Expression Of MxA Protein Research Articles

VP24 matrix proteins of eight filoviruses downregulate innate immune response by inhibiting the interferon-induced pathway.

Filoviruses encode viral protein 24 (VP24) which effectively inhibit the innate immune responses in infected cells. Here we systematically analysed the effects of nine mammalian filovirus VP24 proteins on interferon (IFN)-induced immune response. We transiently expressed Ebola, Bombali, Bundibugyo, Reston, Sudan and Taï Forest ebolavirus (EBOV, BOMV, BDBV, RESTV, SUDV, TAFV, respectively), Lloviu virus (LLOV), Mengla dianlovirus (MLAV) and Marburgvirus (MARV) VP24 proteins and analysed their ability to inhibit IFN-α-induced activation of myxovirus resistance protein 1 (MxA) and interferon-induced transmembrane protein 3 (IFITM3) promoters. In addition, we analysed the expression of endogenous MxA protein in filovirus VP24-expressing cells. Eight filovirus VP24 proteins, including the VP24s of the recently discovered MLAV, BOMV and LLOV, inhibited IFN-induced MxA and IFITM3 promoter activation. MARV VP24 was the only protein with no inhibitory effect on the activation of either promoter. Endogenous MxA protein expression was impaired in cells transiently expressing VP24s with the exception of MARV VP24. We mutated nuclear localization signal (NLS) of two highly pathogenic filoviruses (EBOV and SUDV) and two putatively non-pathogenic filoviruses (BOMV and RESTV), and showed that the inhibitory effect on IFN-induced expression of MxA was dependent on functional cluster 3 of VP24 nuclear localization signal. Our findings suggest that filovirus VP24 proteins are both genetically and functionally conserved, and that VP24 proteins of most filovirus species are capable of inhibiting IFN-induced antiviral gene expression thereby efficiently downregulating the host innate immune responses.

Low MxA Expression Predicts Better Immunotherapeutic Outcomes in Glioblastoma Patients Receiving Heat Shock Protein Peptide Complex 96 Vaccination.

Heat shock protein peptide complex 96 (HSPPC-96) has been proven to be a safe and preliminarily effective therapeutic vaccine in treating newly diagnosed glioblastoma multiforme (GBM) (NCT02122822). However, the clinical outcomes were highly variable, rendering the discovery of outcome-predictive biomarkers essential for this immunotherapy. We utilized multidimensional immunofluorescence staining to detect CD4+ CD8+ and PD-1+ immune cell infiltration levels, MxA and gp96 protein expression in pre-vaccination GBM tissues of 19 patients receiving HSPPC-96 vaccination. We observed low MxA expression was associated with longer OS than high MxA expression (48 months vs. 20 months, p=0.038). Long-term survivors (LTS) exhibited significantly lower MxA expression than short-term survivors (STS) (p= 0.0328), and ROC curve analysis indicated MxA expression as a good indicator in distinguishing LTS and STS (AUC=0.7955, p=0.0318). However, we did not observe any significant impact of immune cell densities or gp96 expression on patient outcomes. Finally, we revealed the association of MxA expression with prognosis linked to a preexisting TCR clone (CDR3-2) but was independent of the peripheral tumor-specific immune response. Taken together, low MxA expression correlated with better survival in GBM patients receiving HSPPC-96 vaccination, indicating MxA as a potential biomarker for early recognition of responsive patients to this immunotherapy.Clinical Trial Registration: ClinicalTrials.gov (NCT02122822) http://www. chictr.org.cn/enindex.aspx (ChiCTR-ONC-13003309).

AB017. Increased dendritic cells and IFN-beta and MxA protein expression in spongiotic dermatitis differentiates dermatomyositis from eczema

BackgroundDermatomyositis (DM) is conventionally characterized by interface dermatitis (ID) on skin histopathology. A subset of patients with clinically diagnosed DM have skin biopsies showing spongiotic dermatitis (SD), a histopathology more commonly seen in eczema. Diagnosis of DM is challenging, with significant delays following initial presentation. (I) To identify the percentage of clinically diagnosed DM patients with skin biopsies showing SD, (II) to identify cytokine and cell markers that can determine if a skin biopsy showing SD is consistent with DM in a patient with clinical DM.MethodsBiopsies from 10 DM patients with SD histopathology were compared to biopsies from 10 healthy controls, 10 patients with eczema, and 12 patients with DM with ID histopathology. Skin biopsies were stained by H&E and by immunohistochemistry for MxA, IFN-beta, CD11c (mDC), and BDCA2 (pDC). Cytokines were quantified by area and intensity. Cells were quantified per HPF. Fisher’s exact test was used to compare baseline patient characteristics. One-way ANOVA with Bonferroni’s multiple comparison test was used to compare protein expression between groups.ResultsEleven of 164 (6.7%) patients with a clinical diagnosis of DM at our tertiary care center were identified as having SD. MxA, IFN-beta, CD11c (mDC), and BDCA2 (pDC) protein expression is significantly higher in DM-SD compared to eczema and healthy controls. Expression of MxA, IFN-beta and BDCA2 were not significantly different between DM-SD and DM-ID.ConclusionsIncreased MxA, IFN-beta, CD11c, and BDCA2 protein expression can help distinguish between DM-SD and eczema.

Increased MxA protein expression and dendritic cells in spongiotic dermatitis differentiates dermatomyositis from eczema in a single-center case-control study.

Dermatomyositis (DM) is conventionally characterized by interface dermatitis (ID) on skin histopathology. A subset of DM patients has skin biopsies showing spongiotic dermatitis (SD), a histopathology more commonly seen in eczema. In this study, we aimed to (a) identify the percentage of clinically diagnosed DM patients with SD skin biopsies, (b) identify cytokine and cell markers that can help determine if a SD skin biopsy is consistent with DM. In this case-control study, biopsy specimens from ten DM patients with SD (DM-SD) were compared to specimens from ten healthy controls, ten patients with eczema, and 12 patients with DM with ID (DM-ID). Specimens were stained by immunohistochemistry for MxA, IFN-β, CD11c, and BDCA2. One-way ANOVA with Bonferroni's multiple comparison test was used to compare protein expression between groups. Eleven of 164 (6.7%) patients with a clinical diagnosis of DM at our tertiary care center were identified as having SD. MxA, IFN-β, CD11c, and BDCA2 protein expression was significantly higher in DM-SD compared to eczema and healthy controls. Expressions of MxA, IFN-β, and BDCA2 were not significantly different between DM-SD and DM-ID. Increased MxA, IFN-β, CD11c, and BDCA2 protein expression may aid in distinguishing between DM-SD and eczema and warrants further investigation.

Interferon inducible antiviral MxA is inversely associated with prostate cancer and regulates cell cycle, invasion and Docetaxel induced apoptosis.

The interferon inducible Myxovirus (influenza virus) resistance A (MxA) is considered as a key mediator of the interferon-induced antiviral response. Mx proteins contain the typical GTP-binding motif and show significant homology to dynamin family of GTPases. Strong interaction of MxA with tubulin suggests that Mx proteins could be involved in mitosis. Studies have shown that MxA inhibit tumor motility/metastasis and virus induced apoptosis. However, the clear association between MxA expression and cancer remains unknown. Meta-analysis suggested that MxA expression was inversely correlated with prostate cancer (PCa). In this study, we demonstrate the expression MxA in PCa and its functional significance on the cancer phenotype. The expression of MxA protein in prostate cancer was examined by immuno-histochemistry. MxA was knocked down (shMxA) or over-expressed (pMxA) in DU145 or LNCaP PCa cell lines respectively. These cell lines were used to study proliferation, apoptosis, invasion, migration, and anchorage independent growth. Co-localization of MxA with tubulin was performed by immuno-cytochemistry following Docetaxel treatment. The expression of MxA protein was significantly decreased in PCa as compared to the normal tissues. DU145 cells lacking MxA (DU145 + chMxA) showed significant increase in proliferation, associated with decreased expression of CDKN1A and B. Increased migration, anchorage independent growth in DU145 + shMxA cells was associated with increased MMP13 expression. Tubulin organization was also dependent on MxA expression. Tubulin polymerizing agents such as Docetaxel was less effective in promoting apoptosis in cells lacking MxA due to altered tubulin organization. Gain of MxA expression in LNCaP cells (LNCaP + pMxA) resulted in cell cycle arrest that was associated with increased expression of CDKN1A. MxA expression was also down-regulated by dihydrotestosterone in LNCaP cells. MxA expression is inversely correlated with prostate cancer. Down-regulation of MxA in LNCaP cells by DHT suggests that MxA could play a significant role in disease progression. Loss of MxA expression results in increased metastasis and decreased sensitivity to Docetaxel suggesting that MxA expression could determine the outcome of chemo-therapeutic treatment. Additional studies will be required to fully establish the cross-talk between androgen receptor-IFN pathway in regulating MxA expression in the normal prostate and prostate cancer. Prostate 75:266-279, 2015. © 2014 Wiley Periodicals, Inc.

Cell-Type Specific Interferon Stimulated Gene Staining in Liver Underlies Response to Interferon Therapy in Chronic HBV Infected Patients

Interferon-α is approved as one of the main therapeutic treatments for chronic hepatitis B virus infection, but only a small number of patients achieve sustained virological response. The molecular mechanisms underlying IFN-α resistance in those patients who do not respond remain elusive. Previous work in our laboratory identified the pre-activation of IFN signaling leading to increased expression of a subset of interferon stimulated genes in the pretreatment liver tissues of chronic HBV infected patients correlated with treatment non-response. We studied the cell-type specific gene expression of interferon stimulated genes in the liver of chronic HBV infected patients and the cellular basis of the phenotype through ISG15 and MxA protein expression. Immunohistochemical analysis was used to detect the expression of ISG15 and MxA protein in the pretreatment liver tissues of chronic HBV infected patients and the expression patterns were correlated with treatment outcomes. In the non-responders, ISG15 and MxA protein expression in the pretreatment liver tissues was more pronounced in hepatocytes while in the responders, ISG15 and MxA protein expression was more focused in macrophages. ISG15 and MxA proteins were occasionally expressed in hepatocytes in normal livers. There were significant differences in the cell-type specific protein expression of ISG15 and MxA in the pretreatment liver tissues of chronic HBV infected patients between treatment responders and non-responders. An easy prediction method based on immunohistochemical stains of a subset of interferon stimulated genes may be developed to predict treatment outcomes of IFN therapy in chronic HBV infected patients.

Antiviral immune responses in H5N1-infected human lung tissue and possible mechanisms underlying the hyperproduction of interferon-inducible protein IP-10

Information on the immune response against H5N1 within the lung is lacking. Here we describe the sustained antiviral immune responses, as indicated by the expression of MxA protein and IFN-α mRNA, in autopsy lung tissue from an H5N1-infected patient. H5N1 infection of primary bronchial/tracheal epithelial cells and lung microvascular endothelial cells induced IP-10, and also up-regulated the retinoic acid-inducible gene-I (RIG-I). Down-regulation of RIG-I gene expression decreased IP-10 response. Co-culturing of H5N1-infected pulmonary cells with TNF-α led to synergistically enhanced production of IP-10. In the absence of viral infection, TNF-α and IFN-α also synergistically enhanced IP-10 response. Methylprednisolone showed only a partial inhibitory effect on this chemokine response. Our findings strongly suggest that both the H5N1 virus and the locally produced antiviral cytokines; IFN-α and TNF-α may have an important role in inducing IP-10 hyperresponse, leading to inflammatory damage in infected lung.

Hepatocellular MxA protein expression supports the differentiation of recurrent hepatitis C disease from acute cellular rejection after liver transplantation

Differentiation of recurrent hepatitis C virus (HCV) disease from acute cellular rejection (ACR) following liver transplantation can be difficult. Previously, we have found that MxA protein, a specific and sensitive marker for type 1 interferon production, is strongly expressed in chronic HCV disease. Here, we investigate MxA expression as a marker for recurrent HCV disease in the livers of 14 adult HCV patients who underwent liver transplantation. Serial liver biopsies available for 12 of these patients were stained for MxA protein and scored using a semi-quantitative approach. Hepatocellular MxA protein levels were significantly up-regulated (p = 0.025) in recurrent HCV disease in comparison to ACR. In biopsies that showed histological changes consistent with recurrent HCV disease, strong hepatocellular MxA staining was present in 14/18 (78%). In the liver biopsies with histological evidence of ACR, strong MxA hepatocellular staining was present in only three of 10 (30%). Thus, assessment of hepatocellular MxA protein expression can contribute to the differential diagnosis of ACR and recurrent HCV disease following liver transplantation. In conclusion, analysis of intrahepatic MxA levels has the potential to reduce the inappropriate use with high-dose pulsing of steroids post-operatively.

MxA expression as marker for assessing the therapeutic response in HCV genotype 4 Egyptian patients

The prevalence of hepatitis C virus (HCV) infection varies across the world, with the highest number of infections reported in Egypt. Expression of the MxA gene has been found to be a reliable and sensitive marker for the induction of endogenous type I interferons (IFNs) during viral infections. This study examined the correlation of gene expression of MxA with the response to treatment with pegylated-IFN-alfa2b and ribavirin. Fifty patients with type 4 HCV and 20 healthy volunteers as controls were enrolled in a prospective study designed with strict inclusion criteria to nullify the effect of confounding variables and further minimize selection bias. Quantification of HCV-RNA and MxA gene by real-time PCR was performed for every patient, and quantification of MxA gene was performed for controls. There was a statistically significant difference between patients and control group as regards the quantity of MxA gene expression (P < 0.05) (Mann-Whitney test) (P = 0.004). There was a statistically significant difference between responders and nonresponders (P < 0.05): responders showed a higher percentage of cases with initial MxA <2(6) (P < 0.05). We conclude that MxA protein expression is a sensitive biological marker for ongoing virus replication and presence of type 1 IFN. These results highlight the importance of the detection of MxA expression at the start of therapy as a factor for assessing the likelihood of HCV genotype 4 patients to achieving a sustained virological response to treatment with IFN-α2 in combination with ribavirin.

Detection of myxovirus resistance protein A in lichen planus lesions and its relationship to hepatitis C virus

Lichen planus (LP) is an inflammatory disease of the skin and oral mucosa. Studies suggested that type I interferons (IFNs) could play an important role in the cytotoxic inflammation in LP. Type I IFNs stimulate the production of several IFN-induced proteins including myxovirus resistance protein A (MxA protein). The association of LP and chronic hepatitis C is well established, with variable prevalence rates among different populations. Many authors have considered hepatitis C virus (HCV) as a possible antigen for inducing cytotoxic immune response in LP. To investigate the role of type I IFNs in LP through the detection of MxA protein, and to compare the expression of MxA protein between HCV-positive and HCV-negative patients with LP in an attempt to clarify the role of HCV in the pathogenesis of LP. The study included 33 skin biopsies from patients with LP and 10 control biopsies. MxA mRNA was detected by reverse transcription-polymerase chain reaction. HCV-specific antibodies were detected in patient sera by enzyme-linked immunosorbent assay. Our analysis revealed a significantly higher level of MxA protein in all the LP skin biopsies compared with controls. The expression was significantly higher in HCV-positive patients than in HCV-negative patients. Type I IFNs play a role in the pathogenesis of LP, and HCV could induce LP through increasing the production of type I IFNs.

Expression of the class I interferon‐related MxA protein in temporal arteries in polymyalgia rheumatica and temporal arteritis

Objective: The aim of this study was to assess the expression of the interferon type I (IFN‐I)‐associated MxA protein in polymyalgia rheumatica (PMR) and temporal arteritis (TA).Methods: Non‐inflamed temporal artery biopsies from 11 PMR patients were compared with biopsies from 13 patients given other diagnoses. Coded sections were screened immunocytochemically for MxA protein, CD83, CD68, CD3, and S100 protein. Inflamed temporal artery biopsies from four patients with TA were also investigated.Results: Focal MxA expression was seen in non‐inflamed arteries, more frequently in PMR than in controls (p = 0.0124). MxA expression was also more common in adventitial dendritic cells (DCs) in PMR (p = 0.0124). Activated adventitial DCs were detected in PMR. Focal MxA expression in the inflamed biopsies from the patients with TA was not related spatially to the inflammation.Conclusions: The expression of MxA protein in arteries from patients with PMR and TA shows that non‐inflamed and inflamed vessel walls are influenced by IFN‐I. Further studies are required to elucidate whether IFN‐I plays a role in the initiation of PMR and/or TA, serving as a link between the innate and the adaptive immune responses, as in some other autoimmune disorders.

Common variable immunodeficiency (CVID) and MxA-protein expression in blood leucocytes.

The underlying immunopathogenic mechanism of CVID has been suspected to involve a chronic viral infection or an autoimmune condition. However, formal proof of viral infection is lacking. Measurement of MxA-protein in leucocyte lysates is a sensitive test for evaluating the activation of the host's interferon system. Both viral infections and autoimmune diseases such as systemic lupus erythematosus (SLE) strongly induce MxA-protein in peripheral leucocytes. We therefore examined 15 patients with longlasting hypogammaglobulinaemia for MxA-protein induction in vivo: 13 patients suffered from CVID, one from hyper-IgM syndrome, and one patient had chronic B lymphocytic leukaemia associated with immunoglobulin deficiency and chronic papilloma virus infection (condylomata accuminata). Only the latter patient exhibited a strong MxA-protein expression; two CVID patients were borderline positive, and the remaining 12 patients including the hyper-IgM syndrome were MxA-protein-negative. There was no relationship between MxA expression and low CD4/CD8 ratios or increased CD8/CD57+ T cell counts, although both conditions are often observed in CVID as well as in chronic viral infections. When exposed in vitro to interferon-alpha (IFN-alpha), peripheral blood leucocytes of four MxA-negative patients were capable of producing normal amounts of MxA-protein. Taken together, these results argue against a viral or autoimmune pathogenesis of CVID.

Neutralizing antibodies to biological therapies

It is almost a given that when a foreign biologically active molecule is injected into humans it will incite immune reactions leading to antibody formation against the molecule, which at high levels of titer and affinity can interfere with its pharmacokinetic properties and block the molecule from binding to its receptor, rendering it biologically inert. Though the degree of foreign-ness tends to be the strongest driving force for the production of antibodies, the mode of administration (sc, IM, IV), dose, and frequency may also impact their development. The development of monoclonal antibody (MAb) technology has allowed for the production of very specific target-directed immunotherapies that have revolutionized the treatment of autoimmune diseases in particular, such as rheumatoid arthritis, systemic lupus erythematosus, and even multiple sclerosis (MS). Though technology has also made it possible to “humanize” the MAb as much as possible, by nature the MAb must be at least a little foreign, since the specific part of the antibody that binds to the human receptor (referred to as the idiotype) is most likely generated in a different species (figure). Assessing what impact anti-drug neutralizing antibodies (NAbs) have on drug efficacy requires attention to two different categories of drug effect: that on drug measures, such as pharmacokinetics and bioactivity, and the effect on specific disease outcome measures. Drug measures in some cases can be readily quantitated (e.g., natalizumab levels) or inferred from bioactivity measures (e.g., MxA protein expression in response to interferon-β) (IFNβ). Presuming that during the development of these agents, both the sustainable levels and their subsequent bioactivity have been optimized, neurologists assume that once administered, agents are fully capable of maximizing their effects on disease measures, which can be assessed in clinical trials. However, anti-drug antibodies can profoundly affect these measures, …

MxA-independent inhibition of Hantaan virus replication induced by type I and type II interferon in vitro

Interferons (IFN) induce an antiviral state against Hantaan virus (HTNV) but the mechanisms responsible for inhibition are unclear. The IFN-inducible MxA is discussed to be important for control of infections with hantaviruses. To characterize the role of endogenous MxA, the inhibition of HTNV induced by type I and type II IFNs was compared in Vero and A549 cells. IFNα and IFNγ reduced production of infectious virions, viral RNA, and nucleocapsid protein with the same efficiency, although expression of MxA protein was detectable only in IFNα-treated A549 cells. Furthermore, knock down of MxA expression did not impair IFNα-induced inhibition. Thus, inhibition of HTNV induced by type I and type II IFNs did not dependent on expression of endogenous MxA. Taken together, these data suggest that MxA endogenously expressed in response to type I or type II IFNs does not play a pivotal role for the antiviral state against HTNV and that there is more than one mechanism by which cellular defences block hantavirus replication.

Interferon receptor expression in multiple sclerosis patients

To determine the gene expression of IFNAR1, IFNAR2 and MxA protein and the association with IFNβ treatment response in MS patients. MS patients treated with IFNβ had a significant decrease in IFNAR1 and IFNAR2 expression, and a significant increase in MxA compared to non-treated patients and healthy controls. Also, those patients who had a good response to treatment had a significant decrease in IFNAR1 and IFNAR2 expression compared to non-responders, non-treated patients and healthy controls. IFNβ influences the expression of its receptors, and is greater in patients who respond to IFNβ treatment. This down-regulation could be indicative of the response to IFNβ.

Theophylline metabolism in acute asthma with MxA-indicated viral infection

Although viral infection might alter theophylline metabolism in acute asthma, there are some difficulties in detecting infection due to various kinds of viruses in a clinical setting. To evaluate the usefulness of assessment of MxA protein in acute asthma exacerbated by viral infection, MxA protein expression in lymphocytes was assayed by flow cytometric analysis in whole peripheral blood in 21 children (aged 0-6 years) receiving continuous theophylline infusion for management of asthma attack. Serum theophylline levels were measured at 24 and 72 h after initiating theophylline infusion. At the beginning of theophylline infusion, 11 children had increased expression of MxA protein, indicating viral infected states. After 24 h continuous infusion, there were no differences in theophylline levels between MxA-negative and MxA-positive groups. After 72 h infusion, the mean theophylline level of MxA-positive children was significantly higher than that of MxA-negative children (9.7 +/- 2.2 microg/mL vs 7.3 +/- 1.6 microg/mL). The ratio of theophylline clearance at 72 h to that at 24 h in the MxA-positive group was significantly lower than that of the MxA-negative group (1.1 +/- 0.2 vs 1.4 +/- 0.1). Viral infection appeared to affect theophylline metabolism. Flow cytometric assay of lymphoid MxA protein expression in whole blood is an easy and useful method of evaluating viral infection in acute asthma exacerbation.

EXPRESSION OF MxA PROTEIN IN BLOOD LYMPHOCYTES OF CHILDREN RECEIVING ANTICANCER CHEMOTHERAPY

The aim of the study was to evaluate whether IFN-α/β-inducible MxA protein expression in children receiving anticancer treatment can be used as an indicator for virus infections during the febrile episodes. Twenty-six children with mainly hematological malignancies entered the study. Children with laboratory-confirmed virus infections had clearly elevated MxA protein levels compared to their counterparts with bacterial or unknown etiology. MxA protein expression increased moderately following the administration of cytostatic agents, even though these children had no clinical signs of infection.

Expression of the interferon-alpha/beta-inducible bovine Mx1 dynamin interferes with replication of rabies virus

Rabies is a fatal anthropozoonotic viral infection of the central nervous system that remains a serious public health problem in many countries. As several animal cases of spontaneous survival to infection were reported and because type 1 interferons were shown to protect against the virus, it was suggested that innate resistance mechanisms exist. Among the antiviral proteins that are synthesized in response to interferon-alpha/beta stimulation, Mx proteins from several species are long known to block the replication of vesicular stomatitis virus (VSV). As both VSV and rabies virus belongs to the Rhabdoviridae family, this study was started with the aim to establish whether the anti-VSV activity of a mammalian Mx protein could be extended to rabies virus. This question was addressed by inoculating the virus onto a bovine Mx1 or human MxA-expressing Vero cell clone. Plaque formation was unambiguously blocked, and viral yields were reduced 100- to 1000-fold by bovine Mx1 expression for both SAG2 and SADB19 viral strains. In opposition, only SAG2 strain could be inhibited by the expression of human MxA protein. The effect of both proteins expression was then evaluated at the viral protein expression level. Again, boMx1 was able to repress protein expression in both strain, whereas only SAG2 proteins were inhibited in human MxA-expressing cells. These results suggest that protection conferred by interferon-alpha/beta against rabies could be, at least partially, attributable to the Mx pathway. Alternatively, bovine Mx1 could be unique in its ability to repress rabies virus which, if confirmed in vivo, would open an avenue for the development of new antirabies therapeutic strategies.

Hepatic Gene Expression Discriminates Responders and Nonresponders in Treatment of Chronic Hepatitis C Viral Infection

Pegylated interferon (IFN)-alpha plus ribavirin is the most effective treatment of chronic hepatitis C but has unpleasant side effects and high costs. A large proportion of patients do not respond to therapy for reasons that are unclear. We used gene expression profiling to investigate the molecular basis for treatment failure. Expression profiling was performed on percutaneous needle liver biopsy specimens taken before therapy. Gene expression levels were compared among 15 nonresponder, 16 responder, and 20 normal liver biopsy specimens. Differential gene expression was confirmed using real-time polymerase chain reaction. We identified 18 genes whose expression differed significantly between all responders and all nonresponders (P < .005). Many of these 18 genes are IFN sensitive and 2 (ISG15/USP18) are linked in a novel IFN-regulatory pathway, suggesting a possible rationale for treatment resistance. Using a number of independent classifier analyses, an 8-gene subset accurately predicted treatment response for 30 of 31 patients. The classifier analyses were applicable to patients with genotype 1 infection and were not correlated with viral load, disease activity, or fibrosis. Hepatic gene expression profiling identified consistent differences in patients who subsequently fail treatment with pegylated IFN-alpha plus ribavirin: up-regulation of a specific set of IFN-responsive genes predicts nonresponse to exogenous therapy. These data may be of use in predicting clinical responses to treatment.

Andes virus stimulates interferon‐inducible MxA protein expression in endothelial cells

MxA is a cellular protein activated in cells treated with type I interferons. MxA protein is a member of the dynamin superfamily of large guanosine triphosphatases. A unique property of Mx1 GTPases is their antiviral activity against a wide range of RNA viruses. Replication of several hantavirus strains is inhibited in cells constitutively expressing MxA protein. We have found that Andes virus (ANDV) infection up regulates transcription of MxA RNA and expression of MxA protein in human endothelial cells in vitro. Activation of MxA gene expression requires virus replication. Up-regulation of MxA gene expression in hantavirus infected cells varies depending on the cell type. The degree of activation of MxA gene expression is inversely correlated with the efficiency of hantavirus replication. Additionally, MxA protein is co-localized with hantavirus nucleocapsid protein in infected cell. Our data suggest that MxA by interacting with the virus nucleocapsid protein inhibits production of new infectious virus particles.