Interferon-inducible effector mechanisms in cell-autonomous immunity

Construction of Toxoplasma gondii SRS29C nucleic acid vaccine and comparative immunoprotective study of an SRS29C and SAG1 combination

Toxoplasma gondii is an intracellular protozoan parasite that infects all nucleated cells except the red blood cells. Currently, nucleic acid vaccines are being widely investigated in Toxoplasma gondii control, and several nucleic acid vaccine candidate antigens have shown good protection in various studies. The aim of this study was to construct a nucleic acid vaccine with Toxoplasma gondii SRS29C as the target gene. We explored the nucleic acid vaccine with Toxoplasma surface protein SRS29C and the combined gene of SRS29C and SAG1 and evaluated its immunoprotective effect against Toxoplasma gondii. To amplify the gene fragment and clone it to the expression vector, the recombinant plasmid pEGFP-SRS29C was constructed by PCR. Eukaryotic cells were transfected with the plasmid, and the expression of the target protein was assessed using the Western blot method. The level of serum IgG was determined via ELISA, and the splenic lymphocyte proliferation ability was detected using the CCK-8 method. The percentages of CD4+ and CD8+ T cells were measured by flow cytometry. Mice were immunised three times with single-gene nucleic acid vaccine and combination vaccine. Splenic lymphocytokine expression was determined using ELISA kits. The mice's survival time was monitored and recorded during an in vivo insect assault experiment, and the vaccine's protective power was assessed. The outcomes showed that PCR-amplification of an SRS29C gene fragment was successful. The 4,733-bp vector fragment and the 1,119-bp target segment were both recognised by double digestion. Additionally, after transfection of the recombinant plasmid pEGFP-SRS29C, Western blot examination of the extracted protein revealed the presence of a target protein strip at 66 kDa. The test results demonstrated that the IgG content in the serum of the pEGFP-SRS29C group and the co-immunization group was significantly higher than that of the PBS group and the empty vector group. The IgG potency induced by the co-immunization group was higher than that of the pEGFP-SRS29C group and the pEGFP-SAG1 group, the number of splenic lymphocyte proliferation number was higher than that of the PBS group and the empty vector group. The CD4+/CD8+ T ratio was higher than that of the PBS group and the empty vector group. The expression of IFN-γ and TNF-α in the splenocytes of the pEGFP-SRS29C group and the combined immunisation group was significantly higher following antigen stimulation. In the worm attack experiments, mice in the PBS and empty vector groups perished within 9 days of the worm attack, whereas mice in the pEGFP-SRS29C group survived for 18 days, mice in the pEGFP-SAG1 group survived for 21 days, and mice in the co-immunization group survived for 24 days. This demonstrates that the constructed Toxoplasma gondii nucleic acid vaccine pEGFP-SRS29C and the combined gene vaccine can induce mice to develop certain humoral and cellular immune responses, and enhance their ability to resist Toxoplasma gondii infection.

The role of AbaI quorum sensing molecule synthase in host cell inflammation induced by Acinetobacter baumannii and its effect on zebrafish infection model

Acinetobacter baumannii is currently one of the most important opportunistic pathogens causing severe nosocomial infections worldwide. Quorum Sensing (QS) system is a widespread mechanism in bacteria to coordinate group behavior by sensing the density of bacterial populations and affect eukaryotic host cell. In Acinetobacter baumannii, AbaI protein is used as QS molecule synthetase to synthesize N- acyl homoserine lactones (AHLs). Currently, QS has made great progress in the study of drug resistance, but there is still a lack of complete understanding of its damage to host cells after adhesion and invasion. Thus, in this study, we examined the effects of abaI mutant (ΔabaI) on the functions of adhesion and invasion, cell viability, inflammation, apoptosis in A. baumannii infected A549 cells, to evaluate the effects of ΔabaI in a zebrafish model. We found the group infected with ΔabaI increased cell viability, reduced adhesion and invasion, cell injury, inflammatory cytokine production and apoptosis. By RNA-Seq, we explored the possibility that abaI stimulated A549 cells inflammation by A. baumannii infection via TLR4/MAPK signaling pathway. In addition, the ΔabaI significantly reduced pathogenicity and recruitment to neutrophils in zebrafish. These observations suggest that abaI plays a major role in A. baumannii infection.

Loss of RBM45 inhibits breast cancer progression by reducing the SUMOylation of IRF7 to promote IFNB1 transcription

Type I interferons exhibit anti-proliferative and anti-cancer activities, but their detailed regulatory mechanisms in cancer have not been fully elucidated yet. RNA binding proteins are master orchestrators of gene regulation, which are closely related to tumor progression. Here we show that the upregulated RNA binding protein RBM45 correlates with poor prognosis in breast cancer. Depletion of RBM45 suppresses breast cancer progression both in cultured cells and xenograft mouse models. Mechanistically, RBM45 ablation inhibits breast cancer progression through regulating type I interferon signaling, particularly by elevating IFN-β production. Importantly, RBM45 recruits TRIM28 to IRF7 and stimulates its SUMOylation, thereby repressing IFNB1 transcription. Loss of RBM45 reduced the SUMOylation of IRF7 by reducing the interaction between TRIM28 and IRF7 to promote IFNB1 transcription, leading to the inhibition of breast cancer progression. Taken together, our finding uncovers a vital role of RBM45 in modulating type I interferon signaling and cancer aggressive progression, implicating RBM45 as a potential therapeutic target in breast cancer.

LncRNA Nostrill promotes interferon-γ-stimulated gene transcription and facilitates intestinal epithelial cell-intrinsic anti-Cryptosporidium defense

Intestinal epithelial cells possess the requisite molecular machinery to initiate cell-intrinsic defensive responses against intracellular pathogens, including intracellular parasites. Interferons(IFNs) have been identified as cornerstones of epithelial cell-intrinsic defense against such pathogens in the gastrointestinal tract. Long non-coding RNAs (lncRNAs) are RNA transcripts (>200 nt) not translated into protein and represent a critical regulatory component of mucosal defense. We report here that lncRNA Nostrill facilitates IFN-γ-stimulated intestinal epithelial cell-intrinsic defense against infection by Cryptosporidium, an important opportunistic pathogen in AIDS patients and a common cause of diarrhea in young children. Nostrill promotes transcription of a panel of genes controlled by IFN-γ through facilitating Stat1 chromatin recruitment and thus, enhances expression of several genes associated with cell-intrinsic defense in intestinal epithelial cells in response to IFN-γ stimulation, including Igtp, iNos, and Gadd45g. Induction of Nostrill enhances IFN-γ-stimulated intestinal epithelial defense against Cryptosporidium infection, which is associated with an enhanced autophagy in intestinal epithelial cells. Our findings reveal that Nostrill enhances the transcription of a set of genes regulated by IFN-γ in intestinal epithelial cells. Moreover, induction of Nostrill facilitates the IFN-γ-mediated epithelial cell-intrinsic defense against cryptosporidial infections.

African swine fever virus pB475L evades host antiviral innate immunity via targeting STAT2 to inhibit IFN-I signaling

African swine fever virus (ASFV) causes severe disease in domestic pigs and wild boars, seriously threatening the development of the global pig industry. Type I interferon (IFN-I) is an important component of innate immunity, inducing the transcription and expression of antiviral cytokines by activating Janus-activated kinase-signal transducer and activator of transcription (STAT). However, the underlying molecular mechanisms by which ASFV antagonizes IFN-I signaling have not been fully elucidated. Therefore, using coimmunoprecipitation, confocal microscopy, and dual luciferase reporter assay methods, we investigated these mechanisms and identified a novel ASFV immunosuppressive protein, pB475L, which interacts with the C-terminal domain of STAT2. Consequently, pB475L inhibited IFN-I signaling by inhibiting STAT1 and STAT2 heterodimerization and nuclear translocation. Furthermore, we constructed an ASFV-B475L7PM mutant strain by homologous recombination, finding that ASFV-B475L7PM attenuated the inhibitory effects on IFN-I signaling compared to ASFV-WT. In summary, this study reveals a new mechanism by which ASFV impairs host innate immunity.

MAVS disruption impairs downstream signaling and results in higher virus replication levels of salmonid alphavirus subtype 3 but not infectious pancreatic necrosis virus in vitro

The mitochondrial anti-viral signaling (MAVS) protein is an intermediary adaptor protein of retinoic acid-inducible gene-1 (RIG-I) like receptor (RLR) signaling, which activates the transcription factor interferon (IFN) regulatory factor 3 (IRF3) and NF-kB to produce type I IFNs. MAVS expression has been reported in different fish species, but few studies have shown its functional role in anti-viral responses to fish viruses. In this study, we used the transcription activator-like effector nuclease (TALEN) as a gene editing tool to disrupt the function of MAVS in Chinook salmon (Oncorhynchus tshawytscha) embryonic cells (CHSE) to understand its role in induction of interferon I responses to infections with the (+) RNA virus salmonid alphavirus subtype 3 (SAV-3), and the dsRNA virus infectious pancreatic necrosis virus (IPNV) infection. A MAVS-disrupted CHSE clone with a 7-aa polypeptide (GVFVSRV) deletion mutation at the N-terminal of the CARD domain infected with SAV-3 resulted in significantly lower expression of IRF3, IFNa, and ISGs and increased viral titer (1.5 log10) compared to wild-type. In contrast, the IPNV titer in MAVS-disrupted cells was not different from the wild-type. Furthermore, overexpression of salmon MAVS in MAVS-disrupted CHSE cells rescued the impaired type I IFN-mediated anti-viral effect against SAV-3.

Bacteria colonization and gene expression related to immune function in colon mucosa is associated with growth in neonatal calves regardless of live yeast supplementation

BACKGROUND

As Holstein calves are susceptible to gastrointestinal disorders during the first week of life, understanding how intestinal immune function develops in neonatal calves is important to promote better intestinal health. Feeding probiotics in early life may contribute to host intestinal health by facilitating beneficial bacteria colonization and developing intestinal immune function. The objective of this study was to characterize the impact of early life yeast supplementation and growth on colon mucosa-attached bacteria and host immune function.

RESULTS

Twenty Holstein bull calves received no supplementation (CON) or Saccharomyces cerevisiae boulardii (SCB) from birth to 5 d of life. Colon tissue biopsies were taken within 2 h of life (D0) before the first colostrum feeding and 3 h after the morning feeding at d 5 of age (D5) to analyze mucosa-attached bacteria and colon transcriptome. Metagenome sequencing showed that there was no difference in α and β diversity of mucosa-attached bacteria between day and treatment, but bacteria related to diarrhea were more abundant in the colon mucosa on D0 compared to D5. In addition, qPCR indicated that the absolute abundance of Escherichia coli (E. coli) decreased in the colon mucosa on D5 compared to D0; however, that of Bifidobacterium, Lactobacillus, and Faecalibacterium prausnitzii, which could competitively exclude E. coli, increased in the colon mucosa on D5 compared to D0. RNA-sequencing showed that there were no differentially expressed genes between CON and SCB, but suggested that pathways related to viral infection such as "Interferon Signaling" were activated in the colon mucosa of D5 compared to D0.

CONCLUSIONS

Growth affected mucosa-attached bacteria and host immune function in the colon mucosa during the first 5 d of life in dairy calves independently of SCB supplementation. During early life, opportunistic pathogens may decrease due to intestinal environmental changes by beneficial bacteria and/or host immune function. Predicted activation of immune function-related pathways may be the result of host immune function development or suggest other antigens in the intestine during early life. Further studies focusing on the other antigens and host immune function in the colon mucosa are required to better understand intestinal immune function development.

Neutrophils and galectin-3 defend mice from lethal bacterial infection and humans from acute respiratory failure

Respiratory infection by Pseudomonas aeruginosa, common in hospitalized immunocompromised and immunocompetent ventilated patients, can be life-threatening because of antibiotic resistance. This raises the question of whether the host's immune system can be educated to combat this bacterium. Here we show that prior exposure to a single low dose of lipopolysaccharide (LPS) protects mice from a lethal infection by P. aeruginosa. LPS exposure trained the innate immune system by promoting expansion of neutrophil and interstitial macrophage populations distinguishable from other immune cells with enrichment of gene sets for phagocytosis- and cell-killing-associated genes. The cell-killing gene set in the neutrophil population uniquely expressed Lgals3, which encodes the multifunctional antibacterial protein, galectin-3. Intravital imaging for bacterial phagocytosis, assessment of bacterial killing and neutrophil-associated galectin-3 protein levels together with use of galectin-3-deficient mice collectively highlight neutrophils and galectin-3 as central players in LPS-mediated protection. Patients with acute respiratory failure revealed significantly higher galectin-3 levels in endotracheal aspirates (ETAs) of survivors compared to non-survivors, galectin-3 levels strongly correlating with a neutrophil signature in the ETAs and a prognostically favorable hypoinflammatory plasma biomarker subphenotype. Taken together, our study provides impetus for harnessing the potential of galectin-3-expressing neutrophils to protect from lethal infections and respiratory failure.

Hepatocytes and the art of killing Plasmodium softly

The Plasmodium parasites that cause malaria undergo asymptomatic development in the parenchymal cells of the liver, the hepatocytes, prior to infecting erythrocytes and causing clinical disease. Traditionally, hepatocytes have been perceived as passive bystanders that allow hepatotropic pathogens such as Plasmodium to develop relatively unchallenged. However, now there is emerging evidence suggesting that hepatocytes can mount robust cell-autonomous immune responses that target Plasmodium, limiting its progression to the blood and reducing the incidence and severity of clinical malaria. Here we discuss our current understanding of hepatocyte cell-intrinsic immune responses that target Plasmodium and how these pathways impact malaria.

Dynamic control of gene expression by ISGF3 and IRF1 during IFNβ and IFNγ signaling

Type I interferons (IFN-I, including IFNβ) and IFNγ produce overlapping, yet clearly distinct immunological activities. Recent data show that the distinctness of global transcriptional responses to the two IFN types is not apparent when comparing their immediate effects. By analyzing nascent transcripts induced by IFN-I or IFNγ over a period of 48 h, we now show that the distinctiveness of the transcriptomes emerges over time and is based on differential employment of the ISGF3 complex as well as of the second-tier transcription factor IRF1. The distinct transcriptional properties of ISGF3 and IRF1 correspond with a largely diverse nuclear protein interactome. Mechanistically, we describe the specific input of ISGF3 and IRF1 into enhancer activation and the regulation of chromatin accessibility at interferon-stimulated genes (ISG). We further report differences between the IFN types in altering RNA polymerase II pausing at ISG 5' ends. Our data provide insight how transcriptional regulators create immunological identities of IFN-I and IFNγ.

Toxoplasma gondii chitinase-like protein TgCLP1 regulates the parasite cyst burden

Toxoplasma, an important intracellular parasite of humans and animals, causes life-threatening toxoplasmosis in immunocompromised individuals. Although Toxoplasma secretory proteins during acute infection (tachyzoite, which divides rapidly and causes inflammation) have been extensively characterized, those involved in chronic infection (bradyzoite, which divides slowly and is surrounded by a cyst wall) remain uncertain. Regulation of the cyst wall is essential to the parasite life cycle, and polysaccharides, such as chitin, in the cyst wall are necessary to sustain latent infection. Toxoplasma secretory proteins during the bradyzoite stage may have important roles in regulating the cyst wall via polysaccharides. Here, we focused on characterizing the hypothetical T. gondii chitinase, chitinase-like protein 1 (TgCLP1). We found that the chitinase-like domain containing TgCLP1 is partially present in the bradyzoite microneme and confirmed, albeit partially, its previous identification in the tachyzoite microneme. Furthermore, although parasites lacking TgCLP1 could convert from tachyzoites to bradyzoites and make an intact cyst wall, they failed to convert from bradyzoites to tachyzoites, indicating that TgCLP1 is necessary for bradyzoite reactivation. Taken together, our findings deepen our understanding of the molecular basis of recrudescence and could contribute to the development of novel strategies for the control of toxoplasmosis.

Characterization of Neisseria gonorrhoeae colonization of macrophages under distinct polarization states and nutrients environment

Neisseria gonorrhoeae (Ng) is a uniquely adapted human pathogen and the etiological agent of gonorrhea, a sexually transmitted disease. Ng has developed numerous mechanisms to avoid and actively suppress innate and adaptive immune responses. Ng successfully colonizes and establishes topologically distinct colonies in human macrophages and avoids phagocytic killing. During colonization, Ng manipulates the actin cytoskeleton to invade and create an intracellular niche supportive of bacterial replication. The cellular reservoir(s) supporting bacterial replication and persistence in gonorrhea infections are poorly defined. The manner in which gonococci colonize macrophages points to this innate immune phagocyte as a strong candidate for a cellular niche during natural infection. Here we investigate whether nutrients availability and immunological polarization alter macrophage colonization by Ng. Differentiation of macrophages in pro-inflammatory (M1-like) and tolerogenic (M2-like) phenotypes prior to infection reveals that Ng can invade macrophages in all activation states, albeit with lower efficiency in M1-like macrophages. These results suggest that during natural infection, bacteria could invade and grow within macrophages regardless of the nutrients availability and the macrophage immune activation status.

LINC01002 functions as a ceRNA to regulate FRMD8 by sponging miR-4324 for the development of COVID-19

BACKGROUND

Syndrome coronavirus-2 (SARS-CoV-2) has developed various strategies to evade the antiviral impact of type I IFN. Non-structural proteins and auxiliary proteins have been extensively researched on their role in immune escape. Nevertheless, the detailed mechanisms of structural protein-induced immune evasion have not been well elucidated.

METHODS

Human alveolar basal epithelial carcinoma cell line (A549) was stimulated with polyinosinic-polycytidylic acid (PIC) and independently transfected with four structural proteins expression plasmids, including nucleocapsid (N), spike (S), membrane (M) and envelope (E) proteins. By RT-qPCR and ELISA, the structural protein with the most pronounced inhibitory effects on IFN-β induction was screened. RNA-sequencing (RNA-Seq) and two differential analysis strategies were used to obtain differentially expressed genes associated with N protein inhibition of IFN-β induction. Based on DIANA-LncBase and StarBase databases, the interactive competitive endogenous RNA (ceRNA) network for N protein-associated genes was constructed. By combining single-cell sequencing data (GSE158055), lncRNA-miRNA-mRNA axis was further determined. Finally, RT-qPCR was utilized to illustrate the regulatory functions among components of the ceRNA axis.

RESULTS

SARS-CoV-2 N protein inhibited IFN-β induction in human alveolar epithelial cells most significantly compared with other structural proteins. RNA-Seq data analysis revealed genes related to N protein inhibiting IFNs induction. The obtained 858 differentially expressed genes formed the reliable ceRNA network. The function of LINC01002-miR-4324-FRMD8 axis in the IFN-dominated immune evasion was further demonstrated through integrating single-cell sequencing data. Moreover, we validated that N protein could reverse the effect of PIC on LINC01002, FRMD8 and miR-4324 expression, and subsequently on IFN-β expression level. And LINC01002 could regulate the production of FRMD8 by inhibiting miR-4324.

CONCLUSION

SARS-CoV-2 N protein suppressed the induction of IFN-β by regulating LINC01002 which was as a ceRNA, sponging miR-4324 and participating in the regulation of FRMD8 mRNA. Our discovery provides new insights into early intervention therapy and drug development on SARS-CoV-2 infection.

Hepatocyte Intrinsic Innate Antiviral Immunity against Hepatitis Delta Virus Infection: The Voices of Bona Fide Human Hepatocytes

The pathogenesis of viral infection is attributed to two folds: intrinsic cell death pathway activation due to the viral cytopathic effect, and immune-mediated extrinsic cellular injuries. The immune system, encompassing both innate and adaptive immunity, therefore acts as a double-edged sword in viral infection. Insufficient potency permits pathogens to establish lifelong persistent infection and its consequences, while excessive activation leads to organ damage beyond its mission to control viral pathogens. The innate immune response serves as the front line of defense against viral infection, which is triggered through the recognition of viral products, referred to as pathogen-associated molecular patterns (PAMPs), by host cell pattern recognition receptors (PRRs). The PRRs-PAMPs interaction results in the induction of interferon-stimulated genes (ISGs) in infected cells, as well as the secretion of interferons (IFNs), to establish a tissue-wide antiviral state in an autocrine and paracrine manner. Cumulative evidence suggests significant variability in the expression patterns of PRRs, the induction potency of ISGs and IFNs, and the IFN response across different cell types and species. Hence, in our understanding of viral hepatitis pathogenesis, insights gained through hepatoma cell lines or murine-based experimental systems are uncertain in precisely recapitulating the innate antiviral response of genuine human hepatocytes. Accordingly, this review article aims to extract and summarize evidence made possible with bona fide human hepatocytes-based study tools, along with their clinical relevance and implications, as well as to identify the remaining gaps in knowledge for future investigations.

The complete assembly of human LAT1-4F2hc complex provides insights into its regulation, function and localisation

The LAT1-4F2hc complex (SLC7A5-SLC3A2) facilitates uptake of essential amino acids, hormones and drugs. Its dysfunction is associated with many cancers and immune/neurological disorders. Here, we apply native mass spectrometry (MS)-based approaches to provide evidence of super-dimer formation (LAT1-4F2hc)2. When combined with lipidomics, and site-directed mutagenesis, we discover four endogenous phosphatidylethanolamine (PE) molecules at the interface and C-terminus of both LAT1 subunits. We find that interfacial PE binding is regulated by 4F2hc-R183 and is critical for regulation of palmitoylation on neighbouring LAT1-C187. Combining native MS with mass photometry (MP), we reveal that super-dimerization is sensitive to pH, and modulated by complex N-glycans on the 4F2hc subunit. We further validate the dynamic assemblies of LAT1-4F2hc on plasma membrane and in the lysosome. Together our results link PTM and lipid binding with regulation and localisation of the LAT1-4F2hc super-dimer.

ATP-P2X7 signaling mediates brain pathology while contributing to viral control in perinatal Zika virus infection

Zika virus (ZIKV), the causative agent of Zika fever, is a flavivirus transmitted by mosquitoes of the Aedes genus. Zika virus infection has become an international concern due to its association with severe neurological complications such as fetal microcephaly. Viral infection can induce the release of ATP in the extracellular environment, activating receptors sensitized by extracellular nucleotides, such as the P2X7 receptor. This receptor is the primary purinergic receptor involved in neuroinflammation, neurodegeneration, and immunity. In this work, we investigated the role of ATP-P2X7 receptor signaling in Zika-related brain abnormalities. Wild-type mice (WT) and P2X7 receptor-deficient (P2X7-/-) C57BL/6 newborn mice were subcutaneously inoculated with 5 × 106plaque-forming units of ZIKV or mock solution. P2X7 receptor expression increased in the brain of Zika virus-infected mice compared to the mock group. Comparative analyses of the hippocampi from WT and P2X7-/-mice revealed that the P2X7 receptor increased hippocampal damage in CA1/CA2 and CA3 regions. Doublecortin expression decreased significantly in the brains of ZIKV-infected mice. WT ZIKV-infected mice showed impaired motor performance compared to P2X7-/- infected mice. WT ZIKV-infected animals showed increased expression of glial markers GFAP (astrocytes) and IBA-1 (microglia) compared to P2X7-/- infected mice. Although the P2X7 receptor contributes to neuronal loss and neuroinflammation, WT mice were more efficient in controlling the viral load in the brain than P2X7 receptor-deficient mice. This result was associated with higher induction of TNF-α, IFN-β, and increased interferon-stimulated gene expression in WT mice than P2X7-/-ZIKV-infected. Finally, we found that the P2X7 receptor contributes to inhibiting the neuroprotective signaling pathway AKT/mTOR while stimulating the caspase-3 activation, possibly two distinct pathways contributing to neurodegeneration. These findings suggest that ATP-P2X7 receptor signaling contributes to the antiviral response in the brain of ZIKV-infected mice while increasing neuronal loss, neuroinflammation, and related brain abnormalities.

Analysis of intestinal epithelial cell responses to Cryptosporidium highlights the temporal effects of IFN-γ on parasite restriction

The production of IFN-γ is crucial for control of multiple enteric infections, but its impact on intestinal epithelial cells (IEC) is not well understood. Cryptosporidium parasites exclusively infect epithelial cells and the ability of interferons to activate the transcription factor STAT1 in IEC is required for parasite clearance. Here, the use of single cell RNA sequencing to profile IEC during infection revealed an increased proportion of mid-villus enterocytes during infection and induction of IFN-γ-dependent gene signatures that was comparable between uninfected and infected cells. These analyses were complemented by in vivo studies, which demonstrated that IEC expression of the IFN-γ receptor was required for parasite control. Unexpectedly, treatment of Ifng-/- mice with IFN-γ showed the IEC response to this cytokine correlates with a delayed reduction in parasite burden but did not affect parasite development. These data sets provide insight into the impact of IFN-γ on IEC and suggest a model in which IFN-γ signalling to uninfected enterocytes is important for control of Cryptosporidium.

Molecular structure and function of mysterin/RNF213

Mysterin is a large intracellular protein harboring a RING finger ubiquitin ligase domain and is also referred to as RING finger protein 213 (RNF213). The author performed the first molecular cloning of the mysterin gene as the final step in genetic exploration of cerebrovascular moyamoya disease (MMD) and initiated the next round of exploration to understand its molecular and cellular functions. Although much remains unknown, accumulating findings suggest that mysterin functions in cells by targeting massive intracellular structures, such as lipid droplets (LDs) and various invasive pathogens. In the latter case, mysterin appears to directly surround and ubiquitylate the surface of pathogens and stimulate cell-autonomous antimicrobial reactions, such as xenophagy and inflammatory response. To date, multiple mutations causing MMD have been identified within and near the RING finger domain of mysterin; however, their functional relevance remains largely unknown. Besides the RING finger, mysterin harbors a dynein-like ATPase core and an RZ finger, another ubiquitin ligase domain unique to mysterin, while functional exploration of these domains has also just commenced. In this review, the author attempts to summarize the core findings regarding the molecular structure and function of the mysterin protein, with an emphasis on the perspective of MMD research.

Signaling by Type I Interferons in Immune Cells: Disease Consequences

This review addresses interferon (IFN) signaling in immune cells and the tumor microenvironment (TME) and examines how this affects cancer progression. The data reveal that IFNs exert dual roles in cancers, dependent on the TME, exhibiting both anti-tumor activity and promoting cancer progression. We discuss the abnormal IFN signaling induced by cancerous cells that alters immune responses to permit their survival and proliferation.

IFNγ insufficiency during mouse intra-vaginal Chlamydia trachomatis infection exacerbates alternative activation in macrophages with compromised CD40 functions

Chlamydia trachomatis (C.tr), an obligate intracellular pathogen, causes asymptomatic genital infections in women and is a leading cause of preventable blindness. We have developed in vivo mouse models of acute and chronic C. trachomatis genital infection to explore the significance of macrophage-directed response in mediating immune activation/suppression. Our findings reveal that during chronic and repeated C. trachomatis infections, Th1 response is abated while Treg response is enhanced. Additionally, an increase in exhaustion (PD1, CTLA4) and anergic (Klrg3, Tim3) T cell markers is observed during chronic infection. We have also observed that M2 macrophages with low CD40 expression promote Th2 and Treg differentiation leading to sustained C. trachomatis genital infection. Macrophages infected with C. trachomatis or treated with supernatant of infected epithelial cells drive them to an M2 phenotype. C. trachomatis infection prevents the increase in CD40 expression as observed in western blots and flow cytometric analysis. Insufficient IFNγ, as observed during chronic infection, leads to incomplete clearance of bacteria and poor immune activation. C. trachomatis decapacitates IFNγ responsiveness in macrophages via hampering IFNγRI and IFNγRII expression which can be correlated with poor expression of MHC-II, CD40, iNOS and NO release even following IFNγ supplementation. M2 macrophages during C. trachomatis infection express low CD40 rendering immunosuppressive, Th2 and Treg differentiation which could not be reverted even by IFNγ supplementation. The alternative macrophages also harbour high bacterial load and are poor responders to IFNγ, thus promoting immunosuppression. In summary, C. trachomatis modulates the innate immune cells, attenuating the anti-chlamydial functions of T cells in a manner that involves decreased CD40 expression on macrophages.

Interferon- and infectious diseases: Lessons and prospects

Infectious diseases continue to claim many lives. Prevention of morbidity and mortality from these diseases would benefit not just from new medicines and vaccines but also from a better understanding of what constitutes protective immunity. Among the major immune signals that mobilize host defense against infection is interferon-γ (IFN-γ), a protein secreted by lymphocytes. Forty years ago, IFN-γ was identified as a macrophage-activating factor, and, in recent years, there has been a resurgent interest in IFN-γ biology and its role in human defense. Here we assess the current understanding of IFN-γ, revisit its designation as an "interferon," and weigh its prospects as a therapeutic against globally pervasive microbial pathogens.

The conceptual foundations of innate immunity: Taking stock 30 years later

While largely neglected over decades during which adaptive immunity captured most of the attention, innate immune mechanisms have now become central to our understanding of immunology. Innate immunity provides the first barrier to infection in vertebrates, and it is the sole mechanism of host defense in invertebrates and plants. Innate immunity also plays a critical role in maintaining homeostasis, shaping the microbiota, and in disease contexts such as cancer, neurodegeneration, metabolic syndromes, and aging. The emergence of the field of innate immunity has led to an expanded view of the immune system, which is no longer restricted to vertebrates and instead concerns all metazoans, plants, and even prokaryotes. The study of innate immunity has given rise to new concepts and language. Here, we review the history and definition of the core concepts of innate immunity, discussing their value and fruitfulness in the long run.

The Micro-Immunotherapy Medicine 2LPAPI® Displays Immune-Modulatory Effects in a Model of Human Papillomavirus Type-16 L1-Protein Capsid-Treated Human Peripheral Blood Mononuclear Cells and Antiproliferative Effects in a Model of Cervical Cancer Cells

Human papillomavirus (HPV) is the second most common infectious agent causing cancer. Persistent infection with high-risk (HR)-HPV can lead to cervical intra-epithelial neoplasia and cervical carcinomas (CC). While host immune response is necessary for viral clearance, chronic immune activation contributes to a low-grade inflammation that can ultimately lead to carcinogenesis. The micro-immunotherapy medicine (MIM) 2LPAPI® could be a valuable tool to manage the clearance of the virus and reduce the risk of developing CC. In this in vitro study, we aimed to investigate its mode of action. We showed that actives from the MIM increased the IL-6, IFN-γ, and IP-10 secretion in human peripheral blood mononuclear cells (PBMCs) exposed to peptides derived from the HPV-16 capsid (HPV16(L1)). This could reflect an increase in the immune activity toward HPV-16. At the same time, some active substances reduced the lympho-proliferation and the expression of T-cell activation markers. Finally, some of the MIM actives displayed antiproliferative effects in CC-derived HeLa cells under serum-starvation conditions. Altogether, this body of data highlighted for the first time the dual effect of MIM in the framework of HR-HPV infections as a potential (i) immune modulator of HPV16(L1)-treated PBMCs and (ii) antiproliferative agent of HPV-positive CC cells.

Characterization of Neisseria gonorrhoeae colonization of macrophages under distinct polarization states and nutrients environment

Neisseria gonorrhoeae (Ng) is a uniquely adapted human pathogen and the etiological agent of gonorrhea, a sexually transmitted disease. Ng has developed numerous mechanisms to avoid and actively suppress innate and adaptive immune responses. Ng successfully colonizes and establishes topologically distinct colonies in human macrophages and avoids phagocytic killing. During colonization, Ng manipulates the actin cytoskeleton to invade and create an intracellular niche supportive of bacterial replication. The cellular reservoir(s) supporting bacterial replication and persistence in gonorrhea infections are poorly defined. The manner in which gonococci colonize macrophages points to this innate immune phagocyte as a strong candidate for a cellular niche during natural infection. Here we investigate whether nutrients availability and immunological polarization alter macrophage colonization by Ng . Differentiation of macrophages in pro-inflammatory (M1-like) and tolerogenic (M2-like) phenotypes prior to infection reveals that Ng can invade macrophages in all activation states, albeit with lower efficiency in M1-like macrophages. These results suggest that during natural infection, bacteria could invade and grow within macrophages regardless of the nutrients availability and the macrophage immune activation status.

Immunity to Cryptosporidium: insights into principles of enteric responses to infection

Cryptosporidium parasites replicate within intestinal epithelial cells and are an important cause of diarrhoeal disease in young children and in patients with primary and acquired defects in T cell function. This Review of immune-mediated control of Cryptosporidium highlights advances in understanding how intestinal epithelial cells detect this infection, the induction of innate resistance and the processes required for activation of T cell responses that promote parasite control. The development of a genetic tool set to modify Cryptosporidium combined with tractable mouse models provide new opportunities to understand the principles that govern the interface between intestinal epithelial cells and the immune system that mediate resistance to enteric pathogens.

Structural insights into the activation mechanism of antimicrobial GBP1

The dynamin-related human guanylate-binding protein 1 (GBP1) mediates host defenses against microbial pathogens. Upon GTP binding and hydrolysis, auto-inhibited GBP1 monomers dimerize and assemble into soluble and membrane-bound oligomers, which are crucial for innate immune responses. How higher-order GBP1 oligomers are built from dimers, and how assembly is coordinated with nucleotide-dependent conformational changes, has remained elusive. Here, we present cryo-electron microscopy-based structural data of soluble and membrane-bound GBP1 oligomers, which show that GBP1 assembles in an outstretched dimeric conformation. We identify a surface-exposed helix in the large GTPase domain that contributes to the oligomerization interface, and we probe its nucleotide- and dimerization-dependent movements that facilitate the formation of an antimicrobial protein coat on a gram-negative bacterial pathogen. Our results reveal a sophisticated activation mechanism for GBP1, in which nucleotide-dependent structural changes coordinate dimerization, oligomerization, and membrane binding to allow encapsulation of pathogens within an antimicrobial protein coat.

Susceptibility of Toxoplasma gondii to autophagy in human cells relies on multiple interacting parasite loci

IMPORTANCE

Autophagy is a process used by cells to recycle organelles and macromolecules and to eliminate intracellular pathogens. Previous studies have shown that some stains of Toxoplasma gondii are resistant to autophagy-dependent growth restriction, while others are highly susceptible. Although it is known that autophagy-mediated control requires activation by interferon gamma, the basis for why parasite strains differ in their susceptibility is unknown. Our findings indicate that susceptibility involves at least five unlinked parasite genes on different chromosomes, including several secretory proteins targeted to the parasite-containing vacuole and exposed to the host cell cytosol. Our findings reveal that susceptibility to autophagy-mediated growth restriction relies on differential recognition of parasite proteins exposed at the host-pathogen interface, thus identifying a new mechanism for cell-autonomous control of intracellular pathogens.

The aldehyde dehydrogenase ALDH1B1 exerts antiviral effects through the aggregation of the adaptor MAVS

Type I interferons (IFNs) are produced by almost all cell types and play a vital role in host defense against viral infection. Infection with an RNA virus activates receptors such as RIG-I, resulting in the recruitment of the adaptor protein MAVS to the RIG-I-like receptor (RLR) signalosome and the formation of prion-like functional aggregates of MAVS, which leads to IFN-β production. Here, we identified the aldehyde dehydrogenase 1B1 (ALDH1B1) as a previously uncharacterized IFN-stimulated gene (ISG) product with critical roles in the antiviral response. Knockout of ALDH1B1 increased, whereas overexpression of ALDH1B1 restricted, the replication of RNA viruses, such as vesicular stomatitis virus (VSV), Zika virus (ZIKV), dengue virus (DENV), and influenza A virus (IAV). We found that ALDH1B1 localized to mitochondria, where it interacted with the transmembrane domain of MAVS to promote MAVS aggregation. ALDH1B1 was recruited to MAVS aggregates. In addition, ALDH1B1 also enhanced the interaction between activated RIG-I and MAVS, thus increasing IFN-β production and the antiviral response. Furthermore, Aldh1b1-/- mice developed more severe symptoms than did wild-type mice upon IAV infection. Together, these data identify an aldehyde dehydrogenase in mitochondria that functionally regulates MAVS-mediated signaling and the antiviral response.

Genome-wide and targeted CRISPR screens identify RNF213 as a mediator of interferon gamma-dependent pathogen restriction in human cells

To define cellular immunity to the intracellular pathogen Toxoplasma gondii, we performed a genome-wide CRISPR loss-of-function screen to identify genes important for (interferon gamma) IFN-γ-dependent growth restriction. We revealed a role for the tumor suppressor NF2/Merlin for maximum induction of Interferon Stimulated Genes (ISG), which are positively regulated by the transcription factor IRF-1. We then performed an ISG-targeted CRISPR screen that identified the host E3 ubiquitin ligase RNF213 as necessary for IFN-γ-mediated control of T. gondii in multiple human cell types. RNF213 was also important for control of bacterial (Mycobacterium tuberculosis) and viral (Vesicular Stomatitis Virus) pathogens in human cells. RNF213-mediated ubiquitination of the parasitophorous vacuole membrane (PVM) led to growth restriction of T. gondii in response to IFN-γ. Moreover, overexpression of RNF213 in naive cells also impaired growth of T. gondii. Surprisingly, growth inhibition did not require the autophagy protein ATG5, indicating that RNF213 initiates restriction independent of a previously described noncanonical autophagy pathway. Mutational analysis revealed that the ATPase domain of RNF213 was required for its recruitment to the PVM, while loss of a critical histidine in the RZ finger domain resulted in partial reduction of recruitment to the PVM and complete loss of ubiquitination. Both RNF213 mutants lost the ability to restrict growth of T. gondii, indicating that both recruitment and ubiquitination are required. Collectively, our findings establish RNF213 as a critical component of cell-autonomous immunity that is both necessary and sufficient for control of intracellular pathogens in human cells.

Structural basis of Irgb6 inactivation by Toxoplasma gondii through the phosphorylation of switch I

Irgb6 is a priming immune-related GTPase (IRG) that counteracts Toxoplasma gondii. It is known to be recruited to the low virulent type II T. gondii parasitophorous vacuole (PV), initiating cell-autonomous immunity. However, the molecular mechanism by which immunity-related GTPases become inactivated after the parasite infection remains obscure. Here, we found that Thr95 of Irgb6 is prominently phosphorylated in response to low virulent type II T. gondii infection. We observed that a phosphomimetic T95D mutation in Irgb6 impaired its localization to the PV and exhibited reduced GTPase activity in vitro. Structural analysis unveiled an atypical conformation of nucleotide-free Irgb6-T95D, resulting from a conformational change in the G-domain that allosterically modified the PV membrane-binding interface. In silico docking corroborated the disruption of the physiological membrane binding site. These findings provide novel insights into a T. gondii-induced allosteric inactivation mechanism of Irgb6.

A Combination of Four Nuclear Targeted Effectors Protects Toxoplasma Against Interferon Gamma Driven Human Host Cell Death During Acute Infection

In both mice and humans, Type II interferon-gamma (IFNγ) is crucial for regulation of Toxoplasma gondii (T. gondii) infection, during acute or chronic phases. To thwart this defense, T. gondii secretes protein effectors hindering the hosťs immune response. For example, T. gondii relies on the MYR translocon complex to deploy soluble dense granule effectors (GRAs) into the host cell cytosol or nucleus. Recent genome-wide loss-of-function screens in IFNγ-primed primary human fibroblasts identified MYR translocon components as crucial for parasite resistance against IFNγ driven vacuole clearance. However, these screens did not pinpoint specific MYR-dependent GRA proteins responsible for IFNγ signaling blockade, suggesting potential functional redundancy. Our study reveals that T. gondii depends on the MYR translocon complex to prevent host cell death and parasite premature egress in human cells stimulated with IFNγ postinfection, a unique phenotype observed in various human cell lines but not in murine cells. Intriguingly, inhibiting parasite egress did not prevent host cell death, indicating this mechanism is distinct from those described previously. Genome-wide loss-of-function screens uncovered TgIST, GRA16, GRA24, and GRA28 as effectors necessary for a complete block of IFNγ response. GRA24 and GRA28 directly influenced IFNγ driven transcription, GRA24's action depended on its interaction with p38 MAPK, while GRA28 disrupted histone acetyltransferase activity of CBP/p300. Given the intricate nature of the immune response to T. gondii, it appears that the parasite has evolved equally elaborate mechanisms to subvert IFNγ signaling, extending beyond direct interference with the JAK/STAT1 pathway, to encompass other signaling pathways as well.

Alterations in RNA editing in skeletal muscle following exercise training in individuals with Parkinson's disease

Parkinson's Disease (PD) is the second most common neurodegenerative disease behind Alzheimer's Disease, currently affecting more than 10 million people worldwide and 1.5 times more males than females. The progression of PD results in the loss of function due to neurodegeneration and neuroinflammation. The etiology of PD is multifactorial, including both genetic and environmental origins. Here we explored changes in RNA editing, specifically editing through the actions of the Adenosine Deaminases Acting on RNA (ADARs), in the progression of PD. Analysis of ADAR editing of skeletal muscle transcriptomes from PD patients and controls, including those that engaged in a rehabilitative exercise training program revealed significant differences in ADAR editing patterns based on age, disease status, and following rehabilitative exercise. Further, deleterious editing events in protein coding regions were identified in multiple genes with known associations to PD pathogenesis. Our findings of differential ADAR editing complement findings of changes in transcriptional networks identified by a recent study and offer insights into dynamic ADAR editing changes associated with PD pathogenesis.

The crucial regulatory role of type I interferon in inflammatory diseases

Type I interferon (IFN-I) plays crucial roles in the regulation of inflammation and it is associated with various inflammatory diseases including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and periodontitis, impacting people's health and quality of life. It is well-established that IFN-Is affect immune responses and inflammatory factors by regulating some signaling. However, currently, there is no comprehensive overview of the crucial regulatory role of IFN-I in distinctive pathways as well as associated inflammatory diseases. This review aims to provide a narrative of the involvement of IFN-I in different signaling pathways, mainly mediating the related key factors with specific targets in the pathways and signaling cascades to influence the progression of inflammatory diseases. As such, we suggested that IFN-Is induce inflammatory regulation through the stimulation of certain factors in signaling pathways, which displays possible efficient treatment methods and provides a reference for the precise control of inflammatory diseases.

IFN-γ-mediated control of SARS-CoV-2 infection through nitric oxide

Introduction

The COVID-19 pandemic has highlighted the need to identify mechanisms of antiviral host defense against SARS-CoV-2. One such mediator is interferon-g (IFN-γ), which, when administered to infected patients, is reported to result in viral clearance and resolution of pulmonary symptoms. IFN-γ treatment of a human lung epithelial cell line triggered an antiviral activity against SARS-CoV-2, yet the mechanism for this antiviral response was not identified.

Methods

Given that IFN-γ has been shown to trigger antiviral activity via the generation of nitric oxide (NO), we investigated whether IFN-γ induction of antiviral activity against SARS-CoV-2 infection is dependent upon the generation of NO in human pulmonary epithelial cells. We treated the simian epithelial cell line Vero E6 and human pulmonary epithelial cell lines, including A549-ACE2, and Calu-3, with IFN-γ and observed the resulting induction of NO and its effects on SARS-CoV-2 replication. Pharmacological inhibition of inducible nitric oxide synthase (iNOS) was employed to assess the dependency on NO production. Additionally, the study examined the effect of interleukin-1b (IL-1β) on the IFN-g-induced NO production and its antiviral efficacy.

Results

Treatment of Vero E6 cells with IFN-γ resulted in a dose-responsive induction of NO and an inhibitory effect on SARS-CoV-2 replication. This antiviral activity was blocked by pharmacologic inhibition of iNOS. IFN-γ also triggered a NO-mediated antiviral activity in SARS-CoV-2 infected human lung epithelial cell lines A549-ACE2 and Calu-3. IL-1β enhanced IFN-γ induction of NO, but it had little effect on antiviral activity.

Discussion

Given that IFN-g has been shown to be produced by CD8+ T cells in the early response to SARS-CoV-2, our findings in human lung epithelial cell lines, of an IFN-γ-triggered, NO-dependent, links the adaptive immune response to an innate antiviral pathway in host defense against SARS-CoV-2. These results underscore the importance of IFN-γ and NO in the antiviral response and provide insights into potential therapeutic strategies for COVID-19.

SARS-CoV-2 decreases malaria severity in co-infected rodent models

Coronavirus disease 2019 (COVID-19) and malaria, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Plasmodium parasites, respectively, share geographical distribution in regions where the latter disease is endemic, leading to the emergence of co-infections between the two pathogens. Thus far, epidemiologic studies and case reports have yielded insufficient data on the reciprocal impact of the two pathogens on either infection and related diseases. We established novel co-infection models to address this issue experimentally, employing either human angiotensin-converting enzyme 2 (hACE2)-expressing or wild-type mice, in combination with human- or mouse-infective variants of SARS-CoV-2, and the P. berghei rodent malaria parasite. We now show that a primary infection by a viral variant that causes a severe disease phenotype partially impairs a subsequent liver infection by the malaria parasite. Additionally, exposure to an attenuated viral variant modulates subsequent immune responses and provides protection from severe malaria-associated outcomes when a blood stage P. berghei infection was established. Our findings unveil a hitherto unknown host-mediated virus-parasite interaction that could have relevant implications for disease management and control in malaria-endemic regions. This work may contribute to the development of other models of concomitant infection between Plasmodium and respiratory viruses, expediting further research on co-infections that lead to complex disease presentations.

Bioinformatics analysis of ceRNA network of autophagy-related genes in pediatric asthma

The molecular underpinnings of pediatric asthma present avenues for targeted therapies. A deeper exploration into the significance of differentially expressed autophagy-related genes (DE-ARGs) and their interactions with the long noncoding RNA (lncRNA)-microRNA (miRNA)-mRNA network may offer insights into the pathogenesis of pediatric asthma. DE-ARGs were retrieved from the Gene Expression Omnibus and the Human Autophagy Database. These DE-ARGs were subjected to comprehensive analyses, including Gene Ontology, Kyoto Encyclopedia of Genes and Genomes pathway, Gene Set Enrichment Analysis, and protein-protein interaction networks. The identified DE-ARGs were further verified for core gene expression. The miRDB and ENCORI databases were used for inverse miRNA predictions. Furthermore, miRNA-lncRNA interactions were predicted using LncBase and ENCORI platforms. Following the exclusion of lncRNAs exclusively localized in the nucleus and extracellular space, a competitive endogenous RNA (ceRNA) network was established and subsequently subjected to detailed analysis. The mRNA expression patterns in the ceRNA network were validated using quantitative real-time PCR. In total, 31 DE-ARGs were obtained, of which 29 were up-regulated and 2 were down-regulated. Notably, the autophagy, regulation of apoptotic signaling pathways, interferon-α/β signaling, interferon γ signaling, autophagy-animal, and apoptosis pathways were predominantly enriched in pediatric asthma. Five hub genes (VEGFA, CFLAR, RELA, FAS, and ATF6) were further analyzed using the Gene Expression Omnibus dataset to verify their expression patterns and diagnostic efficacy. Four hub genes (VEGFA, CFLAR, RELA, and FAS) were obtained. Finally, a ceRNA network of 4 mRNAs (VEGFA, CFLAR, RELA, and FAS), 3 miRNAs (hsa-miR-320b, hsa-miR-22-3p, and hsa-miR-625-5p), and 35 lncRNAs was constructed by integrating data from literature review and analyzing the predicted miRNAs and lncRNAs. Moreover, the quantitative real-time PCR data revealed a pronounced upregulation of Fas cell surface death receptor. The identification of 4 DE-ARGs, especially Fas cell surface death receptor, has shed light on their potential pivotal role in the pathogenesis of pediatric asthma. The established ceRNA network provides novel insights into the autophagy mechanism in asthma and suggests promising avenues for the development of potential therapeutic strategies.

Analysis of intestinal epithelial cell responses to Cryptosporidium highlights the temporal effects of IFN-γ on parasite restriction

The production of IFN-γ is crucial for control of multiple enteric infections, but its impact on intestinal epithelial cells (IEC) is not well understood. Cryptosporidium parasites exclusively infect epithelial cells and the ability of interferons to activate the transcription factor STAT1 in IEC is required for parasite clearance. The use of single cell RNA sequencing to profile IEC during infection revealed induction of IFN-γ-dependent gene signatures that was comparable between uninfected and infected cells, and IEC expression of the IFN-γ receptor was required for parasite control. Unexpectedly, treatment of Ifng-/- mice with IFN-γ demonstrated the IEC response to this cytokine correlates with a delayed reduction in parasite burden but did not affect parasite development. These data sets provide insight into the impact of IFN-γ on IEC and suggest a model in which IFN-γ-mediated bystander activation of uninfected enterocytes is important for control of Cryptosporidium.

Changes in ADAR RNA editing patterns in CMV and ZIKV congenital infections

BACKGROUND

RNA editing is a process that increases transcriptome diversity, often through Adenosine Deaminases Acting on RNA (ADARs) that catalyze the deamination of adenosine to inosine. ADAR editing plays an important role in regulating brain function and immune activation, and is dynamically regulated during brain development. Additionally, the ADAR1 p150 isoform is induced by interferons in viral infection and plays a role in antiviral immune response. However, the question of how virus-induced ADAR expression affects host transcriptome editing remains largely unanswered. This question is particularly relevant in the context of congenital infections, given the dynamic regulation of ADAR editing during brain development, the importance of this editing for brain function, and subsequent neurological symptoms of such infections, including microcephaly, sensory issues, and other neurodevelopmental abnormalities. Here, we begin to address this question, examining ADAR expression in publicly available datasets of congenital infections of human cytomegalovirus (HCMV) microarray expression data, as well as mouse cytomegalovirus (MCMV) and mouse/ human induced pluripotent neuroprogenitor stem cell (hiNPC) Zika virus (ZIKV) RNA-seq data.

RESULTS

We found that in all three datasets, ADAR1 was overexpressed in infected samples compared to uninfected samples. In the RNA-seq datasets, editing rates were also analyzed. In all mouse infections cases, the number of editing sites was significantly increased in infected samples, albeit this was not the case for hiNPC ZIKV samples. Mouse ZIKV samples showed altered editing of well-established protein-recoding sites such as Gria3, Grik5, and Nova1, as well as editing sites that may impact miRNA binding.

CONCLUSIONS

Our findings provide evidence for changes in ADAR expression and subsequent dysregulation of ADAR editing of host transcriptomes in congenital infections. These changes in editing patterns of key neural genes have potential significance in the development of neurological symptoms, thus contributing to neurodevelopmental abnormalities. Further experiments should be performed to explore the full range of editing changes that occur in different congenital infections, and to confirm the specific functional consequences of these editing changes.

A Toxoplasma gondii lipoxygenase-like enzyme is necessary for virulence and changes localization associated with the host immune response

IMPORTANCE

Lipoxygenases (LOXs) are enzymes that catalyze the deoxygenation of polyunsaturated fatty acids such as linoleic and arachidonic acid. These modifications create signaling molecules that are best characterized for modulating the immune response. Deletion of the first lipoxygenase-like enzyme characterized for Toxoplasma gondii (TgLOXL1) generated a less virulent strain, and infected mice showed a decreased immune response. This virulence defect was dependent on the mouse cytokine interferon gamma IFNγ. TgLOXL1 changes location from inside the parasite in tissue culture conditions to vesicular structures within the host immune cells during mouse infection. These results suggest that TgLOXL1 plays a role in the modification of the host immune response in mice.

Protective immunity induced by DNA vaccine containing TgGRA35, TgGRA42, and TgGRA43 against Toxoplasma gondii infection in Kunming mice

Background

Toxoplasma gondii can cause congenital infection and abortion in humans and warm-blooded animals. T. gondii dense granule proteins, GRA35, GRA42, and GRA43, play a critical role in the establishment of chronic infection. However, their potential to induce protective immunity against T. gondii infection remains unexplored.

Objective

This study aimed to test the efficacy of a DNA vaccine encompassing GRA35, GRA42, and GRA43 in inducing protective immunity against the highly virulent T. gondii RH strain (type I) and the brain cyst-forming PRU strain (type II).

Methods

The eukaryotic plasmids pVAX-GRA35, pVAX-GRA42, and pVAX-GRA43 were constructed and formulated into two- or three-gene cocktail DNA vaccines. The indirect immunofluorescence assay (IFA) was used to analyze their expression and immunogenicity. Mice were immunized with a single-gene, two-genes, or multicomponent eukaryotic plasmid, intramuscularly. We assessed antibody levels, cytotoxic T-cell (CTL) responses, cytokines, and lymphocyte surface markers by using flow cytometry. Additionally, mouse survival and cyst numbers in the brain of mice challenged 1 to 2 months postvaccination were determined.

Results

Specific humoral and cellular immune responses were elicited in mice immunized with single-, two-, or three-gene cocktail DNA vaccine, as indicated by significant increases in serum antibody concentrations of total IgG, IgG2a/IgG1 ratio, cytokine levels (IFN-γ, IL-2, IL-12, IL-4, and IL-10), lymphocyte proliferation, lymphocyte populations (CD4+ and CD8+ T lymphocytes), CTL activities, and survival, as well as decreased brain cysts, in comparison with control mice. Moreover, compared with pVAX-GRA35 + pVAX-GRA42, pVAX-GRA42 + pVAX-GRA43, or pVAX-GRA35 + pVAX-GRA43, multicomponent DNA vaccine with three genes (pVAX-GRA35 + pVAX-GRA42 + pVAX-GRA43) induced the higher humoral and cellular immune responses, including serum antibody concentrations, cytokine levels, lymphocyte proliferation, lymphocyte populations, CTL activities and survival, resulting in prolonged survival time and reduced brain cyst loads. Furthermore, mice immunized with pVAX-GRA35 + pVAX-GRA42, pVAX-GRA42 + pVAX-GRA43, or pVAX-GRA35 + pVAX-GRA43 showed greater Th1 immune responses and protective efficacy than the single-gene-vaccinated groups.

Conclusion

These results demonstrate that TgGRA35, TgGRA42, or TgGRA43 are vaccine candidates against T. gondii infection, and the three-gene DNA vaccine cocktail conferred the strongest protection against T. gondii infection.

Vγ9+Vδ2+ T cell control of Listeria monocytogenes growth in infected epithelial cells requires butyrophilin 3A genes

Intracellular bacteria produce antigens, which serve as potent activators of γδ T cells. Phosphoantigens are presented via a complex of butyrophilins (BTN) to signal infection to human Vγ9+Vδ2+ T cells. Here, we established an in vitro system allowing for studies of Vγ9+Vδ2+ T cell activity in coculture with epithelial cells infected with the intracellular bacterial pathogen Listeria monocytogenes. We report that the Vγ9+Vδ2+ T cells efficiently control L. monocytogenes growth in such cultures. This effector function requires the expression of members of the BTN3A family on epithelial cells. Specifically, we observed a BTN3A1-independent BTN3A3 activity to present antigen to Vγ9+Vδ2+ T cells. Since BTN3A1 is the only BTN3A associated with phosphoantigen presentation, our study suggests that BTN3A3 may present different classes of antigens to mediate Vγ9+Vδ2+ T cell effector function against L. monocytogenes-infected epithelia.

Dexamethasone impairs the expression of antimicrobial mediators in lipopolysaccharide-activated primary macrophages by inhibiting both expression and function of interferon β

Glucocorticoids potently inhibit expression of many inflammatory mediators, and have been widely used to treat both acute and chronic inflammatory diseases for more than seventy years. However, they can have several unwanted effects, amongst which immunosuppression is one of the most common. Here we used microarrays and proteomic approaches to characterise the effect of dexamethasone (a synthetic glucocorticoid) on the responses of primary mouse macrophages to a potent pro-inflammatory agonist, lipopolysaccharide (LPS). Gene ontology analysis revealed that dexamethasone strongly impaired the lipopolysaccharide-induced antimicrobial response, which is thought to be driven by an autocrine feedback loop involving the type I interferon IFNβ. Indeed, dexamethasone strongly and dose-dependently inhibited the expression of IFNβ by LPS-activated macrophages. Unbiased proteomic data also revealed an inhibitory effect of dexamethasone on the IFNβ-dependent program of gene expression, with strong down-regulation of several interferon-induced antimicrobial factors. Surprisingly, dexamethasone also inhibited the expression of several antimicrobial genes in response to direct stimulation of macrophages with IFNβ. We tested a number of hypotheses based on previous publications, but found that no single mechanism could account for more than a small fraction of the broad suppressive impact of dexamethasone on macrophage type I interferon signaling, underlining the complexity of this pathway. Preliminary experiments indicated that dexamethasone exerted similar inhibitory effects on primary human monocyte-derived or alveolar macrophages.

PIM1 controls GBP1 activity to limit self-damage and to guard against pathogen infection

Disruption of cellular activities by pathogen virulence factors can trigger innate immune responses. Interferon-γ (IFN-γ)-inducible antimicrobial factors, such as the guanylate binding proteins (GBPs), promote cell-intrinsic defense by attacking intracellular pathogens and by inducing programmed cell death. Working in human macrophages, we discovered that GBP1 expression in the absence of IFN-γ killed the cells and induced Golgi fragmentation. IFN-γ exposure improved macrophage survival through the activity of the kinase PIM1. PIM1 phosphorylated GBP1, leading to its sequestration by 14-3-3σ, which thereby prevented GBP1 membrane association. During Toxoplasma gondii infection, the virulence protein TgIST interfered with IFN-γ signaling and depleted PIM1, thereby increasing GBP1 activity. Although infected cells can restrain pathogens in a GBP1-dependent manner, this mechanism can protect uninfected bystander cells. Thus, PIM1 can provide a bait for pathogen virulence factors, guarding the integrity of IFN-γ signaling.

Investigation of the impact of AXL, TLR3, and STAT2 in congenital Zika syndrome through genetic polymorphisms and protein-protein interaction network analyses

INTRODUCTION

Zika virus (ZIKV) is a human teratogen that causes congenital Zika syndrome (CZS). AXL, TLR3, and STAT2 are proteins involved in the ZIKV's entry into cells (AXL) and host's immune response (TLR3 and STAT2). In this study, we evaluated the role of genetic polymorphisms in these three genes as risk factors to CZS, and highlighted which proteins that interact with them could be important for ZIKV infection and teratogenesis.

MATERIALS AND METHODS

We evaluate eighty-eight children exposed to ZIKV during the pregnancy, 40 with CZS and 48 without congenital anomalies. The evaluated polymorphisms in AXL (rs1051008), TLR3 (rs3775291), and STAT2 (rs2066811) were genotyped using TaqMan® Genotyping Assays. A protein-protein interaction network was created in STRING database and analyzed in Cytoscape software.

RESULTS

We did not find any statistical significant association among the polymorphisms and the occurrence of CZS. Through the analyses of the network composed by AXL, TLR3, STAT2 and their interactions targets, we found that EGFR and SRC could be important proteins for the ZIKV infection and its teratogenesis.

CONCLUSION

In summary, our results demonstrated that the evaluated polymorphisms do not seem to represent risk factors for CZS; however, EGFR and SRC appear to be important proteins that should be investigated in future studies.

MAVI1, an endoplasmic reticulum-localized microprotein, suppresses antiviral innate immune response by targeting MAVS on mitochondrion

Pattern recognition receptor-mediated innate immunity is critical for host defense against viruses. A growing number of coding and noncoding genes are found to encode microproteins. However, the landscape and functions of microproteins in responsive to virus infection remain uncharacterized. Here, we systematically identified microproteins that are responsive to vesicular stomatitis virus infection. A conserved and endoplasmic reticulum-localized membrane microprotein, MAVI1 (microprotein in antiviral immunity 1), was found to interact with mitochondrion-localized MAVS protein and inhibit MAVS aggregation and type I interferon signaling activation. The importance of MAVI1 was highlighted that viral infection was attenuated and survival rate was increased in Mavi1-knockout mice. A peptide inhibitor targeting the interaction between MAVI1 and MAVS activated the type I interferon signaling to defend viral infection. Our findings uncovered that microproteins play critical roles in regulating antiviral innate immune responses, and targeting microproteins might represent a therapeutic avenue for treating viral infection.

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.

IFN-γ: A Crucial Player in the Fight Against HBV Infection?

About 0.8 million people die because of hepatitis B virus (HBV) infection each year. In around 5% of infected adults, the immune system is ineffective in countering HBV infection, leading to chronic hepatitis B (CHB). CHB is associated with hepatocellular carcinoma, which can lead to patient death. Unfortunately, although current treatments against CHB allow control of HBV infection, they are unable to achieve complete eradication of the virus. Cytokines of the IFN family represent part of the innate immune system and are key players in virus elimination. IFN secretion induces the expression of interferon stimulated genes, producing proteins that have antiviral properties and that are essential to cell-autonomous immunity. IFN-α is commonly used as a therapeutic approach for CHB. In addition, IFN-γ has been identified as the main IFN family member responsible for HBV eradication during acute infection. In this review, we summarize the key evidence gained from cellular or animal models of HBV replication or infection concerning the potential anti-HBV roles of IFN-γ with a particular focus on some IFN-γ-inducible genes.

TRIM32 reduced the recruitment of innate immune cells and the killing capacity of Listeria monocytogenes by inhibiting secretion of chemokines

Listeria monocytogenes (Lm) is a facultative, intracellular Gram-positive pathogenic bacterium that causes sepsis, a condition characterized by persistent excessive inflammation and organ dysfunction. However, the pathogenesis of Lm-induced sepsis is unknown. In this research, we discovered that TRIM32 is required for innate immune regulation during Lm infection. Trim32 deficiency remarkably reduced bacteremia and proinflammatory cytokine secretion in mice with severe Lm infection, preventing sepsis. Trim32^-/- mice had a lower bacterial burden after Lm infection and survived significantly longer than wild-type (WT) mice, as well as lower serum levels of inflammatory cytokines TNF-α, IL-6, IL-18, IL-12p70, IFN-β, and IFN-γ at 1 day post infection (dpi) compared to WT mice. On the other hand, the chemokines CXCL1, CCL2, CCL7, and CCL5 were enhanced at 3 dpi in Trim32^-/- mice than WT mice, reflecting increased recruitment of neutrophils and macrophages. Furthermore, Trim32^-/- mice had higher levels of macrophage-associated iNOS to kill Lm. Collectively, our findings suggest that TRIM32 reduces innate immune cells recruitment and Lm killing capabilities via iNOS production.

PLSCR1 is a cell-autonomous defence factor against SARS-CoV-2 infection

Understanding protective immunity to COVID-19 facilitates preparedness for future pandemics and combats new SARS-CoV-2 variants emerging in the human population. Neutralizing antibodies have been widely studied; however, on the basis of large-scale exome sequencing of protected versus severely ill patients with COVID-19, local cell-autonomous defence is also crucial1-4. Here we identify phospholipid scramblase 1 (PLSCR1) as a potent cell-autonomous restriction factor against live SARS-CoV-2 infection in parallel genome-wide CRISPR-Cas9 screens of human lung epithelia and hepatocytes before and after stimulation with interferon-γ (IFNγ). IFNγ-induced PLSCR1 not only restricted SARS-CoV-2 USA-WA1/2020, but was also effective against the Delta B.1.617.2 and Omicron BA.1 lineages. Its robust activity extended to other highly pathogenic coronaviruses, was functionally conserved in bats and mice, and interfered with the uptake of SARS-CoV-2 in both the endocytic and the TMPRSS2-dependent fusion routes. Whole-cell 4Pi single-molecule switching nanoscopy together with bipartite nano-reporter assays found that PLSCR1 directly targeted SARS-CoV-2-containing vesicles to prevent spike-mediated fusion and viral escape. A PLSCR1 C-terminal β-barrel domain-but not lipid scramblase activity-was essential for this fusogenic blockade. Our mechanistic studies, together with reports that COVID-associated PLSCR1 mutations are found in some susceptible people3,4, identify an anti-coronavirus protein that interferes at a late entry step before viral RNA is released into the host-cell cytosol.

A heterotrimeric complex of Toxoplasma proteins promotes parasite survival in interferon gamma-stimulated human cells

Toxoplasma gondii secretes protein effectors to subvert the human immune system sufficiently to establish a chronic infection. Relative to murine infections, little is known about which parasite effectors disarm human immune responses. Here, we used targeted CRISPR screening to identify secreted protein effectors required for parasite survival in IFNγ-activated human cells. Independent screens were carried out using 2 Toxoplasma strains that differ in virulence in mice, leading to the identification of effectors required for survival in IFNγ-activated human cells. We identify the secreted protein GRA57 and 2 other proteins, GRA70 and GRA71, that together form a complex which enhances the ability of parasites to persist in IFNγ-activated human foreskin fibroblasts (HFFs). Components of the protein machinery required for export of Toxoplasma proteins into the host cell were also found to be important for parasite resistance to IFNγ in human cells, but these export components function independently of the identified protein complex. Host-mediated ubiquitination of the parasite vacuole has previously been associated with increased parasite clearance from human cells, but we find that vacuoles from GRA57, GRA70, and GRA71 knockout strains are surprisingly less ubiquitinated by the host cell. We hypothesise that this is likely a secondary consequence of deletion of the complex, unlinked to the IFNγ resistance mediated by these effectors.