Fulvio Baggi

Analysis of T cell receptor repertoire of muscle-infiltrating T lymphocytes in polymyositis. Restricted V alpha/beta rearrangements may indicate antigen-driven selection.

Polymyositis is an inflammatory myopathy characterized by mononuclear cell infiltration of muscle tissue. Myocytotoxic T lymphocytes have been recognized in the infiltrates, but the muscle antigen, target of the immune attack, has not been identified. Molecular characterization of the variable regions of T cell receptors (TCRs) on the infiltrating lymphocytes can be expected to provide insights into the pathogenic process. The V alpha/beta TCR repertoire was investigated by RNA-PCR in muscle biopsies from 15 polymyositis patients and 16 controls (6 Duchenne muscular dystrophy and 10 with no inflammatory or dystrophic myopathy). A variety of rearranged variable TCR genes was found in polymyositis, V alpha 1, V alpha 5, V beta 1, and V beta 15 being the most common (present in 60-100% of patients). In Duchenne muscular dystrophy patients TCR V alpha or beta rearrangements were found although no restriction was observed; no rearrangements were found in muscles from the other controls. Sequence analysis revealed the presence of the J beta 2.1 region in 90% of the V beta 15 clones studied, no random N additions in the diversity region, and a common motif within the CDR3 region. These results suggest that selection of muscle-infiltrating T lymphocytes is antigen driven in polymyositis.

Myasthenia Gravis (MG): Epidemiological Data and Prognostic Factors

Abstract: Data from 756 myasthenic patients were analyzed for diagnostic criteria, clinical aspects, and therapeutic approaches. The patients were followed up at our institution from 1981 to 2001. Clinical evaluation was performed according to the myasthenia gravis score adopted at our clinic. Clinical features of each patient (comprising demographic, clinical, neurophysiological, immunological, radiological, and surgical data, as well as serial myasthenia gravis scores) were filed in a relational database containing more than 7000 records. Clinical efficacy and variables influencing outcome were assessed by life‐table methods and Cox proportional hazards regression analysis. Complete stable remission, as defined by the Task Force of the Medical Scientific Advisory Board of the Myasthenia Gravis Foundation of America, was the end point for good prognosis. Four hundred and ninety‐nine patients (66%) were female and 257 (34%) were male. Mean follow‐up was 55.1 ± 48.1 months. Onset of symptoms peaked in the third decade in females, whereas the male distribution was bimodal with peaks in the third and sixth decades. Modality of myasthenia gravis presentation was as follows: ocular, 39.3%; generalized, 28.5%; bulbar, 31.3%; and respiratory, 0.8%. Thymectomy was carried out on 63.7% of our patients by different approaches: (1) transcervical; (2) transsternal; (3) video‐thoracoscopic mini‐invasive surgery. The last approach has been preferentially used in more recent years and accounted for 62.4% of the thymectomized myasthenia gravis population. Univariate analysis and Kaplan‐Meier analysis showed that variables such as sex (female), age at onset (below 40 years), thymectomy, and histological diagnosis of thymic hyperplasia were significantly associated with complete stable remission, whereas on multivariate analysis only age at onset below 40 years and thymectomy were confirmed.

Video-assisted thoracoscopic extended thymectomy and extended transsternal thymectomy (T-3b) in non-thymomatous myasthenia gravis patients: remission after 6 years of follow-up

The aims of this study were to assess the efficacy of video-assisted thoracoscopic extended thymectomy (VATET) as a treatment for myasthenia gravis (MG) and to identify prognostic factors for thymectomy success. Clinical efficacy and variables influencing outcome were assessed by life-table and Cox proportional hazards regression analysis. Complete stable remission (CSR), as defined by the MGFA Medical Task Force, was the end point for efficacy. VATET was performed in 159 MG patients and T-3b in 47 MG patients. At 6 years of follow-up, CSR, assessed by life-table analysis, was 50.6% in non-thymomatous VATET patients and 48.7% in non-thymomatous T-3b surgery. By univariate analysis, the presence of thymic hyperplasia (P=0.0002) and treatment only with anticholinesterases (P<0.0001) were positively associated with the probability of CSR. By multivariate analysis, the chance of complete remission was significantly increased by the use of anticholinesterases (odds ratio [OR] 2.45; 95% confidence interval [CI] 1.44-4.17; P=0.001) and the presence of thymic hyperplasia (OR 1.96; 95% CI 1.05-3.68; P=0.036). VATET seems to be effective in inducing CSR in MG with an efficiency similar to that of the T-3b transsternal (TS) approach; it is easy to perform in experienced hands and is associated with low morbidity and negligible esthetic sequelae.

Immunomodulation of TGF-beta1 in mdx mouse inhibits connective tissue proliferation in diaphragm but increases inflammatory response: Implications for antifibrotic therapy

Irreversible connective tissue proliferation in muscle is a pathological hallmark of Duchenne muscular dystrophy (DMD), a genetic degenerative muscle disease due to lack of the sarcolemmal protein dystrophin. Focal release of transforming growth factor-beta1 (TGF-beta1) is involved in fibrosis development. Murine muscular dystrophy (mdx) is genetically homologous to DMD and histopathological alterations comparable to those in DMD muscles occur in diaphragm of older mdx mice. To investigate the early development of fibrosis and TGF-beta1 involvement, we assessed diaphragms in 6-36-week-old mdx and C57/BL6 (control) mice for fibrosis, and used real-time PCR and ELISA to determine TGF-beta1 expression. Significantly greater fibrosis and TGF-beta1 expression were found in mdx from the 6th week. Mice treated with neutralizing antibody against TGF-beta1 had lower levels of TGF-beta1 protein, reduced fibrosis, unchanged muscles fiber degeneration/regeneration, but increased inflammatory cells (CD4+lymphocytes). These data demonstrate early and progressive fibrosis in mdx diaphragm accompanied by TGF-beta1 upregulation. Reduction of TGF-beta1 appears promising as a therapeutic approach to muscle fibrosis, but further studies are required to evaluate long term effects of TGF-beta1 immunomodulation on the immune system.

Delayed administration of erythropoietin and its non-erythropoietic derivatives ameliorates chronic murine autoimmune encephalomyelitis

Erythropoietin (EPO) mediates a wide range of neuroprotective activities, including amelioration of disease and neuroinflammation in rat models of EAE. However, optimum dosing parameters are currently unknown. In the present study, we used a chronic EAE model induced in mice by immunization with the myelin oligodendrocyte glycoprotein peptide (MOG35-55) to compare the effect of EPO given with different treatment schedules. EPO was administered intraperitoneally at 0.5, 5.0 or 50 microg/kg three times weekly starting from day 3 after immunization (preventive schedule), at the onset of clinical disease (therapeutic schedule) or 15 days after the onset of symptoms (late therapeutic schedule). The results show that EPO is effective even when given after the appearance of clinical signs of EAE, but with a reduced efficacy compared to the preventative schedule. To determine whether this effect requires the homodimeric EPO receptor (EPOR2)-mediated hematopoietic effect of EPO, we studied the effect of carbamylated EPO (CEPO) that does not bind EPOR2. CEPO, ameliorated EAE without changing the hemoglobin concentration. Another non-erythropoietic derivative, asialoEPO was also effective. Both EPO and CEPO equivalently decreased the EAE-associated production of TNF-alpha, IL-1beta and IL-1Ra in the spinal cord, and IFN-gamma by peripheral lymphocytes, indicating that their action involves targeting neuroinflammation. The lowest dosage tested appeared fully effective. The possibility to dissociate the anti-neuroinflammatory action of EPO from its hematopoietic action, which may cause undesired side effects in non-anemic patients, present new avenues to the therapy of multiple sclerosis.

Type I interferon and Toll-like receptor expression characterizes inflammatory myopathies

Objectives: Juvenile dermatomyositis (JDM), adult dermatomyositis, and polymyositis (PM) are idiopathic inflammatory myopathies (IIMs) characterized by muscle infiltration and specific muscle fiber alterations. They are thought to have an autoimmune etiology, but triggering factors, and how immunologic attack induces muscle weakness, remain unknown. Recent evidence suggests a key role for type I interferon (IFN)-mediated innate immunity in dermatomyositis, which we explored in JDM, dermatomyositis, and PM by gene expression profiling, and other methods. Methods: Ten IIM and 5 control muscle biopsies were assessed for expression of approximately 16,000 genes by microarray; 37 additional IIM, 10 dystrophinopathic, and 14 nonmyopathic control muscles were studied for type I IFN-dependent genes, and Toll-like receptor (TLR) expression by immunochemistry and PCR. Results: Type I IFN-dependent transcripts were significantly upregulated in IIM muscles compared to controls; in JDM the most expressed were ISG15 (408-fold), IFIT3 (261-fold), MX1 (99-fold), and IRF7 (37-fold). IFN-β (but not IFN-α) transcripts were upregulated in PM as well as dermatomyositis/JDM. TLR3 was upregulated particularly in JDM, being localized on vascular endothelial cells, muscle infiltrating cells (mainly myeloid dendritic cells), and regenerating myofibers; TLR7 and TLR9 proteins were present in IIM (prominently in PM), mainly on cell infiltrates, particularly plasma cells, and on some injured myofibers. Conclusions: IFN-β and type I IFN-induced molecules are involved in PM as well as JDM/dermatomyositis. Endosomal TLRs (effectors of innate immunity) are also involved (but differently) in the 3 conditions, further suggesting viral involvement, although TLR activation could be secondary to tissue damage.

A short plasma exchange protocol is effective in severe myasthenia gravis

SummaryPlasma exchange has been reported to be a successful therapeutic procedure for the treatment of severely compromised myasthenic patients, but the optimal regimen in terms of costs or clinical benefit has not so far been determined. We have investigated the efficacy of a short plasmapheresis protocol of two exchanges 1 day apart in a series of 70 patients with severe forms of myasthenia gravis. Patients were evaluated before and 7 days after the first exchange. A positive outcome was observed in 70% of the plasma exchange cycles performed. Disease severity did not seem to be a negative prognostic factor for the efficacy of this short protocol, which was well tolerated by patients. In only 1 case were major side-effects observed. In spite of its short duration, the exchange treatment plus concomitant immunosuppressive drug therapy was not followed by early clinical deterioration.

Increased Toll-Like Receptor 4 Expression in Thymus of Myasthenic Patients with Thymitis and Thymic Involution

Thymic abnormalities are present in approximately 80% of myasthenia gravis (MG) patients, and the thymus seems to be the main site of autosensitization to the acetylcholine receptor. In view of findings that the innate immune system can generate an autoimmune response, we studied the expression of Toll-like receptors (TLRs) 2 to 5, key components of innate immunity signaling pathways, in 37 thymuses from patients with autoimmune MG. TLR4 mRNA levels were significantly greater in thymitis (hyperplasia with diffuse B-cell infiltration) and involuted thymus than in germinal center hyperplasia and thymoma. By immunohistochemistry and confocal microscopy, cells positive for TLR4 protein were rarely detected in thymoma. However, in thymitis TLR4 protein was mostly found on epitheliomorphic (cytokeratin-positive) cells located in close association with clusters of acetylcholine receptor-positive myoid cells in thymic medulla and also at the borders between cortical and medullary areas. B cells were never TLR4-positive. TLR4 protein was also present in remnant tissue of involuted thymus. This is the first finding of a possible link between innate immunity and MG. We speculate that in a subgroup of MG patients, an exogenous or endogenous danger signal may activate the innate immune system and give rise to TLR4-mediated mechanisms contributing to autoimmunity.

Oral administration of an immunodominant T-cell epitope downregulates Th1/Th2 cytokines and prevents experimental myasthenia gravis

The mucosal administration of the native antigen or peptide fragments corresponding to immunodominant regions is effective in preventing or treating several T cell-dependent models of autoimmune disease. No data are yet available on oral tolerance with immunodominant T-cell peptides in experimental autoimmune myasthenia gravis (EAMG), an animal model of B cell-dependent disease. We report that oral administration of the T-cell epitope alpha146-162 of the Torpedo californica acetylcholine receptor (TAChR) alpha-subunit suppressed T-cell responses to AChR and ameliorated the disease in C57Bl/6 (B6) mice. Protection from EAMG was associated with reduced serum Abs to mouse AChR and reduced AChR loss in muscle. The effect of Talpha146-162 feeding was specific; treatment with a control peptide did not affect EAMG manifestations. The protective effect induced by peptide Talpha146-162 was mediated by reduced production of IFN-gamma, IL-2, and IL-10 by TAChR-reactive cells, suggesting T-cell anergy. TGF-beta-secreting Th3 cells did not seem to be involved in tolerance induction. We therefore demonstrate that feeding a single immunodominant epitope can prevent an Ab-mediated experimental model of autoimmune disease.

Detection of poliovirus-infected macrophages in thymus of patients with myasthenia gravis

Background: Genetic and environmental factors are thought to contribute to the etiology of the autoimmune disease myasthenia gravis (MG). Viral involvement has long been suspected, but direct evidence of involvement has not been found. We recently reported that Toll-like receptor 4 (TLR4)—a key activator of innate immunity—was overexpressed in the thymus of some patients with MG, suggesting that thymic infection by pathogens might be involved in MG pathogenesis. We searched for evidence of intrathymic infection in patients with MG. Methods: Twenty-seven MG thymuses (6 involuted, 7 hyperplastic, 5 thymitis, and 9 thymoma) previously tested for TLR4 expression, 18 nonpathologic control thymuses, and 10 pathologic control thymuses from patients without MG (8 thymoma and 2 hyperplastic) were analyzed for cytomegalovirus, varicella-zoster virus, herpes simplex virus types 1 and 2, eubacteria, respiratory syncytial virus, and enteroviruses using PCR techniques. Immunohistochemistry and double immunofluorescence were used to detect enterovirus capsid protein VP1 in thymic specimens and analyze TLR4 expression in VP1-positive cells. Results: Poliovirus was detected in 4 MG thymuses (14.8%; 2 thymitis and 2 thymoma). No virus was detected in any control thymus. A linear correlation between plus and minus strand poliovirus RNA levels was observed in all 4 thymuses, suggesting persistent thymic infection. VP1 protein was detected in the cytoplasm of CD68-positive macrophages scattered through thymic medulla in all PV-positive thymuses. VP1 and TLR4 colocalized in infected cells. Conclusions: Poliovirus-infected macrophages are present in thymus of some patients with myasthenia gravis, suggesting a viral contribution to the intrathymic alterations leading to the disease.