Myxovirus Resistance Protein A Research Articles

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.

Upregulation of Myxovirus-resistance Protein A: A Possible Marker of Type I Interferon Induction in Systemic Sclerosis

.To examine whether myxovirus-resistance protein A (MxA) mRNA expression, commonly considered a reliable marker of Type I interferon (IFN) bioactivity, is modified in patients with systemic sclerosis (SSc); if it is associated to specific clinical features; and if its modulation is accompanied by modulation of mRNA for the Type I IFN receptor (IFNAR). Quantification of mRNA for MxA and the subunit IFNAR1 and isoforms of IFNAR2 was performed by real-time polymerase chain reaction in 50 patients with SSc. Results were compared with those obtained from healthy controls and patients with another autoimmune disease such as multiple sclerosis. . Levels of MxA mRNA above the 99th percentile of values found in healthy controls were observed in 9 out of 50 patients with SSc (p < 0.001). Induced MxA expression was significantly associated with some features of more severe disease, such as lower forced vital capacity and the presence of ischemic digital ulcers. No differences in the levels of IFNAR were found within MxA-induced and MxA-non-induced patients, but there was a direct correlation between levels of MxA and the soluble isoform of IFNAR2. . Our results show induction of MxA expression in some patients with SSc, which correlates with the presence of ischemic ulcers and other signs of worse disease, suggesting a potential role of Type I IFN in the pathogenesis of this disease and/or its complications.

Interferon-β bioactivity measurement in multiple sclerosis: feasibility for routine clinical practice

Background Neutralising antibodies (NAb) to interferon beta (IFNβ) are associated with a reduced bioactivity and efficacy of IFNβ in multiple sclerosis (MS). Unclear is how to apply IFNβ bioactivity measurements (quantification of Myxovirus resistance protein A (MxA) mRNA) in clinical practice. Objectives To evaluate value and feasibility of IFNβ bioactivity measurement with a single MxA mRNA measurement for screening and a second measurement before and after IFNβ administration for definite confirmation of IFNβ bioactivity status. Methods In 79 MS patients MxA mRNA expression was determined 4 hours after IFNβ administration. If inadequate, MxA mRNA expression testing was repeated 3 months afterwards, comparing post- and pre injection samples to determine whether IFNb bioactivity was persistently lacking. MxA mRNA expression was compared to NAβ titres, determined by the cytopathic effect assay (CPE). Results NAb titres correlated significantly with MxA mRNA expression and MxA mRNA induction. Of all screened patients, only one patient had adequate MxA mRNA expression and high NAb titres simultaneously. Of the biological non-responders at second measurement (21/55), 17 (81%) were high-titre NAb positive, 1 (5%) was low-titre NAb positive and 3 (14%) were NAb negative. Without considering the pre-injection measurement, two more NAb negative patients would have tested negative for IFNβ bioactivity, emphasizing the need of a pre-injection sample. Conclusions Our data suggest that for IFNβ bioactivity screening a single post-injection measurement seems reasonable. However, MxA induction measurement based on both pre- and post-IFNβ injection samples at second measurement is somewhat more precise in determining ultimate IFNβ bioactivity status.

Increased Interferon Alpha Expression in Circulating Plasmacytoid Dendritic Cells of HIV-1-Infected Patients

The role of plasmacytoid dendritic cells (pDC) and interferon alpha (IFN alpha) in HIV-1 infection is still unclear. On one hand, HIV-1 disease is associated with a progressive decline of pDC, which displays reduced ability to produce IFN alpha after in vitro challenge. On the other hand, high IFN alpha serum levels in HIV-1-infected individuals have been proposed to promote immune hyper-activation and disease progression. We sought to determine whether disappearance of pDC in HIV-1 disease is due to homing in lymphoid tissues. We also studied IFN alpha and myxovirus resistance protein A (MxA) expression in unstimulated pDC and correlated these results with selected clinical and laboratory parameters. We found that pDC decline markedly in peripheral blood of patients progressing to disease but at the same time express much higher levels of IFN alpha and MxA compared to control individuals. On the other hand, we observed steady pDC counts in lymph nodes of HIV-1 patients. The frequency of circulating pDC correlated directly with CD4 cell counts and inversely with viral load. However, we found no correlation between IFN alpha and MxA expression levels, CD4 counts, and viral load. Circulating pDC decline sharply in the course of HIV-1 disease, but express high levels of IFN alpha, which may represent a hallmark of systemic immune dysfunction.

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.

Induction of innate immune response and absence of subsequent tolerance to dsRNA in biliary epithelial cells relate to the pathogenesis of biliary atresia

Biliary epithelial cells (BECs) possess negative regulatory mechanisms of Toll-like receptor (TLR)-based tolerance to bacteria (e.g. endotoxin tolerance). Viral infections of the Reoviridae genus with a dsRNA genome are suspected to be part of the aetiology of biliary atresia (BA), but the negative biliary mechanisms remain unexplored. Cultured human intrahepatic BECs (HIBECs) pretreated with polyinosinic-polycytidylic acid [poly(I:C)] (a synthetic analogue of viral dsRNA) for 24 h were exposed to poly(I:C) in fresh medium. The activation of nuclear factor-kappaB (NF-kappaB) and the expression of myxovirus resistance protein A (MxA) and tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) mRNAs were evaluated. Moreover, after the pretreatment, the transition of these molecules was examined in poly(I:C)-free conditions. Treatment with poly(I:C) significantly upregulated NF-kappaB activity in fresh HIBECs, and pretreatment failed to show tolerance to poly(I:C). The production of MxA and TRAIL was also preserved. Moreover, upregulation in the pretreated HIBECs was well preserved in poly(I:C)-free medium for at least 72 h. BECs fail to show tolerance to poly(I:C), and once innate immunity is activated it is sustained in poly(I:C)-free conditions, suggesting that the initiation of the immune response to dsRNA in HIBECs and its presence after the clearance of virus are closely associated with the progression of BA.

Biomarkers for interferon response in MS

Randomized, placebo-controlled studies have firmly established interferon beta (IFNβ) as standard therapy for relapsing remitting multiple sclerosis (RRMS).1–3 Many MS experts believe that early and continuous treatment with IFNβ reduces brain inflammation, irreversible CNS injury, and brain atrophy in RRMS, and reduces permanent neurologic disability. The use of IFNβ preparations has expanded to worldwide annual sales exceeding $4 billion USD. However, IFNβ is only partially effective (e.g., relapse rates are reduced by about 30%), so many patients have relapses, new MRI lesions while on treatment, and patients may become increasingly disabled with time. There are no sensitive, validated clinical markers of treatment response for individual patients. How is the neurologist to decide whether a patient is responding to treatment? Objective, practical markers of IFNβ pharmacologic response would be extremely helpful to guide therapy. In this issue of Neurology ®, Malucchi et al.4 describe a novel approach to the problem. Pharmacologic response was defined as increased levels of peripheral blood mononuclear cell myxovirus-resistance protein A (MxA) mRNA, 12 hours after an IFNβ injection. IFNβ exerts biologic effects by inducing expression of several hundred interferon-responsive genes (ISGs). This large number of ISGs is necessary …

Predictive markers for response to interferon therapy in patients with multiple sclerosis

Prolonged therapy with interferon beta (IFN beta) often leads to the development of anti-IFN beta binding antibodies (BAbs). A subset of the BAbs is of a neutralizing nature (neutralizing antibodies, NAbs) and is associated with reduced clinical efficacy of therapy. Myxovirus-resistance-protein A (MxA) has proven to be a reliable biomarker of IFN beta bioactivity. We analyzed the prognostic value of MxA mRNA, NAbs, and BAbs on the risk of having a new relapse in IFN beta-treated patients. A 3-year study was conducted in 137 IFN beta-treated patients. Blood samples for BAbs, NAbs, and MxA mRNA measurements were taken after 12 +/- 3 months of therapy. Analysis of relapse-free survival (RFS) was performed for all measures by using known thresholds, generating "positive" and "negative" groups. Also, time between sampling and following relapse and risk of new relapses were calculated. The MxA-negative group showed poorer RFS rates than the MxA-positive group [p < 0.0001, hazard ratio (HR) = 2.87]. Likewise, the NAb-positive group showed poorer RFS rates than the NAb-negative group (p =0.0013; HR = 2.49). On the contrary, BAb measurement did not show a clear clinical significance. Findings indicate that measurements of both myxovirus-resistance-protein A (MxA) and neutralizing antibodies (NAbs) predict the risk of new relapses; however, the slightly stronger prognostic significance of MxA mRNA and the easier method for it measurement make MxA mRNA the preferred biomarker for monitoring interferon beta (IFN beta)-treated patients. This information can be used to better tailor treatment to the individual patient with MS.

A high incidence of disease flares in an open pilot study of infliximab in patients with refractory inflammatory myopathies

Objective:To investigate the effect of the tumour necrosis factor (TNF) blocking agent infliximab in patients with treatment-resistant inflammatory myopathies.Methods:A total of 13 patients with refractory polymyositis (PM), dermatomyositis (DM), or...

Lentiviral-mediated GATA-3 RNAi Decreases Allergic Airway Inflammation and Hyperresponsiveness

GATA-3 is the key transcriptional factor for Th2 commitment in T cells and is strongly associated with asthma and allergic disease. We studied the silencing of the GATA-3 gene expression using RNA interference (RNAi) delivered by a lentiviral vector, to evaluate the therapeutic role of GATA-3 short hairpin RNAs (shRNAs) in a murine model of asthma. Mice were sensitized with OVA and instilled intratracheally (IT) with GATA-3 shRNAs lentiviral vector (Lenti-si-GATA-3) once, 48 hours before challenge. After three challenges with the OVA antigen, the mice were assessed for airway hyperresponsiveness (AHR) and inflammation. With infection of Lenti-si-GATA-3 in EL-4 cells, GATA-3 gene expression was abrogated and downstream Th2 cytokines, such as interleukin-4 (IL-4) and IL-5, were also significantly inhibited. IT delivery of Lenti-si-GATA-3 in OVA-immunized mice resulted in a strong inhibition of local GATA-3 gene expression. Treatment with Lenti-si-GATA-3 successfully alleviated OVA-induced airway eosinophilia and Th2 cytokine release. While evaluating AHR by means of enhanced pause (Penh) and pulmonary resistance (R(L)) using body plethysmography, it was found that the administration of Lenti-si-GATA-3 had significantly decreased AHR in OVA-immunized mice. These results suggest that inhibition of GATA-3 gene expression by shRNAs lentiviral vectors strongly attenuates antigen-induced airway inflammation and hyper-responsiveness in mice.

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.

Multiple sclerosis: Relating MxA transcription to anti-interferon-β-neutralizing antibodies

Interferon-β (IFNβ) treatment in multiple sclerosis (MS) induces neutralizing antibodies (NAB) in 10 to 30% of patients.1,2 NAB are associated with a reduction of bioactivity of IFNβ, and have a negative impact on therapeutic response.3 Analysis of IFNβ-inducible genes is a direct and practical approach to monitor therapy.4,5 The expression of three IFNβ-induced genes in antibody-positive patients with MS was recently analyzed.6 We performed a similar study to evaluate the relationship between the expression of myxovirus resistance protein A (MxA) and NAB activity. Our results confirm and extend previously reported results.6 We collected serum and PAXgene (PreAnalytiX/Qiagen, Hilden, Germany) samples from 81 patients with relapsing-remitting MS (RR-MS) (54 women, 27 men, median age 38, Expanded Disability Status Scale [EDSS] median 2.0, range 0 to 6.5) before (n = 62) and 12 to 24 hours after (n = 71) injection of IFNβ (Avonex, n = 12; Rebif, 3 × 22 μg, n = 13; Rebif, 3 × 44 μg, n = 39; Betaferon, n = 17). Treatment duration was >6 months in all cases. We also collected blood samples from 25 untreated control patients with RR-MS (19 women, 6 men, median age 32 years, EDSS median 2.0, range 0.0 to 5.0). We analyzed transcription of MxA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as housekeeping gene by TaqMan …

Development and validation of a real time PCR-based bioassay for quantification of neutralizing antibodies against human interferon-beta

There are two commonly employed types of bioassays for the detection of neutralizing antibodies (NAbs) against interferon-beta (IFNβ): the cytopatic effect assay (CPE), and the MxA (myxovirus resistance protein A) protein assay (MPA). This article describes a bioassay based on the real time PCR measurement of mRNA that results from the induction, in cultured human cells, of the MxA gene by IFNβ. Serum samples from 104 patients with multiple sclerosis (MS) treated with IFNβ were tested for NAbs using our real time PCR bioassay. NAbs also were measured in the same specimens by the MPA assay and CPE assay. The calibration range of the real time PCR bioassay is 0.125–30 LU/mL. The range of the intra- and inter-assay variations (coefficients of variation in log 10) were 4.05% (range 0.88%–7.90%) and 4.42% (range 0.31%–9.15%), respectively. Samples of the three commercial preparations of IFNβ-1a and -1b were measured showing dose–response curves parallel to that of the NIH reference IFNβ (mean SD at the midpoint of the dose–response curve = 5%). In addition, the assay was robust with respect to number of cells plated (i.e., increasing cell densities from 12 × 10 3/well to 384 × 10 3/well resulted in 3.03% variability in MxA expression normalized with glyceraldehyde-3 phosphate dehydrogenase). NAbs titers measured were closely comparable to those obtained by the MPA [ r spearman = 0.899; 89% of observed agreements; K = 0.779] and the CPE [ r spearman = 0.7899); 86%; K = 0.729] assays. Despite the obvious disadvantage of cost, when carried out according to quality assurance guidelines for molecular diagnostics the new MxA gene-expression assay (MGA) has significant advantages over the other methods for testing NAbs: it has excellent reliability and reproducibility, and utilizes equipment and methodologies already accessible in many clinical laboratories.

MxA gene expression in juvenile dermatomyositis peripheral blood mononuclear cells: Association with muscle involvement

Juvenile dermatomyositis (JDM), a systemic vasculopathy, is characterized by inflammation of skin and muscle. Muscle biopsies from untreated JDM patients show upregulation of type I interferon (IFN)-inducible genes, including myxovirus resistance protein A (MxA). The present study examines whether MxA mRNA expression in peripheral blood mononuclear cells (PBMC) from JDM patients: (1) is elevated compared to healthy controls, (2) reflects disease activity, and (3) changes with the onset of clinically effective treatment. MxA mRNA expression in JDM PBMC obtained at the initial clinic visit was elevated compared to controls and was positively correlated with Disease Activity Score (DAS) for muscle, but not with DAS for skin, suggesting that damage to skin and muscle in JDM may each have a discrete pathophysiology. During the course of clinically effective treatment, decrease in muscle symptoms was associated with a decrease in PBMC MxA mRNA expression.

Single nucleotide polymorphisms and functional analysis of MxA promoter region in multiple sclerosis

Objective Interferons (IFNs)-inducible myxovirus resistance protein A (MxA) has recently been used as an indirect marker of neutralizing antibody against IFN in patients with multiple sclerosis (MS). On the other hand, MxA inhibits the replication of viruses by means of modifying cellular function, including apoptotic pathway. Our objective is to investigate the genetic and pathological role of MxA in patients with MS. Methods We examined SNPs of MxA promoter region in 67 patients with MS. Moreover, to elucidate the functional roles of SNPs, we conducted Luciferase assay with pGL3-basic vector including patient-derived or artificially mutated MxA promoter region. Results A significantly higher frequency of the haplotype with − 88T and − 123A, which correlates with over-expression of MxA, was observed in MS. Moreover, we elucidated novel findings showing that nt − 88 played a leading part with type I IFNs and that nt − 123 played the same role independently without type I IFNs, respectively. Conclusion SNPs on MxA promoter region may play an important role in the pathophysiology of MS and provide a novel strategy for the therapeutic resolutions of MS.

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.

Biological markers of interferon-beta therapy: comparison among interferon-stimulated genes MxA, TRAIL and XAF-1

Biological activity of interferon-beta (IFNβ) can be assessed by measuring IFN-stimulated genes (ISGs). Among them, myxovirus resistance protein A (MxA) appears to have the highest specificity, but it has no role in the pathogenesis of multiple sclerosis (MS). To investigate the reliability of MxA as a biomarker, we compared its expression to that of two other ISGs: TNF-related apoptosis-inducing ligand (TRAIL) and X-linked inhibitor of apoptosis factor-1 (XAF-1). Both were shown to be involved in immunoregulatory mechanisms and might play a role in MS. Quantitative-PCR measurements were performed in peripheral blood mononuclear cells from 73 MS patients after short-term and long-term treatment with IFNβ. A time-dependent response for multiple ISGs was observed in all patients after short-term treatment. In contrast, long-term treatment induced concurrent inhibition of ISGs in 12.3% (9/73) of patients, in whom neutralizing antibodies (NAbs) were detectable. Besides, 22% (16/73) of chronically treated patients showed a non-NAbs-related abrogation of TRAIL expression. In summary, 1) MxA expression was significantly higher than both TRAIL and XAF-1, and 2) MxA was the most sensitive gene to detect decreased bioavailability due to NAbs. These findings identify MxA as an appropriate biomarker for IFNβ, although there is no evidence for a functional role of it in MS.

97. Type I Interferon Response Against Virus Vectors and Non-Viral Gene Transfer

The first line of defense that gene delivery vectors, viral or non-viral, confront in cells is the type I interferon (IFN) response. Cells produce type I IFNs as a response to dsRNA (intermediates of viral replication) and other viral components. IFNs induce the expression of IFN stimulated genes that can be used as markers for IFN response. One of these IFN stimulated genes is the Myxovirus resistance protein A (MxA).

Measurement of neutralizing antibodies to interferon beta in patients with multiple sclerosis.

Treatment of multiple sclerosis (MS) with interferon beta (IFNbeta) can be associated with the development of binding antibodies (BAbs) and neutralizing antibodies (NAbs). NAbs are a subset of BAbs that prevent IFNbeta from effectively binding to or activating its receptor, thereby blocking its biologic effects and inhibiting its therapeutic effects. Several factors can affect the incidence and titers of NAbs that develop to IFNbeta, including the type of IFNbeta preparation used for treatment. One of the major limitations to evaluating the relative importance of these factors is the variation in assays used to detect IFNbeta antibodies. Two major types of assays are used to detect antibodies to IFNbetas: [1] binding assays, which measure the ability of antibodies in patients' sera to bind to IFNbeta; and [2] neutralization assays (or bioassays), which measure the ability of patients' sera to neutralize the biologic effects of IFNbeta. Assays used to detect NAbs differ in their sensitivity and specificity, and there can be high variability between laboratories in how these assays are performed (e. g., types of cells, quantity of IFNbeta). This article reviews assays currently used for detecting NAbs to IFNbeta and discusses the development of an international standard NAb assay. The myxovirus resistance protein A (MxA) assay is recommended as the standard assay for the quantification of NAbs providing availability of reagents.

Neutralizing antibodies against IFN-beta in multiple sclerosis: antagonization of IFN-beta mediated suppression of MMPs.

Neutralizing antibodies (NAb) against interferon-beta (IFN-beta) develop in about a third of treated multiple sclerosis patients and are believed to reduce therapeutic efficacy of IFN-beta on clinical and MRI measures. The expression of the interferon acute-response protein, myxovirus resistance protein A (MxA) is a sensitive measure of the biological activity of therapeutically applied IFN-beta and of its reduced bioavailability due to NAb. However, MxA may not be operative in the pathogenesis of multiple sclerosis or the therapeutic effect of IFN-beta. Instead, matrix metalloproteinases (MMPs) are increased in brain tissue, CSF and blood circulation of multiple sclerosis patients and function as effector molecules in several steps of multiple sclerosis pathogenesis. One of the molecular mechanisms by which IFN-beta exerts its beneficial effect in multiple sclerosis is reduction of MMP-9 expression and increase of its endogenous tissue inhibitor, TIMP-1. Quantitative PCR measurements of MMP-2 and MMP-9, TIMP-1 and TIMP-2, and MxA were performed in peripheral mononuclear cells from clinically stable multiple sclerosis patients with relapsing remitting disease course after short-term and long-term treatment with IFN-beta. IFN-beta therapy down-regulated the expression of MMP-9 and abolished that of MMP-2 in long-term, but not short-term treated multiple sclerosis, while levels of MxA were increased in both instances. The presence of NAb reversed these effects, i.e. led to reduced MxA and increased MMP-2/MMP-9 expression levels compared with NAb- patients. In contrast, expression of TIMPs in peripheral blood mononuclear cells remained unaffected by IFN-beta therapy and the presence of NAb. While MxA is able to detect the biological action and reduced bioavailability of IFN-beta on the basis of single injections, only MMP-9 shows quantitative correlation with the NAb titre. Together with evidence that an imbalance between MMP and TIMP expression is a crucial pathogenetic feature in multiple sclerosis, these findings support the concept of a significant role of NAb in reducing the therapeutic efficacy of IFN-beta.