Linomide

IntroductionA chronic relapsing form ofexperimental autoimmune encephalomyelitis (CR-EAE) was induced in SJL/J mice by adoptive transfer of lymph node cells (LNC) sensitized to guinea pig myelin basic protein (GMBP). We examined the efficacy of high dose immunosuppressive regimens (cyclophosphamide ICY] 300 mg/kg or total body irradiation ITBI1 900 cGy) followed by syngeneic bone marrow transplantation (SBMT) in prevention and treatment of already established CR-EAE. Treatment with TBI and SBMT on day 5 after the induction of CR-EAE, just before the onset of clinical signs, completely inhibited the appearance of the paralytic signs. The same treatment, applied 4 d after the clinical onset of the disease, led to a significant regression of the paralytic signs and to a total inhibition of spontaneous relapses during a follow-up period of 2 mo. Challenge of mice with GMBP+CFA 78 d after the passive induction of CR-EAE induced a relapse of the disease 7 d later in almost all of the untreated mice; in contrast, the same challenge given to TBI+SBMT-treated mice caused a delayed relapse (30 d later) in only a minority (3/7) of the challenged mice. In vitro lymphocytic proliferative responses to GMBP and purified protein derivative were significantly lower in TBI+SBMT-treated mice before and after the GMBP challenge, although these mice were fully immunocompetent, as evidenced by their normal lymphocytic proliferation to concanavalin A (ConA) and the FACS® analysis of their lymphocytic subpopulations. A similar beneficial therapeutic effect was observed in mice treated with CY followed by SBMT, after the onset of CR-EAE.

No abstract

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.

Experimental autoimmune encephalomyelitis (EAE) is an inducible autoimmune disease widely used as a model of the acute/relapsing stage of multiple sclerosis. We have previously shown that treatment of EAE-mice with high doses of cyclophosphamide (CY) (350 mg kg), followed by syngeneic bone marrow transplantation (SBMT), completely abrogates the clinical paralytic signs and even prevents the appearance of new relapses in the chronic-relapsing model of the disease. In the present study we examined whether this treatment protocol induces long term tolerance and whether this tolerance is antigen-specific. EAE was induced by immunization with spinal cord homogenate (MSCH) in complete Freund's adjuvant (CFA). The treatment with CY and SBMT was performed on day 6 post immunization. Treated and untreated mice were rechallenged with MSCH, or a non-relevant antigen (OVA) in CFA at various stages after the first paralytic attack. In contrast to previous data showing that animals recovering from acute EAE are usually refractory to re-induction of the disease, repeated injections of MSCH at different sites from the initial immunization, followed by i.v. injection of inactivated Bordetella bacteria, 2, 4 and 6 months after the initial EAE-induction, caused a severe and usually lethal relapse in all the untreated, control animals. Mice treated with CY and SBMT were resistant to all rechallenges with the same encephalitogenic inoculum. Following the second rechallenge, peripheral lymph node cells were examined in vitro for their proliferative responses to myelin antigens or to OVA. Lymphocytes obtained from CY+SBMT treated mice did not proliferate in vitro in response to myelin basic protein (MBP), but proliferated against OVA, when immunized with this antigen, after SBMT. Adoptive transfer of lymphocytes from tolerant mice to naive recipients did not transfer resistance to EAE-induction. Our results indicate that high doses of CY, followed by SBMT, induce long term antigen-specific tolerance presumably by a mechanism of clonal deletion or anergy.