underlying mechanisms of Dif in the brain remain elusive. In this study, we aim to investigate the function of Dif in Drosophila brain development and how Dif regulates structure and plasticity of the brain to affect aging and behaviors. Based on the analysis of differentially expressed genes, we identified key genes associated with cell division, development and aging in the brain of Dif1 loss of function mutant. In Dif1 larvae, we found that the metamorphosis and brain development were delayed, and cell division was decreased. In Dif1 adults, the number of neuron cells was reduced in the brain, the lifespan and locomotor activity were decreased, protein markers associated with aging-related neurodegenerative diseases in the brain were altered in abundance or activity. Our results indicated that Dif plays a crucial role in brain plasticity and neurogenesis, dysfunction of Dif delays larval brain development and impacts proliferation of neuronal cells, resulting in aging adult brain by regulating expression of key genes in multiple signaling pathways involved in cell division, neurogenesis and aging.

Botanical oleander extract and oleandrin have superior effects on innate immune functions pertaining to dermal allergic reactions in canine cells when compared to oclacitinib.

To perform testing for cytokines involved in dermal inflammatory reactions and to document and compare the effects of an oleander extract (OE), oleandrin, and oclacitinib on biomarkers relevant to allergic reactions. The effects of these compounds under inflamed culture conditions are of direct importance to the treatment of canine atopic dermatitis. Testing involved primary canine dermal fibroblasts and the canine DH82 macrophage cell line; both cell types are important for initiating, regulating, and resolving dermal allergic reactions via cytokine communication. Under inflamed conditions, OE and oleandrin downregulated key cytokines secreted by canine dermal fibroblasts and the DH82 macrophage cell line; all of which are treatment targets in dermatitis. In the DH82 macrophage cultures, the most noteworthy reductions involved IL-6, IL-12/IL-23p40, interferon-γ, tumor necrosis factor-α, VEGF, and nerve growth factor-β. Oclacitinib triggered reductions of some cytokines involved in allergic reactions, including TGF-β1, IL-12/IL-23p40, and tumor necrosis factor-α; however, these reductions were less robust than the reductions triggered by OE and oleandrin and accompanied by increases in other cytokines involved in dermal inflammation, including IL-6, interferon-γ, and nerve growth factor-β. In cultures of primary dermal fibroblasts, OE and oleandrin reduced the levels of IL-8 and monocyte chemoattractant protein-1, whereas oclacitinib had little or no effect. Oleander extract and oleandrin directly modulate immune responses under inflamed conditions. Moreover, OE and oleandrin appear to provide a more beneficial overall cytokine regulation than oclacitinib under inflamed culture conditions. These results suggest that OE and oleandrin are efficacious agents to treat canine atopic dermatitis. Future studies should evaluate the efficacy of these compounds in dogs affected by atopic dermatitis.

Kupffer Cells and Hepatocytes: A Key Relation in the Context of Canine Leishmaniasis.

Human zoonotic visceral leishmaniasis (ZVL) and canine leishmaniasis (CanL) constitute a major public and veterinary health concern and are both caused by the infection with the protozoan parasite Leishmania infantum. One of the main target organs in CanL is the liver. This complex organ, composed of various highly specialized cell types, has garnered significant attention from the scientific community as a crucial player in innate immune functions. In the context of CanL, liver infection by parasites and the host immune response generated strongly influence the disease outcome. Thus, taking advantage of a co-culture system involving canine hepatocytes and L. infantum-infected autologous Kupffer cells (KCs), allowing cell-to-cell interaction, the current report aims to shed light on the hepatocyte-KCs immune interaction. The co-culture of infected KCs with hepatocytes revealed a vital role of these cells in the activation of a local immune response against L. infantum parasites. Although KCs alone can be immunologically silenced by L. infantum infection, the cell-to-cell interaction with hepatocytes in co-culture can lead to local immune activation. In co-culture it was observed gene expression increased the number of innate immune receptors, specifically cell membrane TLR2 and cytoplasmatic NOD1 along with high TNF-α generation. Altogether, these results suggest that the immune response generated in co-culture could induce the recruitment of other circulating cells to contain and contribute to the resolution of the infection in the liver. This work also enhances our understanding of the liver as a vital organ in innate immunity within the context of CanL.

Complement-Mediated Two-Step NETosis: Serum-Induced Complement Activation and Calcium Influx Generate NADPH Oxidase-Dependent NETs in Serum-Free Conditions.

The complement system and neutrophils play crucial roles in innate immunity. Neutrophils release neutrophil extracellular traps (NETs), which are composed of decondensed DNA entangled with granular contents, as part of their innate immune function. Mechanisms governing complement-mediated NET formation remain unclear. In this study, we tested a two-step NETosis mechanism, as follows: classical complement-mediated neutrophil activation in serum and subsequent NET formation in serum-free conditions, using neutrophils from healthy donors, endothelial cells, and various assays (Fluo-4AM, DHR123, and SYTOX), along with flow cytometry and confocal microscopy. Our findings reveal that classical complement activation on neutrophils upregulated the membrane-anchored complement regulators CD46, CD55, and CD59. Additionally, complement activation increased CD11b on neutrophils, signifying activation and promoting their attachment to endothelial cells. Complement activation induced calcium influx and citrullination of histone 3 (CitH3) in neutrophils. However, CitH3 formation alone was insufficient for NET generation. Importantly, NET formation occurred only when neutrophils were in serum-free conditions. In such environments, neutrophils induced NADPH oxidase-dependent reactive oxygen species (ROS) production, leading to NET formation. Hence, we propose that complement-mediated NET formation involves a two-step process, as follows: complement deposition, neutrophil priming, calcium influx, CitH3 formation, and attachment to endothelial cells in serum. This is followed by NADPH-dependent ROS production and NET completion in serum-free conditions. Understanding this process may unveil treatment targets for pathologies involving complement activation and NET formation.

Reduced B cell frequencies in cord blood of HIV-exposed uninfected infants: an immunological and transcriptomic analysis.

In the course of immune development, HIV-exposed uninfected (HEU) infants exhibit abnormal immune function and increased infectious morbidity compared to HIV-unexposed uninfected (HUU) infants. Yet the specific functional phenotypes and regulatory mechanisms associated with in-utero HIV and/or ART exposure remain largely obscure. We utilized flow cytometry and RNA-seq technologies to conduct the immunological and transcriptomic profiling in cord blood from 9 HEU mother-infant pairs and 24 HUU pairs. On top of that, we compared the cord blood dataset with the maternal venous blood dataset to characterize unique effects induced by in-utero HIV and/or ART exposure. Flow cytometry immunophenotyping revealed that the level of B lymphocyte subsets was significantly decreased in HEU cord blood as compared to HUU (P < 0.001). Expression profiling-based cell abundance assessment, includes CIBERSORT and ssGSEA algorithm, showed a significantly reduced abundance of naive B cells in HEU cord blood (both P < 0.05), supporting the altered composition of B lymphocyte subsets in HEU. Functional enrichment analysis demonstrated suppressed innate immune responses and impaired immune regulatory function of B cells in HEU cord blood. Furthermore, through differential expression analysis, co-expression network analysis using WGCNA, and feature selection analysis using LASSO, we identified a 4-gene signature associated with HEU status. This signature effectively assesses B cell levels in cord blood, enabling discrimination between HEU and HUU infants. Our study provides the first comprehensive immunological and transcriptomic characterization of HEU cord blood. Additionally, we establish a 4-gene-based classifier that holds potential for predict immunological abnormalities in HEU infants.

Dissecting the immune response of CD4+ Tcells in Alzheimer's disease.

The formation of amyloid-β (Aβ) plaques is a neuropathological hallmark of Alzheimer's disease (AD), however, these pathological aggregates can also be found in the brains of cognitively unimpaired elderly population. In that context, individual variations in the Aβ-specific immune response could be key factors that determine the level of Aβ-induced neuroinflammation and thus the propensity to develop AD. CD4+ Tcells are the cornerstone of the immune response that coordinate the effector functions of both adaptive and innate immunity. However, despite intensive research efforts, the precise role of these cells during AD pathogenesis is still not fully elucidated. Both pathogenic and beneficial effects have been observed in various animal models of AD, as well as in humans with AD. Although this functional duality of CD4+ Tcells in AD can be simply attributed to the vast phenotype heterogeneity of this cell lineage, disease stage-specific effect have also been proposed. Therefore, in this review, we summarized the current understanding of the role of CD4+ Tcells in the pathophysiology of AD, from the aspect of their antigen specificity, activation, and phenotype characteristics. Such knowledge is of practical importance as it paves the way for immunomodulation as a therapeutic option for AD treatment, given that currently available therapies have not yielded satisfactory results.

Alterations in visible light exposure modulate platelet function and regulate thrombus formation

BackgroundVariations in light exposure are associated with changes in inflammation and coagulation. The impact of light spectra on venous (VT) and arterial thrombosis is largely unexplored. ObjectivesTo investigate the impact of altering light spectrum on platelet function in thrombosis. MethodsWild type (WT) C57BL/6J mice were exposed to ambient (micewhite, 400lux), blue (miceblue, 442nm, 1,400lux), or red light (micered, 617nm, 1,400lux) with 12:12 hour light:dark cycle for 72 hours. After 72 hours of light exposure, platelet aggregation, activation, transcriptomic, and metabolomic changes were measured. The ability of released products of platelet activation to induce thrombosis-generating NET formation was quantified. Subsequent thrombosis was measured using murine models of VT and stroke. To translate our findings to human patients, light filtering cataract patients were evaluated over an 8-year period for rate of VTE with multivariable logistic regression clustered by hospital. ResultsExposure to long wavelength red light resulted in reduced platelet aggregation and activation. RNA-seq analysis demonstrated no significant transcriptomic changes between micered and micewhite. However, there were global metabolomic changes in platelets from micered compared to micewhite. Releasate from activated platelets resulted in reduced NET formation. Micered also had reduced VT weight and brain infarct size following stroke. On subgroup analysis of cataract patients, patients with a history of cancer have lower lifetime risk of VTE after implantation with lenses that filter low wavelength light. ConclusionsLight therapy may be a promising approach to thrombus prophylaxis by specifically targeting the intersection between innate immune function and coagulation.

The Impact of Liver Failure on the Immune System.

Liver failure profoundly affects the immune system, leading to dysregulation of innate and adaptive immune response. This review explores the intricate relationship between liver function and immune homeostasis. The role of the liver as a central hub in immune response initiation is elucidated, emphasizing its involvement in hepatic inflammation induction and subsequent systemic inflammation. Cytokines, chemokines, growth factors, and lipid mediators orchestrate these immune processes, serving as both prognostic biomarkers and potential therapeutic targets in liver failure-associated immune dysregulation, which might result from acute-on-chronic liver failure (ACLF) and cirrhosis. Furthermore, the review delves into the mechanisms underlying immunosuppression in liver failure, encompassing alterations in innate immune cell functions such as neutrophils, macrophages, and natural killer cells (NK cells), as well as perturbations in adaptive immune responses mediated by B and T cells. Conclusion: Understanding the immunological consequences of liver failure is crucial for developing targeted therapeutic interventions and improving patient outcomes in liver disease management.

SRP54 of black carp negatively regulates MDA5-mediated antiviral innate immunity

Signal Recognition Particle 54 kDa (SRP54) is a subunit of the signal recognition particle (SRP), a cytoplasmic ribonucleoprotein complex guiding the transportation of newly synthesized proteins from polyribosomes to endoplasmic reticulum. In mammals, it has been reported to regulate the RLR signaling pathway negatively by impairing the association between MAVS and MDA5/RIG-I. However, the role of SRP54 in teleost antiviral innate immune response remains obscure. In this study, the SRP54 homolog of black carp (bcSRP54) has been cloned, and its function in antiviral innate immunity has been elucidated. The CDS of bcSRP54 gene consists of 1515 nucleotides and encodes 504 amino acids. Immunofluorescence (IF) showed that bcSRP54 was mainly distributed in the cytoplasm. Overexpressed bcSRP54 significantly reduced bcMDA5-mediated transcription of interferon (IFN) promoter in reporter assay. Co-expression of bcSRP54 and bcMDA5 significantly suppressed bcMDA5-mediated IFN signaling and antiviral activity, while bcSRP54 knockdown increased the antiviral ability of host cells. In addition, the results of the immunofluorescence staining demonstrated the subcellular overlapping between bcSRP54 and bcMDA5, and the co-immunoprecipitation (co-IP) experiment identified their association. Furthermore, the over-expression of bcSRP54 did not influence the protein expression and ubiquitination modification level of bcMDA5, however, hindered the binding of bcMDA5 to bcMAVS. In summary, our results conclude that bcSRP54 targets bcMDA5 and inhibits the interaction between bcMDA5 and bcMAVS, thereby negatively regulating antiviral innate immunity, which provides insight into how teleost SRP54 regulates IFN signaling.

Hypomorphic mutation in the large subunit of replication protein A affects mutagenesis by human APOBEC cytidine deaminases in yeast.

Human APOBEC single-strand (ss) specific DNA and RNA cytidine deaminases change cytosines to uracils (U's) and function in antiviral innate immunity and RNA editing and can cause hypermutation in chromosomes. The resulting U's can be directly replicated, resulting in C to T mutations, or U-DNA glycosylase can convert the U's to abasic (AP) sites which are then fixed as C to T or C to G mutations by translesion DNA polymerases. We noticed that in yeast and in human cancers, contributions of C to T and C to G mutations depend on the origin of ssDNA mutagenized by APOBECs. Since ssDNA in eukaryotic genomes readily binds to replication protein A (RPA) we asked if RPA could affect APOBEC-induced mutation spectrum in yeast. For that purpose, we expressed human APOBECs in the wild-type (WT) yeast and in strains carrying a hypomorph mutation rfa1-t33 in the large RPA subunit. We confirmed that the rfa1-t33 allele can facilitate mutagenesis by APOBECs. We also found that the rfa1-t33 mutation changed the ratio of APOBEC3A-induced T to C and T to G mutations in replicating yeast to resemble a ratio observed in long persistent ssDNA in yeast and in cancers. We present the data suggesting that RPA may shield APOBEC formed U's in ssDNA from Ung1, thereby facilitating C to T mutagenesis through the accurate copying of U's by replicative DNA polymerases. Unexpectedly, we also found that for U's shielded from Ung1 by WT RPA, the mutagenic outcome is reduced in the presence of translesion DNA polymerase zeta.

Rejuvenating bone marrow hematopoietic reserve prevents regeneration failure and hepatic decompensation in animal model of cirrhosis.

Bone marrow stem cells (BM-SCs) and their progeny play a central role in tissue repair and regeneration. In patients with chronic liver failure, bone marrow (BM) reserve is severally compromised and they showed marked defects in the resolution of injury and infection, leading to liver failure and the onset of decompensation. Whether BM failure is the cause or consequence of liver failure during cirrhosis is not known. In this study, we aimed to determine the underlying relationship between BM failure and regeneration failure in cirrhosis. C57Bl/6(J) mice were used to develop chronic liver injury through intra-peritoneal administration of carbon tetrachloride (CCl4) for 15 weeks (0.1-0.5 ml/kg). Animals were sacrificed to study the transition of cirrhosis and BM defects. To restore the BM-SC reserve; healthy BM cells were infused via intra-BM infusion and assessed for changes in liver injury, regeneration, and BM-SC reserve. Using a CCl4-induced animal - model of cirrhosis, we showed the loss of BM-SCs reserve occurred before regeneration failure and the onset of non-acute decompensation. Intra-BM infusion of healthy BM cells induced the repopulation of native hematopoietic stem cells (HSCs) in cirrhotic BM. Restoring BM-HSCs reserve augments liver macrophage-mediated clearance of infection and inflammation dampens neutrophil-mediated inflammation, accelerates fibrosis regression, enhances hepatocyte proliferation, and delays the onset of non-acute decompensation. These findings suggest that loss of BM-HSCs reserve underlies the compromised innate immune function of the liver, drives regeneration failure, and the onset of non-acute decompensation. We further provide the proof-of-concept that rejuvenating BM-HSC reserve can serve as a potential therapeutic approach for preventing regeneration failure and transition to decompensated cirrhosis.

The β-d-manno-heptoses are immune agonists across kingdoms.

Bacterial small molecule metabolites such as adenosine-diphosphate-d-glycero-β-d-manno-heptose (ADP-heptose) and their derivatives act as effective innate immune agonists in mammals. We show that functional nucleotide-diphosphate-heptose biosynthetic enzymes (HBEs) are distributed widely in bacteria, archaea, eukaryotes, and viruses. We identified a conserved STTR5 motif as a hallmark of heptose nucleotidyltransferases that can synthesize not only ADP-heptose but also cytidine-diphosphate (CDP)- and uridine-diphosphate (UDP)-heptose. Both CDP- and UDP-heptoses are agonists that trigger stronger alpha-protein kinase 1 (ALPK1)-dependent immune responses than ADP-heptose in human and mouse cells and mice. We also produced ADP-heptose in archaea and verified its innate immune agonist functions. Hence, the β-d-manno-heptoses are cross-kingdom, small-molecule, pathogen-associated molecular patterns that activate the ALPK1-dependent innate immune signaling cascade.