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Biomedical subjects

M Aguet

Publications and source records attributed to M Aguet.

At least 55 records · Page 3Linked to original sources
PubMed1995

Antiviral protection by vesicular stomatitis virus-specific antibodies in alpha/beta interferon receptor-deficient mice.

The role of innate, alpha/beta interferon (IFN-alpha/beta)-dependent protection versus specific antibody-mediated protection against vesicular stomatitis virus (VSV) was evaluated in IFN-alpha/beta receptor-deficient mice (IFN-alpha/beta R0/0 mice). VSV is a close relative to rabies virus that causes neurological disease in mice. In contrast to normal mice, IFN-alpha/beta R0/0 mice were highly susceptible to infection with VSV because of ubiquitous high viral replication. Adoptive transfer experiments showed that neutralizing antibodies against the glycoprotein of VSV (VSV-G) protected these mice efficiently against systemic infection and against peripheral subcutaneous infection but protected only to a limited degree against intranasal infection with VSV. In contrast, VSV-specific T cells or antibodies specific for the nucleoprotein of VSV (VSV-N) were unable to protect IFN-alpha/beta R0/0 mice against VSV. These results demonstrate that mice are extremely sensitive to VSV if IFN-alpha/beta is not functional and that under these conditions, neutralizing antibody responses mediate efficient protection, but apparently only against extraneuronal infection.

Animals↗
PubMed1995

Antiviral defense in mice lacking both alpha/beta and gamma interferon receptors.

Alpha/beta interferon (IFN) and gamma IFN exert widely overlapping biological effects. Still, mice with individually inactivated alpha/beta or gamma receptors exhibit variably severely reduced resistance to infection and altered immune responses. To investigate to what extent the two IFN systems are functionally redundant, we generated mice with a combined receptor defect (AG129 mice). Like mice with individual mutations, AG129 mice had no apparent anomalies, confirming that in the mouse the IFN system is not essential for normal development. These mice showed an additive phenotype with respect to antiviral defense and exhibited an increased susceptibility to lymphocytic choriomeningitis virus (LCMV) and notably vaccinia virus infection. Because of unlimited replication and subsequent rapid exhaustion of cytotoxic T lymphocyte (CTL) precursors, these mice were unable to mount a CTL response to LCMV. CD8(+)-mediated immunopathology was absent in LCMV-infected mice, and virus persisted. Vaccinia virus replicated much faster in AG129 mice, and a 10(4)-fold lower dose of vaccinia virus was sufficient to prime these mice. With the normal priming dose of 10(6) PFU, cytopathic effects and overwhelming infection possibly causing partial exhaustion of CTL interfered with the anti-vaccinia virus response. Even though global antiviral immunoglobulin G (IgG) titers were within normal ranges, the IgG subclass distribution was heavily biased toward IgG1.

Animals↗
PubMed1995

Role of interferon-gamma in interleukin 12-induced pathology in mice.

Interleukin 12 (IL-12) activates natural killer (NK) and T cells with the secondary synthesis and release of interferon-gamma (IFN-gamma) and other cytokines. IL-12-induced organ alterations are reported for mice and the pathogenetic role of IFN-gamma is investigated by the use of mice deficient in the IFN-gamma receptor (IFN-gamma R-/-). IL-12 caused a rapid infiltration of liver and splenic red pulp with activated macrophages; this and increased NK cells resulted in a fivefold increase of splenic weight in wild-type mice. Splenomegaly was associated with myelosuppression and decreasing peripheral leukocyte counts. IL-12-induced changes in wild-type mice were associated with markedly increased IFN-gamma serum levels and up-regulation of major histocompatibility complex (MHC) class I and II expression in various epithelia. IL-12 induced a qualitatively similar macrophage infiltration in IFN-gamma R-/- mice, less marked splenomegaly (to 2 x normal), and no MHC upregulation. Strikingly increased vascular endothelial intercellular adhesion molecule-1 expression was apparent in both IFN-gamma R-/- and IFN-gamma R+/+ mice. Restricted to mutant mice was a severe, invariably lethal, interstitial, and perivascular pulmonary macrophage infiltration with diffuse pulmonary edema. Extensive quantitative reverse transcriptase polymerase chain reaction analysis revealed an increase of only IL-6 and IL-10 pulmonary gene transcripts in IFN-gamma R-/- mice compared with wild-type mice. IL-12-induced myelosuppression is due to IFN-gamma-release from NK cells and T cells, and is associated with macrophage activation and distinct MHC class I and II antigen upregulation. The pulmonary pathology in IFN-gamma R-/- mice, however, reveals a toxic potential for IL-12 and suggests that endogenous IFN-gamma plays a protective role in preventing fatal pulmonary disease in these mice.

Animals↗
PubMed1994

Mice devoid of interferon regulatory factor 1 (IRF-1) show normal expression of type I interferon genes.

The transcription factor interferon regulatory factor 1 (IRF-1) binds tightly to the interferon (IFN)-beta promoter and has been implicated in the induction of type I IFNs. We generated mice devoid of functional IRF-1 by targeted gene disruption. As reported by others, IRF-1-deficient mice showed a discrete phenotype: the CD4/CD8 ratio was increased and IFN-gamma-induced levels of macrophage iNO synthase mRNA were strongly diminished. However, type I IFN induction in vivo by virus or double-stranded RNA was unimpaired, as evidenced by serum IFN titers and IFN mRNA levels in spleen, liver and lung. There was also no impairment in the response of type I IFN-inducible genes. Therefore, IRF-1 is not essential for these processes in vivo.

Animals↗
PubMed1994

IFN-gamma receptor-deficient mice generate antiviral Th1-characteristic cytokine profiles but altered antibody responses.

The lymphokine IFN-gamma is a pleiotropic immunomodulator and possesses intrinsic antiviral activity. We studied its significance in the development of antiviral immune responses by using IFN-gamma receptor-deficient (IFN-gamma R-/-) mice. After inoculation with live attenuated pseudorabies virus (PRV), the mutant mice showed no infectivity titers in various tissues, and transient viral Ag expression only in the spleen, similar as in wild-type mice. However, the absence of the IFN-gamma R resulted in increased proliferative splenocyte responses. The PRV-immune animals showed a normal IFN-gamma and IL-2 production, without detectable IL-4, and with decreased IL-10 secretion in response to viral Ag or Con A. Immunohistochemically, an increased ratio of IFN-gamma:IL-4-producing spleen cells was found. After immunization with either live attenuated or inactivated PRV, IFN-gamma R-/- mice produced significantly less antiviral Ab, and more succumbed to challenge infection than the intact control animals. The reduction in Ab titers in the mutant mice correlated with lower protection by their sera in transfer experiments. Our data demonstrate that ablation of the IFN-gamma receptor surprisingly does not inhibit the generation of antiviral Th1-type and increase Th2-type cytokine responses. However, it profoundly impairs the generation of protective antiviral Ab.

Animals↗
PubMed1994

Functional role of type I and type II interferons in antiviral defense.

Mice lacking the known subunit of the type I interferon (IFN) receptor were completely unresponsive to type I IFNs, suggesting that this receptor chain is essential for type I IFN-mediated signal transduction. These mice showed no overt anomalies but were unable to cope with viral infections, despite otherwise normal immune responses. Comparison of mice lacking either type I or type II IFN receptors showed that, at least in response to some viruses, both IFN systems are essential for antiviral defense and are functionally nonredundant.

Alphavirus Infections↗
PubMed1994

The transcription factor MTF-1 is essential for basal and heavy metal-induced metallothionein gene expression.

We have described and cloned previously a factor (MTF-1) that binds specifically to heavy metal-responsive DNA sequence elements in the enhancer/promoter region of metallothionein genes. MTF-1 is a protein of 72.5 kDa that contains six zinc fingers and multiple domains for transcriptional activation. Here we report the disruption of both alleles of the MTF-1 gene in mouse embryonic stem cells by homologous recombination. The resulting null mutant cell line fails to produce detectable amounts of MTF-1. Moreover, due to the loss of MTF-1, the endogenous metallothionein I and II genes are silent, indicating that MTF-1 is required for both their basal and zinc-induced transcription. In addition to zinc, other heavy metals, including cadmium, copper, nickel and lead, also fail to activate metal-responsive promoters in null mutant cells. However, cotransfection of an MTF-1 expression vector and metal-responsive reporter genes yields strong basal transcription that can be further boosted by zinc treatment of cells. These results demonstrate that MTF-1 is essential for metallothionein gene regulation. Finally, we present evidence that MTF-1 itself is a zinc sensor, which exhibits increased DNA binding activity upon zinc treatment.

Animals↗
PubMed1994

PrP-deficient mice are resistant to scrapie.

Prusiner proposed that the infectious agent of scrapie, the prion, is PrPSc, a modified form of the normal host protein PrPC. Prn-p0/0 mice devoid of PrPC showed normal development and behavior. When inoculated with mouse scrapie prions they remained free of scrapie symptoms for at least 16 months while wild type controls all died within 6 months. Propagation of infectivity in the PrP null mice, if any, was less than 10(-5) that in wild type animals. Surprisingly, heterozygous Prn-p0/+ mice also showed enhanced resistance to scrapie. After introduction of Syrian hamster PrP transgenes, Prn-p0/0 mice became highly susceptible to hamster but not to mouse prions. These experiments show that PrPC, possibly at close to normal levels, is required for the usual susceptibility to scrapie and that lack of homology between incoming prions and the host's PrP genes retards disease.

Animals↗
PubMed1994

Signaling steps involving the cytoplasmic domain of the interferon-gamma receptor alpha-subunit are not species-specific.

The ligand-binding chain of the interferon-gamma receptor (IFN-gamma R) is a unique cell surface protein which has no similarities to other cytokine receptors. Expression of this receptor chain (alpha-subunit) is not sufficient to mediate responsiveness to IFN-gamma. We and others have shown that IFN-gamma-mediated signal transduction requires a species-specific interaction of the extracellular portion of the known IFN-gamma receptor alpha-chain with an additional receptor subunit that was cloned recently and designated IFN-gamma R beta-chain or accessory factor 1. Here, we investigated whether this tight species barrier also applies to signaling events mediated by the cytoplasmic receptor domain. A cell line derived from embryos that lack the IFN-gamma R alpha-subunit was reconstituted with a hybrid mouse-human alpha-subunit that consisted of an extracellular murine and transmembrane and cytoplasmic human domains. The experiments reported herein showed that in mouse cells, the human intracellular domain of the hybrid IFN-gamma R alpha-subunit was fully functional and that, therefore, signaling steps involving this domain are not species-specific.

Animals↗
PubMed1994

Interferon gamma receptor deficient mice are resistant to endotoxic shock.

Antibody neutralization studies have established interferon gamma (IFN-gamma) as a critical mediator of endotoxic shock. The advent of IFN-gamma receptor negative (IFN gamma R-/-) mutant mice has enabled a more direct assessment of the role of IFN-gamma in endotoxin (lipopolysaccharide [LPS]-induced shock. We report that IFN gamma R-/- mice have an increased resistance to LPS-induced toxicity, this resistance manifesting well before the synthesis and release of LPS-induced IFN-gamma. LPS-induced lymphopenia, thrombocytopenia, and weight loss seen in wild-type mice were attenuated in IFN gamma R-/- mice. IFN gamma R-/- mice tolerated 100-1,000 times more LPS than the minimum lethal dose for wild-type mice in a D-galactosamine (D-GalN)/LPS model. Serum tumor necrosis factor (TNF) levels were 10-fold reduced in mutant mice given LPS or LPS/D-GalN. Bone marrow and splenic macrophages from IFN gamma R-/- mice had a four- to sixfold decreased LPS-binding capacity which correlated with similar reduction in CD14. Serum from mutant mice reduced macrophage LPS binding by a further 50%, although LPS binding protein was only 10% reduced. The expression of TNF receptor I (p55) and II (p75) was identical between wild-type and mutant mice. Thus, depressed TNF synthesis, diminished expression of CD14, and low plasma LPS-binding capacity, in addition to blocked IFN-gamma signaling in the mutant mice, likely to combine to manifest in the resistant phenotype of IFN gamma R-/- mice to endotoxin.

Animals↗
PubMed1994

Susceptibility to scrapie in mice is dependent on PrPC.

Mice devoid of functional PrP genes (Prn-p(o/o) mice) showed normal development and behaviour. When inoculated with mouse scrapie prions they remained free of scrapie symptoms for at least 18 months whereas wild-type controls all died within 6 months. No propagation of infectivity could be detected in the PrP null mice. Surprisingly, heterozygous Prn-p(o/+) mice also showed enhanced resistance to scrapie. After introduction of Syrian hamster PrP transgenes, Prn-p(o/o) mice became highly susceptible to hamster but not to mouse prions. These experiments show that PrPC, possibly at close to normal levels, is required for the usual susceptibility to scrapie and that lack of homology between incoming prions and the host's PrP genes retards disease.

Animals↗
PubMed1994

A novel member of the interferon receptor family complements functionality of the murine interferon gamma receptor in human cells.

Expression of the human interferon gamma receptor (IFN-gamma R) in mouse cells is not sufficient to confer biological responsiveness to human IFN-gamma and vice versa. An additional species-specific component is required for signal transduction. We identified this cofactor by expression cloning in simian COS cells stably transfected with the nonfunctional murine IFN-gamma R and a IFN-gamma-inducible reporter construct encoding the human Tac antigen (interleukin-2 receptor alpha chain, CD25). A cDNA clone was obtained that, upon stable transfection, rendered human HEp-2 cells expressing the murine IFN-gamma R fully responsive to murine IFN-gamma. This cDNA encodes a novel 332 amino acid type I transmembrane protein that belongs to the IFN receptor family and that we designate IFN-gamma R beta chain.

Amino Acid Sequence↗
PubMed1993

Mice that lack the interferon-gamma receptor have profoundly altered responses to infection with Bacillus Calmette-Guérin and subsequent challenge with lipopolysaccharide.

Mice with a targeted disruption of the interferon gamma receptor gene (IFN-gamma R0/0 mice) and control wild-type mice were inoculated with the Bacillus Calmette-Guérin (BCG) strain of Mycobacterium bovis. BCG infection was not lethal for wild-type mice whereas all IFN-gamma R0/0 mice died approximately 7-9 wk after inoculation. Histological examination at 2 and 6 wk after BCG inoculation showed that livers of IFN-gamma R0/0 mice had higher numbers of acid-fast bacteria than wild-type mice, especially at 6 wk. In parallel, the livers of IFN-gamma R0/0 mice showed a reduction in the formation of characteristic granulomas at 2 wk after inoculation. Injection of lipopolysaccharide (LPS) 2 wk after BCG inoculation was significantly less lethal for IFN-gamma R0/0 mice than for wild-type mice. Reduced lethality of LPS correlated with a drastically reduced production of tumor necrosis factor alpha (TNF-alpha) in the IFN-gamma R0/0 mice. Interleukin 1 alpha (IL-1 alpha) and IL-6 levels in the serum were also significantly reduced in the IFN-gamma R0/0 mice after BCG infection and LPS challenge. The greatly reduced capacity of BCG-infected IFN-gamma R0/0 mice to produce TNF-alpha may be an important factor in their inability to resist BCG infection. These results show that the presence of a functional IFN-gamma receptor is essential for the recovery of mice from BCG infection, and that IFN-gamma is a key element in the complex process whereby BCG infection leads to the sensitization to endotoxin.

Animals↗
PubMed1993

Generation of nitric oxide and induction of major histocompatibility complex class II antigen in macrophages from mice lacking the interferon gamma receptor.

Availability of mice with a targeted disruption of the interferon gamma (IFN-gamma) receptor gene (IFN-gamma R0/0 mice) made it possible to examine parameters of macrophage activation in the absence of a functional IFN-gamma receptor. We asked to what extent other cytokines could replace IFN-gamma in the induction of nitric oxide or major histocompatibility complex class II antigen (Ia) expression in peritoneal macrophages. In thioglycollate-elicited macrophages from wild-type mice, tumor necrosis factor (TNF) alone was virtually ineffective in inducing release of NO2- (the endproduct of nitric oxide generation), but TNF enhanced NO2- release in the presence of IFN-gamma. In macrophages from IFN-gamma R0/0 mice, which were unresponsive to IFN-gamma, TNF completely failed to stimulate NO2- release. The stimulatory actions of IFN-alpha/beta on NO2- release were indistinguishable in wild-type and IFN-gamma R0/0 macrophages: IFN-alpha/beta was ineffective on its own, showed marginal stimulation of NO2- release in combination with TNF, and was moderately effective in the presence of lipopolysaccharide. The level of constitutive Ia antigen expression was not significantly different in peritoneal macrophages from wild-type and IFN-gamma R0/0 mice. An increased Ia expression was induced by IL-4 and granulocyte-macrophage colony-stimulating factor in both wild-type and IFN-gamma R0/0 macrophages, but the magnitude of this induction was less than with optimal concentrations of IFN-gamma in macrophages from wild-type mice. IFN-alpha/beta showed only a minor stimulatory effect on Ia expression in both wild-type and IFN-gamma R0/0 macrophages. Simultaneous treatment of wild-type macrophages with IFN-alpha/beta and IFN-gamma reduced the IFN-gamma-induced Ia expression in wild-type macrophages, but IFN-alpha/beta did not show an inhibitory effect on IL-4- or granulocyte-macrophage-colony-stimulating factor-induced Ia expression in either wild-type or IFN-gamma R0/0 macrophages. The important role of IFN-gamma in the regulation of the induced expression of major histocompatibility complex class II antigen was confirmed by showing that after systemic infection with the BCG strain of Mycobacterium bovis resident peritoneal macrophages from IFN-gamma R0/0 mice had a lower level of Ia expression than macrophages from wild-type mice. The inability of other cytokines to substitute fully for IFN-gamma in macrophage activation helps to explain the earlier observed decreased resistance of IFN-gamma R0/0 mice to some infections.

Animals↗
PubMed1993

Mice devoid of PrP are resistant to scrapie.

S.B. Prusiner proposed that the infectious agent of scraple, the prion, is PrPSc, a modified form of the normal host protein PrPC. Prn-p0/0 mice devoid of PrPC showed normal development and behavior. When inoculated with mouse scrapie prions, they remained free of scrapie symptoms for at least 13 months while wild-type controls all died within 6 months. Surprisingly, heterozygous Prn-p0/+ mice also showed enhanced resistance to scrapie. After introduction of Syrian hamster PrP transgenes, Prn-p0/0 mice became highly susceptible to hamster but not to mouse prions. These experiments show that PrPC, possibly at close to normal levels, is required for the usual susceptibility to scrapie and that lack of homology between incoming prions and the host's PrP genes retards disease.

Animals↗
PubMed1993

Immune response in mice that lack the interferon-gamma receptor.

Interferon-gamma (IFN-gamma) exerts pleiotropic effects, including antiviral activity, stimulation of macrophages and natural killer cells, and increased expression of major histocompatibility complex antigens. Mice without the IFN-gamma receptor had no overt anomalies, and their immune system appeared to develop normally. However, mutant mice had a defective natural resistance, they had increased susceptibility to infection by Listeria monocytogenes and vaccinia virus despite normal cytotoxic and T helper cell responses. Immunoglobulin isotype analysis revealed that IFN-gamma is necessary for a normal antigen-specific immunoglobulin G2a response. These mutant mice offer the possibility for the further elucidation of IFN-gamma-mediated functions by transgenic cell- or tissue-specific reconstitution of a functional receptor.

Animals↗
PubMed1993

Role of the PrP gene in transmissible spongiform encephalopathies.

The transmissible agent that causes spongiform encephalopathies such as scrapie, the prion, is believed to be devoid of nucleic acid and identical with PrPSc, a modified form of PrPC. PrPC is a normal host protein encoded by a single copy gene (Prn-p) and is found predominantly on the surface of neurons. PrPSc, in contrast to PrPC, is resistant to protease and accumulates intracellularly. Prusiner proposed that PrPSc, when introduced into a normal host, causes the conversion of PrPC or its precursor into PrPSc ('protein only' hypothesis). If indeed PrP is an essential component of the prion, then an animal devoid of the PrP protein should be resistant to scrapie. We generated homozygous PrP 'knockout' mice. These Prn-p0/0 mice showed no gross abnormalities, and microscopic examination of brain sections of normal and Prn-p0/0 mice revealed no differences. Prn-p0/0, Prn-p+/+ and Prn-p0/+ mice were inoculated with scrapie agent; the clinical response as well as the prion titer at different time points are being determined.

Animals↗