Mutations in the gene encoding superoxide dismutase 1 (SOD1) lead to misfolding and aggregation of SOD1 and cause familial amyotrophic lateral sclerosis (FALS). However, the implications of wild-type SOD1 misfolding in sporadic forms of ALS (SALS) remain unclear. By screening human memory B cells from a large cohort of healthy elderly subjects, we generated a recombinant human monoclonal antibody (α-miSOD1) that selectively bound to misfolded SOD1, but not to physiological SOD1 dimers. On postmortem spinal cord sections from 121 patients with ALS, α-miSOD1 antibody identified misfolded SOD1 in a majority of cases, regardless of their SOD1 genotype. In contrast, the α-miSOD1 antibody did not bind to its epitope in most of the 41 postmortem spinal cord sections from non-neurological control (NNC) patients. In transgenic mice overexpressing disease-causing human SOD1G37R or SOD1G93A mutations, treatment with the α-miSOD1 antibody delayed the onset of motor symptoms, extended survival by up to 2 months, and reduced aggregation of misfolded SOD1 and motor neuron degeneration. These effects were obtained whether α-miSOD1 antibody treatment was administered by direct brain infusion or peripheral administration. These results support the further development of α-miSOD1 antibody as a candidate treatment for ALS involving misfolding of SOD1.

Pathogenic amyloid-β peptide precursor (APP) mutations clustered around position 693 of APP—position 22 of the Aβ sequence—are commonly associated with congophilic amyloid angiopathy (CAA) and intracerebral hemorrhages. In contrast, the Osaka (E693Δ) intra-Aβ APP mutation shows a recessive pattern of inheritance that leads to AD-like dementia despite low brain amyloid on in vivo positron emission tomography imaging. Here, we investigated the effects of the Osaka APP mutation on Aβ accumulation and deposition in vivo using a newly generated APP transgenic mouse model (E22ΔAβ) expressing the Osaka mutation together with the Swedish (K670N/M671L) double mutation. E22ΔAβ mice exhibited reduced α-processing of APP and early accumulation of intraneuronal fibrillar Aβ oligomers associated with cognitive deficits. In line with our in vitro findings that recombinant E22Δ-mutated Aβ peptides form amyloid fibrils, aged E22ΔAβ mice showed extracellular CAA deposits in leptomeningeal cerebellar and cortical vessels. In vitro results from thioflavin T aggregation assays with recombinant Aβ peptides revealed a yet unknown antiamyloidogenic property of the E693Δ mutation in the heterozygous state and an inhibitory effect of E22Δ Aβ42 on E22Δ Aβ40 fibrillogenesis. Moreover, E22Δ Aβ42 showed a unique aggregation kinetics lacking exponential fibril growth and poor seeding effects on wild-type Aβ aggregation. These results provide a possible explanation for the recessive trait of inheritance of the Osaka APP mutation and the apparent lack of amyloid deposition in E693Δ mutation carriers.

IntroductionIn Alzheimer’s disease, accumulation and pathological aggregation of amyloid β-peptide is accompanied by the induction of complex immune responses, which have been attributed both beneficial and detrimental properties. Such responses implicate various cell types of the innate and adaptive arm of the immunesystem, both inside the central nervous system, and in the periphery. To investigate the role of the adaptive immune system in brain β-amyloidosis, PSAPP transgenic mice, an established mouse model of Alzheimer’s disease, were crossbred with the recombination activating gene-2 knockout (Rag2 ko) mice lacking functional B and T cells. In a second experimental paradigm, aged PSAPP mice were reconstituted with bone marrow cells from either Rag2 ko or wildtype control mice.ResultsAnalyses from both experimental approaches revealed reduced β-amyloid pathology and decreased brain amyloid β-peptide levels in PSAPP mice lacking functional adaptive immune cells. The decrease in brain β-amyloid pathology was associated with enhanced microgliosis and increased phagocytosis of amyloid β-peptide aggregates.ConclusionThe results of this study demonstrate an impact of the adaptive immunity on cerebral β-amyloid pathology in vivo and suggest an influence on microglia-mediated amyloid β-peptide clearance as a possible underlying mechanism.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-015-0251-x) contains supplementary material, which is available to authorized users.

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