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Posts Tagged ‘Alzheimer plaques’


Removing Alzheimer plaques

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Transdermal implant releases antibodies to trigger immune system to clear Alzheimer’s plaques            March 21, 2016

Test with mice over 39 weeks showed dramatic reduction of amyloid beta plaque load in the brain and reduced phosphorylation of the protein tau, two signs of Alzheimer’s
http://www.kurzweilai.net/transdermal-implant-releases-antibodies-to-trigger-immune-system-to-clear-alzheimers-plaques

 

An implant that can prevent Alzheimer’s disease. A new capsule can be implanted under the skin to release antibodies that “tag” amyloid beta, signalling the patient’s immune system to clear it before it forms Alzheimer’s plaques. (credit: École polytechnique fédérale de Lausanne

EPFL scientists have developed an implantable capsule containing genetically engineered cells that can recruit a patient’s immune system to combat Alzheimer’s disease.

Placed under the skin, the capsule releases antibody proteins that make their way to the brain and “tag” amyloid beta proteins, signalling the patient’s own immune system to attack and clear the amyloid beta proteins, which are toxic to neurons.

To be most effective, this treatment has to be given as early as possible, before the first signs of cognitive decline. Currently, this requires repeated vaccine injections, which can cause side effects. The new implant can deliver a steady, safe flow of antibodies.

Protection from immune-system rejection

Cell encapsulation device for long-term subcutaneous therapeutic antibody delivery. (B) Macroscopic view of the encapsulation device, composed of a transparent frame supporting polymer permeable membranes and reinforced with an outer polyester mesh. (C) Dense neovascularization develops around a device containing antibody-secreting C2C12 myoblasts, 8 months after implantation in the mouse subcutaneous tissue. (D and E) Representative photomicrographs showing encapsulated antibody-secreting C2C12 myoblasts surviving at high density within the flat sheet device 39 weeks after implantation. (E) Higher magnification: note that the cells produce a collagen-rich matrix stained in blue with Masson’s trichrome protocol. Asterisk: polypropylene porous membrane. Scale bars = 750 mm (B and C),100 mm (D), 50 mm (E). (credit: Aurelien Lathuiliere et al./BRAIN)

The lab of Patrick Aebischer at EPFL designed the “macroencapsulation device” (capsule) with two permeable membranes sealed together with a polypropylene frame, containing a hydrogel that facilitates cell growth. All the materials used are biocompatible and the device is reproducible for large-scale manufacturing.

The cells of choice are taken from muscle tissue, and the permeable membranes let them interact with the surrounding tissue to get all the nutrients and molecules they need. The cells have to be compatible with the patient to avoid triggering the immune system against them, like a transplant can. To do that, the capsule’s membranes shield the cells from being identified and attacked by the immune system. This protection also means that cells from a single donor can be used on multiple patients.

The researchers tested the device mice in a genetic line commonly used to simulate Alzheimer’s disease over a course of 39 weeks, showing dramatic reduction of amyloid beta plaque load in the brain. The treatment also reduced the phosphorylation of the protein tau, another sign of Alzheimer’s observed in these mice.

“The proof-of-concept work demonstrates clearly that encapsulated cell implants can be used successfully and safely to deliver antibodies to treat Alzheimer’s disease and other neurodegenerative disorders that feature defective proteins,” according to the researchers.

The work is published in the journal BRAIN. It involved a collaboration between EPFL’s Neurodegenerative Studies Laboratory (Brain Mind Institute), the Swiss Light Source (Paul Scherrer Institute), and F. Hoffmann-La Roche. It was funded by the Swiss Commission for Technology and Innovation and F. Hoffmann-La Roche Ltd.


Abstract of A subcutaneous cellular implant for passive immunization against amyloid-β reduces brain amyloid and tau pathologies

Passive immunization against misfolded toxic proteins is a promising approach to treat neurodegenerative disorders. For effective immunotherapy against Alzheimer’s disease, recent clinical data indicate that monoclonal antibodies directed against the amyloid-β peptide should be administered before the onset of symptoms associated with irreversible brain damage. It is therefore critical to develop technologies for continuous antibody delivery applicable to disease prevention. Here, we addressed this question using a bioactive cellular implant to deliver recombinant anti-amyloid-β antibodies in the subcutaneous tissue. An encapsulating device permeable to macromolecules supports the long-term survival of myogenic cells over more than 10 months in immunocompetent allogeneic recipients. The encapsulated cells are genetically engineered to secrete high levels of anti-amyloid-β antibodies. Peripheral implantation leads to continuous antibody delivery to reach plasma levels that exceed 50 µg/ml. In a proof-of-concept study, we show that the recombinant antibodies produced by this system penetrate the brain and bind amyloid plaques in two mouse models of the Alzheimer’s pathology. When encapsulated cells are implanted before the onset of amyloid plaque deposition in TauPS2APP mice, chronic exposure to anti-amyloid-β antibodies dramatically reduces amyloid-β40 and amyloid-β42 levels in the brain, decreases amyloid plaque burden, and most notably, prevents phospho-tau pathology in the hippocampus. These results support the use of encapsulated cell implants for passive immunotherapy against the misfolded proteins, which accumulate in Alzheimer’s disease and other neurodegenerative disorders.

 

A subcutaneous cellular implant for passive immunization against amyloid-β reduces brain amyloid and tau pathologies

 

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Passive immunization using monoclonal antibodies has recently emerged for the treatment of neurological diseases. In particular, monoclonal antibodies can be administered to target the misfolded proteins that progressively aggregate and propagate in the CNS and contribute to the histopathological signature of neurodegenerative diseases. Alzheimer’s disease is the most prevalent proteinopathy, characterized by the deposition of amyloid plaques and neurofibrillary tangles. According to the ‘amyloid cascade hypothesis’, which is supported by strong genetic evidence (Goate and Hardy, 2012), the primary pathogenic event in Alzheimer’s disease is the accumulation and aggregation of amyloid-β into insoluble extracellular plaques in addition to cerebral amyloid angiopathy (Hardy and Selkoe, 2002). High levels of amyloid-β may cause a cascade of deleterious events, including neurofibrillary tangle formation, neuronal dysfunction and death. Anti-amyloid-β antibodies have been developed to interfere with the amyloid-β cascade. Promising data obtained in preclinical studies have validated immunotherapy against Alzheimer’s disease, prompting a series of clinical trials (Bard et al., 2000;Bacskai et al., 2002; Oddo et al., 2004; Wilcock et al., 2004a; Bohrmann et al., 2012). Phase III trials using monoclonal antibodies directed against soluble amyloid-β (bapineuzumab and solanezumab) in patients with mild-to-moderate Alzheimer’s disease showed some effects on biomarkers that are indicative of target engagement. These trials, however, missed the primary endpoints, and it is therefore believed that anti-amyloid-β immunotherapy should be administered at the early presymptomatic stage (secondary prevention) to better potentiate therapeutic effects (Doody et al., 2014; Salloway et al., 2014). For the treatment of Alzheimer’s disease, it is likely that long-term treatment using a high dose of monoclonal antibody will be required. However, bolus administration of anti-amyloid-β antibodies may aggravate dose-dependent adverse effects such as amyloid-related imaging abnormalities (ARIA) (Sperling et al., 2012). In addition, the cost of recombinant antibody production and medical burden associated with repeated subcutaneous or intravenous bolus injections may represent significant constraints, especially in the case of preventive immunotherapy initiated years before the onset of clinical symptoms in patients predisposed to develop Alzheimer’s disease.

Therefore, alternative methods need to be developed for the continuous, long-term administration of antibodies. Here, we used an implant based on a high-capacity encapsulated cell technology (ECT) (Lathuiliere et al., 2014b). The ECT device contains myogenic cells genetically engineered for antibody production. Macromolecules can be exchanged between the implanted cells and the host tissue through a permeable polymer membrane. As the membrane shields the implanted cells from immune rejection in allogeneic conditions, it is possible to use a single donor cell source for multiple recipients. We demonstrate that anti-amyloid immunotherapy using an ECT device implanted in the subcutaneous tissue can achieve therapeutic effects inside the brain. Chronic exposure to anti-amyloid-β monoclonal antibodies produced in vivo using the ECT technology leads to a significant reduction of the amyloid brain pathology in two mouse models of Alzheimer’s disease.

 

Microglial phagocytosis study

The measurement of antibody-mediated amyloid-β phagocytosis was performed as proposed previously (Webster et al., 2001). In this study, we used either purified preparations of full mAb-11 IgG2a antibody, or a purified Fab antibody fragment. A suspension of 530 µM fluorescent fibrillar amyloid-β42 was prepared in 10 mM HEPES (pH 7.4) by stirring overnight at room temperature. The resulting suspension contained 30 µM fluorescein-conjugated amyloid-β42 and 500 µM unconjugated amyloid-β42 (Bachem). IgG-fibrillar amyloid-β42 immune complexes were obtained by preincubating fluorescent fibrillar amyloid-β42 at a concentration of 50 µM in phosphate-buffered saline (PBS) with various concentrations of purified mAb-11 IgG2a or Fab antibody fragment for 30 min at 37 °C. The immune complexes were washed twice by centrifugation for 5 min at 14 000g and resuspended in the initial volume to obtain a fluorescent fibrillar amyloid-β42 solution (total amyloid-β42 concentration: 530 µM). The day before the experiment, 8 × 104 C8-B4 cells were plated in 24-well plates. The medium was replaced with serum-free DMEM before the addition of the peptides. The cells were incubated for 30 min with fibrillar amyloid-β42 or IgG-fibrillar amyloid-β42 added to the culture medium. Next, the cells were washed twice with Hank’s Balanced Salt Solution (HBSS) and subsequently detached by trypsinization, which also eliminates surface-bound fibrillar amyloid-β42. The cells were fixed for 10 min in 4% paraformaldehyde and finally resuspended in PBS. The cell fluorescence was determined with a flow cytometer (Accuri C6; BD Biosciences), and the data were analysed using the FlowJo software (TreeStar Inc.). To determine the effect of the anti-amyloid-β antibodies on amyloid-β phagocytosis, the concentration of fluorescent fibrillar amyloid-β42 was set at 1.5 µM, which is in the linear region of the dose-response curve depicting fibrillar amyloid-β42 phagocytosis in C8-B4 cells (Fig. 2C). All experiments were performed in duplicate.

 

The implantation of genetically engineered cells within a retrievable subcutaneous device leads to the continuous production of monoclonal antibodies in vivo. This technology achieves steady therapeutic monoclonal antibody levels in the plasma, offering an effective alternative to bolus injections for passive immunization against chronic diseases. Peripheral delivery of anti-amyloid-β monoclonal antibody by ECT leads to a significant reduction of amyloid burden in two mouse models of Alzheimer’s disease. The effect of the ECT treatment is more pronounced when passive immunization is preventively administered in TauPS2APP mice, most notably decreasing the phospho-tau pathology.

With the recent development of biomarkers to monitor Alzheimer’s pathology, it is recognized that a steady increase in cerebral amyloid over the course of decades precedes the appearance of the first cognitive symptoms (reviewed in Sperling et al., 2011). The current consensus therefore suggests applying anti-amyloid-β immunotherapy during this long asymptomatic phase to avoid the downstream consequences of amyloid deposition and to leverage neuroprotective effects. Several preventive clinical trials have been recently initiated for Alzheimer’s disease. The Alzheimer’s Prevention Initiative (API) and the Dominantly Inherited Alzheimer Network (DIAN) will test antibody candidates in presymptomatic dominant mutation carriers, while the Anti-Amyloid treatment in the Asymptomatic Alzheimer’s disease (A4) trial enrols asymptomatic subjects after risk stratification. If individuals with a high risk of developing Alzheimer’s disease can be identified using current biomarker candidates, these patients are the most likely to benefit from chronic long-term anti-amyloid-β immunotherapy. However, such a treatment may pose a challenge to healthcare systems, as the production capacity of the antibody and its related cost would become a challenging issue (Skoldunger et al., 2012). Therefore, the development of alternative technologies to chronically administer anti-amyloid-β antibody is an important aspect for therapeutic interventions at preclinical disease stages.

Here, we show that the ECT technology for the peripheral delivery of anti-amyloid-β monoclonal antibodies can significantly reduce cerebral amyloid pathology in two mouse models of Alzheimer’s disease. The subcutaneous tissue is a site of implantation easily accessible and therefore well adapted to preventive treatment. It is, however, challenging to reach therapeutic efficacy, as only a small fraction of the produced anti-amyloid-β monoclonal antibodies are expected to cross the blood–brain barrier, although they can next persist in the brain for several months (Wang et al., 2011; Bohrmann et al., 2012). Our results are consistent with previous reports, which have shown that the systemic administration of anti-amyloid-β antibodies can decrease brain amyloid burden in preclinical Alzheimer’s disease models (Bard et al., 2000, 2003; DeMattos et al., 2001; Wilcock et al., 2004a, b; Buttini et al., 2005; Adolfsson et al., 2012).

Remarkably, striking differences exist among therapeutic anti-amyloid-β antibodies in their ability to clear already existing plaques. Soluble amyloid-β species can saturate the small fraction of pan-amyloid-β antibodies entering the CNS and inhibit further target engagement (Demattos et al., 2012). Therefore, antibodies recognizing soluble amyloid-β may fail to bind and clear insoluble amyloid deposits (Das et al., 2001; Racke et al., 2005; Levites et al., 2006; Bohrmann et al., 2012). Furthermore, antibody-amyloid-β complexes are drained towards blood vessels, promoting cerebral amyloid angiopathy (CAA) and subsequent microhaemorrhages. The mAb-11 antibody used in the present study is similar to gantenerumab, which is highly specific for amyloid plaques and reduces amyloid burden in patients with Alzheimer’s disease (Bohrmann et al., 2012; Demattos et al., 2012; Ostrowitzki et al., 2012). We find that the murine IgG2a mAb-11 antibody efficiently enhances the phagocytosis of amyloid-β fibrils by microglial cells. In addition, ECT administration of the mAb-11 F(ab’)2 fragment lacking the Fc region fails to recruit microglial cells, and leads only to a trend towards clearance of the amyloid plaques. Therefore, our results suggest a pivotal role for microglial cells in the clearance of amyloid plaques following mAb-11 delivery by ECT. Importantly, we do not find any evidence that this treatment may cause microhaemorrhages in the mouse models used in this study. It remains entirely possible that direct binding to amyloid plaques of a F(ab’)2 fragment lacking effector functionality can contribute to therapeutic efficacy, as suggested by previous studies using antibody fragments (Bacskai et al., 2002;Tamura et al., 2005; Wang et al., 2010; Cattepoel et al., 2011). However, compared to IgG2a, the lower plasma levels achieved with F(ab’)2 are likely to limit the efficacy of peripheral ECT-mediated immunization. The exact role of the effector domain and its interaction with immune cells expressing Fc receptors, could be determined by comparing the therapeutic effects of a control antibody carrying a mutated Fc portion, similar to a previous study which addressed this question using deglycosylated anti-amyloid-β antibodies (Wilcock et al., 2006a; Fuller et al., 2014).

Remarkably, continuous administration of mAb-11 initiated before plaque deposition had a dramatic effect on the amyloid pathology in TauPS2APP mice, underlining the efficacy of preventive anti-amyloid-β treatments. In this mouse model, where tau hyperphosphorylation is enhanced by amyloid-β (Grueninger et al., 2010), the treatment decreases the number of AT8- and phospho-S422-positive neurons in the hippocampus. Furthermore, the number of MC1-positive hippocampal neurons is significantly reduced, which also indicates an effect of anti-amyloid-β immunotherapy on the accumulation of misfolded tau. These results highlight the effect of amyloid-β clearance on other manifestations of the Alzheimer’s pathology. In line with these findings, previous studies have shown evidence for a decrease in tau hyperphosphorylation following immunization against amyloid-β, both in animal models and in patients with Alzheimer’s disease (Oddo et al., 2004; Wilcock et al., 2009;Boche et al., 2010; Serrano-Pozo et al., 2010; Salloway et al., 2014).

Similar to the subcutaneous injection of recombinant proteins (Schellekens, 2005), ECT implants can elicit significant immune responses against the secreted recombinant antibody. An anti-drug antibody response was detected in half of the mice treated with the mAb-11-releasing devices, in the absence of any anti-CD4 treatment. The glycosylation profile of the mAb-11 synthesized in C2C12 myoblasts is comparable to standard material produced by myeloma or HEK293 cells (Lathuiliere et al., 2014a). Although we cannot exclude that local release by ECT leads to antibody aggregation and denaturation, it is unlikely that this mode of administration further contributes to compound immunogenicity. Because the Fab regions of the chimeric recombinant mAb-11 IgG2a contain human CDRs, it remains to be determined whether the ECT-mediated delivery of antibodies fully matched with the host species would trigger an anti-drug antibody response.

Further developments will be needed to scale up this delivery system to humans. The possibility of using a single allogeneic cell source for all intended recipients is a crucial advantage of the ECT technology to standardize monoclonal antibody delivery. However, the development of renewable cell sources of human origin will be essential to ECT application in the clinic. Although the ARPE-19 cell line has been successfully adapted to ECT and used in clinical trials (Dunn et al., 1996; Zhang et al., 2011), the development of human myogenic cells (Negroni et al., 2009) is an attractive alternative that is worth exploring. Based on the PK analysis of recombinant mAb-11 antibody subcutaneously injected in mice (Supplementary material), we estimate that the flat sheet devices chronically release mAb-11 at a rate of 6.8 and 11.8 µg/h, to reach a plasma level of 50 µg/ml in the implanted animals. In humans, injected IgG1 has a longer half-life (21–25 days), with a volume of distribution of ∼100 ml/kg and an estimated clearance of 0.2 ml/h/kg. These values indicate that the predicted antibody exposure in humans, based on the rate of mAb-11 secretion achieved by ECT in mice, would be only 10 to 20-fold lower than the typical regimens based on monthly bolus injection of 1 mg/kg anti-amyloid-β monoclonal antibody. Hence, it is realistic to consider ECT for therapeutic monoclonal antibody delivery in humans, as the flat sheet device could be scaled up to contain higher amounts of cells. Furthermore, recent progress to engineer antibodies for increased penetration into the brain will enable lowering dosing of biotherapeutics to achieve therapeutic efficacy (Bien-Ly et al., 2014; Niewoehner et al., 2014). For some applications, intrathecal implantation could be preferred to chronically deliver monoclonal antibodies directly inside the CNS (Aebischer et al., 1996; Marroquin Belaunzaran et al., 2011).

Overall, ECT provides a novel approach for the local and systemic delivery of recombinant monoclonal antibodies in the CNS. It will expand the possible therapeutic options for immunotherapy against neurodegenerative disorders associated with the accumulation of misfolded proteins, including Alzheimer’s and Parkinson’s diseases, dementia with Lewy bodies, frontotemporal lobar dementia and amyotrophic lateral sclerosis (Gros-Louis et al., 2010; Bae et al., 2012; Rosenmann, 2013).

Abbreviations
ECT
encapsulated cell technology
mAb
monoclonal antibody
sjwilliamspa

The most powerful part of the article is the methodology of the transdermal patch of genetically engineered cells which appear to give a constant stream of antibody therapy. This would be better for the authors to have highlighted because the protein delivery system is great work. However it is a shame that the Alzheimer’s field is still relying on these mouse models which are appearing to lead the filed down a path which leads to failed clinical trials. Lilly has just dropped their Alzheimer’s program and unless the filed shifts to a different hypothesis of disease etilology I feel the whole field will be stuck where it is.

References

 

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