High molecular weight Alzheimer's disease amyloid peptide immunoreactivity in human serum and CSF is an immunoglobulin G

Charting the Next Road Map for CSF Biomarkers in Alzheimer's Disease and Related Dementias

Clinical prediction of underlying pathologic substrates in people with Alzheimer's disease (AD) dementia or related dementia syndromes (ADRD) has limited accuracy. Etiologic biomarkers - including cerebrospinal fluid (CSF) levels of AD proteins and cerebral amyloid PET imaging - have greatly modernized disease-modifying clinical trials in AD, but their integration into medical practice has been slow. Beyond core CSF AD biomarkers (including beta-amyloid 1-42, total tau, and tau phosphorylated at threonine 181), novel biomarkers have been interrogated in single- and multi-centered studies with uneven rigor. Here, we review early expectations for ideal AD/ADRD biomarkers, assess these goals' future applicability, and propose study designs and performance thresholds for meeting these ideals with a focus on CSF biomarkers. We further propose three new characteristics: equity (oversampling of diverse populations in the design and testing of biomarkers), access (reasonable availability to 80% of people at risk for disease, along with pre- and post-biomarker processes), and reliability (thorough evaluation of pre-analytical and analytical factors influencing measurements and performance). Finally, we urge biomarker scientists to balance the desire and evidence for a biomarker to reflect its namesake function, indulge data- as well as theory-driven associations, re-visit the subset of rigorously measured CSF biomarkers in large datasets (such as Alzheimer's disease neuroimaging initiative), and resist the temptation to favor ease over fail-safe in the development phase. This shift from discovery to application, and from suspended disbelief to cogent ingenuity, should allow the AD/ADRD biomarker field to live up to its billing during the next phase of neurodegenerative disease research.

Accumulation of triosephosphate isomerase, with sequence homology to Beta amyloid peptides, in vessel walls of the newborn piglet hippocampus

We investigated whether beta-amyloid (Abeta)-like immunoreactivity was seen in the brains of newborn piglets. The immunoreactivity for Abeta(1-42) and Abeta(1-40) proteins, but not Abeta precursor protein, was present in CD68-positive perivascular cells of the hippocampus and in parts of the meninges. It was colocalized with immunoreactivity for receptor for advanced glycation end product and tumor necrosis factor-alpha. The protein with a molecular mass of 27 kDa, which was recognized by the Abeta antibodies, was identified as triosephosphate isomerase (TPI) with sequence homology to Abeta peptides by N-terminal amino acid sequencing, mass fingerprint analysis using matrix-associated laser desorption/ionization mass spectrometry, and Western blotting. Western blotting assay also revealed that detectable expression of Abeta proteins were not seen in the piglet brains. These findings indicate that TPI with sequence homology to Abeta peptides accumulates in perivascular cells of the microglia/macrophage lineage located around arterial vessels of the newborn piglet hippocampus.

Decrease of dehydrogenase activity of cerebral glyceraldehyde-3-phosphate dehydrogenase in different animal models of Alzheimer's disease

Recently, a relationship between glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the beta-amyloid precursor protein (betaAPP) in relationship with the pathogenesis of Alzheimer's disease (AD) has been suggested. Therefore, we studied the specific activity of GAPDH in the different animal models of AD: transgenic mice (Tg2576) and rats treated with beta-amyloid, or thiorphan, or lipopolysaccharides (LPS) and interferon gamma (INFgamma). We observed that GAPDH activity was significantly decreased in the brain samples from TG mice. The injection of beta-amyloid, or thiorphan, an inhibitor of neprilysin involved in beta-amyloid catabolism, in rat brains resulted in a pronounced reduction of the enzyme activity. The infusion of LPS and IFNgamma, which can influence the progression of the AD, significantly reduced the enzyme activity.

Cerebrospinal fluid tau and β-amyloid in Alzheimer patients, disease controls and an age-matched random sample

We prospectively evaluated the diagnostic accuracy of cerebrospinal fluid (CSF)-beta-amyloid1-42 (Abeta42), -total-tau (tau) and -phosphorylated-tau181 (p-tau181) as measured by sandwich ELISAs in the clinical routine of a community state hospital to discriminate between patients with Alzheimer's disease (AD), healthy controls (HC), non-AD-dementias, a group composed of various psychiatric disorders (non-AD-dementias, mental diseases) and an age-matched random sample (RS) (total N=219). By comparing patients with AD to HC as reference, tau revealed sensitivity (sens)/specificity (spec) of 88%/80%, p-tau(181) 88%/80%, tau/Abeta42-ratio 81%/85% and phospho-tau(181)/Abeta42-ratio 81%/78%. Discriminative power between HC and all dementias under investigation was estimated lower for tau (78%/77%) and p-tau(181) (73%/79%). Relative to patients with AD, ROC analysis for the RS revealed highest sens/spec for p-tau181 (79%/77%) and p-tau181/Abeta42 ratio (78%/75%). Differentiation between AD versus a group made of patients with various psychiatric disorders was optimised by using CSF-p-tau181 (80%/77%). Under clinical routine conditions current CSF-biomarkers show a substantial capacity to discriminate between AD and HC as reference and to mark off AD patients from RS and heterogeneous diagnostic groups composed of non-AD dementias and other psychiatric conditions. Despite a residual substantial overlap between the groups, we conclude that current CSF markers are well suited to support AD-related diagnostic procedures in every-day clinics.

Amyloid beta protein in plasma from patients with sporadic Alzheimer's disease

Fibrillar amyloid beta protein (A beta) deposition is increased in the brains of patients with Alzheimer's disease (AD), and is manifested as senile plaques (SPs) and congophilic angiopathy (CA). A beta 40 and A beta 42(43), two chief species of A beta, are documented in SPs and CA, as well as in cerebrospinal fluid (CSF) and cell culture media. A beta 42(43) is the major component of diffuse plaques, the earliest form of SPs. Thus, we hypothesized that determination of the amount of A beta 42(43) in CSF or plasma might provide a diagnostic laboratory test for AD. We measured amounts of different A beta species in plasma from 28 patients with sporadic probable AD, 40 age-matched neurologic patients without dementia and 25 age-matched normal controls using enzyme-linked immunosorbent assays (ELISAs). Plasma concentrations of A beta 1-40 and A beta 1-42(43) did not significantly differ among these groups. These findings suggest the unlikelihood that plasma A beta assays would be useful as a diagnostic tool for AD.

Antibodies to amyloid beta protein (A beta) crossreact with glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

In the present study, we characterized the epitope of a monoclonal antibody against purified amyloid plaque cores (Am-3). By immunocytochemical experiments, Am-3 stained cerebrovascular and senile plaque amyloid in brain sections of patients with Alzheimer's disease (AD) in a similar manner to that of antibodies against amyloid beta-protein (A beta). By Western blotting experiments, Am-3 recognized only a 35 kDa protein, which was revealed to be glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and not A beta or beta amyloid precursor protein (beta PP). However, Am-3 recognized both GAPDH and purified native A beta in a dot-binding assay. Therefore, we concluded that Am-3 recognized both GAPDH and native A beta. Other monoclonal antibodies (6C6 and AmT-1) against the synthetic peptide corresponding to residues 1-28 of A beta also recognized these proteins. Because the amino acid sequences of these two proteins are not homologous, we propose that the crossreactivity between A beta and GAPDH is a consequence of their similar conformational epitopes. The possibility of crossreactions would complicate immunochemical and immunocytochemical studies of brain aging, AD and Down's syndrome. The implications of crossreactivity in developing immunological assays and in investigating the amyloid deposits of AD are discussed.

Binding of IgG to amyloid beta A4 peptide via the heavy-chain hinge region with preservation of antigen binding

Amyloid beta A4 peptide is found in the extracellular region of the senile plaque and in the angiopathy of Alzheimer's disease. Several other proteins, including IgG, also reside in these abnormal structures. In an attempt to understand how these structures are assembled and to determine how proteins are recruited, interactions of various proteins with synthetic beta A4 peptide have been examined in vitro. Purified IgG binds directly to synthetic beta A4 peptide with high avidity. The domain between amino acids 12-28 of beta A4 binds IgG. beta A4 peptide binds the hinge region of the immunoglobulin heavy chain, and preserves the ability of the immunoglobulin to bind antigen. A protein which does not bind directly to beta A4 peptide can be targetted to the senile plaque and angiopathy by binding to IgG, which avidly binds beta A4 peptide.

Characterization of beta-amyloid peptide from human cerebrospinal fluid

beta-Amyloid peptide (A beta) is one of the main components of senile plaques in the brain tissue of Alzheimer's disease (AD) patients. A beta is proteolytically cleaved from the amyloid precursor protein (APP), an integral membrane protein possessing a large extracellular N-terminal domain followed by a single membrane-spanning region and a short cytoplasmic C-terminal tail. A beta has been isolated from senile plaques and cerebral vascular tissue of AD brain and characterized as a heterogeneous peptide containing 28-43 amino acids whose sequence begins in the extracellular domain of APP and extends into the putative transmembrane sequence. It has long been speculated that A beta may also be present in body fluids, such as CSF, that contact neuritic plaques. Recently using a specific enzyme-linked immunosorbent assay we were able to quantify one form of A beta in CSF. In this report, using one of these antibodies covalently bound as an affinity matrix, multiple complex forms of A beta have been isolated and characterized from CSF derived from patients with either meningitis or other neurological disorders. Amino acid sequencing reveals A beta species with N-termini of Asp1, Glu3, His6, Glu11, and Val12, although on a molar basis, Asp1 represents the predominant aminoterminus. Laser desorption mass spectrometry confirmed the presence in CSF of A beta species containing 27, 28, 30, 34, 35, 40, 42, and 43 amino acids, all beginning at Asp1; two stable trimers, (Asp1-Met35)3 and (His6-Ala42)3; and one stable dimer containing (Asp1-Val40)2.(ABSTRACT TRUNCATED AT 250 WORDS)

A case of progressive supranuclear palsy with widespread senile plaques

A case of progressive supranuclear palsy (PSP) with frontal lobe atrophy is reported, in which many senile plaques were widely distributed in the neocortex, the entorhinal cortex, the amygdala, and, to a lesser extent, the cerebellar cortex, but not in the hippocampus. Most of the plaques were of the diffuse and primitive types. They were well visualized by beta-protein immunostaining, modified Bielschowsky staining and methenamine silver staining, but were not seen by Bodian staining. The widespread distribution of senile plaques in the cerebral and cerebellar cortices was far beyond that seen in normal aging, and was reminiscent of concomitant Alzheimer's disease (AD). Unlike AD, however, this case had neither senile changes in the hippocampus nor neurofibrillary tangles in the amygdala and entorhinal cortex. It seems that many senile plaques may appear widely in the cerebral cortex and even, to a lesser extent, in the cerebellar cortex of some patients with PSP. Additional case studies using sensitive silver and amyloid antibody preparations are required to elucidate the presence of senile plaques in the cerebral cortex of PSP.

Integrity of the blood-CSF barrier in dementia of Alzheimer type: CSF/serum ratios of albumin and IgG

Serum and cerebrospinal fluid (CSF) from 25 patients with dementia of Alzheimer type (DAT) and 25 controls were assayed for concentrations of albumin and IgG. The severity of dementia was rated with the Mini Mental State Examination. The CSF/serum ratio for albumin and IgG as well as the IgG index were used to evaluate blood-CSF barrier function in the respective groups. The control group was matched for age, sex and the indirect alcohol parameters, mean corpuscular volume and gamma-glutamyltranspeptidase. There were no signs of dysfunction of the blood-CSF barrier for proteins or signs of local synthesis of IgG in the central nervous system (CNS) of the demented patients. The permeability of the blood-CSF barrier appeared to be unrelated to dementia severity. The data do not support the hypothesis that a pathological leakage through the blood-CSF barrier facilitates the entry of extraneuronal proteins to the CNS, which might contribute to the pathophysiological process in DAT.

Amyloid in central nervous system disease

A review is presented of diseases of the central nervous system associated with amyloid deposition. The name amyloid is given to substances with particular physical characteristics which are independent of the chemical constitution of the proteins in the substance. Ideally, a classification of amyloid diseases should be based on the chemical composition of the amyloid deposits; this has only been partially realized. The best documented group of diseases with amyloid deposition in the central nervous system is the group of 'cerebral beta amyloid diseases', characterized by the deposition of beta-protein. This group includes: Alzheimer's disease, sporadic cerebral amyloid angiopathy, Down's syndrome, Parkinson-dementia of Guam, hereditary cerebral hemorrhage with amyloidosis-Dutch type and age-related asymptomatic amyloid angiopathy.

Amyloid A4 protein and its precursor in Down's syndrome and Alzheimer's disease

In patients with Alzheimer's disease, amyloid fibrils that are aggregates of A4 protein subunits are deposited in the brain. A similar process occurs at an earlier age in persons with Down's syndrome. To investigate the deposition of amyloid in these diseases, we used a radioimmunoassay to measure levels of the amyloid precursor (PreA4) in the serum of 17 patients with Down's syndrome, 15 patients with Alzheimer's disease, and 33 normal elderly controls. The mean (+/- SD) concentration of serum PreA4 was increased 1.5-fold in patients with Down's syndrome (2.49 +/- 1.13 nmol per liter) as compared with that in controls (1.68 +/- 0.49 nmol per liter; P less than 0.007); the levels in patients with Alzheimer's disease were similar to those in controls (1.83 +/- 0.78; P less than 0.98). We also found that the concentration of PreA4 in the brain tissue of two adults with Down's syndrome (100 and 190 pmol per gram) was higher than that in the brain tissue of either 26 patients with Alzheimer's disease (64.4 +/- 17.3 pmol per gram) or 17 elderly controls with neurologic disease (68.5 +/- 26.3 pmol per gram). Immunocytochemical studies of brain tissue from 26 patients with Down's syndrome showed that the deposition of A4 protein amyloid began in these patients approximately 50 years earlier than it began in 127 normal aging subjects studied previously, although the rate of deposition was the same. We conclude that, since the gene for PreA4 is on the long arm of chromosome 21, which is present in triplicate in Down's syndrome, overexpression of this gene may lead to increased levels of PreA4 and amyloid deposition in Down's syndrome. However, since increased levels of PreA4 are not present in Alzheimer's disease, additional factors must account for the amyloid deposition in that disorder.

An immunohistochemical study of beta-protein in Alzheimer-type dementia brains

An immunohistochemical study with a polyclonal anti-beta-protein antiserum was performed in order to understand the mechanism of deposition of amyloid fibrils in senile plaques in Alzheimer-type dementia (ATD). Serial cortical sections cut from ATD brains were necessary to investigate the structural correlation between senile plaques and blood vessels. The senile plaques were stained well and a blood vessel or capillary-like structure was found in most of beta-protein-immunoreactive deposits. These findings may suggest an involvement of blood vessels in the formation of at least some of the amyloid deposits in ATD brains.

Human cancer and the food chain: an alternative etiologic perspective

Oncogenic viruses are among the known or presumed initiating agents of human cancer. Although evidence suggests that DNA and RNA oncoviruses may be acquired through multiple routes, our attention focuses chiefly on the ingestion pathway. We have two reasons for this. One is the possibility that viral as well as nonviral oncogenic amino acid sequences might be acquired at the top of the food chain. The other is that the food chain-infection hypothesis may reconcile several biological, ecological, and epidemiological phenomena. Transfection experiments suggest that the concept of infection may have to be broadened to embrace the cellular precursors of oncogenic viruses. Accumulating circumstantial evidence from viral oncology and molecular biology provides a basis for the belief that oncogenic viruses and their cellular precursors might be transmitted from animals to humans through the ingestion pathway. The possibility that such transmission may give rise to some human cancers must now be considered. The ingestion and genomic integration of food-associated DNA sequences may directly account for the increased risk of human cancer associated with an elevated intake of animal fat and protein. This paper addresses the role of infective oncogenic agents as the initiators, rather than the promoters, of cancer.

Does the brain's gatekeeper falter in aging?

The brain's gatekeeper, the blood-brain barrier (BBB), may undergo pathologic changes associated with the aging process. Substrate transport through the brain capillary endothelium, which makes up the BBB in vivo, is controlled by dynamic inputs from three other cells (astrocyte, pericyte, and neuron) that form direct physical contacts with the capillary endothelium. Thus, aging-related changes in any of these three cells may cause abnormalities in blood-brain barrier transport in the aged brain or in Alzheimer's disease.

A variety of cerebral amyloid deposits in the brains of the Alzheimer-type dementia demonstrated by beta protein immunostaining

We studied cerebral amyloid deposits in the hippocampal area immunohistochemically, using antiserum to synthetic beta peptide (1-28) in 66 patients with or without dementia and aged 17 to 91 years old. Senile plaques (SP) and amyloid angiopathy (AA) were detected in 36 (55%) and 19 (29%) patients, respectively. Also, cerebral amyloid deposits from the brains of seven patients with dementia and five patients without were studied in serial sections stained with Bodian, modified Bielschowsky, Congo red, and beta protein immunostain. In the patients with Alzheimer-type dementia (ATD) diffuse plaques, typical of this group, were stained with beta protein antiserum but not with Bodian stain, because the plaques were devoid of abnormally swollen neuritic processes. The diffuse plaques often contained one or more neuronal cell bodies. As well as primitive and classic plaques and AA, the beta protein immunostain demonstrated small deposits among the SP, small stellate deposits of layer 1, subpial fibrillar deposits, and focal cribriform deposits of parasubiculum, which may be new types of amyloid deposits. Amyloid plaques within the subcortical white matter were only found in ATD brains. In the non-demented patients various kinds of SP, including diffuse and compact ones, were immunostained. They tended to be small and few. beta protein immunostain with formic acid pretreatment is a useful method for the identification of a variety of senile cerebral amyloid deposits.

Amyloid angiopathy of Alzheimer's disease: amino acid composition and partial sequence of a 4,200-dalton peptide isolated from cortical microvessels

The cardinal lesions of Alzheimer's disease are neurofibrillary tangles, senile neuritic plaques, and vascular amyloid, the latter generally involving cortical arteries and small arterioles. All three lesions are composed of amyloid-like, beta-pleated sheet fibrils. Recently, a 4,200-dalton peptide has been isolated from extraparenchymal meningeal vessels, neuritic plaques, and neurofibrillary tangles. The assumption of N-terminal homogeneity in vascular amyloid has been used as an argument for a neuronal (versus blood) origin of the peptide. However, intracortical microvessels from Alzheimer's disease have not been previously isolated. The present studies describe the isolation of a microvessel fraction from Alzheimer's disease and control fresh autopsy human brain. Alzheimer's disease isolated brain microvessels that were extensively laden with amyloid and control microvessels were solubilized in 90% formic acid and analyzed by urea sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The arteriole fraction from the Alzheimer's subject with extensive amyloid angiopathy contained a unique 4,200-dalton peptide, whereas the arterioles or capillaries isolated from two controls and two Alzheimer's disease subjects without angiopathy did not. This peptide was purified by HPLC and amino acid composition analysis showed the peptide is nearly identical to the 4,200-dalton peptide recently isolated from neuritic plaques or from neurofibrillary tangles. Sequence analysis revealed N-terminal heterogeneity. The N-terminal sequence was: Asp-Ala-Glu-Phe-Arg-His-Asp-Ser-Gly-Tyr, which is identical to the N-terminal sequence of the 4,200-dalton peptide isolated previously from extraparenchymal meningeal vessels and neuritic plaques.(ABSTRACT TRUNCATED AT 250 WORDS)

Diffuse type of senile plaques in the brains of Alzheimer-type dementia

We studied the nature of diffuse type of senile plaques (SP) in the brains of six autopsied subjects with Alzheimer-type dementia (ATD). The densities of SP in the entorhinal cortex were evaluated using serial sections stained by four different methods. Compared with beta protein immunostaining (100% as a reference), the modified Bielschowsky stain (103%) and the periodic acid-methenamine silver (PAM) stain (109%) labeled similar numbers of SP, whereas the Bodian stain labeled only a minor proportion (42%) of these. The vast majority of Bodian-negative plaques were diffuse plaques, which were seen as ill-defined areas of fine fibrillar material after beta protein immunostain with formic acid pretreatment, modified Bielschowsky stain, and PAM stain. They were not stained by Congo red or periodic acid-Schiff stains. Double staining using Bodian and beta protein methods demonstrated that diffuse plaques were free of swollen neurites. Argyrophilia of the diffuse plaques shown by the modified Bielschowsky and PAM stains, became undetectable when sections were pretreated with formic acid. Such treatment made the diffuse plaques immunoreactive to beta protein antiserum, suggesting that diffuse plaques consisted mainly of amyloid, but not neuritic components. The diffuse plaques were distributed in various cortical areas and in the amygdala, and comprised a considerable population of the SP in the ATD brains.