A combination of multiple autoantibodies is associated with the risk of Alzheimer’s disease and cognitive impairment

Towards early diagnosis of Alzheimer's disease: advances in immune-related blood biomarkers and computational approaches

Alzheimer's disease has an increasing prevalence in the population world-wide, yet current diagnostic methods based on recommended biomarkers are only available in specialized clinics. Due to these circumstances, Alzheimer's disease is usually diagnosed late, which contrasts with the currently available treatment options that are only effective for patients at an early stage. Blood-based biomarkers could fill in the gap of easily accessible and low-cost methods for early diagnosis of the disease. In particular, immune-based blood-biomarkers might be a promising option, given the recently discovered cross-talk of immune cells of the central nervous system with those in the peripheral immune system. Here, we give a background on recent advances in research on brain-immune system cross-talk in Alzheimer's disease and review machine learning approaches, which can combine multiple biomarkers with further information (e.g. age, sex, APOE genotype) into predictive models supporting an earlier diagnosis. In addition, mechanistic modeling approaches, such as agent-based modeling open the possibility to model and analyze cell dynamics over time. This review aims to provide an overview of the current state of immune-system related blood-based biomarkers and their potential for the early diagnosis of Alzheimer's disease.

Profiling the autoantibody repertoire reveals autoantibodies associated with mild cognitive impairment and dementia

Background

Dementia is a debilitating neurological disease affecting millions of people worldwide. The exact mechanisms underlying the initiation and progression of the disease remain to be fully defined. There is an increasing body of evidence for the role of immune dysregulation in the pathogenesis of dementia, where blood-borne autoimmune antibodies have been studied as potential markers associated with pathological mechanisms of dementia.

Methods

This study included plasma from 50 cognitively normal individuals, 55 subjects with MCI (mild cognitive impairment), and 22 subjects with dementia. Autoantibody profiling for more than 1,600 antigens was performed using a high throughput microarray platform to identify differentially expressed autoantibodies in MCI and dementia.

Results

The differential expression analysis identified 33 significantly altered autoantibodies in the plasma of patients with dementia compared to cognitively normal subjects, and 38 significantly altered autoantibodies in the plasma of patients with dementia compared to subjects with MCI. And 20 proteins had significantly altered autoantibody responses in MCI compared to cognitively normal individuals. Five autoantibodies were commonly dysregulated in both dementia and MCI, including anti-CAMK2A, CKS1B, ETS2, MAP4, and NUDT2. Plasma levels of anti-ODF3, E6, S100P, and ARHGDIG correlated negatively with the cognitive performance scores (MoCA) (r2 -0.56 to -0.42, value of p < 0.001). Additionally, several proteins targeted by autoantibodies dysregulated in dementia were significantly enriched in the neurotrophin signaling pathway, axon guidance, cholinergic synapse, long-term potentiation, apoptosis, glycolysis and gluconeogenesis.

Conclusion

We have shown multiple dysregulated autoantibodies in the plasma of subjects with MCI and dementia. The corresponding proteins for these autoantibodies are involved in neurodegenerative pathways, suggesting a potential impact of autoimmunity on the etiology of dementia and the possible benefit for future therapeutic approaches. Further investigations are warranted to validate our findings.

Beyond the amyloid hypothesis: how current research implicates autoimmunity in Alzheimer's disease pathogenesis

The amyloid hypothesis has so far been at the forefront of explaining the pathogenesis of Alzheimer's Disease (AD), a progressive neurodegenerative disorder that leads to cognitive decline and eventual death. Recent evidence, however, points to additional factors that contribute to the pathogenesis of this disease. These include the neurovascular hypothesis, the mitochondrial cascade hypothesis, the inflammatory hypothesis, the prion hypothesis, the mutational accumulation hypothesis, and the autoimmunity hypothesis. The purpose of this review was to briefly discuss the factors that are associated with autoimmunity in humans, including sex, the gut and lung microbiomes, age, genetics, and environmental factors. Subsequently, it was to examine the rise of autoimmune phenomena in AD, which can be instigated by a blood-brain barrier breakdown, pathogen infections, and dysfunction of the glymphatic system. Lastly, it was to discuss the various ways by which immune system dysregulation leads to AD, immunomodulating therapies, and future directions in the field of autoimmunity and neurodegeneration. A comprehensive account of the recent research done in the field was extracted from PubMed on 31 January 2022, with the keywords "Alzheimer's disease" and "autoantibodies" for the first search input, and "Alzheimer's disease" with "IgG" for the second. From the first search, 19 papers were selected, because they contained recent research on the autoantibodies found in the biofluids of patients with AD. From the second search, four papers were selected. The analysis of the literature has led to support the autoimmune hypothesis in AD. Autoantibodies were found in biofluids (serum/plasma, cerebrospinal fluid) of patients with AD with multiple methods, including ELISA, Mass Spectrometry, and microarray analysis. Through continuous research, the understanding of the synergistic effects of the various components that lead to AD will pave the way for better therapeutic methods and a deeper understanding of the disease.

Risk factors, treatment and survival rates of late-onset acquired haemophilia A: A cohort study from the Shizuoka Kokuho Database

INTRODUCTION

Acquired haemophilia A (AHA) is a rare disease. The risk factors have yet to be studied.

AIM

We aimed to identify risk factors for late-onset AHA in Japan.

METHODS

A population-based cohort study was conducted using data from the Shizuoka Kokuho Database. The study population was defined as individuals aged ≥60 years. Cause-specific Cox regression analysis was performed to calculate hazard ratios.

RESULTS

Of 1,160,934 registrants, there were 34 patients with newly diagnosed AHA. The mean follow-up period was 5.6 years, and the incidence of AHA was 5.21 per million person-years. Myocardial infarction, diabetes mellitus, solid tumors, antimicrobial agents, phenytoin and anti-dementia drugs, which showed significant differences in the univariate analysis, were excluded from the multivariable analysis because of the small number of cases. Multivariable regression analysis showed that the presence of Alzheimer's disease (hazard ratio [HR]:4.28, 95% confidence interval [CI]:1.67-10.97) and rheumatic disease (HR:4.65, 95% CI:1.79-12.12) increased the risk of AHA development.

CONCLUSION

We found that comorbid Alzheimer's disease is a risk factor of AHA incidence in the general population. Our findings provide insight into the etiology of AHA, and the proof of the coexistence of Alzheimer's disease may support the recent notion that Alzheimer disease is an autoimmune disease.

Decrease in naturally occurring antibodies against epitopes of Alzheimer's disease (AD) risk gene products is associated with cognitive decline in AD

BACKGROUND

Naturally occurring antibodies (NAbs) are germline-encoded immunoglobulins that can bind to and clear out self-neo-epitopes as well as apoptotic and necrotic cells. However, NAbs pathological relevance in Alzheimer's disease (AD) is not well-understood.

METHODS

Twenty-eight candidate proteins encoded by AD-associated genes were selected for this study based on a number of selection criteria, including preferential expression in the brain and B-lymphocyte cells. The levels of NAbs in plasma were analyzed according to their epitopes in age- and gender-matched cognitively normal subjects (CN, n = 56), subjects with mild cognitive impairment (MCI, n = 16) and subjects with AD (n = 56). We aimed to study the levels of their NAbs in plasma and their associations with cognitive decline in individuals with AD.

RESULTS

Of the 28 antigens tested, 17 showed decreased NAbs in individuals with AD; in particular, NAb-TREM2 had an area under the ROC curve of 0.806, with the highest sensitivity (0.370) at 95% specificity among all 28 tests. Further protein-protein interaction networks and functional enrichment analysis suggested that target genes were enriched in AD-related pathological processes classified under "Alzheimer's disease", "neurodegenerative disease" and "amyloidosis". The "Alzheimer's disease" and "neurodegenerative disease" clusters, which converged on the initial "recognition" step of microglial phagocytosis, showed the best diagnostic performance for AD.

CONCLUSIONS

This study suggests a decline in the function of the adaptive immune system in AD, and the levels of circulating NAbs are likely to serve as biomarkers for surveilling the progression of AD.

Preserved visuoconstruction in patients with Alzheimer's pathology and anti-neural autoantibodies: A case control study

Background

Alzheimer's disease (AD) is seldom reported to be associated with neural autoantibodies apart from those involved in axonal neurodegeneration and amyloidopathy in prior studies. Nevertheless, this is an under-investigated aspect of AD. As we do not know whether additional screening for autoantibodies in AD patients has additional diagnostic and therapeutic value, this study aims to shed light on whether visuoconstructive or figural memory capacities might distinguish these patient populations.

Methods

In this pilot case series, we investigated eight patients suffering from cognitive impairment associated with cerebrospinal fluid (CSF)-based Alzheimer pathology (AP) and with verified anti-neural autoantibodies (AP Aab+) compared to eight AD patients presenting no autoantibodies (Aab-) (AD Aab-). Patients files were reviewed retrospectively regarding their neuropsychological profile assessed via the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) test battery and psychopathology measured by the AMDP (Manual for the Assessment and Documentation of Psychopathology in Psychiatry) system. We also relied on diagnostic parameters as in the CSF and magnetic resonance images.

Results

All patients shared the same pattern of dysfunctional word-list learning and word-list recall resembling a hippocampus-dependent memory dysfunction. Furthermore, both patient groups revealed a CSF profile concurring with Alzheimer's disease. However, visuoconstructive capacity, but not figure recall was preserved in AP Aab+ patients, but not in AD Ab-patients with the shared hippocampus-based memory dysfunction. We observed no relevant differences between the AP Aab+ and AD Aab- groups in CSF cell-counts or intrathecal IgG synthesis. The relative frequency of hippocampal and focal atrophy did not differ either between AP Aab+ and AD Aab- groups.

Discussion

Our pilot findings are encouraging us to conduct large-scale studies to replicate our discovery of preserved visuoconstruction in AP Aab+ patients with hippocampus-based memory dysfunction. The role of anti-neural autoantibodies is still not fully understood. The detection of these autoantibodies might imply another disease pathology that could be either neuroprotective or be affecting other brain regions, i.e., less pronounced disease activity in the right temporo-parietal regions mainly involved in visuoconstruction.

Glia as antigen-presenting cells in the central nervous system

The contribution of the cells within the central nervous system (CNS) toward adaptive immune responses is emerging and incompletely understood. Recent findings indicate important functional interactions between T-cells and glial cells within the CNS that may contribute to disease and neuropathology through antigen presentation. Although glia are not classically considered antigen-presenting cell (APC) types, there is growing evidence indicating that glial antigen presentation plays an important role in several neurological diseases. This review discusses these findings which incriminate microglia, astrocytes, and oligodendrocyte lineage cells as CNS-resident APC types with implications for understanding disease.