Plasma Aß42/40 ratio alone or combined with FDG-PET can accurately predict amyloid-PET positivity: a cross-sectional analysis from the AB255 Study.

BACKGROUND: To facilitate population screening and clinical trials of disease-modifying therapies for Alzheimer's disease, supportive biomarker information is necessary. This study was aimed to investigate the association of plasma amyloid-beta (Aß) levels with the presence of pathological accumulation of Aß in the brain measured by amyloid-PET. Both plasma Aß42/40 ratio alone or combined with an FDG-PET-based biomarker of neurodegeneration were assessed as potential AD biomarkers. METHODS: We included 39 cognitively normal subjects and 20 patients with mild cognitive impairment from the AB255 Study who had undergone PiB-PET scans. Total Aß40 and Aß42 levels in plasma (TP42/40) were quantified using ABtest kits. Subjects were dichotomized as Aß-PET positive or negative, and the ability of TP42/40 to detect Aß-PET positivity was assessed by logistic regression and receiver operating characteristic analyses. Combination of plasma Aß biomarkers and FDG-PET was further assessed as an improvement for brain amyloidosis detection and diagnosis classification. RESULTS: Eighteen (30.5%) subjects were Aß-PET positive. TP42/40 ratio alone identified Aß-PET status with an area under the curve (AUC) of 0.881 (95% confidence interval [CI] = 0.779-0.982). Discriminating performance of TP42/40 to detect Aß-PET-positive subjects yielded sensitivity and specificity values at Youden's cutoff of 77.8% and 87.5%, respectively, with a positive predictive value of 0.732 and negative predictive value of 0.900. All these parameters improved after adjusting the model for significant covariates. Applying TP42/40 as the first screening tool in a sequential diagnostic work-up would reduce the number of Aß-PET scans by 64%. Combination of both FDG-PET scores and plasma Aß biomarkers was found to be the most accurate Aß-PET predictor, with an AUC of 0.965 (95% CI = 0.913-0.100). CONCLUSIONS: Plasma TP42/40 ratio showed a relevant and significant potential as a screening tool to identify brain Aß positivity in preclinical and prodromal stages of Alzheimer's disease.

Safety, tolerability and immunogenicity of an active anti-Aß40 vaccine (ABvac40) in patients with Alzheimer's disease: a randomised, double-blind, placebo-controlled, phase I trial.

BACKGROUND: Immunotherapy targeting the amyloid-ß (Aß) peptide is a promising strategy for the treatment of Alzheimer's disease (AD); however, none of the active or passive vaccines tested have been demonstrated to be effective to date. We have developed the first active vaccine against the C-terminal end of Aß40, ABvac40, and assessed its safety and tolerability in a phase I clinical trial. METHODS: A randomised, double-blind, placebo-controlled, parallel-group, phase I study of ABvac40 was conducted with patients aged 50-85 years with mild to moderate AD. Participants were entered into three separate groups according to time of study entry and were randomly allocated to receive ABvac40 or placebo (overall ratio 2:1). The first group received two half-doses of ABvac40 or placebo, whereas the second and third groups received two and three full doses, respectively. All treatments were administered subcutaneously at 4-week intervals. Patients, carers and investigators were blind to treatment allocation throughout the study. The primary objective was to assess the safety and tolerability of ABvac40 by registering all adverse events (AEs). All patients who received at least one dose of treatment were included in the safety analysis. The secondary objective was to evaluate the immunogenicity of ABvac40 by titration of specific anti-Aß40 antibodies in plasma. RESULTS: Twenty-four patients were randomly allocated: 16 patients to the ABvac40 group and 8 patients to the placebo group. All randomised patients completed the study, therefore the intention-to-treat and safety populations were identical. Overall, 71 AEs affecting 18 patients were recorded: 11 (69%) in the ABvac40 group and 7 (88%) in the placebo group (p = 0.6214). Neither incident vasogenic oedema nor sulcal effusion (amyloid-related imaging abnormalities corresponding to vasogenic oedema and sulcal effusions) nor microhaemorrhages (amyloid-related imaging abnormalities corresponding to microhaemorrhages and hemosiderin deposits) were detected throughout the study period in the ABvac40-treated patients. Eleven of 12 (~92%) individuals receiving three injections of ABvac40 developed specific anti-Aß40 antibodies. CONCLUSIONS: ABvac40 showed a favourable safety and tolerability profile while eliciting a consistent and specific immune response. An ongoing phase II clinical trial is needed to confirm these results and to explore the clinical efficacy of ABvac40. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03113812 . Retrospectively registered on 14 April 2017.

Blood amyloid beta levels in healthy, mild cognitive impairment and Alzheimer's disease individuals: replication of diastolic blood pressure correlations and analysis of critical covariates.

Plasma amyloid beta (Aß) levels are being investigated as potential biomarkers for Alzheimer's disease. In AB128 cross-sectional study, a number of medical relevant correlates of blood Aß40 or Aß42 were analyzed in 140 subjects (51 Alzheimer's disease patients, 53 healthy controls and 36 individuals diagnosed with mild cognitive impairment). We determined the association between multiple variables with Aß40 and Aß42 levels measured in three different blood compartments called i) Aß directly accessible (DA) in the plasma, ii) Aß recovered from the plasma matrix (RP) after diluting the plasma sample in a formulated buffer, and iii) associated with the remaining cellular pellet (CP). We confirmed that diastolic blood pressure (DBP) is consistently correlated with blood DA Aß40 levels (r=-0.19, P=0.032). These results were consistent in the three phenotypic groups studied. Importantly, the observation resisted covariation with age, gender or creatinine levels. Observed effect size and direction of Aß40 levels/DBP correlation are in accordance with previous reports. Of note, DA Aß40 and the RP Aß40 were also strongly associated with creatinine levels (r=0.599, P<<0.001) and to a lesser extent to urea, age, hematocrit, uric acid and homocysteine (p<0.001). DBP and the rest of statistical significant correlates identified should be considered as potential confounder factors in studies investigating blood Aß levels as potential AD biomarker. Remarkably, the factors affecting Aß levels in plasma (DA, RP) and blood cell compartments (CP) seem completely different.

Several direct and calculated biomarkers from the amyloid-ß pool in blood are associated with an increased likelihood of suffering from mild cognitive impairment.

Validation of cost-effective, non-invasive methods to identify early (pre-clinical) Alzheimer's disease (AD) is increasingly becoming a key research challenge. We have developed two ELISA sandwich colorimetric tests for the accurate detection of amyloid-ß (Aß)1-40 and Aß1-42: i) directly accessible (DA) in the plasma, ii) recovered from the plasma sample (RP) after diluting the plasma sample in a formulated buffer, and iii) associated with the remaining cellular pellet (CP). These tests were carried out on samples from healthy controls (n = 19) and individuals with mild cognitive impairment (MCI; n = 27) with amnestic-hippocampal syndrome to investigate whether this comprehensive approach may help to explain the association between blood Aß levels and MCI. A logistic regression analysis detected seven direct or calculated markers (CP 40, DA 42, RP 42, DA/CP 40, DA/RP 42, DA/CP 42, and DA 42/40) with significant odds ratios (OR) after they were dichotomized with regard to the median of the pooled population. In particular, the likelihood [OR (95% CI)] of having MCI for patients with catCP 40, catDA/RP 42, catDA/CP 42, or catDA 42/40 below the corresponding population median ("positive test") was 11.48 (1.87-70.52), 22.09 (3.19-152.61), 11.48 (1.87-70.50), and 9.54 (1.77-51.38)-fold higher, respectively, than in those with a "negative test" after adjusting for the effect of the ApoE genotype. These results are congruent with the hypothesis that changes in blood Aß levels may be associated with the initial stages of AD. Thus, these Aß blood biomarkers might be useful tools for screening for those at increased risk of developing AD.

Reliable Measurements of the ß-Amyloid Pool in Blood Could Help in the Early Diagnosis of AD.

The present study was aimed at assessing the capability of Aß1-40 and Aß1-42 levels in undiluted plasma (UP), diluted plasma (DP), and cell bound (CB) to distinguish between early stages of Alzheimer's disease (AD), amnesic mild cognitive impairment (MCI), and healthy control (HC). Four blood samples from each participant were collected during one month and the levels of Aß1-40 and Aß1-42 were determined by a blinded proprietary ELISA sandwich (Araclon Biotech. Zaragoza, Spain). First striking result was that the amount of Aß1-40 and Aß1-42 in UP represented only a small proportion (~15%) of the total beta-amyloid pool in blood (ßAPB) described here as the sum of Aß1-40 and Aß1-42 in blood where they are free in plasma, bound to plasma proteins, and bound to blood cells. Furthermore, we found that levels of Aß1-40 and Aß1-42 in UP, DP, and CB were significantly higher in MCI when compared to HC. On average, the total ßAPB was 1.8 times higher in MCI than in HC (P = 0.03) and allowed to discriminate between MCI and HC with a sensitivity and specificity over 80%. Thus, quantification of several markers of the ßAPB could be useful and reliable in the discrimination between MCI and HC.

Cytotoxicity of quinone drugs on highly proliferative human leukemia T cells: reactive oxygen species generation and inactive shortened SOD1 isoform implications.

Drugs containing the quinone group were tested on hyperproliferative leukemia T cells (HLTC: Jhp and Jws) and parental Jurkat cells. Doxorubicin, menadione and adaphostin produced different effects on these cell lines. Rapid doxorubicin-induced cell death in Jurkat cells was mediated by caspase activation. Doxorubicin-induced cell death of HLTCs was delayed due to the absence of caspase-3 and -8 expression. Delayed HLTC cell death was mediated and triggered by the generation of reactive oxygen species (ROS). Other drugs containing quinone groups, such as menadione and adaphostin, were also tested on HLTC and both were toxic by a caspase-independent mechanism. The toxicity of these drugs correlated with the generation of the superoxide anion, which increased and was more effective in HLTCs than in parental Jurkat cells. Accordingly, SOD1 activity was much lower in HLTCs than in Jurkat cells. This lower SOD1 activity in HLTCs was associated not only with the absence of the wild-type (16 kDa) SOD1 monomer but also with the presence of a shortened (14 kDa) SOD1 monomer isoform. Moreover, the cytotoxicity of drugs containing the quinone group was prevented by incubation with manganese(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), a cell-permeable superoxide dismutase mimetic and a potent inhibitor of oxidation. These findings could explain the sensitivity of HLTCs to drugs containing the quinone group using a mechanism dependent on oxidative stress. These observations can also be useful to target hyperproliferative leukemias that are resistant to the classical caspase-dependent apoptotic pathway.

Plasma ß-amyloid peptides in canine aging and cognitive dysfunction as a model of Alzheimer's disease.

Aging dogs naturally demonstrate cognitive impairment and neuropathology that model early Alzheimer's disease (AD). In particular, there is evidence that canine cognitive dysfunction syndrome (CDS) in aged dogs is accompanied by cortical deposition of Aß peptides and neurodegeneration. Plasma Aß levels have been examined in humans as putative biomarkers for AD, but to date, no similar studies have been conducted for canine dementia. The aim of the present study was to assess plasma Aß1-42 and Aß1-40 levels in a blind study using pet dogs that were either successfully aging or exhibiting CDS. The severity of cognitive impairment was assessed using an owner-based questionnaire. On average, young dogs presented significantly higher plasma levels of Aß1-42 and Aß1-40 than aged, cognitively unimpaired dogs. Notably, among aged dogs, the levels of Aß1-42 and the Aß42/40 ratio were significantly higher in those showing mild cognitive impairment than in either cognitively unimpaired or severely affected dogs. These results suggest that increased plasma Aß1-42 levels and Aß42/40 ratio could be a biomarker for canine cognitive dysfunction, which is considered an excellent natural model of early AD.

The clinical significance of plasmatic amyloid A{beta}-40 peptide levels in Alzheimer's disease patients treated with galantamine.

To date there are no conclusive reports on the usefulness of determining amyloid peptides in the serum of patients with Alzheimer's disease (AD). Only anecdotal works deal with the changes in the peptides produced by cholinesterase inhibitors. In this study, the authors investigated and studied the clinical significance of plasmatic Abeta-40 and Abeta-42 peptide levels in a series of 34 consecutive patients with AD. The baseline levels of the Abeta-40 peptide correlated negatively with the Mini Examen Cognoscitivo (Spanish version of the Mini-Mental test) score. Complete follow-up was possible in 22 patients. After 6 months of treatment with galantamine, the mean Abeta-40 peptide levels decreased from 31.86 to 24.22 pg/mL. The baseline levels of Abeta-40 were predictive of response to treatment in the Alzheimer's Disease Assessment Scale-Cognitive Subscale. The authors conclude that determining plasmatic Abeta-40 peptide levels could be useful in predicting and monitoring response to treatment in AD.

Lack of Fas/CD95 surface expression in highly proliferative leukemic cell lines correlates with loss of CtBP/BARS and redirection of the protein toward giant lysosomal structures.

Fas/CD95 is a type-I membrane glycoprotein, which inducesapoptotic cell death when ligated by its physiological ligand. We generated previously hyperproliferative sublines derived from the human T-cell leukemia Jurkat, Jurkat-ws and Jurkat-hp, which lost Fas/CD95 surface expression. We have now observed that the total amount of Fas protein is similar in the sublines and in the parental cells, indicating that in the sublines Fas remains in an intracellular compartment. We have found that the protein is directed toward lysosomes in the sublines, where it is degraded. This defect in the secretory pathway correlates with loss of polyunsaturated fatty acids from cellular lipids, and with the lack of expression of endophilin-I and CtBP/BARS, enzymes that regulate vesicle fission by catalyzing the acylation of arachidonate into lysophosphatidic acid. In addition, great multillamer bodies, which contained acid phosphatase activity, absent in the parental Jurkat cells, were observed by transmission electron microscopy in the sublines.