Latent Herpes Simplex Virus Type 1 Research Articles

A dual fluorescent herpes simplex virus type 1 recombinant reveals divergent outcomes of neuronal infection.

Critical stages of lytic herpes simplex virus type 1 (HSV-1) replication are marked by the sequential expression of immediate early (IE) to early (E), then late (L) viral genes. HSV-1 can also persist in neuronal cells via a non-replicative, transcriptionally repressed infection called latency. The regulation of lytic and latent transcriptional profiles is critical to HSV-1 pathogenesis and persistence. We sought a fluorescence-based approach to observe the outcome of neuronal HSV-1 infection at the single-cell level. To achieve this goal, we constructed and characterized a novel HSV-1 recombinant that enables discrimination between lytic and latent infection. The dual reporter HSV-1 encodes a human cytomegalovirus-immediate early (hCMV-IE) promoter-driven enhanced yellow fluorescent protein (eYFP) to visualize the establishment of infection and an endogenous mCherry-VP26 fusion to report lytic replication. We confirmed that viral gene expression, replication, and spread of infection are not altered by the incorporation of the fluorescent reporters, and fluorescent protein (FP) detection virtuously reports the progression of lytic replication. We demonstrate that the outcome of HSV-1 infection of compartmentalized primary neurons is determined by viral inoculating dose: high-dose axonal inoculation proceeds to lytic replication, whereas low-dose axonal inoculation establishes a latent HSV-1 infection. Interfering with low-dose axonal inoculation via small molecule drugs reports divergent phenotypes of eYFP and mCherry reporter detection, correlating with altered states of viral gene expression. We report that the transcriptional state of neuronal HSV-1 infection is variable in response to changes in the intracellular neuronal environment.IMPORTANCEHerpes simplex virus type 1 (HSV-1) is a prevalent human pathogen that infects approximately 67% of the global human population. HSV-1 invades the peripheral nervous system, where latent HSV-1 infection persists within the host for life. Immunological evasion, viral persistence, and herpetic pathologies are determined by the regulation of HSV-1 gene expression. Studying HSV-1 gene expression during neuronal infection is challenging but essential for the development of antiviral therapeutics and interventions. We used a recombinant HSV-1 to evaluate viral gene expression during infection of primary neurons. Manipulation of cell signaling pathways impacts the establishment and transcriptional state of HSV-1 latency in neurons. The work here provides critical insight into the cellular and viral factors contributing to the establishment of latent HSV-1 infection.

Reanalysis of single-cell RNA sequencing data does not support herpes simplex virus 1 latency in non-neuronal ganglionic cells in mice.

Most individuals are latently infected with herpes simplex virus type 1 (HSV-1), and it is well-established that HSV-1 establishes latency in sensory neurons of peripheral ganglia. However, it was recently proposed that latent HSV-1 is also present in immune cells recovered from the ganglia of experimentally infected mice. Here, we reanalyzed the single-cell RNA sequencing (scRNA-Seq) data that formed the basis for that conclusion. Unexpectedly, off-target priming in 3' scRNA-Seq experiments enabled the detection of non-polyadenylated HSV-1 latency-associated transcript (LAT) intronic RNAs. However, LAT reads were near-exclusively detected in mixed populations of cells undergoing cell death. Specific loss of HSV-1 LAT and neuronal transcripts during quality control filtering indicated widespread destruction of neurons, supporting the presence of contaminating cell-free RNA in other cells following tissue processing. In conclusion, the reported detection of latent HSV-1 in non-neuronal cells is best explained using compromised scRNA-Seq datasets.IMPORTANCEMost people are infected with herpes simplex virus type 1 (HSV-1) during their life. Once infected, the virus generally remains in a latent (silent) state, hiding within the neurons of peripheral ganglia. Periodic reactivation (reawakening) of the virus may cause fresh diseases such as cold sores. A recent study using single-cell RNA sequencing (scRNA-Seq) proposed that HSV-1 can also establish latency in the immune cells of mice, challenging existing dogma. We reanalyzed the data from that study and identified several flaws in the methodologies and analyses performed that invalidate the published conclusions. Specifically, we showed that the methodologies used resulted in widespread destruction of neurons which resulted in the presence of contaminants that confound the data analysis. We thus conclude that there remains little to no evidence for HSV-1 latency in immune cells.

Seroprevalence of VZV and HSV-2 Antibodies among Women of Childbearing Age Referring to Health Centres of Mashhad, Iran: The Need for Consideration of VZV Vaccination Program.

Infections with herpes simplex virus type 2 (HSV-2) and varicella-zoster virus (VZV) are associated with serious maternal and neonatal health consequences. The literature review reveals a research gap regarding the seroprevalence of HSV-2 and VZV among women of reproductive age in Mashhad, Northeast of Iran. The present study aims to evaluate the seroprevalence of these viruses among a group of women in Mashhad, Iran. Sera were collected by health center personnel using a cluster sampling method from healthy women with specific age characteristics residing in three distinct socioeconomic regions of the city. The participants, aged 20-35, were divided into three groups (20-25, 26-30, and 31-35 years). The levels of VZV and HSV-2 IgG antibodies were evaluated using commercial ELISA kits. Subsequently, the results were analyzed using SPSS software. A total of 93 women were included in the study. Anti-HSV-2 IgG antibody was detected in 3 out of 93 participants (7.5%), while anti-VZV IgG antibody was found positive in 80 out of 93 individuals (83.3%). The HSV-2 positive cases were concurrently positive for the VZV antibody. There was no significant difference in the positivity of anti-HSV-2 and anti-VZV antibody positivity within age groups or socioeconomic status (P > 0.05). The high seroprevalence of VZV among nonvaccinated participants indicates a widespread presence of the virus and underscores its potentially serious impact on community health. Therefore, it is recommended that a VZV vaccination program be considered by the health system. Furthermore, the reactivation of latent HSV-2, whether symptomatic or asymptomatic, during pregnancy should not be disregarded as a life-threatening threat.

Varicella-zoster virus proteome-wide T-cell screening demonstrates low prevalence of virus-specific CD8 T-cells in latently infected human trigeminal ganglia

BackgroundTrigeminal ganglia (TG) neurons are an important site of lifelong latent varicella-zoster virus (VZV) infection. Although VZV-specific T-cells are considered pivotal to control virus reactivation, their protective role at the site of latency remains uncharacterized.MethodsPaired blood and TG specimens were obtained from ten latent VZV-infected adults, of which nine were co-infected with herpes simplex virus type 1 (HSV-1). Short-term TG-derived T-cell lines (TG-TCL), generated by mitogenic stimulation of TG-derived T-cells, were probed for HSV-1- and VZV-specific T-cells using flow cytometry. We also performed VZV proteome-wide screening of TG-TCL to determine the fine antigenic specificity of VZV reactive T-cells. Finally, the relationship between T-cells and latent HSV-1 and VZV infections in TG was analyzed by reverse transcription quantitative PCR (RT-qPCR) and in situ analysis for T-cell proteins and latent viral transcripts.ResultsVZV proteome-wide analysis of ten TG-TCL identified two VZV antigens recognized by CD8 T-cells in two separate subjects. The first was an HSV-1/VZV cross-reactive CD8 T-cell epitope, whereas the second TG harbored CD8 T-cells reactive with VZV specifically and not the homologous peptide in HSV-1. In silico analysis showed that HSV-1/VZV cross reactivity of TG-derived CD8 T-cells reactive with ten previously identified HSV-1 epitopes was unlikely, suggesting that HSV-1/VZV cross-reactive T-cells are not a common feature in dually infected TG. Finally, no association was detected between T-cell infiltration and VZV latency transcript abundance in TG by RT-qPCR or in situ analyses.ConclusionsThe low presence of VZV- compared to HSV-1-specific CD8 T-cells in human TG suggests that VZV reactive CD8 T-cells play a limited role in maintaining VZV latency.

COVID-19 and Alzheimer's Disease: What Is the Connection?

Wang et al. found that elderly COVID-19 patients were at risk of AD. The following facts suggest a possible explanation: reactivation of herpes simplex virus type 1 (HSV1) and other herpesviruses can occur in SARS-CoV-2 patients; in cell cultures, HSV1 infection causes occurrence of many AD-like features, as does reactivation of latent HSV1 after addition of certain infectious agents; recurrent experimental reactivation of HSV1-infected mice leads to formation of the main features of AD brains, and to cognitive decline. These suggest that COVID-19 results in repeated reactivation of HSV1 in brain, with subsequent accumulation of damage and eventual development of AD.

Latent herpes simplex virus type 1 reactivation increases the susceptibility of neurodegenerative diseases: intervention with traditional Chinese medicine

Owing to environmental and lifestyle changes in modern society, physical and mental stress is on the rise among the population in attempting to compensate for the changes. Stress, defined as a series of non-specific responses to abnormal internal and external stimuli, has long been recognized to increase susceptibility to various diseases, including neurodegenerative diseases (NDs). Herpes simplex virus type 1 (HSV-1), a neurotropic herpes virus, establishes latent infections in the trigeminal ganglia for the lifetime of the host. Upon reactivation, the latent HSV-1 enters the lytic cycle, which not only causes a substantial production of reactive oxygen species (ROS) in the neurons, but also induces glial cells to produce inflammatory mediators, eventually resulting in neuronal damage and occurrence of NDs. Remarkably, both physical and psychological stress are common stimuli leading to latent HSV-1 reactivation. Acyclovir is a classic antiviral drug for the treatment of HSV-1 infection and recurrence, but acyclovir cannot reverse neuronal damage caused by HSV-1 reactivation. Recent studies have shown that traditional Chinese medicine (TCM) has advantages in the treatment of NDs. In addition, TCM is thought to prevent latent HSV-1 reactivation and NDs, which may involve regulation of the neuro-endocrine-immune network, treatment of emotional disorders, and modulation of oxidative stress. Understanding the mechanism underlying stress-induced reactivation of latent HSV-1 and the potential consequences of NDs is needed. TCM may be a promising alternative therapy for related diseases.

T-cells in human trigeminal ganglia express canonical tissue-resident memory T-cell markers

BackgroundTrigeminal ganglia (TG) neurons are the main site of lifelong latent herpes simplex virus type 1 (HSV-1) infection. T-cells in ganglia contribute to long-term control of latent HSV-1 infection, but it is unclear whether these cells are bona fide tissue-resident memory T-cells (TRM). We optimized the processing of human post-mortem nervous tissue to accurately phenotype T-cells in human TG ex vivo and in situ.MethodsPeripheral blood mononuclear cells (PBMC; 5 blood donors) were incubated with several commercial tissue digestion enzyme preparations to determine off-target effect on simultaneous detection of 15 specific T-cell subset markers by flow cytometry. Next, optimized enzymatic digestion was applied to ex vivo phenotype T-cells in paired PBMC, normal appearing white matter (NAWM) and TG of 8 deceased brain donors obtained < 9 h post-mortem by flow cytometry. Finally, the phenotypic and functional markers, and spatial orientation of T-cells in relation to neuronal somata, were determined in TG tissue sections of five HSV-1-latently infected individuals by multiparametric in situ analysis.ResultsCollagenase IV digestion of human nervous tissue was most optimal to obtain high numbers of viable T-cells without disrupting marker surface expression. Compared to blood, majority T-cells in paired NAWM and TG were effector memory T-cells expressing the canonical TRM markers CD69, CXCR6 and the immune checkpoint marker PD1, and about half co-expressed CD103. A trend of relatively higher TRM frequencies were detected in TG of latently HSV-1-infected compared to HSV-1 naïve individuals. Subsequent in situ analysis of latently HSV-1-infected TG showed the presence of cytotoxic T-cells (TIA-1+), which occasionally showed features of proliferation (KI-67+) and activation (CD137+), but without signs of degranulation (CD107a+) nor damage (TUNEL+) of TG cells. Whereas majority T-cells expressed PD-1, traits of T-cell senescence (p16INK4a+) were not detected.ConclusionsThe human TG represents an immunocompetent environment in which both CD4 and CD8 TRM are established and retained. Based on our study insights, we advocate for TRM-targeted vaccine strategies to bolster local HSV-1-specific T-cell immunity, not only at the site of recurrent infection but also at the site of HSV-1 latency.

Sensory Nerve Retraction and Sympathetic Nerve Innervation Contribute to Immunopathology of Murine Recurrent Herpes Stromal Keratitis.

PurposeHerpes stromal keratitis (HSK) represents a spectrum of pathologies which is caused by herpes simplex virus type 1 (HSV-1) infection and is considered a leading cause of infectious blindness. HSV-1 infects corneal sensory nerves and establishes latency in the trigeminal ganglion (TG). Recently, retraction of sensory nerves and replacement with “unsensing” sympathetic nerves was identified as a critical contributor of HSK in a mouse model where corneal pathology is caused by primary infection. This resulted in the loss of blink reflex, corneal desiccation, and exacerbation of inflammation leading to corneal opacity. Despite this, it was unclear whether inflammation associated with viral reactivation was sufficient to initiate this cascade of events.MethodsWe examined viral reactivation and corneal pathology in a mouse model with recurrent HSK by infecting the cornea with HSV-1 (McKrae) and transferring (intravenous [IV]) human sera to establish primary infection without discernible disease and then exposed the cornea to UV-B light to induce viral reactivation.ResultsUV-B light induced viral reactivation from latency in 100% of mice as measured by HSV-1 antigen deposition in the cornea. Further, unlike conventional HSK models, viral reactivation resulted in focal retraction of sensory nerves and corneal opacity. Dependent on CD4+ T cells, inflammation foci were innervated by sympathetic nerves.ConclusionsCollectively, our data reveal that sectoral corneal sensory nerve retraction and replacement of sympathetic nerves were involved in the progressive pathology that is dependent on CD4+ T cells after viral reactivation from HSV-1 latency in the UV-B induced recurrent HSK mouse model.

HSV-1-Specific IgG3 Titers Correlate with Brain Cortical Thinning in Individuals with Mild Cognitive Impairment and Alzheimer's Disease.

Repeated reactivations of latent herpes simplex virus type-1 (HSV-1) in the central nervous system (CNS) may contribute to neurodegeneration in Alzheimer’s disease (AD) patients. Immune response is a key element for the control of viral reactivation. HSV-1 uses a number of strategies to evade immune recognition, Immunoglobulin G 3 (IgG3) alone counteracts humoral immunoevasion, as it is the only IgG subclass that is not blocked by the HSV-1 Fc receptor, a protein that protects virion and infected cells from antibody-mediated effector mechanisms. We examined HSV-1-specific IgG3 titers in serum of AD (n = 70) and mild cognitive impairment (MCI) (n = 61) subjects comparing the results to those of 67 age- and sex-matched healthy controls (HC); associations between MRI-determined brain cortical health and HSV-1-specific IgG3 were analyzed in a subgroup of AD and MCI subjects. HSV-1-specific IgG3 were more frequently detected in MCI compared to AD and HC subjects. Significant inverse correlations were found between IgG3 titers and brain cortical thickness in areas typically involved in dementia and HSV-1 encephalitis in AD patients; interestingly, this negative correlation was much less important in MCI subjects. All together these results suggest that in AD an inefficient IgG3 humoral immune response, failing to block viral replication, contributes to progressive neurodegeneration.

Seroprevalence of Herpes Simplex Virus Type 2 and HIV Co-Infection Among Pregnant Women in Jigawa State

Herpes simplex virus type 2 (HSV-2) infections is one of the most common sexually transmitted infections Worldwide. It facilitates the acquisition of HIV and is the primary cause of genital herpes which when acquired by women during pregnancy account for half of the mobidity and mortality among neonates. Lifelong latent HSV-2 infection raises concern among women of reproductive age considering the risk of neonatal transmission. In Nigeria screening for HSV-2 and co-infection with HIV in antenatal clinics is not routinely done. A cross-sectional study, was carried out among pregnant women attending antenatal clinics in four hospitals in Jigawa state. A total of 300 consenting pregnant women were enrolled, the study involved collection of sociodemographic data and laboratory determination of HSV-2 immunoglobulin G (IgG) and HIV seroprevalence using WHO standard procedure of Enzyme Linked Immunosorbent Assay (ELISA) test kit (DIAPRO Diagnostic Bioprobes, Milano, Italy), UNI-GOLD Wicklow, Ireland and ALERE Determine, respectively. Statistical significance was determined at p<0.05Of the 300 samples tested, overall seroprevalence of 55 (18.3%) and 44 (14.7%) for HSV-2 and HIV were recorded. The HSV-2 and HIV Co-infection rate was 16 (5.3%) among respondent. About 87.5% of the co-infection occurred in respondents that were in their 2^nd Trimester. Addionally, co-infection was found to be high among respondents between the age of 15-34yrs with 81.3%. In this study, education status, parity, stage of pregnancy, occupation, History of blood transfusion had no statistical significance with HSV-2 and HIV co-infection (p>0.05). This study has demonstrated the existence and risk of neonatal herpes in the study area. It is recommended that HSV testing should be placed among the standard medical checkup tests in the area, again advocacy and public awareness on the potential public health burden of HSV-2 and HIV co-infection should be observed.

Using Primary SCG Neuron Cultures to Study Molecular Determinants of HSV-1 Latency and Reactivation.

We describe a primary neuronal culture system suitable for molecular characterization of herpes simplex virus type 1 (HSV-1) infection, latency, and reactivation. While several alternative models are available, including infections of live animal or explanted ganglia, these are complicated by the presence of multiple cell types, including immune cells, and difficulties in manipulating the neuronal environment. The highly pure neuron culture system described here can be readily manipulated and is ideal for molecular studies that focus exclusively on the relationship between the virus and host neuron, the fundamental unit of latency. As such this model allows for detailed investigations of both viral and neuronal factors involved in the establishment and maintenance of HSV-1 latency and in viral reactivation induced by defined stimuli.

Is Alzheimer's disease linked to Herpes simplex virus type 1 infection? A mini‐review of the molecular correlation and the possible disease connections

AbstractAlzheimer's disease (AD) is the most common neurodegenerative disease in the world. Several pathological pathways and genetic alterations have been linked to AD; however, the definitive cause of the disease remains unknown. Recently, an increasing body of evidence suggests that neurodegenerative diseases, including AD, might be triggered by microbial infections. Herpes simplex virus type 1 (HSV1) has been found in brain samples from dead AD patients. At some point of in their lifetime, every person comes into contact with HSV1, but when this enters the brain, it remains latent. However, it was observed that when a person becomes old, and there is a decline in their immunity, the latent HSV1 virus becomes reactivated. The reactivated virus then causes damage to the neural cell DNA and disrupts the DNA repair system, leading to AD. The present review would provide a clear understanding of how HSV1 influences DNA damage, and causes plaque formation and phosphorylation of tau protein, which in turn leads to AD, by inducing the production of interferons that would facilitate the production of specific humoral immunity, which could lead to neurodegeneration.

Co-infection of Herpes Simplex Virus Type 2 and HIV Infections among Pregnant Women in Ibadan, Nigeria.

Introduction:Genital infection with herpes simplex virus type 2 (HSV-2) facilitates the acquisition of HIV, both mutually reinforcing infection. Lifelong latent HSV-2 infection raises concerns among women of reproductive age, considering the risk of neonatal transmission. In Nigeria, screening for HSV-2 and co-infection with HIV in antenatal clinics is not routine. This study was undertaken to determine the seroprevalence and co-infection of HSV-2 and HIV among pregnant women.Methods:This was a cross-sectional study conducted at the antenatal clinic of the University College Hospital, Ibadan, between March and August 2013. A total of 270 consenting pregnant women were enrolled. The study involved collecting socio-demographic data and laboratory determination of HSV-2 immunoglobulin G (IgG) and HIV seroprevalence using type-specific third-generation enzyme-linked immunosorbent assay (DIAPRO Diagnostic Bioprobes, Milan, Italy) and Uni-Gold Recombigen/ALERE determine, respectively. Data analyses were done using SPSS version 20 (SPSS Inc., IL, USA).Results:The seroprevalence for HSV-2 type-specific IgG was 33.3% (90/270), and HIV antibodies were identified in 19.63% (53/270) of the women. The HIV co-infection was 38.8% (35/90) among HSV-2-positive women and 10% (18/180) among HSV-2-negative women. Majority of the HSV-2 positive women (62.2%, 56/90) presented in their 2nd trimester while 18.9% (17/90) in their 3rd trimester.Conclusion:The seroprevalence of HSV-2 in this pregnant population is lower than what is observed in some other Sub-Saharan African countries; however, HSV-2/HIV co-infection is high. The HSV-2-seronegative women are still susceptible to primary HSV-2 infection in pregnancy with increased risk for HIV co-infection and neonatal transmission.

Traditional Chinese Medicine as a Potential Source for HSV-1 Therapy by Acting on Virus or the Susceptibility of Host.

Herpes simplex virus type 1 (HSV-1) is the most common virus, with an estimated infection rate of 60–95% among the adult population. Once infected, HSV-1 can remain latent in the host for a lifetime and be reactivated in patients with a compromised immune system. Reactivation of latent HSV-1 can also be achieved by other stimuli. Though acyclovir (ACV) is a classic drug for HSV-1 infection, ACV-resistant strains have been found in immune-compromised patients and drug toxicity has also been commonly reported. Therefore, there is an urge to search for new anti-HSV-1 agents. Natural products with potential anti-HSV-1 activity have the advantages of minimal side effects, reduced toxicity, and they exert their effect by various mechanisms. This paper will not only provide a reference for the safe dose of these agents if they are to be used in humans, referring to the interrelated data obtained from in vitro experiments, but also introduce the main pharmacodynamic mechanisms of traditional Chinese medicine (TCM) against HSV-1. Taken together, TCM functions as a potential source for HSV-1 therapy by direct (blocking viral attachment/absorption/penetration/replication) or indirect (reducing the susceptibility to HSV-1 or regulating autophagy) antiviral activities. The potential of these active components in the development of anti-HSV-1 drugs will also be described.

Corroboration of a Major Role for Herpes Simplex Virus Type 1 in Alzheimer's Disease.

Strong evidence has emerged recently for the concept that herpes simplex virus type 1 (HSV1) is a major risk for Alzheimer’s disease (AD). This concept proposes that latent HSV1 in brain of carriers of the type 4 allele of the apolipoprotein E gene (APOE-ε4) is reactivated intermittently by events such as immunosuppression, peripheral infection, and inflammation, the consequent damage accumulating, and culminating eventually in the development of AD. Population data to investigate this epidemiologically, e.g., to find if subjects treated with antivirals might be protected from developing dementia—are available in Taiwan, from the National Health Insurance Research Database, in which 99.9% of the population has been enrolled. This is being extensively mined for information on microbial infections and disease. Three publications have now appeared describing data on the development of senile dementia (SD), and the treatment of those with marked overt signs of disease caused by varicella zoster virus (VZV), or by HSV. The striking results show that the risk of SD is much greater in those who are HSV-seropositive than in seronegative subjects, and that antiviral treatment causes a dramatic decrease in number of subjects who later develop SD. It should be stressed that these results apply only to those with severe cases of HSV1 or VZV infection, but when considered with the over 150 publications that strongly support an HSV1 role in AD, they greatly justify usage of antiherpes antivirals to treat AD. Three other studies are described which directly relate to HSV1 and AD: they deal respectively with lysosomal changes in HSV1-infected cell cultures, with evidence for a role of human herpes virus type 6 and 7 (HHV6 and HHV7) in AD, and viral effects on host gene expression, and with the antiviral characteristics of beta amyloid (Aβ). Three indirectly relevant studies deal respectively with schizophrenia, relating to antiviral treatment to target HSV1, with the likelihood that HSV1 is a cause of fibromyalgia (FM), and with FM being associated with later development of SD. Studies on the link between epilepsy, AD and herpes simplex encephalitis (HSE) are described also, as are the possible roles of APOE-ε4, HHV6 and HSV1 in epilepsy.

Molecular Mechanisms for Herpes Simplex Virus Type 1 Pathogenesis in Alzheimer's Disease.

This review focuses on research in the areas of epidemiology, neuropathology, molecular biology and genetics that implicates herpes simplex virus type 1 (HSV-1) as a causative agent in the pathogenesis of sporadic Alzheimer’s disease (AD). Molecular mechanisms whereby HSV-1 induces AD-related pathophysiology and pathology, including neuronal production and accumulation of amyloid beta (Aβ), hyperphosphorylation of tau proteins, dysregulation of calcium homeostasis, and impaired autophagy, are discussed. HSV-1 causes additional AD pathologies through mechanisms that promote neuroinflammation, oxidative stress, mitochondrial damage, synaptic dysfunction, and neuronal apoptosis. The AD susceptibility genes apolipoprotein E (APOE), phosphatidylinositol binding clathrin assembly protein (PICALM), complement receptor 1 (CR1) and clusterin (CLU) are involved in the HSV lifecycle. Polymorphisms in these genes may affect brain susceptibility to HSV-1 infection. APOE, for example, influences susceptibility to certain viral infections, HSV-1 viral load in the brain, and the innate immune response. The AD susceptibility gene cholesterol 25-hydroxylase (CH25H) is upregulated in the AD brain and is involved in the antiviral immune response. HSV-1 interacts with additional genes to affect cognition-related pathways and key enzymes involved in Aβ production, Aβ clearance, and hyperphosphorylation of tau proteins. Aβ itself functions as an antimicrobial peptide (AMP) against various pathogens including HSV-1. Evidence is presented supporting the hypothesis that Aβ is produced as an AMP in response to HSV-1 and other brain infections, leading to Aβ deposition and plaque formation in AD. Epidemiologic studies associating HSV-1 infection with AD and cognitive impairment are discussed. Studies are reviewed supporting subclinical chronic reactivation of latent HSV-1 in the brain as significant in the pathogenesis of AD. Finally, the rationale for and importance of clinical trials treating HSV-1-infected MCI and AD patients with antiviral medication is discussed.

Herpes simplex virus type 1 and Alzheimer's disease: possible mechanisms and signposts.

Support for the concept that herpes simplex virus type 1 (HSV1), when present in the brains of apolipoprotein E-ε4 carriers, is a major risk for Alzheimer's disease (AD) is increasing steadily, with over 120 publications providing direct or indirect evidence relevant to the hypothesis. No articles have contested the concept, apart from 3 published 13-18 yr ago. This review describes very recent studies on the role of HSV1 but refers also to older studies that provide background for some lesser-known related topics not covered in other recent reviews; these include the relevance of herpes simplex encephalitis and of epilepsy to AD, the action of IFN, and the possible relevance of the different types of DNA damage to AD-in particular, those caused by HSV1-and mechanisms of repair of damage. New epidemiologic data supporting previous studies on mild cognitive impairment and progression to AD are reviewed, as are those examining the relationship between total infectious burden (additive seropositivity to various microbes) and cognition/AD. The latter indicates the involvement of HSV1 and cytomegalovirus (and the necessity of taking into account any marked differences in sensitivity of antibody detection). Recent studies that provide further support for the occurrence of repeated reactivation of latent HSV1 in the brain in AD pathogenesis are also discussed.-Itzhaki, R. F. Herpes simplex virus type 1 and Alzheimer's disease: possible mechanisms and signposts.

Detection of herpes simplex virus type 2 (HSV-2) -specific cell-mediated immune responses in guinea pigs during latent HSV-2 genital infection

Genital infections with herpes simplex virus type 2 (HSV-2) are a source of considerable morbidity and are a health concern for newborns exposed to virus during vaginal delivery. Additionally, HSV-2 infection diminishes the integrity of the vaginal epithelium resulting in increased susceptibility of individuals to infection with other sexually transmitted pathogens. Understanding immune protection against HSV-2 primary infection and immune modulation of virus shedding events following reactivation of the virus from latency is important for the development of effective prophylactic and therapeutic vaccines. Although the murine model of HSV-2 infection is useful for understanding immunity following immunization, it is limited by the lack of spontaneous reactivation of HSV-2 from latency. Genital infection of guinea pigs with HSV-2 accurately models the disease of humans including the spontaneous reactivation of HSV-2 from latency and provides a unique opportunity to examine virus-host interactions during latency. Although the guinea pig represents an accurate model of many human infections, relatively few reagents are available to study the immunological response to infection. To analyze the cell-mediated immune response of guinea pigs at extended periods of time after establishment of HSV-2 latency, we have modified flow-cytometry based proliferation assays and IFN-γ ELISPOT assays to detect and quantify HSV-specific cell-mediated responses during latent infection of guinea pigs. Here we demonstrate that a combination of proliferation and ELISPOT assays can be used to quantify and characterize effecter function of virus-specific immune memory responses during HSV-latency.

Association of Depressed Mood With Herpes Simplex Virus-2 Immunoglobulin-G Levels in Pregnancy.

Depressed mood is common in pregnancy, is associated with stress, and could result in immune suppression that may lead to latent herpes viral reactivation. This study investigated whether depressed mood is associated with higher herpes viral IgG levels in pregnant women. Complete cross-sectional data from 247 pregnant women were available for this substudy. The data included demographics, scores on the Perceived Stress Scale and Profile of Mood States (POMS), and a panel of serum IgG levels for human herpesviruses. Only the herpes simplex virus type 2 (HSV-2) (genital herpes) IgG level was associated with Perceived Stress Scale and POMS-Depression/Dejection (POMS-D) score. Hierarchical multiple regression analysis was used to examine the association of POMS-D with herpesviral IgG levels adjusting for demographic variables. In the final model, African American race (β = .251, p < .001), older age (β = .199, p = .002), single marital status (β = -.304, p < .001), and depressed mood (β = .122, p = .04) were associated with HSV-2 IgG levels. In logistic regression, the strongest correlates of HSV IgG positivity were single marital status, followed by POMS-D scores and African American race. Genital herpes is a concern in pregnancy. Antibody titers may indicate asymptomatic viral shedding, viral reactivation, or primary viral infection. Antibody levels may be higher because of the immune changes during pregnancy and potential immune effects of depressed mood causing reactivation of latent HSV-2.

Analyses of herpes simplex virus type 1 latency and reactivation at the single cell level using fluorescent reporter mice

Herpes simplex virus type 1 (HSV-1) establishes a latent infection in sensory neurons from which the virus can periodically reactivate. Whilst latency establishment is thought to result from a failure to express immediate-early genes, we have previously shown that subpopulations of the latent neuronal reservoir have undergone lytic promoter activation prior to latency establishment. In the present study, we have investigated the biological properties of such latently infected neuronal subpopulations using Ai6 fluorescent reporter mice. Using this system we have determined that prior ICP0 or TK promoter activation does not correlate with increased latent virus DNA loads within individual cells and that neurons with evidence of historical lytic cycle promoter activity exhibit a comparable frequency of reactivation to that of the general latent cell population. Comparison of viral DNA content within cells harbouring latent HSV-1 genomes and those undergoing the earliest stages of reactivation has revealed that reactivation can initiate from cells harbouring a wide range of HSV-1 genome copies, but that exiting latency is biased towards cells bearing higher latent virus DNA loads.