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Mammalian innate immune response to virus infection is meditated by many cell-intrinsic pathways. RNA viruses, such as Sendai virus, which replicate in the cytoplasm, trigger the RIG-I-like receptor pathway, which activates the transcription factor, IRF3. Activated IRF3 translocates to the nucleus and induces transcription of the genes which encode interferons, the major antiviral cytokines. Interestingly, IRF3 activates another interferon-independent antiviral pathway, called RIG-I induced pathway of apoptosis (RIPA). For activating RIPA, IRF3 translocates from the cytoplasm to mitochondria. RIPA requires linear polyubiquitination of IRF3 by the enzyme complex, LUBAC; ubiquitinated IRF3 binds to Bax and translocates it to mitochondria causing the release of Cytochrome C, activation of caspases and apoptosis of the infected cell. Here, we report that Otulin, the deubiquitinase that removes linear polyubiquitin chains, inhibits RIPA by deubiquitinating IRF3. Ablation of Otulin expression enhanced RIPA and its overexpression inhibited RIPA. In virus-infected cells, to overcome Otulin-mediated inhibition, RIPA actively degrades Otulin. This degradation required sequential actions of RIPA-activated Caspase 3 and proteasomes. Caspase 3 cleaved Otulin at D31; the D31A mutant was not cleaved at all. The caspase-cleaved fragment was totally degraded by proteasomes, which was preceded by its K48-linked ubiquitination. Mass spectrometric analysis of Otulin identified K64 and K197 as the ubiquitinated residues. Otulin interacted with LUBAC after virus infection and the E3-ubiquitin ligase, HOIP, a component of LUBAC, ubiquitinated Otulin to trigger its proteasome-mediated degradation. To assess the impact of Otulin degradation on RIPA-mediated antiviral action, we expressed, in Otulin-ablated cells, a non-degradable mutant of Otulin, in which D31, K64 and K197 had been mutated. The cells expressing the Otulin mutant were less susceptible to virus-induced apoptosis, because RIPA was less active, and consequently virus replication was more robust. Thus, our study has revealed an important positive feedback loop of RIPA.

The Sendai virus vector has received a lot of attention due to its broad tropism for mammalian cells. As a result of efforts for genetic studies based on a mutant virus, we can now express more than 10 genes of up to 13.5 kilo nucleotides in a single vector with high protein expression efficiency. To prove this benefit, we examined the efficacy of the novel ribonucleic acid (RNA) virus vector harboring the human iduronate-2-sulfatase (IDS) gene with 1,653 base pairs, a causative gene for mucopolysaccharidosis type II, also known as a disorder of lysosomal storage disorders. As expected, this novel RNA vector with the human IDS gene exhibited its marked expression as determined by the expression of enhanced green fluorescent protein and IDS enzyme activity. While these cells exhibited a normal growth rate, the BHK-21 transformant cells stably expressing the human IDS gene persistently generated an active human IDS enzyme extracellularly. The human IDS protein produced failed to be incorporated into the lysosome when cells were pretreated with mannose-6-phosphate, demonstrating that this human IDS enzyme has potential for therapeutic use by cross-correction. These results suggest that our novel RNA vector may be applicable for further clinical settings.

Retinoic acid-inducible gene I (RIG-I) plays a critical role in the recognition of intracytoplasmic viral RNA. Upon binding to the RNA of invading viruses, the activated RIG-I translocates to mitochondria, where it recruits adapter protein MAVS, causing a series of signaling cascades. In this study, we demonstrated that Hsp70 binding protein 1 (HSPBP1) promotes RIG-I-mediated signal transduction. The overexpression of HSPBP1 can increase the stability of RIG-I protein by inhibiting its K48-linked ubiquitination, and promote the activation of IRF3 and the production of IFN-β induced by Sendai virus. Knockdown and knockout of HSPBP1 leads to down-regulation of virus-induced RIG-I expression, inhibits IRF3 activation, and reduces the production of IFNB1. These results indicate that HSPBP1 positively regulates the antiviral signal pathway induced by inhibiting the K48-linked ubiquitination of RIG-I.

The establishment of human-induced pluripotent stem cell (iPSC) models from sporadic Alzheimer’s disease (sAD) patients is necessary and could potentially benefit research into disease etiology and therapeutic strategies. However, the development of sAD iPSC models is still limited due to the multifactorial nature of the disease. Here, we extracted peripheral blood mononuclear cells (PBMCs) from a patient with sAD and induced them into iPSC by introducing the Sendai virus expressing Oct3/4, Sox2, c-Myc, and Klf4, which were subsequently induced into neural cells to build the cell model of AD. Using alkaline phosphatase staining, immunofluorescence staining, karyotype analysis, reverse transcription-polymerase chain reaction (RT-PCR), and teratoma formation in vitro, we demonstrated that the iPSC derived from PMBCs (PBMC-iPSC) had a normal karyotype and potential to differentiate into three embryonic layers. Immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) suggested that PBMC-iPSCs were successfully differentiated into neural cells. Detection of beta-amyloid protein oligomer (AβO), beta-amyloid protein 1-40 (Aβ 1-40), and beta-amyloid protein 1-42 (Aβ 1-42) indicated that the AD cell model was satisfactorily constructed in vitro. In conclusion, this study has successfully generated an AD cell model with pathological features of beta-amyloid peptide deposition using PBMC from a patient with sAD.

Immunotherapy utilizing induced pluripotent stem cell (iPSC) technology has great potential. Functionally rejuvenated cytotoxic T lymphocytes (CTLs) can survive long-term as young memory T cells in vivo, with continuous tumor eradication. Banking of iPSCs as an unlimited “off-the-shelf” source of therapeutic T cells may be feasible. To generate safer iPSCs, we reprogrammed human papilloma virus type 16 (HPV16) E6-specific CTLs by Sendai virus vector without cotransduction of SV40 large T antigen. The iPSCs efficiently differentiated into HPV16-specific rejuvenated CTLs that demonstrated robust cytotoxicity against cervical cancer. The tumor-suppressive effect of rejuvenated CTLs was stronger and more persistent than that of original peripheral blood CTLs. These rejuvenated HPV16-specific CTLs provide a sustained tumor-suppressive effect even for epithelial cancers and constitute promising immunotherapy for cervical cancer., Graphical Abstract, In this article, Honda and colleagues show that safer iPSCs can be established from an HPV-CTL clone by Sendai virus vector without cotransduction of SV40 large T antigen. The iPSCs efficiently differentiated rejuvenated CTLs and exhibited a sustained cervical cancer-suppressive effect in vitro and in vivo.

The novel coronavirus SARS‐CoV‐2 is the causative agent of the global coronavirus disease 2019 (COVID‐19) outbreak. In addition to pneumonia, other COVID‐19‐associated symptoms have been reported, including loss of smell (anosmia). However, the connection between infection with coronavirus and anosmia remains enigmatic. It has been reported that defects in olfactory cilia lead to anosmia. In this Viewpoint, we summarize transmission electron microscopic studies of cilia in virus‐infected cells. In the human nasal epithelium, coronavirus infects the ciliated cells and causes deciliation. Research has shown that viruses such as influenza and Sendai attach to the ciliary membrane. The Sendai virus enters cilia by fusing its viral membrane with the ciliary membrane. A recent study on SARS‐CoV‐2–human protein–protein interactions revealed that the viral nonstructural protein Nsp13 interacts with the centrosome components, providing a potential molecular link. The mucociliary escalator removes inhaled pathogenic particles and functions as the first line of protection mechanism against viral infection in the human airway. Thus, future investigation into the virus–cilium interface will help further the battle against COVID‐19., The connection between coronavirus infection and anosmia remains enigmatic. Defects in olfactory cilia lead to anosmia. This viewpoint summarizes transmission electron microscopic studies of cilia in virus‐infected cells: Coronavirus infects the ciliated cells in human nasal epithelium and causes deciliation. Influenza viruses attach to the ciliary membrane, and Sendai virus enters cilia by fusing its viral membrane with the ciliary membrane.

The interferon system is the first line of defense against virus infection. Recently, using a high-throughput genetic screen of a human interferon-stimulated gene short-hairpin RNA library, we identified a viral restriction factor, TDRD7 (Tudor domain–containing 7). TDRD7 inhibits the paramyxo-/pneumoviruses (e.g. Sendai virus and respiratory syncytial virus) by interfering with the virus-induced cellular autophagy pathway, which these viruses use for their replication. Here, we report that TDRD7 is a viral restriction factor against herpes simplex virus (HSV-1). Using knockdown, knockout, and ectopic expression systems, we demonstrate the anti–HSV-1 activity of TDRD7 in multiple human and mouse cell types. TDRD7 inhibited the virus-activated AMP-activated protein kinase (AMPK), which was essential for HSV-1 replication. Genetic ablation or chemical inhibition of AMPK activity suppressed HSV-1 replication in multiple human and mouse cells. Mechanistically, HSV-1 replication after viral entry depended on AMPK but not on its function in autophagy. The antiviral activity of TDRD7 depended on its ability to inhibit virus-activated AMPK. In summary, our results indicate that the newly identified viral restriction factor TDRD7 inhibits AMPK and thereby blocks HSV-1 replication independently of the autophagy pathway. These findings suggest that AMPK inhibition represents a potential strategy to manage HSV-1 infections.

Animal cells use pattern-recognition receptors (PRRs) to detect specific pathogens. Pathogen detection mounts an appropriate immune response, including interferon and cytokine induction. The intracellular PRR-signaling pathways that detect DNA viruses have been characterized, particularly in myeloid cells. In these pathways, cGMP-AMP synthase (cGAS) and the pyrin and HIN domain family member (PYHIN) protein interferon-γ-inducible protein 16 (IFI16) detect DNA and signal via stimulator of interferon genes protein (STING). However, although airway epithelial cells are frontline sentinels in detecting pathogens, information on how they respond to DNA viruses is limited, and the roles of PYHIN proteins in these cells are unknown. Here, we examined expression and activities of cGAS, STING, and PYHINs in human lung epithelial cells. A549 epithelial cells, commonly used for RNA-sensing studies, failed to respond to DNA because they lacked STING expression, and ectopic STING expression restored a cGAS-dependent DNA response in these cells. In contrast, NuLi-1 immortalized human bronchial epithelial cells did express STING, which was activated after DNA stimulation and mediated DNA-dependent gene induction. PYHIN1, which like IFI16 has been proposed to be a viral DNA sensor, was the only PYHIN protein expressed in both airway epithelial cell types. However, rather than having a role in DNA sensing, PYHIN1 induced proinflammatory cytokines in response to interleukin-1 (IL-1) or tumor necrosis factor α (TNFα) stimulation. Of note, PYHIN1, via its HIN domain, directly induced IL-6 and TNFα transcription, revealing that PYHIN proteins play a role in proinflammatory gene induction in airway epithelial cells.

MicroRNAs (miRNAs) are small noncoding RNAs that suppress the expression of multiple genes and are involved in numerous biologic functions and disorders, including human diseases. Here, we report that two miRNAs, miR-302b and miR-372, target mitochondrial-mediated antiviral innate immunity by regulating mitochondrial dynamics and metabolic demand. Using human cell lines transfected with the synthetic analog of viral dsRNA, poly(I-C), or challenged with Sendai virus, we found that both miRNAs are up-regulated in the cells late after viral infection and ultimately terminate the production of type I interferons and inflammatory cytokines. We found that miR-302b and miR-372 are involved in dynamin-related protein 1 (DRP1)-dependent mitochondrial fragmentation and disrupt mitochondrial metabolism by attenuating solute carrier family 25 member 12 (SLC25A12), a member of the SLC25 family. Neutralizing the effects of the two miRNAs through specific inhibitors re-established the mitochondrial dynamics and the antiviral responses. We found that SLC25A12 contributes to regulating the antiviral response by inducing mitochondrial-related metabolite changes in the organelle. Structure-function analysis indicated that SLC25A12, as part of a prohibitin complex, associates with the mitochondrial antiviral-signaling protein in mitochondria, providing structural insight into the regulation of the mitochondrial-mediated antiviral response. Our results contribute to the understanding of how miRNAs modulate the innate immune response by altering mitochondrial dynamics and metabolic demand. Manipulating the activities of miR-302b and miR-372 may be a potential therapeutic approach to target RNA viruses.

Janus kinase 1 (JAK1) is a member of JAK family of non-receptor protein tyrosine kinases that plays critical roles in transducing cytokine signals via JAK-signal transducer and activator of transcription (STAT) signaling pathway. The importance of JAK1 in innate immunity has been well-studied in mammals and fish, yet in avian remains largely unknown. Here, we cloned the full-length of the duck JAK1 (duJAK1) gene for the first time. DuJAK1 encoded a protein of 1152 amino acids and possessed high amino acid identity with goose and budgerigar JAK1s. The duJAK1 was expressed in all detected tissues, especially high in the thymus and bursa of Fabricius. Overexpression of duJAK1 significantly activated ISRE promoter activity and induced duck viperin, 2', 5'-OAS, MX, PKR and ZAP expression. Knockdown of duJAK1 by small interfering RNA significantly inhibited duck Tembusu virus (DTMUV)-, duck Enteritis virus (DEV)-, poly (I:C)-, poly (dA:dT)- or Sendai virus (SeV)-induced ISRE promoter activation. Furthermore, duJAK1 exhibited antiviral activity against DTMUV infection. These results will help us understand the function of JAK family proteins in duck antiviral immunity.

Although chronic bacterial infections and inflammation are associated with progressive lung disease in patients with cystic fibrosis (CF), much less is known regarding the contributions of respiratory viral infections to this process. Clinical studies suggest that antiviral host defenses may be compromised in individuals with CF, and CF airway epithelia exhibit impaired antiviral responses in vitro. Here, we used the CF pig model to test the hypothesis that the antiviral activity of respiratory secretions is reduced in CF. We developed an in vitro assay to measure the innate antiviral activity present in airway surface liquid (ASL) from CF and non-CF pigs. We found that tracheal and nasal ASL from newborn non-CF pigs exhibited dose-dependent inhibitory activity against several enveloped and encapsidated viruses, including Sendai virus, respiratory syncytial virus, influenza A, and adenovirus. Importantly, we found that the anti–Sendai virus activity of nasal ASL from newborn CF pigs was significantly diminished relative to non-CF littermate controls. This diminution of extracellular antiviral defenses appears to be driven, at least in part, by the differences in pH between CF and non-CF ASL. These data highlight the novel antiviral properties of native airway secretions and suggest the possibility that defects in extracellular antiviral defenses contribute to CF pathogenesis.

Recent advances in gene therapy technologies have enabled the treatment of congenital disorders and cancers and facilitated the development of innovative methods, including induced pluripotent stem cell (iPSC) production and genome editing. We recently developed a novel non-transmissible and non-integrating measles virus (MV) vector capable of transferring multiple genes simultaneously into a wide range of cells through the CD46 and CD150 receptors. The MV vector expresses four genes for iPSC generation and the GFP gene for a period of time sufficient to establish iPSCs from human fibroblasts as well as peripheral blood T cells. The transgenes were expressed differentially depending on their gene order in the vector. Human hematopoietic stem/progenitor cells were directly and efficiently reprogrammed to naive-like cells that could proliferate and differentiate into primed iPSCs by the same method used to establish primed iPSCs from other cell types. The novel MV vector has several advantages for establishing iPSCs and potential future applications in gene therapy.

Many viruses initiate infection by binding to sialoglycan receptors at the cell surface. Binding to such receptors comes at a cost, however, as the sheer abundance of sialoglycans e.g. in mucus, may immobilize virions to non-functional decoy receptors. As a solution, sialoglycan-binding as well as sialoglycan-cleavage activities are often present in these viruses, which for paramyxoviruses are combined in the hemagglutinin-neuraminidase (HN) protein. The dynamic interactions of sialoglycan-binding paramyxoviruses with their receptors are thought to be key determinants of species tropism, replication and pathogenesis. Here we used biolayer interferometry to perform kinetic analyses of receptor interactions of animal and human paramyxoviruses (Newcastle disease virus, Sendai virus, and human parainfluenza virus 3). We show that these viruses display strikingly different receptor interaction dynamics, which correlated with their receptor-binding and -cleavage activities and the presence of a second sialic acid binding site. Virion binding was followed by sialidase-driven release, during which virions cleaved sialoglycans until a virus-specific density was reached, which was largely independent of virion concentration. Sialidase-driven virion release was furthermore shown to be a cooperative process and to be affected by pH. We propose that paramyxoviruses display sialidase-driven virion motility on a receptor-coated surface, until a threshold receptor density is reached at which virions start to dissociate. Similar motility has previously been observed for influenza viruses and is likely to also apply to sialoglycan-interacting embecoviruses. Analysis of the balance between receptor-binding and -cleavage increases our understanding of host species tropism determinants and zoonotic potential of viruses.

Achondroplasia (ACH) is the most common genetic form of dwarfism and belong to dominant monogenetic disorder (MGD) caused by a gain-of-function point mutation in the transmembrane region of fibroblast growth factor receptor 3 (FGFR3). There are currently two mutation sites reported – Gly380Arg and Gly375Cys, the former occupies the vast majority of ACH patients. Homozygous ACH patients have a much more severe phenotype and rarely survive, so most of the ACH patients seen are heterozygous mutations. Like many other MGDs, there are no effective therapeutic methods for ACH even though the cause of the mutation has been found. With the rapid development of stem cell biology and gene-editing technology, the research of ACH is not only important, but also provides theoretical and experimental basis for the investigation of other MGDs. In this study, we generated non-integrated induced pluripotent stem cell (iPSC) lines from ACH patient skin and urine of Gly380Arg mutation. Via powerful gene-editing tool – CRISPR-Cas9, we successfully obtained 2 completely corrected knock-in cell lines. They not only expressed pluripotent markers, maintained normal chromosomal number and structure, but also no off-target indels were identified. This is not only the first time to obtain ACH iPSCs using the most readily available biopsy sample – urine, the first to obtain non-integrated ACH iPSCs, but also is the first to perform gene correction in ACH research. Our study may provide important theoretical and experimental basis for the next step of stem cell research and treatment of ACH in the future.

Human parainfluenza viruses (HPIVs) are a leading cause of acute respiratory infection hospitalization in children, yet little is known about how dose, strain, tissue tropism, and individual heterogeneity affects the processes driving growth and clearance kinetics. Longitudinal measurements are possible by using reporter Sendai viruses, the murine counterpart of HPIV 1, that express luciferase, where the insertion location yields a wild-type (rSeV-luc(M-F*)) or attenuated (rSeV-luc(P-M)) phenotype. Bioluminescence from individual animals suggests that there is a rapid increase in expression followed by a peak, biphasic clearance, and resolution. However, these kinetics vary between individuals and with dose, strain, and whether the infection was initiated in the upper and/or lower respiratory tract. To quantify the differences, we translated the bioluminescence measurements from the nasopharynx, trachea, and lung into viral loads and used a mathematical model together a nonlinear mixed effects approach to define the mechanisms distinguishing each scenario. The results confirmed a higher rate of virus production with the rSeV-luc(M-F*) virus compared to its attenuated counterpart, and suggested that low doses result in disproportionately fewer infected cells. The analyses indicated faster infectivity and infected cell clearance rates in the lung and that higher viral doses, and concomitantly higher infected cell numbers, resulted in more rapid clearance. This parameter was also highly variable amongst individuals, which was particularly evident during infection in the lung. These critical differences provide important insight into distinct HPIV dynamics, and show how bioluminescence data can be combined with quantitative analyses to dissect host-, virus-, and dose-dependent effects., Author summary Human parainfluenza viruses (HPIVs) cause acute respiratory infections and can lead to the hospitalization of children. HPIV infection severity may vary due to dose, strain, patient, and whether the infection initiates within the upper or lower respiratory tract. There is a need to determine how the rates of virus spread and clearance change in different infection scenarios in order to better understand varying clinical manifestations. The significance of our research is in identifying the dominant mechanisms driving strain-, dose-, and tissue-specific HPIV infection kinetics, and in pairing bioluminescence data with quantitative analyses to determine how the same virus can yield patient-specific outcomes. This work enhances our understanding of HPIV infection and broadens our knowledge viral dynamics in the upper and lower respiratory tracts.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an autosomal dominant inherited disease, with variable penetrance and expressivity. Currently, more than 14 different genetic loci have been reported for ARVC, the majority being desmosomal genes like Plakophilin-2 (PKP2). Here, we generated an iPSC cell line bearing a pathogenic heterozygous mutation in PKP2 (c.1799delA) from a patient affected by ARVC. Peripheral blood mononuclear cells were reprogrammed by Sendai virus vectors encoding KOS, KLF4, and c-MYC. Derived iPSCs expressed pluripotent markers, showed intact karyotype and demonstrated the ability to differentiate into three germ layers.

Quaking (QKI) is an RNA-binding protein (RBP) involved in multiple aspects of RNA metabolism and many biological processes. Despite a known immune function in regulating monocyte differentiation and inflammatory responses, the degree to which QKI regulates the host interferon (IFN) response remains poorly characterized. Here we show that QKI ablation enhances poly(I:C) and viral infection-induced IFNβ transcription. Characterization of IFN-related signalling cascades reveals that QKI knockout results in higher levels of IRF3 phosphorylation. Interestingly, complementation with QKI-5 isoform alone is sufficient to rescue this phenotype and reduce IRF3 phosphorylation. Further analysis shows that MAVS, but not RIG-I or MDA5, is robustly upregulated in the absence of QKI, suggesting that QKI downregulates MAVS and thus represses the host IFN response. As expected, MAVS depletion reduces IFNβ activation and knockout of MAVS in the QKI knockout cells completely abolishes IFNβ induction. Consistently, ectopic expression of RIG-I activates stronger IFNβ induction via MAVS-IRF3 pathway in the absence of QKI. Collectively, these findings demonstrate a novel role for QKI in negatively regulating host IFN response by reducing MAVS levels.

Respirovirus C protein blocks the type I interferon (IFN)-stimulated activation of the JAK-STAT pathway. It has been reported that C protein inhibits IFN-α-stimulated tyrosine phosphorylation of STATs, but the underlying mechanism is poorly understood. Here, we show that the C protein of Sendai virus (SeV), a member of the Respirovirus genus, binds to the IFN receptor subunit IFN-α/β receptor subunit (IFNAR)2 and inhibits IFN-α-stimulated tyrosine phosphorylation of the upstream receptor-associated kinases, JAK1 and TYK2. Analysis of various SeV C mutant (Cm) proteins demonstrates the importance of the inhibitory effect on receptor-associated kinase phosphorylation for blockade of JAK-STAT signaling. Furthermore, this inhibitory effect and the IFNAR2 binding capacity are observed for all the respirovirus C proteins examined. Our results suggest that respirovirus C protein inhibits activation of the receptor-associated kinases JAK1 and TYK2 possibly through interaction with IFNAR2.

Interferon (IFN), the first ever-described cytokine, has a potent activity against viruses. Soon since its discovery, quantification of IFN has been an important issue. Most of the traditional methods to measure IFN biological activity rely on indirect methods that quantify dyes retained by IFN-protected cells against a lytic virus, or by techniques that indirectly quantify viral replication by measuring the expression level of viral-encoded reporter proteins such as the green fluorescent protein (GFP). In both cases, the IFN units are determined by the quantification of an effective dose 50, defined as the IFN dose that prevents 50% cell death of 50% reduction of the maximal amount of GFP intensity. In this study we propose the use of an alternative approach to measure IFN activity by calculating the minimal IFN dose 50 as the amount of IFN able to completely protect 50% of the cells from infection measured by the total absence of virus-dependent GFP signal in a cell culture plate. This sensitive approach could be used to easily quantify the Z value to determine IFN bioassay robustness. We believe that this approximation could be interesting to be considered by the IFN community.

Highlights • PDCoV nsp15 antagonizes IFN-β production. • PDCoV nsp15 suppresses NF-κB activation other than IRF3 activation. • The endoribonuclease activity is not essential for PDCoV nsp15 to antagonize IFN-β., Porcine deltacoronavirus (PDCoV) is an emerging swine coronavirus causing diarrhea and intestinal damage in nursing piglets. Previous work showed that PDCoV infection inhibits type I interferon (IFN) production. To further identify and characterize the PDCoV-encoded IFN antagonists will broaden our understanding of its pathogenesis. Nonstructural protein 15 (nsp15) encodes an endoribonuclease that is highly conserved among vertebrate nidoviruses (coronaviruses and arteriviruses) and plays a critical role in viral replication and transcription. Here, we found that PDCoV nsp15 significantly inhibits Sendai virus (SEV)-induced IFN-β production. PDCoV nsp15 disrupts the phosphorylation and nuclear translocation of NF-κB p65 subunit, but not antagonizes the activation of transcription factor IRF3. Interestingly, site-directed mutagenesis found that PDCoV nsp15 mutants (H129A, H234A, K269A) lacking endoribonuclease activity also suppress SEV-induced IFN-β production and NF-κB activation, suggesting that the endoribonuclease activity is not required for its ability to antagonize IFN-β production. Taken together, our results demonstrate that PDCoV nsp15 is an IFN antagonist and it inhibits interferon-β production via an endoribonuclease activity-independent mechanism.

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that causes watery diarrhea, vomiting and mortality in newborn piglets. Previous studies have suggested that PDCoV infection antagonizes RIG-I-like receptor (RLR)-mediated IFN-β production to evade host innate immune defense, and PDCoV-encoded nonstructural protein nsp5 and accessory protein NS6 are associated with this process. However, whether the structural protein(s) of PDCoV also antagonize IFN-β production remains unclear. In this study, we found that PDCoV nucleocapsid (N) protein, the most abundant viral structural protein, suppressed Sendai virus (SEV)-induced IFN-β production and transcription factor IRF3 activation, but did not block IFN-β production induced by overexpressing RIG-I/MDA5. Furthermore, study revealed that PDCoV N protein interacted with RIG-I and MDA5 in an in vitro overexpression system and evident interactions between N protein and RIG-I could be detected in the context of PDCoV infection, which interfered with the binding of dsRNA and protein activator of protein kinase R (PACT) to RIG-I. Together, our results demonstrate that PDCoV N protein is an IFN antagonist and utilizes diverse strategies to attenuate RIG-I recognition and activation.

Virus-induced signaling adaptor (VISA), which mediates the production of type I interferon, is crucial for the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling pathway. Upon viral infection, RIG-I recognizes double-stranded viral RNA and interacts with VISA to mediate antiviral innate immunity. However, the mechanisms underlying RIG/VISA-mediated antiviral regulation remain unclear. In this study, we confirmed that receptor for activated C kinase 1 (RACK1) interacts with VISA and attenuates the RIG/VISA-mediated antiviral innate immune signaling pathway. Overexpression of RACK1 inhibited the interferon-β (IFN-β) promoter; interferon-stimulated response element (ISRE); nuclear factor kappa B (NF-κB) activation; and dimerization of interferon regulatory factor 3 (IRF3) mediated by RIG-I, VISA, and TANK-binding kinase 1 (TBK1). A reduction in RACK1 expression level upon small interfering RNA knockdown increased RIG/VISA-mediated antiviral transduction. Additionally, RACK1 disrupted formation of the VISA-tumor necrosis factor receptor-associated factor 2 (TRAF2), VISA-TRAF3, and VISA-TRAF6 complexes during RIG-I/VISA-mediated signal transduction. Additionally, RACK1 enhanced K48-linked ubiquitination of VISA, attenuated its K63-linked ubiquitination, and decreased VISA-mediated antiviral signal transduction. Together, these results indicate that RACK1 interacts with VISA to repress downstream signaling and downregulates virus-induced IFN-β production in the RIG-I/VISA signaling pathway.

Usher syndrome 2A (USH2A) is one of the most common genes associated with Usher syndrome type II (USH2) and nonsyndromic autosomal recessive retinitis pigmentosa (arRP). Here, we describe the generation and characterization of two human induced pluripotent stem cell (hiPSC) lines from a RP patient with compound heterogeneous USH2A variants and a USH2 patient with homozygous USH2A variant. Blood samples were obtained and peripheral blood mononuclear cells (PBMCs) were reprogrammed using the non-integrative Sendai virus to generate the iPSC lines. The established hiPSC lines retained the disease-associated variants and showed normal karyotype, pluripotency and differentiation capacity.

The prevalence of SARS-CoV-2 is a great threat to global public health. However, the relationship between the viral pathogen SARS-CoV-2 and host innate immunity has not yet been well studied. The genome of SARS-CoV-2 encodes a viral protease called 3C-like protease. This protease is responsible for cleaving viral polyproteins during replication. In this investigation, 293T cells were transfected with SARS-CoV-2 3CL and then infected with Sendai virus (SeV) to induce the RIG-I like receptor (RLR)-based immune pathway. q-PCR, luciferase reporter assays, and western blotting were used for experimental analyses. We found that SARS-CoV-2 3CL significantly downregulated IFN-β mRNA levels. Upon SeV infection, SARS-CoV-2 3CL inhibited the nuclear translocation of IRF3 and p65 and promoted the degradation of IRF3. This effect of SARS-CoV-2 3CL on type I IFN in the RLR immune pathway opens up novel ideas for future research on SARS-CoV-2.

Adult hearts have limited regenerative capacity. Hence, after acute myocardial infarction (MI), dead myocardial tissues are digested by immune cells and replaced by fibrosis, leading to ventricular remodeling and heart failure at the chronic stage. Direct reprogramming of the cardiac fibroblasts (CFs) into induced cardiomyocytes (iCMs) with cardiac transcription factors, including Gata4, Mef2c, and Tbx5 (GMT), may have significant potential for cardiac repair. Sendai virus (SeV) vectors expressing GMT have been reported to reprogram the mouse cardiac fibroblasts into iCMs without any risk of insertional mutagenesis. In vivo reprogramming improved the cardiac function after acute MI in immunodeficient mice. However, it is unknown whether the newly generated iCMs could exist in infarct hearts for a prolonged period and SeV-GMT can improve cardiac function after MI at the chronic stage in immunocompetent mice. Here, we show that SeV vectors efficiently infect CFs in vivo and reprogram them into iCMs, which existed for at least four weeks after MI, in fibroblast-linage tracing mice. Moreover, SeV-GMT improved cardiac function and reduced fibrosis and collagen I expression at 12 weeks after MI in immunocompetent mice. Thus, direct cardiac reprogramming with SeV vectors could be a promising therapy for MI.

The negative regulation of antiviral immune responses is essential for the host to maintain homeostasis. Jumonji domain-containing protein 6 (JMJD6) was previously identified with a number of functions during RNA virus infection. Upon viral RNA recognition, retinoic acid-inducible gene-I-like receptors (RLRs) physically interact with the mitochondrial antiviral signaling protein (MAVS) and activate TANK-binding kinase 1 (TBK1) to induce type-I interferon (IFN-I) production. Here, JMJD6 was demonstrated to reduce type-I interferon (IFN-I) production in response to cytosolic poly (I:C) and RNA virus infections, including Sendai virus (SeV) and Vesicular stomatitis virus (VSV). Genetic inactivation of JMJD6 enhanced IFN-I production and impaired viral replication. Our unbiased proteomic screen demonstrated JMJD6 contributes to IRF3 K48 ubiquitination degradation in an RNF5-dependent manner. Mice with gene deletion of JMJD6 through piggyBac transposon-mediated gene transfer showed increased VSV-triggered IFN-I production and reduced susceptibility to the virus. These findings classify JMJD6 as a negative regulator of the host’s innate immune responses to cytosolic viral RNA., Author summary RLRs-mediated signaling needs to be terminated in order to prevent persistent immune responses and adverse effects to the host once the virus has been cleared. In this study, we provide rigorous evidence that JMJD6 negatively regulates RLRs-mediated innate immune responses. We found that JMJD6 recruits RNF5 to induce the K48-linked polyubiquitination and proteasomal degradation of activated IRF3. Genetic inactivation of JMJD6 in cells increases IFN-I production to suppress viral infection. Consistently, in vivo studies show that, compared with WT mice, JMJD6-deficient mice are more resistant to VSV infection with more IFN-I production and reduced viral load in livers. Our findings reveal a novel mechanism to downregulate innate immune responses mediated by RNA viral infection, which allows the host to prevent undue immune responses and sustain homeostasis.

Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus that causes serious vomiting and diarrhea in piglets. Previous work demonstrated that PDCoV infection inhibits type I interferon (IFN) production. Here, we found that ectopic expression of PDCoV nsp10 significantly inhibited Sendai virus (SeV)-induced IFN-β production by impairing the phosphorylation and nuclear translocation of two transcription factors, IRF3 and NF-κB p65 subunit. Interestingly, experiments with truncated mutants and site-directed mutagenesis revealed that PDCoV nsp10 mutants with missing or destroyed zinc fingers (ZFs) domains also impeded SeV-induced IFN-β production, suggesting that nsp10 does not require its ZF domains to antagonize IFN-β production. Further work found that co-expression of nsp10 with nsp14 or nsp16, two replicative enzymes, significantly enhanced the inhibitory effects of nsp10 on IFN-β. Taken together, our results demonstrate that PDCoV nsp10 antagonizes IFN via a ZF-independent mechanism and has a synergistic effect with nsp14 and nsp16 on inhibiting IFN-β production.

Bartter Syndrome (BS) is a group of rare inherited autosome-recessive disease, which can be caused by the gene mutations of sodium-potassium-chloride cotransporter gene (SLC12A1). Here, the urine cells (UCs) derived from a 4-year-old female BS patient with the homozygote SLC12A1 gene mutation p.A244D (c.731C>A) were reprogramming into induced pluripotent stem cells (iPSCs) named WMUi019-A using a commercial Sendai virus reprogramming kit. The pluripotent stem cell markers like OCT4 and SSEA4 can be positively expressed in this iPSC line, which can also be induced to differentiate into three germ layers in vitro and maintain a stable karyotype (46, XY).

Introduction We have developed a lentiviral vector pseudotyped with the F and HN proteins from Sendai virus (rSIV.F/HN) for cystic fibrosis (CF) gene therapy and are now progressing towards a first-in-man clinical trial. Here we assessed the transduction efficiency of rSIV.F/HN expressing EGFP in human bronchial epithelial cells from healthy control (HC) and CF donors grown in air-liquid interface culture (ALI). We also assessed the degree of correction of ion transport by rSIV.F/HN-CFTR in this model. Methods Fully differentiated ALIs (MucilAir, Epithelix) were transduced with rSIV.F/HN-EGFP or Sendai virus (SeV)-GFP and GFP expression was quantified at multiple time points using fluorescence microscopy or flow cytometry. The ion transport in HC, CF, and CF ALIs transduced with rSIV.F/HN-CFTR was measured at 7 days in Ussing chambers (stepwise protocol: chloride buffer as baseline, 100 μM amiloride, 100 μM DIDS, low chloride, 10 μM forskolin/100 μM IBMX, 30 μM ΔCFTR inhibitor-172). Results Transduction efficiency was generally In Ussing chambers, there was no difference in baseline short circuit current between HC and CF ALIs, while forskolin/IBMX-mediated chloride secretion was significantly higher in HC samples compared to CF (HC: 8.9±1.4 µA/cm2, CF: 1.16±0.33 µA/cm2, n=14–17/group). We then assessed whether transduction of CF ALIs with rSIV.F/HN-CFTR was able to correct the chloride transport defect. Chloride transport increased significantly (p Conclusion These data suggest that ex vivo transduction efficiency of differentiated human ALIs is low and may not reflect the in vivo performance of gene transfer agents. However, even at this low transduction efficiency, functional correction of ~40% of chloride transport was achieved in CF patient-derived ALI cultures following transduction with rSIV.F/HN-CFTR.

Surfactant protein B (SPB) deficiency is a severe monogenic interstitial lung disorder that leads to loss of life in infants as a result of alveolar collapse and respiratory distress syndrome. The development and assessment of curative therapies for the deficiency are limited by the general lack of well-characterized and physiologically relevant in vitro models of human lung parenchyma. Here, we describe a new human surfactant air-liquid interface (SALI) culture model based on H441 cells, which successfully recapitulates the key characteristics of human alveolar cells in primary culture as evidenced by RNA and protein expression of alveolar cell markers. SALI cultures were able to develop stratified cellular layers with functional barrier properties that are stable for at least 28 days after air-lift. A SFTPB knockout model of SPB deficiency was generated via gene editing of SALI cultures. The SFTPB-edited SALI cultures lost expression of SPB completely and showed weaker functional barrier properties. We were able to correct this phenotype via delivery of a lentiviral vector pseudotyped with Sendai virus glycoproteins F/HN expressing SPB. We believe that SALI cultures can serve as an important in vitro research tool to study human alveolar epithelium, especially for the development of advanced therapy medicinal products targeting monogenic disorders., Graphical Abstract, Munis et al. describe a new human pulmonary air-liquid interface (ALI) cell culture model that recapitulates alveolar cell markers, is physiologically relevant, and facilitates high-throughput assessment of therapeutic interventions. They demonstrate that surfactant protein B deficiency, modeled via SFTPB gene knockout, can be reversed by rSIV.F/HN-mediated gene therapy.

Antiviral innate immune response to RNA virus infection is supported by Pattern-Recognition Receptors (PRR) including RIG-I-Like Receptors (RLR), which lead to type I interferons (IFNs) and IFN-stimulated genes (ISG) production. Upon sensing of viral RNA, the E3 ubiquitin ligase TNF Receptor-Associated Factor-3 (TRAF3) is recruited along with its substrate TANK-Binding Kinase (TBK1), to MAVS-containing subcellular compartments, including mitochondria, peroxisomes, and the mitochondria-associated endoplasmic reticulum membrane (MAM). However, the regulation of such events remains largely unresolved. Here, we identify TRK-Fused Gene (TFG), a protein involved in the transport of newly synthesized proteins to the endomembrane system via the Coat Protein complex II (COPII) transport vesicles, as a new TRAF3-interacting protein allowing the efficient recruitment of TRAF3 to MAVS and TBK1 following Sendai virus (SeV) infection. Using siRNA and shRNA approaches, we show that TFG is required for virus-induced TBK1 activation resulting in C-terminal IRF3 phosphorylation and dimerization. We further show that the ability of the TRAF3-TFG complex to engage mTOR following SeV infection allows TBK1 to phosphorylate mTOR on serine 2159, a post-translational modification shown to promote mTORC1 signaling. We demonstrate that the activation of mTORC1 signaling during SeV infection plays a positive role in the expression of Viperin, IRF7 and IFN-induced proteins with tetratricopeptide repeats (IFITs) proteins, and that depleting TFG resulted in a compromised antiviral state. Our study, therefore, identifies TFG as an essential component of the RLR-dependent type I IFN antiviral response., Author summary Antiviral innate immune response is the first line of defence against the invading viruses through type I interferon (IFN) signaling. However, viruses have devised ways to target signaling molecules for aberrant IFN response and worsen the disease outcome. As such, deciphering the roles of new regulators of innate immunity could transform the antiviral treatment paradigm by introducing novel panviral therapeutics designed to reinforce antiviral host responses. This could be of great use in fighting recent outbreaks of severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome MERS-CoV, and the more recent SARS-CoV-2 causing the COVID-19 pandemic. However, aberrant activation of such pathways can lead to detrimental consequences, including autoimmune diseases. Regulation of type I IFN responses is thus of paramount importance. To prevent an uncontrolled response, signaling events happen in discrete subcellular compartments, therefore, distinguishing sites involved in recognition of pathogens and those permitting downstream signaling. Here, we show TFG as a new regulator of type I IFN response allowing the efficient organization of signaling molecules. TFG, thus, further substantiates the importance of the protein trafficking machinery in the regulation of optimal antiviral responses. Our findings have implications for both antiviral immunity and autoimmune diseases.

Niemann-Pick disease type C1 (NPC1) is a rare inherited lipid storage disorder caused by mutations in the NPC1 gene. Mutations lead to impaired lipid trafficking and subsequently to accumulation of cholesterol and sphingolipids. NPC1-patients present variable multisystemic symptoms, including neurological deficits. Here, we describe the generation of human iPSC lines obtained from fibroblasts of a male individual, carrying the homozygous mutation p.I1061T, and an unrelated and healthy male individual. A non-integrating Sendai virus system, containing KLF4, OCT3/4, SOX2 and C-MYC, was used for reprogramming. These cell lines provide a valuable resource for studying the pathophysiology of multisystemic NPC1-disease.

We established a human induced pluripotent stem cells (hiPSC) line (CMCi002-A) from peripheral blood mononuclear cells (PBMCs) of 29-year-old male with Gitelman's syndrome (GIT) caused by the mutation of solute carrier family 12 member 3 (SLC12A3) gene using Sendai virus. The GIT-hiPSCs showed a typical human embryonic stem cell like morphology and expressed all pluripotency-associated markers, exhibited normal karyotype and were capable of differentiating into cells representative of three germ layers.

Respiratory infections, like the current COVID‐19 pandemic, target epithelial cells in the respiratory tract. Alveolar macrophages (AMs) are tissue‐resident macrophages located within the lung. They play a key role in the early phases of an immune response to respiratory viruses. AMs are likely the first immune cells to encounter SARS‐CoV‐2 during an infection, and their reaction to the virus will have a profound impact on the outcome of the infection. Interferons (IFNs) are antiviral cytokines and among the first cytokines produced upon viral infection. In this study, AMs from non‐infectious donors are challenged with SARS‐CoV‐2. We demonstrate that challenged AMs are incapable of sensing SARS‐CoV‐2 and of producing an IFN response in contrast to other respiratory viruses, like influenza A virus and Sendai virus, which trigger a robust IFN response. The absence of IFN production in AMs upon challenge with SARS‐CoV‐2 could explain the initial asymptotic phase observed during COVID‐19 and argues against AMs being the sources of pro‐inflammatory cytokines later during infection., Alveolar macrophages produce interferons and activate interferon stimulated genes when challenged with influenza A virus or Sendai virus, but not when challenged with SARS‐CoV‐2, suggesting that its genomic RNA is undetectable for innate immune sensors.

Peripheral blood mononuclear cells (PBMCs) from a McArdle patient carrying a homozygous mutation in the PYGM gene: c.2392 T > C; p.Trp798Arg were used for the generation of the human iPSC line, IISHDOi007-A. For the delivery of the reprogramming factors Oct3/4, Sox2, Klf4, and c-Myc, a non-integrative methodology that implies the use of Sendai virus has been applied.

We describe the generation and characterisation of four human induced pluripotent stem cell (iPSC) lines from peripheral blood mononuclear cells (PBMC) from individuals with neurofibromatosis type (NF1). PBMC reprogramming was performed using a non-integrative Sendai virus containing the reprogramming factors OCT4, SOX2, MYC and KLF4. All iPSC lines exhibited a normal karyotype, and pluripotency was validated by flow cytometry (EPCAM, TRA-1-81, SSEA1 and CD9) and immunofluorescence (OCT4 and Nanog). Differentiation of the cells into the three embryonic germ layers was confirmed using immunofluorescence. These iPSC lines are a valuable pre-clinical resource to study the molecular mechanisms underlying NF1.

ANCA-associated RPGN leads to renal failure through systemic vasculitis and diffuse crescentic glomerulonephritis. MPO-ANCA-RPGN patients are highly susceptible to infections. Our aim in this study was to uncover reasons why these patients were susceptible to infections. We analyzed various aspects of type I interferon system including HVJ-stimulated IFN-α producing capacity and plasmacytoid dendritic cell (pDC) number in whole blood in MPO-ANCA-RPGN patients. Compared with healthy subjects, MPO-ANCA-RPGN patients showed impaired HVJ-stimulated IFN-α producing capacity and lower pDC number with or without glucocorticoid treatment. Immuno-histological staining of MPO-ANCA-RPGN kidney samples revealed a few but apparent pDC in T cell infiltrating regions even in patients with low pDC number in their peripheral blood. Patients' low HVJ-stimulated IFN-α producing capacity and pDC numbers persisted even after patients underwent several years of treatment. Former infection was determined using patients' serum BPI, Lamp-2 and Calprotectin, since they are reflective of a history of infection. These markers were higher in MPO-ANCA-RPGN patients than in healthy subjects. These results indicate that impaired HVJ-stimulated IFN-α production as well as dysfunction of the IFN system might have resulted from a previous bout of infection and can be partially implicated in patients' long-term susceptibility and vulnerability to infection.

The gene mutations of the collagen type IV alpha 5 chain (COL4A5) can lead to the inherited haematuria to end-stage renal disease X-linked Alport syndrome (X-LAS). The urine cells of a 5-year-old male X-LAS patient carrying a hemizygous COL4A5 gene mutation p.G1433V (c.4298G>T) were reprogrammed to induced pluripotent stem cells (iPSCs) with Sendai virus reprogramming kit containing OCT4, SOX2, c-MYC, and KLF4 Yamanaka factors. The generated iPSC line WMUi015-A stably expressed pluripotent markers, maintained a normal karyotype (46, XY), and had differentiation potential into three germ layers in vitro.

Peripheral blood was extracted from a 48-year old healthy male donor. Induced pluripotent stem cells (iPSC) were reprogrammed by sendai virus encoding Klf-4, c-Myc, Oct-4, and Sox-2. The iPSC line showed pluripotency, which was verified by immunofluorescence staining. The iPSC line showed normal karyotype, and could form embryoid bodies in vitro and differentiate into the 3 germ layers in vivo. This cell line can be served as healthy control for studying inherited disease.

Peripheral blood was extracted from a 45-year old female patient clinically diagnosed with Stickler syndrome harboring a heterozygous splicing mutation in COL2A1 (NM_033150, IVS22-1C>T). Induced pluripotent stem cells (iPSC) were reprogrammed by sendai virus encoding Klf-4, c-Myc, Oct-4, and Sox-2. The iPSC line showed pluripotency, which was verified by immunofluorescence staining. The iPSC line showed normal karyotype, and could form embryoid bodies in vitro and differentiate into the 3 germ layers in vivo. This in vitro cellular model can be used to study the pathogenesis underlying Stickler syndrome.

Marfan syndrome (MFS) is a connective-tissue disorder caused mainly by heterozygous mutations in the FBN1 gene that encodes fibrillin-1. In this study, human induced pluripotent stem cell (iPSC) line ZZUSAHi003-A was generated from peripheral blood mononuclear cells (PBMCs) isolated from a female patient with MFS using non-integrative Sendai virus. The iPSC line carried the FBN1 gene mutation, showed the normal karyotype, expressed pluripotency markers and had the capacity to differentiate into three germ layers in vivo. This iPS line, ZZUSAHi003-A, could serve as a useful tool for studying pathogenic mechanisms of MFS.

The gene mutations of the chloride channel gene (CLCN5) can lead to the inherited X-linked Dent disease (X-Dent). The urine cells of a 4-year-old male X-Dent patient with the hemizygous CLCN5 gene mutation p.R718* (c.2152C > T) were reprogrammed into induced pluripotent stem cells (iPSCs) using integration free Sendai virus reprogramming system. The generated iPSCs stably expressed pluripotent stem cell markers and can be induced to differentiate into three germ layers in vitro. The karyotype of the generated iPSCs was normal (46, XY).