How special is a pathogenic CNS autoantigen? Immunization to many CNS self-antigens does not induce autoimmune disease

Type 1 narcolepsy: a CD8(+) T cell-mediated disease?

Type 1 narcolepsy is a sleep disorder characterized by excessive daytime sleepiness with unintentional sleep attacks and cataplexy. The disorder is caused by a loss of hypocretinergic neurons in the brain. The specific loss of these neurons in narcolepsy is thought to result from an autoimmune attack, and this is supported by evidence of both environmental and genetic factors pointing toward an involvement of the immune system. However, definitive proof of an autoimmune etiology is still missing. Several different immune-mediated disorders targeting neurons are known, and many of these are believed to be caused by autoreactive CD8(+) T cells. In this paper, we review the current knowledge on CD8(+) T cell-mediated neuronal damage on the basis of our understanding of other autoimmune disorders and experimental studies. We identify major histocompatibility complex class I presentation of autoantigens on neurons as a possible mechanism in the development of the disease, and propose T cell-mediated pathogenesis, with cytotoxic CD8(+) T cells targeting the hypocretinergic neurons, as a central element.

Application of glatiramer acetate to neurodegenerative diseases beyond multiple sclerosis: the need for disease-specific approaches

Adaptive and innate immunity, if well controlled, contribute to the maintenance of the CNS, as well as to downregulation of adverse acute and chronic neurological conditions. T cells that recognize CNS antigens are needed to activate resident immune cells and to recruit blood-borne monocytes, which act to restore homeostasis and facilitate repair. However, boosting such a T-cell response in a risk-free way requires a careful choice of the antigen, carrier, and regimen. A single vaccination with CNS-derived peptides or their weak agonists reduces neuronal loss in animal models of acute neurodegeneration. Repeated injections are needed to maintain a long-lasting effect in chronic neurodegenerative conditions, yet the frequency of the injections seems to have a critical effect on the outcome. An example is glatiramer acetate, a compound that is administered in a daily regimen to patients with multiple sclerosis. A single injection of glatiramer acetate, with or without an adjuvant, is neuroprotective in some animal models of acute CNS injuries. However, in an animal model of amyotrophic lateral sclerosis, a single injection of adjuvant-free glatiramer acetate is insufficient, while daily injections are not only ineffective but can carry an increased risk of mortality in female mice.Thus, considering immune-based therapies as a single therapy, rather than as a family of therapies that are regimen dependent, may be misleading. Moreover, the vaccination regimen and administration of a compound, even one shown to be safe in humans for the treatment of a particular neurodegenerative disease, must be studied in preclinical experiments before it is tested in a clinical trial for a novel indication; otherwise, an effective drug in a certain regimen for one disease may be ineffective or even carry risks when used for another disorder.