IFN-inducible GTPases and immunity to intracellular pathogens

Immunopotentiating effect of lentinan on chicks and its inhibitory effect on Marek's disease virus infection

Marek's disease virus (MDV) is a significant tumorigenic virus that causes severe immunosuppression in chickens. Lentinan (LNT) is an immunomodulator containing β-glucans and is widely used in areas such as antiviral, anticancer, and immune regulation. To investigate the immunomodulatory effects of LNT on specific pathogen-free (SPF) chicks and its potential to inhibit MDV infection, we conducted an MDV challenge experiment and observed the immune-enhancing effect of LNT on SPF chicks. The results showed that LNT promoted the growth and development of SPF chicks and induced the upregulation of cytokines such as Mx protein, interferon-γ (INF-γ), tumor necrosis factor-α (TNF-α), and interleukin-2 (IL-2). The specific gravity of CD4+ T-lymphocytes and CD8+ T-lymphocytes and their ratios were also significantly upregulated. Prophylactic use of LNT inhibited MDV replication in lymphocytes, liver, and spleen. It also alleviated MDV-induced weight loss and hepatosplenomegaly in SPF chicks. The present study confirms that LNT can enhance the levels of innate and cellular immunity in SPF chicks and contributes to the inhibition of MDV replication in vivo and mitigation of immune organ damage in chicks due to MDV infection. This provides an adjunctive measure for better control of MDV infection.

Guanylate-binding protein 5-mediated cell-autonomous immunity suppresses inflammation in dental pulpitis: An in vitro study

AIM

Guanylate-binding protein 5 (GBP5) is an interferon (IFN)-inducible GTPase that plays a crucial role in the cell-autonomous immune response against microbial infections. In this study, we investigated the immunoregulatory role of GBP5 in the pathogenesis of dental pulpitis.

METHODOLOGY

Gene-set enrichment analysis (GSEA) was utilized to evaluate the IFN-γ signalling pathway, and the differential expression of GBP mRNA in normal versus inflamed dental pulp tissues was screened, based on Gene Expression Omnibus (GEO) datasets associated with pulpitis. Both normal pulp tissues and inflamed pulp tissues were used for experiments. The expression of IFNs and GBPs was determined by qRT-PCR. Immunoblotting and double immunofluorescence were performed to examine the cellular localization of GBP5 in dental pulp tissues. For the functional studies, IFN-γ priming or lentivirus vector-delivered shRNA was used to, respectively, overexpress or knock down endogenous GBP5 expression in human dental pulp stem cells (HDPSCs). Subsequently, LPS was used to stimulate HDPSCs (overexpressing or with knocked-down GBP5) to establish an in vitro model of inflammation. qRT-PCR and ELISA were employed to examine the expression of proinflammatory cytokines (IL-6, IL-8 and IL-1β) and cyclooxygenase 2 (COX2). Every experiment has three times of biological replicates and three technical replicates, respectively. Statistical analysis was performed using the Student's t-test and one-way ANOVA, and a p-value of <.05 was considered statistically significant.

RESULTS

GSEA analysis based on the GEO dataset revealed a significant activation of the IFN-γ signalling pathway in the human pulpitis group. Among the human GBPs evaluated, GBP5 was selectively upregulated in inflamed dental pulp tissues and predominantly expressed in dental pulp cells. In vitro experiments demonstrated that IFN-γ robustly induced the expression of GBP5 in HDPSCs. Knockdown of GBP5 expression in HDPSCs significantly amplified the LPS-induced upregulation of inflammatory mediators (IL-6, IL-8, IL-1β and COX2) both with and without IFN-γ priming.

CONCLUSION

Our findings demonstrated that GBP5 partook in the pathogenesis of dental pulpitis. The involvement of GBP5 in pulpitis appeared to coordinate the regulation of inflammatory cytokines. Knockdown of GBP5 contributed to the exacerbation of LPS-mediated inflammation.

GBP2 upregulated in LPS-stimulated macrophages-derived exosomes accelerates septic lung injury by activating epithelial cell NLRP3 signaling

Macrophages infiltration is a crucial factor causing Sepsis-associated acute lung injury (ALI). Accumulating evidence suggests macrophages-alveolar epithelial cells communication is proven to be critical in ALI. However, little is known regarding how activated macrophages regulated sepsis-associated ALI. To explore the role of macrophages-alveolar epithelial cells communication in the ALI process, our data revealed that Lipopolysaccharides-induced macrophages-derived exosomes (L-Exo) induced sepsis-associated ALI and caused alveolar epithelial cells damage. Moreover, Guanylate-binding protein 2 (GBP2) was significantly upregulated in L-Exo, and NLRP3 inflammasomes was the direct target of GBP2. Further experimentation showed that GBP2 inhibition in vitro and in vivo reserves L-Exo effects, while GBP2 overexpression in vitro and in vivo promotes L-Exo effects. These results demonstrated that L-Exo contains excessive GBP2 and promotes inflammation through targeting NLRP3 inflammasomes, which induced alveolar epithelial cells dysfunction and pyroptosis. These findings demonstrate that L-Exo exerted a deleterious effect on ALI by regulating the GBP2/NLRP3 axis, which might provide new insight on ALI prevention and treatment.

Human GBP1 facilitates the rupture of the Legionella-containing vacuole and inflammasome activation

IMPORTANCE

Inflammasomes are essential for host defense against intracellular bacterial pathogens like Legionella, as they activate caspases, which promote cytokine release and cell death to control infection. In mice, interferon (IFN) signaling promotes inflammasome responses against bacteria by inducing a family of IFN-inducible GTPases known as guanylate-binding proteins (GBPs). Within murine macrophages, IFN promotes the rupture of the Legionella-containing vacuole (LCV), while GBPs are dispensable for this process. Instead, GBPs facilitate the lysis of cytosol-exposed Legionella. In contrast, the functions of IFN and GBPs in human inflammasome responses to Legionella are poorly understood. We show that IFN-γ enhances inflammasome responses to Legionella in human macrophages. Human GBP1 is required for these IFN-γ-driven inflammasome responses. Furthermore, GBP1 co-localizes with Legionella and/or LCVs in a type IV secretion system (T4SS)-dependent manner and promotes damage to the LCV, which leads to increased exposure of the bacteria to the host cell cytosol. Thus, our findings reveal species- and pathogen-specific differences in how GBPs function to promote inflammasome responses.

The GTPase activity and isoprenylation of Swine GBP1 are critical for inhibiting the production of Japanese Encephalitis Virus

Japanese encephalitis virus (JEV) is a flavivirus that cause severe neurological deficits. The guanylate-binding protein 1 (GBP1) gene is an interferon-stimulated gene and exerts antiviral functions on many RNA and DNA viruses via diverse mechanisms, however, the roles and the action modes of GBP1 in the antiviral effect on the production of JEV RNA and infectious virions remain to be clarified. In this study, we found that the RNA levels of swine GBP1 (sGBP1) in PK15 cells were up-regulated at the late stage of JEV infection. The overexpression of sGBP1 significantly inhibited the production of JEV while the knockdown of sGBP1 promoted the production of JEV. The GTPase activity and isoprenylation of sGBP1 both are critical for anti-JEV activity. The GTPase activity of sGBP1 is responsible for inhibiting the production of JEV genomic RNA. The isoprenylation of sGBP1 inhibited the expression and cleavage of JEV prM to decrease the yields of infectious virions, which may be associated with the interaction between sGBP1 and cellular proprotein convertase furin. Taken together, the study dissected the action modes of sGBP1with potent anti-JEV activity in more details.

Structural basis of IRGB10 oligomerization by GTP hydrolysis

Immunity-related GTPase B10 (IRGB10) is a crucial member of the interferon (IFN)-inducible GTPases and plays a vital role in host defense mechanisms. Following infection, IRGB10 is induced by IFNs and functions by liberating pathogenic ligands to activate the inflammasome through direct disruption of the pathogen membrane. Despite extensive investigation into the significance of the cell-autonomous immune response, the precise molecular mechanism underlying IRGB10-mediated microbial membrane disruption remains elusive. Herein, we present two structures of different forms of IRGB10, the nucleotide-free and GppNHp-bound forms. Based on these structures, we identified that IRGB10 exists as a monomer in nucleotide-free and GTP binding states. Additionally, we identified that GTP hydrolysis is critical for dimer formation and further oligomerization of IRGB10. Building upon these observations, we propose a mechanistic model to elucidate the working mechanism of IRGB10 during pathogen membrane disruption.

Machine learning-based construction of immunogenic cell death-related score for improving prognosis and response to immunotherapy in melanoma

BACKGROUND

Immunogenic cell death (ICD) is a form of regulated cell death (RCD) which could drive the activation of the innate and adaptive immune responses. In this work, we aimed to develop an ICD-related signature to facilitate the assessment of prognosis and immunotherapy response for melanoma patients.

METHODS

A set of machine learning methods, including consensus clustering, non-negative matrix factorization (NMF) method and least absolute shrinkage and selection operator (LASSO) logistic regression model, and bioinformatics analytic tools were integrated to construct an ICD-related risk score (ICDscore). CIBERSORT and ESTIMATE algorithm were used to evaluate the infiltration of immune cells. The 'pRRophetic' package in R and 6 cohorts of melanoma patients receiving immunotherapy were used for therapy sensitivity analyses. The predictive performance between ICDscore with other mRNA signatures were also compared.

RESULTS

The ICDscore could predict prognosis and immunotherapy response in multiple cohorts, and displayed superior performance than other forms of cell death-related signatures or 52 published signatures. The melanoma patients with low ICDscore were marked with high infiltration of immune cells, high expression of immune checkpoint inhibitor-related genes, and increased tumor mutation burden.

CONCLUSIONS

In conclusion, we constructed a stable and robust ICD-related signature for evaluating the prognosis and benefits of immunotherapy, and it could serve as a promising tool to guide decision-making and surveillance for individual melanoma patients.

Functional cross-species conservation of guanylate-binding proteins in innate immunity

Guanylate binding proteins (GBPs) represent an evolutionary ancient protein family widely distributed among eukaryotes. They are interferon (IFN)-inducible guanosine triphosphatases that belong to the dynamin superfamily. GBPs are known to have a major role in the cell-autonomous innate immune response against bacterial, parasitic and viral infections and are also involved in inflammasome activation. Evolutionary studies depicted that GBPs present a pattern of gain and loss of genes in each family with several genes pseudogenized and some genes more divergent, indicative for the birth-and-death evolution process. Most species harbor large GBP gene clusters encoding multiple paralogs. Previous functional studies mainly focused on mouse and human GBPs, but more data are becoming available, broadening the understanding of this multifunctional protein family. In this review, we will provide new insights and give a broad overview about GBP evolution, conservation and their roles in all studied species, including plants, invertebrates and vertebrates, revealing how far the described features of GBPs can be transferred to other species.

Proteomics Profiling Reveals Regulation of Immune Response to Salmonella enterica Serovar Typhimurium Infection in Mice

Regulation of the immune response to Salmonella enterica serovar Typhimurium (S. Typhimurium) infection is a complex process, influenced by the interaction between genetic and environmental factors. Different inbred strains of mice exhibit distinct levels of resistance to S. Typhimurium infection, ranging from susceptible (e.g., C57BL/6J) to resistant (e.g., DBA/2J) strains. However, the underlying molecular mechanisms contributing to the host response remain elusive. In this study, we present a comprehensive proteomics profiling of spleen tissue from C57BL/6J and DBA/2J strains with different doses of S. Typhimurium infection by tandem mass tag labeling coupled with two-dimensional liquid chromatography-tandem mass spectrometry (TMT-LC/LC-MS/MS). We identified and quantified 3,986 proteins, resulting in 475 differentially expressed proteins (DEPs) between C57BL/6J and DBA/2J strains. Functional enrichment analysis unveiled that the mechanisms of innate immune responses to S. Typhimurium infection could be associated with several signaling pathways, including the interferon (IFN) signaling pathway. We experimentally validated the roles of the IFN signaling pathway in the innate immune response to S. Typhimurium infection using an IFN-γ neutralization assay. We further illustrated the importance of macrophage and proinflammatory cytokines in the mechanisms underlying the resistance to S. Typhimurium using quantitative reverse transcription-PCR (qRT-PCR). Taken together, our results provided new insights into the genetic regulation of the immune response to S. Typhimurium infection in mice and might lead to the discovery of potential protein targets for controlling salmonellosis.

Significant alteration of IFN stimulated genes expression in MA104 cells infected with bovine rotavirus RF strain

The pattern recognition receptors (PRRs) trigger signaling cascades, such as nuclear factor kappa B (NF-κB) and interferon regulatory factors (IRFs). Rotavirus (RV) countermeasures against innate responses and understanding of these processes will improve our knowledge regarding immunopathogenesis of RV infection. In this study, we investigated the effect of RV RF strain on the important ISG candidate genes engaging in virus infections for which little information is known in RV RF strain. To this end, MA104 cells were mock/infected with RF followed by incubation in the presence or absence of IFN-α and the expression of MX1, OAS1, STAT1, ISG15, and ISG56 mRNA was analyzed by real-time PCR. All of ISGs' mRNAs showed higher expression levels in IFN I treated cells compared to virus-infected cells except for ISG56. Infecting the cells with RV and treatment with IFN type I led to overexpression of ISG56 compared to cells were either infected with the virus or only treated with IFN I. In conclusion, we showed that the RV RF strain efficiently blocks type I IFN-induced gene expression particularly ISG15, MX1, STAT, and OSA1 as antiviral proteins. Furthermore, viruses may use some ISGs such as ISG 56 to regulate IFN I signaling pathway, negatively.

The proportion of C1q-high and ISG15-high monocytes in the skin of patients with Behçet disease

Behçet disease (BD) is a chronic systemic vasculitis that is clinically characterized by recurrent oral ulcers, genital ulcers, uveitis, and skin lesions. Here, we conducted bulk RNA-seq of skin samples from 4 BD patients and 4 normal controls (NCs). A total of 260 differentially expressed genes (DEGs), including 99 upregulated and 161 downregulated genes, were detected in the skin lesions of BD patients compared to NCs. These DEGs were mainly enriched in the following biological processes: the activation and migration of immune cells, the release of proinflammatory factors, and the IFN-γ signaling pathway. The top upregulated DEGs were CXCL10, CXCL9, FCGR3A, GBP5, GBP4, LILRB2, ADIPOQ, PLIN1, SLC43A2, and MYO1G. Using the deconvolution method CIBERSORT, we analyzed the immune cells subtypes in the skin of BD by integrating the single cell RNA-seq data from PBMC (GSE198616) and bulk RNA-seq data of skin. There was a higher proportion of C1q+ and ISG15 + monocyte subtypes in skin of BD. IHC staining of CD14 and CD16 showed that the monocyte number increased in the skin of BD. IF staining confirmed there was a higher proportion of the C1Q + Mono and ISG15 + Mono subsets in the skin of BD patients. Moreover, we analyzed the average expression level of the top upregulated genes in immune cell types found in PBMC from BD patients and NCs. Almost all the top upregulated genes expressed in monocytes. CXCL10 was specifically expressed in ISG15 + monocyte, and GBP5, GBP4 and IFI44L were expressed more strongly in ISG15 + monocytes. LILRB2 was expressed more strongly in CD16⁺ monocytes and C1Q + monocytes. In conclusion, our study identified that the IFN-γ pathway was activated in skin of BD and the proportion of C1q+ and ISG15 + monocyte subtype increased in the skin of BD.

STING activation promotes robust immune response and NK cell-mediated tumor regression in glioblastoma models

Immunotherapy has had a tremendous impact on cancer treatment in the past decade, with hitherto unseen responses at advanced and metastatic stages of the disease. However, the aggressive brain tumor glioblastoma (GBM) is highly immunosuppressive and remains largely refractory to current immunotherapeutic approaches. The stimulator of interferon genes (STING) DNA sensing pathway has emerged as a next-generation immunotherapy target with potent local immune stimulatory properties. Here, we investigated the status of the STING pathway in GBM and the modulation of the brain tumor microenvironment (TME) with the STING agonist ADU-S100. Our data reveal the presence of STING in human GBM specimens, where it stains strongly in the tumor vasculature. We show that human GBM explants can respond to STING agonist treatment by secretion of inflammatory cytokines. In murine GBM models, we show a profound shift in the tumor immune landscape after STING agonist treatment, with massive infiltration of the tumor-bearing hemisphere with innate immune cells including inflammatory macrophages, neutrophils, and natural killer (NK) populations. Treatment of established murine intracranial GL261 and CT-2A tumors by biodegradable ADU-S100-loaded intracranial implants demonstrated a significant increase in survival in both models and long-term survival with immune memory in GL261. Responses to treatment were abolished by NK cell depletion. This study reveals therapeutic potential and deep remodeling of the TME by STING activation in GBM and warrants further examination of STING agonists alone or in combination with other immunotherapies such as cancer vaccines, chimeric antigen receptor T cells, NK therapies, and immune checkpoint blockade.

Immune tolerance of food is mediated by layers of CD4+ T cell dysfunction

Gastrointestinal health depends on the adaptive immune system tolerating the foreign proteins in food^1,2. This tolerance is paradoxical because the immune system normally attacks foreign substances by generating inflammation. Here we addressed this conundrum by using a sensitive cell enrichment method to show that polyclonal CD4⁺ T cells responded to food peptides, including a natural one from gliadin, by proliferating weakly in secondary lymphoid organs of the gut-liver axis owing to the action of regulatory T cells. A few food-specific T cells then differentiated into T follicular helper cells that promoted a weak antibody response. Most cells in the expanded population, however, lacked canonical T helper lineage markers and fell into five subsets dominated by naive-like or T follicular helper-like anergic cells with limited capacity to form inflammatory T helper 1 cells. Eventually, many of the T helper lineage-negative cells became regulatory T cells themselves through an interleukin-2-dependent mechanism. Our results indicate that exposure to food antigens causes cognate CD4⁺ naive T cells to form a complex set of noncanonical hyporesponsive T helper cell subsets that lack the inflammatory functions needed to cause gut pathology and yet have the potential to produce regulatory T cells that may suppress it.

Control of innate immunity by the cGAS‐STING pathway

Within the cytoplasm of mammalian cells is a protein called cyclic GMP-AMP synthase (cGAS), which acts to defend against infection and other threats to the host. cGAS operates in this manner through its ability to detect a molecular occurrence that should not exist in healthy cells - the existence of DNA in the cytosol. Upon DNA binding, cGAS synthesizes cyclic GMP-AMP (cGAMP), a cyclic dinucleotide that activates the endoplasmic reticulum-localized protein stimulator of interferon genes (STING). STING-mediated signaling culminates in host defensive responses typified by inflammatory cytokine and interferon expression, and the induction of autophagy. Studies over the past several years have established a consensus in the field of the enzymatic activities of cGAS in vitro, as it relates to DNA-induced production of cGAMP. However, much additional work is needed to understand the regulation of cGAS functions within cells, where multiple sources of DNA can create a problem of self and non-self discrimination. In this review, we provide an overview of how the cGAS-STING pathway mediates innate immune responses during infection and other cellular stresses. We then highlight recent progress in the understanding of the increasingly diverse ways in which this DNA-sensing machinery is regulated inside cells, including how cGAS remains inactive to host-derived DNA under conditions of homeostasis.

Lower Expression of GBP2 Associated With Less Immune Cell Infiltration and Poor Prognosis in Skin Cutaneous Melanoma (SKCM)

Guanylate binding protein 2 (GBP2) could bind to guanine nucleotides (GMP, GDP, and GTP) and exhibits antiviral activity against influenza virus through the innate immune response. Some researchers have demonstrated that the value of GBP2 in predicting the prognosis of multiple cancers and the complex correlation with immune response. However, the correlation of GBP2 to prognosis and immune cell infiltration level were unknown in skin cutaneous melanoma (SKCM). The GBP2 expression in multiple cancers were evaluated through Tumor Immune Estimation Resource (TIMER) and Oncomine. We also evaluated the influence of GBP2 on overall survival in multiple caners through GEPIA, TIMER, and tissue microarray. The correlation between GBP2 expression level and immune cell or gene markers of immune infiltration level was explored on TIMER and GEPIA. Gene set enrichment analysis was performed using the TCGA dataset. The GBP2 expression level represented a significant reduction and the GBP2 expression was lower compared with the SKCM-Metastasis with P<0.01. Lower GBP2 expression was significantly correlated with the poor overall survival of SKCM patients. Simultaneously, higher GBP2 expression predicted the better SKCM-free survival with P=0.019. GBP2 expression was positively correlated with the infiltration cells of B-cell, CD8+ T-cell, CD4+ T-cell, macrophage, neutrophil, and dendritic cell in SKCM. And there was a significant negative correlation between the expression of GBP2 and DNA methylation in the cBioPortal database (P=3.39e-42). Gene set enrichment analysis revealed that GBP2 was closely correlated with multiple pathways of immune response in cancer. In conclusion, Lower expression of GBP2 associated with less immune cell infiltration and poor prognosis in SKCM and the high promoter methylation of GBP2 represented a promising biomarker for poor prognostication in SKCM.

Doxycycline Changes the Transcriptome Profile of mIMCD3 Renal Epithelial Cells

Tetracycline-inducible gene expression systems have been used successfully to study gene function in vivo and in vitro renal epithelial models but the effects of the common inducing agent, doxycycline (DOX), on gene expression are not well appreciated. Here, we evaluated the DOX effects on the transcriptome of a widely used renal epithelial cell model, mIMCD3 cells, to establish a reference. Cells were grown on permeable filter supports in the absence and presence of DOX (3 or 6 days), and genome-wide transcriptome profiles were assessed using RNA-Seq. We found DOX significantly altered the transcriptome profile, changing the abundance of 1,549 transcripts at 3 days and 2,643 transcripts at 6 days. Within 3 days of treatment, DOX significantly decreased the expression of multiple signaling pathways (ERK, cAMP, and Notch) that are associated with cell proliferation and differentiation. Genes associated with cell cycle progression were subsequently downregulated in cells treated with DOX for 6 days, as were genes involved in cellular immune response processes and several cytokines and chemokines, correlating with a remarkable repression of genes encoding cell proliferation markers. The results provide new insight into responses of renal epithelial cells to DOX and a establish a resource for DOX-mediated gene expression systems.

The genome of Nautilus pompilius illuminates eye evolution and biomineralization

Nautilus is the sole surviving externally shelled cephalopod from the Palaeozoic. It is unique within cephalopod genealogy and critical to understanding the evolutionary novelties of cephalopods. Here, we present a complete Nautilus pompilius genome as a fundamental genomic reference on cephalopod innovations, such as the pinhole eye and biomineralization. Nautilus shows a compact, minimalist genome with few encoding genes and slow evolutionary rates in both non-coding and coding regions among known cephalopods. Importantly, multiple genomic innovations including gene losses, independent contraction and expansion of specific gene families and their associated regulatory networks likely moulded the evolution of the nautilus pinhole eye. The conserved molluscan biomineralization toolkit and lineage-specific repetitive low-complexity domains are essential to the construction of the nautilus shell. The nautilus genome constitutes a valuable resource for reconstructing the evolutionary scenarios and genomic innovations that shape the extant cephalopods.

Interferon-induced GTPases orchestrate host cell-autonomous defence against bacterial pathogens

Interferon (IFN)-induced guanosine triphosphate hydrolysing enzymes (GTPases) have been identified as cornerstones of IFN-mediated cell-autonomous defence. Upon IFN stimulation, these GTPases are highly expressed in various host cells, where they orchestrate anti-microbial activities against a diverse range of pathogens such as bacteria, protozoan and viruses. IFN-induced GTPases have been shown to interact with various host pathways and proteins mediating pathogen control via inflammasome activation, destabilising pathogen compartments and membranes, orchestrating destruction via autophagy and the production of reactive oxygen species as well as inhibiting pathogen mobility. In this mini-review, we provide an update on how the IFN-induced GTPases target pathogens and mediate host defence, emphasising findings on protection against bacterial pathogens.

Exploring genetic resistance to infectious salmon anaemia virus in Atlantic salmon by genome-wide association and RNA sequencing

Background

Infectious Salmonid Anaemia Virus (ISAV) causes a notifiable disease that poses a large threat for Atlantic salmon (Salmo salar) aquaculture worldwide. There is no fully effective treatment or vaccine, and therefore selective breeding to increase resistance to ISAV is a promising avenue for disease prevention. Genomic selection and potentially genome editing can be applied to enhance host resistance, and these approaches benefit from improved knowledge of the genetic and functional basis of the target trait. The aim of this study was to characterise the genetic architecture of resistance to ISAV in a commercial Atlantic salmon population and study its underlying functional genomic basis using RNA Sequencing.

Results

A total of 2833 Atlantic salmon parr belonging to 194 families were exposed to ISAV in a cohabitation challenge in which cumulative mortality reached 63% over 55 days. A total of 1353 animals were genotyped using a 55 K SNP array, and the estimate of heritability for the trait of binary survival was 0.13–0.33 (pedigree-genomic). A genome-wide association analysis confirmed that resistance to ISAV was a polygenic trait, albeit a genomic region in chromosome Ssa13 was significantly associated with resistance and explained 3% of the genetic variance. RNA sequencing of the heart of 16 infected (7 and 14 days post infection) and 8 control fish highlighted 4927 and 2437 differentially expressed genes at 7 and 14 days post infection respectively. The complement and coagulation pathway was down-regulated in infected fish, while several metabolic pathways were up-regulated. The interferon pathway showed little evidence of up-regulation at 7 days post infection but was mildly activated at 14 days, suggesting a potential crosstalk between host and virus. Comparison of the transcriptomic response of fish with high and low breeding values for resistance highlighted TRIM25 as being up-regulated in resistant fish.

Conclusions

ISAV resistance shows moderate heritability with a polygenic architecture, but a significant QTL was detected on chromosome 13. A mild up-regulation of the interferon pathway characterises the response to the virus in heart samples from this population of Atlantic salmon, and candidate genes showing differential expression between samples with high and low breeding values for resistance were identified.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07671-6.

Regulation of Synovial Inflammation and Tissue Destruction by Guanylate Binding Protein 5 in Synovial Fibroblasts From Patients With Rheumatoid Arthritis and Rats With Adjuvant-Induced Arthritis

OBJECTIVE

Rheumatoid arthritis synovial fibroblasts (RASFs) are crucial mediators of synovial inflammation and joint destruction. However, their intrinsic immunoregulatory mechanisms under chronic inflammation remain unclear. Thus, the present study was undertaken to understand the role of a newly identified GTPase, guanylate binding protein 5 (GBP-5), in RA pathogenesis.

METHODS

The expression of GBP1-GBP7 transcripts was evaluated using quantitative reverse transcription-polymerase chain reaction in RA synovial tissue or synovial tissue unaffected by RA. Our investigation on transient small interfering RNA (siRNA) knockdown and lentiviral overexpression in human RASFs examined the regulatory role of GBP-5 on proinflammatory cytokine signaling pathways. Unbiased whole transcriptome RNA sequencing analysis was used to assess the impact of GBP-5 on RASF molecular functions. These findings were confirmed using a rat model of adjuvant-induced arthritis (AIA) in vivo.

RESULTS

Among different GBPs evaluated, GBP-5 was selectively up-regulated in RA synovial tissue (P < 0.05; n = 4) and in the joints of rats with AIA (P < 0.05; n = 6) and was significantly induced in human RASFs by interleukin-1β (IL-1β), tumor necrosis factor (TNF), and/or interferon-γ (IFNγ) (P < 0.05; n = 3). Bioinformatics analysis of RNA sequencing data identified cytokine-cytokine receptor signaling as a major function altered by GBP-5, with IL-6 signaling as a primary target. Knockdown of GBP-5 amplified IL-1β-induced IL-6, IL-8, and epithelial neutrophil-activating peptide 78/CXCL5 production by 44%, 54%, 45%, respectively, and matrix metalloproteinase 1 (MMP-1) production by several-fold-effects that reversed with exogenously delivered GBP-5. Lack of GBP-5 increased IFNγ-induced proliferation and migration of human RASFs. GBP-5 knockdown in vivo using intraarticular siRNA exacerbated disease onset, severity, synovitis, and bone destruction in rat AIA.

CONCLUSION

Expressed by RASFs in response to cytokine stimulation, GBP-5 has potential to restore cellular homeostasis and blunt inflammation and tissue destruction in RA.

Interferon-stimulated GTPases in autoimmune and inflammatory diseases: promising role for the guanylate-binding protein (GBP) family

Human IFNs are secreted cytokines shown to stimulate the expression of over one thousand genes. These IFN-inducible genes primarily encode four major protein families, known as IFN-stimulated GTPases (ISGs), namely myxovirus-resistance proteins, guanylate-binding proteins (GBPs), p47 immunity-related GTPases and very large inducible guanosine triphosphate hydrolases (GTPases). These families respond specifically to type I or II IFNs and are well reported in coordinating immunity against some well known as well as newly discovered viral, bacterial and parasitic infections. A growing body of evidence highlights the potential contributory and regulatory roles of ISGs in dysregulated inflammation and autoimmune diseases. Our focus was to draw attention to studies that demonstrate increased expression of ISGs in the serum and affected tissues of patients with RA, SS, lupus, IBD and psoriasis. In this review, we analysed emerging literature describing the potential roles of ISGs, particularly the GBP family, in the context of autoimmunity. We also highlighted the promise and implications for therapeutically targeting IFNs and GBPs in the treatment of rheumatic diseases.

Inducible Guanylate-Binding Protein 7 Facilitates Influenza A Virus Replication by Suppressing Innate Immunity via NF-κB and JAK-STAT Signaling Pathways

Guanylate-binding protein 7 (GBP7) belongs to the GBP family, which plays key roles in mediating innate immune responses to intracellular pathogens. Thus far, GBP7 has been reported to be a critical cellular factor against bacterial infection. However, the relationship between GBP7 and influenza A virus (IAV) replication is unknown. Here, we showed that GBP7 expression was significantly upregulated in the lungs of mice, human peripheral blood mononuclear cells (PBMCs), and A549 cells during IAV infection. Using the CRISPR-Cas9 system and overexpression approaches, it was found that GBP7 knockout inhibited IAV replication by enhancing the expression of IAV-induced type I interferon (IFN), type III IFN, and proinflammatory cytokines. Conversely, overexpression of GBP7 facilitated IAV replication by suppressing the expression of those factors. Furthermore, GBP7 knockout enhanced IAV-induced nuclear factor-κB (NF-κB) activation and phosphorylation of stat1 and stat2; overexpression of GBP7 had the opposite effect. Our data indicated that GBP7 suppresses innate immune responses to IAV infection via NF-κB and JAK-STAT signaling pathways. Taken together, upon IAV infection, the induced GBP7 facilitated IAV replication by suppressing innate immune responses to IAV infection, which suggested that GBP7 serves as a therapeutic target for controlling IAV infection.IMPORTANCE So far, few studies have mentioned the distinct function of guanylate-binding protein 7 (GBP7) on virus infection. Here, we reported that GBP7 expression was significantly upregulated in the lungs of mice, human PBMCs, and A549 cells during IAV infection. GBP7 facilitated IAV replication by suppressing the expression of type I interferon (IFN), type III IFN, and proinflammatory cytokines. Furthermore, it was indicated that GBP7 suppresses innate immune responses to IAV infection via NF-κB and JAK-STAT signaling pathways. Taken together, our results elucidate a critical role of GBP7 in the host immune system during IAV infection.

The validation of the role of several genes related to Bombyx mori nucleopolyhedrovirus infection in vivo

Bombyx mori nucleopolyhedrovirus (BmNPV) is one of primary silkworm pathogens and causes a serious damage of cocoon losses every year. Recent years, many works have been done to clarify the silkworm anti-BmNPV mechanism, and a significant progress has been made in screening and studying of genes and proteins related to BmNPV infection, but several of them lacked the proofs in vivo. In this study, to further validate the function of seven newly reported genes in vivo, including BmAtlatin-n, Bmferritin-heavy chain (BmFerHCH), Bmthymosin (BmTHY), Bmseroin1, Bmseroin2, Bmnuclear hormone receptors 96 (BmNHR96), and BmE3 ubiquitin-protein ligase SINA-like 10 (BmSINAL10), the response of them in the midgut, fat body, and hemolymph of differentially resistant strains (resistant strain YeA and susceptible strain YeB) at 48 h following BmNPV infection were analyzed. The results showed that the relative stable or upregulated expression level of BmAtlatin-n, BmTHY, Bmseroin1, and Bmseroin2 in YeA resistant strain following BmNPV infection further indicated their antiviral role in vivo, compared with susceptible YeB strain. Moreover, the significant downregulation of BmFerHCH, BmNHR96, and BmSINAL10 in both strains following BmNPV infection revealed their role in benefiting virus infection, as well as the upregulation of BmFerHCH in YeB midgut and BmSINAL10 in YeB hemolymph. These data could be used to complementary the proofs of the function of these genes in response to BmNPV infection.

Molecular basis of IRGB10 oligomerization and membrane association for pathogen membrane disruption

Immunity-related GTPase B10 (IRGB10) belongs to the interferon (IFN)-inducible GTPases, a family of proteins critical to host defense. It is induced by IFNs after pathogen infection, and plays a role in liberating pathogenic ligands for the activation of the inflammasome by directly disrupting the pathogen membrane. Although IRGB10 has been intensively studied owing to its functional importance in the cell-autonomous immune response, the molecular mechanism of IRGB10-mediated microbial membrane disruption is still unclear. In this study, we report the structure of mouse IRGB10. Our structural study showed that IRGB10 bound to GDP forms an inactive head-to-head dimer. Further structural analysis and comparisons indicated that IRGB10 might change its conformation to activate its membrane-binding and disruptive functions. Based on this observation, we propose a model of the working mechanism of IRGB10 during pathogen membrane disruption.

Ha et al. present a crystal structure of mouse IRGB10, a mouse interferon-inducible GTPase that mediates bacteriolysis in cell autonomous immunity. With further mutagenesis studies, they show that IRGB10 bound to GDP forms an inactive head-to-head dimer, which changes its conformation to activate its membrane-binding and disruptive functions.

Tupaia guanylate-binding protein 1 interacts with vesicular stomatitis virus phosphoprotein and represses primary transcription of the viral genome

Chinese tree shrews (Tupaia belangeri chinensis) are increasingly used as an alternative experimental animal to non-human primates in studying viral infections. Guanylate-binding proteins (GBP) belong to interferon (IFN)-inducible GTPases and defend the mammalian cell interior against diverse invasive pathogens. Previously, we identified five tree shrew GBP genes (tGBP1, tGBP2, tGBP4, tGBP5, and tGBP7) and found that tGBP1 showed antiviral activity against vesicular stomatitis virus (VSV) and type 1 herpes simplex virus (HSV-1) infections. Here, we showed that the anti-VSV activity of tGBP1 was independent of its GTPase activity and isoprenylation. In response to VSV infection, instead of regulating IFN expression and autophagy, tGBP1 competed with the VSV nucleocapsid (N) protein in binding to the VSV phosphoprotein (VSV-P), leading to the repression of the primary transcription of the VSV genome. These observations constitute the first report of the potential mechanism underlying the inhibition of VSV by GBP1.

Immunity-related GTPase induces lipophagy to prevent excess hepatic lipid accumulation

BACKGROUND & AIMS

Currently, only a few genetic variants explain the heritability of fatty liver disease. Quantitative trait loci (QTL) analysis of mouse strains has identified the susceptibility locus Ltg/NZO (liver triglycerides from New Zealand obese [NZO] alleles) on chromosome 18 as associating with increased hepatic triglycerides. Herein, we aimed to identify genomic variants responsible for this association.

METHODS

Recombinant congenic mice carrying 5.3 Mbp of Ltg/NZO were fed a high-fat diet and characterized for liver fat. Bioinformatic analysis, mRNA profiles and electrophoretic mobility shift assays were performed to identify genes responsible for the Ltg/NZO phenotype. Candidate genes were manipulated in vivo by injecting specific microRNAs into C57BL/6 mice. Pulldown coupled with mass spectrometry-based proteomics and immunoprecipitation were performed to identify interaction partners of IFGGA2.

RESULTS

Through positional cloning, we identified 2 immunity-related GTPases (Ifgga2, Ifgga4) that prevent hepatic lipid storage. Expression of both murine genes and the human orthologue IRGM was significantly lower in fatty livers. Accordingly, liver-specific suppression of either Ifgga2 or Ifgga4 led to a 3-4-fold greater increase in hepatic fat content. In the liver of low-fat diet-fed mice, IFGGA2 localized to endosomes/lysosomes, while on a high-fat diet it associated with lipid droplets. Pulldown experiments and proteomics identified the lipase ATGL as a binding partner of IFGGA2 which was confirmed by co-immunoprecipitation. Both proteins partially co-localized with the autophagic marker LC3B. Ifgga2 suppression in hepatocytes reduced the amount of LC3B-II, whereas overexpression of Ifgga2 increased the association of LC3B with lipid droplets and decreased triglyceride storage.

CONCLUSION

IFGGA2 interacts with ATGL and protects against hepatic steatosis, most likely by enhancing the binding of LC3B to lipid droplets.

LAY SUMMARY

The genetic basis of non-alcoholic fatty liver disease remains incompletely defined. Herein, we identified members of the immunity-related GTPase family in mice and humans that act as regulators of hepatic fat accumulation, with links to autophagy. Overexpression of the gene Ifgga2 was shown to reduce hepatic lipid storage and could be a therapeutic target for the treatment of fatty liver disease.

TYK2 licenses non-canonical inflammasome activation during endotoxemia

The non-canonical inflammasome is an emerging crucial player in the development of inflammatory and neurodegenerative diseases. It is activated by direct sensing of cytosolic lipopolysaccharide (LPS) by caspase-11 (CASP11), which then induces pyroptosis, an inflammatory form of regulated cell death. Here, we report that tyrosine kinase 2 (TYK2), a cytokine receptor-associated kinase, is a critical upstream regulator of CASP11. Absence of TYK2 or its kinase activity impairs the transcriptional induction of CASP11 in vitro and in vivo and protects mice from LPS-induced lethality. Lack of TYK2 or its enzymatic activity inhibits macrophage pyroptosis and impairs release of mature IL-1β and IL-18 specifically in response to intracellular LPS. Deletion of TYK2 in myeloid cells reduces LPS-induced IL-1β and IL-18 production in vivo, highlighting the importance of these cells in the inflammatory response to LPS. In support of our data generated with genetically engineered mice, pharmacological inhibition of TYK2 reduced LPS-induced upregulation of CASP11 in bone marrow-derived macrophages (BMDMs) and of its homolog CASP5 in human macrophages. Our study provides insights into the regulation of CASP11 in vivo and uncovered a novel link between TYK2 activity and CASP11-dependent inflammation.

Functional characterization of an immunity-related GTPase gene in immune defense from obscure puffer (Takifugu obscurus)

Immunity-related GTPases (IRGs) are a family of large interferon-inducible GTPases that function in effective host defense against invading pathogens. IRGs have been extensively studied in mammals for their roles in the elimination of intracellular pathogens; however, their homologs in lower vertebrates are not well known. In this study, an IRG from obscure puffer (Takifugu obscurus), ToIRG, was identified and further characterized for its functional activity. The ToIRG gene encodes a protein of 396 amino acids containing a typical N-terminal GTPase domain with three conserved motifs. Phylogenetic analysis revealed that it has a closer evolutionary relationship with mammalian GKS IRGs. Gene expression profile analysis revealed that ToIRG was ubiquitously expressed in all tested healthy tissues of obscure puffer and upregulated in response to Aeromonas hydrophila or Edwardsiella tarda challenge. The subcellular localization of ToIRG is characterized as condensed forms around the nucleus. Importantly, an antimicrobial assay in vitro suggested that ToIRG enhanced the ability of host cells to resist both intracellular (E. tarda) and extracellular pathogens (A. hydrophila). Taken together, these results provide the functional characterization of obscure puffer IRGs in immune defense, which is the first study to reveal the function of IRGs in bony fish and will provide important insights into the evolutionary divergence of IRGs.

Intraperitoneal injection of IFN-γ restores microglial autophagy, promotes amyloid-β clearance and improves cognition in APP/PS1 mice

Autophagy is a major self-degradative process that maintains cellular homeostasis and function in mammalian cells. Autophagic dysfunction occurs in the early pathogenesis of Alzheimer’s disease (AD) and directly regulates amyloid-β (Aβ) metabolism. Although it has been proven that the cytokine IFN-γ enhances autophagy in macrophage cell lines, whether the signaling cascade is implicated in Aβ degradation in AD mouse models remains to be elucidated. Here, we found that 9 days of the intraperitoneal administration of IFN-γ significantly increased the LC3II/I ratio and decreased the level of p62 in APP/PS1 mice, an AD mouse model. In vitro, IFN-γ protected BV2 cells from Aβ toxicity by upregulating the expressions of Atg7 and Atg5 and the LC3II/I ratio, whereas these protective effects were ablated by interference with Atg5 expression. Moreover, IFN-γ enhanced autophagic flux, probably through suppressing the AKT/mTOR pathway both in vivo and in vitro. Importantly, using intravital two-photon microscopy and fluorescence staining, we found that microglia interacted with exogenous IFN-γ and Aβ, and surrounded Aβ in APP/PS1;CX3CR1-GFP^+/− mice. In addition, IFN-γ treatment decreased the Aβ plaque load in the cortex and hippocampus and rescued cognitive deficits in APP/PS1 mice. Our data suggest a possible mechanism by which the peripheral injection of IFN-γ restores microglial autophagy to induce the phagocytosis of cerebral Aβ, which represents a potential therapeutic approach for the use of exogenous IFN-γ in AD.

An interferon-induced GTP-binding protein, Mx, from the redlip mullet, Liza haematocheila: Deciphering its structural features and immune function

The interferon-induced GTP-binding protein Mx is responsible for a specific antiviral state against a broad spectrum of viral infections that are induced by type-I interferons (IFN α/β) in different vertebrates. In this study, the Mx gene was isolated from the constructed mullet cDNA database. Structural features of mullet Mx (MuMx) were analyzed using different in-silico tools. The pairwise comparison revealed that the MuMx sequence was related to Stegastes partitus Mx with an 83.7% sequence identity, whereas MuMx was clustered into the teleost category in the phylogentic analysis. Sequence alignment showed that the dynamin-type guanine nucleotide-binding domain (G_DYNAMIN_2), central interactive domain (CID), and GTPase effector domain (GED) were conserved among Mx counterparts. The transcriptional expression of MuMx was the highest in blood cells from unchallenged fish. The temporal mRNA profile showed that MuMx expression was significantly elevated in all tissues, including blood, spleen, head kidney, liver, and gills after the injection of polyinosinic-polycytidylic acid (poly I:C) at many time points. Moreover, MuMx expression increased slightly, in the blood, spleen, and head kidney at a few time points after the injection of lipopolysaccharide (LPS) and Lactococcus garvieae (L. garvieae). Results of the subcellular localization analysis confirmed that the MuMx protein was highly expressed in the cytoplasm. The analysis of the gene expression of the viral hemorrhagic septicemia virus (VHSV) under conditions of MuMx overexpression confirmed the significant inhibition of viral transcripts. The cell viability (MTT) assay and VHSV titer quantification with the presence of MuMx indicated a significant reduction in virus replication. Collectively, these findings suggest that Mx is a specific immune-related gene that elicits crucial antiviral functions against viral antigens in the mullet fish.

Innate, adaptive, and cell-autonomous immunity against Toxoplasma gondii infection

Hosts have been fighting pathogens throughout the evolution of all infectious diseases. Toxoplasma gondii is one of the most common infectious agents in humans but causes only opportunistic infection in healthy individuals. Similar to antimicrobial immunity against other organisms, the immune response against T. gondii activates innate immunity and in turn induces acquired immune responses. After activation of acquired immunity, host immune cells robustly produce the proinflammatory cytokine interferon-γ (IFN-γ), which activates a set of IFN-γ-inducible proteins, including GTPases. IFN-inducible GTPases are essential for cell-autonomous immunity and are specialized for effective clearance and growth inhibition of T. gondii by accumulating in parasitophorous vacuole membranes. Recent studies suggest that the cell-autonomous immune response plays a protective role in host defense against not only T. gondii but also various intracellular bacteria. Moreover, the negative regulatory mechanisms of such strong immune responses are also important for host survival after infection. In this review, we will discuss in detail recent advances in the understanding of host defenses against T. gondii and the roles played by cell-autonomous immune responses.

Researchers are extensively studying immune responses to the single-celled parasite Toxoplasma gondii, which infects around one-third of humans, often harmlessly, but can cause life-threatening toxoplasmosis infections in patients with weakened immune systems. Masahiro Yamamoto and Miwa Sasai at Osaka University in Japan review recent advances in understanding the interactions between the immune system and the parasite. They consider non-specific ‘innate’ immune responses and also the ‘acquired’ responses that target specific parts of the parasite, referred to as antigens. Methods that selectively switch off genes in mice are revealing details presumed to also be relevant for humans. Significant molecules, molecular signaling pathways and immune-regulating processes are being identified. Recent studies suggest cell-autonomous immunity, the ability of host cells to defend themselves against attack, plays a significant role in fighting Toxoplasma gondii infection.

Polymorphic Immune Mechanisms Regulate Commensal Repertoire

Environmental influences (infections and diet) strongly affect a host's microbiota. However, host genetics may influence commensal communities, as suggested by the greater similarity between the microbiomes of identical twins compared to non-identical twins. Variability of human genomes and microbiomes complicates the understanding of polymorphic mechanisms regulating the commensal communities. Whereas animal studies allow genetic modifications, they are sensitive to influences known as "cage" or "legacy" effects. Here, we analyze ex-germ-free mice of various genetic backgrounds, including immunodeficient and major histocompatibility complex (MHC) congenic strains, receiving identical input microbiota. The host's polymorphic mechanisms affect the gut microbiome, and both innate (anti-microbial peptides, complement, pentraxins, and enzymes affecting microbial survival) and adaptive (MHC-dependent and MHC-independent) pathways influence the microbiota. In our experiments, polymorphic mechanisms regulate only a limited number of microbial lineages (independently of their abundance). Our comparative analyses suggest that some microbes may benefit from the specific immune responses that they elicit.

Molecular identification and antiviral function of the guanylate-binding protein (GBP) genes in the Chinese tree shrew (Tupaia belangeri chinesis)

Following viral detection and interferons (IFNs) production, several hundreds of IFN-stimulated genes (ISGs) are subsequently induced to act as direct antiviral effectors or regulators of the IFN signaling. The guanylate-binding protein (GBP) family belongs to IFN-inducible GTPases defending the host against a diverse group of invading pathogens such as parasites, bacteria and viruses. The Chinese tree shrew (Tupaia belangeri chinese) has been increasingly used as an alternative experimental animal to primates in studying viral infectious diseases. Hitherto, the tree shrew GBP family has not been characterized. In this study, we identified five tree shrew GBP genes (tGBP1, tGBP2, tGBP4, tGBP5 and tGBP7) and characterized their antiviral activities. All these tGBPs were ubiquitously expressed in heart, spleen, intestines, kidney, liver, lung and brain tissues of the tree shrew. IFN-γ treatment of tree shrew primary renal cells (TSPRCs) significantly induced the mRNA expression of tGBPs. Infections with Newcastle disease virus (NDV), encephalomyocarditis virus (EMCV) and type 1 herpes simplex virus (HSV-1) enhanced tGBPs mRNA expression in TSPRCs, but had no effect on the localization of tGBP proteins in the cytoplasm. tGBP1, but not the other four tGBPs, showed antiviral activity against vesicular stomatitis virus (VSV) and HSV-1 infections. Taken together, this study provided the first-hand information of the GBP family members in the Chinese tree shrew, which might assist the development of tree shrew animal model for infectious diseases.

Host immune responses to Toxoplasma gondii

Toxoplasma gondii can infect homoeothermic animals including humans and cause lethal toxoplasmosis in immunocompromised individuals. When hosts are infected with T. gondii, the cells induce immune responses against T. gondii. The pathogen infection is recognized by immune sensors that directly detect T. gondii structural components, leading to production of pro-inflammatory cytokines and chemokines. Antigen-presenting cells such as macrophages and dendritic cells strongly activate T cells and induce development of Th1 cells and antigen-specific killer CD8 T cells. These T cells and Group 1 innate lymphoid cells are main producers of IFN-γ, which robustly stimulates cell-autonomous immunity in cells infected with T. gondii. IFN-γ-inducible effectors such as IFN-inducible GTPases, inducible nitric oxide synthase and indoleamine-2,3-dioxygenase differentially play important roles in suppression of T. gondii growth and its direct killing in anti-T. gondii cell-autonomous immune responses. In this review, we will describe our current knowledge of innate, adaptive and IFN-γ-mediated cell-autonomous immunity against T. gondii infection.

Syntaxin 11 regulates the stimulus-dependent transport of Toll-like receptor 4 to the plasma membrane by cooperating with SNAP-23 in macrophages

Syntaxin 11 (stx11) is a soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE) that is selectively expressed in immune cells; however, its precise role in macrophages is unclear. We showed that stx11 knockdown reduces the phagocytosis of Escherichia coli in interferon-γ–activated macrophages. stx11 knockdown decreased Toll-like receptor 4 (TLR4) localization on the plasma membrane without affecting total expression. Plasma membrane–localized TLR4 was primarily endocytosed within 1 h by lipopolysaccharide (LPS) stimulation and gradually relocalized 4 h after removal of LPS. This relocalization was significantly impaired by stx11 knockdown. The lack of TLR4 transport to the plasma membrane is presumably related to TLR4 degradation in acidic endosomal organelles. Additionally, an immunoprecipitation experiment suggested that stx11 interacts with SNAP-23, a plasma membrane–localized SNARE protein, whose depletion also inhibits TLR4 replenishment in LPS-stimulated cells. Using an intramolecular Förster resonance energy transfer (FRET) probe for SNAP-23, we showed that the high FRET efficiency caused by LPS stimulation is reduced by stx11 knockdown. These findings suggest that stx11 regulates the stimulus-dependent transport of TLR4 to the plasma membrane by cooperating with SNAP-23 in macrophages. Our results clarify the regulatory mechanisms underlying intracellular transport of TLR4 and have implications for microbial pathogenesis and immune responses.

Interferon-induced guanylate-binding proteins: Guardians of host defense in health and disease

The role of guanylate-binding proteins in host defense.

Guanylate-binding proteins (GBPs) have recently emerged as central orchestrators of immunity to infection, inflammation, and neoplastic diseases. Within numerous host cell types, these IFN-induced GTPases assemble into large nanomachines that execute distinct host defense activities against a wide variety of microbial pathogens. In addition, GBPs customize inflammasome responses to bacterial infection and sepsis, where they act as critical rheostats to amplify innate immunity and regulate tissue damage. Similar functions are becoming evident for metabolic inflammatory syndromes and cancer, further underscoring the importance of GBPs within infectious as well as altered homeostatic settings. A better understanding of the basic biology of these IFN-induced GTPases could thus benefit clinical approaches to a wide spectrum of important human diseases.

Immune imbalance of global gene expression, and cytokine, chemokine and selectin levels in the brains of offspring with social deficits via maternal immune activation

The murine maternal immune activation (MIA) offspring model enables longitudinal studies to explore aberrant social behaviors similar to those observed in humans. High levels of cytokines, chemokines and cell adhesion molecules (CAM) have been found in the plasma and/or brains of psychiatric patients. We hypothesized that upregulation of the systemic or brain immune response has an augmenting effect by potentially increasing the interplay between the neuronal and immune systems during the growth of the MIA offspring. In this study, a C57BL/6j MIA female offspring model exhibiting social deficits was established. The expression of fetal interferon (IFN)-stimulated (gbp3, irgm1, ifi44), adolescent immunodevelopmental transcription factor (eg, r2, tfap2b), hormone (pomc, hcrt), adult selectin (sell, selp) and neuroligin (nlgn2) genes was altered. Systemic upregulation of endogenous IL-10 occurred at the adult stage, while both IL-1β and IL-6 were increased and persisted in the sera throughout the growth of the MIA offspring. The cerebral IL-6 levels were endogenously upregulated, but both MCP-1 (macrophage inflammatory protein-1) and L-selectin levels were downregulated at the adolescent and/or adult stages. However, the MIA offspring were susceptible to lipopolysaccharide (LPS) stimulation. After reinjecting the MIA offspring with LPS in adulthood, a variety of sera and cerebral cytokines, chemokines and CAMs were increased. Particularly, both MCP-1 and L-selectin showed relatively high expression in the brain compared with the expression levels in phosphate-buffered saline (PBS)-treated offspring injected with LPS. Potentially, MCP-1 was attracted to the L-selectin-mediated immune cells due to augmentation of the immune response following stimulation in MIA female offspring.

Interferon regulatory factor 1-Rab27a regulated extracellular vesicles promote liver ischemia/reperfusion injury

The role and regulators of extracellular vesicle (EV) secretion in hepatic ischemia/reperfusion (IR) injury have not been defined. Rab27a is a guanosine triphosphatase known to control EV release. Interferon regulatory factor 1 (IRF-1) is a transcription factor that plays an important role in liver IR and regulates certain guanosine triphosphatases. However, the relationships among IRF-1, Rab27a, and EV secretion are largely unknown. Here, we show induction of IRF-1 and Rab27a both in vitro in hypoxic hepatocytes and in vivo in warm IR and orthotopic liver transplantation livers. Interferon γ stimulation, IRF-1 transduction, or IR promoted Rab27a expression and EV secretion. Meanwhile, silencing of IRF-1 decreased Rab27a expression and EV secretion. Rab27a silencing decreased EV secretion and liver IR injury. Ten putative IRF-1 binding motifs in the 1,692-bp Rab27a promoter region were identified. Chromatin immunoprecipitation and electrophoretic mobility shift assay verified five functional IRF-1 binding motifs, which were confirmed by a Rab27a promoter luciferase assay. IR-induced EVs contained higher oxidized phospholipids (OxPL). OxPLs on the EV surface activated neutrophils through the toll-like receptor 4 pathway. OxPL-neutralizing E06 antibody blocked the effect of EVs and decreased liver IR injury.

CONCLUSION

These findings provide a novel mechanism by which IRF-1 regulates Rab27a transcription and EV secretion, leading to OxPL activation of neutrophils and subsequent hepatic IR injury. (Hepatology 2018;67:1056-1070).

Internally ratiometric fluorescent sensors for evaluation of intracellular GTP levels and distribution

GTP is a major regulator of multiple cellular processes, but tools for quantitative evaluation of GTP levels in live cells have not been available. We report the development and characterization of genetically encoded GTP sensors, which we constructed by inserting a circularly permuted yellow fluorescent protein (cpYFP) into a region of the bacterial G protein FeoB that undergoes a GTP-driven conformational change. GTP binding to these sensors results in a ratiometric change in their fluorescence, thereby providing an internally normalized response to changes in GTP levels while minimally perturbing those levels. Mutations introduced into FeoB to alter its affinity for GTP created a series of sensors with a wide dynamic range. Critically, in mammalian cells the sensors showed consistent changes in ratiometric signal upon depletion or restoration of GTP pools. We show that these GTP evaluators (GEVALs) are suitable for detection of spatiotemporal changes in GTP levels in living cells and for high-throughput screening of molecules that modulate GTP levels.

Association of IFNG gene polymorphisms with pulmonary tuberculosis but not with spinal tuberculosis in a Chinese Han population

Spinal tuberculosis (STB) is an extrapulmonary form of tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb), which accounts for around 2% of all TB cases and can lead to spine degeneration. It is widely accepted that host genetic factors participate in the pathogenesis of active TB, but the factors controlling which TB form will manifest after Mtb infection remain unknown. We hypothesized that a genetic difference may exist between the development of STB and pulmonary tuberculosis (PTB). Here, three single nucleotide polymorphisms (SNPs) in the IFNG gene (rs2069718), IRGM gene (rs10065172), and MBL2 gene (rs11003125) were genotyped among 183 PTB patients, 177 STB patients, and 360 healthy controls from the Chinese Han population. We found that rs2069718 genotypes were significantly associated with PTB (TT, p = 0.007; CT, p = 0.008) but not STB, and the TT genotype (p = 0.046) of rs2069718 were less common in PTB than in STB. In contrast, neither PTB nor STB were found to be associated with rs10065172 and rs11003125. Overall, we found a difference in the rs2069718 genetic distribution between the STB and PTB patients in a Chinese Han population. The rs2069718 TT genotype was associated with a protective role in PTB but not STB development during active Mtb infection.

Evolution of Cell-Autonomous Effector Mechanisms in Macrophages versus Non-Immune Cells

Specialized adaptations for killing microbes are synonymous with phagocytic cells including macrophages, monocytes, inflammatory neutrophils, and eosinophils. Recent genome sequencing of extant species, however, reveals that analogous antimicrobial machineries exist in certain non-immune cells and also within species that ostensibly lack a well-defined immune system. Here we probe the evolutionary record for clues about the ancient and diverse phylogenetic origins of macrophage killing mechanisms and how some of their properties are shared with cells outside the traditional bounds of immunity in higher vertebrates such as mammals.

Strain- and Dose-Dependent Reduction of Toxoplasma gondii Burden in Pigs Is Associated with Interferon-Gamma Production by CD8+ Lymphocytes in a Heterologous Challenge Model

Toxoplasma gondii is a worldwide prevalent parasite of humans and animals. The global infection burden exceeds yearly one million disability-adjusted life years (DALY's) in infected individuals. Therefore, effective preventive measures should be taken to decrease the risk of infection in humans. Although human toxoplasmosis is predominantly foodborne by ingestion of tissue cysts in meat from domestic animals such as pigs, the incidence risk is difficult to estimate due to the lack of screening of animals for infection and insights in location and persistence of the parasite in the tissues. Hence, experimental infections in pigs can provide more information on the risk for zoonosis based on the parasite burden in meat products intended for human consumption and on the immune responses induced by infection. In the present study, homo- and heterologous infection experiments with two distinct T. gondii strains (IPB-LR and IPB-Gangji) were performed. The humoral and cellular immune responses, the presence of viable parasites and the parasite load in edible meat samples were evaluated. In homologous infection experiments the parasite persistence was clearly strain-dependent and inversely correlated with the infection dose. The results strongly indicate a change in the amount of parasite DNA and viable cysts in porcine tissues over time. Heterologous challenge infections demonstrated that IPB-G strain could considerably reduce the parasite burden in the subsequent IPB-LR infection. A strong, however, not protective humoral response was observed against GRA7 and TLA antigens upon inoculation with both strains. The in vitro IFN-γ production by TLA-stimulated PBMCs was correlated with the infection dose and predominantly brought about by CD3⁺CD4^-CD8α^bright T-lymphocytes. The described adaptive cellular and humoral immune responses in pigs are in line with the induced or natural infections in mice and humans. Previous studies underscored the heterogeneity of T. gondii strains and the corresponding virulence factors. These findings suggest the potential of the IPB-G strain to elicit a partially protective immune response and to reduce the parasite burden upon a challenge infection. The IPB-G strain could be used as a promising tool in limiting the number of viable parasites in edible tissues and, hence, in lowering the risk for human toxoplasmosis.

Up-regulation of GBP2 is Associated with Neuronal Apoptosis in Rat Brain Cortex Following Traumatic Brain Injury

Guanylate binding protein 2 (GBP2) is one member of GBP family. Recently, GBP2 has been proposed to be a novel target of anti-cancer drugs. However, the role of GBP2 in the traumatic brain injury (TBI) is very limited. In this study, we sought to define GBP2's role in brain injury. GBP2 protein levels were significantly increased in the brain 3 days after injury, suggesting a functional role for GBP2 in TBI. Neuronal cells overexpressing GBP2 exhibited up-regulation of co-location of GBP2 and NeuN following TBI, suggesting that GBP2 potentiates the neuron apoptosis. To confirm the role of GBP2 in neuron apoptosis process, we employed a highly potent inhibitor of GBP2 (GBP2 RNAi). In H₂O₂-stimulated PC12 cells, in vitro blockade of GBP2 activity using GBP2 RNAi markedly attenuated the neuron apoptosis number. GBP2 RNAi also inhibited the expression levels of active caspase3 and p-Stat1. Furthermore, we found the expression of p-Stat1 in line with GBP2 and GBP2 interacted with p-Stat1 following TBI. The Jak2 inhibitor, AG490 inhibited this interaction and decreased the active caspase3 expression as well as promoted the functional recovery. Taken together, these data suggest that GBP2 RNAi has a protective effect in a rat TBI. This study demonstrates that GBP2 is an important positive regulator of TBI and is a promising therapeutic target for brain injury.

Interferon-induced guanylate-binding proteins in inflammasome activation and host defense

Traditional views of the inflammasome highlight the assembly of pre-existing core components shortly after infection or tissue damage. Emerging work, however, suggests that the inflammasome machinery is also subject to 'tunable' or inducible signals that might accelerate its autocatalytic properties and dictate where inflammasome assembly takes place in the cell. Many of these signals operate downstream of interferon receptors to elicit inflammasome regulators, including a new family of interferon-induced GTPases called 'guanylate-binding proteins' (GBPs). Here we investigate the critical roles of interferon-induced GBPs in directing inflammasome subtype-specific responses and their consequences for cell-autonomous immunity to a wide variety of microbial pathogens. We discuss emerging mechanisms of action and the potential effect of these GBPs on predisposition to sepsis and other infectious or inflammatory diseases.

Toll-like receptors and interferon associated immune factors responses to spring viraemia of carp virus infection in common carp (Cyprinus carpio)

Pattern recognition receptor (PRR) toll-like receptors (TLRs), antiviral agent interferon (IFN) and the effector IFN stimulated genes (ISGs) play a fundamental role in the innate immune response against viruses among all vertebrate classes. Common carp is a host for spring viraemia of carp virus (Rhabdovirus carpio, SVCV), which belong to Rhabdoviridae family. The present in-vivo experiment was conducted to investigate the expression of these innate immune factors in early phase as well as during recovery of SVCV infection by real-time quantitative reverse transcriptase polymerase chain reaction. A less lethal SVCV infection was generated in common carp (Cyprinus carpio) and was sampled at 3, 6, 12 h post infection (hpi), 1, 3, 5, 7 and 10 days post infection (dpi). At 3 hpi, the SVCV N gene was detected in all three fish and all three fish showed a relative fold increase of TLR2, TLR3 and TLR7, IFNa1, ISG15 and Vig1. Viral copies rapidly increased at 12 hpi then remained high until 5 dpi. When viral copy numbers were high, a higher expression of immune genes TLR2, TLR3, TLR7, IFNa1, IFNa2, IFNa1S, IFN regulatory factor 3 (IRF3), IRF7, interleukin 1β (IL1β), IL6, IL10, ADAR, ISG15, Mx1, PKR and Vig1 were observed. Viral copies were gradually reduced in 5 to 10 dpi fish, and also the immune response was considerably reduced but remained elevated. A high degree of correlation was observed between immune genes and viral copy number in each of the sampled fish at 12 hpi. The quick and prolonged elevated expression of the immune genes indicates their crucial role in survival of host against SVCV.

Irgm1 promotes M1 but not M2 macrophage polarization in atherosclerosis pathogenesis and development

BACKGROUND AND AIMS

Atherosclerosis is a chronic inflammatory vascular disease related to macrophages uptake of low-density lipoprotein and their subsequent transformation into foam cells. M1 (inflammatory)/M2 (anti-inflammatory) balance was suggested to impact disease progression. In this study, we investigated whether the immunity related GTPase (Irgm1) regulates macrophage polarization during atherosclerosis development.

METHODS

We used apolipoprotein E (ApoE) knockout and Irgm1 haplodeficient mice and induced atherosclerosis with high-cholesterol diet for the indicated months. Atherosclerotic arteries were collected from patients undergoing vascular surgery, to determine the lesional expression of Irgm1 and distribution of M1/M2 populations.

RESULTS

Our results showed that IRGM/Irgm1 expression was increased in atherosclerotic artery samples (1.7-fold, p=0.0045) compared with non-atherosclerotic arteries, which was consistent with findings in the murine experimental atherosclerosis model (1.9-fold, p=0.0002). IRGM/Irgm1 expression was mostly found in lesional M1 macrophages. Haplodeficiency of Irgm1 in ApoE(-/-) mice resulted in reduced infiltrating M1 macrophages in atheroma (94%, p=0.0002) and delayed development of atherosclerotic plaques. In vitro experiments also confirmed that Irgm1 haplodeficiency reduced iNOS expression of polarized M1 macrophages (81%, p=0.0034), with negligible impact on the M2 phenotype. Moreover, we found that Irgm1 haplodeficiency in mice significantly reduced expression level of M1 function-related transcription factors, interferon regulatory factor (Irf) 5 and Irf8, but not Irf4, an M2-related transcription factor.

CONCLUSIONS

This study shows that Irgm1/IRGM participates in the polarization of M1 macrophage and promotes development of atheroma in murine experimental atherosclerosis.

A newly discovered member of the Atlastin family, BmAtlastin-n, has an antiviral effect against BmNPV in Bombyx mori

Atlastin is a member of the dynamin protein superfamily and it can mediate homotypic fusion of endoplasmic reticulum (ER) membranes, which is required for many biological processes. In this study, a new Atlastin homologous protein, BmAtlastin-n, was characterized in silkworms and was found to contain an N-terminal conserved GTPase domain and a coiled-coil middle domain. BmAtlastin-n is localized in the cytoplasm and enriched in silkworm midgut. Results also showed that overexpression of BmAtlastin-n in BmN-SWU1 cells could enhance resistance to BmNPV. To better confirm its antiviral effect, microRNA was used to knock down the expression of BmAtlastin-n in BmE-SWU1 cells with inducing the reproduction of BmNPV. A transgenic expression vector of BmAtlastin-n was constructed and introduced to silkworm embryos by microinjection. The transgenic silkworm also showed considerable antiviral capacity. In conclusion, these findings demonstrate that BmAtlastin-n plays an important role in BmNPV defense. More importantly, the current study may provide a new clue for Atlastin research.