Research could lead to new biomarkers that detect Alzheimer’s much earlier than existing tests and help scientists understand why some people with the disease do not develop dementia
Key biomarkers for detecting the progression of Alzheimer’s disease have typically been based on amyloid-beta (Aβ) plaques. But these plaques show up after the disease has well-progressed and aren’t suited to early detection of the disease.
Now, researchers at the University of Pittsburgh School of Medicine (Pitt) have developed a cerebrospinal fluid (CFS) test that detects changes in tau protein prior to the formation of neurofibrillary tangles (NFTs) that proceed Aβ plaques.
With further research, Pitt’s test could lead to new clinical laboratory biomarkers that help detect the disease earlier and with more accuracy.
“The clumping of tau protein into well-ordered structures, referred to by pathologists as neurofibrillary tangles, is a more defining event for Alzheimer’s disease as it is more strongly associated with the cognitive changes,” as compared to amyloid-beta pathology, according to a Pitt news release.
The researchers showed that their CSF biomarker test worked independent of discovery of brain amyloid deposits and “correlates with severity of cognitive decline” to enable “early-stage disease diagnosis and intervention,” reported Genetic Engineering and Biotechnology News.
“Our test identifies very early stages of tau tangle formation—up to a decade before any tau clumps can show up on a brain scan,” said Thomas Karikari, PhD (above), senior author and assistant professor of psychiatry at Pitt, in a news release. (Photo copyright: University of Pittsburgh.)
Combining Biomarkers May Lead to Better Alzheimer’s Knowledge
The new biomarkers may also work with existing markers that detect amyloid-beta pathology. This could give researchers and healthcare providers a better understanding of the early stages of Alzheimer’s in specific patients.
“Amyloid-beta is a kindling, and tau is a matchstick,” said Thomas Karikari, PhD, senior author and assistant professor of psychiatry at Pitt. Karikari previously researched amyloid-beta.
“A large percentage of people who have brain amyloid-beta deposits will never develop dementia. But once the tau tangles light up on a brain scan, it may be too late to put out the fire, and their cognitive health can quickly deteriorate. Early detection of tangle-prone tau could identify the individuals who are likely to develop Alzheimer’s-associated cognitive decline and could be helped with new generation therapies,” he added.
“P-tau-217 and p-tau-181 are fantastic biomarkers. However, in the early days after we developed these markers, we wondered why they were much more reflective of amyloid pathology than tau pathology,” Karikari told MedPage Today.
“That’s what inspired this work. We believe that methods combining, say, p-tau-217 and p-tau-262 or 356, would provide more complete information on combined early-stage amyloid and tau pathologies in Alzheimer’s disease,” he noted.
Developing the Alzheimer’s Biomarker Test
Karikari and colleagues turned to biochemistry and molecular biology to develop their new test.
Specifically, they emphasized “building blocks of NFTs including oligomers and protomers” which they called “soluble tau assemblies,” Medical News Today explained.
According to the Pitt news release, using autopsied brain tissue, the researchers found:
A core region of the tau protein where NFTs form.
111 amino acids in the region.
New “phosphorylation sites of p-tau-262 and p-tau-356 can inform the status of early-stage tau aggregation that, with an appropriate intervention, could potentially be reversed.”
In other words, p-tau-262 and p-tau-356 “could predict future NFT production, making them potential biomarkers for early disease,” Medical News Today noted.
“Together, our findings inform about the status of early-stage tau aggregation, reveal aggregation-relevant phosphorylation epitopes in tau, and offer a diagnostic biomarker and targeted therapeutic opportunities for Alzheimer’s disease,” the authors wrote in Nature Medicine.
More Research Planned Before Clinical Lab Use
About seven million Americans are affected by Alzheimer’s, according to the Alzheimer’s Association, which expects that number to grow to 13 million by 2050. A cure for the disease does not exist.
More research is needed before the Pitt researchers’ new CSF assay can be used by clinical laboratories. Karikari said the next step is developing blood assays for the biomarkers, MedPage Today reported.
New clinical laboratory test could replace conventional spinal tap for diagnosing neurodegenerative disease
In a proof-of-concept study, University of Pittsburgh (Pitt) scientists validated a clinical laboratory test that measures more than 100 different genetic sequences associated with Alzheimer’s disease. The Pitt researchers believe the new diagnostic platform could help clinicians “capture the multifaceted nature of Alzheimer’s pathology and streamline early disease diagnostics,” according to a news release.
Clinical laboratory blood tests that detect biomarkers such as phosphorylated tau protein (pTau) have emerged in studies as diagnostic possibilities for Alzheimer’s disease, which is traditionally diagnosed using a lumbar puncture (spinal tap) procedure.
In their paper, neuroscientist Thomas Karikari, PhD, Assistant Professor of Psychiatry at University of Pittsburgh, lead author of the study, and his research team acknowledged that progress has been made in detecting Alzheimer’s disease with blood-based biomarkers. However, they note that “two key obstacles remain: the lack of methods for multi-analyte assessments and the need for biomarkers for related pathophysiological processes like neuroinflammation, vascular, and synaptic dysfunction.”
The Pitt scientists believe the focus on so-called “classical Alzheimer’s blood biomarkers” limits exploration of neurodegenerative disease.
“Alzheimer’s disease should not be looked at through one single lens. Capturing aspects of Alzheimer’s pathology in a panel of clinically validated biomarkers would increase the likelihood of stopping the disease before any cognitive symptoms emerge,” said neuroscientist Thomas Karikari, PhD (above), Assistant Professor of Psychiatry, University of Pittsburgh, and lead author of the study in a news release. Should further studies prove Pitt’s research sound, clinical laboratories may have a replacement test for diagnosing neurodegenerative disease. (Photo copyright: University of Pittsburgh.)
On its website, Alamar Biosciences explains that the disease panel offers neurological researchers:
“Multiplexed analysis of 120 neuro-specific and inflammatory proteins from 10 µl of plasma or CSF (cerebrospinal fluid).
Detection of “critical biomarkers—including pTau-217, GFAP (glial fibrillary acidic protein), NEFL (neurofilament light polypeptide) and alpha-synuclein.”
The NULISAseq test works with “a proprietary sequential immunocomplex capture and release mechanism and the latest advances in next-generation sequencing,” according to the company.
Inside Precision Medicine noted that the Alamar Biosciences assay enabled Pitt scientists to detect:
Biomarkers (usually found in CSF) “correlating with patients’ amyloid positivity status and changes in amyloid burden over time,” and,
Biomarkers including “neuroinflammation, synaptic function, and vascular health, which had not previously been validated in blood samples.”
“The performance of the NULISA platform was independently validated against conventional assays for classic Alzheimer’s biomarkers for each sample. Biomarker profiles over two years were also compared with imaging-based measures of amyloid, tau, and neurodegeneration,” LabMedica reported.
Opportunity to Track Alzheimer’s
Karikari sees the diagnostic platform being used to track individuals’ blood biomarker changes over time.
In their Molecular Neurodegeneration paper, the Pitt researchers wrote, “These (results) were not limited to markers such as pTau217, p-Tau231, p-Tau181, and GFAP, the elevation of which have consistently shown strong associations with brain Aβ [amyloid beta] and/or tau load, but included novel protein targets that inform about the disease state of the individual in different pathological stages across the biological Alzheimer’s disease continuum.”
About seven million Americans are affected by Alzheimer’s disease, according to the Alzheimer’s Association, which estimated that figure will grow to 13 billion by 2050.
Further studies by Karikari may include larger samples and greater diversity among the people studied, Inside Precision Medicine noted.
“[Karikari’s] lab is developing a predictive model that correlates biomarker changes detected using NULISAseq with brain autopsy data and cognitive assessments collected over the course of several years. Their goal is to identify blood biomarkers that can help stage the disease and predict its progression, both for decision-making around clinical management and treatment plans,” the Pitt news release states.
The Pitt scientists have developed a multiplex test that works with 100 different genetic sequences associated with Alzheimer’s. Such advances in the understanding of the human genome are giving scientists the opportunity to combine newly identified gene sequences that have a role in specific disease states.
In turn, as further studies validate the value of these biomarkers for diagnosing disease and guiding treatment decisions, clinical laboratories will have new assays that deliver more value to referring physicians and their patients.
New scientific insights from these studies represent progress in the effort to develop a clinical laboratory test that would enable physicians to diagnose Alzheimer’s Disease earlier and with greater accuracy
Most medical laboratory professionals are aware that, for more than 30 years, in vitro diagnostic (IVD) developers and pharmaceutical researchers have sought the Holy Grail of clinical laboratory testing—an accurate test for Alzheimer’s disease that is minimally-invasive and produces information that is actionable by clinicians at a reasonable cost. Such a test could spark a revolution in the diagnosis and treatment of this debilitating disease and would improve the lives of tens of thousands of people each year.
Now, two different research studies being conducted in Germany and Japan may have developed such tests that use blood samples. The tests detect specific biomarkers found in Alzheimer’s patients and one day could enable physicians to diagnose the disease in its preclinical stages.
A healthy brain has amyloid-beta plaques, too. However, in a person with Alzheimer’s disease, the amyloid-beta is misfolded, formed like a sheet, and toxic to nerve cells, the researchers explained in a press release.
The test works with small amounts of blood plasma and employs an immuno-infrared-sensor, also developed at Ruhr University. The sensor measures the amounts of both pathological (the misfolded kind) and healthy amyloid-beta in the blood.
Amyloid plaques can start to form decades prior to the onset of Alzheimer’s symptoms, making them identifiable biomarkers that can be used as a “preselection funnel in two‐step diagnostics,” the researchers noted.
“The use of the immuno‐infrared‐sensor as an initial screening funnel to identify people who should undergo further diagnostics and eventually take part in clinical trials on therapeutics targeting Aβ misfolding might already be an important step forward because subjects with early AD stages are hard to identify,” the researchers note. “To our knowledge, there is today no other plasma test available, which has been tested both in an AD research cohort and in the general population.”
Klaus Gerwert, PhD, (left)Chair of Biophysics at Ruhr University in Bochum, Germany, and Dr. Katsuhiko Yanagisawa, PhD, (right) molecular biologist and Director of the Center for Development of Advanced Medicine for Dementia in Obu City, Japan, both lead research teams that developed tests for identifying amyloid-β biomarkers in early onset Alzheimer’s patients. More research must be conducted before these assays could be offered by clinical laboratories. (Photo copyrights: International Max Planck Research School in Chemical and Molecular Biology/Nagoya University School of Medicine.)
Another Blood Test Finds Amyloid-Beta
Interestingly, just a few months ahead of the German researchers’ paper, scientists at the Center for Development of Advanced Medicine for Dementia (CAMD) in Obu City, Japan, published their own paper on a similar blood test they developed that also identifies high levels of amyloid-beta in patients with Alzheimer’s.
The study, which was published in Nature, involved 373 people: 121 Japanese in the discovery cohort set and 252 Australians in the validation data set. The test found amyloid-beta levels in the brain with 90% accuracy, The Scientist reported.
“These results demonstrate the potential clinical utility of plasma biomarkers in predicting brain amyloid-β burden at an individual level. These plasma biomarkers also have cost-benefit and scalability advantages over current techniques, potentially enabling broader clinical access and efficient population screening,” the researchers wrote in their paper.
Nevertheless, as of 2018, Alzheimer’s disease has impacted the lives of approximately 5.7 million Americans of all ages, according to the Alzheimer’s Association. And yet, doctors currently only have expensive positron emission tomography (PET) brain scans and invasive cerebrospinal fluid (CSF) analysis to identify the disease, generally in the latter stages of its development.
Thus, a less invasive, inexpensive test that accurately identifies biomarkers found in the majority of people during the early stages of the disease would be a boon to physicians who treat chronic neurodegenerative disease, medical laboratories that perform the tests, and, of course, the thousands of people each year who are diagnosed and suffer with this debilitating condition.
