Biomarkers In Biofluids Research Articles

11 Clinical Manifestations of Neuroaxonal Injury

OBJECTIVES/GOALS: The preclinical stage of Alzheimer disease (AD) is a clinically silent period that can be detected through neuroimaging and biofluid biomarkers. The goal of this study was to determine whether performance of complex daily tasks is associated with plasma biomarkers of brain amyloidosis or neuroaxonal injury in cognitively normal (CN) older adults. METHODS/STUDY POPULATION: This is a cross-sectional analysis of an ongoing longitudinal cohort study. CN older adults performed three complex daily tasks (shopping, checkbook balancing, medication management) from the Performance Assessment of Self-Care Skills in their home. Tasks were scored for independence, with more assistance required indicating worse performance. Participants had a plasma sample obtained within two years of completing the tasks. Plasma amyloid (Aβ42 and Aβ40) were evaluated by high precision immunoprecipitation mass spectrometry assays and neurofilament light (NfL) was measured with single molecule array (Simoa) assays. Nonparametric partial correlations were used to quantify the associations between task performance and plasma AD biomarkers, controlling for age and gender. RESULTS/ANTICIPATED RESULTS: 105 CN participants (mean age 74.7 years, 55% female, 88% white) were included. After controlling for age and gender, worse performance of complex daily tasks (more assistance required) was associated with increased plasma NfL (Spearman’s: 0.23, p=0.04) but not plasma Aβ42/Aβ40. DISCUSSION/SIGNIFICANCE: This study suggests that worse performance of complex daily tasks in CN older adults may be associated with increased plasma NfL a marker of neuroaxonal injury, but not with plasma amyloid. These findings could lead to a better understanding of clinical changes that may occur prior to the onset of noticeable memory symptoms in AD or related dementias.

Seed amplification and neurodegeneration marker trajectories in individuals at risk of prion disease.

Human prion diseases are remarkable for long incubation times followed typically by rapid clinical decline. Seed amplification assays and neurodegeneration biofluid biomarkers are remarkably useful in the clinical phase, but their potential to predict clinical onset in healthy people remains unclear. This is relevant not only to the design of preventive strategies in those at-risk of prion diseases, but more broadly, because prion-like mechanisms are thought to underpin many neurodegenerative disorders. Here, we report the accrual of a longitudinal biofluid resource in patients, controls and healthy people at risk of prion diseases, to which ultrasensitive techniques such as real-time quaking-induced conversion (RT-QuIC) and single molecule array (Simoa) digital immunoassays were applied for preclinical biomarker discovery. We studied 648 CSF and plasma samples, including 16 people who had samples taken when healthy but later developed inherited prion disease (IPD) ('converters'; range from 9.9 prior to, and 7.4 years after onset). Symptomatic IPD CSF samples were screened by RT-QuIC assay variations, before testing the entire collection of at-risk samples using the most sensitive assay. Glial fibrillary acidic protein (GFAP), neurofilament light (NfL), tau and UCH-L1 levels were measured in plasma and CSF. Second generation (IQ-CSF) RT-QuIC proved 100% sensitive and specific for sporadic Creutzfeldt-Jakob disease (CJD), iatrogenic and familial CJD phenotypes, and subsequently detected seeding activity in four presymptomatic CSF samples from three E200K carriers; one converted in under 2 months while two remain asymptomatic after at least 3 years' follow-up. A bespoke HuPrP P102L RT-QuIC showed partial sensitivity for P102L disease. No compatible RT-QuIC assay was discovered for classical 6-OPRI, A117V and D178N, and these at-risk samples tested negative with bank vole RT-QuIC. Plasma GFAP and NfL, and CSF NfL levels emerged as proximity markers of neurodegeneration in the typically slow IPDs (e.g. P102L), with significant differences in mean values segregating healthy control from IPD carriers (within 2 years to onset) and symptomatic IPD cohorts; plasma GFAP appears to change before NfL, and before clinical conversion. In conclusion, we show distinct biomarker trajectories in fast and slow IPDs. Specifically, we identify several years of presymptomatic seeding positivity in E200K, a new proximity marker (plasma GFAP) and sequential neurodegenerative marker evolution (plasma GFAP followed by NfL) in slow IPDs. We suggest a new preclinical staging system featuring clinical, seeding and neurodegeneration aspects, for validation with larger prion at-risk cohorts, and with potential application to other neurodegenerative proteopathies.

Universal Fully Integrated Wearable Sensor Arrays for the Multiple Electrolyte and Metabolite Monitoring in Raw Sweat, Saliva, or Urine.

Fully integrated wearable sensors are capable of dynamically, directly, and independently tracking biomarkers in raw noninvasive biofluids without any other equipment or accessories by integrating the unique on-body monitoring feature with the special complete functional implementation attribute. Sweat, saliva, and urine are three important noninvasive biofluids, and changes in their biomarkers hold great potential for revealing physiological conditions. However, it is still a challenge to design single fully integrated wearable sensor arrays (FIWSAs) that are universally able to concurrently measure electrolytes and metabolites in three of the most common noninvasive biofluids including sweat, saliva, and urine. Here, we propose the first single universal FIWSAs for wirelessly, noninvasively, and simultaneously measuring various metabolites (i.e., uric acid) and electrolytes (i.e., Na+ and H+) in raw sweat, saliva, or urine under subjects' exercise by integrating the specifically designed microfluidic, sensing, and electronic modules in a seamless manner. We evaluate its utility for noninvasive gout management in healthy subjects and in gout patients through a purine-rich meal challenge and with a medicine-treatment control, respectively. Noninvasive monitoring of multiple electrolytes and metabolites in a variety of raw noninvasive biofluids via such single universal FIWSAs may enrich the understanding of the biomarkers' levels in the body and would also facilitate self-health management.

Peripheral Biomarkers in Manifest and Premanifest Huntington's Disease.

Huntington's disease (HD) is characterized by clinical motor impairment (e.g., involuntary movements, poor coordination, parkinsonism), cognitive deficits, and psychiatric symptoms. An inhered expansion of the CAG triplet in the huntingtin gene causing a pathogenic gain-of-function of the mutant huntingtin (mHTT) protein has been identified. In this review, we focus on known biomarkers (e.g., mHTT, neurofilament light chains) and on new biofluid biomarkers that can be quantified in plasma or peripheral blood mononuclear cells from mHTT carriers. Circulating biomarkers may fill current unmet needs in HD management: better stratification of patients amenable to etiologic treatment; the initiation of preventive treatment in premanifest HD; and the identification of peripheral pathogenic central nervous system cascades.

Ultralow fouling electrochemical detection of uric acid directly in serum based on phase-transited bovine serum albumin and conducting polymer

Electrochemistry with antifouling sensing interfaces that effectively resist the adsorption of nonspecific biomolecules provides a powerful mean for the accurate and sensitive detection of disease biomarkers in complex biofluids. However, there are few strategies to acquire a stable and solid antifouling coating on any substrate by a simple way. Herein, a simple one-step assembly method has been adopted to construct phase-transited bovine serum albumin (PTB) antifouling layers. Prior to construction of the antifouling layers, the poly(3,4-ethylenedioxythiophene) (PEDOT) doped with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (ionic liquid, IL) were firstly electrodeposited on bare electrodes, endowing good conductivity and catalytic capability for the developed sensor. Subsequently, with the assist of tris(2-carboxyethyl)phosphine (TCEP), the disulfide bonds of bovine serum albumin (BSA) were reduced to form PTB, which can be coated on the PEDOT-IL modified electrode to construct an antifouling electrochemical senor (PTB/PEDOT-IL/GCE) for the detection of uric acid (UA) in human serum. The UA sensor demonstrated a good linear range from 1.11 µmol/L to 798.9 µmol/L, with a high sensitivity of 0.556 µA µmol L−1 cm−2. The combination of conducting polymers with one-step assembly of PTB offers a universal and reliable method for the modification of various electrodes to determine target molecules in complex human body fluids.

Advances in Electrochemical Sensors for Detecting Analytes in Biofluids

AbstractMore than half of all Americans suffer from chronic diseases, the leading causes of death and disability. However, prompt treatment of chronic diseases can lead to better patient outcomes and a reduced burden on the healthcare system. This highlights the urgent need for electrochemical (EC) sensors that provide non‐invasive, real‐time monitoring of disease‐indicating biomarkers. Due to their high sensitivity, high selectivity, and cost‐effectiveness, EC biosensors have recently shown tremendous promise for individualized health monitoring. This review explains the working principles of EC biosensors. It summarizes the recent advances and improvements of EC biosensors for detecting biomarkers in different biofluids, including tears, saliva, breath, urine, and sweat. Through a comprehensive overview of EC biosensor technologies, this article is expected to aid the development of flexible and wearable EC biosensing systems that have the potential to provide continuous, long‐term health monitoring for both clinical and at‐home use.

Multiplex sensing of IL-10 and CRP towards predicting critical illness in COVID-19 infections

Here we present a sensitive method for the detection and quantification of two (IL -10 and CRP) immuno-responsive biomarkers in various biofluids. The significance of these immune response biomarkers lies in them displaying elevated levels in critically ill COVID -19 patients. The developed electrochemical sensor contains a gold film electrode with ZnO nanoparticles deposited on its surface to increase the surface area of the working electrode while integrating antibody-antigen interactions into the detection system. This multiplex biosensor has a wide linear range from 0.01 μg/mL to 100 μg/mL and 0.1 pg/mL to 1000 pg/mL for CRP and IL10, respectively. The cross-reactivity of this multiplex sensor platform was evaluated between these two proteins and was <20%. Recovery studies were performed by spiking known concentrations in serum and urine samples. The recovery was calculated and ranged from 80% to 100%, confirming clinical applicability. This electrochemical sensing platform can aid in the early screening of COVID -19 patients to monitor for the development of more serious and potentially lethal symptoms.

A cork based substrate coupled with artificial antibodies for point-of-care detection of pro-inflammatory cytokine biomarkers

A cork based point of care diagnostic device for monitoring cytokine biomarkers in biofluids.

Emerging molecular biomarkers in osteoarthritis pathology.

Osteoarthritis (OA) is the most common form of arthritis resulting in joint discomfort and disability, culminating in decline in life quality. Attention has been drawn in recent years to disease-associated molecular biomarkers found in readily accessible biofluids due to low invasiveness of acquisition and their potential to detect early pathological molecular changes not observed with traditional imaging methodology. These biochemical markers of OA have been found in synovial fluid, blood, and urine. They include emerging molecular classes, such as metabolites and noncoding RNAs, as well as classical biomarkers, like inflammatory mediators and by-products of degradative processes involving articular cartilage. Although blood-based biomarkers tend to be most studied, the use of synovial fluid, a more isolated biofluid in the synovial joint, and urine as an excreted fluid containing OA biomarkers can offer valuable information on local and overall disease activity, respectively. Furthermore, larger clinical studies are required to determine relationships between biomarkers in different biofluids, and their impacts on patient measures of OA. This narrative review provides a concise overview of recent studies of OA using these four classes of biomarkers as potential biomarker for measuring disease incidence, staging, prognosis, and therapeutic intervention efficacy.

Modular conductive MOF-gated field-effect biosensor for sensitive discrimination on the small molecular scale

Field-effect transistors (FETs) are a promising transducer for biosensors owing to their drastic signal amplification, showing a high sensitivity enough to detect ultra-low concentrations of small-molecular biomarkers in biofluids. However, the discrimination of small molecules from their structural analogues in biofluids using a FET is challenging; because of the 1) Debye screening in high-ionic-strength conditions, 2) few or no charges of the analytes, and 3) lack of target-specific receptors for small molecules. To overcome these limitations, we report a modular conductive MOF (c-MOF)-gated FET biosensor array that discriminates small-molecular neurotransmitters in biofluids. Adsorption and oxidation of analytes inside the pore of catalytic c-MOF films allow the sensitive detection of small molecules close to the clinically relevant concentration, regardless of the ionic strength of the media. The hierarchical screening ability of c-MOF attributed to their tunable pore size, surface charge, and host–guest interactions induces differentiated adsorption of small molecules. The cross-reaction intended by c-MOF design of our biosensor could provide discriminatory information of each neurotransmitter corresponding to the differences of one functional group in the molecule. Using our system, we also demonstrate discrimination capability under the interference of biologically relevant substances and artificial cerebrospinal fluid.

Point of Care testing: The future of periodontal dis-ease diagnosis and monitoring

Manual probing and periodontal charting are the gold standard for periodontal diagnosis that have been used in practice over a century. These methods are affordable and reliable but they are associated with some drawbacks that cannot be avoided. Among these issues is their reliance on operator’s skills, time-consuming and tedious procedure, lack sensitivity especially in cases of early bone loss, and causing discomfort to the patient. Availability of a wide range of biomarkers in the oral biofluids, dental biofilm, and tissues that potentially reflect the periodontal health and disease accurately encouraged their use as predictive/diagnostic/monitoring tools. Analysing biomarkers during care-giving to the patient using chairside kits is known as Point of Care (POC) testing. Introduction of POC in periodontal practice could provide more flexibility and add further dimensions to the process of diagnosis and tailoring more precise treatment plan for the patients. This review aimed to highlight available POC testing used for periodontal diagnosis and disease prediction/monitoring

The ExTINGUISH Trial: A Phase-2B Randomized Placebo-Controlled Trial of Inebilizumab in Anti-NMDA Receptor Encephalitis

Objective To assess the safety and efficacy of inebilizumab in patients with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis. Background The lack of approved therapies for NMDAR encephalitis has led to substantial variability in treatment. High-quality data is needed to guide treatment and optimize long-term outcomes in recovering patients. Inebilizumab is a humanized anti-CD19 monoclonal antibody that can be administered intravenously with good CSF penetration and high target engagement. Inebilizumab may be an efficacious treatment for NMDAR encephalitis, with the potential to achieve early robust and sustained suppression of NMDAR autoantibodies and CD19+ plasmablasts and plasma cells leading to better long-term outcomes. Design/Methods The ExTINGUISH trial is a Phase 2B randomized double-blind placebo-controlled trial designed to evaluate the safety and efficacy of inebilizumab 300 mg for the acute treatment of moderate-to-severe NMDAR encephalitis. 120 participants will be enrolled at 20 US and two European sites (Barcelona, Spain; Rotterdam, The Netherlands). All patients will receive standard “first-line” immunotherapies prior to randomization. Cyclophosphamide IV rescue therapy will be provided after 6 weeks to patients who fail to respond to initial treatment. Motor, cognitive, and functional outcomes will be assessed over 96 weeks. Study operations will be supported via the NINDS-supported NeuroNEXT infrastructure. Results Primary outcomes will be ascertained at 16 weeks using the change in modified Rankin scale (adjusted for rescue therapy) and accepted safety measures. Comprehensive neuropsychological tests, bedside cognitive screening tools, and quality of life/ functional indices will be measured across study participation (secondary outcomes). Clinical data will be combined with biofluid biomarkers of immune activation to inform the biologic contributors to outcomes and identify surrogate endpoints that may be used in future clinical trials (tertiary outcomes). Conclusions ExTINGUISH Trial findings will immediately influence patient care, while informing the design and implementation of future clinical trials in autoimmune encephalitis.

Single-Particle Optical Imaging for Ultrasensitive Bioanalysis.

The quantitative detection of critical biomolecules and in particular low-abundance biomarkers in biofluids is crucial for early-stage diagnosis and management but remains a challenge largely owing to the insufficient sensitivity of existing ensemble-sensing methods. The single-particle imaging technique has emerged as an important tool to analyze ultralow-abundance biomolecules by engineering and exploiting the distinct physical and chemical property of individual luminescent particles. In this review, we focus and survey the latest advances in single-particle optical imaging (OSPI) for ultrasensitive bioanalysis pertaining to basic biological studies and clinical applications. We first introduce state-of-the-art OSPI techniques, including fluorescence, surface-enhanced Raman scattering, electrochemiluminescence, and dark-field scattering, with emphasis on the contributions of various metal and nonmetal nano-labels to the improvement of the signal-to-noise ratio. During the discussion of individual techniques, we also highlight their applications in spatial-temporal measurement of key biomarkers such as proteins, nucleic acids and extracellular vesicles with single-entity sensitivity. To that end, we discuss the current challenges and prospective trends of single-particle optical-imaging-based bioanalysis.

A multimodal pilot study of default mode network (DMN) connectivity across the lifespan in healthy volunteers using functional imaging, CSF, and plasma Alzheimer's disease biomarkers

AbstractBackgroundNormal aging is associated with decreased functional connectivity (FC) in the brain’s default mode network (DMN). Additionally, cerebral burden of both amyloid‐β (Aβ) and tau proteins further contribute to decreased DMN FC in the course of the normal aging process (Wales and Leung, 2021). However, the current literature is sparse and unclear as to the independent actions of Aβand tau on FC of DMN, with tau being associated with general hypoconnectivity (Wales and Leung, 2021). The current pilot study examines resting state fMRI (rsfMRI) data in conjunction with Alzheimer’s Amyloid/Tau/Neurodegeneration (ATN) biofluid biomarkers in healthy individuals, using the isthmus cingulate of the retrosplenial cortex as seed for FC analysis of the DMN.MethodrsfMRI scans are collected in the LifeSPAN Biobanking project [ongoing]. Scans are preprocessed utilizing standard FreeSurfer pipeline. Standard parcellations are assigned using the Desikan‐Killiany atlas. In initial analyses, isthmus cingulate served as the seed for DMN analysis using the FSFAST processing stream within FreeSurfer. ATN biomarkers are obtained from cerebrospinal fluid (CSF) and the following biomarker ratios were computed: Aβ42/Aβ40 (Aβ ratio) and phosphorylated tau‐181 (pTau181) / total Tau (tTau) (pTau181/tTau ratio).ResultIn the initial 14 participants (aged 26‐82 years) [Table 1], General Linear Models (GLMs), adjusted for age, were utilized to evaluate the associations between DMN FC and the following AD biomarkers: Aβ40, Aβ42, Aβ ratio, tTau, pTau181, and pTau181/tTau ratio [Table 2; Figure 1]. After correcting for multiple comparisons (p&lt;0.05), significant association between tTau, and the FC between the DMN and the right inferior temporal region was observed [Table 3].ConclusionThe pilot analysis indicates at least tTau has an association with DMN FC, but sample size precludes conclusion or interpretation. Preliminary data obtained in this exploratory analysis provides a framework for examining the effect of AD biomarkers on the DMN and other functional networks. Future research will incorporate synaptic, inflammatory and other markers into similar statistical models and report preliminary associations. Reference Wales R, Leung H‐C. The Effects of Amyloid and Tau on Functional Network Connectivity in Older Populations. Brain. 2021;142(8):2483‐2491. doi:10.1093/brain/awz162

Biofluid biomarkers in an ethnoracially diverse population and their association with AD

AbstractBackgroundPlasma‐based biomarkers of Alzheimer’s disease are cost‐effective, minimally invasive and highly scalable tools to aid in clinical practice and trials. There remain significant gaps in our understanding of the factors that influence their levels. The majority of fluid biomarker research has been conducted in clinical settings using CSF biomarkers with non‐Hispanic Whites. Although Hispanic and African American communities have higher rates of dementia, there is limited research on blood‐based biomarkers of AD in these communities. The current study of a sample of Mexican Americans, African Americans and Non‐Hispanic Whites investigated the performance of plasma biomarker across the three largest ethnic/racial groups in the US to assess the impact of ethnicity/race on the level of the plasma biomarkers of Aβ40, Aβ42, total tau, ptau 181 and NfL.MethodParticipants were 2200 community dwelling older adults (850 Mexican Americans (MA); 850 Non‐Hispanic Whites (NHW) and 500 African Americans (AA) drawn from The Health &amp; Aging Brain Study – Health Disparities (HABS‐HD) study. Cognitive diagnoses were assigned using an algorithm verified by consensus review. Samples were assayed using Simoa technology. Levels of each biomarker were compared for the three ethnoracial groups across cognitive diagnoses.ResultsSignificant differences were found across the groups at each level of cognitive impairment. For those with normal cognition AA had significantly lower levels of each of the biomarkers and NHW had higher levels of Aβ40, Aβ42 and NFL. MA had the highest level of t tau and p tau 181. MCI group NHW had the highest levels on all the biomarkers and AA had the lowest. NHW and MA has higher levels of Aβ40, Aβ42, total tau, ptau 181 compared to AA. NHW levels of NfL were the highest and MA and AA did not differ. For dementia there was no difference between the groups for Aβ42. NHW had significantly higher levels of Aβ40, t tau, ptau 181 and NfL than AA.ConclusionFindings support the importance of considering ethnoracial background in the clinical use of blood‐based biomarkers and the difficulty of establishing universal cutting points for these biomarkers in the diagnostic process.

Using Proteomics Analysis to Identify Cerebrospinal Fluid Biomarkers in Normal Pressure Hydrocephalus

AbstractBackgroundNormal Pressure Hydrocephalus (NPH) is a neurological condition where there is enlarged ventricular size with normal opening pressure at lumbar puncture. Etiology is uncertain but it is presumed to occur from an imbalance in the production and/or absorption of cerebrospinal fluid (CSF) leading to expansion of the ventricles. Clinical features include gait dysfunction, cognitive impairments, bladder incontinence. Diagnosis is challenging, given a large overlap in clinical and neuroradiological features and co‐morbidity with other more common diseases of aging, especially Alzheimer’s disease (AD) and Lewy body diseases. CSF amyloid and tau biomarkers can be helpful to identify AD pathology but do not exclude concurrent NPH. Currently, there are no biofluid biomarkers to assist in diagnosis of NPH. Here we describe a proteomic discovery pilot to identify candidate protein biomarkers associated with NPH.Method176 banked CSF samples from the MassGeneral Institute for Neurodegenerative Disease biorepository were separated into three groups: NPH (n=30), AD (n=65), and cognitively unimpaired neurological controls (CU‐N; n=81). Diagnoses were established based on comprehensive chart review and CSF AD biomarkers. For proteomic analysis, samples were prepared in batches and analyzed by LC‐MS/MS on an Orbitrap Fusion using a data‐independent acquisition method with non‐overlapping windows from 400‐1000 m/z. Batches were run sequentially, and raw files were searched per batch using Scaffold‐DIA and a custom data‐dependent generated library.ResultFive proteins present in hemoglobulin (HBD and HBB), immunoglobulins (LV39 and KV105), and fibrinogen (FIBA) were increased in NPH compared to AD (Benjamini‐Hochberg adjusted p‐value pAdj &lt;0.05). CSF erythrocyte counts were undetectable in all but one NPH subjects suggesting that a traumatic LP was not the cause of the increased levels. Two neuron associated proteins (VGF and NPTXR) were detected at lower levels in NPH compared to CU‐N subjects (pAdj&lt;0.0001). Alpha‐1‐antichymotrypsin (AACT), was detected at high concentrations both in NPH and AD compared to CU‐N subjects (pAdj&lt;0.02).ConclusionProteomic analysis in NPH may identify novel pathological processes involved in the disease process and aid in the development of biomarkers in NPH.

Worse Performance of Complex Daily Activities is associated with Plasma Neurofilament Light

AbstractBackgroundThe preclinical stage of Alzheimer disease (AD) is a clinically silent period that is detectable through neuroimaging and biofluid biomarkers of amyloid, tau, and neurodegeneration. We evaluated whether performance of cognitively‐focused complex daily activities is associated with plasma biomarkers of brain amyloidosis or neuroaxonal injury in cognitively normal (CN) older adults.MethodIn this cross‐sectional analysis of an ongoing longitudinal cohort study, CN older adults performed three cognitively‐focused complex daily activtites (shopping, checkbook balancing, and medication management) from the Performance Assessment of Self‐Care Skills (PASS) in their home. PASS tasks were scored for independence of performance, with more assistance required indicating worse performance. Participants also had a plasma sample obtained within two years of completing the PASS. Plasma amyloid (Aβ42 and Aβ40) were evaluated by high precision immunoprecipitation mass spectrometry assays and neurofilament light (NfL), a marker of neuroaxonal injury, was measured with single molecule array (Simoa) assays. Amyloid Probability Score (APS) was calculated from a combination of plasma Aβ42/Aβ40, APOE status, and age and reflects the likelihood that an individual will be amyloid positive on an amyloid positron emission tomography (PET) scan. Nonparametric partial correlations were used to examine the associations between PASS performance and biomarkers of AD (plasma Aβ42/Aβ40, APS, and plasma NfL), controlling for age and sex.Result105 CN participants (mean age 74.7 years, 55% female, 88% white) were included. After controlling for age and sex, worse performance of complex daily tasks (more assistance required) was associated with increased plasma NfL (Spearman’s ρ: 0.234, p = 0.04) but not plasma Aβ42/Aβ40 or APS.ConclusionThis study suggests that worse performance of complex daily activities in CN older adults may be associated with increased plasma NfL, a marker of neuroaxonal injury, but not with other plasma biomarkers of brain amyloidosis (plasma Aβ42/Aβ40 or APS). These findings could lead to a better understanding of functional changes that may associate with neuroaxonal injury prior to the onset of noticeable memory symptoms in AD or related dementias.

Chronic Treatment Study Using Class C CpG ODN in Aged Non‐Human Primate Model of Sporadic CAA (Saimiri boliviensis boliviensis).

AbstractBackgroundTherapeutics that target innate immunity present promising avenues for the treatment of Alzheimer’s disease (AD) neuropathology. Our recently published study using squirrel monkeys (SQMs), a non‐human primate model of sporadic AD with extensive cerebral amyloid angiopathy (CAA), demonstrated that treatment with TLR9 agonist, Class B CpG ODN, safely reduces cognitive deficits and pathological features including parenchymal amyloid deposits, tau pathology, and CAA. Subsequently, we initiated the first chronic treatment study using Class C CpG ODN, and demonstrated its safety and efficacy in eliciting an immune response in a geriatric SQM population. Here, we assess the efficacy of Class C CpG ODN by evaluating plasma biomarkers of neurodegeneration and cognitive status using an innovative computerized testing system.MethodGeriatric SQMs received monthly injections of Class C CpG ODN or saline. Plasma biomarkers of neurodegeneration (NfL, GFAP), neuroinflammation (YKL‐40/CHI3L1), and Aβ40/42 autoantibodies were detected longitudinally using Luminex, SIMOA, or ELISA assays. Furthermore, we have implemented an innovative, touchscreen‐based Automated Cognitive Testing System (ACTS) among socially living SQMs to monitor behavioral changes. Actical® activity monitors recorded general activity parameters (step count, activity count, energy expenditure, and intensity level).ResultPlasma levels of NfL, GFAP, and YKL‐40 were significantly increased in saline‐administered monkeys compared to CpG ODN‐treated cohort. No changes were observed in both treatment groups in general activity parameters. Longitudinal plasma hematological/biochemical parameters and Aβ40/42 IgG and IgM titers revealed no differences between treatment groups, further validating the safety of our immunomodulatory approach. Geriatric SQMs completed the ACTS SHAPE training tasks to a 95% criterion of success within 10 days and are progressing through advanced cognitive tests [Match‐to‐Sample (MTS) and Two‐Choice Discrimination]. Preliminary MTS testing revealed that CpG ODN‐treated group performed with a greater response accuracy than saline controls over the last 1000 trials. Additional biofluid biomarkers and cognitive assessments are being finalized. Longitudinal gene expression profiles (RNA‐seq and NanoString analyses) involved in CpG ODN pathways using PBMCs are underway.ConclusionOur findings enhance the translational value of the SQM model for preclinical research on AD and CAA pathogenesis, as we continue to demonstrate Class C CpG ODN’s safety and therapeutic efficacy in geriatric SQMs.

Serum metabolites associate with biofluid neurofilament light chain in Alzheimer’s disease

AbstractBackgroundNeurodegeneration is one of the main components of A/T/N (amyloid/ tau/ neurodegeneration) classification. Recently, neurofilament light chain (NFL), a neuronal protein that is expressed in myelinated axons, has been increasingly recognized as a biomarker of neurodegeneration. In this study, we performed large‐scale association analysis of serum metabolites with NFL in Alzheimer’s disease.MethodWe performed cross‐sectional and longitudinal association analysis of serum metabolome with plasma and CSF NFL in Alzheimer’s disease (AD), after adjusting for multiple testing (N=1,317 for 140 metabolites). Subjects who had both NFL and metabolomics panel data were included. Metabolites were measured using a targeted metabolomics approach using the AbsoluteIDQ‐p180 kit.ResultWe identified 70 metabolites including acylcarnitines sphingomyelins, biogenic amines, amino acids, and glycerophospholipids as significantly associated with baseline plasma NFL, where we identified sex‐specific and APOE ε4‐specific metabolites. Of those, eight metabolites (C16:1, C18:1, SM(OH) C14:1, SM(OH) C16:1, SM C20:2, PC.aa.C28.1, PC.ae.C30.2, and PC.ae. C32.2) were also associated with baseline cerebrospinal fluid NFL and 10 metabolites (C9, C10:2, citrulline, creatinine, SDMA, PC.ae.C34.2, PC.ae.C36.2, PC.ae. C36.3, SM C20:2, and SM C16:0) were associated with change rates of plasma NFL in AD. Metabolites with significant associations were related to biological functions including amyloid precursor protein processing, neuroinflammation, nitric oxide production, and renal function. There were two significant interactions between sex and two medium‐chain acylcarnitine metabolites (C8 and C10) on plasma NFL levels.ConclusionOur present study provides insight into the association of serum‐based circulating metabolites with biofluid biomarker evidence of neurodegeneration, which is closely related to overt clinical symptoms in AD. Metabolites found in our study are related to various biological functions or associated with known risk factors of AD.

Hippocampal CA1 volume is associated with higher p‐tau and diminished memory performance in normal older adults

AbstractBackgroundPrior work has demonstrated that elevated CSF biomarkers in older adults are associated with diminished performance across several hippocampally‐dependent memory tasks. It is unknown whether early structural changes in medial temporal lobe subfields (1) may be impacted by elevated p‐tau181, and (2) mediate the effect of p‐tau181 on memory performance in older adults.MethodThe current study draws on a cohort of 147 cognitively unimpaired older adults (Stanford Aging and Memory Study) that completed both 3T MRI and lumbar punctures. To examine memory performance, participants completed two hippocampally dependent tasks: a paired associate cued recall task and a mnemonic discrimination task (MST) that examined discrimination between previously studied “old” objects, novel “foil” objects and perceptually similar “lure” objects. Lure trials were binned in five difficulty levels, ranging from low to high similarity compared to previously presented stimuli. Hippocampal subregions (CA1, CA3/DG, subiculum) were manually delineated on T2*weighted images following Carr et al., (2017). CSF was processed with Lumipulse to measure Ab42:Ab40 ratio and p‐tau181. Multiple regression was used to assess the associative memory d’ from the paired associate task. Given the repeated measures design of the MST task, linear mixed models were conducted to understand the association between hippocampal subfields and p‐tau181 on performance as a function of similarity strength (Trelle et al., 2021). Age, sex, and education were controlled in all models.ResultP‐tau181 was correlated with reduced left CA1 volume (partial r2=0.043, p = 0.01), but not with volume in other hippocampal subfields. Increased CA1 volume was positively associated with better memory performance, including higher associative memory recall and old‐lure discrimination. After controlling for p‐tau181, CA1 volume was no longer associated with performance on the associative memory task but remained significantly correlated with old/lure discrimination. Notably, increased CA1 volume improved overall discrimination for old/lure trials, independent of the difficulty level, while the association between p‐tau181 and performance was strongest at the lower similarity level.ConclusionReduced CA1 volume and p‐tau explain unique variance in memory performance in older adults. This combination of biofluid biomarkers and high‐resolution MRI has the potential to understand mechanisms underlying age‐related memory decline.