Natural IgG Autoantibodies Are Abundant and Ubiquitous in Human Sera, and Their Number Is Influenced By Age, Gender, and Disease

The presence of self-reactive IgG autoantibodies in human sera is largely thought to represent a breakdown in central tolerance and is typically regarded as a harbinger of autoimmune pathology. In the present study, immune-response profiling of human serum from 166 individuals via human protein microarrays demonstrates that IgG autoantibodies are abundant in all human serum, usually numbering in the thousands. These IgG autoantibodies bind to human antigens from organs and tissues all over the body and their serum diversity is strongly influenced by age, gender, and the presence of specific diseases. We also found that serum IgG autoantibody profiles are unique to an individual and remarkably stable over time. Similar profiles exist in rat and swine, suggesting conservation of this immunological feature among mammals. The number, diversity, and apparent evolutionary conservation of autoantibody profiles suggest that IgG autoantibodies have some important, as yet unrecognized, physiological function. We propose that IgG autoantibodies have evolved as an adaptive mechanism for debris-clearance, a function consistent with their apparent utility as diagnostic indicators of disease as already established for Alzheimer’s and Parkinson’s diseases

Diagnosis of Parkinson\u27s Disease Based on Disease-Specific Autoantibody Profiles in Human Sera

Parkinson\u27s disease (PD), hallmarked by a variety of motor disorders and neurological decline, is the second most common neurodegenerative disease worldwide. Currently, no diagnostic test exists to identify sufferers, and physicians must rely on a combination of subjective physical and neurological assessments to make a diagnosis. The discovery of definitive blood-borne biomarkers would be a major step towards early and reliable diagnosis. Despite attention devoted to this search, such biomarkers have remained elusive. In the present study, we used human protein microarrays to reveal serum autoantibodies that are differentially expressed among PD and control subjects. The diagnostic significance of each of these autoantibodies was evaluated, resulting in the selection of 10 autoantibody biomarkers that can effectively differentiate PD sera from control sera with a sensitivity of 93.1% and specificity of 100%. PD sera were also distinguishable from sera obtained from Alzheimer\u27s disease, breast cancer, and multiple sclerosis patients with accuracies of 86.0%, 96.6%, and 100%, respectively. Results demonstrate that serum autoantibodies can be used as highly specific and accurate biomarkers for PD diagnosis throughout the course of the disease

Cerebrovascular and Blood-Brain Barrier Compromise: A Mechanistic Link between Vascular Disease and Alzheimer’s Disease Subtypes of Neurocognitive Disorders

Alzheimer’s disease (AD) and vascular dementia (VaD) are the most common subtypes of neurocognitive disorders (NCDs), with overlapping clinical presentation and risk factors. Studies on AD brains have demonstrated increased extravasation of plasma components through a functionally compromised blood-brain barrier (BBB). The BBB includes endothelial cells, astrocyte foot processes, basement membrane, and pericytes, and its function is to maintain brain homeostasis by limiting entry of plasma components into the brain. The pathogenesis of VaD is commonly attributed to cerebrovascular lesions, and neuroimaging studies have demonstrated extravasation of plasma components. Although the pathogenesis of AD and VaD is unknown, much evidence suggests that an abnormal cerebrovasculature may be a common mechanistic link. The primary aims of this review are to highlight studies that embrace or oppose this theory, and to examine the potentially causal relationship between cerebrovascular abnormalities and pathological hallmarks of AD. A major challenge to elucidate the role of the BBB in AD pathology has been the inability to demonstrate BBB dysfunction in neuroimaging studies. Computed tomography and magnetic resonance imaging can detect leakage from larger vessels, significant for VaD, but fail to detect smaller chronic vascular leakages common to AD. The latter are, however, detected by routine immunohistological techniques in postmortem tissues. If we consider AD and VaD from the vascular perspective, they have many features in common. By placing these diseases along a continuum of vascular pathology manifesting as dementia, it becomes apparent that the observed clinical differences are mostly attributable to the extent and location of the vascular leak. Lastly, we propose a novel hypothesis that we believe can potentially account for much of the phenomenology surrounding AD and its pathogenesis, including mechanisms of intraneuronal amyloid deposition and amyloid plaque formation, and the role of the BBB and autoantibodies in this process

Detection of Alzheimer\u27s disease at mild cognitive impairment and disease progression using autoantibodies as blood-based biomarkers

Introduction There is an urgent need to identify biomarkers that can accurately detect and diagnose Alzheimer\u27s disease (AD). Autoantibodies are abundant and ubiquitous in human sera and have been previously demonstrated as disease-specific biomarkers capable of accurately diagnosing mild-moderate stages of AD and Parkinson\u27s disease. Methods Sera from 236 subjects, including 50 mild cognitive impairment (MCI) subjects with confirmed low CSF Aβ42 levels, were screened with human protein microarrays to identify potential biomarkers for MCI. Autoantibody biomarker performance was evaluated using Random Forest and Receiver Operating Characteristic curves. Results Autoantibody biomarkers can differentiate MCI patients from age-matched and gender-matched controls with an overall accuracy, sensitivity, and specificity of 100.0%. They were also capable of differentiating MCI patients from those with mild-moderate AD and other neurologic and non-neurologic controls with high accuracy. Discussion Autoantibodies can be used as noninvasive and effective blood-based biomarkers for early diagnosis and staging of AD

Potential utility of autoantibodies as blood-based biomarkers for early detection and diagnosis of Parkinson’s disease

Introduction There is a great need to identify readily accessible, blood-based biomarkers for Parkinson’s disease (PD) that are useful for accurate early detection and diagnosis. This advancement would allow early patient treatment and enrollment into clinical trials, both of which would greatly facilitate the development of new therapies for PD. Methods Sera from a total of 398 subjects, including 103 early-stage PD subjects derived from the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) study, were screened with human protein microarrays containing 9,486 potential antigen targets to identify autoantibodies potentially useful as biomarkers for PD. A panel of selected autoantibodies with a higher prevalence in early-stage PD was identified and tested using Random Forest for its ability to distinguish early-stage PD subjects from controls and from individuals with other neurodegenerative and non-neurodegenerative diseases. Results Results demonstrate that a panel of selected, blood-borne autoantibody biomarkers can distinguish early-stage PD subjects (90% confidence in diagnosis) from age- and sex-matched controls with an overall accuracy of 87.9%, a sensitivity of 94.1% and specificity of 85.5%. These biomarkers were also capable of differentiating patients with early-stage PD from those with more advanced (mild-moderate) PD with an overall accuracy of 97.5%, and could distinguish subjects with early-stage PD from those with other neurological (e.g., Alzheimer’s disease and multiple sclerosis) and non-neurological (e.g., breast cancer) diseases. Conclusion These results demonstrate, for the first time, that a panel of selected autoantibodies may prove to be useful as effective blood-based biomarkers for the diagnosis of early-stage PD

Extravasated Brain-Reactive Autoantibodies Perturb Neuronal Surface Protein Expression in Alzheimer\u27s Pathology

Background: Increased blood-brain barrier (BBB) permeability is reported in both the neuropathological and in vivo studies in both Alzheimer’s Disease (AD) and age matched cognitively normal, no cognitive impairment (NCI), subjects. Impaired BBB allows various vascular components such as immunoglobulin G (IgG) to extravasate into the brain and specifically bind to various neuronal surface proteins (NSP), also known as brain reactive autoantibodies (BrABs). This interaction is predicted to further enhance deposition of amyloid plaques. Hypothesis: Interaction between extravasated BrABs and its cognate NSPs lower the expression of that NSPs in AD patients. Methods: We selected Western blotting technique to study the expression of various brain proteins and test our hypothesis. Fresh frozen brain samples of AD and NCI subjects were acquired, and total brain protein was extracted using protocol established in Acharya lab. We also identified various NSPs to study the impact of BrABs-NSPs interactions. Additionally, we investigated the expression of amyloid plaques ((amyloid precursor protein (APP)) and apoptosis (Caspase-3) markers. Specific NSPs examined included the alpha7 nicotinic acetylcholine receptor (α7nAChR) and anti-choline acetyltransferase (ChAT). To image the membranes, fluorescent imaging was used initially, which was later switched to chemiluminescence, after much troubleshooting. Results: Most of the work done through these experiments was focused on establishing a thorough Western blot protocol that can be used to reliably perform these experiments. This involved determining the appropriate primary and secondary antibodies concentrations, loading concentrations, and testing different imaging settings to determine the most ideal image-acquisition conditions. Towards the end of the fellowship, we were successful in developing a protocol to further explore our investigation. Using this protocol, we were able to visualize bands for ChAT, α7nAChR, and caspase – 3. Conclusions: Using this protocol further Western blot experiments can be run to study and compare the expression levels of various NSP in AD and control samples for testing our hypothesi

Autoantibodies as Diagnostic Biomarkers for the Detection and Subtyping of Multiple Sclerosis

The goal of this preliminary proof-of-concept study was to use human protein microarrays to identify blood-based autoantibody biomarkers capable of diagnosing multiple sclerosis (MS). Using sera from 112 subjects, including 51 MS subjects, autoantibody biomarkers effectively differentiated MS subjects from age- and gender-matched normal and breast cancer controls with 95.0% and 100% overall accuracy, but not from subjects with Parkinson\u27s disease. Autoantibody biomarkers were also useful in distinguishing subjects with the relapsing-remitting form of MS from those with the secondary progressive subtype. These results demonstrate that autoantibodies can be used as noninvasive blood-based biomarkers for the detection and subtyping of M

Antibodies in the Diagnosis, Prognosis, and Prediction of Psychotic Disorders.

Blood-based biomarker discovery for psychotic disorders has yet to impact upon routine clinical practice. In physical disorders antibodies have established roles as diagnostic, prognostic and predictive (theranostic) biomarkers, particularly in disorders thought to have a substantial autoimmune or infective aetiology. Two approaches to antibody biomarker identification are distinguished: a top-down approach, in which antibodies to specific antigens are sought based on the known function of the antigen and its putative role in the disorder, and emerging bottom-up or omics approaches that are agnostic as to the significance of any one antigen, using high-throughput arrays to identify distinctive components of the antibody repertoire. Here we review the evidence for antibodies (to self-antigens as well as infectious organism and dietary antigens) as biomarkers of diagnosis, prognosis, and treatment response in psychotic disorders. Neuronal autoantibodies have current, and increasing, clinical utility in the diagnosis of organic or atypical psychosis syndromes. Antibodies to selected infectious agents show some promise in predicting cognitive impairment and possibly other symptom domains (eg, suicidality) within psychotic disorders. Finally, infectious antibodies and neuronal and other autoantibodies have recently emerged as potential biomarkers of response to anti-infective therapies, immunotherapies, or other novel therapeutic strategies in psychotic disorders, and have a clear role in stratifying patients for future clinical trials. As in nonpsychiatric disorders, combining biomarkers and large-scale use of bottom-up approaches to biomarker identification are likely to maximize the eventual clinical utility of antibody biomarkers in psychotic disorders

The Brodmann Area 39/40 of the Brain in Alzheimer’s, Mild Cognitive Impairment, and No Cognitive Impairment Subjects at Advanced Age Demonstrate Comparable Levels of Blood-Brain Barrier Breach

• Alzheimer’s disease (AD) is one of the most common form of dementia • Mild cognitive impairment (MCI), specifically amnestic subtype, more likely to progress to AD • Pathogenesis Theories: o Accumulation of amyloid-beta peptides and neurofibrillary tangles containing hyperphosphorylated neuronal tau protein o Blood Brain Barrier (BBB) dysfunction is associated with AD pathogenesis • Brodmann area 39/40: regions of parietal cortex are responsible for language, spatial cognition, memory retrieval, attention, phonological processing, and emotional processing • Hypothesis: An increased BBB permeability in Brodmann area 39/40 of AD and age-matched MCI and no cognitive impairment (NCI) subject

A Preliminary Report: The Hippocampus and Surrounding Temporal Cortex of Patients With Schizophrenia Have Impaired Blood-Brain Barrier

Schizophrenia (SZ) is one of the most severe forms of mental illness, yet mechanisms remain unclear. A widely established brain finding in SZ is hippocampal atrophy, and a coherent explanation similarly is lacking. Epidemiological evidence suggests increased cerebrovascular and cardiovascular complications in SZ independent of lifestyle and medication, pointing to disease-specific pathology. Endothelial cell contributions to blood-brain barrier (BBB) compromise may influence neurovascular unit and peripheral vascular function, and we hypothesize that downstream functional and structural abnormalities may be explained by impaired BBB