Myxovirus Resistance Protein A Research Articles

A long-term follow-up study on biochemical and clinical biomarkers of response to interferon beta-1b treatment in relapsing-remitting multiple sclerosis.

While interferon beta-1b (IFN-β-1b) is still a commonly used disease-modifying drug in the treatment of multiple sclerosis (MS), therapeutic possibilities are expanding, and treatment failure should be identified early. Markers to predict response to IFN-β-1b, either clinical or biochemical, are therefore urgently needed. Interferon-induced proteins, including viperin, suppressor of cytokine signaling 3 (SOCS3), ubiquitin specific peptidase-18 (USP18), and myxovirus resistance protein A (MxA), are possible markers of IFN-β-1b bioavailability and treatment response. To evaluate viperin, SOCS3, USP18 and MxA as markers of treatment response in Polish IFN-β-1btreated patients with MS. In 45 IFN-β-1b-treated Polish patients with MS, serum concentrations of viperin, SOCS3, USP18, and MxA were assessed before and after 24 months of IFN-β-1b treatment. The patients were followed clinically and with magnetic resonance imaging (MRI) for a median of 6.8 years. Low viperin, USP18 and MxA at baseline and 24 months and high SOCS3 at 24 months correlated with higher disease activity up to the 6th year of observation, but only baseline MxA and USP18 were independently related to outcome, with higher concentrations predicting less disease activity in the first 3 years and after the 1st year, respectively. We confirm the predictive value of MxA and propose USP18 as a possible new prognostic biomarker in IFN-β-1btreated MS patients.

Expression of MxA Protein in Triple Negative Breast Cancer and its Relationship with Prognosis

Objective: To explore the expression of human myxovirus resistance protein A (MxA) in triple negative breast cancer (TNBC) and its relationship with prognosis. Methods: 144 cases of TNBC confirmed by pathology before or after surgery from January 2014 to January 2017 in the First Central Hospital of Baoding City were retrospectively collected. Western blotting was used to detect the expression of MxA protein in TNBC and adjacent breast tissues. According to the expression of MxA protein, 144 TNBC patients were divided into low MxA protein expression group (n = 91) and MxA protein high expression group (n = 53) for subsequent comparison of prognosis of patients in between these two groups. Results: The expression of MxA protein in TNBC tissue was lower than that of adjacent breast tissue, and the difference was statistically significant (P<0.05). The patients in high MxA expression group had higher loco-regional recurrence-free rate, disease-free survival (DFS) rate, and overall survival (OS) rate than those in low MxA expression group for 3 years. On the other hand, the distant metastasis rate was lower in the high expression group compared to that in the low MxA expression group, and the difference was statistically significant (P<0.05). Conclusion: In triple-negative breast cancer, high MxA expression is a potential predictor of TNBC prognosis.

Prevalence of respiratory viruses and antiviral MxA responses in children with febrile urinary tract infection

Blood myxovirus resistance protein A (MxA) has broad antiviral activity, and it is a potential biomarker for symptomatic virus infections. Limited data is available of MxA in coinciding viral and bacterial infections. We investigated blood MxA levels in children hospitalized with a febrile urinary tract infection (UTI) with or without simultaneous respiratory virus infection. We conducted a prospective observational study of 43 children hospitalized with febrile UTI. Nasopharyngeal swab samples were collected at admission and tested for 16 respiratory viruses by nucleic acid detection methods. Respiratory symptoms were recorded, and blood MxA levels were determined. The median age of study children was 4 months (interquartile range, 2–14 months). A respiratory virus was detected in 17 (40%) children with febrile UTI. Of the virus-positive children with febrile UTI, 7 (41%) had simultaneous respiratory symptoms. Blood MxA levels were higher in virus-positive children with respiratory symptoms (median, 778 [interquartile range, 535–2538] μg/L) compared to either virus-negative (155 [94–301] μg/L, P < 0.001) or virus-positive (171 [112–331] μg/L, P = 0.006) children without respiratory symptoms at presentation with febrile UTI. MxA differentiated virus-positive children with respiratory symptoms from virus-negative without symptoms by an area under the receiver operating characteristic curve of 0.96. Respiratory viruses were frequently detected in children with febrile UTI. In UTI with simultaneous respiratory symptoms, host antiviral immune response was demonstrated by elevated blood MxA protein levels. MxA protein could be a robust biomarker of symptomatic viral infection in children with febrile UTI.

Interferon-β exposure induces a fragile glioblastoma stem cell phenotype with a transcriptional profile of reduced migratory and MAPK pathway activity.

BackgroundType I interferons (IFN-α/β) are cytokines that are typically expressed in response to double-stranded RNA associated with viral infections. Glioblastomas are the most common malignant primary brain tumors, characterized by an infiltrative growth pattern and prominent angiogenic activity, and thought to be maintained by a subpopulation of glioma-initiating (stem-like) cells (GICs). The growth of human GIC lines is highly sensitive to IFN-β.MethodsRepetitive pulse stimulation with IFN-β1a (IS) was used to generate IS sublines that had acquired resistance to IFN-β-induced suppression of sphere formation. These cell lines were characterized by analyses of type 1 IFN signaling, growth patterns, and transcriptomic profiles.ResultsHere we report that repetitive IFN-β1a stimulation (IS) induces a stable phenotype (referred to as IS) at the level of maintaining sphere formation, although classical IFN signaling defined by the expression of both IFN receptors, myxovirus resistance protein A (MxA) accumulation, and STAT1 induction is unaffected. Furthermore, this stably altered IS phenotype is characterized by constitutively decreased sphere formation capacity and morphological features of senescence and autophagy. Transcriptional profiling reveals increased type I IFN signaling in these IS cells, but decreased expression of genes involved in receptor signaling and cell migration.ConclusionsAltogether, these data suggest a role for promoting IFN-β signaling in glioblastoma and might provide clues to design future therapeutic approaches.

FebriDx®: A Rapid Diagnostic Test for Differentiating Bacterial and Viral Aetiologies in Acute Respiratory Infections.

FebriDx® is a rapid, point-of-care diagnostic test that is designed to aid in the differentiation of bacterial and viral acute respiratory infections (ARIs), thus helping to guide decisions regarding the prescription of antibiotics in the outpatient setting. FebriDx carries a CE mark for use in the EU and is also approved in several other countries, including Canada, Saudi Arabia and Singapore. It is indicated for use in patients > 2 years old with symptoms consistent with a community-acquired ARI. The test involves the use of an immunoassay on a fingerstick blood sample to provide simultaneous, qualitative measurement of elevated levels of C-reactive protein (CRP) and myxovirus resistance protein A (MxA). In two prospective, multicentre studies in patients with acute upper respiratory tract infections, FebriDx was shown to be both sensitive and specific in identifying patients with a clinically significant infection and in differentiating between infections of bacterial and viral aetiology. The test is simple, requires no additional equipment and produces actionable results in ~ 10 min. As was demonstrated in a small, retrospective analysis, FebriDx results can help guide (improve) antibiotic prescribing decisions. Reducing the unnecessary or inappropriate prescription of antibiotics for ARIs of probable viral aetiology is important for antibiotic stewardship and can also reduce the unnecessary exposure of patients to the risk of antibiotic-related adverse events. FebriDx thus represents a useful diagnostic tool in the outpatient setting.

Human Antiviral Protein MxA Forms Novel Metastable Membraneless Cytoplasmic Condensates Exhibiting Rapid Reversible Tonicity-Driven Phase Transitions.

Phase-separated biomolecular condensates of proteins and nucleic acids form functional membrane-less organelles (e.g., stress granules and P-bodies) in the mammalian cell cytoplasm and nucleus. In contrast to the long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA) associated with the endoplasmic reticulum (ER) and Golgi apparatus, we report that MxA formed membraneless metastable (shape-changing) condensates in the cytoplasm. In our studies, we used the same cell lines and methods as those used by previous investigators but concluded that wild-type MxA formed variably sized spherical or irregular bodies, filaments, and even a reticulum distinct from that of ER/Golgi membranes. Moreover, in Huh7 cells, MxA structures associated with a novel cytoplasmic reticular meshwork of intermediate filaments. In live-cell assays, 1,6-hexanediol treatment led to rapid disassembly of green fluorescent protein (GFP)-MxA structures; FRAP revealed a relative stiffness with a mobile fraction of 0.24 ± 0.02 within condensates, consistent with a higher-order MxA network structure. Remarkably, in intact cells, GFP-MxA condensates reversibly disassembled/reassembled within minutes of sequential decrease/increase, respectively, in tonicity of extracellular medium, even in low-salt buffers adjusted only with sucrose. Condensates formed from IFN-α-induced endogenous MxA also displayed tonicity-driven disassembly/reassembly. In vesicular stomatitis virus (VSV)-infected Huh7 cells, the nucleocapsid (N) protein, which participates in forming phase-separated viral structures, associated with spherical GFP-MxA condensates in cells showing an antiviral effect. These observations prompt comparisons with the extensive literature on interactions between viruses and stress granules/P-bodies. Overall, the new data correct a long-standing misinterpretation in the MxA literature and provide evidence for membraneless MxA biomolecular condensates in the uninfected cell cytoplasm.IMPORTANCE There is a long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA), which displays antiviral activity against several RNA and DNA viruses, associates with the endoplasmic reticulum (ER) and Golgi apparatus. We provide data to correct this misinterpretation and further report that MxA forms membraneless metastable (shape-changing) condensates in the cytoplasm consisting of variably sized spherical or irregular bodies, filaments, and even a reticulum. Remarkably, MxA condensates showed the unique property of rapid (within 1 to 3 min) reversible disassembly and reassembly in intact cells exposed sequentially to hypotonic and isotonic conditions. Moreover, GFP-MxA condensates included the VSV nucleocapsid (N) protein, a protein previously shown to form liquid-like condensates. Since intracellular edema and ionic changes are hallmarks of cytopathic effects of a viral infection, the tonicity-driven regulation of MxA condensates may reflect a mechanism for modulation of MxA function during viral infection.

Perimysial microarteriopathy in dermatomyositis with anti-nuclear matrix protein-2 antibodies.

Dermatomyositis (DM) with anti-nuclear matrix protein-2 (NXP-2) antibodies usually shows multifocal ischaemic lesions in muscle. Here, we aimed to investigate the microarteriopathy underlying muscle ischaemia in anti-NXP-2-positive DM. A total of 16 patients diagnosed with anti-NXP-2-positive DM were investigated by muscle biopsy. A total of 13 patients with DM with other myositis-specific antibodies and 11 normal controls were included for comparison. Immunofluorescence assays were performed to localize endothelial cells, smooth muscle cells and pericytes, and to determine lesions in myofibers and microvessels by vascular endothelial growth factor and myxovirus resistance protein A (MxA). Electron microscopy was carried out to assess ultrastructure alterations. Subcutaneous edema, severe muscle weakness and dysphagia together with elevated creatine kinase, D-dimer and triglyceride levels, and decreased albumin levels were found in anti-NXP-2-positive DM. Muscle ischaemia included regional muscle edema, perifascicular atrophy, microinfarcts and focal punched-out vacuoles. The density of arterioles was higher in anti-NXP-2-positive DM (P＜0.05). Perimysial arterioles with thickened vascular wall, thrombosis and lipid accumulation were found in the vascular wall of diseased perimysial arterioles. The frequency of diseased arterioles and thrombosis was higher in anti-NXP-2-positive DM (P<0.05). Sarcoplasmic vascular endothelial growth factor and MxA expression was observed in multifocal ischaemic lesions. MxA was present in endothelial and smooth muscle cells of the diseased arterioles and pericytes. Electron microscopy confirmed damaged capillaries and tubuloreticular structures. Our research suggested that perimysial arterioles were most commonly involved in anti-NXP-2-positive DM, which led to muscle ischaemia.

409. Using the Host Response to Reduce Unnecessary Antibiotic Use in Outpatient Acute Respiratory Infections

BackgroundAcute respiratory tract infections (ARI) often resolve without antibiotics. Yet, antibiotics are prescribed in 60–98% of cases despite lack of confirmed bacterial etiology. Antigen, culture and molecular testing identify pathogens; however, do not differentiate colonization from invasive infection. Since antibiotics are often prescribed despite the low prevalence of confirmed bacterial infection in patients with ARI, we analyzed the impact of adding host response biomarkers to the clinical and microbiological evaluation of outpatients with ARI.MethodsA secondary analysis was performed using data from su suspected ARI cohorts derived from two clinical studies. A clinical reference algorithm, which included bacterial culture, respiratory PCR panels for viral and atypical pathogens, procalcitonin, CBC, serology, and Myxovirus resistance protein A (MxA), was used to define invasive infection based on pathogen detection plus host response and classify infections that may benefit from antibiotics. Antibiotics were considered “warranted” if patients exhibited a bacterial-specific host response, with or without bacterial pathogen detection, and a detected bacterial pathogen without a host response was deemed to be colonization and “at risk for antibiotics.” The percentage requiring antibiotics was calculated by dividing the number of patients with a host response for bacteria by the total number of patients at risk for receiving antibiotics (warranted + at risk). A Chi-square test was performed to determine the difference between patients likely to be treated with antibiotics, bacteria detected with or without host response and bacteria detected with a host response.ResultsEach dataset (Self, n = 205) and (Shapiro, n = 220) was analyzed separately and pooled (n = 445). Upon enrollment, 15% (Self) and 55% (Shapiro) were febrile. A pathogen was detected in 67% (Self) vs. 82% (Shapiro) subjects. Reduction in antibiotic prescription was calculated to be 35–44%, (P < 0.001–0.004), when host response was evaluated in addition to bacterial pathogen detection. Results presented in Table 1.ConclusionHost response may aid in differentiating viral infection and bacterial colonization from invasive bacterial infections requiring antibiotics. Disclosures All authors: No reported disclosures.

2023. A Prospective, Multi-Center U.S. Clinical Trial to Determine Accuracy of FebriDx Point-of-Care Testing for Acute Upper Respiratory Infections with and Without a Confirmed Fever

BackgroundFebriDx is a 10-minute disposable point-of-care test designed to identify clinically significant systemic host immune responses and aid in the differentiation of viral and bacterial respiratory infection by simultaneously detecting C-reactive protein (CRP) and myxovirus resistance protein A (MxA) from a fingerstick blood sample.MethodsA prospective, multicenter, cross-sectional study of primarily adults with acute upper respiratory tract infections (URIs), with and without a confirmed fever at the time of enrollment, was performed to evaluate the diagnostic accuracy of FebriDx to identify clinically significant bacterial infection with host response and acute pathogenic viral infection. URI was defined as rhinosinusitis, pharyngitis, nonspecific URI, and bronchitis and the reference method consisted of an algorithm that included throat bacterial cell culture, respiratory PCR panels for viral and atypical pathogens, procalcitonin, white blood cell count, and bandemia. The algorithm also utilized the Centor criteria and allowed for physician over-ride.ResultsAmong 220 patients enrolled, 100% reported fever ≥100.5 within the last 72 hours while 55% (121/220) had a confirmed fever at the time of enrollment. Of the total enrolled patients, 15% (34/220) were classified as bacterial, 56% (124/220) were classified as viral, and 28% (62/220) negative by the reference standard. Sample Size (n) Confirmation of Fever Diagnosis Sensitivit % and [95% CI] Specificity % and [95% CI] Positive Predictive Value (PPV)% and [95% CI] Negative Predictive Value (NPV)% and [95% CI] 220Reported within last3 daysBacterial 85 (29/34) [69-95] 93 (183/196) [89-96] 69 (29/42 ) [56-79] 97 (183/188) [94-99]Viral 90 (111/124) [83-94] 76 (73/96) [66-84] 83 (111/134) [77-87] 85 (73/86) [77-90]121Exhibited on enrollmentBacterial 95 (19/20) [77-100] 94 (95/101) [88-98] 76 (19/25) [59-87] 99 95/96) [93-100]Viral 90 (72/80) [81-96] 78 (32/41) [62-89] 89 (72/81) [82-93] 80 (32/40) [67-89]ConclusionWhen comparing clinical accuracy of diagnostic tests, performance values should be determined in febrile patients. FebriDx’s 97–99% NPV may help to identify clinically significant bacterial URI’s and supports outpatient antibiotic decisions.Disclosures R. Sambursky, Rapid Pathogen Screening, Inc.: Board Member, Employee and Shareholder, Salary.

Diagnostic potential of sarcoplasmic myxovirus resistance protein A expression in subsets of dermatomyositis

To elucidate the diagnostic value of sarcoplasmic expression of myxovirus resistance protein A (MxA) for dermatomyositis (DM) specifically analysing different DM subforms, and to test the superiority of MxA to other markers. Immunohistochemistry for MxA and retinoic acid-inducible gene I (RIG-I) was performed on skeletal muscle samples and compared with the item presence of perifascicular atrophy (PFA) in 57 DM patients with anti-Mi-2 (n=6), -transcription intermediary factor 1 gamma (n=10), -nuclear matrix protein 2 (n=13), -melanoma differentiation-associated gene 5 (MDA5) (n=10) or -small ubiquitin-like modifier activating enzyme (n=1) autoantibodies and with no detectable autoantibody (n=17). Among the patients, nine suffered from cancer and 22 were juvenile-onset type. Disease controls included antisynthetase syndrome (ASS)-associated myositis (n=30), immune-mediated necrotizing myopathy (n=9) and inclusion body myositis (n=5). Sarcoplasmic MxA expression featured 77% sensitivity and 100% specificity for overall DM patients, while RIG-I staining and PFA reached respectively 14% and 59% sensitivity and 100% and 86% specificity. In any subset of DM, sarcoplasmic MxA expression showed higher sensitivity than RIG-I and PFA. Some anti-MDA5 antibody-positive DM samples distinctively showed a scattered staining pattern of MxA. No ASS samples had sarcoplasmic MxA expression even though six patients had DM skin rash. Sarcoplasmic MxA expression is more sensitive than PFA and RIG-I expression for a pathological diagnosis of DM, regardless of the autoantibody-related subgroup. In light of its high sensitivity and specificity, it may be considered a pathological hallmark of DM per se. Also, lack of MxA expression in ASS supports the idea that ASS is a distinct entity from DM.

Destabilized adaptive influenza variants critical for innate immune system escape are potentiated by host chaperones.

The threat of viral pandemics demands a comprehensive understanding of evolution at the host–pathogen interface. Here, we show that the accessibility of adaptive mutations in influenza nucleoprotein at fever-like temperatures is mediated by host chaperones. Particularly noteworthy, we observe that the Pro283 nucleoprotein variant, which (1) is conserved across human influenza strains, (2) confers resistance to the Myxovirus resistance protein A (MxA) restriction factor, and (3) critically contributed to adaptation to humans in the 1918 pandemic influenza strain, is rendered unfit by heat shock factor 1 inhibition–mediated host chaperone depletion at febrile temperatures. This fitness loss is due to biophysical defects that chaperones are unavailable to address when heat shock factor 1 is inhibited. Thus, influenza subverts host chaperones to uncouple the biophysically deleterious consequences of viral protein variants from the benefits of immune escape. In summary, host proteostasis plays a central role in shaping influenza adaptation, with implications for the evolution of other viruses, for viral host switching, and for antiviral drug development.

Neutralizing antibody production against Rebif® and ReciGen® in Relapsing-Remitting Multiple Sclerosis (RRMS) patients and its association with patient's disability

IntroductionHuman recombinant interferon beta (IFN-β) is one of the first line treatments for Relapsing-Remitting Multiple Sclerosis (RRMS). However, the production of neutralizing antibodies (NAb) can impair its function. The aim of this study was to investigate the production of neutralizing antibodies against Rebif® and ReciGen® (two brands of IFN-β-1a) and to evaluate its correlation with Expanded Disability Status Scale (EDSS). Materials and methodsSerum samples of 71 RRMS patients (34 in ReciGen®, 37 in Rebif® group) were collected. Neutralizing antibody was measured by Myxo-virus resistance protein A (MxA) assay using A549 cell line. The MxA concentration was measured by enzyme-linked immunosorbent assay (ELISA) kit. ResultsThe median period of treatment with IFN-β-1a was 18 months in ReciGen® and 24 months in Rebif® arms. The percentage of patients with positive titer of neutralizing antibody (NAb+) had no statistically significant difference between groups (P = 0.6). In both ReciGen® and Rebif® groups, the increase in EDSS score was significantly higher in NAb+ patients compared to NAb− patients (p ≤ 0.05). The duration of using ReciGen® or Rebif® for >24 months was influential in the NAb positivity (OR = 3.78). ConclusionReceiving interferon beta-1a for >24 months is correlated with higher possibility of NAb production. The type of IFN-β used in the study had no significant impact on NAb positivity. In addition, both groups had comparable EDSS score changes, and NAb status of patients was correlated with their EDSS score.

Expression of myxovirus-resistance protein A: a possible marker of muscle disease activity and autoantibody specificities in juvenile dermatomyositis.

AimsTo evaluate the relationship between expression of myxovirus‐resistance protein A (MxA) protein on muscle biopsies by immunohistochemistry and disease activity in juvenile dermatomyositis (JDM) patients. Also, another aim was to investigate whether the expression of MxA is related with myositis‐specific autoantibodies (MSA) status in JDM patients.Methods103 patients (median aged 6.3, interquartile range 0.5–15.9) enrolled in the Juvenile Dermatomyositis Cohort and Biomarker Study (JDCBS). Muscle biopsies were stained with MxA and scored. Clinical data at initial presentation were collected and autoantibodies were analysed. Multiple linear regression analysis was performed to estimate the association between MxA expression on muscle fibres and muscle disease activity, and MSA status.ResultsExpression of MxA protein on JDM samples was identified in 61.2%. There was a significant association between MxA scores and Childhood Myositis Assessment Scale (CMAS) (P = 0.002), and Manual Muscle Testing of Eight Muscles (MMT8) (P = 0.026). CMAS and MMT8 scores were significantly lower in the group of patients with strong MxA expression. MxA scores differed according to MSA subgroups (P = 0.002). Patients with positive nuclear matrix protein 2 autoantibodies had strong MxA expression, whereas anti‐melanoma differentiation‐associated gene 5 positive patients had no or weak MxA expression.ConclusionsThis study reveals the significant association between level of MxA expression on muscle fibres and clinical measures of muscular disease activity in JDM patients and MSA status. This confirms type I interferonopathies in muscle fibres of JDM patients which could help with improving treatment outcome in JDM patients and underscoring the distinct pathophysiological pathways in different MSA status.

A prospective, multi-centre US clinical trial to determine accuracy of FebriDx point-of-care testing for acute upper respiratory infections with and without a confirmed fever

Background: FebriDx is a 10-minute disposable point-of-care test designed to identify clinically significant systemic host immune responses and aid in the differentiation of bacterial and viral respiratory infection by simultaneously detecting C-reactive protein (CRP) and myxovirus resistance protein A (MxA) from a fingerstick blood sample. FebriDx diagnostic accuracy was evaluated in the emergency room and urgent care setting.Methods: A prospective, multicentre, observational cohort study of acute upper respiratory tract infections (URIs), with and without a confirmed fever at the time of enrolment, was performed to evaluate the diagnostic accuracy of FebriDx to identify clinically significant bacterial infection with host response and acute pathogenic viral infection. The reference method consisted of an algorithm with physician override that included bacterial cell culture, respiratory PCR panels for viral and atypical pathogens, procalcitonin, and white blood cell count.Results: Among 220 patients enrolled, 100% reported fever 100.5°F within the last 72 hours while 55% had a measured hyperthermia (T > 100.4) at the time of enrolment. FebriDx demonstrated a sensitivity of 95% (95% CI: 77–100%), specificity of 94% (88–98%), PPV of 76% (59–87%), and a NPV of 99% (93–100%).Conclusion: FebriDx may identify clinically significant bacterial URI’s and supports outpatient antibiotic decisions.Key messagesFebriDx is an outpatient POC test designed to identify a clinically significant systemic host immune response and aid in the differentiation of viral and bacterial infection through rapid measurement of MxA and CRP from a fingerstick blood sample. FebriDx test was determined to be an accurate test, with a 85% sensitivity, 93% specificity and 97% NPV to rule out bacterial infection for any patient presenting with symptoms and reported fever within the prior 3 days, and when confirming fever (hyperthermia) at the time of testing, the test was even more sensitive (95%) and specific (94%) with a 99% NPV. FebriDx may support antibiotic stewardship by rapidly identifying clinically significant bacterial URIs.

Myxovirus resistance protein A inhibits hepatitis C virus replication through JAK-STAT pathway activation.

The interferon-inducible dynamin-like GTPase myxovirus resistance protein A (MxA) exhibits activity against multiple viruses. However, its role in the life cycle of hepatitis C virus (HCV) is unclear, and the mechanisms underlying the anti-HCV activity of MxA require further investigation. In this study, we demonstrated that exogenous MxA expression in the Huh7 and Huh7.5.1 hepatoma cell lines significantly decreased the levels of HCV RNA and core proteins, whereas MxA knockdown exerted the opposite effect. MxA-mediated inhibition of HCV replication was found to involve the JAK-STAT pathway: STAT1 phosphorylation and the expression of IFN-stimulated genes (ISGs) such as guanylate-binding protein 1 and 2'-5'-oligoadenylate synthetase 1 were augmented by MxA overexpression and reduced by endogenous MxA silencing. Treatment with the JAK inhibitor ruxolitinib abrogated the MxA-mediated suppression of HCV replication and activation of the JAK-STAT pathway. Additionally, transfection with an MxA mutant with disrupted GTP-binding consensus motifs abrogated activation of the JAK-STAT pathway and resistance to HCV replication. This study shows that MxA inhibits HCV replication by activating the JAK-STAT signaling pathway through a mechanism involving its GTPase function.

Outpatient Antibiotic Stewardship: A Growing Frontier-Combining Myxovirus Resistance Protein A With Other Biomarkers to Improve Antibiotic Use.

BackgroundThe majority of oral antibiotics are prescribed in outpatient primary and urgent care clinics for acute respiratory infections. Effective antibiotic stewardship must include proper prescribing for outpatients as well as for those in a hospital or long-term care facility. MethodsMajor databases, including MEDLINE and the Cochrane Library, were searched for prospective human clinical studies, including children and/or adults published between January 1966 and November 2017 that evaluated Myxovirus resistance protein A (MxA) as a biomarker for diagnosing viral infections as well as both C-reactive protein (CRP) and procalcitonin (PCT) as potential biomarkers for identifying and differentiating true bacterial upper respiratory infection (URI) from colonization.ResultsTen prospective human studies, totaling 1683 patients, were identified that evaluated MxA as a viral biomarker in children and/or adults. Both systematic review articles, meta-analyses, and randomized controlled clinical trials that examined CRP and/or PCT as a biomarker for identifying clinically significant bacterial infections and supporting antibiotic stewardship were identified.ConclusionsQuick and accurate differentiation between a viral and bacterial respiratory infection is critical to effectively combat antibiotic misuse. MxA expression in peripheral blood is a highly specific marker for viral infection. Combining MxA with other inflammatory biomarkers to test for respiratory infections offers enhanced sensitivity and specificity, forming an excellent tool for antibiotic stewardship in the outpatient setting.

Prevalence of neutralising antibodies to interferon-beta and clinical response in Chinese patients with relapsing multiple sclerosis.

BackgroundThere are no data on neutralising antibodies to interferon-beta and its clinical implications in Chinese patients with multiple sclerosis (MS).ObjectivesThe objectives of this study were to investigate the prevalence of neutralising antibodies among Chinese patients with relapsing MS receiving interferon-beta (1a or 1b) and to study the association between neutralising antibodies and the clinical-radiological response.MethodsWe performed a cross-sectional study on MS patients who received interferon-beta for 9 months or more, and evaluated the clinical response by relapses and magnetic resonance imaging lesions. Blood samples were evaluated for myxovirus resistance protein A (MxA) gene expression by polymerase chain reaction, anti-interferon-beta binding antibodies by enzyme-linked immunosorbent assay, and neutralising antibodies by cell-based MxA protein induction and luciferase reporter gene assays. Assay performances were evaluated by receiver operating characteristic analysis.ResultsAmong 78 subjects recruited, 61/77 (79%) had anti-interferon-beta binding antibodies, and 22/78 (28%) had neutralising antibodies by MxA protein induction assay. The presence of high-titre neutralising antibodies was associated with poor clinical outcome (odds ratio 6.1, 95% confidence interval 1.5–25.6, P = 0.013). The sensitivity and specificity for neutralising antibodies using MxA gene expression assay (cut-off 0.20) was 80% and 68%, respectively (area under the curve 0.71).ConclusionsNeutralising antibodies are associated with poor clinical outcome in Chinese patients with relapsing MS. MxA gene expression and protein induction assays are complimentary assays for neutralising antibody detection.

Diagnostic Accuracy of FebriDx: A Rapid Test to Detect Immune Responses to Viral and Bacterial Upper Respiratory Infections.

C-reactive protein (CRP) and myxovirus resistance protein A (MxA) are associated with bacterial and viral infections, respectively. We conducted a prospective, multicenter, cross-sectional study of adults and children with febrile upper respiratory tract infections (URIs) to evaluate the diagnostic accuracy of a rapid CRP/MxA immunoassay to identify clinically significant bacterial infection with host response and acute pathogenic viral infection. The reference standard for classifying URI etiology was an algorithm that included throat bacterial culture, upper respiratory PCR for viral and atypical pathogens, procalcitonin, white blood cell count, and bandemia. The algorithm also allowed for physician override. Among 205 patients, 25 (12.2%) were classified as bacterial, 53 (25.9%) as viral, and 127 (62.0%) negative by the reference standard. For bacterial detection, agreement between FebriDx and the reference standard was 91.7%, with FebriDx having a sensitivity of 80% (95% CI: 59–93%), specificity of 93% (89–97%), positive predictive value (PPV) of 63% (45–79%), and a negative predictive value (NPV) of 97% (94–99%). For viral detection, agreement was 84%, with a sensitivity of 87% (75–95%), specificity of 83% (76–89%), PPV of 64% (63–75%), and NPV of 95% (90–98%). FebriDx may help to identify clinically significant immune responses associated with bacterial and viral URIs that are more likely to require clinical management or therapeutic intervention, and has potential to assist with antibiotic stewardship.

Detection of Host Response to Viral Respiratory Infection by Measurement of Messenger RNA for MxA, TRIM21, and Viperin in Nasal Swabs.

Respiratory viruses frequently cause symptomatic infections in children but are often detected also in healthy children. We investigated myxovirus resistance protein A (MxA), viperin, and tripartite-motif 21 (TRIM21) messenger RNA indexes in nasal swabs as potential biomarkers of viral respiratory infection in children. Respiratory viruses were detected by polymerase chain reaction in the same swabs. Nasal MxA and viperin indexes were increased in symptomatic virus-positive children. Nasal viperin index was found to be a robust marker of viral respiratory tract infection with a sensitivity of 80% and specificity of 94% in distinguishing children with symptomatic virus infections from asymptomatic virus-negative children.

Autocrine activation of the IFN signaling pathway may promote immune escape in glioblastoma.

Interferons (IFNs) are cytokines typically induced upon viral infection but are constitutively expressed also in the absence of acute infection. The physiological role of autocrine and paracrine IFN signaling, however, remains poorly understood, and its function in glioblastoma has not been explored in depth. Using RNA interference-mediated gene silencing, we characterized constitutive type I IFN signaling and its role in human glioma cells. We observed constitutive expression of phosphorylated signal transducer and activator of transcription 1 (pSTAT1) and myxovirus resistance protein A (MxA), a classical IFN-response marker, in the absence of exogenous IFN-β. In vivo, we found higher MxA expression in gliomas than in normal tissue, suggesting that IFN signaling is constitutively active in these tumors. To demonstrate the presence of an autocrine type I IFN signaling loop in glioma cells in vitro, we first confirmed the expression of the type I alpha/beta receptor (IFNAR)1/2, and its ligands, IFN-α and IFN-β. Small interfering RNA-mediated receptor gene silencing resulted in reduced expression of MxA at mRNA and protein levels, as did gene silencing of the ligands, corroborating the hypothesis of an autocrine signaling loop in which type I IFNs induce intracellular signaling through IFNAR1/2. On a functional level, following IFNAR1 or IFNAR2 gene silencing, we observed reduced programmed death ligand 1 (PD-L1) and major histocompatibility complex (MHC) class I and II expression as well as an enhanced susceptibility to natural killer immune cell lysis, suggesting that autocrine IFN signaling contributes to the immune evasion of glioma cells. Our findings point to an important role of constitutive IFN signaling in glioma cells by modulating their interaction with the microenvironment.