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Biomedical subjects

Bernhard Hemmer

Publications and source records attributed to Bernhard Hemmer.

At least 19 recordsLinked to original sources
PubMed2007

CD8 T-cell subsets and viral load in the cerebrospinal fluid of therapy-naive HIV-infected individuals.

Central nervous system involvement is common in HIV infection. We determined the relationship between T-cell subsets and viral load in the cerebrospinal fluid (CSF) of therapy-naive, asymptomatic HIV-infected individuals. A shift from naive to effector-memory CD8 T cells was observed in the CSF of HIV-infected individuals compared with controls. The HIV load strongly correlated with CD8 T cells in CSF. Effector-memory CD8 T cells were positively and effector CD8 T cells were negatively associated with viral replication in CSF.

CD8-Positive T-Lymphocytes↗
PubMed2006

Identification of a pathogenic antibody response to native myelin oligodendrocyte glycoprotein in multiple sclerosis.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Although the cause of MS is still uncertain, many findings point toward an ongoing autoimmune response to myelin antigens. Because of its location on the outer surface of the myelin sheath and its pathogenicity in the experimental autoimmune encephalomyelitis model, myelin oligodendrocyte glycoprotein (MOG) is one of the potential disease-causing self antigens in MS. However, the role of MOG in the pathogenesis of MS has remained controversial. In this study we addressed the occurrence of autoantibodies to native MOG and its implication for demyelination and axonal loss in MS. We applied a high-sensitivity bioassay, which allowed detecting autoantibodies that bind to the extracellular part of native MOG. Antibodies, mostly IgG, were found in sera that bound with high affinity to strictly conformational epitopes of the extracellular domain of MOG. IgG but not IgM antibody titers to native MOG were significantly higher in MS patients compared with different control groups with the highest prevalence in primary progressive MS patients. Serum autoantibodies to native MOG induced death of MOG-expressing target cells in vitro. Serum from MS patients with high anti-MOG antibody titers stained white matter myelin in rat brain and enhanced demyelination and axonal damage when transferred to autoimmune encephalomyelitis animals. Overall these findings suggest a pathogenic antibody response to native MOG in a subgroup of MS patients.

Animals↗
PubMed2006

Accumulation of class switched IgD-IgM- memory B cells in the cerebrospinal fluid during neuroinflammation.

Inflammatory diseases of the central nervous system (CNS) are characterized by cerebrospinal fluid (CSF) pleocytosis often involving the recruitment of B cells. Little is still known about B cells that are found in the CSF during neuroinflammation. To address the phenotype of these B cells, we studied the distribution of the major B cell subsets in peripheral blood (PB) and CSF of 25 patients with inflammatory diseases of the nervous system by flow cytometry. Six different B cell subsets were identified in PB and CSF according to the surface expression of IgM, IgD, CD27 and CD19. In all patients analysed, memory B cells outnumbered naïve B cells in the CSF, whereas naïve B cells were more prevalent in PB. The accumulation of memory B cells in the CSF was largely due to the recruitment of IgM-IgD- class switched memory B cells. The distribution of IgM+IgD+, IgM-IgD+, IgM+IgD- memory cells and immature cells did not differ significantly between CSF and PB. These findings demonstrate a selective recruitment of IgM-IgD- memory B cells to the CSF suggesting a specific role of these cells during neuroinflammation.

Adult↗
PubMed2006

Suppression of autoimmune encephalomyelitis by a neurokinin-1 receptor antagonist--a putative role for substance P in CNS inflammation.

Substance P (SP) is an excitatory neurotransmitter in the central and peripheral nervous system. Most of its physiological functions are mediated through binding to the neurokinin-1 receptor (NK-1R). Recently, proinflammatory properties of SP have been described. In this study we utilized T cell transfer experimental autoimmune encephalomyelitis (EAE) to investigate the role of SP in CNS autoimmune disease. Treatment with the NK-1R antagonist CP-96,345 dramatically reduced clinical and histological signs of EAE if administered before disease onset. The protective effect of CP96,345 treatment was related to a reduced expression of the adhesion molecules ICAM-1 and VCAM-1 on CNS endothelia. The cellular composition or activation status of splenocytes was not affected by CP-96,345 administration, while the secretion of proinflammatory Th1 cytokines was reduced in treated animals. Th2 cytokines remained largely unaffected by NK-1 receptor antagonist treatment. In summary, our findings suggest that the protective effect of CP96,345 treatment is mediated by stabilization of the blood-brain barrier and suppression of Th1 immunity.

Adoptive Transfer↗
PubMed2006

Immunomodulatory synergy by combination of atorvastatin and glatiramer acetate in treatment of CNS autoimmunity.

One approach to improving efficacy in MS therapy is to identify medications that provide additive or synergistic benefit in combination. Orally administered cholesterol-lowering HMG-CoA reductase inhibitors (known as statins), which exhibit immunomodulatory properties and are effective in treatment of the MS model EAE, are being tested in MS. As atorvastatin can enhance protective Th2 responses and has a different mechanism of action than glatiramer acetate (GA), a parenterally administered immunomodulatory agent approved for MS treatment, we tested whether the combination of these agents could be beneficial in EAE. Combination therapy using suboptimal doses of atorvastatin and GA prevented or reversed clinical and histologic EAE. Secretion of proinflammatory Th1 cytokines was reduced--and conversely Th2 cytokine secretion was increased--in these mice, but not in mice treated with each drug alone at the same doses. Monocytes treated with the combination of suboptimal doses of atorvastatin and GA secreted an antiinflammatory type II cytokine pattern and, when used as APCs, promoted Th2 differentiation of naive myelin-specific T cells. Our results demonstrate that agents with different mechanisms of immune modulation can combine in a synergistic manner for the treatment of CNS autoimmunity and provide rationale for testing the combination of atorvastatin and GA in MS.

Animals↗
PubMed2006

Altered CD4+/CD8+ T-cell ratios in cerebrospinal fluid of natalizumab-treated patients with multiple sclerosis.

BACKGROUND: Treatment with natalizumab, a monoclonal antibody against the adhesion molecule very late activation antigen 4, an alpha4beta(1) integrin, was recently associated with the development of progressive multifocal leukoencephalopathy, a demyelinating disorder of the central nervous system caused by JC virus infection. OBJECTIVE: To test the effect of natalizumab treatment on the CD4(+)/CD8(+) T-cell ratios in cerebrospinal fluid (CSF) and peripheral blood. DESIGN: Prospective longitudinal study. SETTING: Academic and private multiple sclerosis centers. PATIENTS: Patients with multiple sclerosis (MS) treated with natalizumab, untreated patients with MS, patients with other neurologic diseases, and human immunodeficiency virus-infected patients. MAIN OUTCOME MEASURES: CD4(+) and CD8(+) T cells were enumerated in CSF and peripheral blood. The mean fluorescence intensity of unbound alpha4 integrin on peripheral blood CD4(+) and CD8(+) T cells was analyzed before and after natalizumab therapy. RESULTS: Natalizumab therapy decreased the CSF CD4(+)/CD8(+) ratio of patients with MS to levels similar to those of human immunodeficiency virus-infected patients. CD4(+)/CD8(+) ratios in peripheral blood in patients with MS progressively decreased with the number of natalizumab doses, but they remained within normal limits. Six months after the cessation of natalizumab therapy, CSF CD4(+)/CD8(+) ratios normalized. The expression of unbound alpha4 integrin on peripheral blood T cells decreases with natalizumab therapy and was significantly lower on CD4(+) vs CD8(+) T cells. CONCLUSIONS: Natalizumab treatment alters the CSF CD4(+)/CD8(+) ratio. Lower expression of unbound alpha4 integrin on CD4(+) T cells is one possible mechanism. These results may have implications for the observation that some natalizumab-treated patients with MS developed progressive multifocal leukoencephalopathy.

Adolescent↗
PubMed2006

Immune surveillance in multiple sclerosis patients treated with natalizumab.

OBJECTIVE: Our objective was to test whether natalizumab, an antibody against very late activating antigen (VLA)-4, interferes with central nervous system immune surveillance as assessed by leukocyte cell numbers and cellular phenotypes in cerebrospinal fluid (CSF) and peripheral blood. METHODS: Cell numbers and cellular phenotypes in CSF and peripheral blood were analyzed in multiple sclerosis (MS) patients treated with natalizumab, untreated MS patients, and patients with other neurological disease (OND). JC virus DNA in the CSF and peripheral blood was quantified by kinetic polymerase chain reaction. RESULTS: CSF leukocyte counts, CD4(+) and CD8(+) T cells, CD19(+) B cells, and CD138(+) plasma cells were significantly lower in natalizumab-treated MS patients compared with OND patients and untreated MS patients. JC virus DNA was not detected in CSF or peripheral blood from natalizumab-treated patients. Six months after cessation of natalizumab therapy, low lymphocyte counts in the CSF persisted. The patient with the highest total leukocyte and CD4(+) and CD8(+)T-cell counts in the CSF experienced a clinical relapse. INTERPRETATION: These data suggest that natalizumab treatment results in a prolonged decrease of lymphocytes in the CSF and are consistent with the hypothesis that natalizumab impairs immune surveillance of the central nervous system.

Adult↗
PubMed2006

Multiple sclerosis and the autonomic nervous system.

Symptoms related to alterations of the autonomic nervous system are frequent in patients with multiple sclerosis (MS). Bladder or bowel dysfunction or impairment of sexual performance is highly distressing for most MS patients,whereas the clinical relevance of other autonomic symptoms is less clear. Cardiovascular autonomic alterations might relate to clinical signs such as orthostatic intolerance; a relationship with fatigue is uncertain. However, the frequency of abnormal findings in tests for the cardiovascular autonomic system varies due to the lack of standardized test performance or differentially used cut-off values. The incidence of additional symptoms such as pupillomotor or sweating alterations and especially their relationship to overall autonomic nervous system abnormalities is not well known. Although their impact on daily life is low, they can at least serve as diagnostic tools. Beside these clinical aspects, alterations of the autonomic nervous system have also been reported to alter immunological cascades in experimental conditions. However, corresponding results have not been confirmed in clinical trials yet.

Autonomic Nervous System↗
PubMed2006

High throughput analysis of TCR-beta rearrangement and gene expression in single T cells.

Analysis of T-cell receptor beta chain (TCR-beta) rearrangement is essential to investigate T-cell responses in human autoimmune diseases, infection and cancer. Since the TCR-beta locus contains 55 variable (V) region gene segments, multiple assays have been necessary to determine TCR-beta rearrangements of individual T cells. We established a seminested rtPCR method for single T-cell analysis with two sets of degenerate primers covering 76 and 24% of the TCR-Vbeta genes, respectively. The specificity of the approach was validated by screening cDNAs obtained from T-cell clones (TCC) with defined TCR-beta rearrangement. We applied the method successfully to profile TCR-beta rearrangement of single T cells sorted from body fluids or dissected tissue. Concomitant analysis of other gene transcripts allowed determining phenotype and function of TCR-beta-defined single T cells. Our fast, cost-efficient and high throughput approach will facilitate studies on T-cell responses in human diseases.

Brain Neoplasms↗
PubMed2006

Immunopathogenesis and immunotherapy of multiple sclerosis.

Multiple sclerosis (MS) is a chronic disease of the CNS that is characterized by inflammation, demyelination and axonal injury. Although the etiology of MS is still unknown, many findings point toward a central role for the immune system in the pathogenesis of the disease. This hypothesis is strongly supported by the beneficial effects of immunomodulatory and immunosuppressive therapy on disease activity. Over the past few years, substantial progress has been made in deciphering the immune response in MS. Although animal models have advanced our knowledge of basic mechanisms of immune responses in the CNS, recent studies have also highlighted the differences between MS and its animal equivalent, experimental autoimmune encephalomyelitis. New immunotherapeutic agents have been developed and evaluated in clinical trials. Here, we review current knowledge of the immunopathogenesis of MS and corresponding animal models of disease, and discuss new immunointerventional treatment strategies based on changing pathogenetic concepts.

Animals↗
PubMed2006

Central nervous system infections - a potential complication of systemic immunotherapy.

PURPOSE OF REVIEW: Multiple sclerosis is a chronic inflammatory disease of the central nervous system, characterized by demyelination and axonal damage. With the emergence of more efficient immune therapies, severe sometimes even fatal central nervous system infections were observed. This review will address the role of the systemic immune system in central nervous system immune surveillance and discuss implications for the development of novel immunotherapies in multiple sclerosis. RECENT FINDINGS: In the last decade, a number of immunosuppressive and immunomodulatory agents have been approved for the treatment of multiple sclerosis, based on the results of double-blind placebo-controlled randomized clinical trials. A better understanding of the pathogenesis of the disease has prompted exploration of the therapeutic utility of new drugs that more potently disrupt the pathophysiological cascade of events that culminates in central nervous system tissue damage. One potential side-effect of these newer therapies is their interference with the control of central nervous system infections by the immune system. SUMMARY: Any increase in potency of multiple sclerosis therapies could well interfere with protective immunosurveillance of the central nervous system. One possible outcome is an increased incidence of opportunistic infections. A heightened vigilance for central nervous system infections in the setting of immunosuppression is necessary to prevent serious side-effects in the future.

Central Nervous System↗
PubMed2005

Chemokines in multiple sclerosis: CXCL12 and CXCL13 up-regulation is differentially linked to CNS immune cell recruitment.

Understanding the mechanisms of immune cell migration to multiple sclerosis lesions offers significant therapeutic potential. This study focused on the chemokines CXCL12 (SDF-1) and CXCL13 (BCA-1), both of which regulate B cell migration in lymphoid tissues. We report that immunohistologically CXCL12 was constitutively expressed in CNS parenchyma on blood vessel walls. In both active and chronic inactive multiple sclerosis lesions CXCL12 protein was elevated and detected on astrocytes and blood vessels. Quantitative PCR demonstrated that CXCL13 was produced in actively demyelinating multiple sclerosis lesions, but not in chronic inactive lesions or in the CNS of subjects who had no neurological disease. CXCL13 protein was localized in perivascular infiltrates and scattered infiltrating cells in lesion parenchyma. In the CSF of relapsing-remitting multiple sclerosis patients, both CXCL12 and CXCL13 were elevated. CXCL13, but not CXCL12, levels correlated strongly with intrathecal immunoglobulin production as well as the presence of B cells, plasma blasts and T cells. About 20% of CSF CD4+ cells and almost all B cells expressed the CXCL13 receptor CXCR5. In vitro, CXCL13 was produced by monocytes and at much higher levels by macrophages. CXCL13 mRNA and protein expression was induced by TNFalpha and IL-1beta but inhibited by IL-4 and IFNgamma. Together, CXCL12 and CXCL13 are elevated in active multiple sclerosis lesions and CXCL12 also in inactive lesions. The consequences of CXCL12 up-regulation could be manifold. CXCL12 localization on blood vessels indicates a possible role in leucocyte extravasation, and CXCL12 may contribute to plasma cell persistence since its receptor CXCR4 is retained during plasma cell differentiation. CXCL12 may contribute to axonal damage as it can become a neurotoxic mediator of cleavage by metalloproteases, which are present in multiple sclerosis lesions. The strong linkage of CXCL13 to immune cells and immunoglobulin levels in CSF suggests that this is one of the factors that attract and maintain B and T cells in inflamed CNS lesions. Therefore, both CXCL13 and CXCR5 may be promising therapeutic targets in multiple sclerosis.

Acute Disease↗
PubMed2005

High level of cross-reactivity in influenza virus hemagglutinin-specific CD4+ T-cell response: implications for the initiation of autoimmune response in multiple sclerosis.

Viral infections play a role in shaping and maintaining the peripheral T-cell repertoire, as well as in the initiation of autoimmune response via mechanisms of molecular mimicry. In this study, we addressed the flexibility of T-cell receptor (TCR) recognition and the degree of structural and sequence homology required for cross-reactive immune response in the induction of autoimmune response. We studied the extent of cross-reactivity of a CD4+T-cell clone (TCC) specific for the immunodominant influenza virus hemagglutinin (Flu-HA) peptide derived from a patient with multiple sclerosis (MS) using positional scanning synthetic peptide combinatorial libraries (PS-SCL). We documented cross-reactivity against 14 Flu-HA variants, 11 viral, 15 human, and 3 myelin-derived peptides. Moreover, we identified six naturally occurring peptides with higher stimulatory potency than the native ligand, implicating high potential for cross-reactivity even for a virus-specific memory TCC. Our study demonstrates that flexibility of TCR recognition is present even in a clone with a high degree of TCR specificity for an infectious agent. The results have implications for vaccine design and for antigen-specific treatment strategies for autoimmune diseases.

CD4-Positive T-Lymphocytes↗
PubMed2005

Identification of Epstein-Barr virus proteins as putative targets of the immune response in multiple sclerosis.

MS is a chronic inflammatory and demyelinating disease of the CNS with as yet unknown etiology. A hallmark of this disease is the occurrence of oligoclonal IgG antibodies in the cerebrospinal fluid (CSF). To assess the specificity of these antibodies, we screened protein expression arrays containing 37,000 tagged proteins. The 2 most frequent MS-specific reactivities were further mapped to identify the underlying high-affinity epitopes. In both cases, we identified peptide sequences derived from EBV proteins expressed in latently infected cells. Immunoreactivities to these EBV proteins, BRRF2 and EBNA-1, were significantly higher in the serum and CSF of MS patients than in those of control donors. Oligoclonal CSF IgG from MS patients specifically bound both EBV proteins. Also, CD8(+) T cell responses to latent EBV proteins were higher in MS patients than in controls. In summary, these findings demonstrate an increased immune response to EBV in MS patients, which suggests that the virus plays an important role in the pathogenesis of disease.

Antibodies↗
PubMed2005

Short-lived plasma blasts are the main B cell effector subset during the course of multiple sclerosis.

Multiple sclerosis is a chronic inflammatory and demyelinating disorder of the CNS with an unknown aetiology. Although intrathecal immunoglobulin G (IgG) synthesis is a key feature of the disease, little is still known about the B cell response in the CNS of multiple sclerosis patients. We analysed the phenotype and kinetics of different B cell subsets in patients with multiple sclerosis, infectious disease (IND) and non-inflammatory neurological disease (NIND). B cells were detected in the CSF of multiple sclerosis and IND patients, but were largely absent in NIND patients. In the CSF, the majority of B cells had a phenotype of memory B cells and short-lived plasma blasts (PB); plasma cells were absent from the compartment. The proportion of PB was highest in multiple sclerosis patients and patients with acute CNS infection. While PB disappeared rapidly from the CSF after resolution of infection in IND patients, these cells were present at high numbers throughout the disease course in multiple sclerosis patients. CSF PB numbers in multiple sclerosis patients strongly correlated with intrathecal IgG synthesis and inflammatory parenchymal disease activity as disclosed by MRI. This study identifies short-lived plasma blasts as the main effector B cell population involved in ongoing active inflammation in multiple sclerosis patients.

B-Lymphocytes↗
PubMed2005

Clinical stabilization and effective B-lymphocyte depletion in the cerebrospinal fluid and peripheral blood of a patient with fulminant relapsing-remitting multiple sclerosis.

BACKGROUND: The anti-CD20 monoclonal antibody rituximab effectively depletes B lymphocytes and has been successfully used in the therapy of immune-mediated disorders of the peripheral nervous system. A limited effect of rituximab on B lymphocytes in the cerebrospinal fluid compartment of patients with primary progressive multiple sclerosis (MS) was recently reported. OBJECTIVE: To determine the effect of rituximab on clinical, magnetic resonance imaging, and immunological variables in a patient with relapsing-remitting MS. DESIGN: A patient with relapsing-remitting MS was treated with rituximab. The patient was repeatedly examined clinically and by magnetic resonance imaging. The frequency of peripheral blood and cerebrospinal fluid B lymphocytes was assessed by flow cytometry before, during, and after rituximab therapy. RESULTS: Rituximab monotherapy resulted in significant clinical improvement. Inflammatory surrogate markers on magnetic resonance imaging were also reduced. B lymphocytes were depleted in the cerebrospinal fluid and peripheral blood. CONCLUSIONS: Our data demonstrate beneficial clinical effects of rituximab in relapsing-remitting MS, mediated through modulation of humoral systemic and central nervous system intrinsic immune responses. Clinical trials should determine optimal therapeutic strategies for patients with relapsing-remitting MS.

Adult↗
PubMed2005

Acute disseminated encephalomyelitis: an update.

Acute disseminated encephalomyelitis (ADEM) is a monophasic autoimmune demyelinating disease of the central nervous system that typically follows a febrile infection or a vaccination. Children are predominantly affected. A plethora of viral and bacterial pathogens and a number of vaccinations have been associated with ADEM. Experimental animal studies indicate that both primary and secondary autoimmune responses contribute to central nervous system inflammation and subsequent demyelination. The clinical diagnosis of ADEM is strongly suggested by a close temporal relationship between an infectious incident or an immunization and the onset of leukoencephalopathic neurological symptoms. Paraclinical tests may support the diagnosis. Particularly helpful are acute signs of newly developed extensive, multifocal, subcortical white matter abnormalities on magnetic resonance images of the brain. The cerebrospinal fluid may disclose a mild lymphocytic pleocytosis and elevated albumin levels. Oligoclonal bands are not always present in ADEM and, if so, may be transient. The major differential diagnosis of ADEM is multiple sclerosis. Treatment options for ADEM consist of anti-inflammatory and immunosuppressive agents. In general, the disease is self-limiting and the prognostic outcome favorable. In the absence of widely accepted clinical or paraclinical diagnostic guidelines, a number of recently conducted observational case series have substantially broadened our understanding about the clinical phenotype, diagnosis, and prognosis of ADEM.

Acute Disease↗