Quantification of Bevacizumab Activity Following Treatment of Patients With Ovarian Cancer or Glioblastoma

Highly sensitive reporter-gene assays have been developed that allow both the direct vascular endothelial growth factor (VEGF) neutralizing activity of bevacizumab and the ability of bevacizumab to activate antibody dependent cellular cytotoxicity (ADCC) to be quantified rapidly and in a highly specific manner. The use of these assays has shown that in 46 patients with ovarian cancer following four cycle of bevacizumab treatment, and in longitudinal samples from the two patients that respond to bevacizumab therapy from a small cohort of patients with glioblastoma, that there is a reasonably good correlation between bevacizumab drug levels determined by ELISA and bevacizumab activity, determined using either the VEGF-responsive reporter gene, or the ADCC assays. One of the two primary non-responders with glioblastoma exhibited high levels of ADCC activity suggesting reduced bevacizumab Fc engagement in vivo in contrast to the other primary non-responder, and the two secondary non-responders with a decreasing bevacizumab PK profile, determined by ELISA that exhibited low to undetectable ADCC activity. Drug levels were consistently higher than bevacizumab activity determined using the reporter gene assay in serial samples from one of the secondary non-responders and lower in some samples from the other secondary non-responder and ADCC activity was markedly lower in all samples from these patients suggesting that bevacizumab activity may be partially neutralized by anti-drug neutralizing antibodies (NAbs). These results suggest that ADCC activity may be correlated with the ability of some patients to respond to treatment with bevacizumab while the use of the VEGF-responsive reporter-gene assay may allow the appearance of anti-bevacizumab NAbs to be used as a surrogate maker of treatment failure prior to the clinical signs of disease progression.

SCRG1, a Potential Marker of Autophagy in TSE

The Scrg1 gene was initially discovered as one of the genes upregulated in transmissible spongiform encephalopathies (TSE). Scrg1 encodes a highly conserved, cysteine-rich protein expressed principally in the central nervous system. The protein is targeted to the Golgi apparatus and large dense-core vesicles/secretory granules in neurons. We have recently shown that the Scrg1 protein is widely induced in neurons of scrapie-infected mice, suggesting that Scrg1 is involved in the host response to stress and/or the death of neurons. At the ultrastructural level, Scrg1 is associated with dictyosomes of the Golgi apparatus and autophagic vacuoles of degenerative neurons. It is well known that apoptosis plays a major role in the events leading to neuronal cell death in TSE. However, autophagy was identified in experimentally induced scrapie a long time ago and was recently reevaluated as a possible cell death program in prion diseases. The consistent association of Scrg1 with autophagic structures typical of scrapie is in agreement with the recruitment of Golgi-specific proteins in this degradation process and we suggest that Scrg1 might be used as a specific probe to identify neuronal autophagy in TSE.

Immunogenicity and other problems associated with the use of biopharmaceuticals

Biopharmaceuticals are used widely for the treatment of cancer, chronic viral hepatitis, inflammatory, and autoimmune diseases. Biopharmaceuticals such as interferons are well tolerated for the most part with the most common adverse events observed being 'flu-like' symptoms that resolve rapidly after initial treatment. Prolonged treatment is associated, however, with more serious adverse events including leucopenia, thrombocytopenia, and neuropsychiatric effects, which may necessitate dose reduction or even cessation of treatment in some patients. Recombinant growth factors, such as erythropoietin (EPO), granulocyte colony-stimulating factor, or granulocyte macrophage colony-stimulating factor, are for the most part well tolerated, although severe complications have been reported in patients with cancer or chronic kidney disease treated with EPO. Similarly, treatment of patients with cancer with high doses of interleukin-2 is associated with significant toxicity. Treatment of chronic inflammatory diseases, such as rheumatoid arthritis, psoriasis, and Crohn's disease, with antitumor necrosis factor-alpha monoclonal antibodies is associated with an increased risk of granulomatous infections and, in particular, tuberculosis. The monoclonal antibody, natalizumab, that targets alpha4 integrins is effective in the treatment of multiple sclerosis but is associated with the activation of JC virus and development of progressive multifocal leukoencephalopathy. Repeated administration of recombinant proteins can cause a break in immune tolerance in some patients resulting in the production of a polyclonal antibody response that can adversely affect pharmacokinetics and clinical response. In addition, neutralizing antibodies that cross react with nonredundant essential proteins such as EPO can cause severe autoimmune reactions.

Overcoming immunogenicity associated with the use of biopharmaceuticals

The safety and efficacy of biopharmaceuticals can be severely impaired by their immunogenicity. A risk-based strategy should be used to assess immunogenicity on a case-by-case basis using standardized methods to correlate anti-drug antibody levels with clinical outcome. In silico and in vitro techniques allow putative T-cell epitopes to be identified and eliminated in candidate molecules while maintaining structure and function. Putative T-cell epitopes can be studied in the context of the HLA allotypes representative of the target population in vitro and in transgenic mice that express human HLA genes. Mice immune tolerant to human proteins allow the study of the effect of factors such as aggregation on the loss of immune tolerance. However, significant challenges remain in order to be able predict the immunogenicity of a therapeutic protein in a particular individual.

Reporter gene assay for the quantification of the activity and neutralizing antibody response to TNFα antagonists

A cell-based assay has been developed for the quantification of the activity of TNFα antagonists based on human erythroleukemic K562 cells transfected with a NFκB regulated firefly luciferase reporter-gene construct. Both drug activity and anti-drug neutralizing antibodies can be quantified with a high degree of precision within 2h, and without interference from cytokines and other factors known to activate NFκB. The assay cells also contain the Renilla luciferase reporter gene under the control of a constitutive promoter that allows TNFα-induced firefly luciferase activity to be normalized relative to Renilla luciferase expression. Thus, results are independent of cell number or differences in cell viability, resulting in intra and inter assay coefficients of variation of 10% or less. Normalization of results relative to the expression of an internal standard also provides a means for correcting for serum matrix effects and allows residual drug levels or anti-drug neutralizing antibodies to be quantified even in serum samples with a relatively high degree of cytotoxicity.

One-step assay for quantification of neutralizing antibodies to biopharmaceuticals

Assessment of immunogenicity is an important part of biopharmaceutical drug safety evaluation and a prerequisite for the development of less immunogenic and safer biopharmaceuticals since anti-drug antibodies can impair the activity and compromise the safety of biopharmaceuticals. Although regulatory authorities recommend cell-based assays for detection of neutralizing antibodies (NAbs), such assays are difficult to standardize, and ill adapted to high-throughput analysis. These limitations have been overcome by the development of a unique one-step cell-based assay that allows both drug activity and drug NAbs to be quantified rapidly and with a high degree of precision simply be adding reporter cells to a sample. The reporter cells have been engineered to express firefly luciferase (FL) under the control of a drug-responsive promoter, and to express the drug of interest, the production of which is normalized relative to the expression of Renilla luciferase (RL) transcribed from a common doxycycline-inducible promoter. Residual drug levels present in a sample are first quantified by determination of FL expression, autocrine drug synthesis is then induced, and NAb activity is quantified from the difference in the ratio of FL/RL expression in the presence or absence of the sample. Since assay results are normalized relative to the expression of an internal standard, results are independent of cell number or differences in cell viability thus affording a high degree of assay precision and reducing serum matrix effects to a minimum. This unique assay platform is ideally suited for high-throughput analysis, is applicable to most biopharmaceuticals, and will facilitate standardization and comparison of immunogenicity data. The performance of the one-step assay is illustrated for interferon alpha2 (IFNalpha2) used widely to treated chronic hepatitis C (HCV) infection and neoplastic disease.

Cryptosporidium parvum infection rapidly induces a protective innate immune response involving type I interferon

Type II interferon (IFN), IFN-gamma, is important in innate immunity to the intestinal protozoan parasite Cryptosporidium species, which infects epithelial cells (enterocytes). This investigation is, to our knowledge, the first to characterize the role of type I IFN in innate immunity to this parasite. Pretreatment of human or murine enterocyte cell lines with IFN-alpha/beta inhibited parasite development, and we identified that a key mechanism of cytokine action was to prevent parasite invasion of enterocytes. IFN-alpha/beta was rapidly expressed by infected murine enterocytes and also by bone marrow-derived dendritic cells that were exposed to live parasites. Treatment of neonatal severe combined immunodeficiency mice with anti-IFN-alpha/beta neutralizing antibodies before infection increased oocyst reproduction, as measured at the peak of infection, and parasite numbers in gut epithelium were also increased 2 days after infection. The latter observation correlated with strong intestinal expression of both IFN-alpha and IFN-beta messenger RNA within 24 h after infection. Treatment with anti-IFN-alpha/beta, however, did not reduce early expression of IFN-gamma. These findings identify a novel early innate host response against Cryptosporidium parvum involving IFN-alpha/beta.

Treatment with azathioprine and cyclic methylprednisolone has little or no effect on bioactivity in anti-interferon beta antibody-positive patients with multiple sclerosis

Background

It is unknown whether immunosuppression of patients who have developed interferon-β (IFN-β) neutralizing antibodies (NAbs) hastens disappearance of NAbs in the blood.

Objective

We wanted to test whether immunosuppression with cyclic methylprednisolone (MP) in combination with azathioprine (AZA) for 6 months accelerates recovery of IFN-β bioactivity in patients with multiple sclerosis (MS) with abolished in-vivo myxovirus resistance protein A (MxA) mRNA response to IFN-β.

Methods

We included 13 patients with MS with NAbs and a low IFN-β bioavailability detected by the MxA-mRNA response in a descriptive, non-randomized trial. Another 14 NAb-positive patients with a low MxA-mRNA response served as controls. The primary outcome was the fraction of patients who regained an MxA-mRNA response to IFN-β. NAbs were measured by means of a clinically validated cytopathic effect assay and a new reporter gene assay. The in-vivo MxA-mRNA response was measured by real-time polymerase chain reaction.

Results

A total of 11 patients in the treatment group completed the trial. In all, two of these 11 patients regained an in-vivo MxA-mRNA response as compared to one of 14 patients in the control group.

Conclusion

Treatment with AZA and cyclic MP for 6 months has little or no effect on IFN-β bioactivity in NAb-positive patients with MS.

Targeting poly(I:C) to the TLR3-independent pathway boosts effector CD8 T cell differentiation through IFN-alpha/beta

Poly(I:C) is an adjuvant used for antitumor treatment and vaccines because of its prominent effects on CD8 T cells and NK cells. Poly(I:C) binds TLR3 and this interaction is thought to be central for driving cell-mediated immune responses. We investigated the importance of TLR3 in poly(I:C)-mediated endogenous CD8 T cell responses using the pathogenic T cell stimulant Staphylococcus aureus enterotoxin A. While the responsive CD8 T cells expanded comparably in both wild-type and TLR3(-/-) mice, differentiation of effector CD8 T cells was enhanced by poly(I:C) in the TLR3(-/-) mice. A higher percentage of Ag-specific CD8 T cells became IFN-gamma and TNF-alpha producers in the absence of TLR3 signaling. Consistent with this boosted response was the observation that TLR3-deficient cells synthesized less IL-10 compared with TLR3-sufficient cells in response to poly(I:C). Ultimately, however, the fundamental mechanism of CD8 effector T cell differentiation through the TLR3-independent pathway was shown to be completely IFN-alpha/beta-dependent. Administration of IFN-alpha/beta-neutralizing Abs abolished the poly(I:C) effects in TLR3(-/-) mice. These findings reveal specific roles of how dsRNA receptors shape CD8 T cell responses, which should be considered as poly(I:C) is authenticated as a therapeutic adjuvant used in vaccines.

Adjuvant activity of type I interferons

Type I interferons (IFNs) produced primarily by plasmacytoid dendritic cells (pDCs) as part of the innate immune response to infectious agents induce the maturation of myeloid DCs and enhance antigen presentation. Type I IFNs also enhance apoptosis of virus-infected cells, stimulate cross priming and enhanced presentation of viral peptides. Type I IFNs are powerful polyclonal B-cell activators that induce a strong primary humoral immune response characterized by isotype switching and protection against virus challenge. Type I IFNs stimulate an IgG2a antibody response characteristic of Th1 immunity when ad-mixed with influenza virus vaccine and injected intramuscurarly (i.m.) or administered intranasally. The adjuvant activity of type I IFNs has been shown to involve direct effects of IFN on B-cells, effects on T-cells, as well as effects on antigen presentation. Oromucosal administration of type I IFNs concomitantly with i.m. injection of vaccine alone can also enhance the antibody response to influenza vaccination by enhancing trafficking of antigen-presenting cells towards the site of vaccination. Recombinant IFNs are potent adjuvants that may find application in both parenterally and mucosally administered vaccines.

Targeting the effector site with IFN-alphabeta-inducing TLR ligands reactivates tumor-resident CD8 T cell responses to eradicate established solid tumors

Effective antitumor CD8 T cell responses may be activated by directly targeting the innate immune system within tumors. We investigated this response by injecting a range of TLR agonists into established tumors using a mouse model of malignant mesothelioma stably transduced with the hemagglutinin (HA) gene as a marker Ag (AB1-HA). Persistent delivery of the dsRNA mimetic poly(I:C) into established AB1-HA tumors resulted in complete tumor resolution in 40% of mice, with the remaining mice also showing a significant delay in tumor progression. Experiments in athymic nude mice along with CD8 depletion and IFN-alphabeta blocking studies revealed that tumor resolution required both CD8 T cells and type I IFN induction, and was associated with local changes in MHC class I expression. Surprisingly, however, tumor resolution was not associated with systemic dissemination or tumor infiltration of effector CD8 T cells. Instead, the antitumor response was critically dependent on the reactivation of tumor-resident CD8 T cell responses. These studies suggest that, once reactivated, pre-existing local CD8 T cell responses are sufficient to resolve established tumors and that in situ type I IFN is a determining factor.

Type I interferon subtypes produced by human peripheral mononuclear cells from one normal donor stimulated by viral and non-viral inducing factors

Through the activation of Toll-like receptors (TLRs) or cytosolic RNA helicases, a large number of pathogenic or synthetic components can induce the transcription of genes coding for type I interferons (IFNs). This family of related cytokines includes notably, a single IFN-beta protein and 13 different IFN-alpha subtypes, whose biological activities are probably not the same. The aim of this study was to characterize the type I IFN subtypes produced in vitro by human peripheral blood mononuclear cells (PBMCs) in response to specific inducers. Thus, PBMCs obtained from a single donor, were exposed to various agents including Sendai virus, Herpes simplex virus-1 (HSV-1), poliovirus-IgG complexes and serum from a patient with systemic lupus erythematosus (SLE). Six hours later, mRNA was extracted and amplified by RT-PCR using primers which recognize IFN-B mRNA and the different IFN-A mRNA subtypes. IFN-A subtypes were identified by cloning and sequencing the amplification product. Antiviral activity was assayed in supernatant at 18 hours. Human PBMCs were found to express constitutively type I IFNs mRNA. Antiviral activity and expression of IFN-A and IFN-B mRNA increased with each inducing agent. Although almost all the IFN-A subtypes were detected, their relative abundance appeared to be dependent upon the inducing agent. Incubation of PBMCs with a neutralizing monoclonal antibody directed against the type I IFN receptor (IFNAR) did not affect the level of antiviral activity in the supernatant of induced PBMCs. Our results suggest that the level of IFN-alpha expressed by PBMCs cells is independent of IFNAR feedback signalling and that the nature of the inducing agent modifies the pattern of IFN-A subtypes preferentially expressed by these cells.

Infection by ME7 prion is not modified in transgenic mice expressing the yeast chaperone Hsp104 in neurons

The Hsp104 chaperone induces thermo-tolerance in yeast and rescues proteins trapped in aggregates. In this study, we showed that xenogenic expression of Hsp104 dramatically increased the viability of the neuronal mouse CAD cell line after exposure to heat shock. These results indicate that the Hsp104 protein confers thermo-resistance to mammalian neuronal cells, the canonical property of Hsp104 in yeast. Hsp104 also determines the prion state of prion-like proteins in yeast and to investigate whether Hsp104 expression may modify mammalian prion infection in vivo, transgenic mice with specific expression of Hsp104 in neurons were generated. Mice develop and reproduce normally, they show no detectable physical defect and may constitute valuable model for the study of aggregation-prone neuropathological disorders. Hsp104 transgenic and control littermates were infected intracerebrally with the ME7 strain of scrapie. No differences in the incubation time of the disease or in PrP(Sc) accumulation were observed between transgenic and control mice. These results suggest that the heat-shock protein Hsp104 is not efficient to modulate the multiplication of mammalian prions and/or to counteract neurodegeneration in the brain of scrapie-infected mice.

Single-stranded RNA viruses inactivate the transcriptional activity of p53 but induce NOXA-dependent apoptosis via post-translational modifications of IRF-1, IRF-3 and CREB

To characterize the mechanisms underlying apoptosis induced by viral infection, transcriptional activation of genes encoding members of the 'BH3-only' family of proteins was analysed during the course of virus infection. Among these genes, only NOXA is transcriptionally activated by vesicular stomatitis virus (VSV), sendai virus (SV), measles virus, herpes simplex virus, or dsRNA and required for efficient apoptosis of cells. Transcriptional activation of NOXA by VSV or SV is independent of p53, but requires the presence of interferon regulatory factor 1 (IRF-1), IRF-3 and cAMP-responsive element binding protein (CREB). Binding to and transactivation of the NOXA promoter by each of these transcription factors is governed by post-translational modification involving different pathways for each factor. Thus, SV infection activates IRF-3 and CREB by phosphorylation triggered by Toll like receptor 3 signalling, and a pathway involving calcium-independent phopholipase A2, respectively. In addition transactivation induced by IRF-1 during viral infection correlates with a 10 kDa increase in its molecular weight, suggesting a covalent linkage with a previously unknown regulatory polypeptide.

Adjuvant activity of interferon alpha: mechanism(s) of action

Interferon alpha (IFNalpha), produced primarily by plasmacytoid dendritic cells as part of the innate immune response to infectious agents, is a powerful polyclonal B-cell activator that induces a strong primary humoral immune response characterized by isotype switching and protection against virus challenge. IFNalpha has also been shown to stimulate an IgG2a antibody response characteristic of Th1 immunity when ad-mixed with influenza virus vaccine. The use of transgenic mice expressing a green fluorescent protein reporter gene regulated by an IFN responsive element has shown that IFN-activated cells are present in the peripheral circulation of influenza vaccinated mice as early as 4 h after initiation of IFNalpha treatment and that the principal cell populations activated by IFN treatment included B220 (-) Ly6c (-), CD11c (high), CD11b (high), CD8 (+) cells, and B220 (high), Ly6c (high), CD11c (low), CD11b (-), CD4 (+), CD19 (-) cells. The effect of IFNalpha on the antibody response to influenza vaccination was shown to be dependent upon the route of administration. Differential display analysis showed that numerous IFN responsive genes were induced in the lymphoid tissue of IFN treated animals together with a number of genes not previously shown to be induced by IFNalpha including Crg2 and other chemokines, proteases associated with antigen processing, and genes involved in lymphocyte activation, apoptosis, and protein degradation. Together these results may explain in part the mechanism(s) of the adjuvant activity of IFNalpha.

Scrg1 is induced in TSE and brain injuries, and associated with autophagy

We have previously identified Scrg1, a gene with increased cerebral mRNA levels in transmissible spongiform encephalopathies (TSE) such as scrapie, bovine spongiform encephalopathy and Creutzfeldt-Jakob disease. In this study, Scrg1-immunoreactive cells, essentially neurons, were shown to be widely distributed throughout the brain of scrapie-infected mice, while only rare and weakly immunoreactive cells could be detected in the brain of non-infected normal mice. Induction of the protein was confirmed by Western blot analysis. At the ultrastructural level, Scrg1 protein was associated with dictyosomes of the Golgi apparatus and autophagic vacuoles in the central neurons of the scrapie-infected mice. These results suggested a role for Scrg1 in the pathological changes observed in TSE. We have generated transgenic mice specifically expressing Scrg1 in neurons. No significant differences in the time course of the disease were detected between transgenic and non-transgenic mice infected with scrapie prions. However, tight association of Scrg1 with autophagic vacuoles was again observed in brain neurons of infected transgenic mice. High levels of the protein were also detected in degenerating Purkinje cells of Ngsk Prnp 0/0 mice overexpressing the Prnd gene coding for doppel, a neurotoxic paralogue of the prion protein. Furthermore, induction of Scrg1 protein was observed in the brain of mice injured by canine distemper virus or gold thioglucose treatment. Taken together, our results indicate that Scrg1 is associated with neurodegenerative processes in TSE, but is not directly linked to dysregulation of prion protein.

Interferons α and γ induce p53-dependent and p53-independent apoptosis, respectively

Type I interferon (IFN) enhances the transcription of the tumor suppressor gene p53. To elucidate the molecular mechanism mediating IFN-induced apoptosis, we analysed programmed cell death in response to type I (IFNalpha) or type II (IFNgamma) treatment in relation to p53 status. In two cell lines (MCF-7, SKNSH), IFNalpha, but not IFNgamma, enhanced apoptosis in a p53-dependent manner. Furthermore, only IFNalpha upregulated p53 as well as p53 target genes (Noxa, Mdm2 and CD95). The apoptotic response to IFNalpha decreased in the presence of ZB4, an anti-CD95 antibody, suggesting that CD95 is involved in this process. When p53 was inactivated by the E6 viral protein or the expression of a p53 mutant, IFNalpha-induced apoptosis and p53 target genes upregulation were abrogated. Altogether these results demonstrate that p53 plays a pivotal role in the IFNalpha-induced apoptotic response. IFNalpha-induced PML was unable to recruit p53 into nuclear bodies and its downregulation by siRNA did not alter CD95 expression. In contrast, IFNgamma-induced apoptosis is p53-independent. CD95 and IFN-regulatory factor 1 (IRF1) are directly upregulated by this cytokine. Apoptotic response to IFNgamma is decreased in the presence of ZB4 and strongly diminished by IRF1 siRNA, implicating both CD95 and IRF1 in IFNgamma-induced apoptotic response. Taken together, these results show that in two different cell lines, IFNalpha and IFNgamma, induce p53-dependent -independent apoptosis, respectively.

An Essential Role for IFN-α in the Overexpression of Fas Ligand on MRL/lpr Lymphocytes and on Their Spontaneous Fas-Mediated Cytotoxic Potential

Lymphocytes from aged autoimmune MRL/lpr mice overexpress Fas ligand (FasL), and are cytotoxic against Fas+ target cells. This cytotoxic potential is only partly due to FasL, as wild-type MRL+/+ lymphocytes are not able to kill Fas+ targets after induction of FasL. In addition, serum levels of interferon-alpha (IFN-alpha) increase in parallel with the Fas-dependent cytotoxic potential of lymphocytes from MRL/lpr mice as they age. To understand the mechanisms underlying these observations, combined suppression subtractive hybridization (SSH) and RT-PCR were used to study differential gene expression in splenocytes from MRL/lpr mice compared with splenocytes from MRL+/+ mice. Twenty-two genes were upregulated transcriptionally in MRL/lpr splenocytes compared with their MRL+/+ counterparts. Furthermore, 9 of these genes were also upregulated after treatment of MRL/lpr splenocytes with IFN-alpha, and 4 were strongly downregulated. MRL/lpr lymphocytes were also found to be hyperresponsive to IFN-alpha. Thus, MRL/lpr lymphocytes overexpressed mRNA for the IFN-alpha receptor (IFNAR-1 and IFNAR-2) chains of the IFN-alpha/beta receptor and exhibited high endogenous levels of both Stat1 and phosphorylated Stat1 proteins. Lymphocytes from young MRL/lpr mice, with low Fas-dependent cytotoxic activity, were found to become highly cytotoxic against Fas+ targets after treatment with IFN-alpha. These data suggest that IFN-alpha plays an important role in the physiopathology of the systemic lupus erythematosus (SLE)-like syndrome that occurs in MRL/lpr mice.

Identification of Residues of the IFNAR1 Chain of the Type I Human Interferon Receptor Critical for Ligand Binding and Biological Activity

The antiviral and antiproliferative activities of human type I interferons (IFNs) are mediated by two transmembrane receptor subunits, IFNAR1 and IFNAR2. To elucidate the role of IFNAR1 in IFN binding and the establishment of biological activity, specific residues of IFNAR1 were mutated. Residues (62)FSSLKLNVY(70) of the S5-S6 loop of the N-terminal subdomain of IFNAR1 and tryptophan-129 of the second subdomain of IFNAR1 were shown to be crucial for IFN-alpha binding and signaling and establishment of biological activity. Mutagenesis of peptide (278)LRV in the third subdomain shows that these residues are critical for IFN-alpha-induced biological activity but not for ligand binding. These data, together with the sequence homology of IFNAR1 with cytokine receptors of known structure and the recently resolved NMR structure of IFNAR2, led to the establishment of a three-dimensional model of the human IFN-alpha/IFNAR1/IFNAR2 complex. This model predicts that following binding of IFN to IFNAR1 and IFNAR2 the receptor complex assumes a "closed form", in which the N-terminal domain of IFNAR1 acts as a lid, resulting in the activation of intracellular kinases. Differences in the primary sequence of individual IFN-alpha subtypes and resulting differences in binding affinity, duration of ligand/receptor association, or both would explain differences in intracellular signal intensities and biological activity observed for individual IFN-alpha subtypes.

Scrg1, a novel protein of the CNS is targeted to the large dense-core vesicles in neuronal cells

Scrapie responsive gene one (Scrg1) is a novel transcript discovered through identification of the genes associated with or responsible for the neurodegenerative changes observed in transmissible spongiform encephalopathies. Scrg1 mRNA is distributed principally in the central nervous system and the cDNA sequence predicts a small cysteine-rich protein 98 amino acids in length, with a N-terminal signal peptide. In this study, we have generated antibodies against the predicted protein and revealed expression of a predominant immunoreactive protein of 10 kDa in mouse brain by Western blot analysis. We have established CAD neuronal cell lines stably expressing Scrg1 to determine its subcellular localization. Several lines of evidence show that the protein is targeted to dense-core vesicles in these cells. (i) Scrg1 is detected by immunocytochemistry as very punctate signals especially in the Golgi apparatus and tips of neurites, suggesting a vesicular localization for the protein. Moreover, Scrg1 exhibits a high degree of colocalization with secretogranin II, a dense-core vesicle marker and a very limited colocalization with markers for small synaptic vesicles. (ii) Scrg1 immunoreactivity is associated with large secretory granules/dense-core vesicles, as indicated by immuno-electron microscopy. (iii) Scrg1 is enriched in fractions of sucrose density gradient where synaptotagmin V, a dense-core vesicle-associated protein, is also enriched. The characteristic punctate immunostaining of Scrg1 is observed in N2A cells transfected with Scrg1 and for the endogenous protein in cultured primary neurons, attesting to the generality of the observations. Our findings strongly suggest that Scrg1 is associated with the secretory pathway of neuronal cells.

Do retroviruses preferentially integrate within highly plastic regions of the human genome?

Whether retroviral integration is a phenomenon specific to properties of the surrounding genomic region is a widely debated question. In this paper we attempt to enlight the involvement of genomic regions prone to DNA double strand breaks in such process, as well as the more general concept of genome plasticity concerning repair, recombination, transposition events. While performing a differential display analysis of the promonocytic cell line U937 and clone U42 HIV infected counterpart, we found, out of about 15 highly dysregulated genes, expected according to our previous proteomic analysis, two dysregulated cellular transcripts that are shown in the present study to colocalize on band 22q11. The LB14 transcript maps within the DiGeorge critical region. Whereas the AG46 transcript encodes the immunoglobulin-lambda like polypeptide 1 (IGLL1) 4.7Mb apart from LB14. The 22q11 band is remarkable for its high plasticity involving DNA double strand breaks, that may lead to translocations, large deletions, and immunoglobulin rearrangements, frequently observed in this region. We suggest that provirus integration preferentially occurs in such genomic regions and that the subsequent insertional mutagenesis leads to the present observations. Finally, we stress out the possibility that the small size of chromosome 22 is associated with this physical property of the genome.

Oromucosal cytokine therapy: mechanism(s) of action

Oromucosal cytokine therapy allows large amounts of cytokines to be administered with improved outcome and without dose limiting toxicity. Orally administered cytokines exert their effects by a novel two pronged mechanism of action. Firstly, specific populations of immuno-competent effector cells are activated in the oral cavity and migrate to the site of virus replication. Secondly, chemokines produced in the lymphoid tissue of the oral cavity enter the peripheral circulation and redirect activated lymphocytes to eliminate virus infected cells. Oromucosal IFN therapy constitutes an alternative and improved means of therapy for diseases such as chronic viral hepatitis which are currently treated parenterally with IFN alpha. The oral route also has obvious advantages for ease of administration and improved patient compliance. Furthermore, the availability of a well tolerated form of IFN therapy will also allow Type I IFNs to be used for the treatment of diseases such as upper respiratory tract virus infections, for which parenteral IFN therapy is currently precluded due to unacceptable toxicity.

Direct signal transduction via functional interferon-alphabeta receptors in CD34+ hematopoietic stem cells

Affinity purified, freshly isolated CD34+ progenitors were shown to express low levels of type I interferon (IFN) receptors (740 +/- 60 binding sites/cell, K(d) 0.7 +/- 0.04 nM) determined by Scatchard's analysis using a radiolabelled, neutralizing, monoclonal antibody directed against the IFNAR1 chain of the human type I IFN receptor. Treatment of freshly isolated (day 0), highly purified (>95% pure) CD34+ cells with recombinant IFN-alpha resulted in rapid tyrosine phosphorylation and activation of STAT1, Tyk2 and JAK1 as shown by Western immunoblotting. Similarly, IFN treatment was shown by confocal microscopy to result in rapid nuclear localization of the transcription factors IRF1 and STAT2, demonstrating the presence of functional IFN receptors on freshly isolated (day 0) CD34+ cells. The number of specific type I IFN receptor binding sites expressed on hematopoietic progenitor cells increased to some 1440 +/- 40 per cell after 11 days of cultivation of CD34+ cells in vitrosuggesting that receptor expression increases with cell differentiation. IFN-mediated signal transduction and the inhibitory effect of IFN-alpha on 7 or 14 days CFU-GM and BFU-E colony formation was abrogated in the presence of the anti-IFNAR1 mAb, indicating that IFN-alpha acts directly on the proliferation of human hematopoietic progenitor cells via receptor activated signal transduction without excluding the induction of other cytokines or growth factors by residual accessory cells.

Mycobacterial antigens exacerbate disease manifestations in Mycobacterium tuberculosis-infected mice

To control tuberculosis worldwide, the burden of adult pulmonary disease must be reduced. Although widely used, Mycobacterium bovis BCG vaccination given at birth does not protect against adult pulmonary disease. Therefore, postexposure vaccination of adults with mycobacterial antigens is being considered. We examined the effect of various mycobacterial antigens on mice with prior M. tuberculosis infection. Subcutaneous administration of live or heat-treated BCG with or without lipid adjuvants to infected mice induced increased antigen-specific T-cell proliferation but did not reduce the bacterial load in the lungs and caused larger lung granulomas. Similarly, additional mycobacterial antigen delivered directly to the lungs by aerosol infection with viable M. tuberculosis mixed with heat-killed Mycobacterium tuberculosis (1:1) also did not reduce the bacillary load but caused increased expression of tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6), which was associated with larger granulomas in the lungs. When M. tuberculosis-infected mice were treated with recombinant BCG that secreted cytokines shown to reduce disease in a preinfection vaccine model, the BCG secreting TNF-alpha, and to a lesser extent, IL-2 and gamma interferon (IFN-gamma), caused a significant increase in granuloma size in the lungs. Moreover, treatment of M. tuberculosis-infected mice with recombinant murine TNF-alpha resulted in increased inflammation in the lungs and accelerated mortality without affecting the bacillary load. Taken together, these studies suggest that administration of mycobacterial antigens to mice with prior M. tuberculosis infection leads to immune activation that may exacerbate lung pathology via TNF-alpha-induced inflammation without reducing the bacillary load.

Molecular cloning of ADIR, a novel interferon responsive gene encoding a protein related to the torsins

The expression of the previously uncharacterized gene Adir (for ATP dependent interferon responsive gene) was increased by 5- to 15-fold in tissue of the oral cavity or in spleen and liver of mice treated orally or intraperitoneally with IFN-alpha, and in mouse cells treated in vitro with IFN-alpha or IFN-gamma. The level of Adir mRNA was also increased 20- to 40-fold in the brains of animals infected with encephalomyocarditis virus. Adir is expressed ubiquitously in mouse tissues as 1.9-, 2.4-, and 3.5-kb mRNA transcripts encoding a 385-amino-acid protein with a conserved ATP binding domain containing typical nucleotide and Mg(2+) binding sites. We also characterized the human ortholog, ADIR, which is located on chromosome 1q25-q31 and contains six exons encoding a 397-amino-acid protein with 80% homology to the mouse protein. A single 2.3-kb mRNA was detected in all human tissues examined, except for placenta, which also contained a 1.25-kb tissue-specific transcript generated by alternative splicing and encoding a putative 336-amino-acid protein. Although ADIR exhibits low homology to DYT1 and TOR1B, the deduced ADIR protein sequences are highly homologous to torsin A and torsin B and more distantly related to members of the Clp/HSP100 family of proteins, suggesting that ADIR, like torsins, is related to the AAA chaperone-like family of ATPases. An ADIR-EGFP fusion protein expressed in HeLa cells was shown to be associated with the endoplasmic reticulum.

GAAP-1: a transcriptional activator of p53 and IRF-1 possesses pro-apoptotic activity

The mechanisms that regulate the transcription of the tumour suppressor genes p53 and IRF-1 are poorly understood. We have characterized a 68-kDa transcription factor, GAAP-1 (gatekeeper of apoptosis activating proteins), encoded by an alternative splice product of the PRDII-BF1 gene, that recognizes a novel regulatory element within the p53 and IRF-1 promoters. Transfection of U937 cells with GAAP-1 activates p53 and IRF-1 expression and leads to apoptosis, whereas over-expression of GAAP-1 in K562 cells that lack p53 and IRF-1 induces cell differentiation. Alterations in the 6p24 locus containing the GAAP-1 gene are frequent in acute myelogenous leukemia (AML), and AML-derived cell lines display reduced GAAP-1 mRNA levels. Together, these results suggest that GAAP-1 acts as a gatekeeper at a critical point in the tumour suppressor gene pathway.

Induction of tolerance to recombinant therapeutic proteins

The specific IgM and IgG antibody responses to subcutaneous (s.c.) treatment of mice with recombinant human IFN-alpha2a (rHuIFN-alpha2a) or IFN-beta were inhibited in a dose-dependent manner by prior oromucosal (o.m.) administration of rHuIFN-alpha2a or IFN-beta, respectively. Pretreatment of animals once a day for 7 days by the o.m. route with the highest dose of IFN-alpha2a tested (10(7) IU) resulted in complete inhibition of the peak IFN-alpha2a-specific IgG antibody response detected 28 days after subsequent s.c. injection of IFN-alpha2a (p < 0.001). Similarly, prior o.m. administration of 1-10 microg rHuGM-CSF per day for 7 days resulted in a statistically significant (p < 0.001) inhibition of the peak GM-CSF-specific IgG antibody response detected 28 days after s.c. administration of GM-CSF. In contrast, prior o.m. treatment with a quantity of bovine serum albumin (BSA) (100 microg) or human serum albumin (HSA) (10 microg) equivalent, respectively, to the protein content of the highest dose of IFN-alpha2a or GM-CSF administered by the o.m. route, did not affect significantly the IFN-alpha2a-specific or GM-CSF-specific IgG antibody responses detected on subsequent s.c. administration of IFN-alpha2a or GM-CSF. Oromucosal administration of IFN-alpha2a, IFN-beta, or GM-CSF alone did not induce detectable IFN-alpha2a-specific, IFN-beta-specific, or GM-CSF-specific IgM or IgG antibody responses at any of the time points tested. These results suggest that short-term o.m. administration of a recombinant protein is an effective means of inducing peripheral tolerance to subsequent parenteral administration of a therapeutic protein.

Oromucosal interferon therapy: relationship between antiviral activity and viral load

Intraperitoneal (i.p.) administration of 20,000 IU recombinant murine IFN-alpha (rMuIFN-alpha) was highly effective in protecting mice challenged i.p. with doses of encephalomyocarditis virus (EMCV) ranging from 44 to 440 LD(50) (p<0.001). Oromucosal (o.m.) IFN therapy was also found to be effective in protecting mice challenged with a lethal dose of EMCV. Thus, 40% of animals infected with 44 LD(50) of EMCV and treated o.m. with 20,000 IU rMuIFN-alpha survived infection with a mean survival time of 12.0 +/- 2.46 days relative to a mean of 6.11 +/- 0.38 days in the control group (p<0.05). Oromucosal IFN therapy was found to be ineffective, however, in animals infected with higher doses of EMCV (88-440 LD(50)), even though intraperitoneal administration of the same dose of rMuIFN-alpha resulted in the survival of 90%, 50%, and 60% of animals infected with 88, 220, and 440 LD(50) of EMCV, respectively. These results suggest that oromucosal IFN therapy is effective at relatively low viral load only and that the mechanism of action of oromucosal IFN therapy may be different from that of parenterally administered IFN. Our results suggest that oromucosal IFN therapy may be most effective in chronic viral infections as an alternative to parenterally administered IFN, which is clinically effective but poorly tolerated.

Effect of oromucosal administration of IFN-alpha on allergic sensitization and the hypersensitive inflammatory response in animals sensitized to ragweed pollen

Oromucosal (o.m.) administration of interferon-alpha (IFN-alpha) during either allergic sensitization (days 0-6) or the hypersensitive response (days 11 and 12) or both periods caused a dose-dependent reduction in allergen-specific IgE production and allergen-induced eosinophil recruitment in mice sensitized to ragweed pollen, a common allergen in humans. Treatment during the hypersensitive response period alone appeared to be most effective. Oromucosal treatment was as effective as intraperitoneal (i.p.) treatment, with maximum inhibition of both allergen-specific IgE production and allergen-induced eosinophil recruitment observed at a dose of a 1000 IU IFN-alpha. Treatment of animals with up to 10(5) IU murine IFN-alpha/beta (MuIFN-alpha/beta) by either the om. or i.p. route did not inhibit significantly allergen-specific IgG production, which may even have been increased at certain doses of IFN. Treatment of animals with up to 10(5) IU MuIFN-alpha/beta by either the o.m. or i.p. route did not affect significantly total serum IgE or IgG levels. Oromucosal administration of IFN-alpha reduced allergen-specific IgE production and allergen-induced eosinophil recruitment in the absence of detectable toxicity, the induction of H(2) antigen expression, and 2',5'-oligoadenylate synthetase activity associated with parenteral administration of IFN-alpha and thus may find application for the treatment of asthma and associated viral infections.

Localization of a receptor nonapeptide with a possible role in the binding of the type I interferons

Interferons (IFNs) in common with other cytokines activate Janus tyrosine kinases and latent STAT transcription factors upon binding to their cell surface receptor. Type I IFNs bind to a receptor composed of two transmembrane polypeptides, IFNAR1 and IFNAR2, which belong to the class II cytokine receptor family that also includes the cellular receptors for IFN-gamma, interleukin-10 and coagulation protease factor VII (tissue factor). The extracellular domain of the type I IFN receptor chain IFNAR1, has four fibronectin type-III sub-domains. Human IFNAR1 has intrinsic weak affinity for type I IFNs and plays an essential role in transmembrane signaling, formation of a high affinity complex with IFN and the modulation of ligand specificity. In order to characterise the ligand binding site on IFNAR1 we analysed the epitope recognized by the anti-IFNAR1 mAb, 64G12, which inhibits the binding and biological activities of both IFN-alpha and IFN-beta. The target peptide recognized by the 64G12 mAb was determined by screening a set of 48 overlapping peptides covering the first two subdomains (residues 23-229) of the extracellular region of IFNAR1. The results of this study show that the peptide (FSSLKLNVY), localized within the first sub-domain (residues 89-97) of IFNAR1, which is recognized by the 64G12 mAb, most likely overlaps a site to which both IFN-alpha and IFN-beta bind in the ligand-receptor complex. Thus, since the 64G12 mAb can neutralize the biological activities of all the type I IFNs tested, we suggest that the target peptide recognized by the 64G12 mAb, is a possible anchorage point on IFNAR1, common to binding of both IFN-alpha and IFN-beta.

Enhanced levels of scrapie responsive gene mRNA in BSE-infected mouse brain

The expression of the mRNA of nine scrapie responsive genes was analyzed in the brains of FVB/N mice infected with bovine spongiform encephalopathy (BSE). The RNA transcripts of eight genes were overexpressed to a comparable extent in both BSE-infected and scrapie-infected mice, indicating a common series of pathogenic events in the two transmissible spongiform encephalopathies (TSEs). In contrast, the serine proteinase inhibitor spi 2, an analogue of the human alpha-1 antichymotrypsin gene, was overexpressed to a greater extent in the brains of scrapie-infected animals than in animals infected with BSE, reflecting either an agent specific or a mouse strain specific response. The levels of spi 2 mRNA were increased during the course of scrapie prior to the onset of clinical signs of the disease and the increase reached 11 to 45 fold relative to uninfected controls in terminally ill mice. Spi 2, in common with four of the other scrapie responsive genes studied, is known to be associated with pro-inflammatory processes. These observations underline the importance of cell reactivity in TSE. In addition, scrg2 mRNA the level of which is enhanced in TSE-infected mouse brain, was identified as a previously unrecognized long transcript of the murine aldolase C gene. However, the level of the principal aldolase C mRNA is unaffected in TSE. The increased representation of the longer transcript in the late stage of the disease may reflect changes in mRNA processing and/or stability in reactive astrocytes or in damaged Purkinje cells.

Mucosal cytokine therapy: marked antiviral and antitumor activity

Mucosal administration of the Th1 stimulatory cytokines interleukin-2 (IL-2), IL-12, IL-15, IL-18, or granulocyte-macrophage colony-stimulating factor (GM-CSF) induced antiviral activity in mice challenged systemically with a lethal dose of encephalomyocarditis virus (EMCV) similar to that observed following parenteral administration. In contrast, mucosal administration of the Th2 stimulatory cytokines IL-4, IL-5, IL-10, or IL-13 did not affect significantly the survival of EMCV-infected animals. Mucosal administration of IL-2 or IL-12 also exerted a marked antitumor activity in mice inoculated intravenously with Friend erythroleukemia cells. Recombinant IL-2 and IL-18, but none of the other recombinant cytokines tested, induced low levels of IFN in vitro. Polyclonal antibodies to both mouse and human interferon-alpha/beta (IFN-alpha/beta) abrogated the antiviral activity of IL-2 in vivo, even though the anti-human IFN-alpha/beta antibody did not neutralize mouse IFN-alpha/beta, and neither antibody bound to IL-2. IL-15 did not exhibit antiviral activity in IFN-alpha/beta R-/- mice, which are deficient in natural killer (NK) cell activity. These results suggest that mucosal Th1 cytokine therapy induces a soluble factor or activates a specific cell population in the lymphoid or epithelial tissue of the oropharyngeal cavity, which potentiates elimination of virus-infected or neoplasic cells systemically.

Cloning of a long HIV-1 readthrough transcript and detection of an increased level of early growth response protein-1 (Egr-1) mRNA in chronically infected U937 cells

To identify the pathways involved in HIV-1 modification of cellular gene expression, chronically infected U937 cells were screened by mRNA differential display. A chimeric transcript consisting of the 3' end of the LTR of a HIV-1 provirus, followed by 3.7 kb of cellular RNA was identified suggesting that long readthrough transcription might be one of the mechanisms by which gene expression could be modified in individual infected cells. Such a phenomenon may also be the first step towards the potential transduction of cellular sequences. Furthermore, the mRNA encoding for the transcription factor Egr-1 was detected as an over-represented transcript in infected cells. Northern blot analysis confirmed the increase of Egr-1 mRNA content in both HIV-1 infected promonocytic U937 cells and T cell lines such as Jurkat and CEM. Interestingly a similar increase of Egr-1 mRNA has previously been reported to occur in HTLV-1 and HTLV-2 infected T cell lines. Despite the consistent increase in the level of Egr-1 mRNA, the amount of the encoded protein did not appear to be modified in HIV-1 infected cells, suggesting an increased turn over of the protein in chronically infected cells.

Oromucosal interferon therapy: pharmacokinetics and pharmacodynamics

Oromucosal administration of [125I]-labeled recombinant human interferon-alpha1-8 (IFN-alpha1-8), which is biologically active in the mouse, resulted in readily detectable levels of radioactivity in the serum of animals within 5 min. Biologically active IFN could not be detected in the serum at any time after oromucosal administration, however, and SDS-PAGE analysis showed that the material present in the serum was of low molecular weight and most probably reflected absorption of degradation products following digestion of IFN in the stomach and small intestine. Furthermore, oromucosal administration of murine IFN-alpha/beta (MuIFN-alpha/beta) had no significant effect on the expression of IFN-responsive genes in either peripheral blood mononuclear cells or splenic lymphocytes even though in the same animals IFN treatment activated gene transcription locally in the lymphoid tissue of the oropharyngeal cavity and caused a marked systemic antiviral activity. Oromucosal administration of MuIFN-alpha/beta had no significant effect on either the number of circulating peripheral blood leukocytes or the number of granulocyte-macrophage colonies recovered from the bone marrow of IFN-treated animals. These results suggest that the mechanism of action of oromucosal IFN therapy is distinct from that of parenterally administered IFN and may involve, in the abundant lymphoid or epithelial tissue of the oropharyngeal cavity, either production of a soluble factor or activation of a specific cell population that enters the circulation to mediate the elimination of virus-infected or neoplastic cells.

Oromucosal interferon therapy: marked antiviral and antitumor activity

Oromucosal administration of murine interferon-alpha/beta (IFN-alpha/beta) or individual recombinant species of murine IFN-alpha, IFN-beta, or IFN-gamma or recombinant human IFN-alpha1-8, which is active in the mouse, exerted a marked antiviral activity in mice challenged systemically with a lethal dose of encephalomyocarditis virus (EMCV), vesicular stomatitis virus (VSV), or varicella zoster virus (VZV). The effects observed were dose dependent and similar in magnitude to those observed following parenteral administration of the same dose of IFN. No antiviral activity was observed after oromucosal administration of murine IFN-alpha/beta in animals in which the IFN receptor had been inactivated by homologous recombination. In contrast to parenteral treatment, oromucosal IFN therapy was found to be ineffective when IFNs were administered before virus infection. Oromucosal administration of IFN-alpha also exerted a marked antitumor activity in mice injected i.v. with highly malignant Friend erythroleukemia cells or other transplantable tumors, such as L1210 leukemia, which has no known viral etiology, the EL4 tumor, or the highly metastatic B16 melanoma. These results show that high doses of IFN can be administered by the oromucosal route apparently without ill effect, raising the possibility that the oromucosal route will prove to be an effective means of administering high doses of IFN that are clinically effective but poorly tolerated.

Characterization of the human analogue of a Scrapie-responsive gene

We have recently described a novel mRNA denominated ScRG-1, the level of which is increased in the brains of Scrapie-infected mice (Dandoy-Dron, F., Guillo, F., Benboudjema, L., Deslys, J.-P., Lasmézas, C., Dormont, D., Tovey, M. G., and Dron, M. (1998) J. Biol. Chem. 273, 7691-7697). The increase in ScRG-1 mRNA in the brain follows the accumulation of PrPSc, the proteinase K-resistant form of the prion protein (PrP), and precedes the widespread neuronal death that occurs in late stage disease. In the present study, we have isolated a cDNA encoding the human counterpart of ScRG-1. Comparison of the human and mouse transcripts firmly established that both sequences encode a highly conserved protein of 98 amino acids that contains a signal peptide, suggesting that the protein may be secreted. Examination of the distribution of human ScRG-1 mRNA in adult and fetal tissues revealed that the gene was expressed primarily in the central nervous system as a 0.7-kilobase message and was under strict developmental control.