Myxovirus Resistance Protein A Protein Research Articles

Expression of MxA in esophageal cancer cell lines can influence sensitivity to chemotherapeutic agents but this does not require apoptosis.

Esophageal cancer is a poor prognosis cancer characterized by intrinsic or acquired resistance to chemotherapeutic agents. The primary determinants of treatment failure are unknown. Expression of an anti-viral protein, myxovirus resistance protein A (MxA) is de-regulated in many cancers, including esophageal cancer, and its activity has been linked to apoptosis. This study has assessed whether MxA expression can influence the response of esophageal cancer cells to the chemotherapeutic agents 5-fluorouracil (5-FU) or oxaliplatin. MxA protein was differentially expressed in a panel of five esophageal cancer cell lines. KYSE450 and KYSE140 cells did not express MxA and were apoptosis incompetent. FLO-1, KYSE270, and OE21 cells expressed MxA, were more drug-sensitive and were apoptosis competent. MxA was artificially overexpressed in cell lines with no endogenous expression (KYSE450 and KYSE140). This increased the resistance of KYSE450 but not KYSE140 cells. Both cell lines remained apoptosis incompetent. We then evaluated siRNA knockdown of MxA in FLO-1 cells and CRISPR knockout in OE21 cells. Knockdown of MxA significantly increased drug sensitivity and caspase-3 activation in FLO-1 cells. OE21-MX1KO cells were also more drug-sensitive, but in contrast to FLO-1 cells, caspase-3 activation was reduced. Collectively these data indicate that MxA can promote resistance to chemotherapy, but this does not always correspond with effects on apoptosis. Effects on apoptosis are cell line specific, suggesting that other co-operating pathways determine the overall impact of MxA. Importantly, in cancer cells that overexpress the protein, drug sensitivity can be improved by interfering with MxA.

Rational design of MIPs for the detection of Myxovirus resistance protein A (MxA), a biomarker for viral infection

Accurate diagnosis is crucial for effective patient care and the containment of antimicrobial resistance outbreaks. The intricate challenge of distinguishing bacterial from viral infections, coupled with limited diagnostic tools and overlapping symptoms has driven the utilization of molecular imprinting techniques. This study focuses on developing cost-effective, chemically stable antibody analogs for the interferon-induced protein myxovirus resistance protein A (MxA). MxA is an intracellular, cytoplasmic GTPase having activity against a wide range of viruses and serves as a distinctive biomarker for viral infections. We utilized computational design to guide the polymer assembly, centering on epitope imprinting to target MxA-specific regions crucial for interaction. Molecular docking calculations, alongside a pioneering multi-monomer simultaneous docking (MMSD) protocol, efficiently elucidate cooperativity during pre-polymerization. Monomer binding affinity scores, such as for APTMS, exhibited notable increase, ranging from −3.11 to −13.03 kcal/mol across various MMSD combinations compared to a maximum of −2.78 kcal/mol in single monomer docking, highlighting the capacity of MMSD in elucidating crucial monomer-monomer interactions. This computational approach provides a theoretical alternative to labor-intensive experimental optimization, streamlining the development process for synthetic receptors. Simulations reveal unique interactions enhancing MIP-peptide complementarity, yielding optimized receptors selectively binding to MxA epitopes. The obtained MIPs demonstrated a maximum adsorption capacity of approximately 12 mg/g and captured 1.6 times more epitope and 2.6 times more epitope containing MxA protein than corresponding NIPs. A proof-of-concept study demonstrates MxA protein binding to synthetic receptors, highlighting the potential of MIPs, analogous to antibodies, in overcoming current diagnostic challenges for precise detection of viral infection.

Sarcoplasmic Myxovirus Resistance Protein A: A Study of Expression in Idiopathic Inflammatory Myopathy.

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune diseases affecting primarily proximal muscles. Major subtypes include dermatomyositis, polymyositis, inclusion body myositis, immune-mediated necrotizing myopathy and antisynthetase syndrome. Overexpression of sarcoplasmic myxovirus-resistance protein A (MxA) has been observed in muscle biopsy specimens of dermatomyositis but is rarely seen in other subtypes of IIM and other myopathies. We evaluate the expression of sarcoplasmic MxA and its diagnostic value in IIM and other myopathies. One hundred and thirty-eight muscle biopsy specimens with the diagnosis of IIM and other myopathies from 2011 to 2020 were reviewed and stained for MxA by immunohistochemistry. The difference of the expression of MxA between IIM and other myopathies was analyzed by Fisher's exact test, and the sensitivity and specificity of MxA immunohistochemistry in the diagnosis of IIM were assessed. MxA protein was positive in 16/138 (11.6%) specimens. All 12 dermatomyositis specimens positive for MxA protein were positive in perifascicular area pattern. Only dermatomyositis specimens had a significantly higher percentage of positive sarcoplasmic MxA expression than specimens of other subtypes of IIM (p<0.001). Sarcoplasmic MxA expression for dermatomyositis diagnosis had a sensitivity of 46.15% (95% CI 26.59-66.63%) and a specificity of 94.44% (95% CI 81.34-99.32%) with the positive and negative likelihood ratio of 8.31 (95% CI 2.03-34.01) and 0.57 (95% CI 0.40-0.82), respectively. The MxA immunohistochemistry is highly specific for dermatomyositis and should be added to a routine inflammatory panel of muscle biopsy. MxA expression should be cautiously interpreted to avoid pitfalls.

MxA Protein Expression and Histological Characteristics on Muscle Biopsy in Myositis (P9-8.001)

<h3>Objective:</h3> To evaluate both myofiber and capillary MxA expression in a wide range of potentially type 1 interferon driven myositis. <h3>Background:</h3> The myxovirus resistance protein A (MxA) is one of the most highly induced protein by type I interferons. The current international neuromuscular workshop recognizes MxA reactivity on myofibers as a definitive marker for dermatomyositis, with 98–100% specificity on muscle biopsies. However, many type I interferon driven inflammatory myositis have not been tested in previous studies. <h3>Design/Methods:</h3> We evaluated both myofiber and capillary MxA expression in a wide range of potentially type 1 interferon driven myositis, including lupus myositis, HIV myositis, Sjogren’s disease associated myositis, systemic sclerosis associated myositis and antisynthetase syndrome associated myositis. Dermatomyositis and immune mediated necrotizing myopathy served as positive and negative control, respectively. We also cross compared the presence of endothelial tubuloreticular inclusions (TRI), another type 1 interferon activation marker, with MxA expressions. <h3>Results:</h3> Myofiber MxA expression was present in 78.9% (15/19) of active lupus myositis but was uncommon in active myositis associated with HIV (1/18), Sjogren’s disease (1/12), systemic sclerosis (2/14), and antisynthetase syndrome (2/11). Capillary MxA expression was much more prevalent and less specific, present in lupus (18/19), HIV (8/18), Sjogren’s disease (9/12), systemic sclerosis (11/14), and antisynthetase syndrome (9/11). There was a positive correlation between myofiber MxA expression and presence of endothelial tubuloreticular inclusions. Histologically, lupus myositis was characterized by a “pan-fascicular” necrotizing myopathy pattern. <h3>Conclusions:</h3> MxA myofiber expression is not a specific marker for dermatomyositis. Nevertheless, MxA is still a highly useful tool in muscle biopsy whose myofiber expression is strongly suggestive of either dermatomyositis or lupus myositis. The “pan-fascicular” necrotizing myopathy pattern in lupus myositis may serve as a useful histological feature to differentiate from the “perifascicular” injury pattern in dermatomyositis. <b>Disclosure:</b> Dr. Trivedi has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. The institution of Dr. Trivedi has received research support from NIH. Dr. Xing has nothing to disclose. Nicole Bitencourt has nothing to disclose. Chunyu Cai has nothing to disclose.

Myxovirus resistance protein A for discriminating between viral and bacterial lower respiratory tract infections in children – The TREND study

ObjectiveDiscriminating between viral and bacterial lower respiratory tract infection (LRTI) in children is challenging, leading to an excessive use of antibiotics. Myxovirus resistance protein A (MxA) is a promising biomarker for viral infections. The primary aim of the study was to assess differences in blood MxA levels between children with viral and bacterial LRTI. Secondary aims were to assess differences in blood MxA levels between children with viral LRTI and asymptomatic controls and to assess MxA levels in relation to different respiratory viruses. MethodsChildren with LRTI were enrolled as cases at Sachs' Children and Youth Hospital, Stockholm, Sweden. Nasopharyngeal aspirates and blood samples for analysis of viral PCR, MxA, and C-reactive protein were systematically collected from all study subjects in addition to standard laboratory/radiology assessment. Aetiology was defined according to an algorithm based on laboratory and radiological findings. Asymptomatic children with minor surgical disease were enrolled as controls. ResultsMxA levels were higher in children with viral LRTI (n = 242) as compared to both bacterial (n = 5) LRTI (p <0.01, area under the curve (AUC) 0.90, 95% CI: 0.81 to 0.99), and controls (AUC 0.92, 95% CI: 0.88 to 0.95). In the subgroup of children with pneumonia diagnosis, a cutoff of MxA 430 μg/l discriminated between viral (n = 29) and bacterial (n = 4) aetiology with 93% (95% CI: 78–99%) sensitivity and 100% (95% CI: 51–100%) specificity (AUC 0.98, 95% CI: 0.94 to 1.00). The highest MxA levels were seen in cases PCR positive for influenza (median MxA 1699 μg/l, interquartile range: 732 to 2996) and respiratory syncytial virus (median MxA 1115 μg/l, interquartile range: 679 to 2489). DiscussionMxA accurately discriminated between viral and bacterial aetiology in children with LRTI, particularly in the group of children with pneumonia diagnosis, but the number of children with bacterial LRTI was low.

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&lt;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&lt;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.

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.

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.

ID: 187: Allelic variations in the interferon-induced human MxA protein affect its antiviral activity against influenza A virus

Human myxovirus resistance protein A (MxA) is an interferon-induced GTPase and part of the host cell defense against influenza viruses. It has a three-domain architecture with an amino-terminal GTPase (G) domain and a carboxy-terminal stalk responsible for oligomerization and viral target recognition. The MX1 gene, encoding MxA, is highly conserved and only a few single nucleotide polymorphisms are described in the human population. In this study we investigate whether and how allelic variations in MxA influence its antiviral function. Two rare nucleotide changes identified in the MX1 gene of healthy individuals result in amino acid exchanges at positions 255 and 268 in the G domain. GTPase and Minireplicon assays revealed that the V268M exchange showed some reduction in GTP hydrolysis, but only a slightly reduced antiviral activity against influenza A virus. However, the G255E exchange caused a complete loss of GTPase and antiviral activity of MxA. Further biochemical analyses of this naturally occurring mutation revealed the central role of GTP binding and hydrolysis for the antiviral mechanism of MxA. Using bioinformatics tools we are currently identifying additional allelic variations in MxA. Their characterization will answer the question how polymorphisms in the MX1 gene influence the antiviral capacity of MxA and whether these are enriched in patients suffering from severe influenza as has been described recently for IFITM3, another interferon-induced antiviral restriction factor.

Use of a Standardized MxA Protein Measurement-Based Assay for Validation of Assays for the Assessment of Neutralizing Antibodies Against Interferon-β

Effective monitoring of the development of neutralizing antibodies (NAbs) against IFN-β in multiple sclerosis (MS) patients on IFN-β therapy is important for clinical decision making and disease management. To date, antiviral assays have been the favored approach for NAb determination, but variations in assay conditions between laboratories and the increasing use of novel assays have contributed to the reporting of inconsistent antibody data between laboratories and between products. This study, undertaken at the request of the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA), is a joint effort by manufacturers of IFN-β products (approved in Europe) towards harmonization of a NAb assay that facilitates generation of comparable NAb data, which, in conjunction with clinical outcomes, should prove useful for clinicians treating MS patients with IFN-β products. This article describes the standardized cellular myxovirus resistance protein A (MxA) protein measurement-based assay for detection of IFN-β NAbs and its use for the validation of assays used for the quantitative determination of such antibodies. Although titers varied between laboratories and the products used, utilization of IFN-β1a rather than IFN-β1b as the challenge antigen produced more consistent results in the NAb assay. Adoption of the standardized assay improves comparability between laboratories circumventing problems that arise when different, nonstandardized assays are employed for immunogenicity assessment. Based on the data, the EMA recommended for standardization purposes, the use of IFN-β1a in NAb assays, independent of the therapeutic product used for therapy and validation of new NAb procedures against the standardized assay described.

MxA as a clinically applicable biomarker for identifying systemic interferon type I in primary Sjögren's syndrome

ObjectiveTo establish an easy and practical assay for identifying systemic interferon (IFN) type I bioactivity in patients with primary Sjögren's syndrome (pSS). The IFN type I signature is present in...

Inhibition of interferon-α-induced signaling by hyperosmolarity and hydrophobic bile acids

Apart from viral conditions, host factors such as elevated bile acid concentrations are determinants of successful interferon-α (IFN-α) treatment in patients with chronic hepatitis C or B. The present study demonstrates that hydrophobic bile acids inhibit Jak1- and Tyk2-phosphorylation, which lead to blockade of STAT1-mediated IFN-α-signaling in the sodium-taurocholate cotransporting peptide (NTCP)-transfected human hepatoma cell line HepG2, resulting in a decreased mRNA and protein expression of IFN-stimulated genes such as myxovirus resistance protein A (MxA) or dsRNA-activated protein kinase (PKR). In addition, hyperosmotic stress leads to an inhibition of IFN-α-induced Jak1- and Tyk2-phosphorylation, and STAT1/STAT2-phosphorylation and gene expression. This inhibitory effect of hydrophobic bile acids or hyperosmolarity is not due to caspase-mediated cleavage or lysosomal degradation of the cognate receptors or to the generation of oxidative stress, activation of p38- or Erk-mediated MAPK pathways or phosphatase activity. Preincubation with the organic osmolyte betaine blocked the inhibitory effect of bile acids or hyperosmolarity on MxA protein expression, but had no effect on transcript levels or activation of STAT1, suggesting that betaine mediates its effects on MxA expression at a translational or post-translational level. Our findings could provide a rationale for betaine use in cholestatic HBV/HCV patients undergoing interferon therapy.

A Monoclonal Antibody Specific to Human Myxovirus Resistance Protein A

Recombinant human myxovirus resistance protein A (MxA) was successfully expressed by an Escherichia coli expression system. After immunization and cell fusion, a mouse hybridoma (3C2) producing MAbs to MxA was established. Hybridoma 3C2 was further characterized using indirect ELISA, Western blot analysis, immunofluorescent staining, and immunoprecipitation. The ELISA results showed that the titer of 3C2 was between 1:6400 and 1:12800 in ascitic fluids. The isotype of the monoclonal antibody was tested to be IgG1kappa. 3C2 can also specifically recognize human MxA protein in various formats by Western blot analysis, immunofluorescent staining, and immunoprecipitation assay. We further demonstrated that 3C2 could be used to detected MxA expression induce by type I interferon in A549 cell line and human peripheral blood mononuclear cells by Western blot in a dose-dependent manner.

Herpes Simplex Virus Type 1 Us3 Gene Deletion Influences Toll-like Receptor Responses in Cultured Monocytic Cells

BackgroundToll-like receptors have a key role in innate immune response to microbial infection. The toll-like receptor (TLR) family consists of ten identified human TLRs, of which TLR2 and TLR9 have been shown to initiate innate responses to herpes simplex virus type 1 (HSV-1) and TLR3 has been shown to be involved in defence against severe HSV-1 infections of the central nervous system. However, no significant activation of the TLR3 pathways has been observed in wild type HSV-1 infections. In this work, we have studied the TLR responses and effects on TLR gene expression by HSV-1 with Us3 and ICP4 gene deletions, which also subject infected cells to apoptosis in human monocytic (U937) cell cultures.ResultsU937 human monocytic cells were infected with the Us3 and ICP4 deletion herpes simplex virus (d120), its parental virus HSV-1 (KOS), the Us3 deletion virus (R7041), its rescue virus (R7306) or wild type HSV-1 (F). The mRNA expression of TLR2, TLR3, TLR4, TLR9 and type I interferons (IFN) were analyzed by quantitative real-time PCR. The intracellular expression of TLR3 and type I IFN inducible myxovirus resistance protein A (MxA) protein as well as the level of apoptosis were analyzed by flow cytometry. We observed that the mRNA expression of TLR3 and type I IFNs were significantly increased in d120, R7041 and HSV-1 (F)-infected U937 cells. Moreover, the intracellular expression of TLR3 and MxA were significantly increased in d120 and R7041-infected cells. We observed activation of IRF-3 in infections with d120 and R7041. The TLR4 mRNA expression level was significantly decreased in d120 and R7041-infected cells but increased in HSV-1 (KOS)-infected cells in comparison with uninfected cells. No significant difference in TLR2 or TLR9 mRNA expression levels was seen. Both the R7041 and d120 viruses were able to induce apoptosis in U937 cell cultures.ConclusionThe levels of TLR3 and type I IFN mRNA were increased in d120, R7041 and HSV-1 (F)-infected cells when compared with uninfected cells. Also IRF-3 was activated in cells infected with the Us3 gene deletion viruses d120 and R7041. This is consistent with activation of TLR3 signaling in the cells. The intracellular TLR3 and type I IFN inducible MxA protein levels were increased in d120 and R7041-infected cells but not in cells infected with the corresponding parental or rescue viruses, suggesting that the HSV-1 Us3 gene is involved in control of TLR3 responses in U937 cells.

MxA protein – an interferon beta biomarker in primary progressive multiple sclerosis patients

Interferon beta (IFNbeta) preparations have some effect on the progressive phase of multiple sclerosis (MS). This limited effect might be partially because of a certain number of IFNbeta non-responders. Myxovirus resistance protein A (MxA)--a marker of IFNbeta bioactivity--was correlated with the clinical response during an uncontrolled trial, investigating the safety of IFNbeta-1b in primary progressive (PPMS) patients. Twenty PPMS were treated with IFNbeta-1b (s.c.) for 1 year. Blood samples were taken before and 1, 2, 3, 6, 9, 12, and 15 months after treatment initiation and MxA protein levels were measured. Patients were clinically evaluated by EDSS and the more sensitive Incapacity Status Scale (ISS) and stratified in a stable and a progressing group. Using ISS criteria, 11 patients remained stable and nine patients progressed during treatment. The mean area under the curve of log MxA levels during treatment were significantly higher in stable than in progressing patients (10.87 vs. 5.99; P = 0.002). A good biological response to IFNbeta might be associated with a better clinical effect of this drug and could be helpful in future clinical studies for early identification of treatment responders.

MxA protein assay for optimal monitoring of IFN-β bioactivity in the treatment of MS patients

Myxovirus resistance protein A (MxA) can be used as a marker of the bioactivity of interferon-beta (IFN-beta) therapy. Two to forty per cent of IFN-beta-treated multiple sclerosis (MS) patients develop IFN-beta-neutralizing antibodies (NAb) with subsequent attenuation of MxA protein induction. The aim of this study was to set up a simple MxA enzyme immunoassay (EIA) for the measurement of MxA protein and to evaluate the EIA test by comparing the results with flow cytometric analysis and the measurement of NAb. total of 51 IFN-beta-treated relapsing-remitting MS (RRMS) patients were tested for MxA protein expression by using both MxA EIA assay and flow cytometric analysis. Thirteen patients were confirmed to be NAb-positive. The correlation between EIA and flow cytometric analysis was significant with a wider range of measured levels in the EIA. Patients with NAb had low MxA levels, but in some patients, remaining MxA induction could be detected despite NAb. The MxA EIA assay seems to be a practical method for large-scale analysis of the bioactivity of IFN-beta treatment.

Type I interferon-associated skin recruitment of CXCR3+ lymphocytes in dermatomyositis

Dermatomyositis (DM) is an autoimmune disease of unknown origin affecting skin and muscles. Infiltrating autoreactive T lymphocytes are thought to play an important pathogenetic role, but it is unclear which mechanisms are involved in the recruitment of these cells. Recent studies provided evidence that a type I interferon (IFN)-driven immune response, including the recruitment of T cells via IP10/CXCR3 interactions, might be important for the generation of skin lesions of cutaneous lupus erythematosus (CLE), an autoimmune disease that shares some clinical and histopathological features with DM. We hypothesized that a similar mechanism might also be involved in the pathogenesis of DM skin lesions. Skin biopsies of 23 donors (11 DM, 5 healthy controls, 7 CLE controls) were analysed by immunohistochemistry using monoclonal antibodies against CD3, CD4, CD8, CD20, CD68, CD123, the chemokine receptor CXCR3 and its ligand IP10/CXCL10, and the myxovirus-resistance protein A (MxA)-protein, which is a specific marker for type I IFNs. We detected strong expression of the MxA protein in all DM skin biopsies, indicating involvement of type I IFNs. Expression of MxA was closely associated with expression of the interferon-inducible protein IP10/CXCL10 and the recruitment of CXCR3+ lymphocytes. Plasmacytoid dendritic cells appear to be an important source of type I IFNs in DM. Our results support the hypothesis that lesional type I IFN signalling, induction of IP10 expression, and recruitment of potentially autoreactive T cells via IP10/CXCR3 interaction are involved in the pathogenesis of DM skin lesions.