Herpes simplex virus latency and the immune response

Chronic pain and infection: mechanisms, causes, conditions, treatments, and controversies

Throughout human history, infection has been the leading cause of morbidity and mortality, with pain being one of the cardinal warning signs. However, in a substantial percentage of cases, pain can persist after resolution of acute illness, manifesting as neuropathic, nociplastic (eg, fibromyalgia, irritable bowel syndrome), or nociceptive pain. Mechanisms by which acute infectious pain becomes chronic are variable and can include immunological phenomena (eg, bystander activation, molecular mimicry), direct microbe invasion, central sensitization from physical or psychological triggers, and complications from treatment. Microbes resulting in a high incidence of chronic pain include bacteria such as the Borrelia species and Mycobacterium leprae, as well as viruses such as HIV, SARS-CoV-2 and herpeses. Emerging evidence also supports an infectious cause in a subset of patients with discogenic low back pain and inflammatory bowel disease. Although antimicrobial treatment might have a role in treating chronic pain states that involve active infectious inflammatory processes, their use in chronic pain conditions resulting from autoimmune mechanisms, central sensitization and irrevocable tissue (eg, arthropathy, vasculitis) or nerve injury, are likely to cause more harm than benefit. This review focuses on the relation between infection and chronic pain, with an emphasis on common viral and bacterial causes.

Severe Coagulopathy Secondary to Fulminant Herpes Simplex Virus Hepatitis in a Severely Burned Patient: A Case Report and Review of the Literature

Fulminant hepatic failure secondary to herpes simplex virus (HSV) is a rare complication that is associated with high mortality. Here, we describe the case of a critically ill patient with severe burns and inhalation injury who developed severe coagulopathy during her hospital stay, which was later found to be caused by HSV hepatitis. In addition, we review the current literature on HSV hepatitis. Only three prior reports document liver involvement of HSV in patients with burn. Clinical symptoms, diagnostic factors, and management of HSV hepatitis in patients with burn are presented. Because of severe immunosuppression and potentially fatal nature of this infection, clinicians should have a heightened suspicion for HSV hepatitis in burn patients with HSV mucocutaneous involvement, unexplained liver dysfunction, and severe coagulopathy, and it should prompt immediate initiation of intravenous acyclovir.

Herpes Simplex Virus Type 1 infection is associated with suicidal behavior and first registered psychiatric diagnosis in a healthy population

Increasing evidence shows that latent infections and inflammation is associated with cognitive and behavioral changes in humans. This case-control study investigates the association between Herpes Simplex Virus Type 1 (HSV-1) infection and C-reactive Protein (CRP) levels, and psychiatric disorders and suicidal behavior. Public health register data from 81,912 participants in the Danish Blood Donor Study, were reviewed to identify individuals registered with an ICD-10 code of any psychiatric diagnosis, or who had attempted or committed suicide. We found 1,504 psychiatric cases and 353 suicidal cases; for all cases, controls were frequency-matched by age and sex, resulting in 5,336 participants. Plasma samples were analyzed for IgG-class antibodies against HSV-1 and CRP. HSV-1 infection was associated with suicidal behavior (odds-ratio, 1.40; 95% confidence interval [CI] 1.11-1.77). Accounting for temporality, HSV-1 infection was associated with having first psychiatric disorder after the date of blood collection (incidence rate ration, 1.44; 95% CI, 1.05-1.95). No association between CRP and psychiatric disorders or suicidal behavior was found. The finding that HSV-1 was associated with suicidal behavior and first psychiatric disorder indicates that infection may play a role in the etiology and pathogenesis of suicidal behavior and development of psychiatric disorders.

Immune characteristics correlating with HSV-1 immune control and effect of squaric acid dibutyl ester on immune characteristics of subjects with frequent herpes labialis episodes

INTRODUCTION

Differences in immune characteristics, including immune gene expression by peripheral blood mononuclear cells (PBMCs), correlating with herpes labialis and good or poor immune control of herpes simplex virus type 1 (HSV-1), and how these characteristics change after dosing with squaric acid dibutyl ester (SADBE), were investigated.

METHODS

PBMCs were collected from persons positive for IgG against HSV-1 and having frequent, infrequent, or no herpes labialis outbreaks. The PBMCs were tested for proliferation against HSV-1 and a fungal antigen (Candida) and immune gene expression in the presence of HSV-1 and Candida. On day 1 after blood collection the subjects with frequent outbreaks were dosed topically on the arm once with SADBE, and their PBMCs were collected and tested 8 weeks later.

RESULTS

Those with good immune control of their HSV-1 infection (fewer outbreaks) differ from those with poorer immune control in these ways: (1) Greater PBMC proliferation in vitro to HSV-1, HSV-1-infected cell extracts, and Candida considered together (P < 0.01). (2) Higher expression of IFNG and five other immune-related genes (P < 0.05 for each) and lower expression of IL5 and two other immune-related genes (P < 0.05 for each) in PBMCs in vitro stimulated with HSV-1 virus. The subjects with frequent outbreaks were treated once with SADBE, and 56 days later the PBMCs of these subjects differed from PBMCs from the same subjects taken on day 1 before treatment in exactly the same ways listed above as differences between those with good and poor immune control of HSV-1, and at the same levels of significance.

CONCLUSIONS

Higher IFNG and lower IL5 expression by PBMCs in the presence of HSV-1 correlate with fewer herpes labialis outbreaks, and a single topical dose of SADBE to the arm of subjects with frequent herpes labialis episodes improves immune response to HSV-1.

Herpes simplex virus 1 interferes with autophagy of murine dendritic cells and impairs their ability to stimulate CD8+ T lymphocytes

The MHC class I presentation is responsible for the presentation of viral proteins to CD8⁺ T lymphocytes and mainly depends on the classical antigen processing pathway. Recently, a second pathway involving autophagy has been implicated in this process. Here, we show an increase in the capacity of murine dendritic cells (DCs) to present viral antigens on MHC class I after infection with a mutant herpes simplex virus 1 (HSV-1-Δ34.5), lacking infected cell protein 34.5 (ICP34.5), when compared to its parental HSV-1 strain. The ICP34.5 protein counteracts host cell translational arrest and suppresses macroautophagy, and the lack of this protein resulted in a low viral protein abundance, which was processed and presented in an efficient way. Our study demonstrates an important role of autophagy in processing endogenous viral proteins in HSV-1-infected DCs.

Antiherpes virus-specific treatment and cognition in schizophrenia: a test-of-concept randomized double-blind placebo-controlled trial

OBJECTIVE

To test our hypothesis that valacyclovir, an antiherpes virus-specific medication, added to antipsychotics (APs) would improve cognitive performance and psychopathology among schizophrenia subjects exposed to neurotropic herpes simplex virus, type 1 (HSV1).

METHODS

Using a double-blind placebo-controlled design, we randomized 24 HSV1-seropositive schizophrenia subjects to receive either valacyclovir (n = 12) or placebo (n = 12) for 18 weeks in addition to stable doses of APs. Valacyclovir dose was stabilized at 1.5 g twice daily orally. At each visit, subjects were evaluated for severity of psychopathology and side effects using standardized scales and a study-specific semistructured checklist. A computerized neurocognitive battery validated on both schizophrenia and healthy subjects was administered at baseline and follow-up. Intent-to-treat analysis, using linear regression models that included all randomized subjects, were used to examine differential changes in cognition and psychopathology scores over 18 weeks between valacyclovir and placebo, accounting for placebo response.

RESULTS

Valacyclovir group improved in verbal memory, working memory, and visual object learning compared with placebo group. The effect sizes (Cohen's d) were 0.79 for working memory, 1.14 for immediate verbal memory, and 0.97 for the visual object learning. Psychotic symptom severity did not improve.

CONCLUSIONS

Supplemental valacyclovir may alleviate impairments in cognitive domains that are often observed in schizophrenia but not psychotic symptoms in those exposed to HSV1. If replicated, this approach could provide a novel strategy to treat cognitive impairments in a subgroup of schizophrenia subjects who can be reliably identified using a blood test.

Role of Us9 phosphorylation in axonal sorting and anterograde transport of pseudorabies virus

Alphaherpes viruses, such as pseudorabies virus (PRV), undergo anterograde transport in neuronal axons to facilitate anterograde spread within hosts. Axonal sorting and anterograde transport of virions is dependent on the viral membrane protein Us9, which interacts with the host motor protein Kif1A to direct transport. Us9-Kif1A interactions are necessary but not sufficient for these processes, indicating that additional cofactors or post-translational modifications are needed. In this study, we characterized two conserved serine phosphorylation sites (S51 and S53) in the PRV Us9 protein that are necessary for anterograde spread in vivo. We assessed the subcellular localization of phospho-Us9 subspecies during infection of neurons and found that the phospho-form is detectable on the majority, but not all, of axonal vesicles containing Us9 protein. In biochemical assays, phospho-Us9 was enriched in lipid raft membrane microdomains, though Us9 phosphorylation did not require prior lipid raft association. During infections of chambered neuronal cultures, we observed only a modest reduction in anterograde spread capacity for diserine mutant Us9, and no defect for monoserine mutants. Conversely, mutation of the kinase recognition sequence residues adjacent to the phosphorylation sites completely abrogated anterograde spread. In live-cell imaging analyses, anterograde transport of virions was reduced during infection with a recombinant PRV strain expressing GFP-tagged diserine mutant Us9. Phosphorylation was not required for Us9-Kif1A interaction, suggesting that Us9-Kif1A binding is a distinct step from the activation and/or stabilization of the transport complex. Taken together, our findings indicate that, while not essential, Us9 phosphorylation enhances Us9-Kif1A-based transport of virions in axons to modulate the overall efficiency of long-distance anterograde spread of infection.

Bovine herpesvirus-5 infection in a rabbit experimental model: immunohistochemical study of the cellular response in the CNS

Since little information is available regarding cellular antigen mapping and the involvement of non-neuronal cells in the pathogenesis of bovine herpesvirus type 5 (BHV-5) infection, it were determined the BHV-5 distribution, the astrocytic reactivity, the involvement of lymphocytes and the presence of matrix metalloproteinase (MMP)-9 in the brain of rabbits experimentally infected with BHV-5. Twelve New Zealand rabbits that were seronegative for BHV-5 were used for virus inoculation, and five rabbits were used as mock-infected controls. The rabbits were kept in separate areas and were inoculated intranasally with 500 μl of virus suspension (EVI 88 Brazilian isolate) into each nostril (virus titer, 10(7.5) TCID50). Control rabbits were inoculated with the same volume of minimum essential medium. Five days before virus inoculation, the rabbits were submitted to daily administration of dexamethasone. After virus inoculation, the rabbits were monitored clinically on a daily basis. Seven rabbits showed respiratory symptoms and four animals exhibited neurological symptoms. Tissue sections were collected for histological examination and immunohistochemistry to examine BHV-5 antigens, astrocytes, T and B lymphocytes and MMP-9. By means of immunohistochemical and PCR methods, BHV-5 was detected in the entire brain of the animals which presented with neurological symptoms, especially in the trigeminal ganglion and cerebral cortices. Furthermore, BHV-5 antigens were detected in neurons and/or other non-neural cells. In addition to the neurons, most infiltrating CD3 T lymphocytes observed in these areas were positive for MMP-9 and also for BHV-5 antigen. These infected cells might contribute to the spread of the virus to the rabbit brain along the trigeminal ganglia and olfactory nerve pathways.

Exposure to herpes simplex virus type 1 and cognitive impairments in individuals with schizophrenia

Latent infection with neurotropic herpes viruses, such as herpes simplex virus, type 1 (HSV1), has been generally considered benign in most immunocompetent individuals except for rare cases of encephalitis. However, several recent studies have shown impaired cognitive functions among individuals with schizophrenia exposed to HSV1 compared with schizophrenia patients not exposed to HSV1. Such impairments are robust and are prominently observed in working memory, verbal memory, and executive functions. Brain regions that play a key role in the regulation of these domains have shown smaller volumes, along with correlation between these morphometric changes and cognitive impairments in schizophrenia. One study noted temporal decline in executive function and gray matter loss among HSV1-exposed first-episode antipsychotic-naïve schizophrenia patients. Furthermore, a proof-of-concept double-blind placebo-controlled trial indicated improvement in cognitive performance following supplemental anti-herpes-specific medication among HSV1 seropositive schizophrenia patients. Cross-sectional studies have also identified an association between HSV1 exposure and lesser degrees of cognitive impairment among healthy control individuals and patients with bipolar disorder. These studies fulfill several Bradford-Hill criteria, suggesting etiological links between HSV1 exposure and cognitive impairment. Exposure to other human herpes viruses such as cytomegalovirus and herpes simplex virus type 2 (HSV2) may also be associated with cognitive impairment, but the data are less consistent. These studies are reviewed critically and further lines of enquiry recommended. The results are important from a public health perspective, as HSV1 exposure is highly prevalent in many populations.

LEAPS therapeutic vaccines as antigen specific suppressors of inflammation in infectious and autoimmune diseases

The L.E.A.P.S.(™) (Ligand Epitope Antigen Presentation System) technology platform has been used to develop immunoprotective and immunomodulating small peptide vaccines for infectious and autoimmune diseases. Several products are currently in various stages of development, at the pre-clinical stage (in animal challenge efficacy studies). Vaccine peptides can elicit protection of animals from lethal viral (herpes simplex virus [HSV-1] and influenza A) infection or can block the progression of autoimmune diseases (e.g. rheumatoid arthritis as in the collagen induced arthritis (CIA] or experimental autoimmune myocarditis (EAM) models). L.E.A.P.S. technology is a novel T-cell immunization technology that enables the design and synthesis of non-recombinant, proprietary peptide immunogens. Combination of a small peptide that activates the immune system with another small peptide from a disease-related protein, thus a conjugate containing both an Immune Cell Binding Ligand (ICBL) and a disease specific epitope, which allows the L.E.A.P.S. vaccines to activate precursors to differentiate and become more mature cells that can initiate and direct appropriate T cell responses. As such, readily synthesized, defined immunogens can be prepared to different diseases and are likely to elicit protection or therapy as applicable in humans as they are in mice. L.E.A.P.S. vaccines have promise for the treatment of rheumatoid arthritis and other inflammatory diseases and for infections, such as influenza and HSV1. The protective responses are characterized as Th1 immune and immunomodulatory responses with increased IL-12p70 and IFN-γ (Th1 cytokines) but reduced inflammatory cytokines TNF-α, IL-1 and IL-17 (Th2 and Th17 cytokines) and concomitant changes in antibody subtypes. LEAPS immunogens have been used directly in vivo or as ex vivo activators of DC which are then administered to the host.

Pathogenesis of herpes stromal keratitis--a focus on corneal neovascularization

The cornea is a complex sensory organ that must maintain its transparency for optimal vision. Infections such as with herpes simplex virus can result in blinding immunoinflammatory reactions referred to as herpes stromal keratitis (HSK). In this review we discuss the pathogenesis of HSK referring to work mainly done using animal model systems. We briefly discuss the role of multiple cell types and soluble mediators but focus on the critical role of corneal vascularization (CV) in contributing to corneal damage. We describe how VEGF and other angiogenic molecules are induced following infection and discuss the many ways by which CV can be controlled. Speculations are made regarding future approaches that could improve the management of HSK.

Making the case: married versus separate models of alphaherpes virus anterograde transport in axons

Alphaherpesvirus virions infect neurons and are transported in axons for long distance spread within the host nervous system. The assembly state of newly made herpesvirus particles during anterograde transport in axons is an essential question in alphaherpesvirus biology. The structure of the particle has remained both elusive and controversial for the past two decades, with conflicting evidence from EM, immunofluorescence, and live cell imaging studies. Two opposing models have been proposed-the Married and Separate Models. Under the Married Model, infectious virions are assembled in the neuronal cell body before sorting into axons and then traffic inside a transport vesicle. Conversely, the Separate Model postulates that vesicles containing viral membrane proteins are sorted into axons independent of capsids, with final assembly of mature virions occurring at a distant egress site. Recently, a complementary series of studies employing high-resolution EM and live cell fluorescence microscopy have provided evidence consistent with the Married Model, whereas other studies offer evidence supporting the Separate Model. In this review, we compare and discuss the published data and attempt to reconcile divergent findings and interpretations as they relate to these models.

Additive effects of elevated C-reactive protein and exposure to Herpes Simplex Virus type 1 on cognitive impairment in individuals with schizophrenia

OBJECTIVES

We investigated the effect of elevated levels of C-reactive protein (CRP) and exposure to Herpes simplex virus type 1 (HSV-1) on the severity of cognitive impairment in individuals with schizophrenia.

METHODS

We measured the levels of CRP and of antibodies to HSV-1 in serum samples from 588 individuals with schizophrenia by enzyme immunoassay tests. Cognitive functioning was measured with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and psychiatric symptoms with the Positive and Negative Syndrome Scale (PANSS). The effects of HSV1 and CRP on cognitive functioning were analyzed with linear and logistic regression analyses adjusting for demographic and clinical variables.

RESULTS

The individuals with elevated CRP levels and HSV-1 seropositivity had lower RBANS cognitive scores. The strongest effect was found in individuals who had both serological evidence of HSV-1 exposure and elevated levels of CRP. These individuals had odds of 2.35 to have an RBANS Total score<=60 as compared to individuals who were HSV-1 seronegative and who did not have elevated levels of CRP (p=.002). The risks of decreased cognitive functioning associated with HSV-1 exposure and elevated levels of CRP were independent and additive. There was no effect of HSV-1 exposure and CRP levels on the severity of symptoms as measured by the PANSS (all p>.5).

CONCLUSIONS

Elevated levels of CRP and exposure to HSV-1 are associated with the severity of cognitive impairment in schizophrenia. These findings indicate that infection and inflammation may play a major role in the cognitive deficits associated with schizophrenia.

Influence of galectin-9/Tim-3 interaction on herpes simplex virus-1 latency

After HSV-1 infection, CD8(+) T cells accumulate in the trigeminal ganglion (TG) and participate in the maintenance of latency. However, the mechanisms underlying intermittent virus reactivation are poorly understood. In this study, we demonstrate the role of an inhibitory interaction between T cell Ig and mucin domain-containing molecule 3 (Tim-3)-expressing CD8(+) T cells and galectin 9 (Gal-9) that could influence HSV-1 latency and reactivation. Accordingly, we show that most K(b)-gB tetramer-specific CD8(+) T cells in the TG of HSV-1-infected mice express Tim-3, a molecule that delivers negative signals to CD8(+) T cells upon engagement of its ligand Gal-9. Gal-9 was also upregulated in the TG when replicating virus was present as well during latency. This could set the stage for Gal-9/Tim-3 interaction, and this inhibitory interaction was responsible for reduced CD8(+) T cell effector function in wild-type mice. Additionally, TG cell cultures exposed to recombinant Gal-9 in the latent phase caused apoptosis of most CD8(+) T cells. Furthermore, Gal-9 knockout TG cultures showed delayed and reduced viral reactivation as compared with wild-type cultures, demonstrating the greater efficiency of CD8(+) T cells to inhibit virus reactivation in the absence of Gal-9. Moreover, the addition of recombinant Gal-9 to ex vivo TG cultures induced enhanced viral reactivation compared with untreated controls. Our results demonstrate that the host homeostatic mechanism mediated by Gal-9/Tim-3 interaction on CD8(+) T cells can influence the outcome of HSV-1 latent infection, and manipulating Gal-9 signals might represent therapeutic means to inhibit HSV-1 reactivation from latency.

Overwhelming disseminated herpes simplex virus type 2 infection in a patient with severe burn injury: case report and literature review

Viral-mediated organ disease is an infrequent but recognized complication of severe burn injury. This occurs primarily because of herpes family viruses such as cytomegalovirus, herpes simplex virus (HSV), and Epstein-Barr virus given their ability to establish lifelong latency after primary infection and reactivate in the setting of altered immune function. In this report, we describe a severely burned patient who succumbed to fulminant HSV-2 pneumonitis and hepatitis, and summarize the existing literature on HSV infections in this unique patient population. To our knowledge, this is the first report of disseminated visceral HSV-2 infection in a burn patient in the medical literature.

Serological evidence of exposure to Herpes Simplex Virus type 1 is associated with cognitive deficits in the CATIE schizophrenia sample

Cognitive impairment is a core feature of schizophrenia. Previous studies have indicated that exposure to neurotropic infectious agents such as Herpes Simplex Virus type 1 may contribute to cognitive deficits and neuroanatomical abnormalities in individuals with schizophrenia. We examined the association between exposure to neurotropic infectious agents and cognitive function in 1308 participants in the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial. This sample included all of the individuals in the CATIE trial for whom baseline blood samples were available. Cognition was evaluated at baseline by a test battery which yielded composite scores in the domains of processing speed, verbal memory, vigilance, reasoning, and working memory as well as a summary neurocognitive score. Solid phase immunoassay techniques were used to measure IgG class antibodies to Herpes Simplex Virus type 1 (HSV-1), Herpes Simplex Virus type 2 (HSV-2), Cytomegalovirus (CMV), and to Toxoplasma gondii (T gondii) in the sera of the study individuals. We found a significant association between the neurocognitive summary score and antibodies to HSV-1 but not to HSV-2, CMV, or T. gondii. There was also a significant association between HSV-1 exposure and the Verbal Memory, Vigilance, and Processing Speed composite scores. HSV-1 may modulate the neurocognitive function of individuals with schizophrenia through its ability to establish latency in the central nervous system and undergo periodic reactivation. A better understanding of the role of HSV-1 may lead to better methods of treatment for the cognitive impairments associated with schizophrenia.

HSV as a vector in vaccine development and gene therapy

The very deep knowledge acquired on the genetics and molecular biology of herpes simplex virus (HSV), major human pathogen whose lifestyle is based on a long-term dual interaction with the infected host characterized by the existence of lytic and latent infections, has allowed the development of potential vectors for several applications in human healthcare. These include delivery and expression of human genes to cells of the nervous system, selective destruction of cancer cells, prophylaxis against infection with HSV or other infectious diseases and targeted infection of specific tissues or organs. Three different classes of vectors can be derived from HSV-1: replication-competent attenuated vectors, replication-incompetent recombinant vectors and defective helper-dependent vectors known as amplicons. This chapter highlights the current knowledge concerning design, construction and recent applications, as well as the potential and current limitations of the three different classes of HSV-1-based vectors.

Herpes simplex virus type I infection of mature dendritic cells leads to reduced LMP7-mRNA-expression levels

Mature dendritic cells (mDCs) are the most potent antigen presenting cells within the human immune system known today. However, several viruses, including herpes simplex virus type 1 (HSV-1) have developed numerous immune escape mechanisms, such as the avoidance of peptide presentation through the major histocompatibility complex (MHC) class I to CD8(+) cytotoxic T-cells. Within the MHC class I pathway, the majority of antigenic peptides are generated by the proteasome, a multicatalytic protease complex. Upon exposure to IFN-gamma, the constitutive proteasome is partially replaced by the immunoproteasome, which contains the IFN-gamma-inducible subunits LMP2, MECL1 and LMP7. In this study, we report the downregulation of LMP7 on mRNA level in HSV-1 infected mDCs. Interestingly, this reduction was not vhs-mediated since using a virus strain lacking the vhs gene we obtained similar results. However, on protein level, LMP7-expression was not affected, which is probably due the high stability of the LMP7 protein. Also the incorporation of LMP7 into the immunoproteasome was not affected by HSV-1. However, for the in vivo situation, in which DC reside for a prolonged time period in peripheral tissues, the reduced LMP7-mRNA level could be of biological importance, since the virus could escape/hide from immune system of the host and establish latency processes.

Infection of mature dendritic cells with herpes simplex virus type 1 interferes with the interferon signaling pathway

It has been shown that herpes simplex virus type 1 (HSV-1) blocks specific immune responses by various mechanisms. Cell lines infected with HSV-1 for instance show a severe impairment of the interferon-gamma (IFN-gamma)-induced signal transducer and activator of transcription 1 (STAT1) signaling pathway. Thus, we examined the influence of HSV-1 infection on IFN-gamma signal transduction in mature dendritic cells (mDCs). In this study, we report the down-regulation of the IFN-gamma receptor alpha chain (IFNGR1) at the mRNA level in HSV-1 infected mDCs. As a consequence, the expression of the IFNGR1 subunit on the cell surface of the infected cell was strongly reduced. Furthermore, we were able to show the inhibition of STAT1 phosphorylation following HSV-1 infection in mDCs, while protein levels of STAT1 remained constant. As a direct downstream effect of STAT1 phosphorylation, the activation of the transcription factor IRF-1 was also clearly inhibited and could no longer be induced by the addition of IFN-gamma. Additional experiments using a virus strain lacking the vhs gene suggested that the mutant virus is more sensitive to IFN-gamma as STAT1 signaling was inhibited to a lesser extent. Infection with a UV-inactivated, replication incompetent virus did not influence the STAT1 signaling pathway at all. In conclusion, we show that HSV-1 blocks IFN-gamma signaling in mDCs, which requires viral gene expression and involves the viral protein vhs.

Brain morphological changes associated with exposure to HSV1 in first-episode schizophrenia

Infectious agents have been proposed as one of the risk factors for schizophrenia. However, the data on the association of infectious agents with in vivo brain changes are scant. We evaluated the association of serological evidence of exposure to herpes simplex virus 1 (HSV1) with in vivo brain structural variations among first-episode antipsychotic-naive schizophrenia/schizoaffective disorder patients and control subjects. We assayed HSV1 immunoglobulin G (IgG) antibody in serum samples from 30 patients and 44 healthy subjects and obtained structural magnetic resonance imaging scans from the same individuals. There were proportionately more patients with elevated HSV1 antibody ratios than healthy comparison subjects (chi2=3.98, 1 df, P=0.046) and patients had significantly higher HSV1 IgG antibody ratios compared with healthy subjects. Using optimized voxel-based morphometry, we examined diagnosis by HSV1 serological status interaction followed by within- and between-group comparison across the serological status. We observed a diagnosis by HSV1 serological status interaction and a significant main effect of HSV1 serological status in the prefrontal gray matter. Patients exposed to HSV1 had decreased gray matter in Brodmann area 9 (dorsolateral prefrontal cortex) and 32 (anterior cingulate cortex) compared with patients without serological evidence of exposure to HSV1. HSV1-associated differences in brain structure were not detected among healthy subjects. These findings suggest that HSV1 exposure in schizophrenia is associated with specific regional gray matter differences that may not be attributable to medications, illness chronicity or comorbid substance use. This study provides suggestive evidence for a link between HSV1 exposure and some of the cerebral morphological changes often reported in schizophrenia.

Anatomical mapping of human herpesvirus reservoirs of infection

Following primary infection, all eight human herpesviruses persist lifelong in the human host. However, a mapping of all anatomic sites of human herpesvirus persistence is lacking. Fresh tissue specimens representing approximately 40 major anatomic sites from eight autopsies were screened using a recently developed real-time PCR method for detection of all eight human herpesviruses. Patients with evidence of active herpesvirus infection (herpes simplex 1 (HSV-1), herpes simplex 2 (HSV-2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpesvirus 6 (HHV-6), herpesvirus 7 (HHV-7), and herpesvirus 8 (HHV-8)) at the time of death were excluded to avoid detection of widely disseminated infection. Despite this precaution, widespread HSV-1 positivity (with blood positivity) was detected in one case-an elderly male who died of cardiac arrest. In a middle-aged male with HIV-AIDS, HSV-1 was found in neural and pharyngeal tissues, skin, cartilage, bone, and urinary bladder, whereas in two other cases, HSV-1 was restricted to neural tissues. HSV-2 was detected in a single site, the anus, in the male with HIV-AIDS. VZV was detected only twice, once in the adrenal gland and once in the small intestine. CMV was detected in three cases, most commonly in nasal mucosa, trachea, thyroid, intestine, and liver. EBV was detected in all eight cases, especially in nasal mucosa, tonsil, spleen, lymph node, tongue, and intestine, but in only two of six whole-blood specimens. HHV-6, like EBV, was detected in all eight cases, most commonly in salivary glands, thyroid, stomach, intestines, liver, and pancreas. HHV-7, like EBV and HHV-6, was detected in all eight cases, most commonly in salivary glands, tonsil, lymph nodes, and bone marrow. HHV-8 was detected in only two sites (both lymph nodes) from two cases. Herpesviruses were detected in three of six whole-blood specimens, including HSV-1, EBV, HHV-6, and HHV-7. These results represent the most comprehensive mapping of herpesvirus tissue distribution in humans reported to date.

Qa-1b and CD94-NKG2a interaction regulate cytolytic activity of herpes simplex virus-specific memory CD8+ T cells in the latently infected trigeminal ganglia

After ocular infection, HSV-specific CD8+ T cells migrate to and are specifically retained in the ophthalmic branch of the trigeminal ganglia (TG) even at the time when replicating virus is no longer evident. Virus-specific CD8+ T cells maintain an activation phenotype and secrete IFN-gamma in the latent TG. In this report we demonstrated that activated virus-specific memory CD8+ T cells, although potentially cytolytic, also expressed the CD94-NK cell receptor subfamily G2a inhibitory molecule and were unable to exert cytotoxicity when engaged by Qa-1b expressing targets. Interestingly, many neurons in the latent TG expressed Qa-1b, and blocking of Qa-1b/CD94-NKG2a interaction in an ex vivo TG culture resulted in neuronal cell lysis. The expression of the inhibitory CD94-NKG2a molecule could be induced by TGF-beta1, which was shown to present as a bioactive molecule in the latent TG. Additionally, CD4+ forkhead/winged helix transcription factor 3+ T cells were also determined in the latent TG. Our results demonstrate the operation of a regulatory system in vivo that serves to protect irreplaceable neurons from destruction by the immune system.

MMTV accessory factor Naf affects cellular gene expression

Mouse mammary tumour virus (MMTV) encodes a viral superantigen (Sag) and a negative acting factor (Naf) which share parts of their coding sequence. Using 2-dimensional gel electrophoresis (2D-DIGE), we could show that at least 10 different cellular proteins were differentially expressed in Naf positive cells. Also, luciferase reporter expression was down-regulated in Naf expressing cells independent of the promoter used and further experiments suggested that this effect was due in part to a decrease in cellular growth rates. Although in Naf positive cells expression of the major sag containing transcript was strongly induced by the synthetic glucocorticoid dexamethasone, the hormone analogue neither influenced luciferase expression nor mRNA expression of selected cellular proteins identified by 2D-DIGE. Taken together, these data support the previous finding that Naf and Sag have separable activities and suggest that Naf may play a role in modulating host cell gene expression during MMTV infection.

Infection of mature dendritic cells with herpes simplex virus type 1 dramatically reduces lymphoid chemokine-mediated migration

Herpes simplex virus type 1 (HSV-1) is able to establish latency in infected individuals. In order to characterize potential new immune-escape mechanisms, mature dendritic cells (DCs) were infected with HSV-1 and total cellular RNA was isolated from infected and mock-infected populations at different time points. RNA profiling on Affymetrix Human Genome U133A arrays demonstrated a dramatic downregulation of the migration-mediating surface molecules CCR7 and CXCR4, an observation that was further confirmed by RT-PCR and fluorescence-activated cell sorting analyses. Furthermore, migration assays revealed that, upon infection of mature DCs, CCR7- and CXCR4-mediated migration towards the corresponding CCL19 and CXCL12 chemokine gradients was strongly reduced. It is noteworthy that the infection of immature DCs with HSV-1 prior to maturation led to a failure of CCR7 and CXCR4 upregulation during DC maturation and, as a consequence, also induced a block in their migratory capacity. Additional migration assays with a Δvhs mutant virus lacking the virion host shutoff (vhs) gene, which is known to degrade cellular mRNAs, suggested a vhs-independent mechanism. These results indicate that HSV-1-infected mature DCs are limited in their capacity to migrate to secondary lymphoid organs, the areas of antigen presentation and T-cell stimulation, thus inhibiting an antiviral immune response. This represents a novel, previously unrecognized mechanism for HSV-1 to escape the human immune system.

Severe herpes virus (HSV-2) infection in two patients with myelodysplasia and undetectable NK cells and plasmacytoid dendritic cells in the blood

BACKGROUND

How the immune system contains herpes simplex virus (HSV) infections is partly understood. T cells from infected persons proliferate in response to HSV antigens in vitro and may control local relapse rather than primary infection. NK cells have been involved in the control of experimental infections. A potentially important, as yet unexplored, population of interest might be the plasmacytoid dendritic cells (PDC), which contrary to monocytes, produce very high amounts of the major antiviral molecules, type-I interferon (IFN) following interaction with HSV.

OBJECTIVES

Measure type-I IFN production, PDC, and NK cells in patients with unusually severe HSV infections.

STUDY DESIGN

Two female patients of 33- and 50-year-old, respectively were referred because of severe disseminated HSV2 infection and myelodysplastic marrow. One patient had leukaemia and a primary HSV2 infection whereas the other had systemic lupus erythematosus (SLE) and a chronic HSV2 infection. The following studies were performed at various time points over 18 months: analysis of the lymphocytes and PDC subsets phenotype, lymphocyte proliferation assays to recall antigens; generation of NK cells in cultures, and production of type-I IFN in serum and by HSV-infected and by sendai virus (SV)-infected blood cells.

RESULTS AND CONCLUSIONS

PDC and NK cells were undetectable in the blood of both patients and NK cells could not be generated in culture at the time of ongoing infection. PBMC failed to produce IFN after infection with HSV contrasting with a normal T cell proliferation to HSV antigens in patient 1. Our observation suggests that innate immunity, through NK cells and PDC may control HSV infections, and together with IFN-producing capacity, should be investigated in patients with unusually severe HSV infections.

Infection with herpes simplex virus type 1 is associated with cognitive deficits in bipolar disorder

BACKGROUND

In a previous investigation, we found an association between reduced cognitive functioning and the prevalence of antibodies to herpes simplex virus type 1 in individuals with schizophrenia. The current study was undertaken to determine if this association also occurs in individuals with bipolar disorder.

METHODS

Cognitive functioning and serologic evidence of infection with potentially neurotropic herpesviruses were measured in 117 individuals with bipolar disorder and in 100 individuals without a history of psychiatric disorder. Cognitive functioning was evaluated with the Repeatable Battery for the Assessment of Neuropsychological Status. For each patient, serologic evidence of infection was ascertained by the measurement of serum immunoglobulin G class antibodies with specificities for six potentially neurotropic human herpesviruses. The association between serologic evidence of herpesvirus infection and cognitive functioning was analyzed by univariate analyses, as well as multivariate analyses that included demographic and clinical factors associated with cognitive functioning.

RESULTS

Serologic evidence of infection with herpes simplex virus type 1 was an independent predictor of decreased cognitive functioning in the individuals with bipolar disorder (F = 20.5, p <.0001). Discriminant function analysis indicated that most of the difference in cognitive functioning between individuals who were antibody positive and antibody negative for herpes simplex virus type 1 could be attributed to immediate verbal memory (F = 12.07, p <.001). There was no significant association between cognitive functioning and the other human herpesviruses. No association between antibodies to herpesviruses and cognitive functioning was found in the control individuals without a history of psychiatric disorder.

CONCLUSIONS

Serologic evidence of herpes simplex virus type 1 infection is associated with cognitive impairment in individuals with bipolar disorder.

The herpes simplex virus-1 Us3 protein kinase blocks CD8T cell lysis by preventing the cleavage of Bid by granzyme B

The Us3 kinase is part of the antiapoptotic arsenal that salvages herpes simplex virus (HSV)-1-infected cells from damage caused by different stimuli. We demonstrate that Us3 protects HSV-1-infected cells from lysis by MHC class I-restricted CD8T cells without affecting antigen presentation. Expression of Us3 was associated with inhibition of caspase activation and reduced cleavage of the proapoptotic protein Bid. Recombinant granzyme B (GrB) failed to cleave Bid in cytosolic extracts from Us3 positive cells, while recombinant Bid served as substrate for Us3 phosphorylation, suggesting that modification of Bid by Us3 blocks its processing by GrB. Our data illustrate a new strategy of viral escape, where modification of a cellular proapoptotic substrate may prevent lysis of the infected cells without affecting other T-cell functions.

Cross-presentation of cell-associated antigens by dendritic cells

There is a strict requirement for professional antigen-presenting cells (APCs) in the generation of immunity toward most viruses. Exogenous pathways of MHC class I-restricted antigen presentation play an important role in the generation of antiviral immunity, particularly in the immune surveillance of virus-infected tissues of nonhematopoietic origin, and to bypass the detrimental effects of direct virus infection on professional APCs. The mechanisms underlying generation of antiviral immunity under these circumstances are discussed.

Herpes viruses hedge their bets

Static latency is the hallmark of all herpes viruses. The varicella zoster virus, for instance, causes varicella (chickenpox), and after a latent phase of between 5 and 40 years, it can give rise to herpes zoster (shingles). This latency and the subsequent reactivation has intrigued and puzzled virologists. Although several factors have been suggested, it is unknown what triggers reactivation. However, latency can be explained with a simple evolutionary model. Here, we demonstrate that a simple, yet efficient, bet-hedging strategy might have evolved in a number of viruses, especially those belonging to the herpes virus family and most importantly in varicella zoster virus. We show that the evolution of latency can be explained by the population dynamics of infectious diseases in fluctuating host populations.

Primary infection, latency, and reactivation of bovine herpesvirus type 5 in the bovine nervous system

Bovine herpesvirus type 5 (BHV-5) infection in calves causes meningoencephalitis, a fatal disease highly prevalent in South America. To study the pathogenesis of BHV-5 infection in cattle, 12 calves (group 1: acute infection) and 11 calves (group 2: latent infection) were intranasally inoculated with an Argentinean BHV-5 isolate at 10(8) and 10(4.7) tissue culture infective doses, respectively; six calves (control group) were mock infected. At 3 months postinoculation, all of the calves in group 2 and three calves in group 3 were given dexamethasone to reactivate the virus. The animals were euthanatized between days 6 and 17 postinoculation (group 1) and between days 6 and 16 postreactivation (group 2). Seventy-five percent and 91% of animals in groups 1 and 2, respectively, excreted BHV-5 in nasal and ocular discharges. Following dexamethasone administration, 45% of calves shed virus in both types of secretions. Spontaneous virus reactivation and shedding was observed in one calf. Neurologic signs consisting of circling, teeth grinding, ptyalism, jaw chomping, tongue protrusion, and apathy were observed in two animals in group 1 and, during the reactivation period, in four animals in group 2. Macroscopic findings consisted of softening of the cerebral tissue, meningeal hemorrhages and swelling, and edema and hemorrhages of prescapular, retropharyngeal and submandibular lymph nodes. Histologic lesions consisted of meningitis, mononuclear perivascular cuffing, neuronophagia, satellitosis, gliosis, hemorrhage, and necrosis and edema. Lesions in anterior cerebral cortex, medulla, and pons were consistently seen in all the animals of group 1. In the acutely infected animals, lesions in the diencephalon appeared at day 10 postinoculation, whereas in the latently infected calves these lesions were observed as early as at day 6 postreactivation. Latently infected animals developed lesions simultaneously in anterior cortex, medulla, pons, and diencephalon, showing a remarkable difference from the acutely infected group. Trigeminal ganglionitis appeared relatively early in animals of both groups (day 7 postinoculation in group 1 and day 8 postreactivation in group 2).

Immunologic approach to herpes simplex virus

The fundamental biological characteristic of herpes simplex virus (HSV) infection is its ability to establish latency and periodically reactivate, resulting in productive infectious virus. Recurrent HSV infections occur in spite of the presence of host immune responses to the virus. Because genital herpes is currently one of the three most prevalent sexually transmitted diseases worldwide, its potential public health impact has contributed to increased awareness in medical communities. The current state of knowledge on the immunological control of primary and recurrent HSV infections is reviewed, as well as the various immune-based therapeutic approaches to resultant disease. Finally, the potential benefit of immune response modifiers (IRMs), which have shown promise in early clinical studies, is discussed.

Interleukin-12- and gamma interferon-dependent innate immunity are essential and sufficient for long-term survival of passively immunized mice infected with herpes simplex virus type 1

Interferon (IFN) type I (alpha/beta IFN [IFN-alpha/beta]) is very important in directly controlling herpes simplex virus type I (HSV-1) replication as well as in guiding and upregulating specific immunity against this virus. By contrast, the roles of IFN type II (IFN-gamma) and antibodies in the defense against HSV-1 are not clear. Mice without a functional IFN system and no mature B and T cells (AGR mice) did not survive HSV-1 infection in the presence or absence of neutralizing antibodies to the virus. Mice without a functional IFN type I system and with no mature B and T cells (AR129 mice) were unable to control infection with as little as 10 PFU of HSV-1 strain F. By contrast, in the presence of passively administered neutralizing murine antibodies to HSV-1, some AR129 mice survived infection with up to 10(4) PFU of HSV-1. This acute immune response was dependent on the presence of interleukin-12 (IL-12) p75. Interestingly, some virus-infected mice stayed healthy for several months, at which time antibody to HSV-1 was no longer detectable. Treatment of these virus-exposed mice with dexamethasone led to death in approximately 40% of the mice. HSV-1 was found in brains of mice that did not survive dexamethasone treatment, whereas HSV-1 was absent in those that survived the treatment. We conclude that in the presence of passively administered HSV-1-specific antibodies, the IL-12-induced IFN-gamma-dependent innate immune response is able to control low doses of virus infection. Surprisingly, in a significant proportion of these mice, HSV-1 appears to persist in the absence of antibodies and specific immunity.

The immune response to ocular herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) is a prevalent microbial pathogen infecting 60% to 90% of the adult world population. The co-evolution of the virus with humans is due, in part, to adaptations that the virus has evolved to aid it in escaping immune surveillance, including the establishment of a latent infection in its human host. A latent infection allows the virus to remain in the host without inducing tissue pathology or eliciting an immune response. During the acute infection or reactivation of latent virus, the immune response is significant, which can ultimately result in corneal blindness or fatal sporadic encephalitis. In fact, HSV-1 is one of the leading causes of infectious corneal blindness in the world as a result of chronic episodes of viral reactivation leading to stromal keratitis and scarring. Significant inroads have been made in identifying key immune mediators that control ocular HSV-1 infection and potentially viral reactivation. Likewise, viral mechanisms associated with immune evasion have also been identified and will be discussed. Lastly, novel therapeutic strategies that are currently under development show promise and will be included in this review. Most investigators have taken full advantage of the murine host as a viable working in vivo model of HSV-1 due to the sensitivity and susceptibility to viral infection, ease of manipulation, and a multitude of developed probes to study changes at the cellular and molecular levels. Therefore, comments in this review will primarily be restricted to those observations pertaining to the mouse model and the assumption (however great) that similar events occur in the human condition.

Herpes simplex virus-specific immune responses in subjects with frequent and infrequent orofacial recrudescences

BACKGROUND

Following the primary infection of the orofacial region with herpes simplex virus (HSV) type 1, the virus remains latent in the ganglia for the lifetime of the host but can reactivate at intervals and cause recrudescent lesions. The frequency of these episodes varies considerably from one individual to another.

OBJECTIVES

To compare immune responses in two groups of subjects: those with frequent orofacial lesions, defined as 10 or more per year (n = 12), and those with infrequent lesions, defined as three or fewer per year (n = 20).

METHODS

Plasma and peripheral blood mononuclear cells were collected from each individual for the series of immunological tests listed in the following results section.

RESULTS

Although IgG titres specific for HSV, measured by enzyme-linked immunosorbent assay (ELISA), were not different between the two groups, there was a significantly higher HSV-specific IgE titre in the frequent group. The percentages of CD3-, CD4- and CD8-positive cells in peripheral blood, assessed by flow cytometry, and the in vitro lymphoproliferative response to the non-specific mitogen concanavalin A, did not differ between the two groups. T-cell responses to HSV were assessed by in vitro lymphoproliferation with tritiated thymidine incorporation and subsequent calculation of the stimulation index; cytokine production [interferon (IFN)-gamma and interleukin (IL)-10] into the culture supernatant as a result of the stimulation was measured by ELISAs. The mean +/- SEM stimulation index was 4.1 +/- 0.2 in the subjects with frequent lesions and 11.8 +/- 3.1 in the subjects with infrequent lesions, a difference that was significant. The mean IL-10 concentrations found in the subjects with frequent and infrequent lesions were 154 and 110 pg mL-1, respectively, a difference that did not reach significance. However, the IFN-gamma production was significantly lower in the subjects with frequent lesions compared with those with infrequent lesions: mean 835 and 1679 pg mL-1, respectively.

CONCLUSIONS

Thus, from the HSV-specific T-cell proliferation, IFN-gamma production and IgE results, patients who experience frequent recrudescences may tend towards the production of T-helper 2 cytokines in response to the virus, which may lead, in turn, to less effective control of viral replication in the periphery following reactivation from latency.

Effects of UV irradiation on skin and nonskin-associated herpes simplex virus infections in rats

Herpes simplex virus (HSV) normally causes vescular lesions on mucocutaneous surfaces but can also cause encephalitis. The virus can reactivate from the latent state in neurons to form recrudescent lesions. One common stimulus for reactivation is exposure to sunlight. In the present study, the effects of irradiating rats with suberythemal ultraviolet (UV) before or after infecting them epidermally with HSV was investigated. Preexposure to UV impaired HSV-specific cellular immune responses, as indicated by delayed type hypersensitivity (DTH) and in vitro lymphoproliferation assays. However, the number and severity of the skin lesions were not altered. In contrast, exposure after infection did not affect cellular immunity but resulted in a large increase in the severity and number of lesions. In a second series of experiments, the effects of preirradiating with UV on HSV infection was examined using a route of inoculation which was not skin-associated, namely intranasal, allowing direct non-invasive access to the nervous system. It was found that suppressed DTH resulted, together with an increase in the incidence and severity of neurological symptoms and an increased viral load in the brain. Therefore, unlike the situation in the skin, irradiation of rats before intranasal inoculation led to a suppressed immune response to HSV which correlated with increased viral load and symptoms. These results indicate that the effects of UV may be dependent on whether the animal is exposed before or after the infection, and whether the infection is skin-associated or systemic.

Why do we lack an effective vaccine against herpes simplex virus infections?

This review discusses the possible causes for the lack of an effective antiherpes vaccine. Future prospects of vaccines based on the current knowledge of immune responses to herpes viruses are discussed. It is argued that vaccines capable of expanding CD8 T-cell memory responses should be the focus of future anti-herpes simplex virus research.

Either a CD4(+)or CD8(+)T cell function is sufficient for clearance of infectious virus from trigeminal ganglia and establishment of herpes simplex virus type 1 latency in mice

Following ocular infection of normal mice, herpes simplex virus type 1 (HSV-1) establishes a latent infection in the trigeminal ganglia (TG) with the complete absence of detectable infectious virus. In this study, the role of CD4(+)and CD8(+)T cell dependent immune responses is examined in relation to clearing infectious virus from the TG following HSV-1 ocular challenge. Nude mice, which lack T cells, and MHC(o/o)mice, which lack both MHC class I and MHC class II, were challenged ocularly with wild-type HSV-1. Over 70% of the TG from mice surviving the infection contained infectious virus, indicative of a chronic infection in these TG, rather than a latent infection. No infectious virus was detected in TGs from infected C57BL/6 parental mice. Ocular challenge of CD4(o/o)A(beta(o/o, CD8(o/o)or beta(2)m(o/o)mice resulted in latent rather than chronic infection. Similarly, when C57BL/6 mice were depleted for CD4(+)or CD8(+)T cells from 4 days before ocular challenge to 26 days after ocular challenge, no free virus was detected in TGs of challenged mice. In contrast, when mice were depleted of both their CD4(+)and CD8(+)T cells, over 90% of TGs were positive for free virus, suggesting that the lack of virus clearance was due to the combined lack of both CD4(+)T cells and CD8(+)T cells (i.e. in the presence of either CD4(+)T cells or CD8(+)T cells alone all of the infectious virus was cleared and latency was established).))

Herpes simplex virus type 1 and Alzheimer's disease

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