 |
Aβ and Tau Conformational Changes in AD
(1–5) (1) APP undergoes normal cleavage by β and γ-secretase (PS is part of the γ-secretase complex) to produce the (2) normal sAβ. sAβ can undergo a conformational change to (3) a β sheet-rich conformer that further aggregates to form (4) soluble, toxic Aβ oligomers. These also may precipitate to form (5) relatively inert fibrils in amyloid plaques and congophilic amyloid angiopathy.
(A–F) (A) Tau is a microtubule-binding protein. Tau can undergo (B) hyperphosphorylation or (C) a conformational change to a β sheet conformer. These species can both further change to (D) hyperphosphorylated tau in a β sheet-rich form that is predisposed to further aggregation into (E) toxic, tau oligomers. These can precipitate to form (F) PHFs in the form of NFTs.
(I and II) The Aβ β sheet conformers and Aβ oligomers may cross-seed, under some circumstances, with intermediate tau species in a β sheet conformation and with tau oligomers, to synergistically exacerbate AD pathology.
The most effective immunotherapeutic approaches for AD will need to be able to concurrently reduce levels of the toxic Aβ and tau oligomeric species.
Different Immunotherapeutic Approaches to Ameliorate AD Pathology
(A) Active immunization can be performed using Aβ peptides, phosphorylated tau (ptau) peptides, or preparations such as pBri as an immunogen. These immunogens are presented to B cells by antigen-presenting cells (APC). Use of Aβ peptides or ptau peptides will give rise to the production by B cells of antibodies to Aβ or ptau epitopes, respectively. Use of pBri (or equivalent preparations of an immunogen that is a non-self peptide, in a stabilized, oligomeric β sheet conformation) will lead to the production of antibodies that recognize both Aβ and tau pathological conformers (but not normal monomeric sAβ or tau proteins).
(B) Passive immunization can be performed by the production of mAbs that bind to Aβ, ptau, or β sheet pathological conformations. These antibodies need to be infused systemically in concentrations sufficient for adequate BBB penetration (typically only ∼0.1% of a systemically injected mAb will cross the BBB).
Once antibodies cross the BBB (using either active or passive immunization), they will act to enhance the clearance and degradation of their targets. Additional or alternative mechanisms may include disaggregation or neutralization of their target (i.e., blocking of toxicity). Antibodies to Aβ will recognize normal sAβ, oligomeric Aβ, and/or deposited fibrillar Aβ (with varying preference depending on the type[s] of antibodies to Aβ). Similarly, antibodies to ptau will recognize monomeric ptau species, oligomeric tau, and/or NFTs, with varying preference depending on the specific anti-ptau antibody(ies). Antibodies to β sheet will simultaneously act to ameliorate both Aβ and tau pathologies by specifically binding pathological conformers, without binding to normal sAβ or tau.
(C) Stimulation of innate immunity also can be used to ameliorate AD pathology by enhancing microglia/macrophage function via TLRs or related pathways. Microglia/macrophages are stimulated similarly by the immune complexes produced using active or passive immunization approaches.
|
AlzheimeResearch.com | Finding a cure for Alzheimer's disease
Immunotherapeutic Approaches for Alzheimer’s Disease
Opportunity to get involved in research to detect early Alzheimer's disease by participating in a registry
Biogen Idec is running a registry for researchers to advance their knowledge of early Alzheimers Disease. If you're having memory problems or are worried you're at risk of early Alzheimer’s, you can play an important role in improving our understanding of the disease. You will have the opportunity to learn about and take part in local studies looking at new treatment options. You will also receive some reimbursement for your time.
More about the registry:
- There will be 14000 participants in this registry
- This registry will take place over two years requiring no visits or overnight stays
- This registry is taking place nationwide and you can complete it from the comfort of you own home.
If you are interested, the full study details and eligibility criteria are listedhere.
Eligibility Criteria:
Participants must:
- be between 50 – 85 years old
- be willing to answer questionnaires periodically over a 2 year block of time
- be concerned that you are at risk for developing early Alzheimers have difficulty with memory or thinking skills
Participants must not:
- already be diagnosed with Alzheimers Disease
- have had events of stroke, epilepsy, or Parkinson's Disease Please complete the online questionnaire to check if you’re eligible for the trial.
ADDITIONAL INFO ON THE REGISTRY
If you agree to participate in the registry, you will be asked to complete an online questionnaire to assess how you understand, remember, and communicate information. This questionnaire will be repeated every 3 – 6 months. You will also be asked to take a brief 10 – 15 telephone call, which will be repeated every 6 months. The registry team may use your answers to see if you may qualify for another clinical research study. If you are interested in participating, we will ask for your permission to send your contact details to the study center. After you speak with someone at the study center, you can decide whether or not you want to participate in the study.
Learn why I’m talking about Clinical Trials
Subscribe to:
Posts (Atom)