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M B Oldstone

Publications and source records attributed to M B Oldstone.

At least 73 records · Page 4Linked to original sources
PubMed1997

Deficits in discriminated learning remain despite clearance of long-term persistent viral infection in mice.

Mice persistently infected with lymphocytic choriomeningitis virus (LCMV) exhibit impaired learning ability. In this report, we determined whether clearance of the virus was associated with restoration of behavioral function. Neonatal Balb/cByJ mice were persistently infected with LCMV and tested as adults in a nonconditional spatial discrimination task. The presence of viral proteins in neurons was confirmed immunohistochemically and infectious virus was quantified in the blood by plaque assay. LCMV-infected adult mice made more errors in a Y-maze avoidance task compared to sham-inoculated controls. After the initial behavioral analysis, infected and control mice received a dose of cytotoxic T-lymphocytes sufficient to clear virus from these mice. Following complete clearance of the virus, mice were re-tested in the behavioral task, 5 months after the original test. No reversal of the learning deficit was seen following viral clearance; mice that had been cleared of the virus and those that remained persistently infected behaved similarly. These data indicate that persistent LCMV infection of the CNS lasting up to 7 months results in discriminated learning impairments that are not reversed by subsequent anti-viral immunocytotherapy.

Aging↗
PubMed1996

Viral infection of transgenic mice expressing a viral protein in oligodendrocytes leads to chronic central nervous system autoimmune disease.

One hypothesis for the etiology of central nervous system (CNS) autoimmune disease is that infection by a virus sharing antigenic epitopes with CNS antigens (molecular mimicry) elicits a virus-specific immune response that also recognizes self-epitopes. To address this hypothesis, transgenic mice were generated that express the nucleoprotein or glycoprotein of lymphocytic choriomeningitis virus (LCMV) as self in oligodendrocytes. Intraperitoneal infection with LCMV strain Armstrong led to infection of tissues in the periphery but not the CNS, and the virus was cleared within 7-14 d. After clearance, a chronic inflammation of the CNS resulted, accompanied by upregulation of CNS expression of MHC class I and II molecules. A second LCMV infection led to enhanced CNS pathology, characterized by loss of myelin and clinical motor dysfunction. Disease enhancement also occurred after a second infection with unrelated viruses that cross-activated LCMV-specific memory T cells. These findings indicate that chronic CNS autoimmune disease may be induced by infection with a virus sharing epitopes with a protein expressed in oligodendrocytes and this disease may be enhanced by a second infection with the same or an unrelated virus. These results may explain the association of several different viruses with some human autoimmune diseases.

Animals↗
PubMed1996

Studies using double mutants of the conformational transitions in influenza hemagglutinin required for its membrane fusion activity.

Amino acid substitutions widely distributed throughout the influenza hemagglutinin (HA) influence the pH of its membrane fusion activity. We have combined a number of these substitutions in double mutants and determined the effects on the pH of fusion and on the pH at which the refolding of HA required for fusion occurs. By analyzing combinations of mutations in three regions of the metastable neutral-pH HA that are rearranged at fusion pH we obtain evidence for both additive and nonadditive effects and for an apparent order of dominance in the effects of amino acid substitutions in particular regions on the pH of fusion. We conclude that there are at least three components in the structural transition required for membrane fusion activity and consider possible pathways for the transition in relation to the known differences between neutral and fusion pH HA structures.

Aspartic Acid↗
PubMed1996

Changes in the cytoplasmic structure of CTLs during target cell recognition and killing.

CTL play a critical role in immune defense by recognizing and killing virally infected or tumor cells. In this report, the structure of cytoplasm within living CTL was monitored during CTL killing of target cells. Living CTL were simultaneously loaded with fluorescent 70,000- and 10,000-kDa dextran particles. The relative distribution of the large and small dextrans within CTL revealed subcellular heterogeneities in the submicroscopic structure of cytoplasm. Localized alterations in cytoplasmic structure correlated with specific events during CTL killing. Recognition of target cells was accompanied by a transient increase in large dextran accessibility over a broad front near the interface between CTL and target cells. This region narrowed to a smaller area from which pseudopodia were extended toward the target. During extension, there was a large difference between regions of high dextran accessibility within the pseudopod and more structured cytoplasm within the cell body. Areas undergoing structural changes showed localized foci of high dextran accessibility. During retraction, cytoplasmic structure became gradually more uniform throughout the protrusion and cell body. These observations revealed subcellular regions undergoing major changes during early stages of the killing response, and addressed the role of cytoplasmic solation in controlling CTL morphology. They support mechanisms of pseudopod extension driven by hydrostatic pressure and demonstrate a precise regulation of cortical structure to control the direction of pseudopod extension.

Animals↗
PubMed1996

Oral insulin treatment suppresses virus-induced antigen-specific destruction of beta cells and prevents autoimmune diabetes in transgenic mice.

Oral administration of self-antigens has been proposed as a therapy to prevent and treat autoimmune diseases. Here we report that oral treatment with insulin prevents virus-induced insulin-dependent diabetes mellitus (IDDM) in a transgenic (tg) mouse model. Such mice express the viral nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV) under control of the rat insulin promoter in their pancreatic beta cells and < 2% spontaneously develop diabetes. However, 2 mo after challenge with LCMV, IDDM occurs in > 95% of tg mice but not in controls. Oral treatment with 1 mg of insulin twice per week for 2 mo starting either 1 wk before or 10 d after initiating LCMV infection prevents IDDM in > 50% of the tg mice (observation time 8 mo). Thus, insulin therapy is effective in preventing progression to overt IDDM in prediabetic tg mice with ongoing islet infiltration. Oral administration of insulin does not affect the generation of LCMV-NP-specific anti-self cytotoxic T lymphocytes nor the infiltration of lymphocytes into the pancreas. However, less beta cells are destroyed in insulin-treated mice, upregulation of MHC class I and II molecules does not occur, and antiviral (self) cytotoxic T lymphocytes are not found in the islets, events present in tg mice developing IDDM. The majority of lymphocytes in the islets of insulin-treated tg mice without IDDM produces IL-4, IL-10, and TGF-beta. In contrast, lymphocytes from islets of tg mice developing IDDM mainly make gamma-IFN.

Administration, Oral↗
PubMed1996

Suppression of lymphocytic choriomeningitis virus--induced growth hormone deficiency syndrome by disease-negative virus variants.

Populations of RNA viruses consist of heterogeneous mixtures of related genomes (quasispecies). Isolation of variants present at low levels within a population can result in clonal virus populations which display markedly different phenotypes upon infection of the host. The mechanisms by which these variants are maintained within the original quasispecies are not understood. Certain strains of lymphocytic choriomeningitis virus (LCMV) cause a growth hormone deficiency syndrome (GHDS) when inoculated into newborn C3H/St mice while others do not. We have previously described the isolation of virus clones from the GHDS-negative WE strain of LCMV which differ in their ability to cause GHDS. To investigate how disease-positive clones can remain hidden within a disease-negative parental population, we examined whether infection with mixtures of the GHDS-negative (WE c54) and GHDS-positive (WE c2.5) clones could cause GHDS. Neonatal C3H/ST mice infected with 100:1 or 10:1 ratios of WE c54 to WE c2.5 did not develop the syndrome, while animals infected with 1:1 or lower ratios did. Development of GHDS correlated with the extent to which the GH-producing cells of the anterior pituitary were infected. These data indicate that a large excess of disease-negative clones can restrict the replication of disease-positive clones in GH-producing cells, thus preventing the onset of GHDS. In addition, our results indicate that a threshold for phenotypic dominance exists. Interestingly, WE c54 did not entirely outcompete WE c2.5 in mice infected with the 100:1 ratio, suggesting a mechanism whereby pathogenic viruses can be maintained within a nonpathogenic viral population.

Animals↗
PubMed1996

Binding of viral antigens to major histocompatibility complex class I H-2Db molecules is controlled by dominant negative elements at peptide non-anchor residues. Implications for peptide selection and presentation.

Binding of viral antigens to major histocompatibility complex (MHC) class I molecules is a critical step in the activation process of CD8(+) cytotoxic T lymphocytes. In this study, we investigated the impact of structural factors at non-anchor residues in peptide-MHC interaction using the model of lymphocytic choriomeningitis virus (LCMV) infection of its natural host, the mouse. Altering viral genes by making reassortants, recombinants, and using synthetic peptides, CD8(+) cytotoxic T lymphocytes were shown to recognize only three H-2Db-restricted epitopes, GP amino acids 33-41/43, GP 276-286, and NP 396-404. However, LCMV NP and GP proteins contain 31 other peptides bearing the H-2Db motif. These 34 LCMV peptides and 11 other known H2-Db-restricted peptides were synthesized and examined for MHC binding properties. Despite the presence of the H-2Db binding motif, the majority of LCMV peptides showed weak or no affinity for H-2Db. We observed that dominant negative structural elements located at non-anchor positions played a crucial role in peptide-MHC interaction. By comparative sequence analysis of strong versus non-binders and using molecular modeling, we delineated these negative elements and evaluated their impact on peptide-MHC interaction. Our findings were validated by showing that a single mutation of a favorable non-anchor residue in the sequence of known viral epitopes for a negative element resulted in dramatic reduction of antigen presentation properties, while conversely, substitution of one negative for a positive element in the sequence of a non-binder conferred to the peptide an ability to now bind to MHC molecules.

Amino Acid Sequence↗
PubMed1996

Viral persistence in neurons alters synaptic plasticity and cognitive functions without destruction of brain cells.

Neurons have a restricted expression of MHC heavy chain molecules which prevents presentation of antigens of infecting viruses. As a result, such infected cells escape immune surveillance and allow the establishment of noncytolytic persistent infection. Here we show that a chronic noncytolytic viral infection both in vitro and in vivo selectively perturbed the expression of GAP-43, a protein that plays a central role in neuronal plasticity processes accompanying learning and memory. GAP-43 expression was greatly decreased in the hippocampus, an area of heightened viral replication, while synaptic density was preserved. Concurrently, the ability to learn tasks was significantly impaired in these persistently infected mice. Yet, infected neurons remained free from structural injury.

Animals↗
PubMed1996

Viral cross talk: intracellular inactivation of the hepatitis B virus during an unrelated viral infection of the liver.

Hepatitis B virus (HBV) infection is thought to be controlled by virus-specific cytotoxic T lymphocytes (CTL). We have recently shown that HBV-specific CTL can abolish HBV replication noncytopathically in the liver of transgenic mice by secreting tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) after antigen recognition. We now demonstrate that hepatocellular HBV replication is also abolished noncytopathically during lymphocytic choriomeningitis virus (LCMV) infection, and we show that this process is mediated by TNF-alpha and IFN-alpha/beta produced by LCMV-infected hepatic macrophages. These results confirm the ability of these inflammatory cytokines to abolish HBV replication; they elucidate the mechanism likely to be responsible for clearance of HBV in chronically infected patients who become superinfected by other hepatotropic viruses; they suggest that pharmacological activation of intrahepatic macrophages may have therapeutic value in chronic HBV infection; and they raise the possibility that conceptually similar events may be operative in other viral infections as well.

Animals↗
PubMed1996

CD40L-deficient mice show deficits in antiviral immunity and have an impaired memory CD8+ CTL response.

The ligand for CD40 (CD40L) is expressed on the surface of activated CD4+ T cells and its role in T-B cell collaborations and thymus-dependent humoral immunity is well established. Recently, by generating CD40L-knockout mice, we have confirmed its previously described role in humoral immunity and defined another important function of this molecule in the in vivo clonal expansion of antigen-specific CD4+ T cells. Here, we investigated the potential in vivo role of CD40L in antiviral immunity by examining the immune response mounted by CD40L-deficient mice following infection with lymphocytic choriomeningitis virus (LCMV), Pichinde virus, or vesicular stomatitis virus. Humoral immune responses of CD40L-deficient mice to these viruses were severely compromised, although moderate titres of antiviral IgM and some IgG2a were produced by virus-infected CD40L-deficient mice by a CD4+ T cell-independent mechanism. By contrast, CD40L-deficient mice made strong primary CTL responses to all three viruses. Interestingly however, although memory CTL activity was detectable in CD40L-deficient mice two months after infection with LCMV, the memory CTL response was much less efficient than in wild-type mice. Together, the results show that CD40-CD40L interactions are required for strong antiviral humoral immune responses, and reveal a novel role for CD40L in the establishment and/or maintenance of CD8+ CTL memory.

Animals↗
PubMed1996

The M22 antibody identifies highly activated reactive astrocytes responding to central nervous system disease.

Astrocytes respond vigorously to diverse neurological insults. It is still not clear, however, whether this response is stereotypic following different insults or varies according to the injury. We have used a novel immunocytochemical marker of reactive astrocytes, termed M22, together with antibodies to glial fibrillary acidic protein (GFAP), to analyze region- and insult-specific differences in reactive astrocytosis in the murine central nervous system (CNS). Pathology was variously induced by (1) infectious agents, (2) transgenic overexpression of a viral glycoprotein or cytokine, or (3) focal trauma. Scrapie infection induced high levels of both GFAP and M22 epitope expression by hippocampal reactive astrocytes, but neither scrapie nor wild mouse retrovirus infection induced detectable M22 staining in reactive astrocytes of the caudal brain. Focal trauma and human immunodeficiency virus gp120 overexpression induced M22 expression only in the hippocampus, while interleukin-6 overexpression induced it in cerebellar astrocytes. Although M22 expression was limited to areas with extensive damage, GFAP expression was induced in every region of the mouse brain displaying pathology. Staining of routinely fixed human brain tissue demonstrated that M22 also labeled reactive astrocytes in chronic human CNS disease. The restriction of M22 expression to areas of strongly GFAP-positive astrocytosis suggests that the M22 antibody identified highly activated reactive astrocytes. Because of this selective staining of activated astrocytes, the M22 antibody may provide neuropathologists with a good marker for qualitative analysis of the astrocytic response to different injuries.

Animals↗
PubMed1996

Virus-induced autoimmune disease.

The breaking of tolerance or unresponsiveness to self-antigens, involving the activation of autoreactive lymphocytes, is a critical event leading to autoimmune diseases. The precise mechanisms by which this can occur are mostly unknown. Viruses have been implicated in this process, among other etiological factors, such as genetic predisposition and cytokine activity. Several ways have been proposed by which a viral infection might break tolerance to self and trigger an autoreactive cascade that ultimately leads to the destruction of a specific cell type or an entire organ. The process termed "molecular mimicry' and the use of transgenic models in which viral and host genes can be manipulated to analyze their effects in causing autoimmunity have been particular focuses for research. For example, there is a transgenic murine model of virus-induced autoimmune disease, in which a known viral gene is selectively expressed as a self-antigen in beta cells of the pancreas. In these mice, insulin-dependent diabetes develops after either a viral infection, the release of a cytokine such as IFN-gamma, or the expression of the costimulatory molecule B7.1 in the islets of Langerhans. Recent studies using this model have contributed to the understanding of the pathogenesis of virus-induced autoimmune disease and have furthered the design and testing of novel immunotherapeutic approaches.

Animals↗
PubMed1996

A model of measles virus-induced immunosuppression: enhanced susceptibility of neonatal human PBLs.

Measles virus (MV) still incites one of the most contagious infections of humankind. Despite the development and use of an excellent live attenuated virus vaccine, over one million infants and children continue to die each year from measles. The main cause of morbidity and mortality is virus-induced immunosuppression of lymphocyte function, which allows secondary infections. Here we report an in vivo model for the study of MV-induced immunosuppression. Human peripheral blood leukocytes (PBLs) grafted onto mice with severe combined immunodeficiency disease (SCID mice) to create hu-PBLS-SCID mice produce human IgG that is suppressed by MV infection. Immunosuppression is dependent on the involvement of live virus and is dramatically more severe for PBLs obtained from newborns than PBLs from adults. Suppression of IgG synthesis by PBLs from newborns occurs as early as ten days after administration of MV to hu-PBLS-SCID mice compared with 44 days required for PBLs from adults. Further, MV infection of SCID mice reconstituted with PBLs from newborns.

Adult↗
PubMed1996

Using transgenic mouse models to dissect the pathogenesis of virus-induced autoimmune disorders of the islets of Langerhans and the central nervous system.

Viruses have often been associated with autoimmune diseases. One mechanism by which self-destruction can be triggered is molecular mimicry. Many examples of cross-reactive immune responses between pathogens and self-antigens have been described. This review presents two transgenic models of autoimmune disease induced by a virus through activation of anti-self lymphocytes. Viral antigens are expressed as transgenes either in beta-cells of the pancreas or in the oligodendrocytes of the CNS. Infection by a virus encoding the same gene activated autoreactive T cells that cleared the viral infection, and as a consequence of transgene expression resulted in organ-specific autoimmune disease. In both transgenic mouse models, autoreactive lymphocytes that escaped thymic negative selection were present in the periphery. Several factors are described that play a role in the regulation of the self-reactive process precipitated by a viral infection. These include the quantity of activated autoreactive T cells, the affinity of these T cells, the number of memory T cells generated following primary infection, costimulation by accessory molecules, and the types and locations of cytokines produced. In addition, unique barriers exist in target tissues that prevent or suppress autoreactive responses and define to a large extent the outcome of disease. Restimulation of autoreactive memory lymphocytes may be required to bypass these barriers and enhance autoimmune disease. Therapy directed at modifying these factors can reduce and even prevent autoimmune disease after it has been initiated.

Animals↗