Time Course of Axon and Myelin Degeneration in Peripheral Nerves in Experimental Autoimmune Neuritis Rats.

Experimental autoimmune neuritis (EAN) is an animal model for Guillain-Barré syndrome (GBS), which results in neurological symptoms and histopathological changes in peripheral nerves. In this model, the correlation between the progression of the disease and the histopathological changes is not clear. To further examine histopathological changes in peripheral nerves in EAN rats, sciatic nerves were sampled at onset (day 10), peak (day 16), and recovery (days 22 and 25) of neurological symptoms in P2(57-81)-peptide-administered rats. Axon and myelin degeneration was observed by light microscopy at onset, degeneration became severe at peak, and persisted at recovery. Densities of myelinated nerve fibers and myelin areas decreased from day 10 to a minimum on day 22. Slight axon and myelin degeneration, such as accumulation of vesicles in axons and focal myelin splitting and folding, was observed by transmission electron microscopy at onset; severe degeneration, such as axonal loss, myelin ovoid, and demyelination, increased at peak; and regenerative changes, such as remyelination and enlargement of Schwann cell cytoplasm, occurred at recovery. These results suggest that EAN rats have histopathological similarities to some types of GBS patients and that EAN rats are a useful model to understand the pathogenesis of GBS.

Treatment for experimental autoimmune neuritis with clodronate (Bonefos).

Experimental autoimmune neuritis (EAN) serves as an animal model for human Gullain-Barre syndrome (GBS), an autoimmune disease causing demyelination and inflammation of peripheral nerves. Macrophages, which play a major role in this autoimmune inflammatory process, can be selectively targeted by high doses of bisphophonates. The goal of this study was to examine the effect of the bisphosphonate, clodronate, on the severity of the EAN model. EAN was induced in female adult rats by immunization with bovine peripheral myelin. A number of treatment protocols with clodronate were used based on the common dosage regimen of 20 mg/kg in humans starting with the appearance of clinical signs on day 10 post-immunization. The clinical parameters measured included a clinical score, a motor performance test performed on a Rotarod and body weight. The expression of the matrix metaloprotease (MMP-9) in the sciatic nerves was measured as a marker of inflammatory macrophages. Treatment with clodronate, 20 mg/kg daily and 40 mg/kg every 2 days, significantly reduced the disease severity (a 75% decrease in severity, p < 0.01 by ANOVA) as measured by the clinical score compared to controls. Performance on the Rotarod test and body weight confirmed the clinical score findings. MMP-9 expression levels were significantly lower in the sciatic nerves of clodronate-treated rats. The present findings support the efficiency of clodronate in inflammatory diseases of the peripheral nervous system. The mechanism of action includes inhibition of inflammatory macrophages. The results suggest the use of bisphosphonates be considered in humans with GBS.

Upregulation of erythropoietin in rat peripheral nervous system with experimental autoimmune neuritis.

The glycoprotein erythropoietin (EPO) is a multifunctional cytokine involved in erythropoiesis. Recent data have suggested that EPO and EPO receptors are expressed in the central nervous system, where EPO exerts neuroprotective effects. However, peripheral nervous system (PNS) EPO and EPO receptor expression has not been widely studied. EPO and EPO receptor expression was examined in the PNS in an experimental autoimmune neuritis (EAN) rat model in the present study to elucidate EPO/EPO-receptor binding pathway involvement in injured PNS tissue. Western blot analysis demonstrated that EPO was significantly increased in the PNS at the paralytic stage on day 14 post-immunization (PI); levels were significantly decreased at day 30 PI. EPO was identified in PNS-derived vascular endothelial cells, Schwann cells, and axons in normal control rats. Most inflammatory cells in EAN lesions were EPO immunopositive at day 14 PI. In addition, the intensity of EPO immunoreactivity in both Schwann and vascular endothelial cells was greater than that of normal controls at this stage; intensity declined at day 30 PI. These findings suggest that EPO is transiently upregulated in EAN lesions and that the EPO/EPO-receptor binding pathway is associated with neuroprotection in EAN-affected PNS tissues.

Chronic sensorimotor polyradiculopathy with antibodies to P2: an electrophysiological and immunoproteomic analysis.

In this study we report a patient with chronic progressive sensory ataxia, proximal weakness, immunoglobulin M (IgM) monoclonal gammopathy, and elevated protein levels in the cerebrospinal fluid, who showed a good response to prednisone. Electrophysiological study disclosed abnormalities predominantly of late responses (F waves and H reflexes), with no evidence of demyelination in the peripheral nerves, suggesting motor and preganglionic sensory nerve roots as the site of the lesion. An immune-mediated pathogenesis was considered and, to identify possible target antigens, we performed bidimensional electrophoresis and a Western blot study. Based on the suspected lesion site, we used human anterior and posterior root extracts. We identified IgM reactivity against peripheral nerve myelin protein P2. Enzyme-linked immunosorbent assay confirmed IgM reactivity toward one synthetic peptide from P2. To our knowledge, reactivity against P2 has not been reported previously in a paraproteinemic neuropathy. Furthermore, we demonstrated that bidimensional electrophoresis and Western blot of the tissue involved, as determined by clinical and electrophysiological studies, may be useful to establish clinical-immunological correlations in paraproteinemic neuropathies.

Immune responses to myelin proteins in Guillain-Barré syndrome.

BACKGROUND: Potential target autoantigens in the demyelinating form of Guillain-Barré syndrome (GBS) include the myelin proteins PMP22, P0 and P2. METHODS: We investigated immunoreactivity to P0, P2 and PMP22 proteins in 37 patients with GBS and 32 healthy controls. RESULTS: Antibodies to PMP22 or P0 peptides were detected at presentation in only 5 out of 37 patients. In ELISPOT assays, blood mononuclear cells from 15 out of 24 patients with GBS, but none of the control subjects, produced interleukin-10 (IL-10) in response to peptides from proteins P0, P2 or PMP22 (p = 0.0003). The cells from only two patients produced interferon-gamma (IFN gamma). The cells from 11 patients with GBS had increased IL-10 responses to peptides representing sequences from the extracellular domains of PMP22 before intravenous immunoglobulin (IVIg) treatment (p = 0.006). The cells from 11 patients with GBS, including 7 who responded to the extracellular domains of PMP22, had increased IL-10 responses to the intracellular domain of P0 before (p = 0.005) and those from 9 patients after they had been treated with IVIg (p = 0.01). CONCLUSIONS: Antibodies to P0 and PMP22 protein peptides do occur in GBS but are uncommon. Circulating mononuclear cell IFN gamma responses to P0, P2 and PMP22 myelin protein peptides are rare, but IL-10 responses occur significantly more often than in normal subjects. They might be part of a harmful pathogenetic process or represent a regulatory response.

Antibody responses to peptides of peripheral nerve myelin proteins P0 and P2 in patients with inflammatory demyelinating neuropathy.

BACKGROUND: Antibodies with reactivity to peripheral nerve myelin have previously been found in the serum, and bound to peripheral nerves of patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). AIM: To investigate the presence of antibodies reactive to specific peptide sequences within the myelin proteins P0 and P2 in patients with GBS, in patients with CIDP, in healthy controls and in patients with other neuropathies (ON). METHODS: Blood was obtained from 48 patients with GBS, 36 with CIDP, 48 with ON and 38 controls. ELISA was used to detect antibody responses to peptides of the human peripheral myelin proteins P0 and P2. Blood samples were collected from patients with GBS in early, peak and recovery stages of GBS to analyse antibody levels throughout the course of the disease. RESULTS: Significantly increased total IgG levels were found in patients with GBS compared with other groups. A higher percentage of patients with GBS at the peak of disease had antibody reactivity to P2(14-25) compared with patients with CIDP and control groups. In patients with GBS and CIDP, the percentages of patients with antibody reactivity to P2(61-70), and peptides derived from P0, were comparable to the control groups. Although some individual patients with GBS had high titres of reactivity to the peptide antigens tested, most patients with GBS and CIDP had levels of antibody similar to controls. CONCLUSION: Our data suggest that increased IgG levels and increased antibody reactivity to P2(14-25) in patients with GBS at the peak of disease may play a contributory role in the disease process in some patients with demyelinating forms of GBS.

Pain hypersensitivity in rats with experimental autoimmune neuritis, an animal model of human inflammatory demyelinating neuropathy.

Experimental autoimmune neuritis (EAN) is a T cell mediated autoimmune disease of the peripheral nervous system that serves as an animal model of the acute inflammatory demyelinating polyradiculoneuropathy in Guillain-Barre syndrome (GBS). Although pain is a common symptom of GBS occurring in 55-85% of cases, it is often overlooked and the underlying mechanisms are poorly understood. Here we examined whether animals with EAN exhibit signs of neuropathic pain including hyperalgesia and allodynia, and assessed their peripheral nerve autoimmune inflammation. We immunized Lewis rats with peripheral myelin P2 peptide (amino acids 57-81) emulsified with complete Freund's adjuvant, or with adjuvant only as control. P2-immunized rats developed mild to modest monophasic EAN with disease onset at day 8, peak at days 15-17, and full recovery by day 28 following immunization. Rats with EAN showed a significant decrease in withdrawal latency to thermal stimuli and withdrawal threshold to mechanical stimuli, in both hindpaws and forepaws, during the course of the disease. We observed a significant infiltration of T cells bearing alphabeta receptors, and a significant increase in antigen-presenting cells expressing MHC class II as well as macrophages, in EAN-affected rats. Our results demonstrate that animals with active EAN develop significant thermal hyperalgesia and mechanical allodynia, accompanied by pronounced autoimmune inflammation in peripheral nerves. These findings suggest that EAN is a useful model for the pain seen in many GBS patients, and may facilitate study of neuroimmune mechanisms underlying pain in autoimmune neuropathies.

T cell reactivity to P0, P2, PMP-22, and myelin basic protein in patients with Guillain-Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy.

OBJECTIVES: It has been suggested that autoimmunity to peripheral myelin proteins is involved in the pathogenesis of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We aimed to compare reactivity of peripheral blood mononuclear cells (PBMC) to antigens of peripheral myelin proteins in patients with GBS and patients with CIDP with that of healthy controls and patients with other non-immune mediated neuropathies (ON). METHODS: We prepared PBMC from blood from 83 healthy controls and from 64 patients with GBS, 54 with CIDP, and 62 with ON. PBMC were tested in antigen specific proliferation assays against peptides from myelin proteins P0, P2, PMP22, and myelin basic protein (MBP), which is identical to myelin P1, and against whole human MBP. Interferon-gamma (IFN-gamma) and interleukin (IL)-5 enzyme linked immunospot (ELISPOT) assays were also performed in some subjects to assess spontaneous and peripheral myelin antigen specific PBMC cytokine secretion. RESULTS: Antigen specific PBMC proliferation assays showed no significant elevation of peptide specific T cell responsiveness in patients with GBS or CIDP compared with healthy controls or patients with ON. Levels of spontaneous ELISPOT IFN-gamma secretion were increased in patients with GBS and significantly increased in those with CIDP compared with healthy controls and patients with ON. No convincing differences in antigen specific ELISPOT IFN-gamma secretion levels to individual peptides were detectable in patients with GBS. The proportion of patients with CIDP with an increased number of PBMC producing IFN-gamma in response to peptide PMP-22(51-64) was significantly increased compared with healthy controls and patients with ON. No significant differences in antigen specific ELISPOT IL-5 secretion levels were detectable in patients with GBS or CIDP compared with controls, but levels of spontaneous IL-5 secretion were significantly higher in patients with CIDP than in healthy controls or patients with ON. CONCLUSIONS: Although the lack of significantly increased antigen specific PBMC proliferation in GBS and CIDP does not support a role for T cells, the more sensitive ELISPOT technique detected increased numbers of PBMC secreting IFN-gamma spontaneously in 25% of patients with GBS, providing further evidence for a role of T cells in the immunopathology of GBS. Increased numbers of spontaneous IFN-gamma and IL-5 secreting cells, and increased IFN-gamma secretion in response to PMP-22(51-64), in patients with CIDP provide further evidence for a role of myelin specific T cells in CIDP.

MHC and non-MHC gene regulation of disease susceptibility and disease course in experimental inflammatory peripheral neuropathy.

With a panel of rat strains, we demonstrate a strong impact of the MHC genotype on susceptibility and disease course in experimental autoimmune neuritis induced with peripheral nerve myelin or the P2 peptide 58-81 (KNTEISFKLGQEFEETTADNRKTK). Beside the MHC genotype, non-MHC genes determined disease susceptibility and resistance. The type of disease induced with P2 58-81 was strongly correlated to the strength of the MHC class II isotype interaction with P2 58-81. These findings suggest a link between susceptibility and acute versus chronic disease courses on one hand and the strength of the MHC class II molecule/peptide affinity on the other hand.

Treatment and prevention of experimental autoimmune neuritis with superagonistic CD28-specific monoclonal antibodies.

Two distinct CD28-specific mAb were used in treatment of active or adoptive transfer (AT)-experimental autoimmune neuritis (EAN): "superagonistic" JJ316 activates T cells without T cell receptor (TCR) occupancy, and conventional JJ319 activates T cells only in the presence of TCR-stimulation. Treatment with JJ316 during induction phase of active and adoptive-transfer experimental autoimmune encephalomyelitis (AT-EAN) dramatically reduced disease severity and improved nerve function as revealed by electrophysiology. JJ316 given 1 week before immunization had a preventive effect. By immunohistology, JJ316 markedly reduced TC infiltration of the sciatic nerve in active and AT-EAN. JJ319 was less effective. Ex vivo, JJ316 therapy reduced P2-specific proliferation and interferon-gamma (IFN-gamma) production of lymph node cells. We demonstrate preventive and therapeutic effects of a "superagonistic" mAb-mediated, TCR-independent CD28 stimulation in EAN, possibly with implications for therapy of autoimmune-inflammatory disorders.

Increased expression of phospholipase D1 in the sciatic nerve of rats with experimental autoimmune neuritis.

Phospholipase D1 (PLD1) expression in the sciatic nerve was studied in induced experimental autoimmune neuritis (EAN) in Lewis rats. PLD1 immunoreactivity was seen in some Schwann cells in the sciatic nerves of normal rats. In parallel with the progression of EAN, PLD1-positive Schwann cells significantly increased in number and showed intense immunoreactivity. PLD1 was also detected in some ED1+ macrophages in EAN lesions. These results suggest that PLD1 in macrophages and Schwann cells plays an important role in the activation of these cells in the pathogenesis of EAN, an animal model of human peripheral demyelinating disease.

Adoptive transfer-experimental allergic neuritis in newborn Lewis rats results in inflammatory infiltrates, mast cell activation, and increased Ia expression with only minor nerve fiber degeneration.

Experimental allergic neuritis (EAN) induced in the Lewis rat by the adoptive transfer of a P2-specific T cell line (AT-EAN) is considered an animal model of Guillain-Barré syndrome. It is not yet known whether AT-EAN is inducible at early stages in the development of the peripheral nervous system (PNS) or whether disease activity is modified because of immaturity of either the nervous system or the immune system. We therefore compared the susceptibility of neo-natal and adult Lewis rats to AT-EAN induced by the adoptive transfer (intraperitoneally) of 10(6) activated P2-specific T cells. P2 antigen was already present in 7 day old Lewis rats and P2-specific T cell transfer into 3-day-old rats induced clinical disease associated with an inflammatory response (sciatic nerves and spinal ganglia). In injected newborn rats we observed local activation of mast cells, infiltration of the PNS by inflammatory cells, and induction of Ia antigen expression in Schwann cells. Unlike in adults, segmental or paranodal demyelination despite occasional nerve fiber degeneration did not occur. However, the difference between newborn and adult rats could not be ascertained statistically because of the relative rarity of the lesions, their focal character, the admixture of fiber demyelination and degeneration, and most importantly, size differences of the myelinated fibers, which result in a large developmental decrease in fiber density in adults compared to newborns.

Truncation of the neuritogenic peptide bP2(60-70) results in the generation of altered peptide ligands with the potential to interfere with T cell activation.

Due to the central role of T cells in the pathogenesis of inflammatory diseases of the peripheral nervous system like the Guillain-Barré syndrome, specific immunotherapies aim at modifying T cell responses. Use of truncated mutants of the neuritogenic peptide of myelin basic protein (MBP) has been shown to anergize autoreactive T cells and to reverse experimental autoimmune encephalitis (EAE). To establish a rationale basis for the use of altered peptide ligands (APLs) in the treatment of autoimmune diseases we designed a set of N- and C-terminally truncated mutants of the minimal experimental autoimmune neuritis (EAN) inducing bovine P2 (bP2) (60-70) peptide and compared them for the ability to induce immune responses and T cell receptor (TCR) cell signaling. Truncated peptides bound to MHC class II molecules and induced TCR internalization and expression of interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) with decreasing potency. None of the shortened mutants elicited a proliferative response in P2-specific T cells. Stimulation of these antigen-specific T cells with peptide bP2(62-69) using antigen presenting cells (APCs) prepulsed with bP2(60-70) resulted in a significant decrease of the proliferative response. In agreement with the observed effects on T cell activation, analysis of TCR signaling demonstrated a lack of CD3 epsilon phosphorylation and MAPK activation. Moreover, repeated injection of bP2(62-69) significantly slowed progression of adoptive transfer EAN (AT-EAN). Taken together, these findings strongly suggest that peptide bP2(62-69) can favorably modulate the antigen-induced response of neuritogenic T cells.

The processing and presentation of endogenous and exogenous antigen by Schwann cells in vitro.

The expression of major histocomatibility complex class II in vitro and in vivo by Schwann cells indicates a potential facultative role of Schwann cells in the presentation of antigen to neuritogenic T cells during inflammatory demyelinating neuropathies. Using a T cell proliferation assay, this study demonstrated that processing and presentation of endogenous and exogenous antigen by Schwann cells influences T cell proliferation. Statistical analysis of proliferation and its relation to processing and presentation of antigen by Schwann cells had not been previously addressed. Different combinations of factors including treatment of cultures (untreated, irradiated or fixed), concentration of exogenous antigen (0 or 40 microg/ml), the presence of interferon-gamma and the timing of exogenous antigen addition influence the proliferation P2-specific, non-mammalian protein ovalbumin-specific T cell lines and naive T cells.

Vaccination, prevention, and treatment of experimental autoimmune neuritis (EAN) by an oligomerized T cell epitope.

Using a polypeptide oligomer harboring 16 repeats of the neuritogenic epitope (aa 58-73) of myelin P2 protein separated by spacers, enhancement of the immune response to the P2 protein, an important neuritogenic autoantigen in experimental autoimmune neuritis (EAN), was attempted. In contrast to a previous study with PLP-16-mer antigen-specific response of T cells was attenuated at all doses examined to a variable degree. Treatment of Lewis rats with the P2-16-mer up to 2 months before immunization with P2(53-78) (vaccination) or after immunization but before appearance of disease (prevention) had a strong tolerizing effect against the induction of EAN on immunization with P2(53-78). Moreover, rats injected with 200 microg of the P2-16-mer i.v. on day 11 after disease induction, at which time the initial signs of disease had appeared, were almost completely protected against progression of clinical disease, whereas animals treated with the same amount of monomeric control peptide developed severe disease (treatment). Similar results were obtained by i.v. treatment of adoptive-transfer EAN with the P2-16-mer. The lack of clinical signs of disease after 16-mer therapy could be correlated with a reduced proliferative response of P2(53-78)-specific lymph node cells. The frequency of apoptotic T cells in sciatic nerve or in lymph node cells, however, was not increased by the 16-mer treatment, suggesting that induction of anergy or other forms of peripheral tolerance may be responsible for the effect. Thus, the oligomerized P2 peptide antigen was highly effective in all three treatment modalities examined in this specific autoreactive T cell-mediated immune response.

Schwann cell apoptosis in experimental autoimmune neuritis of the Lewis rat and the functional role of tumor necrosis factor-alpha.

Schwann cell (SC) apoptosis may be a critical factor challenging nerve remyelination and regeneration in experimental autoimmune neuritis (EAN) in the Lewis rat. We therefore analyzed the fate of SC during high-dose antigen therapy of adoptive transfer-(AT-) EAN using rhP2 protein. P2 antigen therapy was associated with an increase of tumor necrosis factor (serum levels 1 h after intravenous (i.v.) injection and an augmentation of T-cell apoptosis. Antigen specific therapy had no clear effect on SC apoptosis. The effects on SC apoptosis were determined by morphological criteria or by in situ tailing (IST) followed by immunocytochemical analysis. Secondly, we neutralized TNF-alpha, released in abundance by antigen treatment but only in small concentrations during natural disease course. We found that the addition of a TNF-alpha neutralizing antiserum resulted in a significant decrease in the rate of SC apoptosis in vivo compared to animals treated with control antigen rhP0 or with rhP2 only.

Transfer of myelin-specific cells deviated in vitro towards IL-4 production ameliorates ongoing experimental allergic neuritis.

A causal role of IL-4 (Th2) production for recovery in experimental allergic neuritis (EAN) was indicated by experiments where Th1-like autoreactive cell populations, taken from the induction phase of the disease, were deviated to extensive secretion of IL-4 in a selective fashion, by ex vivo stimulation with autoantigen in the presence of IL-4. The deviated cells were adoptively transferred to EAN rats at a time just prior to the onset of clinical signs. This treatment ameliorated EAN compared with sham treatment. This therapeutic approach, with generation of autoreactive IL-4-secreting cells ex vivo followed by subsequent adoptive transfer, may become a new selective treatment of organ-specific autoimmune diseases since, in contrast to previous attempts, it is done in a physiological and technically easy way.

Lipid-free versus lipid-bound P2 protein-induced experimental allergic neuritis: clinicopathological, neurophysiological, and immunological study.

The P2 protein of the peripheral nervous system myelin is a neuritogenic protein capable of inducing experimental allergic neuritis (EAN) in the Lewis rat. It has been suggested that the addition of some lipids to the protein isolated in the lipid-free form might enhance its immunogenicity. In this study, we compared lipid-free P2 (the EAN factor) and the corresponding lipid-bound form of the protein regarding their ability to induce EAN. Lipid-bound P2, copurified with all the myelin lipids, shows a conformation different from that of LF-P2. The timing of disease and the clinical scores of lipid-bound P2-induced EAN animals (n = 23) did not differ statistically from those injected with lipid-free P2 (n = 23), with only a tendency to higher clinical severity in the former group. Tail nerve conduction velocities did not differ in the two groups and in both were significantly lower in comparison to Freund adjuvant controls (n = 8). Inflammation and demyelination predominated in the spinal roots and were less evident in the sciatic nerve for both groups of animals. The ELISA determination of antibodies to lipid-free and lipid-bound P2 revealed the development of antibodies recognizing the lipid-free form of the protein in both groups of animals. Our results stand in contrast to results of previous studies performed after addition of exogenous lipids to the P2 purified in the lipid-free form and indicate that lipid-bound P2 is not significantly more immunogenic than lipid-depleted P2.