The selective sphingosine 1-phosphate receptor modulator BAF312 redirects lymphocyte distribution and has species-specific effects on heart rate

BACKGROUND AND PURPOSE

BAF312 is a next-generation sphingosine 1-phosphate (S1P) receptor modulator, selective for S1P₁ and S1P₅ receptors. S1P₁ receptors are essential for lymphocyte egress from lymph nodes and a drug target in immune-mediated diseases. Here, we have characterized the immunomodulatory potential of BAF312 and the S1P receptor-mediated effects on heart rate using preclinical and human data.

EXPERIMENTAL APPROACH

BAF312 was tested in a rat experimental autoimmune encephalomyelitis (EAE) model. Electrophysiological recordings of G-protein-coupled inwardly rectifying potassium (GIRK) channels were carried out in human atrial myocytes. A Phase I multiple-dose trial studied the pharmacokinetics, pharmacodynamics and safety of BAF312 in 48 healthy subjects.

KEY RESULTS

BAF312 effectively suppressed EAE in rats by internalizing S1P₁ receptors, rendering them insensitive to the egress signal from lymph nodes. In healthy volunteers, BAF312 caused preferential decreases in CD4⁺ T cells, T_naïve, T_{central memory} and B cells within 4–6 h. Cell counts returned to normal ranges within a week after stopping treatment, in line with the elimination half-life of BAF312. Despite sparing S1P₃ receptors (associated with bradycardia in mice), BAF312 induced rapid, transient (day 1 only) bradycardia in humans. BAF312-mediated activation of GIRK channels in human atrial myocytes can fully explain the bradycardia.

CONCLUSION AND IMPLICATIONS

This study illustrates species-specific differences in S1P receptor specificity for first-dose cardiac effects. Based on its profound but rapidly reversible inhibition of lymphocyte trafficking, BAF312 may have potential as a treatment for immune-mediated diseases.

RGMA and IL21R show association with experimental inflammation and multiple sclerosis

Rat chromosome 1 harbors overlapping quantitative trait loci (QTL) for cytokine production and experimental models of inflammatory diseases. We fine-dissected this region that regulated cytokine production, myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), anti-MOG antibodies and pristane-induced arthritis (PIA) in advanced intercross lines (AILs). Analysis in the tenth and twelfth generation of AILs resolved the region in two narrow QTL, Eae30 and Eae31. Eae30 showed linkage to MOG-EAE, anti-MOG antibodies and levels of interleukin-6 (IL-6). Eae31 showed linkage to EAE, PIA, anti-MOG antibodies and levels of tumor necrosis factor (TNF) and IL-6. Confidence intervals defined a limited set of potential candidate genes, with the most interesting being RGMA, IL21R and IL4R. We tested the association with multiple sclerosis (MS) in a Nordic case-control material. A single nucleotide polymorphism in RGMA associated with MS in males (odds ratio (OR)=1.33). Polymorphisms of RGMA also correlated with changes in the expression of interferon-gamma (IFN-gamma) and TNF in cerebrospinal fluid of MS patients. In IL21R, there was one positively associated (OR=1.14) and two protective (OR=0.87 and 0.68) haplotypes. One of the protective haplotypes correlated to lower IFN-gamma expression in peripheral blood mononuclear cells of MS patients. We conclude that RGMA and IL21R and their pathways are crucial in MS pathogenesis and warrant further studies as potential biomarkers and therapeutic targets.

Evaluation of conversion coefficients from measurable to risk quantities for external exposure over contaminated soil by use of physical human phantoms

Conversion coefficients from measurable quantities such as air kerma free-in-air or personal dose equivalent to effective dose were determined by phantom experiments. Heterogenic anthropomorphic phantoms representing children of one and five years age, and a Rando phantom representing an adult were exposed in the open field contaminated by different levels of radiocesium in the upper soil layer, in a forest site and inside a wooden house. LiF thermoluminescent (TL) detectors were used inside the phantoms for the estimation of organ doses and effective dose. Personal dosimeters similar to those used in radiation protection for individual dose measurements were placed onto the phantom surface (chest area). The ratios of dose values in separate organs to air kerma free-in-air varied from 0.69 to 1.15 for the children phantoms, and from 0.55 to 0.94 for the adult phantom, respectively, when irradiated in the open field. Body size (weight) was found to be the most important factor influencing the values of the conversion coefficients. The differences observed can reach approximately 40% when comparing conversion factors from air kerma free-in-air to effective dose for adults and newborns. For conversion coefficients from personal dose to effective dose, these differences can reach approximately 15%. The dependences of the various conversion coefficients on body mass were quantified by regression analysis. The results were compared with those calculated for a plane mono-energetic photon source having an energy of 700 keV and being located in the ground at a depth of 0.5 g cm(-2). Calculated and measured conversion coefficients from air kerma free-in-air to effective dose agreed within 12%.

No signs of immunoactivation in the cerebrospinal fluid during treatment with infliximab

Neuroinflammatory (demyelinating) disease is a rare but feared complication of treatment with anti-tumour necrosis factor (TNF)alpha in patients with polyarthritis. In this study, blood and cerebrospinal fluid markers of inflammation were analysed in 10 people with polyarthritis before and during treatment with infliximab. An increased systemic expression of interferon (IFN)gamma was detected. Systemic administration of IFNgamma is known to exacerbate multiple sclerosis. However, the present study failed to detect signs of inflammation in the cerebrospinal fluid samples-that is, pleocytosis, oligoclonal immunoglobulin G bands, increased expression of IFNgamma, TNFalpha or interleukin 10, or increased levels of nitric oxide oxidation products. Our initial hypothesis, that the few cases of clinical neuroinflammatory disorders observed during treatment of polyarthritis with anti-TNFalpha represent the extreme end of a commonly occurring minor intrathecal immune activation, which in most cases does not give any overt neurological dysfunction, was not supported. Induction of systemic IFNgamma production may still be relevant in neuroinflammation associated with treatment with anti-TNFalpha.

Autoimmunity to myelin oligodendrocyte glycoprotein in rats mimics the spectrum of multiple sclerosis pathology

Multiple sclerosis is a chronic inflammatory disease characterized by perivenous inflammation and focal destruction of myelin. Many attempts have been undertaken previously to create animal models of chronic inflammatory demyelinating diseases through autoimmunity or virus infection. Recently, however, a new model of myelin oligodendrocyte glycoprotein (MOG) induced autoimmune encephalomyelitis became available, which, in a very standardized and predictable way, leads to chronic (relapsing or progressive) disease and widespread CNS demyelination. In the present study we actively induced MOG-experimental autoimmune encephalomyelitis (EAE) in different inbred rat strains using different immunization protocols. The pathology found in our models closely reflects the spectrum of multiple sclerosis (MS) pathology: Classical MS as well as variants such as optic neuritis, Devic's disease and Marburg's type of acute MS are mimicked in rats immunized with MOG antigen. Furthermore we demonstrate, that by using the proper strain/sensitization regime, subforms of MS such as for instance neuromyelitis optica can be reproducibly induced. Our study further supports the notion, that incidence and expression of the disease in this model, alike the situation in multiple sclerosis, is determined by genetic and environmental factors.

External and internal irradiation of a rural Bryansk (Russia) population from 1990 to 2000, following high deposition of radioactive caesium from the Chernobyl accident

In 1990, a joint Nordic-Russian project was initiated in order to make independent estimations of the effective dose to selected groups of inhabitants in a highly contaminated area around the city of Novozybkov in the western Bryansk region of Russia. The inhabitants were living in six villages with initial contamination levels of (137)Cs between 0.9 and 2.7 MBq m(-2). Some villages had been decontaminated, others not. Both school children and adults participated in the study. The external irradiation of 100-130 inhabitants was determined during 1 month in September-October each year from 1990 to 2000 (except 1999), using individual thermoluminescent dosemeters. The body burden of (137,134)Cs was determined by in vivo measurements in about 500 inhabitants annually from 1991 to 2000, and for a subgroup also with analysis of the (137)Cs concentration in urine. The mean effective dose (E) from external and internal irradiation due to (137,134)Cs deposition varied between 2.5 and 1.2 mSv per year between 1990 and 2000. The total mean E decreased, on average, by 9% per year, while the mean external dose decreased by 16% per year. The dose rate from internal radiation decreased more slowly than the dose rate from external radiation, and also showed an irregular time variation. The contribution from the internal dose to the total E was 30-50%, depending on the village. Predictions for the long-term changes in the effective dose to people living in the areas are presented. The cumulated E for the 70 years following the accident was estimated to be about 90 mSv with the assumption that both internal and external dose decrease by 2% per year after year 2000. The highest E during a life-time received by single individuals living in the area may amount to around 500 mSv considering the individual variations in E.

Current Gene-Mapping Strategies in Experimental Models of Multiple Sclerosis

Both family-based linkage analyses and population-based association studies have failed to identify disease-regulatory non-human leucocyte antigen genes of importance in multiple sclerosis (MS). Instead, investigators have employed experimental models, which offer major advantages in genetic studies. We summarize the current main methodologies used and the status of both the human and experimental approaches. Why is it important to find genes regulating MS? There is an immense number of cellular and molecular interactions defined in the immunological field and it is very difficult to unravel those that are critical to an inflammatory disease, such as MS, by classical hypothesis-driven research. Unbiased genetics defines evolutionary conserved gene polymorphisms and pathways regulated by these genes, which are central in the pathogenesis. These, in turn, are of interest as therapeutic targets and pharmacogenetic markers.

Depletion of Vbeta5.2/5.3 T cells with a humanized antibody in patients with multiple sclerosis

A potentially pathogenic expansion of T cells expressing T cell receptor (TCR) Vbeta5.2/5.3 has been demonstrated in patients with multiple sclerosis (MS). A humanized antibody (ATM-027) directed against these T cells has been developed to further investigate the role of this subpopulation of T cells in MS. The pharmacokinetics/dynamics and safety of ATM-027 (0.3-300 mg intravenously over 30 min) were investigated in 14 patients with MS. The effect of treatment on cytokine expression and autoreactivity to peptides of myelin basic protein (MBP) was also studied. ATM-027 was well tolerated and raised no safety concerns. Clearance of the antibody was low and elimination half-life was approximately 3 weeks. The majority of the target Vbeta5.2/5.3 expressing T cells were depleted for at least 18 months. The small remaining fraction of target cells showed a marked decrease in their TCR expression, which was recovered within 8 months. The numbers of peripheral blood mononuclear cells (PBMCs) with spontaneous expression of IFN-gamma was decreased at 72 h and 8 weeks after treatment, whilst no clear effects on TNF-alpha, IL-4, IL-10, TGF-beta expression were observed. There was also a significant decrease in the number of PBMCs producing IFN-gamma in response to MBP peptide 80-102. We conclude that long-term depletion of T cells expressing defined Vbeta subgroups in MS patients is feasible using selective immunotherapy. The selective depletion of Vbeta5.2/5.3 expressing T cells in this study resulted in a decrease in potentially disease promoting anti-MBP reactivity and pro-inflammatory cytokine production.

Long-term external radiation exposure of inhabitants in the western Bryansk region of Russia as a consequence of the Chernobyl accident

The western Bryansk region in south-western Russia was highly contaminated with 137Cs and 134Cs due to the Chernobyl accident in 1986. In 1990, a joint Nordic-Russian project was initiated in order to make measurements and estimates of the absorbed doses to selected groups of inhabitants in this area. The participating individuals were living in small villages with contamination levels between 0.9 and 2.7 MBq m(-2). Only some villages had been decontaminated. Both school-children and adults participated in the study and the number of persons was between 100 and 130 each year, residing in 5 villages. Every year in September-October, from 1990 to 1998. we performed individual measurements of external absorbed doses, assessed with thermoluminescent (TL) dosemeters (LiF). The mean effective dose per year from external irradiation due to the Chernobyl accident of the inhabitants in the villages ranged between 0.8 and 2.9 mSv during the study period and decreased with an apparent half-time of 3.7-8.2 years, depending on village and group. The highest individual doses within one village were, on average higher by a factor of 3 than the mean value for that village. Under the conservative assumption of a decrease rate in the external effective dose of 2% per year after 1998, individuals in the most highly exposed village are assumed to receive a life-time effective dose of about 75 mSv (between 1986 and 2056) from external exposure to caesium radionuclides. The mean value for the villages under study was estimated to be around 65 mSv using the assumed rate of decrease.

Polygenic control of autoimmune peripheral nerve inflammation in rat

Experimental autoimmune neuritis (EAN) is the principal animal model for Guillain-Barré syndrome (GBS), an inflammatory disease of the peripheral nervous system. Little is known on the genetic regulation of these diseases. We provide the first genetic linkage analysis of EAN. Susceptibility to EAN in a rat F2 population segregated with high levels of anti-PNM IgG, as well as IgG2b and IgG2c isotype levels, which support that disease genes regulate preferential Th1/Th2 differentiation. Linkage analysis demonstrated co-localization of EAN loci with reported susceptibility loci for experimental arthritis and/or encephalomyelitis and a new region on chromosome 17. Further dissection of these loci may disclose disease pathways in GBS.

Screening of several H-2 congenic mouse strains identified H-2(q) mice as highly susceptible to MOG-induced EAE with minimal adjuvant requirement

We identified H-2(q) as a susceptible genotype for MOG-induced EAE by systematic screening of a series of H-2 congenic B10 mouse strains. A series of H-2(q)-bearing strains with divergent gene backgrounds were subsequently investigated. DBA/1 mice were highly susceptible to MOG(1-125)- and MOG(79-96)-induced EAE in the absence of pertussis toxin. Immunisation with MOG(1-125) and MOG(79-96) induced an autoreactive T-cell response in DBA/1 mice. Brain histopathology revealed T-cell and macrophage-infiltrated lesions with associated demyelination. The important features which make this an appropriate model of human disease are high sensitivity to MOG and dependence of an immunodominant peptide region homologous to that implicated in multiple sclerosis.

Genetics of rat neuroinflammation

The definition of genes regulating the pathogenetic pathways of autoimmune neuroinflammation, may provide targets for new therapeutic strategies. This is not easily accomplished in human disease. Such genetic dissection can more readily be done by the use of inbred rodent strains. With these, genetic heterogeneity is avoided and variation in the environmental influences is minimized. Close mimicking of the human disease characteristics is desirable in such endeavors. Chronic relapsing experimental autoimmune encephalomyelitis (EAE) with MS-like histopathology is achieved after immunization of certain rat strains with myelin oligodendrocyte glycoprotein (MOG) or spinal cord homogenate. The major histocompatibility complex (MHC) regulate the ease by which the environmental trigger in the form of immunisation induces disease. Use of intra-MHC recombinant strains demonstrated major influences from the MHC class II genome region, but additional influences from both the MHC class I and III regions. These findings now provide a basis for studies of the mechanisms for MHC-controlled autoimmune pathogenicity leading to MS-like disease. Gene mapping of F2 crosses between susceptible and resistant rat strains demonstrated nine genome regions outside the MHC which regulate different phenotypes of rat EAE. Many of these co-localize with genome regions regulating other organ-specific disease such experimental arthritis, suggesting a sharing of disease pathways. Further finemapping can lead to the exact identification of disease regulating genes. Interestingly, we have also demonstrated a non-MHC gene control of the inflammatory response, in the form of glial cell activation, and neuronal degeneration, subsequent to anterior nerve root avulsion in rats. The genetic dissection of these influences may unravel pathways controlling CNS vulnerability.

Reduction of both pro- and anti-inflammatory cytokines after 6 months of interferon beta-1a treatment of multiple sclerosis

Treatment of multiple sclerosis (MS) with interferon beta (IFNbeta) reduces relapse rate, magnetic resonance imaging (MRI) activity and progression of disability. It has been suggested that this beneficial effect is paralleled by an inhibition of proinflammatory cytokines such as interferon gamma (IFNgamma) and tumor necrosis factor alpha (TNFalpha) and an induction of anti-inflammatory cytokines such as interleukin-4 (IL-4) and interleukin-10 (IL-10). In this study, we record a reduced number of spontaneously IFNgamma mRNA-expressing cerebrospinal fluid mononuclear cells (CSF-MC) and IFNgamma, TNFalpha and IL-10 mRNA-expressing peripheral blood mononuclear cells (PBMC) after 6 months of IFNbeta-1a treatment, paralleled by a decreased purified protein derivate (PPD)-stimulated and unstimulated IFNgamma secretion by PBMC. These effects were not apparent after 2 weeks of treatment, and IFNbeta-1a induced IFNgamma production by naive PBMC in vitro. We did not record increased numbers of IL-4 mRNA-expressing CSF-MC or PBMC, increased plasma IL-10 levels, increased numbers of IgG, A or M secreting plasma cells or in vitro induction of IL-10 production by IFNbeta-1a. We conclude that long-term cytokine modulation by IFNbeta-1a differs from acute effects and that downregulation of both pro- and anti-inflammatory cytokines, rather than a shift in the cytokine profile, is apparent after 6 months of IFNbeta-1a treatment of MS patients.

Increased numbers of mononuclear cells from blood and CSF expressing interferon-gamma mRNA in multiple sclerosis are from both the CD4+ and the CD8+ subsets

Activated, cytokine-producing lymphocytes may regulate central nervous system (CNS) inflammation in multiple sclerosis (MS). We utilize a novel combination of in situ hybridization (ISH) and immunocytochemical staining of peripheral blood lymphocytes (PBLs) to identify spontaneously interferon-gamma (IFNgamma) mRNA expressing cells as CD4+ or CD8+. A major proportion of the IFNgamma mRNA expressing lymphocytes belonged to the CD4+ lineage, which concords with the cellular composition of MS brain lesions, findings in experimental models and the HLA class II haplotype association in MS. There were also significantly more CD8+ IFNgamma mRNA expressing lymphocytes in the MS patients compared with healthy controls, further suggesting the contribution of activated cells from this lineage in the inflammatory response in MS. Both CD4+ and CD8+ IFNgamma mRNA expressing cells were enriched in the cerebrospinal fluid (CSF) as compared with the peripheral blood of the MS patients. Combined with emerging genetic data on HLA class I influences, our data argues for a joint role of activated CD8+ and CD4+ cells in the pathogenesis of MS.

Linkage analysis of myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis in the rat identifies a locus controlling demyelination on chromosome 18

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system (CNS) with a complex etiology comprising a genetically determined predisposition and a suspected auto- immune pathogenesis. Experimental autoimmune encephalomyelitis (EAE) is an animal model for MS, which can be used to define susceptibility loci for autoimmune neuroinflammation. We have recently established a chronic relapsing EAE model characterized by inflammation and focal demyelination in the CNS by immunizing a variety of rat strains with the CNS-specific myelin oligodendrocyte glycoprotein (MOG). This model is more MS-like than any other rodent EAE model described up to now. Here we present the first systematic genome search for chromosomal regions linked to phenotypes of MOG-induced EAE in a (DA x ACI) F(2)intercross. A genome-wide significant susceptibility locus linked to demyelination was identified on chromosome 18. This region has not been described in inflammatory diseases affecting other organs and the responsible gene or genes may thus be nervous system specific. Other chromosomal regions showing suggestive linkage to phenotypes of MOG-induced EAE were identified on chromosomes 10, 12 and 13. The chromosome 10 and 12 regions have previously been linked to arthritis in DA rats, suggesting that they harbour immunoregulatory genes controlling general susceptibility to autoimmune diseases. We conclude that identification of susceptibility genes for MOG-induced EAE on rat chromosomes 10, 12, 13 and 18 may disclose important disease pathways for chronic inflammatory demyelinating diseases of the CNS such as MS.

A gamma camera for measurements of internal contamination after a radiological accident

After a radiological accident with the release of large amounts of radionuclides into the environment, measurements of the external and internal exposure of the public will be urgently required. The aim of this study was to investigate the properties of a gamma camera with regard to measurements of internal contamination. The gamma camera was used as a detector without any imaging function. The lowest minimum detectable activity, 100 Bq 131I in thyroid measured over the neck and 400 Bq 137Cs in the whole body measured over the trunk (1 min measuring time), was found when using the lowest (50 keV-450 keV) energy interval among the three investigated (also 550-750 keV and 450-550 keV), in measurements without a collimator. The mechanical difficulties in handling a gamma camera without a collimator may also have to be considered. It is essential to pay attention to the influence of body size on both background and sensitivity. Provided proper calibrations are carried out and routines for measurements are established, a gamma camera is useful for fast identification and quantification of internal contamination with gamma-emitting radionuclides down to levels so low that in most situations they give a low contribution to the effective dose.

Increased reactivity to myelin oligodendrocyte glycoprotein peptides and epitope mapping in HLA DR2(15)+ multiple sclerosis

Multiple sclerosis (MS) is a central nervous system-specific inflammatory and demyelinating disease where a myelin-directed autoimmune response is thought to be pathogenetically relevant. Myelin oligodendrocyte glycoprotein (MOG) is a surface-exposed minor myelin component that is a prime candidate autoantigen. We have investigated peripheral blood lymphocyte responses to synthetic 15-26 amino acids long overlapping MOG peptides in 20 MS patients and 14 healthy controls with the MS-associated HLA haplotype DR2(15). There were significantly increased responses, in terms of numbers of cells secreting IFN-gamma detected by Elispot in response to several MOG-derived peptides in the MS patients, but not the healthy controls. MOG peptide 63-87 evoked the strongest response, and the stimulatory property of this peptide was confirmed in additional DR2(15)+ MS patients where a peptide concentration-dependent proliferative response, which was inhibited by the addition of anti-HLA class II antibodies, was observed. This is the first work detailing putative immunodominant T cell epitopes of MOG in DR2(15)+ MS patients.

MHC haplotype-dependent regulation of MOG-induced EAE in rats

Experimental autoimmune encephalomyelitis (EAE) induced in the rat by active immunization with myelin-oligodendrocyte-glycoprotein (MOG) is mediated by synergy between MOG-specific T cells and demyelinating MOG-specific antibody responses. The resulting disease is chronic and displays demyelinating central nervous system (CNS) pathology that closely resembles multiple sclerosis. We analyzed major histocompatibility complex (MHC) haplotype influences on this disease. The MHC haplotype does not exert an all-or-none effect on disease susceptibility. Rather, it determines the degree of disease susceptibility, recruitment of MOG-specific immunocompetent cells, clinical course, and CNS pathology in a hierarchical and allele-specific manner. Major haplotype-specific effects on MOG-EAE map to the MHC class II gene region, but this effect is modified by other MHC genes. In addition, non-MHC genes directly influence both disease and T cell functions, such as the secretion of IFN-gamma. Thus, in MOG-EAE, allelic MHC class II effects are graded, strongly modified by other MHC genes, and overcome by effects of non-MHC genes and environment.

Memantine abrogates neurological deficits, but not CNS inflammation, in Lewis rat experimental autoimmune encephalomyelitis

Memantine, a clinically employed drug with N-methyl-D-aspartate (NMDA) receptor antagonistic effects, dose-dependently ameliorates neurological deficits in Lewis rat experimental autoimmune encephalomyelitis (EAE). Interestingly, this therapeutic effect was not due to dampened CNS inflammation, as assessed by immunohistochemical evaluation of spinal cord tissue. Furthermore, numbers of interferon gamma (IFN gamma) mRNA expressing cells were not decreased, as assessed by in situ hybridization. Systemic immunity in terms of numbers of IFN gamma secreting cells in response to immunodominant myelin basic protein (MBP) peptides ex vivo was not reduced, and non-toxic doses of memantine did not affect lymphocyte proliferation or IFN gamma secretion in vitro. Considering these findings, we hypothesize that effector mechanisms responsible for reversible neurological deficits in EAE may involve NMDA receptors, and this highlights neurons as targets during autoimmune neuroinflammation.