Search

Drug development, and especially that intended for central nervous system (CNS) disorders, still poses a challenge. We investigated both the use of bifunctional compounds designed for multiple targeting and enhanced CNS permeability, and of recombinant alpha-fetoprotein (AFP), a natural pregnancy-associated immunomodulating protein for the treatment of CNS inflammation. Bifunctional compounds showed a novel pharmacokinetic profile due to the conjugation, yet retained, and even improved pharmacodynamics. AFP was well tolerated and decreased various aspects of neuroinflammation, including disease severity, axonal loss and damage, T-cell reactivity, and antigen presentation. Our results show that both strategies may serve as future drug modalities., (Copyright (c) 2007 S. Karger AG, Basel.)

Paraneoplastic Neurologic Diseases (PND) are remote complications of certain neoplastic diseases characterized by distinct neurological deficits in the central as well as the peripheral nervous system. The neurological disorders are usually clinically evident before the cancer is identified. PND are rare syndromes believed to have an immunological link where antibodies or activated T cells are acting against self antigens shared by the tumor cells and neurons. Most of these onconeural antigens are located in the cytoplasm-nuclear compartment of the cell, whereas others are located at the membrane and act as receptors or ion channels. This short review discusses the autoimmune mechanisms involved in PND in general and in opsoclonus-myoclonus-ataxia in particular. The article attempts to clarify why in most PND the immune effector mechanisms against onconeural antigens detected in sera of patients may not be the direct cause of the neurological deficit. We elaborate on the difference between the immune response against cytoplasmic-nuclear antigens as opposed to membranal antigens with regard to the fact that: a) the nervous system is considered immune privileged; b) neither the tumors nor the neurons have an optimal expression of MHC class I antigens and onconeural epitopes on the membrane. The availability of onconeural antigens to the immune effectors mechanisms is probably the main reason why there are few animal models for PND.

MRL-lpr/lpr mice spontaneously develop a severe autoimmune syndrome, characterized by massive generalized lymphadenopathy, arthritis, arteritis, dermatitis and immune complex-mediated glomerulonephritis. Bone marrow transplantation (BMT) from MHC-matched systemic lupus erythematosus (SLE)-resistant donors to susceptible recipients has proved effective in correcting autoimmune manifestations in autoimmune-prone mice. We investigated the effect of syngeneic BMT from MRL/lpr (donor) to immunocompromised MRL/lpr (recipient), after purging the bone marrow inoculum with MoAbs against mature T cells (anti-Thy 1.2). All the untreated mice developed lymphadenopathy and by the age of 36 weeks five of the eight were dead; in contrast, all the mice which underwent syngeneic BMT following acute immunosuppression with total body irradiation (900 cGy) (TBI) remained disease-free. In an additional experiment, it was found that conditioning with cyclophosphamide (CY) before BMT was more effective than TBI in inhibiting delayed-onset autoimmune manifestations (mean survival 350 days in the CY group and 305 days in the TBI group, versus 197 days in untreated controls). Under both immunosuppressive regimens T cell-depleted bone marrow grafts produced far better results than did unmanipulated BMT. Following syngeneic BMT the incidence of proteinuria and the level of serum anti-DNA (dd) antibodies were significantly reduced, compared with that of the age-matched untreated controls. CY was more effective than TBI in reducing the anti-DNA titres. Likewise, T depletion of bone marrow inocula before BMT induced a more drastic drop in autoantibodies, following both CY and TBI conditioning protocols. After syngeneic BMT (either CY or TBI) no signs of lymphadenopathy were observed even at an advanced age. Upon histopathological examination, the BMT-treated mice displayed normal glomeruli with occasional minimal signs of glomerulonephritis. Syngeneic T cell-depleted BMT following acute cytoreduction of anti-self immune lymphocytes may represent a new therapeutic approach for drug-resistant autoimmune diseases.

Linomide (LS-2616, quinoline-3-carboxamide) is a synthetic immunomodulator that stimulates natural killer cell activity and activates several lymphocytic subpopulations in experimental animals and humans. In this study we determined the effect of oral treatment with linomide on the development of experimental autoimmune encephalomyelitis, an animal model for immune-mediated human demyelinating disorders. Experimental autoimmune encephalomyelitis was induced in SJL/J mice and in an outbred strain of rats (Sabra) by subcutaneous injection of spinal cord homogenate in adjuvant followed by inoculation with Bordetella pertussis. Linomide was administered in drinking water, at an estimated dose of 50 to 100 mg/kg/day. None of the linomide-treated mice (0/41) and Sabra rats (0/15) developed any clinical or pathological signs of experimental autoimmune encephalomyelitis, whereas almost all control animals (48/53 and 18/19, respectively) were severely paralyzed and 64.5% died from the disease. Lymphocytes obtained from linomide-treated animals had reduced in vitro proliferative responses to guinea pig myelin basic protein, proteolipid protein of the myelin, and tuberculin-purified protein derivative, unlike antigen-independent proliferation which was rather unaffected. Natural killer cell activity (tested by a cytotoxic assay on radiolabeled YAC-1 target cells) was significantly enhanced in mice treated with linomide. Our results indicate that modulation of the immune system with linomide leads to complete inhibition of experimental autoimmune encephalomyelitis in the absence of systemic immunosuppression. Linomide could therefore be of use in future clinical trials for the treatment of human autoimmune demyelinating disorders.

We report five patients who had multiple sclerosis (MS) associated with type I diabetes mellitus (TODM). Examination of the Israeli National Neurological Disease Register revealed the prevalence of TODM among 334 MS patients under the age of 30 years to be 8.98 per 1,000. This is significantly higher than the prevalence of TODM in the general population of Israel for the same age group, which is 0.095 per 1,000. MS and TODM share clinical, epidemiological and immunological features, and both diseases have a target site that is neuroectodermal in origin. The association between these two putative autoimmune diseases may suggest a similar pathogenetic mechanism.

Circulating autoantibodies against the acetylcholine receptor (AChR-Ab) are an important diagnostic tool in myasthenia gravis (MG). Lack of antibodies may cast doubt upon the diagnosis, the immune-mediated mechanism and the nature of the antigen. We examined clinical and laboratory features, response to immunotherapy and production of AChR-Ab in vitro, in 12 seronegative MG patients who were followed up for 2-30 years. It was possible to divide those patients into 2 groups: 7 patients with systemic muscle weakness, with a severe disease and with response to immunosuppressive therapies. The other group of 5 patients was characterized by oculobulbar symptomatology, a relatively benign course and immunotherapy was ineffective in 3 treated patients. Five patients underwent thymectomy and gland histology was normal in all of them. In none of 9 patients examined, were AChR-Ab synthesized in vitro (compared to 65% of seropositive myasthenic patients). Thus seronegative generalized MG is probably an autoimmune disease though the autoantigen is presently unknown and is responsive to immunosuppressive treatment. Seronegative oculobulbar MG might represent a separate disease entity in which immunological mechanisms play no significant role.

The influence of experimental autoimmune encephalomyelitis (EAE) on the course and outcome of pregnancy, and the effect of pregnancy on EAE development, was investigated in rabbits and rats. Animals were immunized with encephalitogenic antigen in complete Freund's adjuvant (CFA) either before or during pregnancy. Abortion or fetal resorption was observed in most of the rabbits immunized before or during pregnancy, but not in pregnant rabbits injected with CFA or saline alone. Fetal loss was higher in those rabbits that developed clinical EAE. In rats, fetal loss occurred only when immunization was carried out during the first half of pregnancy. The appearance of EAE in pregnant rabbits, but not in rats, was delayed until after abortion or termination of pregnancy. The incidence of EAE in rabbits was lower, with milder severity and longer duration. Serum antibody levels to myelin basic protein, the autoantigen of EAE, was lower in pregnant rabbits, but not in rats, as compared to non pregnant animals. These results indicate that in species where pregnancy has a suppressive influence on the development of experimental autoimmune demyelinating disease, immunization with the neuroantigen induces a high rate of fetal loss.

Of 66 patients (31 female and 35 male) with demyelinating inflammatory polyradiculoneuropathy (DIP), 12% (8/66) had a chronic relapsing and/or progressive course (CR-DIP) and 88% (58/66) had an acute monophasic illness (acute Guillain-Barré syndrome or GBS). Ten (15%) of the 66 had one or more associated putative autoimmune diseases; of these ten, five had CR-DIP and five had GBS. Cell-mediated immune responsiveness (CMI) of 30 cases with DIP was tested in vitro by lymphocyte transformation. Peripheral nervous system neuritogenic protein (NP) and central nervous system encephalitogenic myelin basic protein were the challenge antigens. Eighteen (60%) of the 30 patients had CMI to NP of human peripheral nervous system origin when a stimulation index (SI) of 2 or more was evaluated as positive; eight 27% (1) had CMI to NP when a positive SI was 3 or more. Of the 44 control patients with other neuropathies, only two (4.6%) demonstrated CMI to NP (SI, greater than or equal to 2). The in vitro response of patients with DIP to myelin basic protein (7/30) was not significantly different from that of the control population (16/44). The high incidence of DIP associated with autoimmune diseases and the CMI to NP in this group suggest that DIP may be an autoimmune disease with NP as one possible major antigen.

Experimental autoimmune myasthenia gravis (EAMG), induced in rabbits by injection of acetylcholine receptor (AChR) from Torpedo californica, was suppressed by appropriate treatment with hydrocortisone or with azathioprine. Administration of hydrocortisone in gradually increasing doses, starting at the time of immunization with the receptor, prevented exacerbation of the disease in the early stages of treatment, as was the case when hydrocortisone was administered in high doses from the beginning. Prolonged administration of the antimetabolite azathioprine (Imuran) prevented the appearance of EAMG, for at least 4 months, in rabbits immunized with AChR. Cell-mediated immunity to AChR was demonstrated to be significantly decreased in such treated animals. The effects of hydrocortisone and azathioprine on EAMG support the view that the disease involves an immunologically cell-mediated mechanism and indicate that the experimental disease can serve as a useful model for chemotherapy of the human disease.

Clinical and neuropharmacological evidence indicates the involvement of dopaminergic mechanisms in Parkinson's disease and schizophrenia, as well as in iatrogenic Parkinsonism and drug-induced schizophrenia-like syndrome. The evidence hitherto presented stresses the existence of a reversed relationship between Parkinson's disease and schizophrenia and implicates the possibility that dysfunction of dopamine-receptors may be a central phenomenon in both diseases. In view of the recent demonstration of two separate dopamine-receptors, it is postulated that a striatal receptor blockade may cause Parkinson's disease, whereas a limbic receptor blockade may result in schizophrenia. The recent discovery that several autoimmune diseases, such as myasthenia gravis, are the result of an immunopharmacological block at receptor sites, together with several observations of immunological disorders in Parkinson's disease and schizophrenia, suggests the possibility that certain types of Parkinson's disease and schizophrenia might be the consequence of an autoimmune blockade of striatal or limbic dopamine-receptors, respectively.

Patients with peripheral nervous system disorders were tested for the presence of cellular hypersensitivity to peripheral and central nervous system antigens by means of the in vitro lymphocyte transformation technique. Lymphocytes sensitized to the neuritogenic peripheral nervous system P1L basic protein were found in pure polyradiculitis of the Guillain-Barré syndrome type. Lymphocytes from patients with myeloradiculitis underwent transformation by peripheral P2 basic protein and by central nervous system basic encephalitogenic protein. In cases of chronic relapsing polyneuropathy response was shown to the central nervous system basic encephalitogen and to both of the peripheral nerve basic proteins. Lymphocytes from patients with other neurologic conditions showed no response to any oth these antigens. These findings suggest that cell mediated immunity to specific basic proteins of the myelin plays a rolw in the pathogenesis of the above-mentioned demyelinating disorders and may lead to a new approach in their classification and diagnosis.

Lymphocytes from patients with acute transverse myelopathy (ATM) were shown to undergo a specific and significant transformation when cultured in vitro in the presence of either the central nervous myelin basic encephalitogenic protein (BE) or the peripheral nerve myelin P2 protein. A similar pattern of response was demonstrated in acute disseminated encephalomyelitis and in acute myeloradiculitis. Lymphocytes from patients suffering from other autoimmune neurological disorders or other neurological diseases affecting the spinal cord showed no response to there immunologically related antigens, which have previously been found to have the capacity of inducing experimental allergic encephalomyelitis, either alone or with experimental allergic neuritis, when injected into animals. The specific in vitro response to BE and P2 suggests that in vivo sensitization of lymphocytes to such self-antigens occurs in ATM and than a cell-mediated, probably postinfecious autoimmune mechanism may be an important factor in the pathogenesis of the disease.