Gene expression analyzed by microarrays in HSV-1 latent mouse trigeminal ganglion following heat stress

DLK-Dependent Biphasic Reactivation of Herpes Simplex Virus Latency Established in the Absence of Antivirals

Understanding the molecular mechanisms of herpes simplex virus 1 (HSV-1) latent infection and reactivation in neurons requires the use of in vitro model systems. Establishing a quiescent infection in cultured neurons is problematic, as any infectious virus released can superinfect the cultures. Previous studies have used the viral DNA replication inhibitor acyclovir to prevent superinfection and promote latency establishment. Data from these previous models have shown that reactivation is biphasic, with an initial phase I expression of all classes of lytic genes, which occurs independently of histone demethylase activity and viral DNA replication but is dependent on the cell stress protein DLK. Here, we describe a new model system using HSV-1 Stayput-GFP, a reporter virus that is defective for cell-to-cell spread and establishes latent infections without the need for acyclovir. The establishment of a latent state requires a longer time frame than previous models using DNA replication inhibitors. This results in a decreased ability of the virus to reactivate using established inducers, and as such, a combination of reactivation triggers is required. Using this system, we demonstrate that biphasic reactivation occurs even when latency is established in the absence of acyclovir. Importantly, phase I lytic gene expression still occurs in a histone demethylase and viral DNA replication-independent manner and requires DLK activity. These data demonstrate that the two waves of viral gene expression following HSV-1 reactivation are independent of secondary infection and not unique to systems that require acyclovir to promote latency establishment. IMPORTANCE Herpes simplex virus-1 (HSV-1) enters a latent infection in neurons and periodically reactivates. Reactivation manifests as a variety of clinical symptoms. Studying latency and reactivation in vitro is invaluable, allowing the molecular mechanisms behind both processes to be targeted by therapeutics that reduce the clinical consequences. Here, we describe a novel in vitro model system using a cell-to-cell spread-defective HSV-1, known as Stayput-GFP, which allows for the study of latency and reactivation at the single neuron level. We anticipate this new model system will be an incredibly valuable tool for studying the establishment and reactivation of HSV-1 latent infection in vitro. Using this model, we find that initial reactivation events are dependent on cellular stress kinase DLK but independent of histone demethylase activity and viral DNA replication. Our data therefore further validate the essential role of DLK in mediating a wave of lytic gene expression unique to reactivation.

Microbiome-Mediated Upregulation of MicroRNA-146a in Sporadic Alzheimer's Disease

The first indication of a potential mechanistic link between the pathobiology of the human gastrointestinal (GI)-tract microbiome and its contribution to the pathogenetic mechanisms of sporadic Alzheimer's disease (AD) came a scant 4 years ago (1). Ongoing research continues to strengthen the hypothesis that neurotoxic microbial-derived components of the GI tract microbiome can cross aging GI tract and blood-brain barriers and contribute to progressive proinflammatory neurodegeneration, as exemplified by the AD-process. Of central interest in these recent investigations are the pathological roles played by human GI tract resident Gram-negative anaerobic bacteria and neurotropic viruses-two prominent divisions of GI tract microbiome-derived microbiota-which harbor considerable pathogenic potential. It is noteworthy that the first two well-studied microbiota-the GI tract abundant Gram-negative bacteria Bacteroides fragilis and the neurotropic herpes simplex virus-1 both share a final common pathway of NF-κB (p50/p65) activation and microRNA-146a induction with ensuing pathogenic stimulation of innate-immune and neuroinflammatory pathways. These appear to strongly contribute to the inflammation-mediated amyloidogenic neuropathology of AD. This communication: (i) will review recent research contributions that have expanded our understanding of the nature of the translocation of microbiome-derived neurotoxins-across biophysiological barriers; (ii) will assess multiple-recent investigations of the induction of the proinflammatory pathogenic microRNA-146a by these two prominent classes of human microbiota; and (iii) will discuss the role of molecular neurobiology and mechanistic contribution of polymicrobial infections to AD-type neuropathological change.

A famciclovir + celecoxib combination treatment is safe and efficacious in the treatment of fibromyalgia

Objective

Infections and other stressors have been implicated in the development of fibromyalgia. We hypothesized that these stressors could result in recurrent reactivations of latent herpes virus infections, which could lead to the development of fibromyalgia. This study evaluated a famciclovir + celecoxib drug combination (IMC-1), active against suspected herpes virus reactivation and infection, for the treatment of fibromyalgia.

Methods

A total of 143 fibromyalgia patients were enrolled at 12 sites in a 16-week, double-blinded, placebo-controlled proof-of-concept trial. Randomized patients received either IMC-1 or placebo in a 1:1 ratio. Outcome measures included a 24-hour recall pain Numerical Rating Scale, the Revised Fibromyalgia Impact Questionnaire (FIQ-R), the Patient’s Global Impression of Change (PGIC) questionnaire, the Multidimensional Fatigue Inventory, the NIH Patient-Reported Outcomes Measurement Information System (PROMIS), and the Beck Depression Inventory-II conducted at baseline and weeks 6, 12, and 16 of the study.

Results

A significant decrease in fibromyalgia-related pain was observed for patients on IMC-1 treatment versus placebo. PGIC response rates were significantly improved with IMC-1 treatment. Overall, patient self-reported functioning, as measured by the FIQ-R, was significantly improved. Fatigue was also significantly improved as measured by the PROMIS fatigue inventory. The safety profile was encouraging. Despite the celecoxib component of IMC-1, gastrointestinal and nervous system treatment emergent adverse events were reported less frequently in the IMC-1 group, and study completion rates favored IMC-1 treatment.

Conclusion

IMC-1 was efficacious and safe in treating symptoms of fibromyalgia, supporting the hypothesis that herpes virus infections may contribute to this syndrome. Improved retention rates, decreased adverse event rates, and evidence of efficacy on a broad spectrum of outcome measures are suggestive that IMC-1 may represent an effective, novel treatment for fibromyalgia.

Nanomolar aluminum induces expression of the inflammatory systemic biomarker C-reactive protein (CRP) in human brain microvessel endothelial cells (hBMECs)

C-reactive protein (CRP; also known as pentraxin 1, PTX1), a 224 amino acid soluble serum protein organized into a novel pentameric ring-shaped structure, is a highly sensitive pathogenic biomarker for systemic inflammation. High CRP levels are found in practically every known inflammatory state, and elevated CRP levels indicate an increased risk for several common age-related human degenerative disorders, including cardiovascular disease, cancer, diabetes, and Alzheimer's disease (AD). While the majority of CRP is synthesized in the liver for secretion into the systemic circulation, it has recently been discovered that an appreciable amount of CRP is synthesized in highly specialized endothelial cells that line the vasculature of the brain and central nervous system (CNS). These highly specialized cells, the major cell type lining the human CNS vasculature, are known as human brain microvessel endothelial cells (hBMECs). In the current pilot study we examined (i) CRP levels in human serum obtained from AD and age-matched control patients; and (ii) analyzed the effects of nanomolar aluminum sulfate on CRP expression in primary hBMECs. The three major findings in this short communication are: (i) that CRP is up-regulated in AD serum; (ii) that CRP serum levels increased in parallel with AD progression; and (iii) for the first time show that nanomolar aluminum potently up-regulates CRP expression in hBMECs to many times its 'basal abundance'. The results suggest that aluminum-induced CRP may in part contribute to a pathophysiological state associated with a chronic systemic inflammation of the human vasculature.

Investigating the biology of alpha herpesviruses with MS-based proteomics

Viruses are intracellular parasites that can only replicate and spread in cells of susceptible hosts. Alpha herpesviruses (α-HVs) contain double-stranded DNA genomes of at least 120 kb, encoding for 70 or more genes. The viral genome is contained in an icosahedral capsid that is surrounded by a proteinaceous tegument layer and a lipid envelope. Infection starts in epithelial cells and spreads to the peripheral nervous system. In the natural host, α-HVs establish a chronic latent infection that can be reactivated and rarely spread to the CNS. In the nonnatural host, viral infection will in most cases spread to the CNS with often fatal outcome. The host response plays a crucial role in the outcome of viral infection. α-HVs do not encode all the genes required for viral replication and spread. They need a variety of host gene products including RNA polymerase, ribosomes, dynein, and kinesin. As a result, the infected cell is dramatically different from the uninfected cell revealing a complex and dynamic interplay of viral and host components required to complete the virus life cycle. In this review, we describe the pivotal contribution of MS-based proteomics studies over the past 15 years to understand the complicated life cycle and pathogenesis of four α-HV species from the alphaherpesvirinae subfamily: Herpes simplex virus-1, varicella zoster virus, pseudorabies virus and bovine herpes virus-1. We describe the viral proteome dynamics during host infection and the host proteomic response to counteract such pathogens.

The role of cyclooxygenase in multiplication and reactivation of HSV-1 in vestibular ganglion neurons

Reactivation of latent herpes simplex type 1 (HSV-1) and nerve inflammation have been shown to be involved in vertigo-related vestibular pathogenesis. Treatments of such diseases have been less than perfect. Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to suppress reactivation of HSV-1 in trigeminal ganglions. However, whether this drug can affect reactivation of HSV-1 in vestibular ganglions is unclear. Due to the difficulties of constructing in vivo animal models, in this study, we developed a vestibular ganglion culture system, in which vestibular neurons were latently or lytically infected with HSV-1. Indomethacin and celecoxib were selected to measure their effects on HSV-1. Trichostatin A was used to reactivate HSV-1 in latently infected neurons. Cycloxygenase-2, which is the target of NSAIDs, was induced by HSV-1 in the lytically infected cultures, with an increase of 14-fold. Although it appeared that indomethacin and celecoxib showed limited but concentration-dependent inhibition effects on viral production under our condition, indomethacin decreased reactivation rate of HSV-1 by about 20%. Though more in vitro or in vivo studies are needed to confirm the effects of the drugs, our study may provide a potential way to investigate the mechanism of HSV-related vestibular pathogenesis as well as new treatments of vertigo-related diseases.

Proteomics in immunity and herpes simplex encephalitis

The genetic theory of infectious diseases has proposed that susceptibility to life-threatening infectious diseases in childhood, occurring in the course of primary infection, results mostly from individually rare but collectively diverse single-gene variants. Recent evidence of an ever-expanding spectrum of genes involved in susceptibility to infectious disease indicates that the paradigm has important implications for diagnosis and treatment. One such pathology is childhood herpes simplex encephalitis, which shows a pattern of rare but diverse disease-disposing genetic variants. The present report shows how proteomics can help to understand susceptibility to childhood herpes simplex encephalitis and other viral infections, suggests that proteomics may have a particularly important role to play, emphasizes that variation over the population is a critical issue for proteomics and notes some new challenges for proteomics and related bioinformatics tools in the context of rare but diverse genetic defects.

The proteome of Toll-like receptor 3-stimulated human immortalized fibroblasts: implications for susceptibility to herpes simplex virus encephalitis

BACKGROUND

Inborn errors in Toll-like receptor 3 (TLR3)-IFN type I and III pathways have been implicated in susceptibility to herpes simplex virus encephalitis (HSE) in children, but most patients studied do not carry mutations in any of the genes presently associated with HSE susceptibility. Moreover, many patients do not display any TLR3-IFN-related fibroblastic phenotype.

OBJECTIVE

To study other signaling pathways downstream of TLR3 and/or other independent pathways that may contribute to HSE susceptibility.

METHODS

We used the stable isotope labeling of amino acids in cell culture proteomics methodology to measure changes in the human immortalized fibroblast proteome after TLR3 activation.

RESULTS

Cells from healthy controls were compared with cells from a patient with a known genetic etiology of HSE (UNC-93B-/-) and also to cells from an HSE patient with an unknown gene defect. Consistent with known variation in susceptibility of individuals to viral infections, substantial variation in the response level of different healthy controls was observed, but common functional networks could be identified, including upregulation of superoxide dismutase 2. The 2 patients with HSE studied show clear differences in functional response networks when compared with healthy controls and also when compared with each other.

CONCLUSIONS

The present study delineates a number of novel proteins, TLR3-related pathways, and cellular phenotypes that may help elucidate the genetic basis of childhood HSE. Furthermore, our results reveal superoxide dismutase 2 as a potential therapeutic target for amelioration of the neurologic sequelae caused by HSE.

NF-κB-regulated, proinflammatory miRNAs in Alzheimer's disease

Abundant neurochemical, neuropathological, and genetic evidence suggests that a critical number of proinflammatory and innate immune system-associated factors are involved in the underlying pathological pathways that drive the sporadic Alzheimer's disease (AD) process. Most recently, a series of epigenetic factors - including a select family of inducible, proinflammatory, NF-κB-regulated small noncoding RNAs called miRNAs - have been shown to be significantly elevated in abundance in AD brain. These upregulated miRNAs appear to be instrumental in reshaping the human brain transcriptome. This reorganization of mRNA speciation and complexity in turn drives proinflammatory and pathogenic gene expression programs. The ensuing, progressively altered immune and inflammatory signaling patterns in AD brain support immunopathogenetic events and proinflammatory features of the AD phenotype. This report will briefly review what is known concerning NF-κB-inducible miRNAs that are significantly upregulated in AD-targeted anatomical regions of degenerating human brain cells and tissues. Quenching of NF-κB-sensitive inflammatory miRNA signaling using NF-κB-inhibitors such as the polyphenolic resveratrol analog trans-3,5,4'-trihydroxystilbene (CAY10512) may have some therapeutic value in reducing inflammatory neurodegeneration. Antagonism of NF-κB-inducing, and hence proinflammatory, epigenetic and environmental factors, such as the neurotrophic herpes simplex virus-1 and exposure to the potent neurotoxin aluminum, are briefly discussed. Early reports further indicate that miRNA neutralization employing anti-miRNA (antagomir) strategies may hold future promise in the clinical management of this insidious neurological disorder and expanding healthcare concern.

Regulation of complement factor H (CFH) by multiple miRNAs in Alzheimer's disease (AD) brain

Human brain cells rely on a specific subset of microRNAs (miRNAs or miRs) to shape their gene expression patterns, and this is mediated through microRNA effects on messenger RNA (mRNA) speciation and complexity. In recent studies (a) in short post-mortem interval Alzheimer's disease (AD) brain tissues versus age-matched controls, and (b) in pro-inflammatory cytokine- and Aβ42 peptide-stressed human neuronal-glial (HNG) cells in primary culture, we have identified several brain-abundant miRNA species found to be significantly up-regulated, including miR-125b and miR-146a. Both of these nuclear factor kappa B (NF-κB)-activated, 22 nucleotide small non-coding RNAs (sncRNAs) target the mRNA of the key, innate-immune- and inflammation-related regulatory protein, complement factor-H (CFH; chr 1q32), resulting in significant decreases in CFH expression (p < 0.01, ANOVA). Our results further indicate that HNG cells respond to IL-1β + Aβ42-peptide-induced stress by significant NF-κB-modulated up-regulation of miRNA-125b- and miRNA-146a. The complex interactive signaling of NF-κB, miR-125b, miR-146a, and perhaps other miRNAs, further illustrate interplay between inducible transcription factors and multiple pro-inflammatory sncRNAs that regulate CFH expression. The novel concept of miRNA actions involving mRNA target convergence and divergence are proposed and discussed. The combinatorial use of NF-кB inhibitors with anti-miRNAs (AMs; antagomirs) may have potential against CFH-driven pathogenic signaling in neurodegenerative disease, and may redirect our therapeutic perspectives to novel treatment strategies that have not yet been considered.

Regulation of cyclooxygenase-2 expression by heat: a novel aspect of heat shock factor 1 function in human cells

The heat-shock response, a fundamental defense mechanism against proteotoxic stress, is regulated by a family of heat-shock transcription factors (HSF). In humans HSF1 is considered the central regulator of heat-induced transcriptional responses. The main targets for HSF1 are specific promoter elements (HSE) located upstream of heat-shock genes encoding cytoprotective heat-shock proteins (HSP) with chaperone function. In addition to its cytoprotective function, HSF1 was recently hypothesized to play a more complex role, regulating the expression of non-HSP genes; however, the non-canonical role of HSF1 is still poorly understood. Herein we report that heat-stress promotes the expression of cyclooxygenase-2 (COX-2), a key regulator of inflammation controlling prostanoid and thromboxane synthesis, resulting in the production of high levels of prostaglandin-E(2) in human cells. We show that heat-induced COX-2 expression is regulated at the transcriptional level via HSF1-mediated signaling and identify, by in-vitro reporter gene activity assay and deletion-mutant constructs analysis, the COX-2 heat-responsive promoter region and a new distal cis-acting HSE located at position -2495 from the transcription start site. As shown by ChIP analysis, HSF1 is recruited to the COX-2 promoter rapidly after heat treatment; by using shRNA-mediated HSF1 suppression and HSE-deletion from the COX-2 promoter, we demonstrate that HSF1 plays a central role in the transcriptional control of COX-2 by heat. Finally, COX-2 transcription is also induced at febrile temperatures in endothelial cells, suggesting that HSF1-dependent COX-2 expression could contribute to increasing blood prostaglandin levels during fever. The results identify COX-2 as a human non-classical heat-responsive gene, unveiling a new aspect of HSF1 function.

The influence of stress factors on the reactivation of latent herpes simplex virus type 1 in infected mice

This study shows that the influence of different stress factors impacts the reactivation of latent herpes simplex virus type 1 (HSV-1) specifically in the trigeminal ganglion of infected mice. Different stress factors including hyperthermia, hypothermia, fatigue, and immunosuppression were exerted on mice infected with HSV-1. These viral antigens were then detected in the trigeminal ganglion region of infected mice under the influence of each stress factor, with hyperthermia having the most influence on reactivation. Interestingly, an increase in IL-6 was also detected in mice subjected to hyperthermia. These studies therefore suggest that stress can induce the reactivation of latent HSV-1, possibly through the induction of IL-6, in the trigeminal ganglion region of infected mice. This reveals a new insight on the pathogenesis of relapse infection of HSV-1.

NF-кB-regulated micro RNAs (miRNAs) in primary human brain cells

Micro RNAs (miRNAs), small and labile ~22 nucleotide-sized fragments of single stranded RNA, are important regulators of messenger (mRNA) complexity and in shaping the transcriptome of a cell. In this communication, we utilized amyloid beta 42 (Aβ42) peptides and interleukin-1beta (IL-1β) as a combinatorial, physiologically-relevant stress to induce miRNAs in human primary neural (HNG) cells (a co-culture of neurons and astroglia). Specific miRNA up-regulation was monitored using miRNA arrays, Northern micro-dot blots and RT-PCR. Selective NF-кB translocation and DNA binding inhibitors, including the chelator and anti-oxidant pyrollidine dithiocarbamate (PDTC) and the polyphenolic resveratrol analog CAY10512 (trans-3,5,4'-trihydroxystilbene), indicated the NF-кB sensitivity of several brain miRNAs, including miRNA-9, miRNA-125b and miRNA-146a. The inducible miRNA-125b and miRNA-146a, and their verified mRNA targets, including 15-lipoxygenase (15-LOX), synapsin-2 (SYN-2), complement factor H (CFH) and tetraspanin-12 (TSPAN12), suggests complex and highly interactive roles for NF-кB, miRNA-125b and miRNA-146a. These data further indicate that just two NF-кB-mediated miRNAs have tremendous potential to contribute to the regulation of neurotrophic support, synaptogenesis, neuroinflammation, innate immune signaling and amyloidogenesis in stressed primary neural cells of the human brain.

Up-regulation of NF-kB-sensitive miRNA-125b and miRNA-146a in metal sulfate-stressed human astroglial (HAG) primary cell cultures

Micro RNAs (miRNAs) constitute a unique class of small, non-coding ribonucleic acids (RNAs) that regulate gene expression at the post-transcriptional level. The presence of two inducible miRNAs, miRNA-125b and miRNA-146a, involved in respectively, astroglial cell proliferation and in the innate immune and inflammatory response, is significantly up-regulated in human neurological disorders including Alzheimer's disease (AD). In this study we analyzed abundances miRNA-125b and miRNA-146a in magnesium-, iron-, gallium, and aluminum-sulfate-stressed human-astroglial (HAG) cells, a structural and immune-responsive brain cell type. The combination of iron- plus aluminum-sulfate was found to be significantly synergistic in up-regulating reactive oxygen species (ROS) abundance, NF-кB-DNA binding and miRNA-125b and miRNA-146a expression. Treatment of metal-sulfate stressed HAG cells with the antioxidant phenyl butyl nitrone (PBN) or the NF-кB inhibitors curcumin, the metal chelator-anti-oxidant pyrollidine dithiocarbamate (PDTC), or the resveratrol analog CAY10512, abrogated both NF-кB signaling and induction of these miRNAs. Our observations further illustrate the potential of physiologically relevant amounts of aluminum and iron sulfates to synergistically up-regulate specific miRNAs known to contribute to AD-relevant pathogenetic mechanisms, and suggest that antioxidants or NF-кB inhibitors may be useful to quench metal-sulfate triggered genotoxicity.

Differential expression of miRNA-146a-regulated inflammatory genes in human primary neural, astroglial and microglial cells

MicroRNA-146a (miRNA-146a) is an inducible, 22 nucleotide, small RNA over-expressed in Alzheimer's disease (AD) brain. Up-regulated miRNA-146a targets several inflammation-related and membrane-associated messenger RNAs (mRNAs), including those encoding complement factor-H (CFH) and the interleukin-1 receptor associated kinase-1 (IRAK-1), resulting in significant decreases in their expression (p<0.05, ANOVA). In this study we assayed miRNA-146a, CFH, IRAK-1 and tetraspanin-12 (TSPAN12), abundances in primary human neuronal-glial (HNG) co-cultures, in human astroglial (HAG) and microglial (HMG) cells stressed with Aβ42 peptide and tumor necrosis factor alpha (TNFα). The results indicate a consistent inverse relationship between miRNA-146a and CFH, IRAK-1 and TSPAN12 expression levels, and indicate that HNG, HAG and HMG cell types each respond differently to Aβ42-peptide+TNFα-triggered stress. While the strongest miRNA-146a-IRAK-1 response was found in HAG cells, the largest miRNA-146a-TSPAN12 response was found in HNG cells, and the most significant miRNA-146a-CFH changes were found in HMG cells, the 'resident scavenging macrophages' of the brain.

Virus reactivation: a panoramic view in human infections

Viruses are obligate intracellular parasites, relying to a major extent on the host cell for replication. An active replication of the viral genome results in a lytic infection characterized by the release of new progeny virus particles, often upon the lysis of the host cell. Another mode of virus infection is the latent phase, where the virus is 'quiescent' (a state in which the virus is not replicating). A combination of these stages, where virus replication involves stages of both silent and productive infection without rapidly killing or even producing excessive damage to the host cells, falls under the umbrella of a persistent infection. Reactivation is the process by which a latent virus switches to a lytic phase of replication. Reactivation may be provoked by a combination of external and/or internal cellular stimuli. Understanding this mechanism is essential in developing future therapeutic agents against viral infection and subsequent disease. This article examines the published literature and current knowledge regarding the viral and cellular proteins that may play a role in viral reactivation. The focus of the article is on those viruses known to cause latent infections, which include herpes simplex virus, varicella zoster virus, Epstein-Barr virus, human cytomegalovirus, human herpesvirus 6, human herpesvirus 7, Kaposi's sarcoma-associated herpesvirus, JC virus, BK virus, parvovirus and adenovirus.

Upregulation of micro RNA-146a (miRNA-146a), a marker for inflammatory neurodegeneration, in sporadic Creutzfeldt-Jakob disease (sCJD) and Gerstmann-Straussler-Scheinker (GSS) syndrome

A mouse- and human-brain-abundant, nuclear factor (NF)-кB-regulated, micro RNA-146a (miRNA-146a) is an important modulator of the innate immune response and inflammatory signaling in specific immunological and brain cell types. Levels of miRNA-146a are induced in human brain cells challenged with at least five different species of single- or double-stranded DNA or RNA neurotrophic viruses, suggesting a broad role for miRNA-146a in the brain's innate immune response and antiviral immunity. Upregulated miRNA-146a is also observed in pro-inflammatory cytokine-, Aβ42 peptide- and neurotoxic metal-induced, oxidatively stressed human neuronal-glial primary cell cocultures, in murine scrapie and in Alzheimer's disease (AD) brain. In AD, miRNA-146a levels are found to progressively increase with disease severity and co-localize to brain regions enriched in inflammatory neuropathology. This study provides evidence of upregulation of miRNA-146a in extremely rare (incidence 1-10 per 100 million) human prion-based neurodegenerative disorders, including sporadic Creutzfeldt-Jakob disease (sCJD) and Gerstmann-Straussler-Scheinker syndrome (GSS). The findings suggest that an upregulated miRNA-146a may be integral to innate immune or inflammatory brain cell responses in prion-mediated infections and to progressive and irreversible neurodegeneration of both the murine and human brain.

A limited innate immune response is induced by a replication-defective herpes simplex virus vector following delivery to the murine central nervous system

Herpes simplex virus type 1 (HSV-1)-based vectors readily transduce neurons and have a large payload capacity, making them particularly amenable to gene therapy applications within the central nervous system (CNS). Because aspects of the host responses to HSV-1 vectors in the CNS are largely unknown, we compared the host response of a nonreplicating HSV-1 vector to that of a replication-competent HSV-1 virus using microarray analysis. In parallel, HSV-1 gene expression was tracked using HSV-specific oligonucleotide-based arrays in order to correlate viral gene expression with observed changes in host response. Microarray analysis was performed following stereotactic injection into the right hippocampal formation of mice with either a replication-competent HSV-1 or a nonreplicating recombinant of HSV-1, lacking the ICP4 gene (ICP4-). Genes that demonstrated a significant change (P < .001) in expression in response to the replicating HSV-1 outnumbered those that changed in response to mock or nonreplicating vector by approximately 3-fold. Pathway analysis revealed that both the replicating and nonreplicating vectors induced robust antigen presentation but only mild interferon, chemokine, and cytokine signaling responses. The ICP4- vector was restricted in several of the Toll-like receptor-signaling pathways, indicating reduced stimulation of the innate immune response. These array analyses suggest that although the nonreplicating vector induces detectable activation of immune response pathways, the number and magnitude of the induced response is dramatically restricted compared to the replicating vector, and with the exception of antigen presentation, host gene expression induced by the nonreplicating vector largely resembles mock infection.

HSV-1 infection of human brain cells induces miRNA-146a and Alzheimer-type inflammatory signaling

Herpes simplex virus type-1 (HSV-1) infection of human brain cells induces changes in gene expression favorable to the propagation of the infecting agent and detrimental to the function of the host cells. We report that infection of human primary neural cells with a high phenotypic reactivator HSV-1 (17syn+) induces upregulation of a brain-enriched microRNA (miRNA)-146a that is associated with proinflammatory signaling in stressed brain cells and Alzheimer's disease. Expression of cytoplasmic phospholipase A2, the inducible prostaglandin synthase cyclooxygenase-2, and the neuroinflammatory cytokine interleukin-1beta were each upregulated. A known miRNA-146a target in the brain, complement factor H, was downregulated. These data suggest a role for HSV-1-induced miRNA-146a in the evasion of HSV-1 from the complement system, and the activation of key elements of the arachidonic acid cascade known to contribute to Alzheimer-type neuropathological change.

Localization of COX-1 and COX-2 in the intracranial dura mater of the rat

Primary headaches such as migraine can be aborted by systemic administration of non-steroidal anti-inflammatory drugs (NSAIDs), potentially through the non-selective inhibition of cyclooxygenase (COX) activity in the intracranial meninges. In this study we have used single and double labeling immunohistochemistry to examine the distribution of the COX-1 and COX-2 isoforms in the intracranial dura mater of the rat and identify cell types that express them. COX-1 immunoreactivity was found in medium and small dural blood vessels and was co-expressed with the endothelial cell markers vimentin and the endothelial isoform of nitric oxide synthase (ecNOS). COX-1 was also found to be present in most dural mast cells. COX-2 was mainly expressed in ED2-positive resident dural macrophages. Constitutive COX-2 expression was also found in some axonal profiles, many of which were co-labeled with the nociceptor peptide marker CGRP. The findings suggest that NSAIDs may abort headache, at least in part, by inhibiting either neuronal or non-neuronal COX activity in the dura mater.

Gene expression profiling by microarray analysis reveals an important role for caspase-1 in dengue virus-induced p53-mediated apoptosis

Recently, a dengue virus-induced apoptosis p53- and mitochondria-mediated were reported in human and animal cells. To understand further the underlying mechanisms, a p53-deficient cell line, H1299, and a p53-knockin cell line, H273, were infected with dengue type 1 virus and the cellular gene expression profiles at the mRNA level were analyzed by affymetrix array analysis. The results showed 183 genes with at least twofold increase at mRNA expression level in dengue virus-infected cells. Among the 183 genes, 68 genes were up-regulated in both H1299 and H273 cells and 78 genes were found to be up-regulated in only H273 cells. Eleven selected genes, mainly involved in IFN-pathway, cell cycle, signal transduction, and ubiquitin-proteasome pathways were confirmed using qualitative and quantitative PCR. Interestingly, an approximately 32-fold increase in caspase-1 expression was observed in the p53-knockin cell line, H273. Gene silencing of caspase-1 or inhibition of caspase-1 activity led to reduction in dengue virus-induced apoptosis with minimal effect on virus replication.

Cyclooxygenase (COX)-inhibiting drug reduces HSV-1 reactivation in the mouse eye model

PURPOSE

To examine the effects of COX inhibitors on suppressing HSV-1 reactivation in a mouse model.

METHODS

BALB/c mice were latently infected with HSV-1 and treated by 0.1% bromfenac Na eye drops, 0.1% pranoprofen eye drops, 0.1 mg oral etodolac 4 times/day, and saline for 4 days. After reactivating the latent HSV-1, we swabbed the mouse ocular surface for the culture of the infectious virus and assessed the viral loads in the eyes and trigeminal ganglia (TGs) using real-time PCR to determine the treatment efficacies.

RESULTS

With stimulated reactivation, 10 of 24 (41.7%), 5 of 10 (50.0%), 17 of 25 (68%), and 16 of 22 eyes (72.7%) showed positive swab results in the bromfenac Na, etodolac, pranoprofen, and saline groups, respectively; and a significant difference was seen only between the bromfenac Na and saline groups (p = 0.033). None of the three drug-treated groups showed any significant difference from the saline group in the viral DNA in the eyes and TGs (p > 0.05).

CONCLUSIONS

Bromfenac Na eye drops can suppress HSV-1 reactivation.

Heat-induced reactivation of HSV-1 in latent mice: upregulation in the TG of CD83 and other immune response genes and their LAT-ICP0 locus

PURPOSE

To determine changes in host gene expression in HSV-1 latent trigeminal ganglia (TG) after hyperthermic stress.

METHODS

Scarified corneas of 6-week-old female BALB/c mice were inoculated with either HSV-1 17Syn(+) (high phenotypic reactivator) or 17DeltaPst(LAT(-)) (low phenotypic reactivator) at 10(4) plaque-forming units/eye. At 28 days after infection, viral reactivation was induced in some of the infected mice with hyperthermic stress, and the mice were killed after 1 hour. Heat-treated uninfected mice served as the control. Labeled cRNA derived from TG-isolated total RNA was hybridized to 430 2.0 chips containing 14,000 mouse genes. Gene expression was confirmed by quantitative real-time PCR.

RESULTS

There was no difference in gene expression in the non-heat-treated mice. Gene expression in the TG of each of the heat-treated mouse groups (17Syn(+), 17DeltaPst(LAT(-)) and uninfected) yielded upregulation of more than twofold of a group of the same genes, designated as heat stress-induced gene expression. Twenty-nine genes (0.2%) were significantly upregulated (2- to 17-fold) when the heat stress-induced gene expression was subtracted from the gene expression of 17Syn(+) latent TG relative to 17DeltaPst(LAT(-)) latent TG 1 hour after mouse hyperthermic stress. Nine host adaptive immunity genes comprising Ig molecules, CD83, CD8A, ADA, and CCL8 were the largest subset upregulated, and all were confirmed by real-time PCR. Others identified included genes involved in hypothalamic-pituitary gland functions.

CONCLUSIONS

Hyperthermic stress-induced reactivation of the HSV-1 high phenotypic reactivator can upregulate gene expression involved in B-cell function and in T-cell function. CD83 is implicated in HSV-1 latency, suggesting it could also be involved in immune-mediated mechanisms of viral reactivation.

Ocular HSV-1 latency, reactivation and recurrent disease

Ocular infection with HSV-1 continues to be a serious clinical problem despite the availability of effective antivirals. Primary infection with HSV-1 can involve ocular and adenaxial sites and can manifest as blepharitis, conjunctivitis, or corneal epithelial keratitis. After initial ocular infection, HSV-1 can establish latent infection in the trigeminal ganglia for the lifetime of the host. During latency, the viral genome is retained in the neuron without producing viral proteins. However, abundant transcription occurs at the region encoding the latency-associated transcript, which may play significant roles in the maintenance of latency as well as neuronal reactivation. Many host and viral factors are involved in HSV-1 reactivation from latency. HSV-1 DNA is shed into tears and saliva of most adults, but in most cases this does not result in lesions. Recurrent disease occurs as HSV-1 is carried by anterograde transport to the original site of infection, or any other site innervated by the latently infected ganglia, and can reinfect the ocular tissues. Recurrent corneal disease can lead to corneal scarring, thinning, stromal opacity and neovascularization and, eventually, blindness. In spite of intensive antiviral and anti-inflammatory therapy, a significant percentage of patients do not respond to chemotherapy for herpetic necrotizing stromal keratitis. Therefore, the development of therapies that would reduce asymptomatic viral shedding and lower the risks of recurrent disease and transmission of the virus is key to decreasing the morbidity of ocular herpetic disease. This review will highlight basic HSV-1 virology, and will compare the animal models of latency, reactivation, and recurrent ocular disease to the current clinical data.

Molecular analysis of human cancer cells infected by an oncolytic HSV-1 reveals multiple upregulated cellular genes and a role for SOCS1 in virus replication

Oncolytic herpes simplex viruses (oHSVs) are promising anticancer therapeutics. We sought to characterize the functional genomic response of human cancer cells to oHSV infection using G207, an oHSV previously evaluated in a phase I trial. Five human malignant peripheral nerve sheath tumor cell lines, with differing sensitivity to oHSV, were infected with G207 for 6 h. Functional genomic analysis of virus-infected cells demonstrated large clusters of downregulated cellular mRNAs and smaller clusters of those upregulated, including 21 genes commonly upregulated in all five lines. Of these, 7 are known to be HSV-1 induced and 14 represent novel virus-regulated genes. Gene ontology analysis revealed that a majority of G207-upregulated genes are involved in Janus kinase/signal transducer and activator of transcription signaling, transcriptional regulation, nucleic acid metabolism, protein synthesis and apoptosis. Ingenuity networks highlighted nodes for AP-1 subunits and interferon signaling via STAT1, suppressor of cytokine signaling-1 (SOCS1), SOCS3 and RANTES. As biological confirmation, we found that virus-mediated upregulation of SOCS1 correlated with sensitivity to G207 and that depletion of SOCS1 impaired virus replication by >10-fold. Further characterization of roles provided by oHSV-induced cellular genes during virus replication may be utilized to predict oncolytic efficacy and to provide rational strategies for designing next-generation oncolytic viruses.

Biological interactions between herpesviruses and cyclooxygenase enzymes

Decades ago, medical researchers noted that non-steroidal anti-inflammatory drugs (NSAIDs), for example aspirin and indomethacin, modulate primary herpesvirus infections and diminish reactivation of latent herpesvirus infections. NSAIDs inhibit cyclooxygenase (COX) enzymes, molecules necessary for generation of prostaglandins. Numerous studies indicate that herpesvirus infections elicit elevated levels of cyclooxygenase 2 (COX-2) with a resultant increase in prostaglandin E(2) levels (PGE(2)). Thus, the biochemical pathway underlying the anti-herpetic mechanism of NSAIDs is linked to the inhibition of COX. The precise roles of COX-2 and PGE(2) in the viral life cycle are unknown. However, among the alphaherpesvirus, betaherpesvirus and gammaherpesvirus subfamilies, evolutionarily conserved mechanisms ensure modulated expression of COX molecules, underscoring their importance in viral replication and virus-host interactions.

The cellular response to herpes simplex virus type 1 (HSV-1) during latency and reactivation

In order to learn more about the cellular response to viral gene activity during latency and reactivation of herpes simplex virus type 1 (HSV-1), the authors have employed microarray analysis. On an array of about 1200 cellular genes, approximately 56 genes were found to be differentially regulated in infected trigeminal ganglia of mice, compared to uninfected mice, during latency and reactivation. Of these genes, 10 were examined more closely using quantitative real-time polymerase chain reaction (PCR) to confirm the microarray results. Genes involved in interferon and other signaling pathways appeared to predominate in response to a latent or reactivating HSV infection. Interestingly, some genes found to be differentially regulated in latently infected ganglia are neuronal-specific genes (pro-opiomelanocortinin; zinc finger proteins of the cerebellum 1 and 2). During reactivation, the involvement of several cell signaling molecules that may be important for the initiation of an HSV infection was observed, including various receptors and molecules involved in cell-cell spread.

Role of inflammatory cytokine-induced cyclooxygenase 2 in the ocular immunopathologic disease herpetic stromal keratitis

Ocular infection with herpes simplex virus (HSV) results in a blinding immunoinflammatory stromal keratitis (SK) lesion. Early preclinical events include polymorphonuclear neutrophil (PMN) infiltration and neovascularization in the corneal stroma. We demonstrate here that HSV infection of the cornea results in the upregulation of the cyclooxygenase 2 (COX-2) enzyme. Early after infection, COX-2 was produced from uninfected stromal fibroblasts as an indirect effect of virus infection. Subsequently, COX-2 may also be produced from other inflammatory cells that infiltrate the cornea. The induction of COX-2 is a critical event, since inhibition of COX-2 with a selective inhibitor was shown to reduce corneal angiogenesis and SK severity. The administration of a COX-2 inhibitor resulted in compromised PMN infiltration into the cornea, as well as diminished corneal vascular endothelial growth factor levels, likely accounting for the reduced angiogenic response. COX-2 stimulation by HSV infection represents a critical early event accessible for therapy and the control of SK severity.

Microarray and real-time RT-PCR analyses of a novel set of differentially expressed human genes in ECV304 endothelial-like cells infected with dengue virus type 2

The cellular and molecular pathways of dengue infection have not been as intensively studied compared to the host immunological responses. Changes in mRNA expression levels of ECV304 human endothelial-like cells following infection with the virulent New Guinea C strain of dengue virus type 2 were analyzed by a microarray system comprising 7600 oligonucleotide cDNAs. After normalization against the uninfected control using two independent software programs, 111 genes exhibited at least a 1.5-fold difference in expression level. Out of these, 21 mRNAs were upregulated while 90mRNAs were downregulated. Quantitative real-time RT-PCR was then performed to determine the expression patterns of 15 selected genes of interest involved in the cell cycle (MAD3), apoptosis (RIPK3, PDCD8), cellular receptors (H963, CCR7, KLRC3), transcriptional regulation (RUNX3, HNF4G, MIZ1), signal transduction (HSP27, TRIP, MAP4K4), enzymes (angiotensinogen), protein transport (AP4M1), and cytoskeleton (ACTA2). Dengue virus infection resulted in the downregulation of the C-terminal alternatively spliced p53 variant, the pro-apoptotic IG20 and IG20-SV2 isoforms, and the Fas apoptosis inhibitory molecule (FAIM). Most of the real-time RT-PCR data showed concordance with the normalized microarray data. Hence, real-time RT-PCR validation of high-throughput gene microarray screening is important and necessary before further conclusions on gene expression can be drawn. This study elucidated novel information on the complex responses at the transcriptional level in susceptible human endothelial-like cells induced by a virulent dengue virus strain implicated in the pathogenesis of dengue and/or its complications.

Inhibition of Cyclooxygenase 2 Synthesis SuppressesHerpes simplexVirus Type 1 Reactivation

Recurrent herpes virus infection, in which the virus reactivates from the nervous system and causes painful lesions in peripheral tissues, is a significant clinical problem. Our recent studies showing that the amount of cyclooxygenase 2 (COX-2) in the trigeminal ganglia of heat-stressed untreated mice is higher than the amount in heat-stressed mice treated with the COX-2 inhibitor, celecoxib, have indicated that the prostaglandin synthesis pathway--and in particular COX-2--may be an intermediate in the pathway to herpes viral reactivation. To further study this process, we infected the corneas of mice using topical application to a lightly scratched epithelium and waited 30 days for Herpes simplex virus type 1 (HSV-1) latency to be established in the trigeminal ganglia. Prior to the induction of viral reactivation, the mice were treated orally with celecoxib. Treated and untreated mice were induced to undergo reactivation by immersion in 43 degrees C water for 10 min. The shedding of virus at the ocular surface was determined by culturing ocular swabs with indicator cells. The presence of infectious virus in the trigeminal ganglion was evaluated by incubating ganglion homogenates with indicator cells and observing for cytopathic effect. Celecoxib treatment significantly suppressed viral reactivation when given prophylactically by the gastrointestinal route. The numbers of corneas and ganglia containing infectious virus were significantly lower in the celecoxib-treated animals, compared to the placebo-treated mice. These experiments demonstrate that a selective COX-2 inhibitor can suppress hyperthermic stress-induced herpes viral reactivation in the nervous system. It may be possible to use COX-2 inhibitors to prevent viral reactivation in high-risk patients by drug prophylaxis.

Microarray analysis in the HSV-1 latently infected mouse trigeminal ganglion

PURPOSE

To review our previous studies regarding alterations in gene expression in HSV-1 latently infected mouse trigeminal ganglia (TGs) following treatment with immunosuppressants and hyperthermia.

METHODS

Uninfected and HSV-1 latently infected mice were treated with immunosuppressants or heat stressed (43 degrees C for 10 minutes). In the immunosuppressant study, 4 groups of animals were examined: (1) uninfected, not treated; (2) uninfected, drug-treated; (3) latently infected, not treated; and (4) latently infected, drug-treated. In the hyperthermia study, TG from 6 groups of mice were studied: (1) uninfected, not stressed; (2) uninfected, heat-stressed; killed at 6 hours after hyperthermia; (3) uninfected, heat-stressed, killed at 24 hours after hyperthermia; (4) latently infected, not stressed; (5) latently infected, heat-stressed, killed at 6 hours after hyperthermia; and (6) latently infected, heat-stressed, killed at 24 hours after hyperthermia. PolyA mRNA from the TGs of each group was reverse-transcribed, labeled with P, incubated on a gene array membrane, and analyzed by phosphorimaging. As a comparison and to confirm microarray results, semiquantitative RT-PCR for selected genes was also performed.

RESULTS

The immunosuppressive drugs significantly increased expression of two genes--calpactin 1 light chain and guanine nucleotide-binding protein alpha stimulating activity polypeptide (GNAS)--in the ganglia of uninfected mice compared with untreated, uninfected mice. Ten genes were shown to be significantly increased in the latent TGs from mice treated with the immunosuppressants compared with latently infected untreated mice. These genes were prostaglandin E2 receptor EP4 subtype (PTGER4), insulin promoter factor 1 (IPF1), glutathione S-transferase mu2, cyclin D2, peripherin, plasma glutathione peroxidase, methyl CpG-binding protein 2, retinal S-antigen, ErbB2 protooncogene, and GNAS. Eight genes were shown to be significantly decreased in the HSV-1 latent TGs treated with the drugs compared with untreated latent mice. These genes were peripheral myelin protein 22, decorin, transcription factor AP-1, dystroglycan 1, myelin protein zero, mitogen-activated protein kinase 3, prothymosin beta4, and brain lipid-binding protein. The results obtained by semiquantitative RT-PCR results were similar to those obtained by microarray analysis. Six hours after heat stress, the genes whose expression was altered included the FK506-binding protein gene (decreased), the T-complex protein 1alpha subunit gene (increased), and the 94-kDa glucose-regulated protein gene (increased in uninfected TG, decreased in infected TG). Heat stress increased expression of the DNA excision repair protein ERCC5 gene 24 hours after the treatment. Genes previously reported to exhibit increased transcription 1 hour after heat stress did not continue to show significant transcriptional activation at 6 or 24 hours.

CONCLUSIONS

Those genes whose expression is altered by immunosuppressive drug treatment may play an important role in ocular HSV-1 recurrence. Changes in gene expression in the prostaglandin pathway, a transcription factor, and an enzyme in the cell cycle are considered of special importance for HSV-1 reactivation by immunosuppression. Altered gene expression at 6 and 24 hours after heat stress was different from previously reported changes in gene expression 1 hour after hyperthermia in HSV-1 latently infected mice.

γ-Herpesvirus neoplasia: A growing role for COX-2

Both human gamma-herpesviruses, Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) induce neoplasia. Burkitt's and Hodgkin's lymphomas harbor EBV sequences, while KSHV has been associated with Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric castleman's disease (MCD). Each of these gamma-herpesvirus-associated malignancies displays typical characteristics of neoplasia, such as angiogenesis and cell survival. One enzyme commonly overexpressed in breast, prostate, and colon cancers is cyclooxygenase-2 (COX-2). Recently, COX-2 overexpression has been reported in herpesvirus infections in vitro. This review will outline potential mechanisms by which COX-2 may participate in herpesvirus-induced neoplasia.

Transactivator protein BICP0 of bovine herpesvirus 1 (BHV-1) is blocked by prostaglandin D2 (PGD2), which points to a mechanism for PGD2-mediated inhibition of BHV-1 replication

The immediate-early protein, BICP0, of bovine herpesvirus 1 (BHV-1) transactivates a variety of viral and cellular genes. In a yeast two-hybrid cDNA library screening, we found that lipocalin-type prostaglandin D synthase, which catalyzes the production of prostaglandin D(2) (PGD(2)), is a cellular target of BICP0. We observed that, during wild-type BHV-1 infection, PGD(2) levels were increased intracellularly and decreased in the medium. These effects were absent upon infection with recombinant BHV-1 expressing beta-galactosidase instead of BICP0 (A2G2). Transient-expression assays showed that BICP0 alone caused a significant increase in PGD(2) levels in the cell. PGD(2) repressed BHV-1 replication in cultured cells. Antiviral activities of prostaglandins have been documented long ago, but their mode of action remains to be clarified. Here we provide evidence that PGD(2) impairs the transactivation ability of BICP0 that is necessary for efficient virus replication.

Latent herpes simplex virus infection of sensory neurons alters neuronal gene expression

The persistence of herpes simplex virus (HSV) and the diseases that it causes in the human population can be attributed to the maintenance of a latent infection within neurons in sensory ganglia. Little is known about the effects of latent infection on the host neuron. We have addressed the question of whether latent HSV infection affects neuronal gene expression by using microarray transcript profiling of host gene expression in ganglia from latently infected versus mock-infected mouse trigeminal ganglia. (33)P-labeled cDNA probes from pooled ganglia harvested at 30 days postinfection or post-mock infection were hybridized to nylon arrays printed with 2,556 mouse genes. Signal intensities were acquired by phosphorimager. Mean intensities (n = 4 replicates in each of three independent experiments) of signals from mock-infected versus latently infected ganglia were compared by using a variant of Student's t test. We identified significant changes in the expression of mouse neuronal genes, including several with roles in gene expression, such as the Clk2 gene, and neurotransmission, such as genes encoding potassium voltage-gated channels and a muscarinic acetylcholine receptor. We confirmed the neuronal localization of some of these transcripts by using in situ hybridization. To validate the microarray results, we performed real-time reverse transcriptase PCR analyses for a selection of the genes. These studies demonstrate that latent HSV infection can alter neuronal gene expression and might provide a new mechanism for how persistent viral infection can cause chronic disease.

Changes in gene expression in latent HSV-1-infected rabbit trigeminal ganglia following epinephrine iontophoresis

PURPOSE

The aim of the present study was to identify the genes that express in the nervous system when herpes simplex virus type 1 (HSV-1) reactivates from latency by using subtraction cloning following epinephrine iontophoresis.

METHODS

The corneas of New Zealand White rabbits (2 to 2.5 kg) were topically inoculated with 5 x 10(5) PFU of plaque-purified HSV-1 strain McKrae. Corneal infection was monitored by slit lamp examination (SLE) on days 3-7 after infection. At 30 d post-infection, eyes were assessed for infectious virus by ocular swabs. Disappearance of virus in ocular swabs signified latency for HSV-1. Latently-infected rabbits were subjected to transcorneal iontophoresis. The messenger RNA (mRNA) was isolated from the trigeminal ganglia and used for subtraction cloning and subtraction library synthesis.

RESULTS

Our results indicate 18 genes with increased expression and 6 genes with decreased levels. Northern blot analysis revealed that genes for OX-40 ligand, MHC class II HLA-DR-alpha and beta-microglobulin showed predominant increase followed by tyrosine 3'-monooxygenase, proteolipid protein, tyrosine beta, and apolipoprotein D. Genes that underwent reduced expression included cytochrome c oxidase subunit I, ATP synthase isoform, cytochrome b, ATPase 9, and at least one unidentified gene.

CONCLUSIONS

Our results, particularly the increased detection of OX-40 ligand and MHC class II-alpha and beta-2 microglobulin, support the finding that lymphocytes persist in latently-infected trigeminal ganglia (TGs). These results also suggest a role of the immune system in HSV-1 recurrences. In addition, we have detected genes associated with neuronal disorders, OX-40L, proteolipid protein, and apolipoprotein D.

Herpes simplex virus evolved to use the human defense mechanisms to establish a lifelong infection in neurons--a review and hypothesis

The review of recent studies using DNA microarrays shed new light on herpes simplex virus (HSV) replicative cycle, the response of immature dendritic cells (DCs) to pathogens and the response of neurons in trigeminal ganglia to virus reactivation. These studies provided a better understanding of the molecular biology of HSV during infection, latency and reactivation. The research on the sensory trigeminal neurons and the neuronal axons (type C fibers) that transverse the skin basal membrane, enter the skin epidermis and interact with the cell membrane of the skin resident immature DCs provided an insight on the connection between the nervous system and the host immune system. Based on these studies a hypothesis is presented suggesting that HSV evolved to use the human host defense systems (pain signals, the immune system cells and sensory neurons) to ensure its entry from the skin epithelium into the sensory neurons. Reactivated HSV in the neurons utilizes the same host defense systems to return to the skin epithelium.