Quantitation of interferon-induced Mx protein in whole blood lysates by an immunochemiluminescent assay: elimination of protease activity of cell lysates in toto

Sexual maturation in Atlantic salmon induces a constitutive Mx protein production and influences the infectious pancreatic necrosis virus carrier-status

The aim of this study was to demonstrate for the first time that sexual maturation induces a constitutive increase in Mx gene expression and protein production in Atlantic salmon. This could explain the reduction in IPNV prevalence previously observed in broodfish at the time of ova/milt stripping. For this purpose, Mx transcript and protein levels were analysed in different tissues/samples and compared between mature broodfish (female and male) and immature parr.

New sandwich-type enzyme-linked immunosorbent assay for human MxA protein in a whole blood using monoclonal antibodies against GTP-binding domain for recognition of viral infection

OBJECTIVES

To develop a clinically significant and practical enzyme-linked immunosorbent assay (ELISA) for the detection of MxA protein in human whole blood, a biological marker of viral infection.

DESIGN AND METHODS

A sandwich ELISA suitable for the measurement of human MxA protein in whole blood was developed using mouse monoclonal antibodies (mAbs) raised against the GTP-binding domain of human MxA protein. Prior to the assay, the whole blood sample was treated with special buffer to extract the MxA protein, improve its stability, and avoid interference from hemoglobin.

RESULTS

This ELISA meets all the requirements for use in routine clinical assays, especially in terms of sensitivity (detection limit: 1.3 ng/ml whole blood), accuracy (recovery: 93.0-100.0%), and rapidity (<1.5 h). The present ELISA had a sensitivity of 100% and a specificity of 100% for viral infection when compared to samples from healthy control and 87.1% and 90.9% when compared to samples from the bacterial infection group.

CONCLUSION

We have developed a new ELISA for measuring MxA protein in human whole blood using mAbs specific for the GTP-binding domain of MxA. This ELISA has analytical performance enough for routine clinical assay and can be used in detecting the possibility of viral infection.

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

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

The MxA EIA assay seems to be a practical method for large-scale analysis of the bioactivity of IFN-beta treatment.

Dynamics of interferon-beta modulated mRNA biomarkers in multiple sclerosis patients with anti-interferon-beta neutralizing antibodies

The objective of this study was to evaluate multiple interferon (IFN) specific mRNA biomarkers in multiple sclerosis (MS) patients with anti-IFN-beta neutralizing antibodies (NAB) using a pharmacodynamic study design. Thirty patients were enrolled. Blood samples were drawn at pre-treatment, 4-, 8-h time points following the intramuscular dose of IFN-beta-1a. Total RNA was obtained from peripheral blood cells, processed to cDNA and analyzed using quantitative real-time polymerase chain reaction. Pre-treatment serum samples were analyzed for anti-IFN-beta binding and neutralizing antibodies: 22 patients were NAB negative; equal numbers of the eight remaining patients were either NAB positive or had borderline NAB status. The results showed that early assessment (at 4 h after IFN-beta injection) of mRNAs for Stat-1, MxA, MxB and TRAIL was more sensitive than the later measurements. Furthermore, the NAB positive patients had strongly attenuated gene expression responses on all the mRNAs. Patients with borderline NAB had average responses that appear to be lower than NAB negative patients on several genes, notably Stat-1, TRAIL and beta2 microglobulin.

Biological assays for interferons

Interferons (IFN) are potent biologically active proteins synthesised and secreted by somatic cells of all mammalian species. They have been well characterised, especially those of human origin, with respect to structure, biological activities, and clinical therapeutic effects. While structural differences are known to exist among the IFN species that constitute the "IFN family" and despite the existence of different receptors for type I and type II IFN, all species have been shown to exert a similar spectrum of in vitro biological activities in responsive cells. Principal among the biological activities induced by IFN is antiviral activity, the activity used to originally define IFN. Antiviral activity of IFN is mediated via cell receptors and is dependent on the activation of signalling pathways, the expression of specific gene products, and the development of antiviral mechanisms. Sensitivity of cells to IFN-mediated antiviral activity is variable, and depends on a number of factors including cell type, expression of IFN receptors and downstream effector response elements, effectiveness of antiviral mechanisms, and the type of virus used to infect cells. Nevertheless, by the judicious use of sensitive cell lines in combination with appropriate cytopathic viruses, effective assays to measure the antiviral activity have been developed. Historically, "antiviral assays" (AVA) were the first type of biological assays that were developed to measure the relative activity or potency of IFN preparations. However, the subsequent discoveries of several other biological activities of IFN has opened the way to the development of assays based on one or other of these activities. The latter include inhibition of cell proliferation, regulation of functional cellular activities, regulation of cellular differentiation and immunomodulation. More recently, the cloning of IFN responsive genes has led to the development of "reporter gene assays". In this case, the promoter region of IFN responsive genes is linked with a heterologous reporter gene, for example, firefly luciferase or alkaline phosphatase, and transfected into an IFN-sensitive cell line. Stably transfected cell lines exposed to IFN increase expression of the reporter gene product in direct relation to the dose of IFN, the readout being a measure of this product's enzymic action. The current review aims to give a critical overview of the development, specificity, standardisation and present use of the various biological assay methods now available for the quantification of IFN activity.

Increased levels of antiviral MxA protein in peripheral blood of patients with a chronic disease of unknown etiology

Interferon alpha (IFN-alpha) is synthesized in response to viral infections. MxA protein, induced specifically by IFN-alpha and beta, expressed in peripheral blood cells, is detected more consistently than circulating IFN-alpha in serum of patients with viral infections. Thus, activation of the IFN-alpha/MxA system can be used as additional marker of the presence of a virus in patients. Therefore MxA protein and IFN-alpha levels were measured in patients with multiple sclerosis (MS), a chronic neurological disease of unknown etiology, in order to investigate the possible role of viruses in the expression of this disease. The means of MxA values obtained by using an immunochemiluminescent assay were significantly higher in blood of patients with remitting (n = 197) or relapsing (n = 39) multiple sclerosis (MS) patients and in patients with viral infections than in blood from healthy controls (n = 25) and from patients with bacterial infections (n = 12). Intra-individual variance in MxA levels in seven clinically stable remitting patients with MS was observed in the course of a follow-up, and high MxA levels were detected in three of them in blood samples collected consecutively over several months. By using an ultra sensitive assay, a higher MxA-inducer activity was obtained with sera from MS patients (n = 39) than with those from healthy controls (n = 12). Experiments with neutralizing antibodies proved that this activity in serum from patients was due to IFN-alpha, whereas IFN-alpha could not be detected by other methods. Altogether these results demonstrate that there is an activation of the IFN-alpha/MxA system in MS patients, which is consistent with the hypothesis that a viral infection may be associated with MS.

Evaluation of bioavailability of three types of IFNbeta in multiple sclerosis patients by a new quantitative-competitive-PCR method for MxA quantification

Intracellular expression of human myxovirus protein A (MxA) is exclusively induced by type I IFNs (IFNalpha,beta,omega) or by some viruses and it is strongly increased under IFN treatment. We set up an internally controlled quantitative-competitive polymerase chain reaction (qc-PCR) that quantifies MxA mRNA expressed in human peripheral blood mononuclear cells (PBMC). Our qc-PCR is accurate because the mean ratio of copy number estimated by qc-PCR to that quantified spectrophotometrically is 1.08+/-0.03, moreover it is repeatable with high sensitivity (1 fg MxA/pg GAPDH). MxA mRNA was tested in 47 Relapsing-Remitting Multiple Sclerosis (RR-MS) untreated patients and in 48 patients treated with one of the 3 IFNbeta licensed for MS (24 with Rebif, 14 with Avonex and 10 with Betaferon). All the 48 treated patients were negative to IFNbeta neutralising antibodies (NABs) as tested in our laboratory using a cytopathic assay (CPE). MxA mRNA levels were detectable in all untreated patients (mean 24+/-18 fg MxA/pg GAPDH) and significantly higher levels were found in all the treated patients 12 h after IFNbeta administration (mean 499+/-325 fg MxA/pg GAPDH); furthermore, the three types of IFNbeta showed comparable bioavailability. Our data indicate that the bioavailability of the three available types of IFNbeta can be evaluated by MxA qc-PCR.

Characterization and humanization of a monoclonal antibody that neutralizes human leukocyte interferon: a candidate therapeutic for IDDM and SLE

We have developed a panel of murine monoclonal antibodies that recognize human interferon alpha. One of these mononclonal antibodies binds and neutralizes, with high affinity, all of seven tested recombinant human interferon alphas. This mononclonal antibody also neutralizes the interferon activity present in two independent pools of interferon alphas prepared following stimulation of human peripheral blood leukocytes. The complementary determining regions from this murine mononclonal antibody were transferred to a human IgG2 heavy chain and to a human kappa1 light chain. In addition, six (heavy chain) and two (light chain) amino acids were transferred from the framework regions. This generated a humanized mononclonal antibody that retained the specificity of the mouse parent. The humanized anti-interferon alpha antibody is a candidate therapeutic for those diseases, such as insulin-dependent diabetes, systemic lupus erythematosis, psoriasis and Crohn's disease, which are all characterized by pathological expression of interferon alpha.

Correlation of interferon-induced expression of MxA mRNA in peripheral blood mononuclear cells with the response of patients with chronic active hepatitis C to IFN-alpha therapy

MxA, a protein with selective activity against certain viruses, is an accepted specific indicator of type I interferon (IFN) activity. We have developed an internally controlled quantitative-competitive PCR to measure the amounts of MxA mRNA expressed in peripheral blood mononuclear cells (PBMC). This assay is more sensitive, quantitative, and easily applied to serial clinical samples than previously described methods. We have applied this assay retrospectively to 27 patients with chronic active hepatitis C given IFN-alpha2. Most such patients gain no sustained benefit but nevertheless suffer from the side effects, expense, and inconvenience of the treatment. Fourteen of the 27 had been classified on clinical grounds as responders and 13 as nonresponders at the end of a 6 month treatment period. We measured MxA mRNA in PBMC obtained before and after 8 weeks of IFN-alpha2 treatment. All the patients expressed some level of mRNA before treatment began, and after 8 weeks of treatment, the level rose in 19. This increase was significant (p < 0.001) only in patients classified as responders. This strongly suggests that hepatitis C virus (HCV) patients who express increased amounts of MxA mRNA in their PBMC during IFN-alpha treatment are most likely to obtain long-term benefit. If this finding is confirmed in future prospective studies, it will provide an extremely important predictive marker for managing IFN-alpha therapy in patients with HCV.

Interferon-inducible Mx proteins in fish

Mx proteins are members of a family of interferon-inducible genes expressed when cells are treated with double-stranded RNA or virus infection. These proteins are important components of the antiviral response and form the first line of the body's defense against virus infections. The exact mechanism of action for these proteins has not been discovered, but mice missing the Mx genes are extremely sensitive to influenza virus infection. Mammals have between two and three Mx genes whose functions may vary with regard to the inhibition of a specific virus, cellular localization, and activity. The cDNA of three rainbow trout Mx proteins has been cloned and a comparison of their sequences with that of avian and mammalian species reveals striking conservation of domains. They all maintain the tripartite ATP/GTP binding domain and the dynamin family signature in the amino terminal half of the protein. In the carboxyl terminal half of the Mx proteins are the localization signals and the leucine zipper motifs which account for the trimerization of Mx in the cell. Like the rat and human Mx proteins, the different trout Mx proteins exhibit distinctly different immunohistochemical staining patterns in cells transfected with plasmids expressing RBTMx1, RBTMx2, or RBTMx3. To date, the antiviral function of the trout Mx proteins has not been satisfactorily established.

A novel sensitive and selective bioassay for human type I interferons

We describe a novel MxA gene-induction assay for type I interferons (IFN-alpha and IFN-beta) based on the specific induction of the MxA gene in cultured human cells. Accumulated intracellular MxA protein is determined by immunologic measurement by a rapid method using commercially available materials. IFN activity can be measured accurately over a concentration range of 0.1-30 IU/ml. In contrast, type II IFN and other cytokines are not significantly detected. The MxA-induction assay has advantages in terms of specificity, reliability, and sensitivity over other methods for assaying type I IFN. It has also been adapted and validated for measuring the titers of anti-IFN-beta neutralizing antibodies in human sera.

Comparative study of the pharmacodynamic and pharmacologic effects of Betaseron and AVONEX

The aim of this 1 week study was to compare the biologic effects induced by Betaseron and AVONEX using their approved dose, route, and schedule. Sixteen healthy volunteers were randomly assigned to receive either a single i.m. dose of AVONEX (6 million International Units [MIU]) or, every other day s.c. doses of Betaseron (8 MIU). Common side effects associated with interferon-beta (IFN-beta) treatment and biologic response parameters (neopterin, beta2-microglobulin, interleukin-10 [IL-10], and MxA protein levels in blood) were measured. Ibuprofen was administered to all subjects throughout the study. Fever, chills, and myalgia occurred most frequently and with the greatest severity between 6 and 12 h after the first dose of either IFN-beta. Despite the additional dosing of subjects in the Betaseron group, the incidence, duration, and severity of the side effects were not significantly different from those in the AVONEX group. Biologic response parameters reached similar maximum concentrations in both treatment groups. In the Betaseron group, neopterin and beta2-microglobulin levels remained significantly greater than baseline throughout the 7 day study, whereas those in the AVONEX group were elevated only through day 5. Betaseron treatment significantly increased IL-10 levels above baseline, but AVONEX treatment did not. The overall induction of neopterin, beta2-microglobulin, and IL-10 (as measured by area under the concentration-time curve) was significantly greater in the Betaseron group than the AVONEX group (p = 0.031). The results of this study demonstrate that the approved Betaseron dosing regimen, in combination with ibuprofen use, provided a significantly greater and more consistently elevated biologic response compared with that of AVONEX and did so with a side effects profile comparable to that of once a week AVONEX dosing.

The MxA protein levels in whole blood lysates of patients with various viral infections

Interferon alpha (IFNalpha), a type I interferon, can be considered as a viral infection marker because this cytokine is induced during many viral infections. However, it is quite difficult to detect IFNalpha in sera. Investigations are interested in various intra-cellular IFNalpha-induced proteins as viral infection markers. However the activity of these enzymes increased not only in response to type I IFNs but also to type II IFN. MxA protein can be detected in the cytoplasm of IFNalpha/beta-treated cells, whereas other cytokines, including IFNgamma, are poor inducers. Using an immunochemiluminescent assay, we studied MxA protein in whole blood of 34 patients with various viral infections. The whole blood was drawn into sterile vacuum tubes containing heparin or EDTA. MxA values were relatively similar in heparin-treated samples and EDTA-treated samples, with differences not exceeding 1 ng/ml. The levels of MxA protein were compared in whole blood obtained by using two different lysis procedures. A correlation was found between the MxA levels obtained by using procedure I and procedure II, but higher amounts of MxA protein were found with procedure II. The second procedure is rapid and more convenient than the other and it is carried out in one step which reduce technical problems. High levels of MxA protein were found in peripheral blood cells of patients with acute viral infections (Rotavirus, Adenovirus, RSV, CMV), but MxA protein was not elevated in bacterial infections. The MxA levels were also studied in peripheral blood of 32 HCV positive patients. MxA protein was not found in most of IFNalpha-untreated patients, even those with high viral load. In contrast, high levels of MxA protein were found in IFNalpha-treated patients. MxA quantitation can be considered as a specific marker of acute viral infections, and could be useful in the management of treatment with IFNalpha.

Interferon gamma producing blood lymphocytes are decreased by interferon beta therapy in patients with multiple sclerosis

OBJECTIVE

We studied the individual course of interferon gamma producing blood lymphocyte count (IFGC) of 15 multiple sclerosis patients started on 8 MIU beta interferon administered subcutaneously each other day.

METHODS

Mononuclear blood cells were prepared before treatment and on day 3, 9, 15, as well as after month 1, 2, 3 and 4 of therapy. After stimulation intracellular interferon gamma was detected with monoclonal fluorescent antibodies and measured by flow cytometry. IFGC is given as percentage of all gated lymphocytes.

RESULTS

forty-eight hours after first interferon beta application the mean IFGC dropped significantly from 11.37 to 7.09 (P < 0.05) and to 4.22 within 4 months. Whereas the majority of patients showed a decrease of IFGC from the beginning of therapy, in three of the 15 patients a transient increase of IFGC was seen suggesting a different response to immunomodulatory therapy.

CONCLUSIONS

Interferon gamma producing lymphocyte count might be a useful tool to determine the biological effect of interferon beta therapy in multiple sclerosis patients.

Use of an indirect pharmacodynamic stimulation model of MX protein induction to compare in vivo activity of interferon alfa-2a and a polyethylene glycol-modified derivative in healthy subjects

Interferon alfa-2a was chemically modified by the covalent attachment of a polyethylene glycol (PEG) moiety to enhance its circulating half-life and to reduce its immunogenicity. A comparative evaluation of the pharmacokinetics of the PEG-modified interferon alfa-2a showed a greater than twofold increase in the circulating half-life as a result of this chemical modification. An indirect physiologic response model was developed to characterize the time course of the MX protein response after subcutaneous administration of single ascending doses of either interferon alfa-2a or PEG-interferon alfa-2a in healthy volunteers. Analysis of the pharmacokinetic-pharmacodynamic relationship suggested that the PEG-modified interferon alfa-2a could not be administered less than twice weekly and therefore offered little therapeutic advantage over its unmodified counterpart, which is administered three times weekly. These results were consistent with findings in phase II trials. This study substantiates the usefulness of pharmacodynamic modeling as a tool for the development of dose recommendations and for the early selection of drug candidates in the drug development process.