The production of antibody by invading B cells is required for the clearance of rabies virus from the central nervous system.

BACKGROUND: The pathogenesis of rabies is associated with the inability to deliver immune effectors across the blood-brain barrier and to clear virulent rabies virus from CNS tissues. However, the mechanisms that facilitate immune effector entry into CNS tissues are induced by infection with attenuated rabies virus. METHODOLOGY/PRINCIPAL FINDINGS: Infection of normal mice with attenuated rabies virus but not immunization with killed virus can promote the clearance of pathogenic rabies virus from the CNS. T cell activity in B cell-deficient mice can control the replication of attenuated virus in the CNS, but viral mRNA persists. Low levels of passively administered rabies virus-neutralizing antibody reach infected cells in the cerebellum of B cell-deficient mice but are not sufficient to mediate virus clearance. Production of rabies virus-specific antibody by B cells invading CNS tissues is required for this process, and a substantial proportion of the B cells that accumulate in the CNS of mice infected with attenuated rabies virus produce virus-specific antibodies. CONCLUSIONS/SIGNIFICANCE: The mechanisms required for immune effectors to enter rabies virus-infected tissues are induced by infection with attenuated rabies virus but not by infection with pathogenic rabies viruses or immunization with killed virus. T cell activities can inhibit rabies virus replication, but the production of rabies virus-specific antibodies by infiltrating B cells, as opposed to the leakage of circulating antibody across the BBB, is critical to elimination of the virus. These findings suggest that a pathogenic rabies virus infection may be treatable after the virus has reached the CNS tissues, providing that the appropriate immune effectors can be targeted to the infected tissues.

Does somatostatin confer insulinostatic effects of neuromedin u in the rat pancreas?

OBJECTIVES: Neuromedin U (NmU) is a neuropeptide with anorexigenic activity. Two receptor subtypes (NmUR1 and NmUR2) confer the effects of NmU on target cells. We have recently demonstrated that NmU reduces insulin secretion from isolated pancreatic islets. Aim of our current study is to investigate the role of somatostatin at mediating the effects of NmU on insulin secretion. METHODS: Expression of NmU in the pancreas was detected by immunohistochemistry. Insulin and somatostatin secretion from in situ perfused rat pancreas and isolated pancreatic islets was measured by radioimmunoassay. The paracrine effects of somatostatin within pancreatic islets were blocked by cyclosomatostatin, a somatostatin receptor antagonist. RESULTS: Receptor subtype NmUR1, but not NmUR2, was expressed in the endocrine pancreas, predominantly in the periphery. Neuromedin U reduced insulin secretion from in situ perfused rat pancreas and stimulated somatostatin secretion from isolated pancreatic islets. Neuromedin U stimulated somatostatin secretion at both physiological and supraphysiological glucose concentrations. Cyclosomatostatin increased insulin secretion and reduced NmU-induced inhibition of insulin secretion. CONCLUSIONS: Neuromedin U reduces insulin and increases somatostatin secretion. Blockade of somatostatin action abolishes the inhibition of insulin secretion by NmU. The results of the study suggest that somatostatin mediates the inhibitory action of NmU on insulin secretion.

Blood-brain barrier changes and cell invasion differ between therapeutic immune clearance of neurotrophic virus and CNS autoimmunity.

CNS tissues are protected from circulating cells and factors by the blood-brain barrier (BBB), a specialization of the neurovasculature. Outcomes of the loss of BBB integrity and cell infiltration into CNS tissues can differ vastly. For example, elevated BBB permeability is closely associated with the development of neurological disease in experimental allergic encephalomyelitis (EAE) but not during clearance of the attenuated rabies virus CVS-F3 from the CNS tissues. To probe whether differences in the nature of BBB permeability changes may contribute to the pathogenesis of acute neuroinflammatory disease, we compared the characteristics of BBB permeability changes in mice with EAE and in mice clearing CVS-F3. BBB permeability changes are largely restricted to the cerebellum and spinal cord in both models but differ in the extent of leakage of markers of different size and in the nature of cell accumulation in the CNS tissues. The accumulation in the CNS tissues of CD4 T cells expressing mRNAs specific for IFN-gamma and IL-17 is common to both, but iNOS-positive cells invade into the CNS parenchyma only in EAE. Mice that have been immunized with myelin basic protein (MBP) and infected exhibit the features of EAE. Treatment with the peroxynitrite-dependent radical scavenger urate inhibits the invasion of iNOS-positive cells into the CNS tissues and the development of clinical signs of EAE without preventing the loss of BBB integrity in immunized/infected animals. These findings indicate that BBB permeability changes can occur in the absence of neuropathology provided that cell invasion is restricted.

A peroxynitrite-dependent pathway is responsible for blood-brain barrier permeability changes during a central nervous system inflammatory response: TNF-alpha is neither necessary nor sufficient.

Elevated blood-brain barrier (BBB) permeability is associated with both the protective and pathological invasion of immune and inflammatory cells into CNS tissues. Although a variety of processes have been implicated in the changes at the BBB that result in the loss of integrity, there has been no consensus as to their induction. TNF-alpha has often been proposed to be responsible for increased BBB permeability but there is accumulating evidence that peroxynitrite (ONOO(-))-dependent radicals may be the direct trigger. We demonstrate here that enhanced BBB permeability in mice, whether associated with rabies virus (RV) clearance or CNS autoimmunity, is unaltered in the absence of TNF-alpha. Moreover, the induction of TNF-alpha expression in CNS tissues by RV infection has no impact on BBB integrity in the absence of T cells. CD4 T cells are required to enhance BBB permeability in response to the CNS infection whereas CD8 T cells and B cells are not. Like CNS autoimmunity, elevated BBB permeability in response to RV infection is evidently mediated by ONOO(-). However, as opposed to the invading cells producing ONOO(-) that have been implicated in the pathogenesis of CNS inflammation, during virus clearance ONOO(-) is produced without pathological sequelae by IFN-gamma-stimulated neurovascular endothelial cells.

Loss of blood-brain barrier integrity in the spinal cord is common to experimental allergic encephalomyelitis in knockout mouse models.

Experimental allergic encephalomyelitis (EAE) is an inflammatory demyelinating disease of the CNS that is used to model certain parameters of multiple sclerosis. To establish the relative contributions of T cell reactivity, the loss of blood-brain barrier (BBB) integrity, CNS inflammation, and lesion formation toward the pathogenesis of EAE, we assessed the incidence of EAE and these parameters in mice lacking NF-kappaB, TNF-alpha, IFN-alphabeta receptors, IFN-gamma receptors, and inducible nitric oxide synthase. Although increased myelin oligodendrocyte glycoprotein-specific T cell reactivity was generally associated with a more rapid onset or increased disease severity, the loss of BBB integrity and cell accumulation in spinal cord tissues was invariably associated with the development of neurological disease signs. Histological and real-time RT-PCR analyses revealed differences in the nature of immune/inflammatory cell accumulation in the spinal cord tissues of the different mouse strains. On the other hand, disease severity during the acute phase of EAE directly correlated with the extent of BBB permeability. Thus, the loss of BBB integrity seems to be a requisite event in the development of EAE and can occur in the absence of important inflammatory mediators.

Expression of a human anti-rabies virus monoclonal antibody in tobacco cell culture.

A Nicotiana tabacum cv. Xanthi cell culture was initiated from a transgenic plant expressing a human anti-rabies virus monoclonal antibody. Within 3 months, plant cell suspension cultures were established and recombinant protein expression was examined. The antibody was stably produced during culture growth. ELISA, protein G purification, Western blotting, and neutralization assay confirmed that the antibody was fully processed, with association of light and heavy-chains, and that it was able to bind and neutralize rabies virus. Quantification of antibody production in plant cell suspension culture revealed 30 microg/g of cell dry weight for the highest-producing culture (0.5 mg/L), 3 times higher than from the original transgenic plant. The same production level was observed 3 months after cell culture initiation. Plant cell suspension cultures were successfully grown in a new disposable plastic bioreactor, with a growth rate and production level similar to that of cultures in Erlenmeyer flasks.

Evidence that orexins A and B stimulate insulin secretion from rat pancreatic islets via both receptor subtypes.

Orexins are recently identified neuropeptides that appear to play a role in the regulation of energy homeostasis and arousal. They bind to and activate two closely related G protein-coupled receptors (OXR1 and OXR2), previously described as orphans. In this study we examined involvement of orexins in regulation of insulin secretion from rat pancreatic islets utilizing an in situ perfused pancreas and isolated pancreatic islet models. By means of RT-PCR we found that both OXR1 and OXR2 are expressed in rat pancreatic islets. Furthermore, the expression levels of OXR1 were higher than OXR2. In both experimental models applied, orexins A and B (1, 10 and 100 nmol/l) concentration dependently stimulated insulin secretion at two different glucose concentrations (6.66 or 26.4 mmol/l), with orexin A being more potent than orexin B. This study demonstrates that orexins A and B modulate insulin secretion in vitro.

ICAM-1 upregulation in the spinal cords of PLSJL mice with experimental allergic encephalomyelitis is dependent upon TNF-alpha production triggered by the loss of blood-brain barrier integrity.

Urate (UA) selectively scavenges peroxynitrite-dependent radicals and suppresses CNS inflammation through effects that are manifested at the blood-brain barrier (BBB). ICAM-1 upregulation in the spinal cord tissues of myelin basic protein (MBP) immunized mice is selectively inhibited by UA treatment. In contrast, the expression of ICAM-1 and other adhesion molecules by circulating cells is unchanged. Moreover, TNF-alpha expression in the CNS tissues of MBP-immunized mice is suppressed by UA treatment but TNF-alpha-induced ICAM-1 expression on neurovascular endothelial cells is not. Therefore the effect of UA on ICAM-1 upregulation in the CNS tissues is likely due to its known contribution to the maintenance of BBB integrity in MBP-immunized mice which in turn inhibits cell invasion into the CNS and prevents TNF-alpha production in CNS tissues.

The therapeutic effects of PJ34 [N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide.HCl], a selective inhibitor of poly(ADP-ribose) polymerase, in experimental allergic encephalomyelitis are associated with immunomodulation.

Poly(ADP-ribose) polymerase (PARP) activity has been implicated in the pathogenesis of several central nervous system (CNS) disorders. For example, the presence of extensive poly(ADP)ribosylation in CNS tissues from animals with experimental allergic encephalomyelitis (EAE) indicates that PARP activity may be involved in this inflammatory disease process. Using PJ34 [N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N, N-dimethylacetamide.HCl], a selective PARP inhibitor, we studied the mechanisms through which PARP activity may contribute to the onset of acute EAE. PLSJL mice immunized with myelin antigens were treated with PJ34, and the effects on the progression of EAE and several other parameters relevant to the disease process were assessed. PJ34 exerted therapeutic effects at the onset of EAE that were associated with reduced CNS inflammation and the maintenance of neurovascular integrity. Expression of genes encoding the intercellular adhesion molecule-1 (ICAM-1) and the inflammatory mediators interferon-gamma, tumor necrosis factor-alpha, and inducible nitric-oxide synthase were decreased in CNS tissues from drug-treated animals. Administration of PJ34 biased the class of myelin basic protein (MBP)-specific antibodies elicited from IgG2a to IgG1 and IgG2b and modulated antigen-specific T-cell reactivity. Therefore, the mode of action of PJ34 at the onset of EAE is likely mediated by a shift in the MBP-specific immune response from a proinflammatory Th1 toward an anti-inflammatory Th2 phenotype.

In vivo and in situ action of melatonin on insulin secretion and some metabolic implications in the rat.

INTRODUCTION: The role of melatonin in human insulin regulation is poorly understood. AIM: To investigate the influence of melatonin supplementation on glucose and insulin levels and on lipid metabolism in blood serum and the liver. METHODOLOGY: The acute melatonin effects on insulin secretion in male Wistar rats were investigated. In addition, carbohydrate and lipid metabolism was studied. In in vivo experiments, melatonin was administered subcutaneously in two different doses (0.5 and 1.0 mg/kg body weight, respectively), and animals were decapitated after 1 hour. RESULTS: The higher dose of the hormone increased insulin level in blood. The applied pancreas perfusion technique allowed us to confirm a direct mechanism of melatonin action on the pancreas. The ability of melatonin to stimulate insulin output was dose dependent. The highest effect was noticed for 100 nmol/L, whereas 1 nmol/L did not influence this process. CONCLUSION: Melatonin treatment in vivo caused many biochemical consequences. The hormone augmented significantly the concentrations of total, free, and esterified cholesterol, as well as high-density lipoprotein cholesterol in blood. Together with the enhanced insulin secretion observed in the in vivo experiment, the level of free fatty acids in blood decreased and, surprisingly, glucose concentration was significantly elevated.