Therapeutic effects of immunization with mutant superoxide dismutase in mice models of amyotrophic lateral sclerosis

Abstract

There is emerging evidence for the existence of secretory pathways for superoxide dismutase (SOD1) mutants linked to amyotrophic lateral sclerosis (ALS) and for neurotoxicity of extracellular mutant SOD1. This evidence led us to test immunization protocols aiming to reduce the burden of extracellular SOD1 mutants in nervous tissue of mice models of ALS, by using bacterially purified recombinant SOD1 mutant protein as an immunogen. First, a vaccination was tested on a G37R SOD1 mouse strain with lateonset disease exhibiting levels of mutant SOD1 protein at 4-fold higher than normal SOD1 levels. Repeated injections of adjuvant/ SOD1 mutant with a final booster injection before symptoms at 6 months of age were effective in delaying disease onset and extending the life span of G37R SOD1 mice by >4 weeks. Western blot analysis with a monoclonal antibody specific to mutant SOD1 forms provided evidence of clearance of SOD1 species in the spinal cord of vaccinated G37R SOD1 mice. In contrast, this vaccination approach failed to confer significant protection in G93A SOD1 mice with extreme overexpression of mutant SOD1. Nonetheless, a passive immunization through intraventricular infusion of purified anti-human SOD1 antibody with osmotic minipump succeeded in alleviating disease symptoms and prolonging the life span of G93A SOD1 mice. From these results, we propose that immunization strategies should be considered as potential avenues for treatment of familial ALS caused by SOD1 mutations.vaccination ͉ immunotherapy ͉ antibody A myotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized with limb paralysis and atrophy. Since the discovery of genetic mutations in superoxide dismutase 1 (SOD1) in 20% of familial ALS patients (1) and the development of ALS model mice overexpressing SOD1 mutants (2), diverse pathogenic pathways to motor neuron death have been elucidated, such as protein misfolding and aggregation, proteasome impairment, inflammation, reactive oxygen species, excitotoxicity, and mitochondrial dysfunction (3, 4). Based on these hypotheses, multiple approaches for treatment have been tested in the ALS mice, including pharmacological approaches (5-10) and virus-mediated delivery of molecules (11-16). Recent lines of evidence indicate that the toxicity of SOD1 mutants is not strictly autonomous to motor neurons. Neuron-specific expression of mutant SOD1 failed to provoke motor neuron disease (17, 18), and chimeric mouse studies with SOD1 mutants demonstrated that neurodegeneration was delayed or eliminated when motor neurons expressing mutant SOD1 were surrounded by wild-type (WT) healthy cells (19). Moreover, the report by Clement et al. (19) showed evidence of damage to WT motor neurons that were surrounded by cells expressing mutant SOD1. These results emphasized the importance of motor neuron milieu, but they did not provide insight into the mechanism by which the toxicity of mutant SOD1 may be transferred from one cell to another.Although it is well known that SOD1 is a cytosolic ...

Prion-like propagation of mutant superoxide dismutase-1 misfolding in neuronal cells

“…Although primarily cytosolic, SOD1 can be secreted (15,16) and has been detected in cerebrospinal fluid of ALS patients (17). The recent success of SOD1 immunotherapy in transgenic mice clearly establishes the pathophysiological importance of extracellular SOD1 in ALS (18). These features are compatible with the hypothesis that SOD1-misfolding pathology might spread from the site of disease onset to neighboring cells.…”

Immunotherapeutic Approaches Targeting Amyloid-β, α-Synuclein, and Tau for the Treatment of Neurodegenerative Disorders

“…Finally, proteins other than Aβ, α-syn, and tau do accumulate in neurodegenerative disorders and are potential targets for immunotherapy as well. These include β-secretase [173], presenilin-1, leucine-rich repeat kinase 2 (LRRK2), superoxide dismutase-1 [174][175][176], TDP-43, and fused in sarcoma, among others. It is possible that simultaneously targeting these proteins would drastically improve the outcome of the immunotherapeutic approach.…”

Extracellular wildtype and mutant SOD1 induces ER–Golgi pathology characteristic of amyotrophic lateral sclerosis in neuronal cells

“…Similarly, extracellular misfolded SOD1 Wt induces cell death [16] and overexpression of SOD1 Wt induces misfolding of natively folded SOD1 in human but not mouse neuronal cell lines, demonstrating species specificity in the transfer of misfolding [17]. Furthermore, therapeutic strategies targeting extracellular SOD1 using antibodies specific to misfolded SOD1, delay disease progression in mutant SOD1 transgenic mice [18][19][20]. however, there is currently no evidence to show that uptake of extracellular misfolded SOD1 into neuronal cells initiates neurodegenerative pathways reminiscent of aLS pathology.…”