Targeted RNA Sequencing of VZV-Infected Brain Vascular Adventitial Fibroblasts Indicates That Amyloid May Be Involved in VZV Vasculopathy

The effect of herpes zoster vaccination at different stages of the disease course of dementia: Two quasi-randomized studies

The varicella zoster virus, a neurotropic herpesvirus, has been hypothesized to play a role in the pathophysiology of dementia, such as through neuroinflammatory processes or intracerebral vasculopathy. Using unique natural experiments, our group has previously found that live-attenuated herpes zoster (HZ) vaccination reduced the incidence of new diagnoses of dementia in both Wales and Australia. To inform further research and ultimately clinical care, it is crucial to understand at which stage of the disease course of dementia the HZ vaccine has its effect. Representing the two opposing ends of the dementia disease course as it can be ascertained from electronic health record data, the aims of this study were twofold: to determine the effect of HZ vaccination on i) new diagnoses of mild cognitive impairment (MCI) among individuals without any record of cognitive impairment, and ii) deaths due to dementia among individuals living with dementia. Our approach took advantage of the fact that at the time of the start date (September 1 2013) of the HZ vaccination program in Wales, individuals who had their eightieth birthday just after this date were eligible for HZ vaccination for one year whereas those who had their eightieth birthday just before were ineligible and remained ineligible for life. This eligibility rule created comparison groups just on either side of the September 2 1933 date-of-birth eligibility threshold who differed in their age by merely a week but had a large difference in their probability of receiving HZ vaccination. The key strength of our study is that these comparison groups should be similar in their health characteristics and behaviors except for a minute difference in age. We used regression discontinuity analysis to estimate the difference in our outcomes between individuals born just on either side of the date-of-birth eligibility threshold for HZ vaccination. Our dataset consisted of detailed country-wide electronic health record data from primary care in Wales, linked to hospital records and death certificates. We restricted our dataset to individuals born between September 1 1925 and September 1 1942. Among our study cohort of 282,557 without any record of cognitive impairment at baseline, HZ vaccination eligibility and receipt reduced the incidence of a new MCI diagnosis by 1.5 (95% CI: 0.5 - 2.9, p=0.006) and 3.1 (95% CI: 1.0 - 6.2, p=0.007) percentage points over nine years, respectively. Similarly, among our study cohort of 14,350 individuals who were living with dementia at baseline, being eligible for and receiving HZ vaccination reduced deaths due to dementia by 8.5 (95% CI: 0.6 - 18.5, p=0.036) and 29.5 (95% CI: 0.6 - 62.9, p=0.046) percentage points over nine years, respectively. Except for dementia, HZ vaccination did not have an effect on any of the ten most common causes of morbidity and mortality among adults aged 70 years and older in Wales in either of our two study cohorts. The protective effects of HZ vaccination for both MCI and deaths due to dementia were larger among women than men. Our findings suggest that the live-attenuated HZ vaccine has benefits for the dementia disease process at both ends of the disease course of dementia.

Herpes zoster vaccination and new diagnoses of dementia: A quasi-randomized study in Australia

Increasing evidence suggests that neurotropic herpesviruses could play a role in the development of dementia, possibly through a neuroinflammatory process. Herpes zoster (HZ) vaccination has been reported to lead to a reduced probability of being diagnosed with dementia in several correlational studies and in a prior analysis by our team in Wales. This present study constitutes the first investigation to use a quasi-randomized study design in an electronic health record dataset from a large and diverse nation (Australia) to aim to determine the effect of HZ vaccination on dementia. In Australia, starting on November 1 2016, live-attenuated HZ vaccination was provided for free to individuals aged 70 to 79 years of age through primary care providers. Thus, those whose 80th birthday was just a few days prior to November 1 2016 never became eligible, whereas those whose 80th birthday was just a few days later were eligible. The key advantage of our approach is that one would not expect that these population groups who differ in their age by only a minute degree would, on average, differ in any of their health characteristics and behaviors. We used detailed primary healthcare records with week-of-birth information from 65 general practices across Australia. We analyzed our data using a regression discontinuity approach. Our sample consisted of 101,219 patients. As expected, patients born just before versus shortly after the date-of-birth eligibility threshold (November 2 1936) for HZ vaccination were well-balanced in their past preventive health services uptake and chronic disease diagnoses. There was an abrupt increase of 15.7 (95% CI: [12.2 - 19.3], p < 0.001) percentage points in the probability of ever receiving HZ vaccination between patients born shortly before versus shortly after the eligibility threshold. The eligibility rules of the HZ vaccination program, thus, created comparison groups just on either side of the date-of-birth eligibility threshold who were similar to each other, except for a large difference in their probability of receiving the intervention (HZ vaccination) of interest. Eligibility for HZ vaccination (i.e., being born shortly before versus shortly after November 2 1936) decreased the probability of receiving a new dementia diagnosis over 7.4 years by 2.0 percentage points (95% CI: [0.3 - 3.7], p = 0.021). Being eligible for HZ vaccination did not affect the probability of taking up other preventive health services (including other vaccinations), nor the probability of being diagnosed with other common chronic conditions than dementia. This study provides important evidence on the potential benefits of HZ vaccination for dementia because its quasi-randomized design allows for conclusions that are more likely to be causal than those of the existing associational evidence.

Infectious and Postinfectious Vasculopathies

Stroke is a complication of many central nervous system (CNS) infections, but only a few present with stroke without other symptoms or signs of CNS infection. Chief among these are varicella zoster virus (VZV) and syphilis. Delayed cerebral vasculopathy after successful treatment of bacterial meningitis, most commonly pneumococcal, is an emerging entity with uncertain pathogenesis.

The association between varicella zoster virus and dementia: a systematic review and meta-analysis of observational studies

PURPOSE

The relationship between varicella zoster virus (VZV) infection and the risk of dementia has not been previously studied specifically. Therefore, this study sought to determine the relationship between studying VZV infection and dementia occurring in the general population by conducting an extensive meta-analysis of published cases.

METHOD

A systematic literature search was conducted in seven online databases by October 31, 2022. Heterogeneity was tested by the I2 index. Pooled HR and 95% CI were used to estimate the effect of VZV infection on dementia. Sensitivity analyses and publication bias were also performed.

RESULT

Nine studies involving 3,326,673 subjects were included. VZV infection was associated with an increased risk of dementia (HR = 1.11, 95% CI: 1.02-1.21). The risk of dementia was reduced in those who received antiviral therapy compared to those who did not (HR = 0.84, 95% CI: 0.71-0.99). In addition, VZV infection was found to be associated with an increased risk of developing dementia in the pooled results of the moderate quality study (HR = 1.81,95% CI: 1.27-2.59), and this association persisted when subgroup analyses were performed based on region (Asia: HR = 1.18,95% CI: 1.04-1.33).

CONCLUSIONS

Our results suggest that VZV infection might increase the risk of developing dementia, but there is no clear mechanism about the true relationship, and since there is no effective treatment for dementia, and our results suggest that some populations can benefit from antiviral therapy, it is at least arguable that patients who develop VZV infection should be treated with appropriate antiviral medications.

Resveratrol: a potential medication for the prevention and treatment of varicella zoster virus-induced ischemic stroke

BACKGROUND

Infection rate of varicella zoster virus (VZV) is 95% in humans, and VZV infection is strongly associated with ischemic stroke (IS). However, the underlying molecular mechanisms of VZV-induced IS are still unclear, and there are no effective agents to treat and prevent VZV-induced IS.

OBJECTIVE

By integrating bioinformatics, this study explored the interactions between VZV and IS and potential medication to treat and prevent VZV-induced IS.

METHODS

In this study, the VZV and IS datasets from the GEO database were used to specify the common genes. Then, bioinformatics analysis including Gene Ontology, Kyoto Encyclopedia Genes Genomes and Protein-Protein Interaction network analysis was performed. Further, the hub genes, transcription factor (TF) gene interactions, TF-miRNA co-regulatory network and potential drug were obtained. Finally, validation was performed using molecular docking and molecular dynamics simulations.

RESULTS

The potential molecular mechanisms of VZV-induced IS were studied using multiple bioinformatics tools. Ten hub genes were COL1A2, DCN, PDGFRB, ACTA2, etc. TF genes and miRNAs included JUN, FOS, CREB, BRCA1, PPARG, STAT3, miR-29, etc. A series of mechanism may be involved, such as inflammation, oxidative stress, blood-brain barrier disruption, foam cell generation and among others. Finally, we proposed resveratrol as a potential therapeutic medicine for the prevention and treatment of VZV-induced IS. Molecular docking and molecular dynamics results showed that resveratrol and hub genes exhibited strong binding score.

CONCLUSIONS

Resveratrol could be an alternative for the prevention and treatment of VZV-IS. More in vivo and in vitro studies are needed in the future to fully explore the molecular mechanisms between VZV and IS and for medication development.

Zoster-Associated Prothrombotic Plasma Exosomes and Increased Stroke Risk

Herpes zoster (HZ; shingles) caused by varicella zoster virus reactivation increases stroke risk for up to 1 year after HZ. The underlying mechanisms are unclear, however, the development of stroke distant from the site of zoster (eg, thoracic, lumbar, sacral) that can occur months after resolution of rash points to a long-lasting, virus-induced soluble factor (or factors) that can trigger thrombosis and/or vasculitis. Herein, we investigated the content and contributions of circulating plasma exosomes from HZ and non-HZ patient samples. Compared with non-HZ exosomes, HZ exosomes (1) contained proteins conferring a prothrombotic state to recipient cells and (2) activated platelets leading to the formation of platelet-leukocyte aggregates. Exosomes 3 months after HZ yielded similar results and also triggered cerebrovascular cells to secrete the proinflammatory cytokines, interleukin 6 and 8. These results can potentially change clinical practice through addition of antiplatelet agents for HZ and initiatives to increase HZ vaccine uptake to decrease stroke risk.

Signatures for viral infection and inflammation in the proximal olfactory system in familial Alzheimer's disease

Alzheimer's disease (AD) is characterized by deficits in olfaction and olfactory pathology preceding diagnosis of dementia. Here we analyzed differential gene and protein expression in the olfactory bulb (OB) and tract (OT) of familial AD (FAD) individuals carrying the autosomal dominant presenilin 1 E280A mutation. Compared to control, FAD OT had increased immunostaining for β-amyloid (Aβ) and CD68 in high and low myelinated regions, as well as increased immunostaining for Iba1 in the high myelinated region. In FAD samples, RNA sequencing showed: (1) viral infection in the OB; (2) inflammation in the OT that carries information via entorhinal cortex from the OB to hippocampus, a brain region essential for learning and memory; and (3) decreased oligodendrocyte deconvolved transcripts. Interestingly, spatial proteomic analysis confirmed altered myelination in the OT of FAD individuals, implying dysfunction of communication between the OB and hippocampus. These findings raise the possibility that viral infection and associated inflammation and dysregulation of myelination of the olfactory system may disrupt hippocampal function, contributing to acceleration of FAD progression.

The emerging mechanism behind viral infections and extracellular vesicles hypotheses leading to neuroinflammation and Alzheimer's disease pathology

Despite decades of repeated and intense research, the etiology of sudden Alzheimer's disease (AD) symptoms is still unclear. AD progressive pathology mainly involves neuron damage, depositions of amyloid-beta (Aβ), and hyperphosphorylated tau protein. All these defects are manifested by exaggerated cytokine storm and neuroinflammation leading to irreversible brain damage in the long term. Despite the numerous risks and drawbacks associated with AD, it is believed that there is a hidden unknown causative and predisposing factors for AD. Extracellular vesicles (EVs) are small vesicles released by cells as a type of intercellular communication. Several pieces of evidence support the inclusion of viral components within EVs facilitating their penetration into the blood-brain barrier leading to neuroinflammation. In light of the SARS-CoV-19 pandemic and its related neurological complications, it is mandatory to highlight the possibility and viability of viral infections such as varicella-zoster virus (VZV) and herpes simplex virus (HSV) on the onset of AD. Herein, the author is investigating the potential role of VZV and HSV along with highlighting the suggested route of pathogenesis entry resulting in AD manifestations. Additionally, this review aims to summarize the role of EVs in mediating the central nervous system viral infections leading to AD.

Retinal vasculopathy following varicella zoster virus infection

PURPOSE OF REVIEW

Varicella zoster virus (VZV) ocular infection can manifest purely as a vasculopathy that leads to retinal arteriole occlusion, without any retinitis or vasculitis. This review summarizes our current knowledge of such VZV ocular infection phenotype, incorporating initial descriptions from 1988. We describe the pathogenesis and VZV's manifestations in the retina using fundus photography, fundus fluorescein angiography, optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). Laboratory investigations, diagnostic procedures, prognoses, and treatment options are also being reviewed.

RECENT FINDINGS

Ten case reports where VZV retinal vasculopathy was the primary feature observed after varicella or zoster rash are described. The retinal arteriole, cilioretinal artery, branches of retinal artery, central retinal artery and ophthalmic artery were found to be areas of more rarely affected, neither in the form of vasculitis nor retinitis. Diagnosis is typically made from positive polymerase chain reaction (PCR) for VZV from extracted intraocular fluid or positive serum or cerebrospinal fluid (CSF) anti-VZV immunoglobulin G antibody in the context of compatible ocular findings. In addition, retinal vasculopathy occurring in the setting of confirmed varicella or zoster rashes could be considered potentially pathognomonic. Pathological concepts, including direct VZV infection of affected tissue, persistent inflammation, and/or virus-induced hypercoagulability are also discussed.

SUMMARY

VZV may produce a wide spectrum of ocular manifestations with isolated VZV retinal vasculopathy being a rarer presentation. A prompt diagnosis followed by an early treatment of systemic acyclovir with or without corticosteroids is the mainstay of treatment.

Role of Intracellular Amyloid β as Pathway Modulator, Biomarker, and Therapy Target

The β- and γ-secretase-driven cleavage of the amyloid precursor protein (APP) gives rise to the amyloid β peptide, which is believed to be the main driver of neurodegeneration in Alzheimer’s disease (AD). As it is prominently detectable in extracellular plaques in post-mortem AD brain samples, research in recent decades focused on the pathological role of extracellular amyloid β aggregation, widely neglecting the potential meaning of very early generation of amyloid β inside the cell. In the last few years, the importance of intracellular amyloid β (iAβ) as a strong player in neurodegeneration has been indicated by a rising number of studies. In this review, iAβ is highlighted as a crucial APP cleavage fragment, able to manipulate intracellular pathways and foster neurodegeneration. We demonstrate its relevance as a pathological marker and shed light on initial studies aiming to modulate iAβ through pharmacological treatment, which has been shown to have beneficial effects on cognitive properties in animal models. Finally, we display the relevance of viral infections on iAβ generation and point out future directions urgently needed to manifest the potential relevance of iAβ in Alzheimer’s disease.