Plasma monitoring in neurological diseases Flashcards
Why is early intervention important in neurological diseases?
Very important for neurological tissue as it cannot be repaired or restored.
Is there already ongoing pathology in the preclinical phase of a neurological disease?
A lot of neurological diseases have a long preclinical phase. A period sometimes as long as 10-20 years where there already is ongoing pathology, but the symptoms are not yet visible.
Why are biomarkers needed for drug development?
• To include the right patients in the preclinical phase
• To make sure there is target engagement
• To monitor side effects
• To measure outcomes in the preclinical phase
o Phase 2: biomarker endpoints are seen as reliable
o Phase 3: aiming for biomarkers to replace clinical outcomes
What are the pros and cons of looking at the CSF?
A very specific diagnosis can be made when we look into the CSF, but we really want blood-based biomarkers. This is because they allow you to monitor frequently as it is less invasive.
What is neurofilament light and how is it of use in neurological diseases?
It is a neuron specific protein that is released after axonal injury. With the new ultrasensitive technologies, it is also measurable in the small concentrations in blood instead of only the high concentrations in CSF. NFL is increased in many neurological diseases
o Only no good diagnostic value in MS
It is the pioneering biomarker for neurological diseases
What is Simoa?
Single Molecule Array technology (also “digital ELISA”). It is a sandwich immunoassay, but with beads
What are the advantages and disadvantages of Simoa?
Advantages:
o Automated platform
o Ultrasensitive: up to 1000-fold increase in assay sensitivity
o Wide portfolio of commercial assays, but also the possibility to develop your own assays (e.g. PD-1)
Disadvantages:
o Cost of the instrument itself, the maintenance and the reagents
o Novelty of the instrument: Struggle with “kinderziektes”
What is the principle of Simoa?
It is a sandwich ELISA but with beads. The primary antibody is stuck to a bead with its Fc tail and binds to the antigen. The secondary antibody also binds to the antigen and is coupled to a enzyme that can change the substrate (for detection).
Simoa gives a fluorescent signal when the antigen is captured. There is one bead per chamber, which makes it a digital signal (0 or 1)
What is the sensitivity of the Simoa NFL assay?
Sensitivity of Simoa NFL assay: CSF Neurofilament light correlates strongly with serum neurofilament light, but only when using a high-sensitive technique. There was correlation when using Simoa (R=0.88).
What is the use of NFL as a biomarker for diagnosis and prognosis?
NFL as a biomarker for diagnosis and prognosis:
•Diagnostics in familial Alzheimer’s disease and temperal dementia: NfL increases at the time of symptoms
•Prognostic value for clinical decline in MS: higher NfL means worse prognosis
•Relation with outcome in coma patients after cardiac arrest: High NfL means worse prognosis. –> really good prognostic marker (AUC=0.94)!
Can NFL be used as a monitoring biomarker to monitor treatment response?
In MS: when treatment works, NFL decreases. NFL can be used for monitoring side effects and NFL levels are also related to severity of the symptoms.
What are Alzheimer CSF biomarkers and what can they be used for?
They can now be used for diagnosis! An increase in Tau (tangle) and decrease in amyloid beta (plaque) can be used for diagnosis in combination with PET
What are the core Alzheimers disease pathologies reflected in blood biomarkers?
Plasma/serum pTau181 is increased in alzheimers disease compared to healthy controls, but also compared to other neurological diseases. –> Early marker
•Amyloid beta ratio can be used to predict progression in SCD (subjective cognitive decline) into MCI (multiple cognitive impairments) or dementia. Higher amyloid beta levels predict more risk of progression into MCI or dementia
o It is also usefull for prescreening for trial inclusion! Not 100%, but you can reduce the amount of people having to undergo a lumbar punction to confirm by 50%
oSimoa amyblood: Simoa assay developed for specific and multiplex detection of Amyloid 1-42/40 isoforms: relevant for target engagement
•Amyloid beta compared with PET (FDA approved): good, 0.75 fold increase
• Within this cohort: also compared NfL (1.5 fold increase) and GFAP (1.8 fold increase)
o GFAP: astrocytic marker
•All promising results –> It works to combine these 3 different AD biomarkers in 1 assay: the Amyblood 4-plex
Can baseline biomarkers predict Amyloid positivity 10 years later?
Yes! This was shown in a twin cohort
What can sensitive array based technologies be used for?
Sensitive array based technologies can be used for:
• Novel biomarkers in panels to capture the full complexity of dementias.
• Find protein signatures for differential dementia diagnosis with Olink. You can analyse >1500 proteins and it can be applied to blood, which you cannot do with mass spectrometry
o Olink can also be used for treatment monitoring in neurological diseases, cardiac disease and cancer
