Deglycosylation of anti-beta amyloid antibodies inhibits microglia activation in BV-2 cellular model

Immune recruitment or suppression by glycan engineering of endogenous and therapeutic antibodies

Human serum IgG contains multiple glycoforms which exhibit a range of binding properties to effector molecules such as cellular Fc receptors. Emerging knowledge of how the Fc glycans contribute to the antibody structure and effector functions has opened new avenues for the exploitation of defined antibody glycoforms in the treatment of diseases. Here, we review the structure and activity of antibody glycoforms and highlight developments in antibody glycoengineering by both the manipulation of the cellular glycosylation machinery and by chemoenzymatic synthesis. We discuss wide ranging applications of antibody glycoengineering in the treatment of cancer, autoimmunity and inflammation. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

Naturally occurring autoantibodies against β-Amyloid

Naturally occurring antibodies (NAbs) have been described for more than 30 years. Recently, NAbs against β-Amyloid and against other proteins involved in neurodegenerative disorders have been detected in humans. Based on the current evidence, it is hypothesized that anti-Aβ NAbs can inhibit the fibrillation and toxicity of β-aymloid, can improve cognition in a transgenic mouse model and interfere with oligomers of Aβ. Different functions of these NAbs have been described in the current literature. Based on the results of the diverse studies a Phase-III study using IVIG has been initiated in patients with AD. The results will show whether the application of NAbs will change the fate of the disease. This chapter summarizes our current knowledge on NAbs against Aβ.

Microglia demonstrate age-dependent interaction with amyloid-β fibrils

Alzheimer's disease (AD) is an age-associated disease characterized by increased accumulation of extracellular amyloid-β (Aβ) plaques within the brain. Histological examination has also revealed profound microglial activation in diseased brains often in association with these fibrillar peptide aggregates. The paradoxical presence of increased, reactive microglia yet accumulating extracellular debris suggests that these cells may be phagocytically compromised during disease. Prior work has demonstrated that primary microglia from adult mice are unable to phagocytose fibrillar Aβ1-42 in vitro when compared to microglia cultured from early postnatal animals. These data suggest that microglia undergo an age-associated decrease in microglial ability to interact with Aβ fibrils. In order to better define a temporal profile of microglia-Aβ interaction, acutely isolated, rather than cultured, microglia from 2 month, 6 month, and postnatal day 0 C57BL/6 mice were compared. Postnatal day 0 microglia demonstrated a CD47 dependent ability to phagocytose Aβ fibrils that was lost by 6 months. This corresponded with the ability of postnatal day 0 but not adult microglia to decrease Aβ immunoreactive plaque load from AD sections in vitro. In spite of limited Aβ uptake ability, adult microglia had functional phagocytic uptake of bacterial bioparticles and demonstrated the ability to adhere to both Aβ plaques and in vitro fibrillized Aβ. These data demonstrate a temporal profile of specifically Aβ-microglia interaction with a critical developmental period at 6 months in which cells remain able to interact with Aβ fibrils but lose their ability to phagocytose it.

Intramuscular delivery of a single chain antibody gene prevents brain Aβ deposition and cognitive impairment in a mouse model of Alzheimer's disease

Anti-beta-amyloid (Aβ) immunotherapy is effective in removing brain Aβ, but has shown to be associated with detrimental effects. We have demonstrated that Adeno-associated virus (AAV)-mediated delivery of an anti-Aβ single chain antibody (scFv) gene was effective in clearing brain Aβ without eliciting any inflammatory side effects in old APP(Swe)/PS1dE9 transgenic mice. In the present study, we tested the efficacy and safety of intramuscular delivery of the scFv gene in preventing brain Aβ deposition. The scFv gene was intramuscularly delivered to APP(Swe)/PS1dE9 transgenic mice at 3 months of age, prior to Aβ deposition in the brain. Six months later, we found that the transgenes were expressed in a stable form at the delivered sites, with a small amount of ectopic expression in the liver and olfactory bulb. Brain Aβ plaque formation, Aβ accumulation, AD-type pathologies and cognitive impairment were significantly attenuated in scFv-treated APP(Swe)/PS1dE9 transgenic mice relative to EGFP-treated mice. Intramuscular delivery of scFv gene was well tolerated by the animals, did not cause inflammation or microhemorrhage at the gene expression site and in the brain, and did not induce neutralizing antibodies in the animals. These findings suggest that peripheral application of scFv is effective and safe in preventing the development of Alzheimer's disease (AD), and would be a promising non-inflammatory immunological modality for prevention and treatment of AD.

Novel strategies for Alzheimer's disease treatment

Considerable progress has been made in recent years towards better understanding the pathogenesis of Alzheimer's disease (AD), a dementing neurodegenerative disorder that affects > 10 million individuals in the US and Europe combined. Recent studies suggest that alterations in the processing of amyloid precursor protein (APP), resulting in the accumulation of amyloid-beta protein (Abeta) and the formation of oligomers leads to synaptic damage and neurodegeneration. Therefore, strategies for treatment development have been focused on reducing Abeta accumulation using, among other approaches, antiaggregation molecules, regulators of the APP proteolysis and processing, reducing APP production (e.g., small-interfering RNA), and increasing Abeta clearance with antibodies, apolipoprotein E and Abeta-degrading enzymes (e.g., neprilysin). The main focus of this review is on novel treatments for AD with a special emphasis on delivering neuroprotective and antiamyloidogenic molecules by gene therapy and by promoting neurogenesis.

Deglycosylated anti-amyloid beta antibodies reduce microglial phagocytosis and cytokine production while retaining the capacity to induce amyloid beta sequestration

Accumulation of amyloid beta (Abeta) is a pathological hallmark of Alzheimer's disease, and lowering Abeta is a promising therapeutic approach. Intact anti-Abeta antibodies reduce brain Abeta through two pathways: enhanced microglial phagocytosis and Abeta transfer from the brain to the periphery (Abeta sequestration). While activation of microglia, which is essential for microglial phagocytosis, is necessarily accompanied by undesired neuroinflammatory events, the capacity for sequestration does not seem to be linked to such effects. We and other groups have found that simple Abeta binding agents are sufficient to reduce brain Abeta through the sequestration pathway. In this study, we aimed to eliminate potentially deleterious immune activation from antibodies without affecting the ability to induce sequestration. The glycan portion of immunoglobulin is critically involved in interactions with immune effectors including the Fc receptor and complement c1q; deglycosylation eliminates these interactions, while antigen (Abeta)-binding affinity is maintained. In this study, we investigated whether deglycosylated anti-Abeta antibodies reduce microglial phagocytosis and neuroinflammation without altering the capacity to induce Abeta sequestration. Deglycosylated antibodies maintained Abeta binding affinity. Deglycosylated antibodies did not enhance Abeta phagocytosis or cytokine release in primary cultured microglia, whereas intact antibodies did so significantly. Intravenous injection of deglycosylated antibodies elevated plasma Abeta levels and induced Abeta sequestration to a similar or greater degree compared with intact antibodies in an Alzheimer's transgenic mouse model without or with Abeta plaque pathology. We conclude that deglycosylated antibodies effectively induced Abeta sequestration without provoking neuroinflammation; thus, these deglycosylated antibodies may be optimal for sequestration therapy for Alzheimer's disease.