The influence of latent viral infection on rate of cognitive decline over 4 years

Negative Association of Cognitive Performance With Blood Serum Neurotoxicity and Its Modulation by Human Herpes Virus 5 (HHV5) Seropositivity in Healthy Women

Identification of early influences on cognitive decline is of paramount importance in order to stem the impacts of decrements in cognitive functioning and to potentially intervene. Thus, here we focused on 132 healthy adult women (age range 26-98 years) to (a) determine whether factors circulating in serum may exert neurotoxic effects in vitro, (b) evaluate associations between serum neurotoxicity and cognitive performance, and (c) assess the influence of human herpes virus (HHV) seroprevalence and other factors on apoptosis and cognitive performance. The results documented that the addition of serum from healthy adult women to neural cell cultures resulted in apoptosis, indicating the presence of circulating neurotoxic factors in the serum. Furthermore, apoptosis increased with age, and was associated with decreased cognitive performance. Stepwise regression evaluating the influence of 6 HHVs on apoptosis and cognitive function revealed that only HHV5 (cytomegalovirus; CMV) seropositivity was significantly associated with apoptosis and cognitive decline, controlling for age. These findings document neurotoxic effects of serum from healthy women across the adult lifespan and suggest a unique detrimental influence associated with CMV seropositivity.

Human Cytomegalovirus Infection and Neurocognitive and Neuropsychiatric Health

A common infection, human cytomegalovirus (HCMV) has been associated with a variety of human diseases, including cardiovascular disease and possibly certain cancers. HCMV has also been associated with cognitive, psychiatric, and neurological conditions. Children with congenital or early-life HCMV are at risk for microcephaly, cerebral palsy, and sensorineural hearing loss, although in many cases sensorineural loss may resolve. In addition, HCMV can be associated with neurodevelopmental impairment, which may improve with time. In young, middle-aged, and older adults, HCMV has been adversely associated with cognitive function in some but not in all studies. Research has linked HCMV to Alzheimer's and vascular dementia, but again not all findings consistently support these associations. In addition, HCMV has been associated with depressive disorder, bipolar disorder, anxiety, and autism-spectrum disorder, although the available findings are likewise inconsistent. Given associations between HCMV and a variety of neurocognitive and neuropsychiatric disorders, additional research investigating reasons for the considerable inconsistencies in the currently available findings is needed. Additional meta-analyses and more longitudinal studies are needed as well. Research into the effects of antiviral medication on cognitive and neurological outcomes and continued efforts in vaccine development have potential to lower the neurocognitive, neuropsychiatric, and neurological burden of HCMV infection.

Cognitive Effects of Toxoplasma and CMV Infections: A Cross-Sectional Study of 557 Young Adults Considering Modulation by Sex and Rh Factor

One-third of humanity harbors a lifelong infection with Toxoplasma gondii, and probably about 80% are infected with human cytomegalovirus (CMV). This study aims to delineate the associations between toxoplasmosis and cognitive abilities and compare these to the associations with CMV. We evaluated the cognitive performance of 557 students, who had been examined for Toxoplasma and CMV infections, using intelligence, memory, and psychomotor tests. The results indicated cognitive impairments in seropositive individuals for both pathogens, with variations in cognitive impact related to sex and the Rh factor. Specifically, Toxoplasma infection was associated with lower IQ in men, whereas CMV was predominantly associated with worse performance by women when testing memory and reaction speeds. Analysis of the antibody concentrations indicated that certain Toxoplasma-associated cognitive detrimental effects may wane (impaired intelligence) or worsen (impaired reaction times) over time following infection. The findings imply that the cognitive impairments caused by both neurotropic pathogens are likely due to pathological changes in the brain rather than from direct manipulative action by the parasites.

Molecular characterization of plasma virome of hepatocellular carcinoma (HCC) patients

Hepatocellular carcinoma (HCC) stands as the most common cancer type, arising from various causes, and responsible for a substantial number of cancer-related fatalities. Recent advancements in viral metagenomics have empowered scientists to delve into the intricate diversity of the virosphere, viral evolution, interactions between viruses and their hosts, and the identification of viral causes behind disease outbreaks, the development of specific symptoms, and their potential role in altering the host's physiology. The present study had the objective of "Molecular Characterization of HBV, HCV, anelloviruses, CMV, SENV-D, SENV-H, HEV, and HPV viruses among individuals suffering from HCC." A total of 381 HCC patients contributed 10 cc of blood each for this study. The research encompassed the assessment of tumor markers, followed by molecular characterization of HBV, HCV, Anelloviruses (TTV, TTMV, and TTMDV), SENV-H and SENV-D viruses, HEV, CMV, and HPV, as well as histopathological examinations. The outcomes of this study revealed that majority of the HCC patients 72.4% (276/381) were male as compared to females. HCV infection, at 76.4% (291 out of 381), exhibited a significant association (p < 0.05) with HCC. Most patients displayed singular lesions in the liver, with Child Pugh Score Type B being the predominant finding in 45.2% of cases. Plasma virome analysis indicated the prevalence of TTMDV (75%), followed by TTMV (70%) and TTV (42.1%) among anelloviruses in HCC patients. Similarly, SENV-H (52%) was followed by SENV-D (20%), with co-infections at 15%. The presence of CMV and HEV among the HCC patients was recorded 5% each however 3.5% of the patients showed the presence of HPV. In conclusion, this study underscores that HCC patients serve as reservoirs for various pathogenic and non-pathogenic viruses, potentially contributing to the development, progression, and severity of the disease.

Cytomegalovirus IgG is Associated With Physical Function But Not Muscle Density in People With HIV

BACKGROUND

Cytomegalovirus (CMV) seropositivity is associated with poor outcomes, including physical function impairment, in people without HIV. We examined associations between CMV IgG titer and physical function in virologically suppressed people with HIV (PWH).

METHODS

REPRIEVE is a double-blind randomized trial evaluating pitavastatin for primary prevention of atherosclerotic cardiovascular disease in PWH. This analysis focused on participants enrolled in a substudy with additional biomarker testing, imaging [coronary CT angiography], and physical function measures at entry. CMV IgG was measured using quantitative enzyme immunoassay, physical function by Short Physical Performance Battery, and muscle density and area by CT. Associations between CMV IgG (risk factor) and outcomes were evaluated using the partial Spearman correlation and linear and log-binomial regression.

RESULTS

Among 717 participants, 82% male, the median CMV IgG was 2716 (Q1, Q3: 807, 6672) IU/mL, all above the limit of quantification. Among 631 participants with imaging, there was no association between CMV IgG and CT-based muscle density or area, controlling for age (r = -0.03 and r = -0.01, respectively; P ≥ 0.38). Among 161 participants with physical function data, higher CMV IgG was associated with poorer overall modified Short Physical Performance Battery score ( P = 0.02), adjusted for age, nadir CD4, and high-sensitivity C-reactive protein.

CONCLUSIONS

Higher CMV IgG titer was associated with poorer physical function, not explained by previous immune compromise, inflammation, or muscle density or area. Further mechanistic studies are needed to understand this association and whether CMV-specific therapy can affect physical function in PWH.

Sociodemographic patterns in biomarkers of aging in the Add Health cohort

Biomarkers in population health research serve as indicators of incremental physiological deterioration and contribute to our understanding of mechanisms through which social disparities in health unfold over time. Yet, few population-based studies incorporate biomarkers of aging in early midlife, when disease risks may emerge and progress across the life course. We describe the distributions of several biomarkers of inflammation and neurodegeneration and their variation by sociodemographic characteristics using blood samples collected during Wave V of the National Longitudinal Study of Adolescent to Adult Health (ages 33-44 years). Higher mean levels of inflammatory and neurodegenerative biomarkers were associated with greater socioeconomic disadvantage. For example, the neurodegenerative markers, Neurofilament Light Chain and total Tau proteins were higher among lower income groups, though the relationship was not statistically significant. Similarly, proinflammatory marker Tumor Necrosis Factor-α (TNF-α) levels were higher among those with lower education. Significant differences in the mean levels of other proinflammatory markers were observed by race/ethnicity, sex, census region, BMI, and smoking status. These descriptive findings indicate that disparities in biomarkers associated with aging are already evident among young adults in their 30s and attention should focus on age-related disease risk earlier in the life course.

Intrathecal production of anti-Epstein-Barr virus viral capsid antigen IgG is associated with neurocognition and tau proteins in people with HIV

OBJECTIVE

HIV and Epstein-Barr virus (EBV) co-infection has been linked to increased immune activation and larger HIV reservoir. We assessed whether anti-EBV humoral responses are associated with increased cerebrospinal fluid (CSF) inflammation and with neurocognitive impairment (NCI) in people with HIV (PWH).

DESIGN

Cross-sectional analysis in 123 EBV-seropositive PWH either on antiretroviral therapy ( n  = 70) or not.

METHODS

Serum and CSF anti-EBV viral capsid antigen immunoglobulin G (anti-EVI) and CSF EBV DNA were measured by commercial immunoassay and RT-PCR. Seventy-eight participants without neurological confounding factors underwent neurocognitive assessment (Global Deficit Score, GDS). CSF total tau and 181-phosphorylated-tau (ptau) were measured by immunoassays together with biomarkers of blood-brain barrier (BBB) integrity, immune activation, astrocytosis, and intrathecal synthesis. Logistic and linear regressions and moderation analysis were used to investigate the relationships between CSF anti-EVI, GDS, and biomarkers.

RESULTS

Twenty-one (17.1%) and 22 participants (17.9%) had detectable CSF anti-EVI (10.5-416.0 U/ml) and CSF EBV DNA (25-971 copies/ml). After adjusting for BBB integrity, age, and clinical factors, the presence of CSF anti-EVI was only associated with serum levels of anti-EVI, and not with CSF EBV DNA. CSF anti-EVI, tau and ptau showed reciprocal interactions affecting their associations with GDS. After adjusting for demographics and clinical parameters, higher CSF anti-EVI levels were associated with worse GDS (aβ 0.45, P  < 0.001), and CSF levels of tau and ptau had a moderation effect on the strength of this association (models' P  < 0.001).

CONCLUSION

Humoral immune responses against EBV within the central nervous system may contribute to NCI in PWH through mechanisms that involve neuronal injury.

Viral Infections, Are They a Trigger and Risk Factor of Alzheimer's Disease?

Alzheimer's Disease (AD), a progressive and debilitating condition, is reported to be the most common type of dementia, with at least 55 million people believed to be currently affected. Many causation hypotheses of AD exist, yet the intriguing link between viral infection and its possible contribution to the known etiology of AD has become an attractive focal point of research for the field and a challenging study task. In this review, we will explore the historical perspective and milestones that led the field to investigate the viral connection to AD. Specifically, several viruses such as Herpes Simplex Virus 1 (HSV-1), Zika virus (ZIKV), and severe cute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with several others mentioned, include the various viruses presently considered within the field. We delve into the strong evidence implicating these viruses in the development of AD such as the lytic replication and axonal transport of HSV-1, the various mechanisms of ZIKV neurotropism through the human protein Musashi-1 (MSI1), and the spread of SARS-CoV-2 through the transfer of the virus through the BBB endothelial cells to glial cells and then to neurons via transsynaptic transfer. We will also explore beyond these mere associations by carefully analyzing the potential mechanisms by which these viruses may contribute to AD pathology. This includes but is not limited to direct neuronal infections, the dysregulation of immune responses, and the impact on protein processing (Aβ42 and hyperphosphorylated tau). Controversies and challenges of the virus-AD relationship emerge as we tease out these potential mechanisms. Looking forward, we emphasize future directions, such as distinct questions and proposed experimentations to explore, that the field should take to tackle the remaining unanswered questions and the glaring research gaps that persist. Overall, this review aims to provide a comprehensive survey of the past, present, and future of the potential link between viral infections and their association with AD development while encouraging further discussion.

Single-Cell RNA Sequencing Transcriptomics Revealed HCMV IE2-Related Microglia Responses in Alzheimer's-Like Disease in Transgenic Mice

    Although multiple factors are known to concur with Alzheimer's disease (AD), the relationship between human cytomegalovirus (HCMV) and AD-like disease is unclear. Here, we propose a hypothesis that HCMV immediate-early 2 (IE2) protein promotes microglia activation and thus leads to AD-like disease. We successfully constructed IE2 transgenic mice expressing IE2 in the hippocampus. Single-cell sequencing analysis revealed that IE2 promoted the activation of microglia and upregulated the expression of disease-associated microglia genes. Differentially expressed gene analysis and pathway enrichment revealed that IE2 upregulated immune and nervous system disease-related genes. Immunohistochemical analysis showed that the expressions of both amyloid precursor protein (APP) and p-Tau were significantly upregulated in the brains of IE2 mice and were markers of AD. Taken together, these findings provide useful insights into AD-like disease activated by HCMV IE2.

Herpesviridae, Neurodegenerative Disorders and Autoimmune Diseases: What Is the Relationship between Them?

Alzheimer's disease and Parkinson's disease represent the most common forms of cognitive impairment. Multiple sclerosis is a chronic inflammatory disease of the central nervous system responsible for severe disability. An aberrant immune response is the cause of myelin destruction that covers axons in the brain, spinal cord, and optic nerves. Systemic lupus erythematosus is an autoimmune disease characterized by alteration of B cell activation, while Sjögren's syndrome is a heterogeneous autoimmune disease characterized by altered immune responses. The etiology of all these diseases is very complex, including an interrelationship between genetic factors, principally immune associated genes, and environmental factors such as infectious agents. However, neurodegenerative and autoimmune diseases share proinflammatory signatures and a perturbation of adaptive immunity that might be influenced by herpesviruses. Therefore, they might play a critical role in the disease pathogenesis. The aim of this review was to summarize the principal findings that link herpesviruses to both neurodegenerative and autoimmune diseases; moreover, briefly underlining the potential therapeutic approach of virus vaccination and antivirals.

Immunosenescence and Cytomegalovirus: Exploring Their Connection in the Context of Aging, Health, and Disease

Aging induces numerous physiological alterations, with immunosenescence emerging as a pivotal factor. This phenomenon has attracted both researchers and clinicians, prompting profound questions about its implications for health and disease. Among the contributing factors, one intriguing actor in this complex interplay is human cytomegalovirus (CMV), a member of the herpesvirus family. Latent CMV infection exerts a profound influence on the aging immune system, potentially contributing to age-related diseases. This review delves into the intricate relationship between immunosenescence and CMV, revealing how chronic viral infection impacts the aging immune landscape. We explore the mechanisms through which CMV can impact both the composition and functionality of immune cell populations and induce shifts in inflammatory profiles with aging. Moreover, we examine the potential role of CMV in pathologies such as cardiovascular diseases, cancer, neurodegenerative disorders, COVID-19, and Long COVID. This review underlines the importance of understanding the complex interplay between immunosenescence and CMV. It offers insights into the pathophysiology of aging and age-associated diseases, as well as COVID-19 outcomes among the elderly. By unraveling the connections between immunosenescence and CMV, we gain a deeper understanding of aging's remarkable journey and the profound role that viral infections play in transforming the human immune system.

Human cytomegalovirus induces significant structural and functional changes in terminally differentiated human cortical neurons

IMPORTANCE

Human cytomegalovirus (HCMV) is a highly prevalent viral pathogen that can cause serious neurological deficits in infants experiencing an in utero infection. Also, as a life-long infection, HCMV has been associated with several diseases in the adult brain. HCMV is known to infect early neural progenitor cells, but whether it also infects terminally differentiated neurons is still debated. Here, we differentiated human-induced pluripotent stem cells into neurons for 84-120 days to test the ability of HCMV to infect terminally differentiated neurons and assess the downstream functional consequences. We discovered that mature human neurons are highly permissive to HCMV infection, exhibited late replication hallmarks, and produced infectious virus. Moreover, infection in terminally differentiated neurons essentially eliminated neuron function. These results demonstrate that terminally differentiated human neurons are permissive to HCMV infection, which can significantly alter both structural and functional features of this mature neuron population.

Prevalence of active cytomegalovirus infection at diagnosis of ovarian cancer and during chemotherapy and subsequent changes in cognitive functioning

PURPOSE

One of the most frequently reported effects of cancer and its treatments is cancer-related cognitive impairment (CRCI). Viral infections may affect inflammation and immune function and therefore may influence patient symptoms, including CRCI. The goal of this study was to describe the prevalence of cytomegalovirus (CMV) infections at diagnosis, during, and after chemotherapy in individuals with ovarian cancer and explore CMV infection at diagnosis with cancer-related cognitive impairment (CRCI) following chemotherapy.

METHODS

We recruited adults newly diagnosed with ovarian, primary peritoneal or fallopian tube cancer at a single academic cancer center into two prospective studies. In Study 1 (N = 71), participants provided blood samples at diagnosis. In Study 2 (N = 18), participants provided blood samples and completed symptom surveys before, during and after front-line adjuvant chemotherapy. Serum CMV DNA levels were assessed using digital PCR; >100 copies/mL of serum was considered positive for active CMV infection (CMV+). CRCI was measured using the Functional Assessment of Cancer Therapy - Cognitive Function (FACT-Cog) questionnaire. Changes in FACT-Cog scores were compared by CMV status at diagnosis using t-tests at each time point.

RESULTS

At diagnosis, 29.2% were CMV+ (28.2% in Study 1, 33.3% in Study 2). Following three cycles of chemotherapy (Study 2), CMV positivity rose to 60.0% and then back down to 31.3% after chemotherapy. We observed significant differences in CRCI following chemotherapy by CMV status at diagnosis.

CONCLUSION

Our data suggest that active CMV infection is common among patients undergoing treatment for ovarian cancer and may contribute to symptoms of CRCI.

Cardiovascular health, infection burden and their interactive association with brain volumetric and white matter integrity outcomes in the UK Biobank

BACKGROUND

Cardiovascular health is associated with brain magnetic resonance imaging (MRI) markers of pathology and infections may modulate this association.

METHODS

Using data from 38,803 adults (aged 40-70 years) and followed-up for 5-15 years, we tested associations of prevalent total (47.5%) and hospital-treated infection burden (9.7%) with brain structural and diffusion-weighted MRI (i.e., sMRI and dMRI, respectively) common in dementia phenome. Poor white matter tissue integrity was operationalized with lower global and tract-specific fractional anisotropy (FA) and higher mean diffusivity (MD). Volumetric sMRI outcomes included total, gray matter (GM), white matter (WM), frontal bilateral GM, white matter hyperintensity (WMH), and selected based on previous associations with dementia. Cardiovascular health was measured with Life's Essential 8 score (LE8) converted to tertiles. Multiple linear regression models were used, adjusting for intracranial volumes (ICV) for subcortical structures, and for demographic, socio-economic, and the Alzheimer's Disease polygenic risk score for all outcomes, among potential confounders.

RESULTS

In fully adjusted models, hospital-treated infections were inversely related to GM (β ± SE: -1042 ± 379, p = 0.006) and directly related to WMH as percent of ICV (Loge transformed) (β ± SE:+0.026 ± 0.007, p < 0.001). Both total and hospital-treated infections were associated with poor WMI, while the latter was inversely related to FA within the lowest LE8 tertile (β ± SE:-0.0011 ± 0.0003, p < 0.001, PLE8×IB < 0.05), a pattern detected for GM, Right Frontal GM, left accumbens and left hippocampus volumes. Within the uppermost LE8 tertile, total infection burden was linked to smaller right amygdala while being associated with larger left frontal GM and right putamen volumes, in the overall sample. Within that uppermost tertile of LE8, caudate volumes were also positively associated with hospital-treated infections.

CONCLUSIONS

Hospital-treated infections had more consistent deleterious effects on volumetric and white matter integrity brain neuroimaging outcomes compared with total infectious burden, particularly in poorer cardiovascular health groups. Further studies are needed in comparable populations, including longitudinal studies with multiple repeats on neuroimaging markers.

Viruses - a major cause of amyloid deposition in the brain

INTRODUCTION

Clinically, Alzheimer's disease (AD) is a syndrome with a spectrum of various cognitive disorders. There is a complete dissociation between the pathology and the clinical presentation. Therefore, we need a disruptive new approach to be able to prevent and treat AD.

AREAS COVERED

In this review, the authors extensively discuss the evidence why the amyloid beta is not the pathological cause of AD which makes therefore the amyloid hypothesis not sustainable anymore. They review the experimental evidence underlying the role of microbes, especially that of viruses, as a trigger/cause for the production of amyloid beta leading to the establishment of a chronic neuroinflammation as the mediator manifesting decades later by AD as a clinical spectrum. In this context, the emergence and consequences of the infection/antimicrobial protection hypothesis are described. The epidemiological and clinical data supporting this hypothesis are also analyzed.

EXPERT OPINION

For decades, we have known that viruses are involved in the pathogenesis of AD. This discovery was ignored and discarded for a long time. Now we should accept this fact, which is not a hypothesis anymore, and stimulate the research community to come up with new ideas, new treatments, and new concepts.

Longitudinal Effects of Herpesviruses on Multiple Cognitive Outcomes in Healthy Elderly Adults

BACKGROUND

Herpesviruses have been proposed to be involved in Alzheimer's disease development as potentially modifiable pathology triggers.

OBJECTIVE

To investigate associations of serum antibodies for herpes simplex virus (HSV)-1 and cytomegalovirus (CMV) and anti-herpesvirus treatment with cognitive outcomes in relation to interactions with APOE ɛ4.

METHODS

The study included 849 participants in the population-based Prospective Investigation of the Vasculature in Uppsala Seniors study. Cognitive performance at the ages of 75 and 80 years was assessed using the Mini-Mental State Examination (MMSE), trail-making test (TMT) A and B, and 7-minute screening test (7MS).

RESULTS

Anti- HSV-1 IgG positivity was associated cross-sectionally with worse performance on the MMSE, TMT-A, TMT-B, 7MS, enhanced free recall, and verbal fluency tests (p = 0.016, p = 0.016, p <  0.001, p = 0.001, p = 0.033, and p <  0.001, respectively), but not orientation or clock drawing. Cognitive scores did not decline over time and longitudinal changes did not differ according to HSV-1 positivity. Anti- CMV IgG positivity was not associated cross-sectionally with cognition, but TMT-B scores declined more in anti- CMV IgG carriers. Anti- HSV-1 IgG interacted with APOE ɛ4 in association with worse TMT-A and better enhanced cued recall. Anti- HSV IgM interacted with APOE ɛ4 and anti-herpesvirus treatment in association with worse TMT-A and clock drawing, respectively.

CONCLUSION

These findings indicate that HSV-1 is linked to poorer cognition in cognitively healthy elderly adults, including impairments in executive function, memory, and expressive language. Cognitive performance did not decline over time, nor was longitudinal decline associated with HSV-1.

A systematic literature review on the humanistic burden of cytomegalovirus

OBJECTIVE

Cytomegalovirus (CMV) infection is typically asymptomatic in healthy individuals; however, certain populations are vulnerable to infection and may develop serious sequelae. CMV infection may also have a broad impact on humanistic outcomes, including patient health status and quality of life (QoL). We conducted a systematic literature review (SLR) to describe the global humanistic burden of CMV and congenital CMV (cCMV) infections across all age groups.

METHODS

Medline, Embase, and LILACS were searched to identify studies on humanistic outcomes following CMV infection, including health status/QoL and any outcomes in domains such as auditory, cognitive ability, developmental status, intelligence, language, memory, mental health, motor performance, social communication, speech, and vocabulary. The SLR included articles published from 2000-2020 and focused geographically on Australia, Europe, Israel, Japan, Latin America, and North America.

RESULTS

Sixty-three studies met the inclusion criteria. In general, individuals with symptomatic cCMV infection experience a greater burden of disease and more substantial impact on QoL versus those with asymptomatic cCMV infection. Children with hearing loss due to cCMV infection, both symptomatic and asymptomatic, showed improved auditory outcomes following cochlear implantation. Newborns, infants, and children with cCMV infections had worse cognitive outcomes in psychological development, sequential and simultaneous processing, phonological working memory, and attention control versus age-matched controls without cCMV infection. CMV infection was also associated with cognitive decline in elderly populations.

CONCLUSIONS

CMV infection can have substantial, lifelong, heterogenous impacts on humanistic outcomes, including health status and QoL, which should be considered when developing and implementing treatment and prevention strategies.

Human Cytomegalovirus Induces Significant Structural and Functional Changes in Terminally Differentiated Human Cortical Neurons

Human cytomegalovirus (HCMV) is a highly prevalent viral pathogen that typically presents asymptomatically in healthy individuals despite lifelong latency. However, in 10-15% of congenital cases, this beta-herpesvirus demonstrates direct effects on the central nervous system, including microcephaly, cognitive/learning delays, and hearing deficits. HCMV has been widely shown to infect neural progenitor cells, but the permissiveness of fully differentiated neurons to HCMV is controversial and chronically understudied, despite potential associations between HCMV infection with neurodegenerative conditions. Using a model system representative of the human forebrain, we demonstrate that induced pluripotent stem cell (iPSC)-derived, excitatory glutamatergic and inhibitory GABAergic neurons are fully permissive to HCMV, demonstrating complete viral replication, competent virion production, and spread within the culture. Interestingly, while cell proliferation was not induced in these post-mitotic neurons, HCMV did increase expression of proliferative markers Ki67 and PCNA suggesting alterations in cell cycle machinery. These finding are consistent with previous HCMV-mediated changes in various cell types and implicate the virus' ability to alter proliferative pathways to promote virion production. HCMV also induces significant structural changes in forebrain neurons, such as the formation of syncytia and retraction of neurites. Finally, we demonstrate that HCMV disrupts calcium signaling and decreases neurotransmission, with action potential generation effectively silenced after 15 days post infection. Taken together, our data highlight the potential for forebrain neurons to be permissive to HCMV infection in the CNS, which could have significant implications on overall brain health and function.

Socioeconomic and race/ethnic differences in immunosenescence: Evidence from the Health and Retirement Study

BACKGROUND

The COVID-19 pandemic has highlighted the urgent need to understand variation in immunosenescence at the population-level. Thus far, population patterns of immunosenescence have not well described.

METHODS

We characterized measures of immunosenescence from the 2016 Venous Blood Study from the nationally representative U.S Health and Retirement Study (HRS) of individuals ages 50 years and older.

RESULTS

Median values of the CD8+:CD4+, EMRA:Naïve CD4+ and EMRA:Naïve CD8+ ratios were higher among older participants and were lower in those with additional educational attainment. Generally, minoritized race and ethnic groups had immune markers suggestive of a more aged immune profile: Hispanics had a CD8+:CD4+ median value of 0.37 (95 % CI: 0.35, 0.39) compared to 0.30 in non-Hispanic Whites (95 % CI: 0.29, 0.31). Non-Hispanic Blacks had the highest median value of the EMRA:Naïve CD4+ ratio (0.08; 95 % CI: 0.07, 0.09) compared to non-Hispanic Whites (0.03; 95 % CI: 0.028, 0.033). In regression analyses, race/ethnicity and education were associated with large differences in the immune ratio measures after adjustment for age and sex.

CONCLUSIONS

Lower educational attainment and minoritized racial ethnic status were associated with higher levels of immunosenescence. This population variation may have important implications for both risk of age-related disease and vulnerability to emerging pathogens (e.g., SARS-CoV-2).

Links between inflammation and immune functioning with cognitive status among older Americans in the Health and Retirement Study

Elevated inflammation and poor immune functioning are tied to worse cognitive health. Both processes are fundamental to aging and are strongly implicated in the development of age-related health outcomes, including cognitive status. However, results from prior studies evaluating links between indicators of inflammation and immune function and cognitive impairment have been inconsistent due to biomarker selection, sample selection, and cognitive outcome. Using the Health and Retirement Study (HRS), a nationally representative study of older adults in the United States, we assessed how indicators of inflammation (neutrophil-lymphocyte ratio (NLR), albumin, CRP, IL6, IL10, IL-1Ra, sTNFR1, and TGFβ1) and immune functioning (CMV, CD4+ TN/TM, and CD8+ TN/TM) are associated with cognitive status. First, to examine the association between each biomarker and cognitive status, we tested whether markers of inflammation and immune functioning varied across cognitive status categories. We found that dementia and cognitive impairment without dementia (CIND) were associated with elevated inflammation and poorer immune functioning across biomarkers except for CD4+ TN/TM. Next, we estimated multinomial logistic regression models to assess which biomarkers would continue to be associated with dementia and CIND, net of each other. In these models, albumin, cytokines, CMV, CD4+ TN/TM, and CD8+ TN/TM are associated with cognitive status. Because poor immune functioning and increased inflammation are associated with cognitive impairment, improving immune functioning and reducing inflammation may provide a mechanism for reducing ADRD risk in the population.

Seropositivity and reactivations of HSV-1, but not of HSV-2 nor VZV, associate with altered blood–brain barrier, beta amyloid, and tau proteins in people living with HIV

Among 128 adult people living with HIV and no neurological conditions confounding the cerebrospinal fluid results, the presence of HSV-1 chronic infection (detected either by serology or PCR), but not of HSV-2 and VZV, independently associated with higher odds of blood-brain barrier impairment, abnormally increased cerebrospinal fluid levels of tau and phosphorylated-181 tau, and decreased concentrations of fragments 1-42 of beta amyloid compared to the seronegative counterpart. These associations were even stronger for seropositive participants with a positive history of at least one symptomatic reactivation of HSV-1.

Herpes simplex virus and rates of cognitive decline or whole brain atrophy in the Dominantly Inherited Alzheimer Network

OBJECTIVE

To investigate whether herpes simplex virus type 1 (HSV-1) infection was associated with rates of cognitive decline or whole brain atrophy among individuals from the Dominantly Inherited Alzheimer Network (DIAN).

METHODS

Among two subsets of the DIAN cohort (age range 19.6-66.6 years; median follow-up 3.0 years) we examined (i) rate of cognitive decline (N = 164) using change in mini-mental state examination (MMSE) score, (ii) rate of whole brain atrophy (N = 149), derived from serial MR imaging, calculated using the boundary shift integral (BSI) method. HSV-1 antibodies were assayed in baseline sera collected from 2009-2015. Linear mixed-effects models were used to compare outcomes by HSV-1 seropositivity and high HSV-1 IgG titres/IgM status.

RESULTS

There was no association between baseline HSV-1 seropositivity and rates of cognitive decline or whole brain atrophy. Having high HSV-1 IgG titres/IgM was associated with a slightly greater decline in MMSE points per year (difference in slope - 0.365, 95% CI: -0.958 to -0.072), but not with rate of whole brain atrophy. Symptomatic mutation carriers declined fastest on both MMSE and BSI measures, however, this was not influenced by HSV-1. Among asymptomatic mutation carriers, rates of decline on MMSE and BSI were slightly greater among those who were HSV-1 seronegative. Among mutation-negative individuals, no differences were seen by HSV-1. Stratifying by APOE4 status yielded inconsistent results.

INTERPRETATION

We found no evidence for a major role of HSV-1, measured by serum antibodies, in cognitive decline or whole brain atrophy among individuals at high risk of early-onset AD.

Herpes simplex virus 1 infection on grey matter and general intelligence in severe mental illness

Schizophrenia and bipolar disorder are severe mental illnesses (SMI) linked to both genetic and environmental factors. Herpes simplex virus 1 (HSV1) is a common neurotropic pathogen which after the primary infection establishes latency with periodic reactivations. We hypothesized that the latent HSV1 infection is associated with brain structural abnormalities and cognitive impairment, especially in SMI. We included 420 adult patients with SMI (schizophrenia or bipolar spectrum) and 481 healthy controls. Circulating HSV1 immunoglobulin G concentrations were measured with immunoassays. We measured the total grey matter volume (TGMV), cortical, subcortical, cerebellar and regional cortical volumes based on T1-weighted MRI scans processed in FreeSurfer v6.0.0. Intelligence quotient (IQ) was assessed with the Wechsler Abbreviated Scale of Intelligence. Seropositive patients had significantly smaller TGMV than seronegative patients (642 cm³ and 654 cm³, respectively; p = 0.019) and lower IQ (104 and 107, respectively; p = 0.018). No TGMV or IQ differences were found between seropositive and seronegative healthy controls. Post-hoc analysis showed that (a) in both schizophrenia and bipolar spectrum, seropositive patients had similarly smaller TGMV than seronegative patients, whereas the HSV1-IQ association was driven by the schizophrenia spectrum group, and (b) among all patients, seropositivity was associated with smaller total cortical (p = 0.016), but not subcortical or cerebellar grey matter volumes, and with smaller left caudal middle frontal, precentral, lingual, middle temporal and banks of superior temporal sulcus regional cortical grey matter volumes. The results of this cross-sectional study indicate that HSV1 may be an environmental factor associated with brain structural abnormalities and cognitive impairment in SMI.

Cytomegalovirus and Toxoplasma Gondii Serostatus Prospectively Correlated With Problems in Self-Regulation but not Executive Function Among Older Adults

OBJECTIVE

Cytomegalovirus (CMV) and Toxoplasma gondii are organisms that may infect the brain and have cognitive and behavioral consequences. We hypothesized that these latent infections would be prospectively associated with poorer cognition and more problems in self-regulation among older adults.

METHODS

Older adults (n = 138, mean age = 75.5 years, 59% women) had CMV and T. gondii serostatus tested, crystallized intelligence estimated (North American Adult Reading Test), and executive function (EF; e.g., Trail Making Test) and self-regulation (Behavior Regulation Inventory of Executive Function-Adult) assessed in visits occurring every 6 months (mean visits = 16).

RESULTS

CMV+ people (79%) had significantly poorer self-regulation versus CMV- people (21%; behavioral regulation: γ = 0.108, 95% confidence interval [CI] = 0.009-0.206; metacognition: γ = 0.117, 95% CI = 0.005-0.229), but not intelligence or EF. T. gondii+ people (24%) were not significantly different from T. gondii- people (76%) on any outcome. However, T. gondii+ men had better self-regulation versus T. gondii- men, and the opposite was true of women (behavioral regulation interaction: γ = 0.267, 95% CI = 0.093-0.441).

CONCLUSIONS

CMV latent infection was associated with more problems in self-regulation, and the magnitude of this difference was clinically significant. T. gondii latent infection was associated with more problems, but only for women. Latent infection might associate with self-regulation but not EF because of factors influencing self-regulation but not neuropsychological test performance, such as values and emotion. Efforts to link latent infection with EFs might, in the future, include the application of those functions to self-regulation in daily life.

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.

Sociodemographic Differences in Population-Level Immunosenescence in Older Age

Background

The COVID-19 pandemic has highlighted the urgent need to understand variation in immunosenescence at the population-level. Thus far, population patterns of immunosenescence are not well described.

Methods

We characterized measures of immunosenescence from newly released venous blood data from the nationally representative U.S Health and Retirement Study (HRS) of individuals ages 56 years and older.

Findings

Median values of the CD8+:CD4+, EMRA:Nave CD4+ and EMRA:Nave CD8+ ratios were higher among older participants and were lower in those with additional educational attainment. Generally, minoritized race and ethnic groups had immune markers suggestive of a more aged immune profile: Hispanics had a CD8+:CD4+ median value of 0.37 (95% CI: 0.35, 0.39) compared to 0.30 in Whites (95% CI: 0.29, 0.31). Blacks had the highest median value of the EMRA:Nave CD4+ ratio (0.08; 95% CI: 0.07, 0.09) compared to Whites (0.03; 95% CI: 0.028, 0.033). In regression analyses, race/ethnicity and education were associated with large differences in the immune ratio measures after adjustment for age and sex. For example, each additional level of education was associated with roughly an additional decade of immunological age, and the racial/ethnic differences were associated with two to four decades of additional immunological age.

Interpretation

Our study provides novel insights into population variation in immunosenescence. This has implications for both risk of age-related disease and vulnerability to novel pathogens (e.g., SARS-CoV-2).

Funding

This study was partially funded by the U.S. National Institutes of Health, National Institute on Aging R00AG062749. AEA and GAN acknowledge support from the National Institutes of Health, National Institute on Aging R01AG075719. JBD acknowledges support from the Leverhulme Trust (Centre Grant) and the European Research Council grant ERC-2021-CoG-101002587.

Research in context

Evidence before this study: Alterations in immunity with chronological aging have been consistently demonstrated across human populations. Some of the hallmark changes in adaptive immunity associated with aging, termed immunosenescence, include a decrease in nave T-cells, an increase in terminal effector memory cells, and an inverted CD8:CD4 T cell ratio. Several studies have shown that social and psychosocial exposures can alter aspects of immunity and lead to increased susceptibility to infectious diseases.Add value of this study: While chronological age is known to impact immunosenescence, there are no studies examining whether social and demographic factors independently impact immunosenescence. This is important because immunosenescence has been associated with greater susceptibility to disease and lower immune response to vaccination. Identifying social and demographic variability in immunosenescence could help inform risk and surveillance efforts for preventing disease in older age. To our knowledge, we present one of the first large-scale population-based investigations of the social and demographic patterns of immunosenescence among individuals ages 50 and older living in the US. We found differences in the measures of immunosenescence by age, sex, race/ethnicity, and education, though the magnitude of these differences varied across immune measures and sociodemographic subgroup. Those occupying more disadvantaged societal positions (i.e., minoritized race and ethnic groups and individuals with lower educational attainment) experience greater levels of immunosenescence compared to those in less disadvantaged positions. Of note, the magnitude of effect of sociodemographic factors was larger than chronological age for many of the associations.Implications for practice or policy and future research: The COVID-19 pandemic has highlighted the need to better understand variation in adaptive and innate immunity at the population-level. While chronological age has traditionally been thought of as the primary driver of immunological aging, the magnitude of differences we observed by sociodemographic factors suggests an important role for the social environment in the aging human immune system.

Cytomegalovirus is not associated with cognitive function in UK adults aged 40 to 70 years

Infecting much of the world's population, the herpesviridae virus cytomegalovirus has been associated with lower cognitive function in some but not all studies. In this study, we further investigate associations between cytomegalovirus and cognitive function in a community-based sample of adults aged 40 to 70 years (M = 55.3; SD = 8.1) from the United Kingdom. Adjusted multiple-regression modeling showed no significant associations between cytomegalovirus and performance on nine cognitive tasks. Further, in adjusted interaction models, age, sex, educational attainment, and income did not moderate associations between cytomegalovirus and cognitive function. In this community-based adult sample, cytomegalovirus was not associated with cognitive function.

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.

Cognitive Trajectories Following Acute Infection in Older Patients With and Without Cognitive Impairment: An 1-Year Follow-Up Study

Introduction: Dementia is a known risk factor for both delirium and acute systemic infections which may also play a significant role in promoting or accelerating neurodegenerative disease. Infections are both the main causes of hospitalization of dementia patients and can be a major precipitant of delirium but currently it is not possible to predict the risk of cognitive decline in older patients exposed to acute infection. Objectives: We aimed to determine the level of cognitive change at 1-year follow up in individuals with different patterns of cognitive function (dementia, delirium, delirium superimposed on dementia) at the time of their hospitalization due to a systemic infection and to correlate these cognitive patterns with clinical status variables. Methods: We recruited 53 hospitalized geriatric patients with a systemic infection, and we collected 12-months follow up data for 34 patients. These patients were classified in four groups: no cognitive impairment (controls-C), delirium only (D), dementia only (Dem), and delirium superimposed to dementia (DD). Cognitive performance was measured by change in score on the Montreal Cognitive Assessment (MoCA) and delirium was identified using Confusion Assessment Measure (CAM). We examined performance on the MoCA in the first year after hospitalization, controlling for demographic characteristics, coexisting medical conditions, and type of infection. Results: For the 34 patients to whom follow-up data was available, delirium presence in individuals with prior dementia (DD group) was associated with a negative mean change score of 3-point (p < 0.02) at 1 year follow up, whereas dementia patients without delirium had a mean change score of 1.5-point lower at 12-months (p = 0.04), when comparing follow-up and baseline MoCA scores. Cognitively healthy patients did not significantly decrease their MoCA score at follow-up (p = 0.15). MoCA and NPI scores during hospitalization were significantly correlated with the level of cognitive decline in the four groups (r = 0.658, p < 0.01 and r = 0.439, p = 0.02, respectively). Conclusions: Premorbid dementia and delirium superimposed on dementia during hospitalization in older patients with acute infections predict cognitive decline at 1 year following admission. Taken together, our findings suggest a pathophysiological interaction between neurodegenerative changes, acute infection, and delirium.

The Role of Chronic Infection in Alzheimer's Disease: Instigators, Co-conspirators, or Bystanders?

PURPOSE OF REVIEW

Herein, we provide a critical review of the clinical and translational research examining the relationship between viral and bacterial pathogens and Alzheimer's disease. In addition, we provide an overview of the biological pathways through which chronic infection may contribute to Alzheimer's disease.

RECENT FINDINGS

Dementia due to Alzheimer's disease is a leading cause of disability among older adults in developed countries, yet knowledge of the causative factors that promote Alzheimer's disease pathogenesis remains incomplete. Over the past several decades, numerous studies have demonstrated an association of chronic viral and bacterial infection with Alzheimer's disease. Implicated infectious agents include numerous herpesviruses (HSV-1, HHV-6, HHV-7) and various gastric, enteric, and oral bacterial species, as well as Chlamydia pneumonia and multiple spirochetes.

SUMMARY

Evidence supports the association between multiple pathogens and Alzheimer's disease risk. Whether these pathogens play a causal role in Alzheimer's pathophysiology remains an open question. We propose that the host immune response to active or latent infection in the periphery or in the brain triggers or accelerates the Alzheimer's disease processes, including the accumulation of amyloid-ß and pathogenic tau, and neuroinflammation. While recent research suggests that such theories are plausible, additional longitudinal studies linking microorganisms to Aß and phospho-tau development, neuroinflammation, and clinically defined Alzheimer's dementia are needed.

[Seroprevalence and factors associated with chronic infections among community-dwelling elderly individuals]

Chronic infections can contribute to the aging process, but this issue is less studied in Latin America. The aim was to assess the prevalence and factors associated with cytomegalovirus (CMV), Herpes Simplex 1 (HSV-1), Chlamydia pneumoniae and Helicobacter pylori among the elderly. A total of 1,320 individuals participated from the baseline of the Elderly Cohort of Bambuí. IgG antibodies against infections and explanatory variables (sociodemographic factors, health behaviors and health conditions) were evaluated. Poisson regression models with robust variance were used. Seroprevalence rates were 99.4% for CMV, 96.7% for HSV-1, 56% for C. pneumoniae and 70.5% for H. pylori. Elderly men, women, smokers, diabetics, the disabled and those with high levels of IL-6 had a higher prevalence of CMV. HSV-1 was less frequent among women. The prevalence of C. pneumoniae was higher at ages >75 and among diabetics; it was lower among women and individuals with less schooling. H. pylori was less frequent among women and those with detectable levels of IL-1β, but more common among smokers. The findings show a high prevalence of chronic infection and a different epidemiologic profile for each pathogen, making it possible to detect groups that are vulnerable to these infections.

Life Course Socioeconomic Disadvantage and the Aging Immune System: Findings From the Health and Retirement Study

OBJECTIVES

Previous research has documented a consistent association between current socioeconomic status (SES) and cytomegalovirus (CMV). Early life is likely a critical period for CMV exposure and immune development, but less is known about early-life socioeconomic factors and CMV, particularly in older age populations. Using data from the Health and Retirement Study, we investigated the association between life course socioeconomic disadvantage and immune response to CMV among older adults.

METHODS

Using ordered logit models, we estimated associations between several measures of socioeconomic disadvantage and the odds of being in a higher CMV Immunoglobulin G (IgG) response category in a sample of 8,168 respondents aged older than 50 years.

RESULTS

We found a significant association between educational attainment and CMV IgG response. Those with less than a high school education had 2.00 (95% confidence interval [CI]: 1.67-2.40) times the odds of being in a higher CMV category compared to those with a college degree or greater. In addition, we also observed a significant association with parental education and CMV response. Individuals with parents having 8 years or less of schooling had 2.32 (95% CI: 2.00-2.70) times the odds of higher CMV response compared to those whose parents had greater than high school education.

DISCUSSION

CMV IgG levels in older adults are associated with both early-life and adult SES. Life course socioeconomic disadvantage may contribute to disparities in immunological aging.

Cross sectional association between cytomegalovirus seropositivity, inflammation and cognitive impairment in elderly cancer survivors

PURPOSE

The higher prevalence of cognitive impairment/ dementia among cancer survivors is likely multifactorial. Since both exposures to cytomegalovirus (CMV) and inflammation are common among elderly cancer survivors, we evaluated their contribution towards dementia.

METHODS

Data from 1387 cancer survivors and 7004 participants without cancer in the 2016 wave of the Health and Retirement Study (HRS) was used in this study. Two inflammatory biomarkers, C-reactive protein (CRP) and neutrophil-lymphocyte ratio (NLR), were used to create an inflammation score. We used survey logistic regression adjusted for survey design parameters.

RESULTS

CMV seropositivity was not associated with cognitive impairment among cancer survivors (p = 0.2). In addition, inflammation was associated with elevated odds of cognitive impairment (OR = 2.2, 95% CI [1.2, 4.2]). Cancer survivors who were both CMV seropositive and had increased inflammation had the highest odds of cognitive impairment compared to those who were CMV seronegative and had low inflammation (OR = 3.8, 95% CI [1.5, 9.4]). The stratified analysis among cancer survivors showed this association was seen only among cancer survivors in whom the cancer was diagnosed within three years of measurement of inflammation score and CMV serostatus (OR = 18.5; 95% CI [6.1, 56.1]).

CONCLUSION

The CMV seropositivity and high inflammation was associated with higher cognitive impairment among cancer survivors. The stronger associations seen among cancer survivors diagnosed within the last three years suggest that strategies to reduce CMV activation and inflammation during or immediately after cancer treatment may be important in reducing the prevalence of cognitive impairment/ dementia among cancer survivors.

The Hippocampal Vulnerability to Herpes Simplex Virus Type I Infection: Relevance to Alzheimer's Disease and Memory Impairment

Herpes simplex virus type 1 (HSV-1) as a possible infectious etiology in Alzheimer’s disease (AD) has been proposed since the 1980s. The accumulating research thus far continues to support the association and a possible causal role of HSV-1 in the development of AD. HSV-1 has been shown to induce neuropathological and behavioral changes of AD, such as amyloid-beta accumulation, tau hyperphosphorylation, as well as memory and learning impairments in experimental settings. However, a neuroanatomical standpoint of HSV-1 tropism in the brain has not been emphasized in detail. In this review, we propose that the hippocampal vulnerability to HSV-1 infection plays a part in the development of AD and amnestic mild cognitive impairment (aMCI). Henceforth, this review draws on human studies to bridge HSV-1 to hippocampal-related brain disorders, namely AD and aMCI/MCI. Next, experimental models and clinical observations supporting the neurotropism or predilection of HSV-1 to infect the hippocampus are examined. Following this, factors and mechanisms predisposing the hippocampus to HSV-1 infection are discussed. In brief, the hippocampus has high levels of viral cellular receptors, neural stem or progenitor cells (NSCs/NPCs), glucocorticoid receptors (GRs) and amyloid precursor protein (APP) that support HSV-1 infectivity, as well as inadequate antiviral immunity against HSV-1. Currently, the established diseases HSV-1 causes are mucocutaneous lesions and encephalitis; however, this review revises that HSV-1 may also induce and/or contribute to hippocampal-related brain disorders, especially AD and aMCI/MCI.

Association between cytomegalovirus infection, reduced gray matter volume, and resting-state functional hypoconnectivity in major depressive disorder: a replication and extension

Human cytomegalovirus (HCMV) is a neurotropic herpes virus known to cause neuropathology in patients with impaired immunity. Previously, we reported a reduction in the gray matter volume (GMV) of several brain regions in two independent samples of participants who were seropositive for HCMV (HCMV+) compared to matched participants who were seronegative for HCMV (HCMV-). In addition to an independent replication of the GMV findings, this study aimed to examine whether HCMV+ was associated with differences in resting-state functional connectivity (rsfMRI-FC). After balancing on 11 clinical/demographic variables using inverse probability of treatment weighting (IPTW), GMV and rsfMRI-FC were obtained from 99 participants with major depressive disorder (MDD) who were classified into 42 HCMV+ and 57 HCMV- individuals. Relative to the HCMV- group, the HCMV+ group showed a significant reduction of GMV in nine cortical regions. Volume reduction in the right lateral orbitofrontal cortex (standardized beta coefficient (SBC) = -0.32, [95%CI, -0.62 to -0.02]) and the left pars orbitalis (SBC = -0.34, [95%CI, -0.63 to -0.05]) in the HCMV+ group was also observed in the previous study. Regardless of the parcellation method or analytical approach, relative to the HCMV- group, the HCMV+ group showed hypoconnectivity between the hubs of the sensorimotor network (bilateral postcentral gyrus) and the hubs of the salience network (bilateral insula) with effect sizes ranging from SBC = -0.57 to -0.99. These findings support the hypothesis that a positive HCMV serostatus is associated with altered connectivity of regions that are important for stress and affective processing and further supports a possible etiological role of HCMV in depression.

Cytomegalovirus Serostatus and Functional Impairment in Liver Transplant Recipients in the Current Era

BACKGROUND

Whether donor (D+) or recipient (R+) cytomegalovirus (CMV) seropositivity is associated with functional impairment in liver transplant recipients is not known.

METHODS

Patients included adult liver transplant recipients in the Organ Procurement and Transplantation Network database transplanted over a five-year period from 1 January 2014-31 December 2018. Functional status in the database was assessed using Karnofsky performance scale. A logistic regression model that controlled for potential confounders was used to examine the association of CMV serostatus and functional status. Variables significantly associated with functional status (p < 0.05) were then used to develop propensity score and propensity score matched analysis was conducted where each patient was compared with a matched-control with the same propensity score.

RESULTS

Among 30,267 adult liver transplant recipients, D+ or R+ patients had significantly lower functional status at last follow-up than the D-R- cohort (OR 0.88, 95% CI 0.80-0.96, p = 0.007). In propensity score matched model, D+ or R+ patients had significantly lower functional status than matched-controls (p = 0.009). D+ or R+ CMV serostatus (p = 0.018) and low functional level (p < 0.001) were also independently associated with infections as cause-of-death.

CONCLUSIONS

D+ or R+ liver transplant recipients had lower functional status and higher risk of deaths due to infections. Future studies are warranted to examine the mechanistic basis of these findings in the setting of transplantation.

Cytomegalovirus infection and IQ in patients with severe mental illness and healthy individuals

Cytomegalovirus (CMV) infection in immunocompetent adults is usually asymptomatic, but results in lifelong latency. Infection occurring congenitally or in immunodeficiency can lead to cognitive impairment. We aimed to investigate the associations between CMV exposure and intelligence quotient (IQ) in patients with schizophrenia spectrum disorders (SZS), bipolar spectrum disorders (BDS) and healthy controls (HC). CMV immunoglobulin G antibody concentrations were measured by immunoassay and expressed as dichotomous measures (seropositive/CMV+ vs. seronegative/CMV-). Based on a significant CMV-by-diagnosis-by-sex interaction on IQ, we investigated main and interaction effects of CMV and sex on IQ in each diagnostic category. Significant CMV-by-sex interactions were found in patient groups. In SZS, CMV+ female patients (n = 50) had significantly lower IQ than CMV- female patients (n = 33), whereas CMV+ (n = 48) and CMV- (n = 45) male patients did not differ in IQ. In BDS, CMV+ (n = 49) and CMV- (n = 37) female patients did not differ in IQ, whereas CMV+ male patients (n = 33) had significantly higher IQ than CMV- male patients (n = 32). Among HC, CMV+ (n = 138) and CMV- (n = 118) male participants as well as CMV+ (n = 125) and CMV- (n = 93) female participants did not differ in IQ. Our findings suggest that CMV exposure may affect IQ in patients with severe mental illness but not HC.

Association Between Immune Response to Cytomegalovirus and Cognition in the Health and Retirement Study

Chronic infections and the subsequent immune response have recently been shown to be risk factors for cognitive decline and Alzheimer disease and related dementias (ADRD). While some studies have shown an association between cytomegalovirus (CMV), a chronic and highly prevalent infection, and cognition and/or ADRD, these studies have been limited by nonrepresentative and small samples. Using 2016 data on 5,617 adults aged 65 years or more from the Health and Retirement Study, we investigated the cross-sectional associations of both CMV serostatus and immunoglobulin G (IgG) antibody response with cognitive function using linear regression models adjusting for age, sex, race/ethnicity, and educational attainment. We further investigated potential effect-measure modification by educational attainment. Overall, both CMV seropositivity and higher IgG antibody response were associated with lower cognitive function, though the relationship was not statistically significant in adjusted models. Among participants with less than a high school diploma, CMV seropositivity and being in the first tertile of IgG response, relative to seronegative persons, were associated with lower scores on the Telephone Interview for Cognitive Status (-0.56 points (95% confidence interval: -1.63, 0.52) and -0.89 points (95% confidence interval: -2.07, 0.29), respectively), and the relationship was attenuated among those with higher education. Our results suggest that CMV may be a risk factor for cognitive impairment, particularly among persons with fewer educational resources.

Herpes simplex virus 1 and the risk of dementia: a population-based study

Herpes simplex virus 1 (HSV1) is a neuroinvasive virus capable of entering the brain which makes it a candidate pathogen for increasing risk of dementia. Previous studies are inconsistent in their findings regarding the link between HSV1 and dementia, therefore, we investigated how HSV1 relates to cognitive decline and dementia risk using data from a population-based study. We measured HSV1 immunoglobulin (IgG) antibodies in serum collected between 2002 and 2005 from participants of the Rotterdam Study. We used linear regression to determine HSV1 in relation to change in cognitive performance during 2 consecutive examination rounds on average 6.5 years apart. Next, we determined the association of HSV1 with risk of dementia (until 2016) using a Cox regression model. We repeated analyses for Alzheimer’s disease. All models were adjusted for age, sex, cardiovascular risk factors, and apolipoprotein E genotype. Of 1915 non-demented participants (mean age 71.3 years, 56.7% women), with an average follow-up time of 9.1 years, 244 participants developed dementia (of whom 203 Alzheimer’s disease). HSV1 seropositivity was associated with decline in global cognition (mean difference of HSV1 seropositive vs seronegative per standard deviation decrease in global cognition − 0.16; 95% confidence interval (95%CI), − 0.26; − 0.07), as well as separate cognitive domains, namely memory, information processing, and executive function, but not motor function. Finally, HSV1 seropositivity was not associated with risk of dementia (adjusted hazard ratio 1.18, 95% CI 0.83; 1.68), similar for Alzheimer’s disease. HSV1 is associated with cognitive decline but not with incident dementia in the general population. These data suggest HSV1 to be associated only with subtle cognitive disturbances but not with greater cognitive disorders that result in dementia.

Pathogen Burden, Blood Biomarkers and Functional Ageing in Community-Dwelling Older Adults

BACKGROUND

Lifelong accumulation of latent or persistent or repeated infections may be a contributing factor to the deterioration of physical and cognitive function associated with functional ageing, but the evidence is limited and the biological underpinnings are unclear.

METHODS

We profiled the seropositivity for common viral, bacterial and plasmodial pathogens of local importance in community-living older adults in two studies involving 745 older adults (mean age 67.0, SD: 7.7 years), and 142 older adults (mean age 72.7, SD: 8.3 years). Pathogen load was related to different sets of age-related physical and cognitive measures of functional ageing and the frailty index, and plasma levels of biomarkers of inflammation, innate and adaptive immunity, and other physiological functions.

RESULTS

High pathogen load was associated with impaired gait speed (GS), (p<0.015), functional mobility (POMA) (p<0.029), cognitive function (MMSE) (p<<0.05), and increased frailty index (FI) (p<<0.05). High pathogen load was significantly associated with C3a complement activity (p<0.001), matrix metalloproteinase-7, macrophage inflammatory protein-1α (p<0.05), and monocyte chemoattractant protein 2 (p=0.028). Blood biomarkers did not fully explain the observed association between pathogen load and functional ageing measures.

CONCLUSIONS

The present study provides novel evidence linking lifelong cumulated numbers of latent, persistent or repeated infection to functional ageing, plausibly via inflammatory and immune and other biological factors.

Viral infections and their relationship to neurological disorders

The chronic dysfunction of neuronal cells, both central and peripheral, a characteristic of neurological disorders, may be caused by irreversible damage and cell death. In 2016, more than 276 million cases of neurological disorders were reported worldwide. Moreover, neurological disorders are the second leading cause of death. Generally, the etiology of neurological diseases is not fully understood. Recent studies have related the onset of neurological disorders to viral infections, which may cause neurological symptoms or lead to immune responses that trigger these pathological signs. Currently, this relationship is mostly based on epidemiological data on infections and seroprevalence of patients who present with neurological disorders. The number of studies aiming to elucidate the mechanism of action by which viral infections may directly or indirectly contribute to the development of neurological disorders has been increasing over the years but these studies are still scarce. Comprehending the pathogenesis of these diseases and exploring novel theories may favor the development of new strategies for diagnosis and therapy in the future. Therefore, the objective of the present study was to review the main pieces of evidence for the relationship between viral infection and neurological disorders such as Alzheimer's disease, Parkinson's disease, Guillain-Barré syndrome, multiple sclerosis, and epilepsy. Viruses belonging to the families Herpesviridae, Orthomyxoviridae, Flaviviridae, and Retroviridae have been reported to be involved in one or more of these conditions. Also, neurological symptoms and the future impact of infection with SARS-CoV-2, a member of the family Coronaviridae that is responsible for the COVID-19 pandemic that started in late 2019, are reported and discussed.

Cytomegalovirus antibody levels and mortality among hospitalised elderly patients

BACKGROUND

The impact of cytomegalovirus infection in elderly subjects remains unclear. This study examined the relationship between humoral immune response to cytomegalovirus (CMV) and all-cause mortality in a cohort of elderly hospitalised patients.

METHODS

Data were obtained from a random sample of 715 patients (≥65 years old) admitted for any cause in a third level hospital. Serum IgG antibody against CMV was determined by enzyme-linked immunosorbent (ELISA) assay.

RESULTS

A total of 480 deaths occurred in seropositive patients (n = 671) during a follow-up of 7.6 years (mean, 4.6); of which 112 patients died in-hospital or within 30 days after discharge (short-term mortality). For patients with CMV IgG antibody levels in the highest quartile compared with lower quartile, fully adjusted models showed that mortality was 1.40 times (95% CI 1.05-1.86) and 2.20 times (95% CI 1.15-4.21) higher, respectively. The exclusion of patients with cardiovascular disease (angina, myocardial infarction, heart failure, peripheral artery disease, or stroke) increases the risk of long-term (HR 2.22, 95% CI 1.36-3.62) and short-term mortality (OR 3.18, 95% CI 1.40-7.24).

CONCLUSIONS

Increased IgG antibody levels against CMV are associated with increased short and long-term mortality in elderly hospitalised patients, especially in patients without cardiovascular disease. Key Messages The outcome of elderly hospitalised patients in relation to CMV is unknown. We demonstrate an association between increased anti-CMV IgG levels and mortality. This association is greater in elderly patients without cardiovascular disease.

Neurocognitive functioning in long-term survivors of pediatric hematopoietic cell transplantation

Survivors of pediatric hematopoietic cell transplantation (HCT) are at risk for impairment in cognitive and academic function. Most research to date has focused on the first years following transplant, and less is known about the long-term effects. We examined global and specific neurocognitive functioning in long-term (>5 years post HCT) survivors in comparison to both normative data and a sample of demographically similar healthy peers. A comprehensive battery of neurocognitive measures was obtained from 83 long-term survivors and 50 healthy comparisons. Analyses were conducted to assess for differences in neurocognitive functions between survivors, normative means, and healthy comparisons, and to examine the impact of medical and demographic variables on neurocognitive performance. Survivors' performance was within the Average range across most measures, although significantly lower than both test norms and healthy comparisons on several measures. Despite generally intact neurocognitive functioning in the survivor group as a whole, survivors who experienced graft-vs.-host disease demonstrated slower processing speed and weaker verbal learning. Use of total body irradiation was not associated with any performance-based measure of neurocognitive functioning. Although subgroups of patients may be at relatively higher risk of neurocognitive impairment, the long-term neurocognitive impact for most survivors is relatively small.

KIR2DS2/KIR2DL2/HLA-C1 Haplotype Is Associated with Alzheimer's Disease: Implication for the Role of Herpesvirus Infections

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, where neuroinflammation and immune cells are key pathological factors. Recently, it was suggested a possible association between AD and human herpesvirus 6 (HHV-6) infection. Since we recently observed that multiple sclerosis patients with KIR2DL2 expression on natural killer (NK) cells are more susceptible to herpesvirus infection, we tested the possible implication of KIR/HLA genetic for HHV-6A infection. We identified, for the first time, a possible implication of a specific KIR/HLA subset in AD. The combination KIR2DS2/KIR2DL2/C1 correlated with a lower MMSEDi score, representative of a severe AD status and an increased susceptibility to HHV-6A infection. Therefore, the results seem to converge on the hypothesis that herpesvirus infection might play a role in AD. If this hypothesis finds experimental confirmation, a new therapeutic strategy, modulating KIR2DL2 expression on NK cells, for AD might be envisaged.

Multiple Causes of Dementia as Engineered Senescence

All traumas—cranial, cardiovascular, hormone, viral, bacterial, fungi, parasites, misfolded protein, genetic, behavior, environmental and medication—affect the brain. This paper itemizes studies showing the many different causes of dementia including Alzheimer’s disease. Causes interact with each other, act sequentially by preparing the optimal conditions for its successor, initiate other diseases, allow for other traumas to accumulate and degrade protective features of the brain. Since such age-related cognitive impairment is not exclusively a human attribute there might be support for an evolutionary theory of dementia. Relying on theories of antagonistic pleiotropy and polymorphism, the brain has been designed to sequester trauma. Because of increased longevity, the short-term tactic of sequestering trauma becomes a long-term liability. We are engineered to sequester these insults until a tipping point is reached. Dementia is an evolutionary trade-off for longevity. We cannot cure dementia without understanding the overall biology of aging.

Infectious agents as a risk factor for Alzheimer’s disease

Cognitive disorders are one of the relevant problems of modern clinical medicine. This is due to both their high frequency of occurrence and significant negative impact, which has a violation of higher cortical functions on the quality of life of patients due to the deterioration of their social communication, as well as reducing the effectiveness of professional and household functions. The main cause of cognitive disorders is Alzheimer’s disease. At the same time, according to statistical studies, a significant increase in the incidence of the number of persons in the human population as a whole suffering from this pathology is predicted. At the heart of Alzheimer’s disease is a complex of pathobiochemical changes leading to synaptic dysfunction, accompanied by the development of atrophic changes in certain areas of the brain, against which a specific clinical picture is formed. The earliest and most important manifestation of Alzheimer’s disease is memory impairment for current events, which are subsequently joined by a number of other symptoms. The literature describes certain risk factors that contribute to the development of the disease, among which a certain place is occupied by infectious pathology. However, this aspect remains largely outside the traditional study of the pathogenesis of Alzheimer’s disease. In the review the analysis of the results of modern studies confirm the possible involvement of infections in the development of dementia of Alzheimer’s type.

Herpes Simplex Virus Type-1 Infection: Associations with Inflammation and Cognitive Aging in Relation to Schizophrenia

Most persons experience cognitive decline as they grow older. The term "cognitive aging," coined to describe milder varieties of cognitive decline, is likely to be due to multiple causes. Persistent or repeated infections of the central nervous system (whether subclinical or diagnosable) can cause damage to neurons directly or indirectly through inflammation resulting in incremental neuronal damage, thus eroding cognitive reserve. This possibility has not been considered widely. We evaluated the data linking persistent infection with herpes simplex virus type 1 (HSV-1) and cognitive aging by applying the Bradford Hill criteria. Despite inherent problems in establishing causal relations for chronic disorders, our analyses suggest plausible links. These studies are pertinent for patients with schizophrenia, who are particularly vulnerable due to disorder-related cognitive impairment. Further investigations are warranted to test a causal hypothesis, particularly prospective studies and intervention studies.

Cytomegalovirus-Specific CD4+ T-cell Responses and CMV-IgG Levels Are Associated With Neurocognitive Impairment in People Living With HIV

BACKGROUND

Mechanisms leading to neurocognitive impairment (NCI) in people living with HIV (PLWHIV) on stable combination antiretroviral therapy (cART) remain unknown. We investigated the association between immunity against cytomegalovirus (CMV), HIV-specific variables, and NCI in PLWHIV on stable cART and with low comorbidity.

METHODS

Fifty-two PLWHIV on stable cART and 31 HIV-uninfected controls matched on age, sex, education, and comorbidity were tested with a neurocognitive test battery, and CMV-immunoglobulin G (CMV-IgG) levels were measured. In PLWHIV, CMV-specific (CMV-pp65 and CMV-gB) CD4 and CD8 T-cell responses were measured using intracellular cytokine staining and flow cytometry. NCI was defined as a global deficit scale score (GDS score) ≥0.5. GDS scores and domain-specific scores defined severity of NCI. Logistic and linear multivariable regression analyses were used.

RESULTS

NCI was detected in 30.8% of PLWHIV, and HIV was associated with an adjusted odds ratio (aOR) of 5.18 [95% confidence interval (CI): 1.15 to 23.41, P = 0.033] for NCI. In PLWHIV, higher CMV-specific CD4 T-cell responses increased the probability of NCI with an aOR of 1.68 (95% CI: 1.10 to 2.57) for CMV-pp65 or an aOR of 3.73 (95% CI: 1.61 to 16.98) for CMV-gB, respectively. Similar associations were not found with CMV-IgG or CMV-specific CD8 T cells, but when assessing severity of NCI, higher CMV-IgG (per 100 U/mL) was associated with worse GDS scores (β = 0.08) (0.01-0.16), P = 0.044), specifically in the domain of speed of information processing (β = 0.20 (0.04-0.36, P = 0.019).

CONCLUSIONS

PLWHIV had increased risk of NCI. Excess risk may be associated with CMV-specific CD4 T-cell responses and CMV-IgG. Larger longitudinal studies investigating the impact of immunity against CMV on risk of NCI are warranted.