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