Herpes Simplex Virus Type 1 and Other Pathogens are Key Causative Factors in Sporadic Alzheimer's Disease

Systematic review of amyloid-beta clearance proteins from the brain to the periphery: implications for Alzheimer's disease diagnosis and therapeutic targets

Amyloid-beta clearance plays a key role in the pathogenesis of Alzheimer's disease. However, the variation in functional proteins involved in amyloid-beta clearance and their correlation with amyloid-beta levels remain unclear. In this study, we conducted meta-analyses and a systematic review using studies from the PubMed, Embase, Web of Science, and Cochrane Library databases, including journal articles published from inception to June 30, 2023. The inclusion criteria included studies comparing the levels of functional proteins associated with amyloid-beta clearance in the blood, cerebrospinal fluid, and brain of healthy controls, patients with mild cognitive impairment, and patients with Alzheimer's disease. Additionally, we analyzed the correlation between these functional proteins and amyloid-beta levels in patients with Alzheimer's disease. The methodological quality of the studies was assessed via the Newcastle‒Ottawa Scale. Owing to heterogeneity, we utilized either a fixed-effect or random-effect model to assess the 95% confidence interval (CI) of the standard mean difference (SMD) among healthy controls, patients with mild cognitive impairment, and patients with Alzheimer's disease. The findings revealed significant alterations in the levels of insulin-degrading enzymes, neprilysin, matrix metalloproteinase-9, cathepsin D, receptor for advanced glycation end products, and P-glycoprotein in the brains of patients with Alzheimer's disease, patients with mild cognitive impairment, and healthy controls. In cerebrospinal fluid, the levels of triggering receptor expressed on myeloid cells 2 and ubiquitin C-terminal hydrolase L1 are altered, whereas the levels of TREM2, CD40, CD40L, CD14, CD22, cathepsin D, cystatin C, and α2 M in peripheral blood differ. Notably, TREM2 and cathepsin D showed changes in both brain (SMD = 0.31, 95% CI: 0.16-0.47, P < 0.001, I2 = 78.4%; SMD = 1.24, 95% CI: 0.01-2.48, P = 0.048, I2 = 90.1%) and peripheral blood (SMD = 1.01, 95% CI: 0.35-1.66, P = 0.003, I2 = 96.5%; SMD = 7.55, 95% CI: 3.92-11.18, P < 0.001, I2 = 98.2%) samples. Furthermore, correlations were observed between amyloid-beta levels and the levels of TREM2 ( r = 0.16, 95% CI: 0.04-0.28, P = 0.009, I2 = 74.7%), neprilysin ( r = -0.47, 95% CI: -0.80-0.14, P = 0.005, I2 = 76.1%), and P-glycoprotein ( r = -0.31, 95% CI: -0.51-0.11, P = 0.002, I2 = 0.0%) in patients with Alzheimer's disease. These findings suggest that triggering receptor expressed on myeloid cells 2 and cathepsin D could serve as potential diagnostic biomarkers for Alzheimer's disease, whereas triggering receptor expressed on myeloid cells 2, neprilysin, and P-glycoprotein may represent potential therapeutic targets.

Infections, genetics, and Alzheimer's disease: Exploring the pathogenic factors for innovative therapies

Alzheimer's disease (AD) is a progressive neurodegenerative condition that creates a significant global health challenge and profoundly affects patients and their families. Recent research has highlighted the critical role of microorganisms, particularly viral infections, in the pathogenesis of AD. The involvement of viral infections in AD pathogenesis is predominantly attributed to their ability to induce neuroinflammation and amyloid beta (Aβ) deposition in the brain. The extant research exploring the relationship between viruses and AD has focused largely on Herpesviridae family. Traces of Herpesviruses, such as Herpes Simplex Virus-1 and Epstein Barr Virus, have been found in the brains of patients with AD. These viruses are thought to contribute to the disease progression by triggering chronic inflammatory responses in the brain. They can remain dormant in the brain, and become reactivated due to stress, a secondary viral infection, or immune-senescence in older adults. This review focuses on the association between Herpesviridae and bacterial infections with AD. We explore the genetic factors that might regulate viral illness and discuss clinical trials investigating antiviral and anti-inflammatory agents as possible therapeutic strategies to mitigate cognitive decline in patients with AD. In summary, understanding the interplay between infections, genetic factors, and AD pathogenesis may pave the way for novel therapeutic approaches, facilitating better management and possibly even prevent this debilitating disease.

Precision delivery of pretreated macrophage-membrane-coated Pt nanoclusters for improving Alzheimer's disease-like cognitive dysfunction induced by Porphyromonas gingivalis

Oral infection with Porphyromonas gingivalis (P. gingivalis), a kind of pathogenic bacteria causing periodontitis, can increase the risk of Alzheimer's disease (AD) and cause cognitive decline. Therefore, precise intracerebral antimicrobial therapy to reduce the load of P. gingivalis in brain may serve as a potential therapeutic approach to improve AD-like cognitive impairment. A kind of nano-delivery system precisely targets bacteria in the brain through coating P. gingivalis stimulated macrophage membrane onto the surface of platinum nanoclusters (Pg-M-PtNCs). Approximate 50 nm spherical Pg-M-PtNCs demonstrate good biocompatibility and the pretreated macrophage membranes can inhibit macrophages phagocytosis and increase the adherence to bacteria. Pg-M-PtNCs can significantly inhibit the growth of P.gingivalis in vitro, and are effectively delivered and remain at the infection site in the mice brain to reduce the bacterial load and neuronal damage, and then improve the AD-like cognitive dysfunction in the chronic periodontitis mice. Platinum nanoclusters coated with P. gingivalis pretreated macrophage membrane play an important role in targeting bacteria in the brain, and effectively improve AD-like cognitive function disorder caused by P. gingivalis infection in the brain.

SARS-CoV-2: A synergy to the Alzheimer's disease

COVID-19 was a nightmare in humankind's history that challenged our advanced medical technology. All credit goes to the researchers who played a crucial role in curbing COVID-19 and proved our medical technology supremacy. However, COVID-19 has left some mysterious scars on human well-being. It is believed that COVID-19 has a significant negative impact on various cardiovascular (CVS) and central nervous system (CNS) diseases, especially in the case of CNS diseases like Alzheimer's. Surprisingly, COVID-19 affects the respiratory system, whereas Alzheimer's disease (AD) alters brain function. To explain this phenomenon, several hypotheses were proposed, but the mechanism needs to be clearly understood. Another critical thing to be concerned about is that COVID-19 will worsen pre-existing conditions and lead to the onset of AD. In the race to curb COVID-19, the invention of vaccines was speeded up, and it is necessary to fight against COVID-19. However, postvaccination follow-up is mandatory when an individual is a victim of AD. In this review article, we compiled the various dreadful effects of the COVID-19 virus on AD, the Post effects of the virus on AD, and the effect of the COVID-19 vaccination on AD. This article provides a new direction for research concerning COVID-19 and AD.

Interleukin 1β receptor and synaptic dysfunction in recurrent brain infection with Herpes simplex virus type-1

Several experimental evidence suggests a link between brain Herpes simplex virus type-1 infection and the occurrence of Alzheimer's disease. However, the molecular mechanisms underlying this association are not completely understood. Among the molecular mediators of synaptic and cognitive dysfunction occurring after Herpes simplex virus type-1 infection and reactivation in the brain neuroinflammatory cytokines seem to occupy a central role. Here, we specifically reviewed literature reports dealing with the impact of neuroinflammation on synaptic dysfunction observed after recurrent Herpes simplex virus type-1 reactivation in the brain, highlighting the role of interleukins and, in particular, interleukin 1β as a possible target against Herpes simplex virus type-1-induced neuronal dysfunctions.

Anti-herpetic tau preserves neurons via the cGAS-STING-TBK1 pathway in Alzheimer's disease

Alzheimer's disease (AD) diagnosis relies on the presence of extracellular β-amyloid (Aβ) and intracellular hyperphosphorylated tau (p-tau). Emerging evidence suggests a potential link between AD pathologies and infectious agents, with herpes simplex virus 1 (HSV-1) being a leading candidate. Our investigation, using metagenomics, mass spectrometry, western blotting, and decrowding expansion pathology, detects HSV-1-associated proteins in human brain samples. Expression of the herpesvirus protein ICP27 increases with AD severity and strongly colocalizes with p-tau but not with Aβ. Modeling in human brain organoids shows that HSV-1 infection elevates tau phosphorylation. Notably, p-tau reduces ICP27 expression and markedly decreases post-infection neuronal death from 64% to 7%. This modeling prompts investigation into the cGAS-STING-TBK1 pathway products, nuclear factor (NF)-κB and IRF-3, which colocalizes with ICP27 and p-tau in AD. Furthermore, experimental activation of STING enhances tau phosphorylation, while TBK1 inhibition prevents it. Together, these findings suggest that tau phosphorylation acts as an innate immune response in AD, driven by cGAS-STING.

The role of inhibitory immune checkpoint receptors in the pathogenesis of Alzheimer's disease

There is mounting evidence that microglial cells have a key role in the pathogenesis of Alzheimer's disease (AD). In AD pathology, microglial cells not only are unable to remove β-amyloid (Aβ) plaques and invading pathogens but also are involved in synaptic pruning, chronic neuroinflammation, and neuronal degeneration. Microglial cells possess many different inhibitory immune checkpoint receptors, such as PD-1, LILRB2-4, Siglecs, and SIRPα receptors, which can be targeted by diverse cell membrane-bound and soluble ligand proteins to suppress the functions of microglia. Interestingly, in the brains of AD patients there are elevated levels of many of the inhibitory ligands acting via these inhibitory checkpoint receptors. For instance, Aβ oligomers, ApoE4, and fibronectin are able to stimulate the LILRB2-4 receptors. Increased deposition of sialoglycans, e.g., gangliosides, inhibits microglial function via Siglec receptors. AD pathology augments the accumulation of senescent cells, which are known to possess a high level of PD-L1 proteins, and thus, they can evade immune surveillance. A decrease in the expression of SIRPα receptor in microglia and its ligand CD47 in neurons enhances the phagocytic pruning of synapses in AD brains. Moreover, cerebral neurons contain inhibitory checkpoint receptors which can inhibit axonal growth, reduce synaptic plasticity, and impair learning and memory. It seems that inappropriate inhibitory immune checkpoint signaling impairs the functions of microglia and neurons thus promoting AD pathogenesis. KEY MESSAGES: Microglial cells have a major role in the pathogenesis of AD. A decline in immune activity of microglia promotes AD pathology. Microglial cells and neurons contain diverse inhibitory immune checkpoint receptors. The level of ligands for inhibitory checkpoint receptors is increased in AD pathology. Impaired signaling of inhibitory immune checkpoint receptors promotes AD pathology.

Olfactory and trigeminal routes of HSV-1 CNS infection with regional microglial heterogeneity

Herpes simplex virus type 1 (HSV-1) primarily targets the oral and nasal epithelia before establishing latency in the trigeminal ganglion (TG) and other peripheral ganglia. HSV-1 can also infect and become latent in the central nervous system (CNS) independent of latency in the TGs. Recent studies suggest entry to the CNS via two distinct routes: the TG-brainstem connection and olfactory nerve; however, to date, there is no characterization of brain regions targeted during HSV-1 primary infection. Furthermore, the immune response by microglia may also contribute to the heterogeneity between different brain regions. However, the response to HSV-1 by microglia has not been characterized in a region-specific manner. This study investigated the time course of HSV-1 spread within the olfactory epithelium (OE) and CNS following intranasal inoculation and the corresponding macrophage/microglial response in a C57BL/6 mouse model. We found an apical to basal spread of HSV-1 within the OE and underlying tissue accompanied by an inflammatory response of macrophages. OE infection was followed by infection of a small subset of brain regions targeted by the TG in the brainstem and other cranial nerve nuclei, including the vagus and hypoglossal nerve. Furthermore, other brain regions were positive for HSV-1 antigens, such as the locus coeruleus (LC), raphe nucleus (RaN), and hypothalamus while sparing the hippocampus and cortex. Within each brain region, microglia activation also varied widely. These findings provide critical insights into the region-specific dissemination of HSV-1 within the CNS, elucidating potential mechanisms linking viral infection to neurological and neurodegenerative diseases.IMPORTANCEThis study shows how herpes simplex virus type 1 (HSV-1) spreads within the brain after infecting the nasal passages. Our data reveal the distinct pattern of HSV-1 through the brain during a non-encephalitic infection. Furthermore, microglial activation was also temporally and spatially specific, with some regions of the brain having sustained microglial activation even in the absence of viral antigens. Previous reports have identified specific brain regions found to be positive for HSV-1 infection; however, to date, there has not been a concise investigation of the anatomical spread of HSV-1 and the brain regions consistently vulnerable to viral entry and spread. Understanding these region-specific differences in infection and immune response is crucial because it links HSV-1 infection to potential triggers for neurological and neurodegenerative diseases.

Immunotherapeutic approaches for Alzheimer's disease: Exploring active and passive vaccine progress

Alzheimer's disease (AD) is the most common neurodegeneration having non-effective treatments. Vaccines or monoclonal antibodies are two typical immunotherapies for AD. Due to Aβ neurotoxicity, most of the treatments target its generation and deposition. However, therapies that specifically target tau protein are also being investigated. UB311 vaccine generates N-terminal anti-Aβ antibodies, that neutralize Aβ toxicity and promote plaque clearance. It is designed to elicit specific B-cell and wide T-cell responses. ACC001 or PF05236806 vaccine has the same Aβ fragment and QS21 as an adjuvant. CAD106 stimulates response against Aβ1-6. However, Nasopharyngitis and injection site erythema are its side effects. AN1792, the first-generation vaccine was formulated in proinflammatory QS21 adjuvant. However, T-cell epitopes are omitted from the developed epitope AD vaccine with Aβ1-42B-cell epitopes. The first-generation vaccine immune response was immensely successful in clearing Aβ, but it was also sufficient to provoke meningoencephalitis. Immunotherapies have been at the forefront of these initiatives in recent years. The review covers the recent updates on active and passive immunotherapy for AD.

Olfactory and Trigeminal Routes of HSV-1 CNS Infection with Regional Microglial Heterogeneity

Herpes simplex virus type 1 (HSV-1) primarily targets the oral and nasal epithelia before establishing latency in the trigeminal and other peripheral ganglia (TG). HSV-1 can also infect and go latent in the central nervous system (CNS) independent of latency in the TGs. Recent studies suggest entry to the CNS via two distinct routes: the TG-brainstem connection and olfactory nerve; however, to date, there is no characterization of brain regions targeted during HSV-1 primary infection. Furthermore, the immune response by microglia may also contribute to the heterogeneity between different brain regions. However, the response to HSV-1 by microglia has not been characterized in a region-specific manner. This study investigated the time course of HSV-1 spread within the olfactory epithelium (OE) and CNS following intranasal inoculation and the corresponding macrophage/microglial response in a C57BL/6 mouse model. We found an apical to basal spread of HSV-1 within the OE and underlying tissue accompanied by an inflammatory response of macrophages. OE Infection was followed by infection of a small subset of brain regions targeted by the TG in the brainstem, as well as other cranial nerve nuclei, including the vagus and hypoglossal nerve. Furthermore, other brain regions were positive for HSV-1 antigens, such as the locus coeruleus (LC), raphe nucleus (RaN), and hypothalamus, while sparing the hippocampus and cortex. Within each brain region, microglia activation also varied widely. These findings provide critical insights into the region-specific dissemination of HSV-1 within the CNS, elucidating potential mechanisms linking viral infection to neurological and neurodegenerative diseases.

Importance

This study sheds light on how herpes simplex virus type 1 (HSV-1) spreads within the brain after infecting the nasal passages. Our data reveals the distinct pattern of HSV-1 through the brain during a non-encephalitic infection. Furthermore, microglial activation was also temporally and spatially specific, with some regions of the brain having sustained microglial activation even in the absence of viral antigen. Previous reports have identified specific regions of the brain found to be positive for HSV-1 infection; however, to date, there has not been a concise investigation of the anatomical spread of HSV-1 and the regions of the brain consistently vulnerable to viral entry and spread. Understanding these region-specific differences in infection and immune response is crucial because it links HSV-1 infection to potential triggers for neurological and neurodegenerative diseases.

Cardiovascular and Neurological Diseases and Association with Helicobacter Pylori Infection-An Overview

This article investigates the link between Helicobacter pylori (H. pylori) infection and cardiovascular and neurological disorders. Recent research suggests that H. pylori may play a role in cardiovascular diseases like atherosclerosis, myocardial infarction, and stroke, as well as neurological diseases including Alzheimer's disease, multiple sclerosis, and Parkinson's disease. Cardiovascular Diseases: H. pylori induces endothelial dysfunction and chronic inflammation, promoting atherosclerotic plaque formation and other cardiac complications. High infection prevalence in cardiovascular patients implies that systemic inflammation from H. pylori accelerates disease progression. Eradication therapies combined with anti-inflammatory and lipid-lowering treatments may reduce cardiovascular risk. Neurological Diseases: H. pylori may contribute to Alzheimer's, multiple sclerosis, and Parkinson's through systemic inflammation, neuroinflammation, and autoimmune responses. Increased infection prevalence in these patients suggests bacterial involvement in disease pathogenesis. The eradication of H. pylori could reduce neuroinflammation and improve outcomes. Discussions and Future Research: Managing H. pylori infection in clinical practice could impact public health and treatment approaches. Further research is needed to clarify these relationships. Longitudinal and mechanistic studies are essential to fully understand H. pylori's role in these conditions. Conclusions: H. pylori infection is a potential risk factor for various cardiovascular and neurological conditions. Additional research is critical for developing effective prevention and treatment strategies. Targeted therapies, including H. pylori eradication combined with anti-inflammatory treatments, could improve clinical outcomes. These findings highlight the need for an integrated clinical approach to include H. pylori evaluation and treatment.

Regional Differences in Microbial Infiltration of Brain Tissue from Alzheimer's Disease Patients and Control Individuals

Alzheimer's disease (AD) is characterized by cognitive decline and neuropathology including amyloid beta (Aβ) plaques and neurofibrillary tangles (tau). Factors initiating or driving these pathologies remain unclear, though microbes have been increasingly implicated. Our data and others' findings indicate that microbes may be common constituents of the brain. It is notable that Aβ and tau have antimicrobial properties, suggesting a response to microbes in the brain. We used 16S rRNA sequencing to compare major bacterial phyla in post-mortem tissues from individuals exhibiting a range of neuropathology and cognitive status in two brain regions variably affected in AD. Our data indicate that strong regional differences exist, driven in part by the varied presence of Proteobacteria and Firmicutes. We confirmed our data using ELISA of bacterial lipopolysaccharide (LPS) and lipoteichoic acid in the same brain tissue. We identified a potential association between the composition of phyla and the presence of neuropathology but not cognitive status. Declining cognition and increasing pathology correlated closely with serum LPS, but not brain levels of LPS, although brain LPS showed a strong negative correlation with cerebral amyloid angiopathy. Collectively, our data suggest a region-specific heterogeneity of microbial populations in brain tissue potentially associated with neurodegenerative pathology.

SARS-CoV-2 Nucleocapsid Protein Induces Tau Pathological Changes That Can Be Counteracted by SUMO2

Neurologic manifestations are an immediate consequence of SARS-CoV-2 infection, the etiologic agent of COVID-19, which, however, may also trigger long-term neurological effects. Notably, COVID-19 patients with neurological symptoms show elevated levels of biomarkers associated with brain injury, including Tau proteins linked to Alzheimer's pathology. Studies in brain organoids revealed that SARS-CoV-2 alters the phosphorylation and distribution of Tau in infected neurons, but the mechanisms are currently unknown. We hypothesize that these pathological changes are due to the recruitment of Tau into stress granules (SGs) operated by the nucleocapsid protein (NCAP) of SARS-CoV-2. To test this hypothesis, we investigated whether NCAP interacts with Tau and localizes to SGs in hippocampal neurons in vitro and in vivo. Mechanistically, we tested whether SUMOylation, a posttranslational modification of NCAP and Tau, modulates their distribution in SGs and their pathological interaction. We found that NCAP and Tau colocalize and physically interact. We also found that NCAP induces hyperphosphorylation of Tau and causes cognitive impairment in mice infected with NCAP in their hippocampus. Finally, we found that SUMOylation modulates NCAP SG formation in vitro and cognitive performance in infected mice. Our data demonstrate that NCAP induces Tau pathological changes both in vitro and in vivo. Moreover, we demonstrate that SUMO2 ameliorates NCAP-induced Tau pathology, highlighting the importance of the SUMOylation pathway as a target of intervention against neurotoxic insults, such as Tau oligomers and viral infection.

Peripheral immune function and Alzheimer's disease: a living systematic review and critical appraisal

BACKGROUND

A growing body of literature examines the relationship between peripheral immune function and Alzheimer's Disease (AD) in human populations. Our living systematic review summarizes the characteristics and findings of these studies, appraises their quality, and formulates recommendations for future research.

METHODS

We searched the electronic databases PubMed, PsycINFO, and Web of Science, and reviewed references of previous reviews and meta-analyses to identify human studies examining the relationship between any peripheral immune biomarkers and AD up to September 7th, 2023. We examined patterns of reported statistical associations (positive, negative, and null) between each biomarker and AD across studies. Evidence for each biomarker was categorized into four groups based on the proportion of studies reporting different associations: corroborating a positive association with AD, a negative association, a null association, and presenting contradictory findings. A modified Newcastle-Ottawa scale (NOS) was employed to assess the quality of the included studies.

FINDINGS

In total, 286 studies were included in this review. The majority were cross-sectional (n = 245, 85.7%) and hospital-based (n = 248, 86.7%), examining relationships between 187 different peripheral immune biomarkers and AD. Cytokines were the most frequently studied group of peripheral immune biomarkers. Evidence supported a positive association with AD for six biomarkers, including IL-6, IL-1β, IFN-γ, ACT, IL-18, and IL-12, and a negative association for two biomarkers, including lymphocytes and IL-6R. Only a small proportion of included studies (n = 22, 7.7%) were deemed to be of high quality based on quality assessment.

INTERPRETATION

Existing research on peripheral immune function and AD exhibits substantial methodological variations and limitations, with a notable lack of longitudinal, population-based studies investigating a broad range of biomarkers with prospective AD outcomes. The extent and manner in which peripheral immune function can contribute to AD pathophysiology remain open questions. Given the biomarkers that we identified to be associated with AD, we posit that targeting peripheral immune dysregulation may present a promising intervention point to reduce the burden of AD.

Associations of infections and vaccines with Alzheimer's disease point to a role of compromised immunity rather than specific pathogen in AD

INTRODUCTION

Diverse pathogens (viral, bacterial, fungal) have been associated with Alzheimer's disease (AD) and related traits in various studies. This suggests that compromised immunity, rather than specific microbes, may play a role in AD by increasing an individual's vulnerability to various infections, which could contribute to neurodegeneration. If true, then vaccines that have heterologous effects on immunity, extending beyond protection against the targeted disease, may hold a potential for AD prevention.

METHODS

We evaluated the associations of common adult infections (herpes simplex, zoster (shingles), pneumonia, and recurrent mycoses), and vaccinations against shingles and pneumonia, with the risks of AD and other dementias in a pseudorandomized sample of the Health and Retirement Study (HRS).

RESULTS

Shingles, pneumonia and mycoses, diagnosed between ages 65 and 75, were all associated with significantly increased risk of AD later in life, by 16 %-42 %. Pneumococcal and shingles vaccines administered between ages 65-75 were both associated with a significantly lower risk of AD, by 15 %-21 %. These effects became less pronounced when AD was combined with other dementias.

DISCUSSION

Our findings suggest that both the pneumococcal polysaccharide vaccine and the live attenuated zoster vaccine can offer significant protection against AD. It remains to be determined if non-live shingles vaccine has a similar beneficial effect on AD. This study also found significant associations of various infections with the risk of AD, but not with the risks of other dementias. This indicates that vulnerability to infections may play a more significant role in AD than in other types of dementia, which warrants further investigation.

Single-cell transcriptome reveals highly complement activated microglia cells in association with pediatric tuberculous meningitis

Background

Tuberculous meningitis (TBM) is a devastating form of tuberculosis (TB) causing high mortality and disability. TBM arises due to immune dysregulation, but the underlying immune mechanisms are unclear.

Methods

We performed single-cell RNA sequencing on peripheral blood mononuclear cells (PBMCs) and cerebrospinal fluid (CSF) cells isolated from children (n=6) with TBM using 10 xGenomics platform. We used unsupervised clustering of cells and cluster visualization based on the gene expression profiles, and validated the protein and cytokines by ELISA analysis.

Results

We revealed for the first time 33 monocyte populations across the CSF cells and PBMCs of children with TBM. Within these populations, we saw that CD4_C04 cells with Th17 and Th1 phenotypes and Macro_C01 cells with a microglia phenotype, were enriched in the CSF. Lineage tracking analysis of monocyte populations revealed myeloid cell populations, as well as subsets of CD4 and CD8 T-cell populations with distinct effector functions. Importantly, we discovered that complement-activated microglial Macro_C01 cells are associated with a neuroinflammatory response that leads to persistent meningitis. Consistently, we saw an increase in complement protein (C1Q), inflammatory markers (CRP) and inflammatory factor (TNF-α and IL-6) in CSF cells but not blood. Finally, we inferred that Macro_C01 cells recruit CD4_C04 cells through CXCL16/CXCR6.

Discussion

We proposed that the microglial Macro_C01 subset activates complement and interacts with the CD4_C04 cell subset to amplify inflammatory signals, which could potentially contribute to augment inflammatory signals, resulting in hyperinflammation and an immune response elicited by Mtb-infected tissues.

The associations of herpes simplex virus and varicella zoster virus infection with dementia: a nationwide retrospective cohort study

BACKGROUND

In this study, the risk of dementia in patients with a history of herpes simplex virus (HSV) or varicella zoster virus (VZV) infection was evaluated.

METHODS

This nationwide cohort study used data from the Korean National Health Insurance Service collected between 2006 and 2017. A total of 752,205 subjects ≥ 45 years of age not diagnosed with dementia until 2006 were included. A multivariate Cox regression model, adjusted for age, sex, and other comorbidities, was used to assess the hazard ratio (HR) for dementia based on VZV or HSV infection. The interaction effects of both viral infections were analysed. Viral infections are classified into four categories: eye, central nervous system (CNS), simple, and complicated. The hazard ratio (HR) of viral infection was analysed based on the type of dementia.

RESULTS

In multivariable analysis, both HSV and VZV infection were associated with an increased risk of dementia (HR = 1.38, 95% confidence interval, CI:1.33-1.43) and (HR = 1.41, 95% CI:1.37-1.46), respectively. Patients who experienced both HSV and VZV infections were also at an increased risk of dementia (HR = 1.57, 95% CI:1.50-1.63). The co-infection group showed the shortest time from viral infection to dementia diagnosis (4.09 ± 3.02 years). In the subgroup analysis, all types of HSV and VZV infections were associated with an increased risk of dementia compared to the non-infection group. The eye, CNS, and complicated VZV infections were associated with a significantly higher risk than simple VZV infections. There were no significant differences between the subtypes of HSV infection. Furthermore, HSV, VSV, and co-infection were associated with an increased risk of all dementia types, including Alzheimer's disease (AD) and vascular dementia (VD).

CONCLUSIONS

Individual HSV and VZV infections were associated with an increased risk of all types of dementia, including AD and VD. Patients co-infected with HSV and VZV, VZV infection in the eye, CNS, or complicated type were more vulnerable to the development of dementia.

Intermittent cytomegalovirus infection alters neurobiological metabolism and induces cognitive deficits in mice

Risk factors contributing to dementia are multifactorial. Accumulating evidence suggests a role for pathogens as risk factors, but data is largely correlative with few causal relationships. Here, we demonstrate that intermittent murine cytomegalovirus (MCMV) infection of mice, alters blood brain barrier (BBB) permeability and metabolic pathways. Increased basal mitochondrial function is observed in brain microvessels cells (BMV) exposed to intermittent MCMV infection and is accompanied by elevated levels of superoxide. Further, mice score lower in cognitive assays compared to age-matched controls who were never administered MCMV. Our data show that repeated systemic infection with MCMV, increases markers of neuroinflammation, alters mitochondrial function, increases markers of oxidative stress and impacts cognition. Together, this suggests that viral burden may be a risk factor for dementia. These observations provide possible mechanistic insights through which pathogens may contribute to the progression or exacerbation of dementia.

Peripheral inflammation is a potential etiological factor in Alzheimer's disease

Peripheral inflammation could constitute a risk factor for AD. This review summarizes the research related to peripheral inflammation that appears to have a relationship with Alzheimer's disease. We find there are significant associations between AD and peripheral infection induced by various pathogens, including herpes simplex virus type 1, cytomegalovirus, Epstein-Barr virus, human immunodeficiency virus, severe acute respiratory syndrome coronavirus 2, Porphyromonas gingivalis, Helicobacter pylori, and Toxoplasma gondii. Chronic inflammatory diseases are also reported to contribute to the pathophysiology of AD. The mechanisms by which peripheral inflammation affects the pathophysiology of AD are complex. Pathogen-derived neurotoxic molecule composition, disrupted BBB, and dysfunctional neurogenesis may all play a role in peripheral inflammation, promoting the development of AD. Anti-pathogenic medications and anti-inflammatory treatments are reported to decrease the risk of AD. Studies that could improve understanding the associations between AD and peripheral inflammation are needed. If our assumption is correct, early intervention against inflammation may be a potential method of preventing and treating AD.

Associations of infections and vaccines with Alzheimer's disease point to a major role of compromised immunity rather than specific pathogen in AD

INTRODUCTION

Diverse pathogens (viral, bacterial, fungal) have been linked to Alzheimer's disease (AD) indicating a possibility that the culprit may be compromised immunity rather than particular microbe. If true, then vaccines with broad beneficial effects on immunity might be protective against AD.

METHODS

We estimated associations of common adult infections, including herpes simplex, zoster (shingles), pneumonia, and recurrent mycoses, as well as vaccinations against shingles and pneumonia, with the risk of AD in a pseudorandomized sample of the Health and Retirement Study.

RESULTS

Shingles, pneumonia, and mycoses diagnosed between ages 65-75, were all associated with higher risk of AD later in life, by 16%-42%. Pneumococcal and shingles vaccines received between ages 65-75 both lowered the risk of AD, by 15%-21%.

DISCUSSION

Our results support the idea that the connection between AD and infections involves compromised immunity rather than specific pathogen. We discuss mechanisms by which the declining immune surveillance may promote AD, and the role of biological aging in it. Repurposing of vaccines with broad beneficial effects on immunity could be a reasonable approach to AD prevention. Pneumococcal and zoster vaccines are promising candidates for such repurposing.

Intermittent therapy with helicase-primase inhibitor IM-250 efficiently controls recurrent herpes disease and reduces reactivation of latent HSV

Herpes is a contagious life-long infection with persistently high incidence and prevalence, causing significant disease worldwide. Current therapies have efficacy against active HSV infections but no impact on the latent viral reservoir in neurons. Thus, despite treatment, disease recurs from latency and the infectious potential remains unaffected within patients. Here, efficacy of the helicase-primase inhibitor (HPI) IM-250 against chronic neuronal HSV infections utilizing two classic herpes in vivo latency/reactivation animal models (intravaginal guinea pig HSV-2 infection model and ocular mouse HSV-1 infection model) is presented. Intermittent therapy of infected animals with 4-7 cycles of IM-250 during latency silences subsequent recurrences analyzed up to 6 months. In contrast to common experience, our studies show that the latent reservoir is indeed accessible to antiviral therapy altering the latent viral reservoir such that reactivation frequency can be reduced significantly by prior IM-250 treatment. We provide evidence that antiviral treatment during HSV latency can reduce future reactivation from the latent reservoir, supporting a conceptual shift in the antiviral field, and reframing what is achievable with respect to therapy of latent neuronal HSV infections.

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.

Effect of Systemic Inflammation in the CNS: A Silent History of Neuronal Damage

Central nervous system (CNS) infections including meningitis and encephalitis, resulting from the blood-borne spread of specific microorganisms, provoke nervous tissue damage due to the inflammatory process. Moreover, different pathologies such as sepsis can generate systemic inflammation. Bacterial lipopolysaccharide (LPS) induces the release of inflammatory mediators and damage molecules, which are then released into the bloodstream and can interact with structures such as the CNS, thus modifying the blood-brain barrier's (BBB´s) and blood-cerebrospinal fluid barrier´s (BCSFB´s) function and inducing aseptic neuroinflammation. During neuroinflammation, the participation of glial cells (astrocytes, microglia, and oligodendrocytes) plays an important role. They release cytokines, chemokines, reactive oxygen species, nitrogen species, peptides, and even excitatory amino acids that lead to neuronal damage. The neurons undergo morphological and functional changes that could initiate functional alterations to neurodegenerative processes. The present work aims to explain these processes and the pathophysiological interactions involved in CNS damage in the absence of microbes or inflammatory cells.

Gut Microbiota is an Impact Factor based on the Brain-Gut Axis to Alzheimer's Disease: A Systematic Review

Alzheimer's disease (AD) is a degenerative disease of the central nervous system. The pathogenesis of AD has been explained using cholinergic, β-amyloid toxicity, tau protein hyperphosphorylation, and oxidative stress theories. However, an effective treatment method has not been developed. In recent years, with the discovery of the brain-gut axis (BGA) and breakthroughs made in Parkinson's disease, depression, autism, and other diseases, BGA has become a hotspot in AD research. Several studies have shown that gut microbiota can affect the brain and behavior of patients with AD, especially their cognitive function. Animal models, fecal microbiota transplantation, and probiotic intervention also provide evidence regarding the correlation between gut microbiota and AD. This article discusses the relationship and related mechanisms between gut microbiota and AD based on BGA to provide possible strategies for preventing or alleviating AD symptoms by regulating gut microbiota.

Role of Innate Interferon Responses at the Ocular Surface in Herpes Simplex Virus-1-Induced Herpetic Stromal Keratitis

Herpes simplex virus type 1 (HSV-1) is a highly successful pathogen that primarily infects epithelial cells of the orofacial mucosa. After initial lytic replication, HSV-1 enters sensory neurons and undergoes lifelong latency in the trigeminal ganglion (TG). Reactivation from latency occurs throughout the host's life and is more common in people with a compromised immune system. HSV-1 causes various diseases depending on the site of lytic HSV-1 replication. These include herpes labialis, herpetic stromal keratitis (HSK), meningitis, and herpes simplex encephalitis (HSE). HSK is an immunopathological condition and is usually the consequence of HSV-1 reactivation, anterograde transport to the corneal surface, lytic replication in the epithelial cells, and activation of the host's innate and adaptive immune responses in the cornea. HSV-1 is recognized by cell surface, endosomal, and cytoplasmic pattern recognition receptors (PRRs) and activates innate immune responses that include interferons (IFNs), chemokine and cytokine production, as well as the recruitment of inflammatory cells to the site of replication. In the cornea, HSV-1 replication promotes type I (IFN-α/β) and type III (IFN-λ) IFN production. This review summarizes our current understanding of HSV-1 recognition by PRRs and innate IFN-mediated antiviral immunity during HSV-1 infection of the cornea. We also discuss the immunopathogenesis of HSK, current HSK therapeutics and challenges, proposed experimental approaches, and benefits of promoting local IFN-λ responses.

Association of scrub typhus with incidence of dementia: a nationwide population-based cohort study in Korea

BACKGROUND

Scrub typhus is a mite-borne infectious rickettsial disease that can occur in rural and urban areas, with an especially high prevalence in older populations. This disease causes systemic vasculitis that can invade the central nervous system. Considering these characteristics, here we examined whether scrub typhus was associated with the occurrence of dementia, using large population-based cohort data.

METHOD

This population-based cohort study enrolled patients aged 60-89 years using data from the Health Insurance Review and Assessment database of South Korea between 2009 and 2018. We defined scrub typhus and dementia using International Classification of Diseases, Tenth Edition diagnostic codes. The control group was stratified according to age and sex at a ratio of 1:5 to the case group in the study population. The index date was set after 90 days beyond the date of the scrub typhus diagnosis, while the observation period was from the time of the index appointment to December 31, 2020. The primary outcome was newly diagnosed dementia. The secondary outcome was dementia classification, such as Alzheimer's disease, vascular dementia, and other. All analyses were conducted by matching age, gender, and comorbidity.

RESULTS

During the observation period, 10,460 of 71,047 (14.7%) people who had a history of scrub typhus versus 42,965 of 355,235 (12.1%) people in the control group, that is, with no history of scrub typhus, were diagnosed with dementia (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.15, p < 0.001). The Kaplan-Meier curves for time to cumulative incidence of dementia showed that the dementia incidence in both groups increased over time, while individuals with a past history of scrub typhus had a higher incidence of dementia than the control group. Second, the risk of Alzheimer's disease was significantly higher among patients with a history of scrub typhus (adjusted hazard ratio, 1.15; 95% confidence interval 1.13-1.18, p < 0.001).

CONCLUSION

In conclusion, a history of scrub typhus infection in old age is significantly associated with an increase in dementia, especially Alzheimer's disease. Our results suggest that prevention and appropriate treatment of scrub typhus should be emphasized as a dementia prevention measure.

Unlocking Modifiable Risk Factors for Alzheimer's Disease: Does the Oral Microbiome Hold Some of the Keys?

Advancing age is recognized as the primary risk factor for Alzheimer's disease (AD); however approximately one third of dementia cases are attributable to modifiable risk factors such as hypertension, diabetes, smoking, and obesity. Recent research also implicates oral health and the oral microbiome in AD risk and pathophysiology. The oral microbiome contributes to the cerebrovascular and neurodegenerative pathology of AD via the inflammatory, vascular, neurotoxic, and oxidative stress pathways of known modifiable risk factors. This review proposes a conceptual framework that integrates the emerging evidence regarding the oral microbiome with established modifiable risk factors. There are numerous mechanisms by which the oral microbiome may interact with AD pathophysiology. Microbiota have immunomodulatory functions, including the activation of systemic pro-inflammatory cytokines. This inflammation can affect the integrity of the blood-brain barrier, which in turn modulates translocation of bacteria and their metabolites to brain parenchyma. Amyloid-β is an antimicrobial peptide, a feature which may in part explain its accumulation. There are microbial interactions with cardiovascular health, glucose tolerance, physical activity, and sleep, suggesting that these modifiable lifestyle risk factors of dementia may have microbial contributors. There is mounting evidence to suggest the relevance of oral health practices and the microbiome to AD. The conceptual framework presented here additionally demonstrates the potential for the oral microbiome to comprise a mechanistic intermediary between some lifestyle risk factors and AD pathophysiology. Future clinical studies may identify specific oral microbial targets and the optimum oral health practices to reduce dementia risk.

Intermittent systemic exposure to lipopolysaccharide-induced inflammation disrupts hippocampal long-term potentiation and impairs cognition in aging male mice

Age-related cognitive decline, a common component of the brain aging process, is associated with significant impairment in daily functioning and quality of life among geriatric adults. While the complexity of mechanisms underlying cognitive aging are still being elucidated, microbial exposure and the multifactorial inflammatory cascades associated with systemic infections are emerging as potential drivers of neurological senescence. The negative cognitive and neurobiological consequences of a single pathogen-associated inflammatory experience, such as that modeled through treatment with lipopolysaccharide (LPS), are well documented. Yet, the brain aging impacts of repeated, intermittent inflammatory challenges are less well studied. To extend the emerging literature assessing the impact of infection burden on cognitive function among normally aging mice, here, we repeatedly exposed adult mice to intermittent LPS challenges during the aging period. Male 10-month-old C57BL6 mice were systemically administered escalating doses of LPS once every two weeks for 2.5 months. We evaluated cognitive consequences using the non-spatial step-through inhibitory avoidance task, and both spatial working and reference memory versions of the Morris water maze. We also probed several potential mechanisms, including cortical and hippocampal cytokine/chemokine gene expression, as well as hippocampal neuronal function via extracellular field potential recordings. Though there was limited evidence for an ongoing inflammatory state in cortex and hippocampus, we observed impaired learning and memory and a disruption of hippocampal long-term potentiation. These data suggest that a history of intermittent exposure to LPS-induced inflammation is associated with subtle but significantly impaired cognition among normally aging mice. The broader impact of these findings may have important implications for standard of care involving infections in aging individuals or populations at-risk for dementia.

Re-Addressing Dementia by Network Medicine and Mechanism-Based Molecular Endotypes

Alzheimer's disease (AD) and other forms of dementia are together a leading cause of disability and death in the aging global population, imposing a high personal, societal, and economic burden. They are also among the most prominent examples of failed drug developments. Indeed, after more than 40 AD trials of anti-amyloid interventions, reduction of amyloid-β (Aβ) has never translated into clinically relevant benefits, and in several cases yielded harm. The fundamental problem is the century-old, brain-centric phenotype-based definitions of diseases that ignore causal mechanisms and comorbidities. In this hypothesis article, we discuss how such current outdated nosology of dementia is a key roadblock to precision medicine and articulate how Network Medicine enables the substitution of clinicopathologic phenotypes with molecular endotypes and propose a new framework to achieve precision and curative medicine for patients with neurodegenerative disorders.

The Neuropathological Impacts of COVID-19: Challenges and Alternative Treatment Options for Alzheimer's Like Brain Changes on Severely SARS-CoV-2 Infected Patients

Recently, some researchers claimed neuropathological changes lead to Alzheimer's-like brains after severe infection of SARS-CoV-2. Several mechanisms have been postulated on how SARS-CoV-2 neurological damage leads to Alzheimer's disease (AD) development. Neurobiochemical changes during infection may significantly induce Alzheimer's disease in severely COVID-19 infected people. The immune system is also compromised while infected by this novel coronavirus. However, recent studies are insufficient to conclude the relationship between Alzheimer's disease and COVID-19. This review demonstrates the possible pathways of neuropathological changes induced by the SARS-CoV-2 virus in AD patients or leading to AD in COVID-19 patients. Therefore, this study delineates the challenges for COVID-19 infected AD patients and the mechanism of actions of natural compounds and alternative treatments to overcome those. Furthermore, animal studies and a large cohort of COVID-19 survivors who showed neuroinflammation and neurological changes may augment the research to discover the relationship between Alzheimer's disease and COVID-19.

Expression of the human herpesvirus 6A latency-associated transcript U94A impairs cytoskeletal functions in human neural cells

Many neurodegenerative diseases have a multifactorial etiology and variable course of progression that cannot be explained by current models. Neurotropic viruses have long been suggested to play a role in these diseases, although their exact contributions remain unclear. Human herpesvirus 6A (HHV-6A) is one of the most common viruses detected in the adult brain, and has been clinically associated with multiple sclerosis (MS), and, more recently, Alzheimer's disease (AD). HHV-6A is a ubiquitous viral pathogen capable of infecting glia and neurons. Primary infection in childhood is followed by the induction of latency, characterized by expression of the U94A viral transcript in the absence of viral replication. Here we examine the effects of U94A on cells of the central nervous system. We found that U94A expression inhibits the migration and impairs cytoplasmic maturation of human oligodendrocyte precursor cells (OPCs) without affecting their viability, a phenotype that may contribute to the failure of remyelination seen in many patients with MS. A subsequent proteomics analysis of U94A expression OPCs revealed altered expression of genes involved in tubulin associated cytoskeletal regulation. As HHV-6A seems to significantly be associated with early AD pathology, we extended our initially analysis of the impact of U94A on human derived neurons. We found that U94A expression inhibits neurite outgrowth of primary human cortical neurons and impairs synapse maturation. Based on these data we suggest that U94A expression by latent HHV-6A in glial cells and neurons renders them susceptible to dysfunction and degeneration. Therefore, latent viral infections of the brain represent a unique pathological risk factor that may contribute to disease processes.

Selective Vulnerability of the Locus Coeruleus Noradrenergic System and its Role in Modulation of Neuroinflammation, Cognition, and Neurodegeneration

Locus coeruleus (LC) noradrenergic (NE) neurons supply the main adrenergic input to the forebrain. NE is a dual modulator of cognition and neuroinflammation. NE neurons of the LC are particularly vulnerable to degeneration both with normal aging and in neurodegenerative disorders. Consequences of this vulnerability can be observed in both cognitive impairment and dysregulation of neuroinflammation. LC NE neurons are pacemaker neurons that are active during waking and arousal and are responsive to stressors in the environment. Chronic overactivation is thought to be a major contributor to the vulnerability of these neurons. Here we review what is known about the mechanisms underlying this neuronal vulnerability and combinations of environmental and genetic factors that contribute to confer risk to these important brainstem neuromodulatory and immunomodulatory neurons. Finally, we discuss proposed and potential interventions that may reduce the overall risk for LC NE neuronal degeneration.

Increased incidence of dementia following herpesvirus infection in the Korean population

Herpesviruses affect the development of dementia. We investigated the association between herpes infection and subsequent diagnoses of dementia. Data from the National Health Insurance Service of South Korea were used. Patients aged ≥50 years with the relevant diagnostic codes in the reference year 2009 were included and prospectively reviewed from January 2010 to December 2018. All study participants were followed from the index date until the onset of dementia, death, or the study endpoint. The three cohorts comprised 92,095 patients with herpes simplex virus (HSV) infections, 97,323 patients with varicella-zoster virus (VZV) infections, and 183,779 controls. During the follow-up period, 15,831 (17.19%) subjects with HSV infection and 17,082 (17.55%) VZV-infected subjects, compared to 27,028 (14.17%) control subjects, were subsequently diagnosed with dementia (all, P < .001). The adjusted hazard ratio for developing dementia was found to be 1.18 (95% confidence interval [CI]; 1.16-1.20) in HSV and 1.09 (95% CI; 1.07-1.11) in VZV patients (all, P < .001). HSV1 infections such as oral or ocular subtypes, but not HSV2, anogenital subtype, were associated with dementia, including several subtypes such as Alzheimer's disease (AD), vascular dementia, and dementia with Lewy bodies. VZV infection is also associated with AD. In this Korean nationwide population-based cohort study, both HSV and VZV infections were associated with a higher risk of dementia, particularly AD. Among the subtypes of HSV infection, HSV1 is associated with a risk of dementia. Further studies including appropriate public health interventions could evaluate the causality of these relationships.

Cross protective efficacy of the Non-Neurotropic live attenuated herpes simplex virus type 1 vaccine VC-2 is enhanced by intradermal vaccination and deletion of glycoprotein G

Herpes simplex virus type 1 and 2 (HSV-1 and HSV-2 respectively) cause life-long latent infections resulting in recurrent orofacial and genital blisters or sores. Ensued disease can be painful and may lead to significant mental anguish of infected individuals. Currently, there are no FDA-approved vaccines for either prophylactic or therapeutic use, and recent clinical trials of subunit vaccines failed to achieve endpoints goals. Development of a safe live-attenuated herpes simplex vaccine may provide the antigenic breadth to ultimately protect individuals from acquiring HSV disease. We have previously shown that prophylactic use of the non-neurotropic live attenuated HSV-1 vaccine, VC-2, provides potent and durable protection from genital HSV-2 disease in the guinea pig model. Here, we investigated the effects of intradermal administration as well as the deletion of the viral glycoprotein G (gG) on the efficacy of prophylactic vaccination. Vaccination with either VC-2, VC-2 gG null, or gD2 MPL/Alum offered robust protection from acute disease regardless of route of vaccination. However, both the VC-2 gG-null and the ID vaccination route were more effective compared to the parent VC2 administered by the IM route. Specifically, the VC-2 gG-null administered ID, reduced HSV-2 vaginal replication on day 2 and day 4 as well as mean recurrent lesion scores more effectively than VC2 administered IM. Most importantly, only VC-2 gG null IM and VC-2 ID significantly reduced the frequency of recurrent shedding, the most likely source for virus transmission. Similarly, while all vaccinated groups demonstrated a significant reduction in the number of animals testing PCR-positive for HSV-2 in their dorsal root ganglia following challenge only VC2 ID vaccinated animals demonstrated a significant reduction in DRG viral load. All vaccinations induced neutralizing antibodies to HSV-2 MS when compared to unvaccinated guinea pigs. Therefore, further investigation of VC-2 gG null delivered ID is warranted.

Implications of Microorganisms in Alzheimer's Disease

Alzheimer’s disease (AD) is a deadly brain degenerative disorder that leads to brain shrinkage and dementia. AD is manifested with hyperphosphorylated tau protein levels and amyloid beta (Aβ) peptide buildup in the hippocampus and cortex regions of the brain. The nervous tissue of AD patients also contains fungal proteins and DNA which are linked to bacterial infections, suggesting that polymicrobial infections also occur in the brains of those with AD. Both immunohistochemistry and next-generation sequencing (NGS) techniques were employed to assess fungal and bacterial infections in the brain tissue of AD patients and non-AD controls, with the most prevalent fungus genera detected in AD patients being Alternaria, Botrytis, Candida, and Malassezia. Interestingly, Fusarium was the most common genus detected in the control group. Both AD patients and controls were also detectable for Proteobacteria, followed by Firmicutes, Actinobacteria, and Bacteroides for bacterial infection. At the family level, Burkholderiaceae and Staphylococcaceae exhibited higher levels in the brains of those with AD than the brains of the control group. Accordingly, there is thought to be a viscous cycle of uncontrolled neuroinflammation and neurodegeneration in the brain, caused by agents such as the herpes simplex virus type 1 (HSV1), Chlamydophilapneumonia, and Spirochetes, and the presence of apolipoprotein E4 (APOE4), which is associated with an increased proinflammatory response in the immune system. Systemic proinflammatory cytokines are produced by microorganisms such as Cytomegalovirus, Helicobacter pylori, and those related to periodontal infections. These can then cross the blood–brain barrier (BBB) and lead to the onset of dementia. Here, we reviewed the relationship between the etiology of AD and microorganisms (such as bacterial pathogens, Herpesviridae viruses, and periodontal pathogens) according to the evidence available to understand the pathogenesis of AD. These findings might guide a targeted anti-inflammatory therapeutic approach to AD.

Efficacy of antimicrobial photodynamic therapy versus antiviral therapy in the treatment of herpetic gingivostomatitis among children: Aa randomized controlled clinical trial

AIM

The aim of the present study was to evaluate the effect of antimicrobial photodynamic therapy (aPDT) as an adjunctive treatment to topical antiviral therapy for the treatment of children having herpetic gingivostomatitis.

MATERIALS AND METHODS

45 individuals (age group 12-18 years) with herpetic gingivostomatitis (HG) were divided into three groups on the basis of provision of treatment. (a) Group A: topical anti-viral therapy (TAT) (n = 14, mean age = 17.0 years) (b) Group B: antimicrobial photodynamic therapy (aPDT) (n = 15, mean age =17.7 years) and (c) Group C: topical anti-viral therapy + adjunctive aPDT (n = 16, mean age = 18.0 years) respectively. Pain scores [visual analogue scale (VAS) and McGill Pain Questionnaire (MPQ)] were assessed and HSV-1 was quantified. ENZYME LINKED IMMUNOSORBENT ASSAY (ELISA) was used to compute the pro-inflammatory cytokine including interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-α). The analysis of the mean values and inter group comparisons were evaluated with the Mann-Whitney test. The Friedman test was used to establish the comparison of the changes observed in HSV quantification, pain scores, and pro-inflammatory cytokines. ANOVA tests were employed for the quantification of differences observed at follow-ups. The assessments for the clinical trial were done at baseline, immediate after post-op, two, and four weeks, and three and six months respectively.

RESULTS

According to the analysis of the data obtained after the clinical assessment, the three groups reported a decrease in the pain scores, HSV-1 quantification and levels of the pro-inflammatory cytokines. However, Group C (TAT + aPDT) reported improvement in the observed parameters which was statistically significant in comparison to Group A (TAT) and Group B (aPDT) respectively.

CONCLUSION

Antimicrobial photodynamic therapy (aPDT) in conjunction with topical antiviral therapy (TAT) helped in reducing the pain scores and pro-inflammatory cytokine levels in herpetic gingivostomatitis among children.

Understanding global changes of the mouse brain proteome after vaginal infection with HSV-2 using a label-free shotgun approach

Herpes simplex virus type 2 (HSV-2) is a common human pathogen that establishes lifelong latency in neurons of the nervous system. The number of severe central nervous system infections caused by the virus has increased recently. However, the pathogenesis of HSV-2 infection in the nervous system is not fully understood. Here, we demonstrated global proteomic changes in the brain tissue in BALB/c mice vaginally infected with HSV-2. Data are available via ProteomeXchange with identifier PXD034186. A total of 249 differentially expressed proteins were identified in infected brain tissue. The GO and KEGG enrichment analysis of these proteins indicated that they were mainly involved in the regulation of synapse formation and synaptic excitability. In addition, genes affecting autophagy, the development of other neurodegenerative diseases, and signaling pathways relevant to other neurologic diseases were identified. Additional experiments, comparing the brain tissue of asymptomatic and symptomatic mice showed a differential expression of proteins involved in synapse formation and synaptic transmission. Others were involved in autophagy, addiction, and signaling pathways of other neurologic diseases. These results suggest that changes in synaptic structure and function, as well as autophagy, may be related to the development of neurologic abnormalities that follow HSV-2 infection. We also identified a protein GluN2A encoded by Grin2a was continuously expressed at high levels after infection. We propose that GluN2A may be a key molecule in the pathogenesis of HSV-2-induced neurologic diseases.

Human Palatine Tonsils Are Linked to Alzheimer’s Disease through Function of Reservoir of Amyloid Beta Protein Associated with Bacterial Infection

Amyloid-β (Aβ)-peptide production or deposition in the neuropathology of Alzheimer’s disease (AD) was shown to be caused by chronic inflammation that may be induced by infection, but the role of pathogenic-bacteria-related AD-associated Aβ is not yet clearly understood. In this study, we validated the hypothesis that there is a correlation between the Aβ-protein load and bacterial infection and that there are effects of bacteria, Staphylococcus aureus (S. aureus), on the Aβ load in the inflammatory environment of human tonsils. Here, we detected Aβ-peptide deposits in human tonsil tissue as well as tissue similar to tonsilloliths found in the olfactory cleft. Interestingly, we demonstrated for the first time the presence of Staphylococcus aureus (S. aureus) clustered around or embedded in the Aβ deposits. Notably, we showed that treatment with S. aureus upregulated the Aβ-protein load in cultures of human tonsil organoids and brain organoids, showing the new role of S. aureus in Aβ-protein aggregation. These findings suggest that a reservoir of Aβ and pathogenic bacteria may be a possible therapeutic target in human tonsils, supporting the treatment of antibiotics to prevent the deposition of Aβ peptides via the removal of pathogens in the intervention of AD pathogenesis.

Immune Response at the Crossroads of Atherosclerosis and Alzheimer's Disease

Alzheimer's disease (AD) and cardiovascular disease (CVD) are pathologies that are characterized by common signatures of vascular dysfunction and chronic inflammation that are accelerated with aging. Importantly, epidemiological studies report an independent interaction between AD and CVD and data suggest that chronic inflammation in CVD may accelerate AD development. Atherosclerosis affects most large to medium sized arteries including those supplying the cerebral circulation. Vascular dysfunction caused by atherosclerosis results in blood brain barrier breakdown, inflammation, an impaired clearance of amyloid-beta (Aβ), and finally ends with neurovascular dysfunction. Numerous data indicate that innate and adaptive immune responses shape atherogenesis and increasing evidence suggests an implication of the immune response in AD progression. Currently, mechanisms by which these two diseases are interconnected with each other are not well-defined. In this review, we discuss the recent advances in our understanding of the intertwined role of the immune response in atherosclerosis and AD and the implications of these findings for human health.

Structural Mimicry in Microbial and Antimicrobial Amyloids

The remarkable variety of microbial species of human pathogens and microbiomes generates significant quantities of secreted amyloids, which are structured protein fibrils that serve diverse functions related to virulence and interactions with the host. Human amyloids are associated largely with fatal neurodegenerative and systemic aggregation diseases, and current research has put forward the hypothesis that the interspecies amyloid interactome has physiological and pathological significance. Moreover, functional and molecular-level connections between antimicrobial activity and amyloid structures suggest a neuroimmune role for amyloids that are otherwise known to be pathological. Compared to the extensive structural information that has been accumulated for human amyloids, high-resolution structures of microbial and antimicrobial amyloids are only emerging. These recent structures reveal both similarities and surprising departures from the typical amyloid motif, in accordance with their diverse activities, and advance the discovery of novel antivirulence and antimicrobial agents. In addition, the structural information has led researchers to postulate that amyloidogenic sequences are natural targets for structural mimicry, for instance in host-microbe interactions. Microbial amyloid research could ultimately be used to fight aggressive infections and possibly processes leading to autoimmune and neurodegenerative diseases.

Screening neuroprotective compounds in herpes-induced Alzheimer's disease cell and 3D tissue models

Alzheimer's Disease (AD) is a neurodegenerative disorder that can cause life-altering and debilitating cognitive decline. AD's etiology is poorly understood, and no disease-modifying therapeutics exist. Here, we describe the use of 2D and 3D tissue culture models of herpesvirus-induced AD, which recapitulate hallmark disease features of plaque formation, gliosis, neuroinflammation, and impaired neuronal signaling, to screen a panel of 21 medications, supplements, and nutraceuticals with purported neuroprotective benefits. This screen identified green tea catechins and resveratrol as having strong anti-plaque properties, functional neuroprotective benefits, and minimal neurotoxicity, providing support for their further investigation as AD preventives and therapies. Two other candidates, citicoline and metformin, reduced plaque formation and were minimally toxic, but did not protect against virus-induced impairments in neuronal signaling. This study establishes a simple platform for rapidly screening and characterizing AD compounds of interest in 2D and 3D human cortical tissue models representing physiologically relevant disease features.

Does Dementia Have a Microbial Cause?

The potential contribution of pathogenic microbes to dementia-inducing disease is a subject of considerable importance. Alzheimer's disease (AD) is a neurocognitive disease that slowly destroys brain function, leading to cognitive decline and behavioral and psychiatric disorders. The histopathology of AD is associated with neuronal loss and progressive synaptic dysfunction, accompanied by the deposition of amyloid-β (Aβ) peptide in the form of parenchymal plaques and abnormal aggregated tau protein in the form of neurofibrillary tangles. Observational, epidemiological, experimental, and pathological studies have generated evidence for the complexity and possible polymicrobial causality in dementia-inducing diseases. The AD pathogen hypothesis states that pathogens and microbes act as triggers, interacting with genetic factors to initiate the accumulation of Aβ, hyperphosphorylated tau protein (p-tau), and inflammation in the brain. Evidence indicates that Borrelia sp., HSV-1, VZV (HHV-2), HHV-6/7, oral pathogens, Chlamydophila pneumoniae, and Candida albicans can infect the central nervous system (CNS), evade the immune system, and consequently prevail in the AD brain. Researchers have made significant progress in understanding the multifactorial and overlapping factors that are thought to take part in the etiopathogenesis of dementia; however, the cause of AD remains unclear.

Cerebral Organoids for Modeling of HSV-1-Induced-Amyloid β Associated Neuropathology and Phenotypic Rescue

Herpes simplex virus type I (HSV-1) infection is a potential risk factor involved in the Amyloid β (Aβ) associated neuropathology. However, further understanding of the neuropathological effects of the HSV-1 infection is hampered by the limitations of existing infection models due to the distinct differences between human brains and other mammalians’ brains. Here we generated cerebral organoid models derived from pluripotent stem cells to investigate the HSV-induced Aβ associated neuropathology and the role of antiviral drugs in the phenotypic rescue. Our results identified that the HSV-1-infected cerebral organoids recapitulated Aβ associated neuropathology including the multicellular Aβ deposition, dysregulated endogenous AD mediators, reactive gliosis, neuroinflammation, and neural loss, indicating that cerebral organoids offer an opportunity for modeling the interaction of HSV-1 with the complex phenotypes across the genetic, cellular, and tissue levels of the human Alzheimer’s disease (AD). Furthermore, we identified that two antiviral drugs, namely Ribavirin (RBV) and Valacyclovir (VCV), inhibited HSV-1 replication and rescued the neuropathological phenotypes associated with AD in the HSV-1-infected cerebral organoids, implying their therapeutic potential to slow down the progression of AD. Our study provides a high-fidelity human-relevant in-vitro HSV-1 infection model to reconstitute the multiscale neuropathological features associated with AD and discover therapeutic drug candidates relevant to the AD viral hypothesis.

Effect of Cytomegalovirus Infection on the Central Nervous System: Implications for Psychiatric Disorders

Cytomegalovirus (CMV) is a common herpesvirus that establishes lifelong latent infections and interacts extensively with the host immune system, potentially contributing to immune activation and inflammation. Given its proclivity for infecting the brain and its reactivation by inflammatory stimuli, CMV is well known for causing central nervous system complications in the immune-naïve (e.g., in utero) and in the immunocompromised (e.g., in neonates, individuals receiving transplants or cancer chemotherapy, or people living with HIV). However, its potentially pathogenic role in diseases that are characterized by more subtle immune dysregulation and inflammation such as psychiatric disorders is still a matter of debate. In this chapter, we briefly summarize the pathogenic role of CMV in immune-naïve and immunocompromised populations and then review the evidence (i.e., epidemiological studies, serological studies, postmortem studies, and recent neuroimaging studies) for a link between CMV infection and psychiatric disorders with a focus on mood disorders and schizophrenia. Finally, we discuss the potential mechanisms through which CMV may cause CNS dysfunction in the context of mental disorders and conclude with a summary of the current state of play as well as potential future research directions in this area.

The Possible Role of Prion-Like Viral Protein Domains on the Emergence of Novel Viruses as SARS-CoV-2

Self-replicating proteins or prions deviate from the central dogma of replication. The discovery of prion-like domains in coronavirus SARS-CoV-2 suggests their possible role in viral evolution. Here, we have outlined the possible role of self-replicating protein-like domains in the emergence of novel viruses. Further studies are needed to understand the function of these viral self-replicating protein-like domains and whether they could be antiviral target(s) for the development of effective antiviral agents in the future.

Sequence complementarity between human noncoding RNAs and SARS-CoV-2 genes: What are the implications for human health?

Objectives

To investigate in silico the presence of nucleotide sequence complementarity between the RNA genome of Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2) and human non-coding (nc)RNA genes.

Methods

The FASTA sequence (NC_045512.2) of each of the 11 SARS-CoV-2 isolate Wuhan-Hu-1 genes was retrieved from NCBI.nlm.nih.gov/gene and the Ensembl.org library interrogated for any base-pair match with human ncRNA genes. SARS-CoV-2 gene-matched human ncRNAs were screened for functional activity using bioinformatic analysis. Finally, associations between identified ncRNAs and human diseases were searched in GWAS databases.

Results

A total of 252 matches were found between the nucleotide sequence of SARS-CoV-2 genes and human ncRNAs. With the exception of two small nuclear RNAs, all of them were long non-coding (lnc)RNAs expressed mainly in testis and central nervous system under physiological conditions. The percentage of alignment ranged from 91.30% to 100% with a mean nucleotide alignment length of 17.5 ± 2.4. Thirty-three (13.09%) of them contained predicted R-loop forming sequences, but none of these intersected the complementary sequences of SARS-CoV-2. However, in 31 cases matches fell on ncRNA regulatory sites, whose adjacent coding genes are mostly involved in cancer, immunological and neurological pathways. Similarly, several polymorphic variants of detected non-coding genes have been associated with neuropsychiatric and proliferative disorders.

Conclusion

This pivotal in silico study shows that SARS-CoV-2 genes have Watson-Crick nucleotide complementarity to human ncRNA sequences, potentially disrupting ncRNA epigenetic control of target genes. It remains to be elucidated whether this could result in the development of human disease in the long term.

The evolution of knowledge on genes associated with human diseases

Thousands of biomedical scientific articles, including those describing genes associated with human diseases, are published every week. Computational methods such as text mining and machine learning algorithms are now able to automatically detect these associations. In this study, we used a cognitive computing text-mining application to construct a knowledge network comprising 3,723 genes and 99 diseases. We then tracked the yearly changes on these networks to analyze how our knowledge has evolved in the past 30 years. Our systems approach helped to unravel the molecular bases of diseases and detect shared mechanisms between clinically distinct diseases. It also revealed that multi-purpose therapeutic drugs target genes that are commonly associated with several psychiatric, inflammatory, or infectious disorders. By navigating this knowledge tsunami, we were able to extract relevant biological information and insights about human diseases.

Cognitive decline following acute viral infections: literature review and projections for post-COVID-19

Recently, much attention has been drawn to the importance of the impact of infectious disease on human cognition. Several theories have been proposed, to explain the cognitive decline following an infection as well as to understand better the pathogenesis of human dementia, especially Alzheimer's disease. This article aims to review the state of the art regarding the knowledge about the impact of acute viral infections on human cognition, laying a foundation to explore the possible cognitive decline followed coronavirus disease 2019 (COVID-19). To reach this goal, we conducted a narrative review systematizing six acute viral infections as well as the current knowledge about COVID-19 and its impact on human cognition. Recent findings suggest probable short- and long-term COVID-19 impacts in cognition, even in asymptomatic individuals, which could be accounted for by direct and indirect pathways to brain dysfunction. Understanding this scenario might help clinicians and health leaders to deal better with a wave of neuropsychiatric issues that may arise following COVID-19 pandemic as well as with other acute viral infections, to alleviate the cognitive sequelae of these infections around the world.