Innate immunity stimulation via CpG oligodeoxynucleotides ameliorates Alzheimer's disease pathology in aged squirrel monkeys

Identification of Specific Cell Surface Markers on Immune Cells of Squirrel Monkeys (Saimiri sciureus)

Nonhuman primates are an important experimental model for the development of targeted biological therapeutics because of their immunological closeness to humans. However, there are very few antibody reagents relevant for delineating the different immune cell subsets based on nonhuman primate antigens directly or with cross-reactivity to those in humans. Here, we report specific expression of HLA-DR, PD-1, and CD123 on different circulating immune cell subsets in the peripheral blood that included T cells (CD3+), T cells subsets (CD4+ and CD8+), B cells (CD20+), natural killer (NK) cells (CD3-CD16+), and natural killer T cells (CD3+CD16+) along with different monocyte subsets in squirrel monkey (Saimiri sciureus). We established cross-reactivity of commercial mouse antihuman monoclonal antibodies (mAbs), with these various immune cell surface markers. These findings should aid further future comprehensive understanding of the immune parameters and identification of new biomarkers to significantly improve SQM as a model for biomedical studies.

Clearance of interstitial fluid (ISF) and CSF (CLIC) group-part of Vascular Professional Interest Area (PIA), updates in 2022-2023. Cerebrovascular disease and the failure of elimination of Amyloid-β from the brain and retina with age and Alzheimer's disease: Opportunities for therapy

This editorial summarizes advances from the Clearance of Interstitial Fluid and Cerebrospinal Fluid (CLIC) group, within the Vascular Professional Interest Area (PIA) of the Alzheimer's Association International Society to Advance Alzheimer's Research and Treatment (ISTAART). The overarching objectives of the CLIC group are to: (1) understand the age-related physiology changes that underlie impaired clearance of interstitial fluid (ISF) and cerebrospinal fluid (CSF) (CLIC); (2) understand the cellular and molecular mechanisms underlying intramural periarterial drainage (IPAD) in the brain; (3) establish novel diagnostic tests for Alzheimer's disease (AD), cerebral amyloid angiopathy (CAA), retinal amyloid vasculopathy, amyloid-related imaging abnormalities (ARIA) of spontaneous and iatrogenic CAA-related inflammation (CAA-ri), and vasomotion; and (4) establish novel therapies that facilitate IPAD to eliminate amyloid β (Aβ) from the aging brain and retina, to prevent or reduce AD and CAA pathology and ARIA side events associated with AD immunotherapy.

Modeling the neuroimmune system in Alzheimer's and Parkinson's diseases

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders caused by the interaction of genetic, environmental, and familial factors. These diseases have distinct pathologies and symptoms that are linked to specific cell populations in the brain. Notably, the immune system has been implicated in both diseases, with a particular focus on the dysfunction of microglia, the brain's resident immune cells, contributing to neuronal loss and exacerbating symptoms. Researchers use models of the neuroimmune system to gain a deeper understanding of the physiological and biological aspects of these neurodegenerative diseases and how they progress. Several in vitro and in vivo models, including 2D cultures and animal models, have been utilized. Recently, advancements have been made in optimizing these existing models and developing 3D models and organ-on-a-chip systems, holding tremendous promise in accurately mimicking the intricate intracellular environment. As a result, these models represent a crucial breakthrough in the transformation of current treatments for PD and AD by offering potential for conducting long-term disease-based modeling for therapeutic testing, reducing reliance on animal models, and significantly improving cell viability compared to conventional 2D models. The application of 3D and organ-on-a-chip models in neurodegenerative disease research marks a prosperous step forward, providing a more realistic representation of the complex interactions within the neuroimmune system. Ultimately, these refined models of the neuroimmune system aim to aid in the quest to combat and mitigate the impact of debilitating neuroimmune diseases on patients and their families.

Vaccines and Dementia: Part II. Efficacy of BCG and Other Vaccines Against Dementia

 There is growing awareness that infections may contribute to the development of senile dementia including Alzheimer's disease (AD), and that immunopotentiation is therefore a legitimate target in the management of diseases of the elderly including AD. In Part I of this work, we provided a historical and molecular background to how vaccines, adjuvants, and their component molecules can elicit broad-spectrum protective effects against diverse agents, culminating in the development of the tuberculosis vaccine strain Bacille Calmette-Guérin (BCG) as a treatment for some types of cancer as well as a prophylactic against infections of the elderly such as pneumonia. In Part II, we critically review studies that BCG and other vaccines may offer a measure of protection against dementia development. Five studies to date have determined that intravesicular BCG administration, the standard of care for bladder cancer, is followed by a mean ∼45% reduction in subsequent AD development in these patients. Although this could potentially be ascribed to confounding factors, the finding that other routine vaccines such as against shingles (herpes zoster virus) and influenza (influenza A virus), among others, also offer a degree of protection against AD (mean 29% over multiple studies) underlines the plausibility that the protective effects are real. We highlight clinical trials that are planned or underway and discuss whether BCG could be replaced by key components of the mycobacterial cell wall such as muramyl dipeptide. We conclude that BCG and similar agents merit far wider consideration as prophylactic agents against dementia.

Mutated Toll-like receptor 9 increases Alzheimer's disease risk by compromising innate immunity protection

The development of Alzheimer's disease (AD) involves central and peripheral immune deregulation. Gene identification and studies of AD genetic variants of peripheral immune components may aid understanding of peripheral-central immune crosstalk and facilitate new opportunities for therapeutic intervention. In this study, we have identified in a Flanders-Belgian family a novel variant p.E317D in the Toll-like receptor 9 gene (TLR9), co-segregating with EOAD in an autosomal dominant manner. In human, TLR9 is an essential innate and adaptive immune component predominantly expressed in peripheral immune cells. The p.E317D variant caused 50% reduction in TLR9 activation in the NF-κB luciferase assay suggesting that p.E317D is a loss-of-function mutation. Cytokine profiling of human PBMCs upon TLR9 activation revealed a predominantly anti-inflammatory response in contrast to the inflammatory responses from TLR7/8 activation. The cytokines released upon TLR9 activation suppressed inflammation and promoted phagocytosis of Aβ42 oligomers in human iPSC-derived microglia. Transcriptome analysis identified upregulation of AXL, RUBICON and associated signaling pathways, which may underline the effects of TLR9 signaling-induced cytokines in regulating the inflammatory status and phagocytic property of microglia. Our data suggest a protective role of TLR9 signaling in AD pathogenesis, and we propose that TLR9 loss-of-function may disrupt a peripheral-central immune crosstalk that promotes dampening of inflammation and clearance of toxic protein species, leading to the build-up of neuroinflammation and pathogenic protein aggregates in AD development.

Mitochondrial DNA and Inflammation in Alzheimer's Disease

Mitochondrial dysfunction and neuroinflammation are implicated in the pathogenesis of most neurodegenerative diseases, such as Alzheimer's disease (AD). In fact, although a growing number of studies show crosstalk between these two processes, there remain numerous gaps in our knowledge of the mechanisms involved, which requires further clarification. On the one hand, mitochondrial dysfunction may lead to the release of mitochondrial damage-associated molecular patterns (mtDAMPs) which are recognized by microglial immune receptors and contribute to neuroinflammation progression. On the other hand, inflammatory molecules released by glial cells can influence and regulate mitochondrial function. A deeper understanding of these mechanisms may help identify biomarkers and molecular targets useful for the treatment of neurodegenerative diseases. This review of works published in recent years is focused on the description of the mitochondrial contribution to neuroinflammation and neurodegeneration, with particular attention to mitochondrial DNA (mtDNA) and AD.

Alzheimer's Disease: Novel Targets and Investigational Drugs for Disease Modification

Novel agents addressing non-amyloid, non-tau targets in Alzheimer's Disease (AD) comprise 70% of the AD drug development pipeline of agents currently in clinical trials. Most of the target processes identified in the Common Alzheimer's Disease Research Ontology (CADRO) are represented by novel agents in trials. Inflammation and synaptic plasticity/neuroprotection are the CADRO categories with the largest number of novel candidate therapies. Within these categories, there are few overlapping targets among the test agents. Additional categories being evaluated include apolipoprotein E [Formula: see text] 4 (APOE4) effects, lipids and lipoprotein receptors, neurogenesis, oxidative stress, bioenergetics and metabolism, vascular factors, cell death, growth factors and hormones, circadian rhythm, and epigenetic regulators. We highlight current drugs being tested within these categories and their mechanisms. Trials will be informative regarding which targets can be modulated to produce a slowing of clinical decline. Possible therapeutic combinations of agents may be suggested by trial outcomes. Biomarkers are evolving in concert with new targets and novel agents, and biomarker outcomes offer a means of supporting disease modification by the putative treatment. Identification of novel targets and development of corresponding therapeutics offer an important means of advancing new treatments for AD.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

Anti-Amyloid Immunotherapies for Alzheimer's Disease: A 2023 Clinical Update

The amyloid cascade hypothesis is a useful framework for therapeutic development in Alzheimer's disease (AD). Amyloid b1-42 (Aβ) has been the main target of experimental therapies, based on evidence of the neurotoxic effects of Aβ, and of the potential adverse effects of brain Aβ burden detected in humans in vivo by positron emission tomography (PET). Progress on passive anti-amyloid immunotherapy research includes identification of antibodies that facilitate microglial activation, catalytical disaggregation, and increased flow of Aβ from cerebrospinal fluid (CSF) to plasma, thus decreasing the neurotoxic effects of Aβ. Recently completed phase 2 and 3 trials of 3rd generation anti-amyloid immunotherapies are supportive of their clinical efficacy in reducing brain Aβ burden and preventing cognitive decline. Data from recent trials implicate these agents as the first effective disease-modifying therapies against AD and has led to the US Food and Drug Administration (FDA) recent approval of aducanumab and lecanemab, under an accelerated approval pathway. The clinical effects of these agents are modest, however, and associated with amyloid-related imaging abnormalities (ARIA). Testing the effects of anti-Aβ immunotherapies in pre-symptomatic populations and identification of more potent and safer agents is the scope of ongoing and future research. Innovations in clinical trial design will be the key for the efficient and equitable development of novel anti-Aβ immunotherapies. The progress in the field of AD therapeutics will bring new clinical, logistical, and ethical challenges, which pose to revolutionize the practice of neurology, dementia care, and preventive cognitive healthcare.

Early activation of Toll-like receptor-3 reduces the pathological progression of Alzheimer's disease in APP/PS1 mouse

BACKGROUND

Toll-like receptor 3 (TLR3) plays an important role in the immune/inflammatory response in the nervous system and is a main pathological feature of Alzheimer's disease (AD). This study investigates the role of early activation of TLR3 in the pathophysiological process of AD.

METHODS

In the experiment, the agonist of TLR3, Poly(I:C), was intraperitoneally injected into the APP/PS1 mouse model of AD and wild-type control mice starting from the age of 4 to 9 months. At the age of 14 months, behavioral tests were conducted. Western blot and immunohistochemistry staining were used to evaluate the level of amyloid β-protein (Aβ), the activation of inflammatory cells, and neuron loss. In addition, the levels of inflammatory cytokines were measured using a quantitative polymerase chain reaction.

RESULTS

The results demonstrated that the early activation of TLR3 attenuated neuronal loss and neurobehavioral dysfunction. Moreover, the early activation of TLR3 reduced Aβ deposition, inhibited the activation of microglia and astrocytes, and decreased the transcription of pro-inflammatory factors in the hippocampus.

CONCLUSIONS

The results indicated that the activation of TLR3 by Poly (I:C) in the early stage of development of AD in a mouse model attenuated neuron loss and improved neurobehavioral functions. The underlying mechanisms could be attributed to its role in Aβ clearance, the inhibition of glial cells, and the regulation of neuroinflammation in the hippocampus.

Nanomedicine based strategies for oligonucleotide traversion across the blood-brain barrier

Neurological disorders are considered the most prominent cause of disability worldwide. The major hurdle in the management of neurological disorders is the existence of the blood-brain barrier (BBB), which hinders the entry of several therapeutic moieties. In recent years, oligonucleotides have gained tremendous attention for their target specificity, diminished dose and adverse effects, thereby halting disease progression. However, enzymatic degradation, rapid clearance, limited circulation and availability at the bio-active site, etc., limit its clinical translation. Nanomedicine has opened up a breadth of opportunities in the delivery of oligonucleotides across the BBB. This review addresses the pitfalls associated with oligonucleotide delivery in traversing the BBB via nanotherapeutics for the management of brain disorders. Regulatory perspectives pertaining to hastening the clinical translation of oligonucleotide-loaded nanocarriers for brain delivery have been highlighted.

Deletion of Abi3/Gngt2 influences age-progressive amyloid β and tau pathologies in distinctive ways

BACKGROUND

The S209F variant of Abelson Interactor Protein 3 (ABI3) increases risk for Alzheimer's disease (AD), but little is known about its function in relation to AD pathogenesis.

METHODS

Here, we use a mouse model that is deficient in Abi3 locus to study how the loss of function of Abi3 impacts two cardinal neuropathological hallmarks of AD-amyloid β plaques and tau pathology. Our study employs extensive neuropathological and transcriptomic characterization using transgenic mouse models and adeno-associated virus-mediated gene targeting strategies.

RESULTS

Analysis of bulk RNAseq data confirmed age-progressive increase in Abi3 levels in rodent models of AD-type amyloidosis and upregulation in AD patients relative to healthy controls. Using RNAscope in situ hybridization, we localized the cellular distribution of Abi3 in mouse and human brains, finding that Abi3 is expressed in both microglial and non-microglial cells. Next, we evaluated Abi3-/- mice and document that both Abi3 and its overlapping gene, Gngt2, are disrupted in these mice. Using multiple transcriptomic datasets, we show that expression of Abi3 and Gngt2 are tightly correlated in rodent models of AD and human brains, suggesting a tight co-expression relationship. RNAseq of the Abi3-Gngt2-/- mice revealed upregulation of Trem2, Plcg2, and Tyrobp, concomitant with induction of an AD-associated neurodegenerative signature, even in the absence of AD-typical neuropathology. In APP mice, loss of Abi3-Gngt2 resulted in a gene dose- and age-dependent reduction in Aβ deposition. Additionally, in Abi3-Gngt2-/- mice, expression of a pro-aggregant form of human tau exacerbated tauopathy and astrocytosis. Further, using in vitro culture assays, we show that the AD-associated S209F mutation alters the extent of ABI3 phosphorylation.

CONCLUSIONS

These data provide an important experimental framework for understanding the role of Abi3-Gngt2 function and early inflammatory gliosis in AD. Our studies also demonstrate that inflammatory gliosis could have opposing effects on amyloid and tau pathology, highlighting the unpredictability of targeting immune pathways in AD.

Effect of Probiotic Fungi against Cognitive Impairment in Mice via Regulation of the Fungal Microbiota-Gut-Brain Axis

The fungal microbiota may be involved in the regulation of cognition and behavior, while the role of probiotic fungi against cognitive impairment is unclear. Here, we explored the idea that probiotic Saccharomyces boulardii could participate in the regulation of microglia-induced neuroinflammation in Alzheimer's disease (AD) model mice. Cognitive deficits, deposits of amyloid-β (Aβ) and phosphorylation of tau, synaptic plasticity, microglia activation, and neuroinflammatory reactions were observed. The expression levels of Toll-like receptors (TLRs) pathway-related proteins were detected. Meanwhile, intestinal barrier integrity and fungal microbiota composition were evaluated. Our results showed fungal microbiota dysbiosis in APP/PS1 mice, which might result in the neuroinflammation of AD. The increased levels of interleukin (IL)-6, IL-1β, and cluster of differentiation 11b (CD11b) were observed in APP/PS1 mice, which were associated with activation of microglia, indicative of a broader recognition of neuroinflammation mediated by fungal microbiota compared to hitherto appreciated. Probiotic S. boulardii treatment improved dysbiosis, alleviated the neuroinflammation as well as synaptic injury, and ultimately improved cognitive impairment. Moreover, S. boulardii therapy could inhibit microglia activation and the TLRs pathway, which were reversed by antifungal treatment. These findings revealed that S. boulardii actively participated in regulating the TLRs pathway to inhibit the neuroinflammation via the gut-brain axis.

Short-Term Relocation Stress-Induced Hematological and Immunological Changes in Saimiri boliviensis boliviensis

Nonhuman primates are frequently transported to a new location or temporarily relocated within their colony. Both transportation and relocation expose animals to new environments, causing them to undergo a stress response (before adapting). In our NHP colony, the mentioned situations are not infrequent for many reasons, including maintenance. The objective of this study was to determine whether abrupt changes consisting of relocation, housing, separation, and grouping could influence hematological and immunological parameters and thereby functional activity. The current study used squirrel monkeys as a model to investigate the stress-inducing effects of relocation within a facility, while animals acclimated to new situations (physical, housing). A detailed blood analysis revealed significant changes in lymphocytes, triglycerides, total protein, creatinine, and ALT. Flow cytometric analysis of peripheral blood showed reduction in CD3+, CD4+, and CD8+ T cells and monocytes, while B cells and natural killer (NK) cells changed with relocation. Simultaneously, changes in functional activity of immune cells altered proliferative responses and as shown by ELISpot (IFN γ). Though the parameters studied are not affected as severely as those in animals transported by road or air, stress responses induced by intrafacility relocation are significant and worth consideration. Our findings indicate that squirrel monkeys mimic the features seen in humans exposed to social stressors and may serve an important model for understanding the mechanisms of stress-induced immune dysfunction in humans.

Dissecting the Crosstalk between Endothelial Mitochondrial Damage, Vascular Inflammation, and Neurodegeneration in Cerebral Amyloid Angiopathy and Alzheimer's Disease

Alzheimer’s disease (AD) is the most prevalent cause of dementia and is pathologically characterized by the presence of parenchymal senile plaques composed of amyloid β (Aβ) and intraneuronal neurofibrillary tangles of hyperphosphorylated tau protein. The accumulation of Aβ also occurs within the cerebral vasculature in over 80% of AD patients and in non-demented individuals, a condition called cerebral amyloid angiopathy (CAA). The development of CAA is associated with neurovascular dysfunction, blood–brain barrier (BBB) leakage, and persistent vascular- and neuro-inflammation, eventually leading to neurodegeneration. Although pathologically AD and CAA are well characterized diseases, the chronology of molecular changes that lead to their development is still unclear. Substantial evidence demonstrates defects in mitochondrial function in various cells of the neurovascular unit as well as in the brain parenchyma during the early stages of AD and CAA. Dysfunctional mitochondria release danger-associated molecular patterns (DAMPs) that activate a wide range of inflammatory pathways. In this review, we gather evidence to postulate a crucial role of the mitochondria, specifically of cerebral endothelial cells, as sensors and initiators of Aβ-induced vascular inflammation. The activated vasculature recruits circulating immune cells into the brain parenchyma, leading to the development of neuroinflammation and neurodegeneration in AD and CAA.