Dynamic bidirectional regulation of NLRC3 and gammaherpesviruses during viral latency in B lymphocytes

While most NOD-like receptors (NLRs) are predominately expressed by innate immune cells, NLRC3, an inhibitory NLR of immune signaling, exhibits the highest expression in lymphocytes. The role of NLRC3 or any NLRs in B lymphocytes is completely unknown. Gammaherpesviruses, including human Epstein-Barr virus (EBV) and murine gammaherpesvirus 68 (MHV-68), establish latent infection in B lymphocytes, which requires elevated NF-κB. This study shows that during latent EBV infection of human B cells, viral-encoded latent membrane protein 1 (LMP1) decreases NLRC3 transcript. LMP1-induced-NF-κB activation suppresses the promoter activity of NLRC3 via p65 binding to the promoter. Conversely, NLRC3 inhibits NF-κB activation by promoting the degradation of LMP1 in a proteasome-dependent manner. In vivo, MHV-68 infection reduces Nlrc3 transcripts in splenocytes, and Nlrc3-deficient mice show greater viral latency than controls. These results reveal a bidirectional regulatory circuit in B lymphocytes, where viral latent protein LMP1 reduces NLRC3 expression, while NLRC3 disrupts gammaherpesvirus latency, which is an important step for tumorigenesis.

Skin manifestations and clinical features of drug reaction with eosinophilia and systemic symptoms (DRESS): A retrospective multicenter study of 125 patients

BACKGROUND

Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe adverse drug reaction generally accompanied by skin manifestations as the first and most frequent symptoms. However, skin manifestations and associated clinical features of DRESS have not been fully explored and evaluated.

OBJECTIVES

This study aimed to describe the skin manifestations of DRESS in detail and analyze their association with demographic characteristics and extra-cutaneous clinical features.

METHODS

We conducted this retrospective study on patients with DRESS diagnosed between September 2009 and August 2021 at three medical institutes and validated using the RegiSCAR score. Data regarding demographics, skin manifestations, and clinical characteristics were retrieved through thorough chart reviews.

RESULTS

Among 182 potential cases of DRESS, the validated 125 cases were analyzed. A widespread rash extending over more than 50% of the body surface area was observed in 122 patients (97.6%) and typical facial edema was experienced by 67 patients (53.6%). Polymorphous maculopapules were the most common rash morphology (106, 84.8%): specifically, exfoliative (59, 47.2%), urticarial (57, 45.6%), and purpuric forms (39, 31.2%) were common. Mucosal involvement was observed in 41 patients (32.8%). Patients with carboxamide antiepileptics (carbamazepine and oxcarbazepine) experienced more edema (P = .014) and typical facial edema than those with allopurinol (P = .021). The RegiSCAR score was higher in patients with purpura (P < .01).

CONCLUSIONS

Skin manifestations of DRESS exhibit a wide range of skin lesions and can vary according to the culprit drugs. Early suspicion and prompt intervention are needed to improve prognosis.

Fenofibrate rapidly decreases hepatic lipid and glycogen storage in neonatal mice with glycogen storage disease type Ia

Glycogen storage disease type Ia (GSD Ia) is caused by autosomal mutations in glucose-6-phosphatase α catalytic subunit (G6PC) and can present with severe hypoglycemia, lactic acidosis and hypertriglyceridemia. In both children and adults with GSD Ia, there is over-accumulation of hepatic glycogen and triglycerides that can lead to steatohepatitis and a risk for hepatocellular adenoma or carcinoma. Here, we examined the effects of the commonly used peroxisomal proliferated activated receptor α agonist, fenofibrate, on liver and kidney autophagy and lipid metabolism in 5-day-old G6pc -/- mice serving as a model of neonatal GSD Ia. Five-day administration of fenofibrate decreased the elevated hepatic and renal triglyceride and hepatic glycogen levels found in control G6pc -/- mice. Fenofibrate also induced autophagy and promoted β-oxidation of fatty acids and stimulated gene expression of acyl-CoA dehydrogenases in the liver. These findings show that fenofibrate can rapidly decrease hepatic glycogen and triglyceride levels and renal triglyceride levels in neonatal G6pc -/- mice. Moreover, since fenofibrate is an FDA-approved drug that has an excellent safety profile, our findings suggest that fenofibrate could be a potential pharmacological therapy for GSD Ia in neonatal and pediatric patients as well as for adults. These findings may also apply to non-alcoholic fatty liver disease, which shares similar pathological and metabolic changes with GSD Ia.

A DNA-sensing-independent role of a nuclear RNA helicase, DHX9, in stimulation of NF-κB-mediated innate immunity against DNA virus infection

DExD/H-box helicase 9 (DHX9), or RNA helicase A (RHA), is an abundant multifunctional nuclear protein. Although it was previously reported to act as a cytosolic DNA sensor in plasmacytoid dendritic cells (pDCs), the role and molecular mechanisms of action of DHX9 in cells that are not pDCs during DNA virus infection are not clear. Here, a macrophage-specific knockout and a fibroblast-specific knockdown of DHX9 impaired antiviral innate immunity against DNA viruses, leading to increased virus replication. DHX9 enhanced NF-κB–mediated transactivation in the nucleus, which required its ATPase-dependent helicase (ATPase/helicase) domain, but not the cytosolic DNA-sensing domain. In addition, DNA virus infection did not induce cytoplasmic translocation of nuclear DHX9 in macrophages and fibroblasts. Nuclear DHX9 was associated with a multiprotein complex including both NF-κB p65 and RNA polymerase II (RNAPII) in chromatin containing NF-κB–binding sites. DHX9 was essential for the recruitment of RNAPII rather than NF-κB p65, to the corresponding promoters; this function also required its ATPase/helicase activity. Taken together, our results show a critical role of nuclear DHX9 (as a transcription coactivator) in the stimulation of NF-κB–mediated innate immunity against DNA virus infection, independently of DHX9’s DNA-sensing function.

Bezafibrate Enhances AAV Vector-Mediated Genome Editing in Glycogen Storage Disease Type Ia

Glycogen storage disease type Ia (GSD Ia) is a rare inherited disease caused by mutations in the glucose-6-phosphatase (G6Pase) catalytic subunit gene (G6PC). Absence of G6Pase causes life-threatening hypoglycemia and long-term complications because of the accumulations of metabolic intermediates. Bezafibrate, a pan-peroxisome proliferator-activated receptor (PPAR) agonist, was administered in the context of genome editing with a zinc-finger nuclease-containing vector (AAV-ZFN) and a G6Pase donor vector (AAV-RoG6P). Bezafibrate treatment increased survival and decreased liver size (liver/body mass, p < 0.05) in combination with genome editing. Blood glucose has higher (p < 0.05) after 4 h of fasting, and liver glycogen accumulation (p < 0.05) was lower in association with higher G6Pase activity (p < 0.05). Furthermore, bezafibrate-treated mice had increased numbers of G6PC transgenes (p < 0.05) and higher ZFN activity (p < 0.01) in the liver compared with controls. PPAR-α expression was increased and PPAR-γ expression was decreased in bezafibrate-treated mice. Therefore, bezafibrate improved hepatocellular abnormalities and increased the transduction efficiency of AAV vector-mediated genome editing in liver, whereas higher expression of G6Pase corrected molecular signaling in GSD Ia. Taken together, bezafibrate shows promise as a drug for increasing AAV vector-mediated genome editing.

Incidence and Risk Factors of Immediate Hypersensitivity Reactions Associated With Low-Osmolar Iodinated Contrast Media: A Longitudinal Study Based on a Real-Time Monitoring System

OBJECTIVES

We investigated the incidence of immediate hypersensitivity reaction (HSR) caused by different types of low-osmolar contrast media (LOCM) and cumulative exposure to LOCM.

METHODS

This cohort study included all consecutive patients who underwent LOCM-enhanced computed tomography from 2012 through 2014. We assessed 5 LOCM (iobitridol, iohexol, iomeprol, iopamidol, and iopromide). All patients were monitored for adverse events, and new symptoms and signs were recorded in real time using the Contrast Safety Monitoring and Management System (CoSM2oS).

RESULTS

The overall incidence of immediate HSR to LOCM was 0.97% (2004 events resulting from 205 726 exposures). Incidence differed significantly depending on whether the patient had a previous history of HSR to LOCM (0.80% in patients with no history and 16.99% in patients with a positive history of HSR to LOCM, P=.001). The incidence of HSR to individual LOCM ranged from 0.72% (iohexol) to 1.34% (iomeprol), although there were no significant differences across the 5 LOCM. A longitudinal analysis demonstrated that the incidence of HSR increased gradually with more frequent previous exposure to LOCM (HR=2.006 [95%CI, 1.517-2.653], P<.001). However, this cumulative increase in risk was observed in patients who had experienced HSR to LOCM, but not in those who had not.

CONCLUSION

The incidence of HSR did not differ significantly across the 5 LOCM assessed in the study. Repeated exposure to LOCM did not increase the risk of HSR among patients who had never experienced HSR to LOCM.

BST2 inhibits infection of influenza A virus by promoting apoptosis of infected cells

BST2 is an antiviral factor that inhibits the release of enveloped virus at the plasma membrane via an unusual topology in which its N-terminal is in the cytosol while its C-terminal is anchored by glycophosphatidylinositol (GPI). BST2-deficient cells showed substantially higher release of virions than wild type cells. Influenza-infected BST2-deficient cells showed greatly reduced cytopathic effect (CPE) than wild type cells despite their generally robust virus production. This finding prompted us to determine whether BST2 was involved in the apoptotic process of virus-infected host cells. Our results revealed that BST2 might be involved in IRE1α-mediated ER stress pathway by increasing spliced form XBP-1. Consequently, levels of cytochrome C, caspase-3, caspase-9, and PARP as representative molecules of apoptosis were significantly increased in wild type cells than those in BST2-deficient cells. These results suggest that BST2 might participate in innate host defense by augmenting ER-stress-induced apoptotic signaling to inhibit the replication and spread of virus.

Structure-based mechanism of action of a viral poly(ADP-ribose) polymerase 1-interacting protein facilitating virus replication

Poly(ADP-ribose) polymerase 1 (PARP-1), an enzyme that modifies nuclear proteins by poly(ADP-ribosyl)ation, regulates various cellular activities and restricts the lytic replication of oncogenic gammaherpesviruses by inhibiting the function of replication and transcription activator (RTA), a key switch molecule of the viral life cycle. A viral PARP-1-interacting protein (vPIP) encoded by murine gammaherpesvirus 68 (MHV-68) orf49 facilitates lytic replication by disrupting interactions between PARP-1 and RTA. Here, the structure of MHV-68 vPIP was determined at 2.2 Å resolution. The structure consists of 12 α-helices with characteristic N-terminal β-strands (Nβ) and forms a V-shaped-twist dimer in the asymmetric unit. Structure-based mutagenesis revealed that Nβ and the α1 helix (residues 2-26) are essential for the nuclear localization and function of vPIP; three residues were then identified (Phe5, Ser12 and Thr16) that were critical for the function of vPIP and its interaction with PARP-1. A recombinant MHV-68 harboring mutations of these three residues showed severely attenuated viral replication both in vitro and in vivo. Moreover, ORF49 of Kaposi's sarcoma-associated herpesvirus also directly interacted with PARP-1, indicating a conserved mechanism of action of vPIPs. The results elucidate the novel molecular mechanisms by which oncogenic gammaherpesviruses overcome repression by PARP-1 using vPIPs.

Severe Asthma Phenotypes Classified by Site of Airway Involvement and Remodeling via Chest CT Scan

OBJECTIVES

This study aimed to establish a system that can classify severe asthma on the basis of airway remodeling patterns visualizedusing computed tomography (CT) images and to evaluate the clinical characteristics of individual image-based subtypes.

METHODS

Chest CT images from severe asthma patients were retrospectively evaluated to classify phenotypes by site of airway involvement and remodeling. The association between radiologic subtypes and clinical characteristics was assessed.

RESULTS

Of 91 patients with severe asthma, 74 (81.3%) exhibited abnormal radiologic findings, including bronchial wall thickening (BT), mucus plugging (MP), and bronchiectasis (BE). The severity of BT and the extent of MP were independently associated with peripheral blood eosinophil count (P=.012, r2=0.112) and sputum eosinophil count (P=.022, r2=0.090), respectively. The large-to-medium airway remodeling type, which showed diffuse BT combined with MP and BE, accounted for 44% of patients and revealed higher peripheral blood eosinophil counts than other types. In the small airway remodeling type, which accounted for 6.6% of patients, we observed a higher rate of fixed airflow obstruction, along with a predominance of males and smokers and more frequent use of controller medication than other phenotypes. In 26% of patients with severe asthma, no prominent airway remodeling was observed (near-normal type); the near-normal type required oral corticosteroids less frequently than the large-to-medium airway and small airway remodeling types.

CONCLUSIONS

Depending on the site of airway involvement and remodeling pattern, 3 different structural types can be distinguished in chest CT findings from patients with severe asthma. Remodeling in large-to-medium sized airways revealed an association with systemic eosinophilic inflammation in patients with severe asthma.

The structure of the pleiotropic transcription regulator CodY provides insight into its GTP-sensing mechanism

GTP and branched-chain amino acids (BCAAs) are metabolic sensors that are indispensable for the determination of the metabolic status of cells. However, their molecular sensing mechanism remains unclear. CodY is a unique global transcription regulator that recognizes GTP and BCAAs as specific signals and affects expression of more than 100 genes associated with metabolism. Herein, we report the first crystal structures of the full-length CodY complex with sensing molecules and describe their functional states. We observed two different oligomeric states of CodY: a dimeric complex of CodY from Staphylococcus aureus with the two metabolites GTP and isoleucine, and a tetrameric form (apo) of CodY from Bacillus cereus. Notably, the tetrameric state shows in an auto-inhibitory manner by blocking the GTP-binding site, whereas the binding sites of GTP and isoleucine are clearly visible in the dimeric state. The GTP is located at a hinge site between the long helical region and the metabolite-binding site. Together, data from structural and electrophoretic mobility shift assay analyses improve understanding of how CodY senses GTP and operates as a DNA-binding protein and a pleiotropic transcription regulator.

Influenza A Virus NS1 Protein Inhibits the NLRP3 Inflammasome

The inflammasome is a molecular platform that stimulates the activation of caspase-1 and the processing of pro-interleukin (IL)-1β and pro-IL-18 for secretion. The NOD-like receptor family, pyrin domain containing 3 (NLRP3) protein is activated by diverse molecules and pathogens, leading to the formation of the NLRP3 inflammasome. Recent studies showed that the NLRP3 inflammasome mediates innate immunity against influenza A virus (IAV) infection. In this study, we investigated the function of the IAV non-structural protein 1 (NS1) in the modulation of NLRP3 inflammasome. We found that NS1 proteins derived from both highly pathogenic and low pathogenic strains efficiently decreased secretion of IL-1β and IL-18 from THP-1 cells treated with LPS and ATP. NS1 overexpression significantly impaired the transcription of proinflammatory cytokines by inhibiting transactivation of the nuclear factor-κB (NF-κB), a major transcription activator. Furthermore, NS1 physically interacted with endogenous NLRP3 and activation of the NLRP3 inflammasome was abrogated in NS1-expressing THP-1 cells. These findings suggest that NS1 downregulates NLRP3 inflammasome activation by targeting NLRP3 as well as NF-κB, leading to a reduction in the levels of inflammatory cytokines as a viral immune evasion strategy.

Phosphatidylinositol-3-kinase and Akt are required for RIG-I-mediated anti-viral signalling through cross-talk with IPS-1

Retinoic acid-inducible gene I (RIG-I) is a cytosolic pattern-recognition receptor that recognizes viruses and triggers anti-viral immune responses. Activation of intracellular RIG-I signalling is mediated through interferon-β (IFN-β) promoter stimulator-1 (IPS-1), an adaptor of RIG-I, which induces IFN regulatory factor (IRF) 3 activation and type I IFN expression. The phosphatidylinositol-3-kinase (PI3K) and Akt pathway is activated in host immune cells upon viral infection. However, the mechanism as to how they work in RIG-I signalling has not been fully elucidated. Therefore, we investigated the role of PI3K and Akt in the regulation of RIG-I-mediated IRF3 activation and type I IFN expression in macrophages. Our results show that Sendai virus infection, which is recognized by RIG-I, led to IRF3 activation and IFN-β expression and these responses were attenuated by the PI3K inhibitor (LY294002) and an Akt dominant-negative mutant in the macrophage cell line(RAW264.7). IRF3 phosphorylation and dimerization as well as IFN-β expression induced by a synthetic RIG-I agonist, short poly(I:C), were suppressed by LY294002 or siRNA-Akt in bone marrow-derived macrophages. Suppression of PI3K and Akt using a dominant-negative mutant and siRNA knockdown resulted in attenuation of IRF3 activation and IFN-β expression induced by RIG-I itself or its adaptor, IPS-1. Association of Akt with IPS-1 increased with short poly(I:C) stimulation and required the pleckstrin homology domain of Akt and caspase-recruitment domain in IPS-1. Collectively, our results show that PI3K and Akt are required downstream of IPS-1 for RIG-I-mediated anti-viral immune responses. The results describe a novel, interactive relationship between RIG-I downstream signalling molecules resulting in efficient anti-viral immunity.

Antiviral activity of angelicin against gammaherpesviruses

Human gammaherpesviruses including Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are important pathogens as they persist in the host and cause various malignancies. However, few antiviral drugs are available to efficiently control gammaherpesvirus replication. Here we identified the antiviral activity of angelicin against murine gammaherpesvirus 68 (MHV-68), genetically and biologically related to human gammaherpesviruses. Angelicin, a furocoumarin naturally occurring tricyclic aromatic compound, efficiently inhibited lytic replication of MHV-68 in a dose-dependent manner following the virus entry. The IC50 of angelicin antiviral activity was estimated to be 28.95μM, while the CC50 of angelicin was higher than 2600μM. Furthermore, incubation with angelicin efficiently inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced lytic replication of human gammaherpresviruses in both EBV- and KSHV-infected cells. Taken together, these results suggest that MHV-68 can be a useful tool to screen novel antiviral agents against human gammaherepsviruses and that angelicin may provide a lead structure for the development of antiviral drug against gammaherpesviruses.

Persistent infection of a gammaherpesvirus in the central nervous system

Human gammaherpesvirus infections of the central nervous system (CNS) have been linked to various neurological diseases. Murine gammaherpesvirus 68 (MHV-68), genetically related and biologically similar to human gammaherpesviruses, infects the CNS in laboratory mice. However, viral persistency of MHV-68 has not been studied following CNS infection. In this study, we undertook the noninvasive bioluminescence imaging of a recombinant MHV-68 expressing the firefly luciferase (M3FL) to monitor virus progression after CNS infection. The M3FL virus inoculated in the brain systemically spread to the abdominal area in bioluminescence imaging, which was further confirmed by detection of viral genome and transcripts. The disseminated wild-type virus established latency in the spleen. Moreover, the treatment of the infected mice with CsA induced reactivation of latent MHV-68 from the brain and the spleen. Our results suggest that MHV-68 may persist both inside and outside the CNS once it gains access to the CNS.

Normal C1 inhibitor mRNA expression level in type I hereditary angioedema patients: newly found C1 inhibitor gene mutations

BACKGROUND

C1 esterase inhibitor (C1INH) plays a key role in the classical pathway of the complement cascade. Mutations in this gene cause a decreased level of antigenic (type I hereditary angioedema, HAE) or functional (type II HAE) C1INH.

OBJECTIVE

To find novel mutations in C1INH and evaluate the expression of C1INH gene in HAE patients.

METHODS

Direct sequencing mutation analysis was performed for genomic DNA from three unrelated families (14 HAE patients and 18 family members). Genomic DNA from one family was also analyzed for larger genomic rearrangements, using Southern blotting analysis. We used real-time quantitative polymerase chain reaction (PCR) to evaluate C1INH mRNA expression level.

RESULTS

Four mutations in exons (2,311 T-->C, 14,034 G-->A, 16,830 G-->A, and 16,979-16,980 G insertion) and four in introns (738 G-->A, 8,531 A-->G, 14,254 A-->G, and 14,337-14,378 TT deletion) were found. Interestingly, all of the nine patients in one family share the same mutation of Gly345Arg (14,034 G-->A) in the seventh exon. In another family, a single base mutation near the splice site (14,254 A-->G) was found in all of the three patients. In the last family, although a significant mutation was not found by direct sequencing, patients showed an abnormal 16 kb fragment in addition to the normal allele (21 kb Bcl I fragment). The C1INH mRNA expression of HAE patients in two families was not significantly different compared with that of normal controls.

CONCLUSION

The two novel exonal mutations (G-->A and A-->G) and one large gene deletion were associated with the clinical phenotypes of HAE. Considering the normal C1INH mRNA levels but below normal protein levels in two families, their phenotypes would be associated with the post-translational defect.

Systemic lupus erythematosus complicated with cerebral venous sinus thrombosis : a report of two cases

A rare manifestation of systemic lupus erythematosus (SLE) is cerebral venous sinus thrombosis (CVST), in which early diagnosis and aggressive therapy are of prime importance for favorable outcome. The pathogenesis of CVST is largely unknown, but it is thought to be caused by cerebral vasculitis, antiphospholipid antibodies or other conditions associated with enhanced coagulability. We describe two cases of SLE with CVST which were not associated with antiphospholipid antibodies. Both cases were treated with immunosuppressants (intravenous methylprednisolone and cyclophosphamide pulse therapy) and anticoagulant drugs (heparin and subsequent maintenance therapy with warfarin). There was a marked improvement of neurologic symptoms with the disappearance of thrombus in a follow-up MRI. The possibility of CVST should be considered in any patients with SLE who show neuropsychiatric manifestations.

Rheumatoid arthritis associated with myelodysplastic syndrome: a case report

Myelodysplastic syndromes (MDS) are a group of refractory anemias resulting from a clonal stem cell disorder often associated with cytogenetic abnormalities. There is increasing recognition of immunological abnormalities in patients with MDS, including defective B- and T-cell function, hyper- or hypogammaglobulinemia and monoclonal gammopathy. MDS have been associated with Sjögren's syndrome, polymyalgia rheumatica, relapsing polychondritis and systemic lupus erythematosus. Although there may be various rheumatologic features, including acute arthritis in MDS, chronic inflammatory arthritis is uncommonly combined. There have been a few reports that described cases of rheumatoid arthritis (RA) concurrent with MDS, but advanced rheumatoid arthritis with typical joint deformities has rarely been reported. We report a case of rheumatoid arthritis with atlantoaxial subluxation combined with refractory anemia in a 31-year-old woman.