Multiscale Analysis of Independent Alzheimer's Cohorts Finds Disruption of Molecular, Genetic, and Clinical Networks by Human Herpesvirus

Investigators have long suspected that pathogenic microbes might contribute to the onset and progression of Alzheimer's disease (AD) although definitive evidence has not been presented. Whether such findings represent a causal contribution, or reflect opportunistic passengers of neurodegeneration, is also difficult to resolve. We constructed multiscale networks of the late-onset AD-associated virome, integrating genomic, transcriptomic, proteomic, and histopathological data across four brain regions from human post-mortem tissue. We observed increased human herpesvirus 6A (HHV-6A) and human herpesvirus 7 (HHV-7) from subjects with AD compared with controls. These results were replicated in two additional, independent and geographically dispersed cohorts. We observed regulatory relationships linking viral abundance and modulators of APP metabolism, including induction of APBB2, APPBP2, BIN1, BACE1, CLU, PICALM, and PSEN1 by HHV-6A. This study elucidates networks linking molecular, clinical, and neuropathological features with viral activity and is consistent with viral activity constituting a general feature of AD.

Herpes simplex virus type 1 in brain and risk of Alzheimer's disease

BACKGROUND

The apolipoprotein E epsilon 4 (APOE-epsilon 4) allele is a risk factor for Alzheimer's disease (AD), but it is neither essential nor sufficient for development of the disease. Other factors-genetic or environmental-must therefore have a role. By means of a PCR we have detected herpes simplex virus type 1 (HSV1) in latent form in brains of elderly people with and without AD. We have postulated that limited reactivation of the virus causes more damage in AD patients than in elderly people without AD because of a difference in the hosts. We now report the APOE genotypes of AD patients and non-AD sufferers with and without HSV1 in brain.

METHODS

DNA was extracted from 84 samples of brain from 46 AD patients (39 temporal lobe, 39 frontal lobe, three hippocampus) and from 75 samples of brain from 44 non-AD elderly people (33 temporal lobe, 36 frontal lobe, six hippocampus). PCR amplification was used to detect HSV1 thymidine kinase gene and the host APOE gene.

FINDINGS

By multiple logistic regression, the APOE-epsilon 4 allele frequency was significantly higher in the patients positive for HSV1 in brain than in the HSV1-negative AD group, the HSV1-positive non-AD group, or the HSV1-negative non-AD group (52.8% vs 10.0%, 3.6%, and 6.3%, respectively). The odds ratio for APOE-epsilon 4 in the HSV1-positive AD group compared with HSV1-negative non-AD group was 16.8 (95% CI 3.61-77.8) and in the HSV1-negative AD group, 1.67 (0.21-13.4). We also compared APOE genotypes of 40 people who had recurrent cold sores and 33 non-sufferers; the APOE-epsilon 4 allele frequencies were 36% and 9%, respectively (p < 0.0001).

INTERPRETATION

These findings suggest that the combination of HSV1 in brain and carriage of an APOE-epsilon 4 allele is a strong risk factor for AD, whereas either of these features alone does not increase the risk of AD. The findings in people with cold sores support our hypothesis that APOE-epsilon 4 and HSV1 together are damaging in the nervous system.

Alzheimer's Disease-Associated β-Amyloid Is Rapidly Seeded by Herpesviridae to Protect against Brain Infection

Amyloid-β peptide (Aβ) fibrilization and deposition as β-amyloid are hallmarks of Alzheimer's disease (AD) pathology. We recently reported Aβ is an innate immune protein that protects against fungal and bacterial infections. Fibrilization pathways mediate Aβ antimicrobial activities. Thus, infection can seed and dramatically accelerate β-amyloid deposition. Here, we show Aβ oligomers bind herpesvirus surface glycoproteins, accelerating β-amyloid deposition and leading to protective viral entrapment activity in 5XFAD mouse and 3D human neural cell culture infection models against neurotropic herpes simplex virus 1 (HSV1) and human herpesvirus 6A and B. Herpesviridae are linked to AD, but it has been unclear how viruses may induce β-amyloidosis in brain. These data support the notion that Aβ might play a protective role in CNS innate immunity, and suggest an AD etiological mechanism in which herpesviridae infection may directly promote Aβ amyloidosis.

Anticipating and Mitigating the Impact of the COVID-19 Pandemic on Alzheimer's Disease and Related Dementias

The COVID-19 pandemic is causing global morbidity and mortality, straining health systems, and disrupting society, putting individuals with Alzheimer's disease and related dementias (ADRD) at risk of significant harm. In this Special Article, we examine the current and expected impact of the pandemic on individuals with ADRD. We discuss and propose mitigation strategies for: the risk of COVID-19 infection and its associated morbidity and mortality for individuals with ADRD; the impact of COVID-19 on the diagnosis and clinical management of ADRD; consequences of societal responses to COVID-19 in different ADRD care settings; the effect of COVID-19 on caregivers and physicians of individuals with ADRD; mental hygiene, trauma, and stigma in the time of COVID-19; and the potential impact of COVID-19 on ADRD research. Amid considerable uncertainty, we may be able to prevent or reduce the harm of the COVID-19 pandemic and its consequences for individuals with ADRD and their caregivers.

The viral protein corona directs viral pathogenesis and amyloid aggregation

Artificial nanoparticles accumulate a protein corona layer in biological fluids, which significantly influences their bioactivity. As nanosized obligate intracellular parasites, viruses share many biophysical properties with artificial nanoparticles in extracellular environments and here we show that respiratory syncytial virus (RSV) and herpes simplex virus type 1 (HSV-1) accumulate a rich and distinctive protein corona in different biological fluids. Moreover, we show that corona pre-coating differentially affects viral infectivity and immune cell activation. In addition, we demonstrate that viruses bind amyloidogenic peptides in their corona and catalyze amyloid formation via surface-assisted heterogeneous nucleation. Importantly, we show that HSV-1 catalyzes the aggregation of the amyloid β-peptide (Aβ42), a major constituent of amyloid plaques in Alzheimer's disease, in vitro and in animal models. Our results highlight the viral protein corona as an acquired structural layer that is critical for viral-host interactions and illustrate a mechanistic convergence between viral and amyloid pathologies.

Herpesviruses in brain and Alzheimer's disease

It has been established, using polymerase chain reaction (PCR), that herpes simplex virus type 1 (HSV1) is present in a high proportion of brains of elderly normal subjects and Alzheimer's disease (AD) patients. It was subsequently discovered that the virus confers a strong risk of AD when in brain of carriers of the type 4 allele of the apolipoprotein E gene (apoE-epsilon4). This study has now sought, using PCR, the presence of three other herpesviruses in brain: human herpesvirus 6 (HHV6)-types A and B, herpes simplex virus type 2 (HSV2) and cytomegalovirus (CMV). HHV6 is present in a much higher proportion of the AD than of age-matched normal brains (70% vs. 40%, p=0.003) and there is extensive overlap with the presence of HSV1 in AD brains, but HHV6, unlike HSV1, is not directly associated in AD with apoE-epsilon4. In 59% of the AD patients' brains harbouring HHV6, type B is present while 38% harbour both type A and type B, and 3% type A. HSV2 is present at relatively low frequency in brains of both AD patients and normals (13% and 20%), and CMV at rather higher frequencies in the two groups (36% and 35%); in neither case is the difference between the groups statistically significant. It is suggested that the striking difference in the proportion of elderly brains harbouring HSV1 and HSV2 might reflect the lower proportion of people infected with the latter, or the difference in susceptibility of the frontotemporal regions to the two viruses. In the case of HHV6, it is not possible to exclude its presence as an opportunist, but alternatively, it might enhance the damage caused by HSV1 and apoE-epsilon4 in AD; in some viral diseases it is associated with characteristic brain lesions and it also augments the damage caused by certain viruses in cell culture and in animals.

The chronic neuropsychiatric sequelae of COVID-19: The need for a prospective study of viral impact on brain functioning

INTRODUCTION

The increasing evidence of SARS-CoV-2 impact on the central nervous system (CNS) raises key questions on its impact for risk of later life cognitive decline, Alzheimer's disease (AD), and other dementia.

METHODS

The Alzheimer's Association and representatives from more than 30 countries-with technical guidance from the World Health Organization-have formed an international consortium to study the short-and long-term consequences of SARS-CoV-2 on the CNS-including the underlying biology that may contribute to AD and other dementias. This consortium will link teams from around the world covering more than 22 million COVID-19 cases to enroll two groups of individuals including people with disease, to be evaluated for follow-up evaluations at 6, 9, and 18 months, and people who are already enrolled in existing international research studies to add additional measures and markers of their underlying biology.

CONCLUSIONS

The increasing evidence and understanding of SARS-CoV-2's impact on the CNS raises key questions on the impact for risk of later life cognitive decline, AD, and other dementia. This program of studies aims to better understand the long-term consequences that may impact the brain, cognition, and functioning-including the underlying biology that may contribute to AD and other dementias.

Infiltration of the brain by pathogens causes Alzheimer's disease

Despite very numerous studies on Alzheimer's disease (AD), especially on amyloid plaques and neurofibrillary tangles, little information has been obtained thus on the causes of the disease. Evidence is described here that implicates firstly herpes simplex virus type 1 (HSV1) as a strong risk factor when it is present in brain of carriers of the type 4 allele of the gene for apolipoprotein E (APOE-4). Indirect support comes from studies indicating the role of APOE in several diverse diseases of known pathogen cause. A second putative risk factor is the bacterium, Chlamydia pneumoniae. This pathogen has been identified and localized in AD brain. Current studies aimed at "proof of principle" address the entry of the organism into the CNS, the neuroinflammatory response to the organism, and the role that the organism plays in triggering AD pathology. An infection-based animal model demonstrates that following intranasal inoculation of BALB/c mice with C. pneumoniae, amyloid plaques/deposits consistent with those observed in the AD brain develop, thus implicating this infection in the etiology of AD.

Productive herpes simplex virus in brain of elderly normal subjects and Alzheimer's disease patients

It was previously shown that herpes simplex virus type 1 (HSV1) DNA resides latently in a high proportion of aged brains and that in carriers of the type 4 allele of the apolipoprotein E gene (APOE-epsilon4), it confers a strong risk of Alzheimer's disease. It was suggested that initial entry of brain by HSV1 and any subsequent reactivation(s) would cause a type of limited encephalitis, the resulting damage being more harmful in APOE-epsilon4 carriers. Reactivation(s) would induce synthesis of intrathecal antibodies; these are long-lived after herpes simplex encephalitis so they were sought in cerebrospinal fluid (CSF) of Alzheimer's disease patients and age-matched normal subjects. Intrathecal antibodies to human herpesvirus 6 (HHV6) were also sought as DNA of this virus has been detected previously in a high proportion of Alzheimer's disease brains. Antibody indices for HSV and HHV6 were measured using indirect ELISA for IgG antibody, and single radial immunodiffusion was used for albumin, in serum and CSF. A raised antibody index (>1.5) indicative of virus-specific intrathecal HSV1 IgG synthesis was found in 14/27 (52%) Alzheimer's disease patients and 9/13 (69%) age-matched normals (difference non-significant). A raised antibody index to HHV6 was detected in 22% of the Alzheimer's disease patients and in no normals, so presumably this virus either did not reactivate in brain or it elicited only short-lived intrathecal antibodies. The HSV1 results confirm the original PCR findings that show the presence of HSV1 DNA sequences in many elderly brains, and indicate also that the whole functional HSV1 genome is present, and that the virus has replicated.

Herpesviruses in brains in Alzheimer's and Parkinson's diseases

We evaluated the association of HSV-1, HHV-6, and VZV with Alzheimer's disease (AD) and Parkinson's disease (PD). Brain specimens for viral DNA polymerase chain reaction represented 34 patients with AD, 40 with PD, and 40 controls. One AD patient (2.9%) was positive for HSV-1 DNA, 88.2% for HHV-6 DNA, and 26.5% for VZV DNA; 17.5% of PD patients were HSV-1 DNA-positive and 75% HHV-6-positive, whereas 40% had VZV DNA. Twenty-five percent of the controls were positive for HSV-1 DNA, 87.5% for HHV-6, and 27.5% for VZV. HSV-1, VZV, or HHV-6 DNA in brains was no additional risk factor for AD.

Human Herpesvirus 6 Detection in Alzheimer's Disease Cases and Controls across Multiple Cohorts

The interplay between viral infection and Alzheimer's disease (AD) has long been an area of interest, but proving causality has been elusive. Several recent studies have renewed the debate concerning the role of herpesviruses, and human herpesvirus 6 (HHV-6) in particular, in AD. We screened for HHV-6 detection across three independent AD brain repositories using (1) RNA sequencing (RNA-seq) datasets and (2) DNA samples extracted from AD and non-AD control brains. The RNA-seq data were screened for pathogens against taxon references from over 25,000 microbes, including 118 human viruses, whereas DNA samples were probed for PCR reactivity to HHV-6A and HHV-6B. HHV-6 demonstrated little specificity to AD brains over controls by either method, whereas other viruses, such as Epstein-Barr virus (EBV) and cytomegalovirus (CMV), were detected at comparable levels. These direct methods of viral detection do not suggest an association between HHV-6 and AD.

The comorbidity of HIV-associated neurocognitive disorders and Alzheimer's disease: a foreseeable medical challenge in post-HAART era

Although the introduction of highly active antiretroviral therapy (HAART) has led to a strong reduction of HIV-associated dementia (HAD) incidence, the prevalence of minor HIV-1-associated neurocognitive disorder (HAND) is rising among AIDS patients. HAART medication has shifted neuropathology from a subacute encephalitic condition to a subtle neurodegenerative process involving synaptic and dendritic degeneration, particularly of hippocampal neurons that are spared prior to HAART medication. Considerable neuroinflammation coupled with mononuclear phagocyte activation is present in HAART-medicated brains, particularly in the hippocampus. Accumulating evidence suggests that the resultant elevated secretion of pro-inflammatory cytokines such as interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta can increase amyloid-beta peptide (Abeta) generation and reduce Abeta clearance. Recent advancements in Alzheimer's disease (AD) research identified Abeta biogenesis and clearance venues that are potentially influenced by HIV viral infection, providing new insights into beta-amyloidosis segregation in HIV patients. Our study suggests enhanced beta-amyloidosis in ART-treated HAD and HIV-associated encephalitis brains and suppression of Abeta clearance by viral infection of human primary macrophages. A growing awareness of potential convergent mechanisms leading to neurodegeneration shared by HIV and Abeta points to a significant chance of comorbidity of AD and HAND in senile HIV patients, which calls for a need of basic studies.

Herpes simplex virus type 1, apolipoprotein E, and cholesterol: A dangerous liaison in Alzheimer’s disease and other disorders

Almost a hundred years ago, the main neuropathological features of Alzheimer's disease (AD) brain were discovered, yet the underlying cause(s) are still unknown, and the disease is basically untreatable. Despite the very numerous studies on the neuropathological features, the cause(s) of their production and whether they have an aetiological role in the disease or are merely end-products ("tombstones") are still unknown. Indeed, until fairly recently, the only known risk factors were age, Down's syndrome and head injury. A susceptibility factor, the type 4 allele of the apolipoprotein E gene was identified, but it is neither essential nor sufficient to cause AD, so other factors must be involved also. We investigated the possibility of a viral role and discovered that HSV1 DNA is present in brain of a high proportion of elderly people and that in combination with APOE-epsilon4 it confers a high risk of AD. Subsequently, we found that APOE determines outcome of infection in several diseases caused by diverse infectious agents. Here we describe our studies, and the few others carried out elsewhere, on the mechanism of action of HSV1 and the dependence of the damage on APOE. We discuss, in relation to HSV1 action on lipids and to the spread of the virus via lipid rafts in brain, the possible involvement in AD of cholesterol, a vital and major component of the human brain, and the dispute over whether statins, drugs used for lowering cholesterol levels, are protective against the disease. We also link the damage due to two major consequences of HSV1 infection--inflammatory and oxidative processes--to lipid peroxidation in brain, and consider the influence of the different apoE isoforms in this process.

Intracerebral propagation of Alzheimer's disease: strengthening evidence of a herpes simplex virus etiology

BACKGROUND

A faulty human protein, abnormally phosphorylated tau, was recently publicized to spread "like a virus" from neuron to neuron in Alzheimer's patients' brains. For several decades, we have been amassing arguments showing that herpes simplex virus type 1 (HSV-1), not p-tau, propagates this interneuronal, transsynaptic pathologic cascade.

METHODS

We reiterate convincing data from our own (and other) laboratories, reviewing the first anatomic foothold neurofibrillary tangles gain in brainstem and/or entorhinal cortex; the chronic immunosurveillance cellularity of the trigeminal ganglia wherein HSV-1 awakens from latency to reactivate; the inabilities of p-tau protein's physical properties to promote it to jump synapses; the amino acid homology between human p-tau and VP22, a key target for phosphorylation by HSV serine/threonine-protein kinase UL13; and the exosomic secretion of HSV-1-infected cells' L-particles, attesting to the cell-to-cell passage of microRNAs of herpesviruses.

RESULTS

The now-maturing construct that reactivated HSV-1 best accounts for the intracerebral propagation of AD changes in the human brain should at last seem highly attractive. This hypothesis might even explain statins' apparent mechanism in some studies for lowering AD incidence.

CONCLUSION

Provided that funding agencies will quickly ignite a new realm of investigation, the rejuvenated enthusiasm for testing this optimistic construct holds incalculable potential for rapid, efficacious clinical application, through already available and relatively safe antiviral therapeutics.

Herpes simplex virus type 1 and Alzheimer's disease

Until recently, the only risk factors implicated in noninherited cases of Alzheimer's disease were increasing age, Down's syndrome, and probably, head injury. Having found that herpes simplex type 1 virus (HSV1) is present in the brain of many elderly people, we discovered that it is a risk factor for Alzheimer's disease when in the central nervous system of APOE-epsilon4 allele carriers. On the basis of this result and our finding that apoE-epsilon4 is a risk factor for herpes labialis, we suggested that the combination of virus and genetic factor is particularly damaging in the nervous system. The present review describes 1) the search for HSV1 in human brain; 2) HSV1 infection of the peripheral nervous system; 3) HSV1 infection of the central nervous system; 4) how APOE genotype might influence HSV1 infection; 5) possible APOE genotype effect on viral latency and its reactivation; 6) interactions of viruses with lipoproteins, their components, and lipoprotein receptors; 7) the role of APOE in repair; 8) pathological processes in AD and their relationship to prior damage; and 9) implications for the prevention or treatment of Alzheimer's disease.

Herpes simplex virus interferes with amyloid precursor protein processing

BACKGROUND

The early events underlying Alzheimer's disease (AD) remain uncertain, although environmental factors may be involved. Work in this laboratory has shown that the combination of herpes simplex virus type 1 (HSV1) in brain and carriage of the APOE-epsilon4 allele of the APOE gene strongly increases the risk of developing AD. The development of AD is thought to involve abnormal aggregation or deposition of a 39-43 amino acid protein--beta amyloid (Abeta)--within the brain. This is cleaved from the much larger transmembranal protein 'amyloid precursor protein' (APP). Any agent able to interfere directly with Abeta or APP metabolism may therefore have the capacity to contribute towards AD. One recent report showed that certain HSV1 glycoprotein peptides may aggregate like Abeta; a second study described a role for APP in transport of virus in squid axons. However to date the effects of acute herpesvirus infection on metabolism of APP in human neuronal-type cells have not been investigated. In order to find if HSV1 directly affects APP and its degradation, we have examined this protein from human neuroblastoma cells (normal and transfected with APP 695) infected with the virus, using Western blotting.

RESULTS

We have found that acute HSV1 (and also HSV2) infection rapidly reduces full length APP levels--as might be expected--yet surprisingly markedly increases levels of a novel C-terminal fragment of APP of about 55 kDa. This band was not increased in cells treated with the protein synthesis inhibitor cycloheximide

CONCLUSION

Herpes virus infection leads to rapid loss of full length APP from cells, yet also causes increased levels of a novel 55 kDa C-terminal APP fragment. These data suggest that infection can directly alter the processing of a transmembranal protein intimately linked to the aetiology of AD.

Herpes and Alzheimer's Disease: Subversion in the Central Nervous System and How It Might Be Halted

The last 8 or so years have seen a large increase in the number of studies supporting the concept of a major role for herpes simplex virus type 1 (HSV1) in Alzheimer's disease (AD). The main advances have been made through studies in humans and in mice, investigating the likelihood of reactivation of the latent virus in brain. Others have aimed to explain the mechanisms in cells whereby the increase in amyloid-beta (Aβ) production on HSV1 infection of cells and mouse brains occurs, and the reason that infected cells make this increase. The possibility that other herpesviruses are involved in the development of AD has been explored, and human herpesvirus type 6, Epstein-Barr virus, and cytomegalovirus, in particular, have been implicated. Epidemiological studies have further supported the role specifically of HSV1 and its reactivation in the disease. Antiviral studies have continued, comparing those acting by different mechanisms, such as restricting viral replication, or blocking viral entry into cells, to treat HSV1-infected cell cultures, and then examining the extent to which the virus-induced increases in Aβ and AD-like tau are reduced. All the studies support the usage of antiviral treatment to slow or halt the progression of AD.

Can Better Management of Periodontal Disease Delay the Onset and Progression of Alzheimer's Disease?

A risk factor relationship exists between periodontal disease and Alzheimer's disease (AD) via tooth loss, and improved memory following dental intervention. This links the microbial contribution from indigenous oral periodontal pathogens to the manifestation of chronic conditions, such as AD. Here, we use Porphyromonas gingivalis infection to illustrate its effect on mental health. P. gingivalis infection, in its primary sub-gingival niche, can cause polymicrobial synergy and dysbiosis. Dysbiosis describes the residency of select commensals from the oral cavity following co-aggregation around the dominant keystone pathogen, such as P. gingivalis, to gain greater virulence. The initial process involves P. gingivalis disturbing neutrophil mediated innate immune responses in the healthy gingivae and then downregulating adaptive immune cell differentiation and development to invade, and subsequently, establish new dysbiotic bacterial communities. Immune responses affect the host in general and functionally via dietary adjustments caused by tooth loss. Studies from animals orally infected with P. gingivalis confirm this bacterium can transmigrate to distant organ sites (the brain) and contribute toward peripheral and intracerebral inflammation, and compromise vascular and microvascular integrity. In another study, P. gingivalis infection caused sleep pattern disturbances by altering glial cell light/dark molecular clock activity, and this, in turn, can affect the clearance of danger associated molecular patterns, such as amyloid-β, via the glymphatic system. Since P. gingivalis can transmigrate to the brain and modulate organ-specific inflammatory innate and adaptive immune responses, this paper explores whether better management of indigenous periodontal bacteria could delay/prevent the onset and/or progression of dementia.

Reactivation of HSV-1 in the brain of patients with familial Alzheimer's disease

Herpes simplex virus type 1 (HSV-1) has been proposed as an environmental risk factor for sporadic Alzheimer's disease, although this issue is still in dispute. The involvement of HSV-1 in the pathogenesis of familial Alzheimer's disease, the uncommon type of Alzheimer's disease, has not been addressed yet. We investigated formalin-fixed, paraffin-embedded, postmortem brain tissue sections of three patients with familial Alzheimer's disease for the presence of HSV-1 DNA. The nested polymerase chain reaction (PCR) detected the HSV-1 glycoprotein D gene in the brain of all three patients with familial Alzheimer's disease preferentially in the frontal and temporal cortices, whereas only one case out of six age-matched, non-Alzheimer's disease individuals could disclose the presence of HSV-1 gene. The PCR detected HSV-1 DNA in the frontal cortex of the two patients with sporadic Alzheimer's disease. The presence of HSV-1 was associated with beta-amyloid deposition in the cerebral cortex. To clarify the localization of HSV-1 in the brain tissue of patients with familial Alzheimer's disease, the in situ hybridization of the tyramide signal amplification system was used. It detected the HSV-1-specific signals predominantly in the cytoplasm of cortical neurons in a dot-like staining fashion. In addition, high-sensitivity immunohistochemistry revealed the existence of HSV-1 antigens in the cytoplasm of cortical neurons. This report provides the first evidence of reactivation of HSV-1 in the brain of patients with familial Alzheimer's disease, associated with beta-amyloid deposition, and suggests the possible involvement of HSV-1 together with genetic factors in the pathogenesis of familial Alzheimer's disease.

Antiviral therapy: Valacyclovir Treatment of Alzheimer's Disease (VALAD) Trial: protocol for a randomised, double-blind,placebo-controlled, treatment trial

INTRODUCTION

After infection, herpes simplex virus-1 (HSV1) becomes latent in the trigeminal ganglion and can enter the brain via retrograde axonal transport. Recurrent reactivation of HSV1 may lead to neurodegeneration and Alzheimer's disease (AD) pathology. HSV1 (oral herpes) and HSV2 (genital herpes) can trigger amyloid beta-protein (Aβ) aggregation and HSV1 DNA is common in amyloid plaques. Anti-HSV drugs reduce Aβ and phosphorylated tau accumulation in cell-culture models. Cognitive impairment is greater in patients with HSV seropositive, and antiviral drugs show robust efficacy against peripheral HSV infection. Recent studies of electronic health records databases demonstrate that HSV infections increase dementia risk, and that antiviral medication treatment reduces this risk. The generic antiviral drug valacyclovir was superior to placebo in improving memory in a schizophrenia pilot trial but has not been tested in AD.

METHODS AND ANALYSIS

In patients with mild AD who test positive for HSV1 or HSV2 serum antibodies, valacyclovir, repurposed as an anti-AD drug, will be compared with placebo (lactose pills) in 130 patients (65 valacyclovir and 65 placebo) in a randomised, double-blind, 78-week phase II proof-of-concept trial. Patients on valacyclovir, dose-titrated from 2 g to a targeted oral dose of 4 g daily, compared with placebo, are hypothesised to show smaller cognitive and functional decline, and, using 18F-Florbetapir positron emission tomography (PET) and 18F-MK-6240 PET imaging, to show less amyloid and tau accumulation, respectively. In the lumbar puncture subsample, cerebrospinal fluid acyclovir will be assayed to assess central nervous system valacyclovir penetration.

ETHICS AND DISSEMINATION

The trial is being overseen by the New York State Psychiatric Institute Institutional Review Board (protocol 7537), the National Institute on Ageing, and the Data Safety Monitoring Board. Written informed consent is obtained for all subjects. Results will be disseminated via publication, clinicaltrials.gov, media and conferences.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov identifier (NCT03282916) Pre-results.

High avidity HSV-1 antibodies correlate with absence of amnestic Mild Cognitive Impairment conversion to Alzheimer's disease

Amnestic Mild Cognitive Impairment (aMCI) is an alteration in cognitive abilities that can progress to Alzheimer's disease (AD), a condition in which herpes simplex type 1 (HSV-1) infection might play a pathogenetic role. Prognostic indexes capable of predicting aMCI conversion to AD are only partially understood. The objective of the present work is to verify whether HSV-1 immune responses is involved in conversion of aMCI to AD and correlate with grey matter brain morphometry. Two homogeneous groups of individuals who did or did not convert to AD over a 24-months period were selected after retrospective analysis of a cohort of patients with a diagnosis of aMCI. The selection of subjects was based on: a) clinical follow-up; b) neurocognitive evaluation at baseline and after 24months; c) availability of serum and DNA samples at baseline. 36 aMCI individuals, 21 of whom did (aMCI-converters) and 15 of whom did not (aMCI-non-converters) convert to AD, were included in the study. HSV-1 antibody (Ab) titers, avidity index and APOE genotyping were performed in all the enrolled individuals at baseline. Brain magnetic resonance imaging (MRI) by 1.5T scanner results at baseline were available as well in most (29/36) of these individuals. HSV-1-specific Ab titers were increased at baseline in aMCI-non-converters, and the avidity of these Ab was significantly higher in aMCI-non-converter compared to aMCI-converter (p=0.0018). Receiver operating characteristics analysis showed that HSV-1 avidity had a predictive value in distinguishing between aMCI-non-converters and aMCI-converters (p<0.0001). Notably, a positive correlation was detected as well between HSV-1 antibody titers and MRI-evaluated cortical volumes in the left hippocampus and amigdala (p_corr<0.05). In conclusion, stronger HSV-1-specific humoral responses associate with protection against AD conversion and better-preserved cortical volumes. These results reinforce the hypothesis for a role for HSV-1 in the pathogenesis of AD.

Neurotropic viruses and Alzheimer's disease: a search for varicella zoster virus DNA by the polymerase chain reaction

BACKGROUND

In studies on the possible role of viruses in the aetiopathogenesis of Alzheimer's disease, herpes simplex virus type 1 (HSV1) DNA was detected by the polymerase chain reaction (PCR) in a high proportion of normal elderly people and of patients with Alzheimer's disease. The combination of HSV1 and a host factor, the type 4 allele of the gene for apolipoprotein E, is a strong risk factor for the disease.

METHODS

Brain specimens were examined for another herpes virus, varicella zoster (VZV), which, like HSV1, is neurotropic, has a predilection for residing latently in the peripheral nervous system, and can reactivate.

RESULTS

Using primers for sequences in the VZV origin of replication gene or thymidine kinase gene, VZV DNA was not found in any of 24 samples (18 HSV1 positive), from 17 patients with Alzheimer's disease, nor in 20 samples (12 HSV1 positive from 12 aged normal people. Hybridisation of the PCR products with a radiolabelled oligonucleotide probe capable of detecting less than 10 copies of the target sequence, confirmed the absence of VZV DNA.

CONCLUSION

The presence of one neurotropic virus--HSV1--and the absence of another--VZV--in aged human brains is consistent with a role for HSV1 in the aetiology of Alzheimer's disease.

Neurotropic viruses and Alzheimer disease. Interaction of herpes simplex type 1 virus and apolipoprotein E in the etiology of the disease

Infectious agents have been proposed as possible etiological factors in sporadic cases of Alzheimer disease (AD), herpes simplex type 1 virus (HSV1) being a likely candidate. We have detected laten HSV1 in brain from AD patients and from aged normal individuals, using polymerase chain reaction (PCR), in the regions most affected in the disease. In contrast, we have not detected another neurotropic herpes virus, varicella zoster (VZV), in any brains. We have postulated that HSV1 reactivates periodically, and that a host or viral characteristic determines the degree of damage caused by the resulting acute infection-with much greater damage in the case of AD patients. We have therefore examined a host factor-the apolipoprotein E (apoE) genotype, since the E4 allele is a known risk factor in the disease. We have found that the risk of developing AD is much greater in those who are HSV1-positive in brain and who possess an apoE4 allele than for those with only one of these factors.