Human herpes viruses latent infection in the nervous system

Enhancing cell-scale performance via sustained release of the varicella-zoster virus antigen from a microneedle patch under simulated microgravity

The immune system of astronauts might become weakened in the microgravity environment in space, and the dormant varicella-zoster virus (VZV) in the body might be reactivated, seriously affecting their work and safety. For working in orbit for the long term, there is currently no efficient and durable delivery system of general vaccines in a microgravity environment. Accordingly, based on the previous foundation, we designed, modified, and synthesized a biodegradable and biocompatible copolymer, polyethylene glycol-polysulfamethazine carbonate urethane (PEG-PSCU) that could be mainly adopted to fabricate a novel sustained-release microneedle (S-R MN) patch. Compared with conventional biodegradable microneedles, this S-R MN patch could not only efficiently encapsulate protein vaccines (varicella-zoster virus glycoprotein E, VZV gE) but also further prolong the release time of VZV gE in a simulated microgravity (SMG) environment. Eventually, we verified the activation of dendritic cells by VZV gE released from the S-R MN patch in an SMG environment and the positive bioeffect of activated dendritic cells on lymphocytes using an in vitro lymph node model. This study is of great significance for the exploration of long-term specific immune responses to the VZV in an SMG environment.

Binding of herpesvirus entry mediator (HVEM) and HSV-1 gD affect reactivation but not latency levels

Previously we reported that the HSV-1 latency associated transcript (LAT) specifically upregulates the cellular herpesvirus entry mediator (HVEM) but no other known HSV-1 receptors. HSV-1 glycoprotein D (gD) binds to HVEM but the effect of this interaction on latency-reactivation is not known. We found that the levels of latent viral genomes were not affected by the absence of gD binding to HVEM. However, reactivation of latent virus in trigeminal ganglia explant cultures was blocked in the absence of gD binding to HVEM. Neither differential HSV-1 replication and spread in the eye nor levels of latency influenced reactivation. Despite similar levels of latency, reactivation in the absence of gD binding to HVEM correlated with reduced T cell exhaustion. Our results indicate that HVEM-gD signaling plays a significant role in HSV-1 reactivation but not in ocular virus replication or levels of latency. The results presented here identify gD binding to HVEM as an important target that influences reactivation and survival of ganglion resident T cells but not levels of latency. This concept may also apply to other herpesviruses that engages HVEM.

Seasonal patterns in the epidemiology of Bell's palsy in Hungary

Introduction

Epidemiological data on Bell's palsy are vital for elucidating disease prevalence and enhancing therapeutic options. Our objective was to explore the prevalence and possible risk factors associated with Bell's palsy recurrence in the Clinical Center of the University of Debrecen service area. Secondary data analysis was performed using hospital discharge data, including patient information and comorbidities.

Methods

Data was obtained from the Clinical Center of the University of Debrecen, on Bell's palsy patients who were treated at the hospital between January 1, 2015 and December 31, 2021. Multiple logistic regression analysis was used to examine the factors associated with Bell's palsy recurrence.

Results

Of the 613 patients analyzed, 5.87% had recurrent paralysis, and the median time interval between episodes was 315 days. Hypertension was significantly associated with Bell's palsy recurrence. Moreover, seasonal distribution analysis revealed that the number of Bell's palsy episodes was higher in colder seasons, with spring and winter having a significantly higher number of episodes than summer and autumn.

Discussion

This study provides insights into the prevalence and associated risk factors of Bell's palsy recurrence, which could aid in its management and help reduce the long-term consequences of the disease. Further research is necessary to determine the precise mechanisms underlying these findings.

Stacking the odds: Multiple sites for HSV-1 latency

A hallmark of herpes simplex virus (HSV) infection is the establishment of latent virus in peripheral sensory ganglia of the latently infected host. We and others originally reported that the latency-associated transcript (LAT) is the only abundantly expressed viral gene in neurons within trigeminal ganglia (TG) of a latently infected host. Here, we investigated the possible contribution of various cells [i.e., B cells, dendritic cells (DCs), fibroblasts, glial cells, innate lymphoid cells (ILCs), macrophages, microglia, monocytes, natural killer cells, neurons, neutrophils, and T cells] isolated from TG of latently infected mice. Our results demonstrated that all of these cell types contain LAT, with DCs, neurons, and ILCs having the most LAT⁺ cells. These results suggest that HSV-1 can establish a quiescent/latent infection in a subset of nonneuronal cells, which enhances the chances that the virus will survive in its host.

A potent neutralizing and protective antibody against a conserved continuous epitope on HSV glycoprotein D

Infections caused by herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) remain a serious global health issue, and the medical countermeasures available thus far are limited. Virus-neutralizing monoclonal antibodies (NAbs) are crucial tools for studying host-virus interactions and designing effective vaccines, and the discovery and development of these NAbs could be one approach to treat or prevent HSV infection. Here, we report the isolation of five HSV NAbs from mice immunized with both HSV-1 and HSV-2. Among these were two antibodies that potently cross-neutralized both HSV-1 and HSV-2 with the 50% virus-inhibitory concentrations (IC₅₀) below 200 ng/ml, one of which (4A3) exhibited high potency against HSV-2, with an IC₅₀ of 59.88 ng/ml. 4A3 neutralized HSV at the prebinding stage and prevented HSV infection and cell-to-cell spread. Significantly, administration of 4A3 completely prevented weight loss and improved survival of mice challenged with a lethal dose of HSV-2. Using structure-guided molecular modeling combined with alanine-scanning mutagenesis, we observed that 4A3 bound to a highly conserved continuous epitope (residues 216 to 220) within the receptor-binding domain of glycoprotein D (gD) that is essential for viral infection and the triggering of membrane fusion. Our results provide guidance for developing NAb drugs and vaccines against HSV.

Advancing Our Understanding of Corneal Herpes Simplex Virus-1 Immune Evasion Mechanisms and Future Therapeutics

Herpes stromal keratitis (HSK) is a disease that commonly affects the cornea and external eye and is caused by Herpes Simplex Virus type 1 (HSV-1). This virus infects approximately 66% of people worldwide; however, only a small portion of these people will develop symptoms in their lifetime. There is no cure or vaccine available for HSV-1; however, there are treatments available that aim to control the inflammation caused by the virus and prevent its recurrence. While these treatments are beneficial to those suffering with HSK, there is a need for more effective treatments to minimise the need for topical steroids, which can have harmful effects, and to prevent bouts of disease reactivation, which can lead to progressive corneal scarring and visual impairment. This review details the current understanding of HSV-1 infection and discusses potential novel treatment options including microRNAs, TLRs, mAbs, and aptamers.

Absence of CD28-CTLA4-PD-L1 Costimulatory Molecules Reduces Herpes Simplex Virus 1 Reactivation

We previously reported that herpes simplex virus 1 (HSV-1) ICP22 binds to CD80 and suppresses CD80 expression in vitro and in vivo. Similar to ICP22, the cellular costimulatory molecules CD28, CTLA4, and PD-L1 also bind to CD80. In this study, we asked whether, similar to ICP22-null virus, the absence of these costimulatory molecules will reduce HSV-1 infectivity. To test our hypothesis, CD28^−/−, CD28^−/− CTLA4^−/−, PD-L1^−/−, and wild-type control BALB/c mice were ocularly infected with HSV-1 strain KOS. Levels of virus replication in the eye, corneal scarring (CS), latency, and reactivation in infected mice were determined. Expression of different genes in the trigeminal ganglia (TG) of latently infected mice was also determined by NanoString and quantitative reverse transcription-PCR (qRT-PCR). In the absence of costimulatory molecules, latency levels were higher than those in wild-type control mice, but despite higher latency, a significant number of TG from infected knockout mice did not reactivate. Reduced reactivation correlated with downregulation of 26 similar cellular genes that are associated with inflammatory signaling and innate immune responses. These results suggest that lower reactivation directly correlates with lower expression of interferon signaling. Thus, despite having different modes of actions, we identified a similar function for CD28, CTLA4, and PD-L1 in HSV-1 reactivation that is dependent on their interactions with CD80. Therefore, blocking these interactions could be a therapeutic target for HSV-1-induced reactivation.

Pressurized DNA state inside herpes capsids-A novel antiviral target

Drug resistance in viruses represents one of the major challenges of healthcare. As part of an effort to provide a treatment that avoids the possibility of drug resistance, we discovered a novel mechanism of action (MOA) and specific compounds to treat all nine human herpesviruses and animal herpesviruses. The novel MOA targets the pressurized genome state in a viral capsid, "turns off" capsid pressure, and blocks viral genome ejection into a cell nucleus, preventing viral replication. This work serves as a proof-of-concept to demonstrate the feasibility of a new antiviral target-suppressing pressure-driven viral genome ejection-that is likely impervious to developing drug resistance. This pivotal finding presents a platform for discovery of a new class of broad-spectrum treatments for herpesviruses and other viral infections with genome-pressure-dependent replication. A biophysical approach to antiviral treatment such as this is also a vital strategy to prevent the spread of emerging viruses where vaccine development is challenged by high mutation rates or other evasion mechanisms.

Pressure-driven release of viral genome into a host nucleus is a mechanism leading to herpes infection

Many viruses previously have been shown to have pressurized genomes inside their viral protein shell, termed the capsid. This pressure results from the tight confinement of negatively charged viral nucleic acids inside the capsid. However, the relevance of capsid pressure to viral infection has not been demonstrated. In this work, we show that the internal DNA pressure of tens of atmospheres inside a herpesvirus capsid powers ejection of the viral genome into a host cell nucleus. To our knowledge, this provides the first demonstration of a pressure-dependent mechanism of viral genome penetration into a host nucleus, leading to infection of eukaryotic cells.

Herpes Simplex Virus 1 Latency and the Kinetics of Reactivation Are Regulated by a Complex Network of Interactions between the Herpesvirus Entry Mediator, Its Ligands (gD, BTLA, LIGHT, and CD160), and the Latency-Associated Transcript

Recently, we reported that the herpesvirus entry mediator (HVEM; also called TNFRSF14 or CD270) is upregulated by the latency-associated transcript (LAT) of herpes simplex virus 1 (HSV-1) and that the absence of HVEM affects latency reactivation but not primary infection in ocularly infected mice. gD has been shown to bind to HVEM. LIGHT (TNFSF14), CD160, and BTLA (B- and T-lymphocyte attenuator) also interact with HVEM and can interfere with HSV gD binding. It was not known if LIGHT, CD160, or BTLA affected the level of latency reactivation in the trigeminal ganglia (TG) of latently infected mice. To address this issue, we ocularly infected LIGHT^-/-, CD160^-/-, and BTLA^-/- mice with LAT(+) and LAT(-) viruses, using similarly infected wild-type (WT) and HVEM^-/- mice as controls. The amount of latency, as determined by the levels of gB DNA in the TG of the LIGHT^-/-, CD160^-/-, and BTLA^-/- mice infected with either LAT(+) or LAT(-) viruses, was lower than that in WT mice infected with LAT(+) virus and was similar in WT mice infected with LAT(-) virus. The levels of LAT RNA in HVEM^-/-, LIGHT^-/-, CD160^-/-, and BTLA^-/- mice infected with LAT(+) virus were similar and were lower than the levels of LAT RNA in WT mice. However, LIGHT^-/-, CD160^-/-, and BTLA^-/- mice, independent of the presence of LAT, had levels of reactivation similar to those of WT mice infected with LAT(+) virus. Faster reactivation correlated with the upregulation of HVEM transcript. The LIGHT^-/-, CD160^-/-, and BTLA^-/- mice had higher levels of HVEM expression, and this, along with the absence of BTLA, LIGHT, or CD160, may contribute to faster reactivation, while the absence of each molecule, independent of LAT, may have contributed to lower latency. This study suggests that, in the absence of competition with gD for binding to HVEM, LAT RNA is important for WT levels of latency but not for WT levels of reactivation.IMPORTANCE The effects of BTLA, LIGHT, and CD160 on latency reactivation are not known. We show here that in BTLA, LIGHT, or CD160 null mice, latency is reduced; however, HVEM expression is upregulated compared to that of WT mice, and this upregulation is associated with higher reactivation that is independent of LAT but dependent on gD expression. Thus, one of the mechanisms by which BTLA, LIGHT, and CD160 null mice enhance reactivation appears to be the increased expression of HVEM in the presence of gD. Thus, our results suggest that blockade of HVEM-LIGHT-BTLA-CD160 contributes to reduced HSV-1 latency and reactivation.

Tannic Acid-Modified Silver and Gold Nanoparticles as Novel Stimulators of Dendritic Cells Activation

Silver nanoparticles (AgNPs) are promising new antimicrobial agents against a wide range of skin and mucosal pathogens. However, their interaction with the immune system is currently not fully understood. Dendritic cells (DCs) are crucial during development of T cell-specific responses against bacterial and viral pathogens. We have previously shown that tannic acid-modified silver nanoparticles (TA-AgNPs) consist of a promising microbicide against HSV-2. The aim of this study was to compare the ability of TA-AgNPs or TA-AuNPs of similar sizes (TA-Ag/AuNPs) to induce DCs maturation and activation in the presence of HSV-2 antigens when used at non-toxic doses. First, we used JAWS II DC line to test toxicity, ultrastructure as well as activation markers (MHC I and II, CD40, CD80, CD86, PD-L1) and cytokine production in the presence of TA-Ag/AuNPs. Preparations of HSV-2 treated with nanoparticles (TA-Ag/AuNPs-HSV-2) were further used to investigate HSV-2 antigen uptake, activation markers, TLR9 expression, and cytokine production. Additionally, we accessed proliferation and activation of HSV-2-specific T cells by DCs treated with TA-AgNP/AuNPs-HSV-2. We found that both TA-AgNPs and TA-AuNPs were efficiently internalized by DCs and induced activated ultrastructure. Although TA-AgNPs were more toxic than TA-AuNPs in corresponding sizes, they were also more potent stimulators of DCs maturation and TLR9 expression. TA-Ag/AuNPs-HSV-2 helped to overcome inhibition of DCs maturation by live or inactivated virus through up-regulation of MHC II and CD86 and down-regulation of CD80 expression. Down-regulation of CD40 expression in HSV-2-infected DCs was reversed when HSV-2 was treated with TA-NPs sized >30 nm. On the other hand, small-sized TA-AgNPs helped to better internalize HSV-2 antigens. HSV-2 treated with both types of NPs stimulated activation of JAWS II and memory CD8+ T cells, while TA-AgNPs treatment induced IFN-γ producing CD4+ and CD8+ T cells. Our study shows that TA-AgNPs or TA-AuNPs are good activators of DCs, albeit their final effect upon maturation and activation may be metal and size dependent. We conclude that TA-Ag/AuNPs consist of a novel class of nano-adjuvants, which can help to overcome virus-induced suppression of DCs activation.

Misdirection of endosomal trafficking mediated by herpes simplex virus-encoded glycoprotein B

Herpes simplex virus (HSV)-encoded glycoprotein B (gB) is the most abundant protein in the viral envelope and promotes fusion of the virus with the cellular membrane. In the present study, we found that gB impacts on the major histocompatibility complex (MHC)-II pathway of antigen presentation by fostering homotypic fusion of early endosomes and trapping MHC-II molecules in these altered endosomes. By using an overexpression approach, we demonstrated that transient expression of gB induces giant vesicles of early endosomal origin, which contained Rab5, early endosomal antigen 1 (EEA1), and large amounts of MHC-II molecules [human leukocyte antigen (HLA)-DR, and HLA-DM], but no CD63. In HSV-1-infected and stably transfected cell lines that expressed lower amounts of gB, giant endosomes were not observed, but strongly increased amounts of HLA-DR and HLA-DM were found in EEA1⁺ early endosomes. We used these giant vesicles as a model system and revealed that gB interacts with Rab5 and EEA1, and that gB-induced homotypic fusion of early endosomes to giant endosomes requires phosphatidylinositol 3-phosphate, the activity of soluble N-ethylmaleimide-sensitive factor attachment protein receptors, and the cytosolic gB sequence ⁸⁸⁹YTQVPN⁸⁹⁴ We conclude that gB expression alters trafficking of molecules of the HLA-II processing pathway, which leads to increased retention of MHC-II molecules in early endosomal compartments, thereby intercepting antigen presentation.-Niazy, N., Temme, S., Bocuk, D., Giesen, C., König, A., Temme, N., Ziegfeld, A., Gregers, T. F., Bakke, O., Lang, T., Eis-Hübinger, A. M., Koch, N. Misdirection of endosomal trafficking mediated by herpes simplex virus-encoded glycoprotein B.

Viruses and the origin of microbiome selection and immunity

The last common metazoan ancestor (LCMA) emerged over half a billion years ago. These complex metazoans provided newly available niche space for viruses and microbes. Modern day contemporaries, such as cnidarians, suggest that the LCMA consisted of two cell layers: a basal endoderm and a mucus-secreting ectoderm, which formed a surface mucus layer (SML). Here we propose a model for the origin of metazoan immunity based on external and internal microbial selection mechanisms. In this model, the SML concentrated bacteria and their associated viruses (phage) through physical dynamics (that is, the slower flow fields near a diffusive boundary layer), which selected for mucin-binding capabilities. The concentration of phage within the SML provided the LCMA with an external microbial selective described by the bacteriophage adherence to mucus (BAM) model. In the BAM model, phage adhere to mucus protecting the metazoan host against invading, potentially pathogenic bacteria. The same fluid dynamics that concentrated phage and bacteria in the SML also concentrated eukaryotic viruses. As eukaryotic viruses competed for host intracellular niche space, those viruses that provided the LCMA with immune protection were maintained. If a resident virus became pathogenic or if a non-beneficial infection occurred, we propose that tumor necrosis factor (TNF)-mediated programmed cell death, as well as other apoptosis mechanisms, were utilized to remove virally infected cells. The ubiquity of the mucosal environment across metazoan phyla suggest that both BAM and TNF-induced apoptosis emerged during the Precambrian era and continue to drive the evolution of metazoan immunity.

Interrelationship of Primary Virus Replication, Level of Latency, and Time to Reactivation in the Trigeminal Ganglia of Latently Infected Mice

We sought to determine the possibility of an interrelationship between primary virus replication in the eye, the level of viral DNA in the trigeminal ganglia (TG) during latency, and the amount of virus reactivation following ocular herpes simplex virus type 1 (HSV-1) infection. Mice were infected with virulent (McKrae) or avirulent (KOS and RE) strains of HSV-1, and virus titers in the eyes and TG during primary infection, level of viral gB DNA in TG on day 28 postinfection (p.i.), and virus reactivation on day 28 p.i. as measured by explant reactivation were calculated. Our results suggest that the avirulent strains of HSV-1, even after corneal scarification, had lower virus titers in the eye, had less latency in the TG, and took a longer time to reactivate than virulent strains of HSV-1. The time to explant reactivation of avirulent strains of HSV-1 was similar to that of the virulent LAT((-)) McKrae-derived mutant. The viral dose with the McKrae strain of HSV-1 affected the level of viral DNA and time to explant reactivation. Overall, our results suggest that there is no absolute correlation between primary virus titer in the eye and TG and the level of viral DNA in latent TG and time to reactivation.

IMPORTANCE

Very little is known regarding the interrelationship between primary virus replication in the eye, the level of latency in TG, and the time to reactivate in the mouse model. This study was designed to answer these questions. Our results point to the absence of any correlation between the level of primary virus replication and the level of viral DNA during latency, and neither was an indicator of how rapidly the virus reactivated following explant TG-induced reactivation.

Herpes Zoster Meningitis Complicating Combined Tocilizumab and Cyclosporine Therapy for Adult-Onset Still's Disease

A 56-year-old female with refractory adult-onset Still's disease presented with ocular herpes zoster infection during TCZ treatment. After three days of acyclovir treatment (5 mg/kg), she developed a severe headache and high fever. Viral DNA isolation and cerebral spinal fluid abnormalities led to a herpes zoster meningitis diagnosis. Her meningitis was cured by high doses of intravenous acyclovir (10 mg/kg for 14 days). To our knowledge, this is the first report of meningeal herpes zoster infection in rheumatic diseases under TCZ treatment.

The association between antibodies to neurotropic pathogens and schizophrenia: a case-control study

Background:

Exposure to neurotropic pathogens has been proposed as an environmental risk factor for schizophrenia and can be evaluated by measuring pathogen-specific immunoglobulin G (IgG). Seroprevalence of pathogen-specific IgG reflects prior exposure, whereas IgG levels are associated with reactivity or reinfection. Several studies have examined these parameters in schizophrenia. However, results still remain inconclusive, as several previous studies did not correct for important confounding factors.

Aims:

To investigate whether schizophrenia is associated with prior exposure to neurotropic pathogens, or with their reactivation.

Methods:

We examined the seroprevalence and titer of IgG antibodies against herpes simplex virus-1 and -2 (HSV-1/HSV-2), varicella zoster virus (VZV), Epstein–Barr virus (EBV), cytomegalovirus (CMV), and Toxoplasma gondii (TG) in plasma of 368 adult patients with a schizophrenia spectrum disorder and 282 controls using ELISA.

Results:

We did not find evidence for an increased exposure to HSV-1, HSV-2, EBV, and TG in patients. There was a significantly higher seroprevalence of VZV (98.9% vs. 95.6%, P<0.05) and CMV (40.4% vs. 27.7%, P<0.001) in controls as compared with patients, which did not remain statistically significant after adjustment for various potential confounders. We did not find significant differences in antibody titers of seropositive patients and controls for any of the six pathogens.

Conclusions:

Our results do not support the hypothesis that increased exposure to neurotropic pathogens after birth is associated with schizophrenia.

CD8α dendritic cells drive establishment of HSV-1 latency

It is generally accepted that CD8 T cells play the key role to maintain HSV-1 latency in trigeminal ganglia of ocularly infected mice. Yet, comparably little is known about the role of innate immunity in establishment of viral latency. In the current study, we investigated whether CD8α DCs impact HSV-1 latency by examining latency in the trigeminal ganglia (TG) of wild-type (WT) C57BL/6 versus CD8α-/- (lack functional CD8 T cells and CD8α+ DCs), CD8β-/- (have functional CD8α+ T cells and CD8α+ DCs), and β2m-/- (lack functional CD8 T cells but have CD8α+ DCs) mice as well as BXH2 (have functional CD8 T cells but lack CD8α+ DCs) versus WT C3H (have functional CD8α T cells and CD8α+ DCs) mice. We also determined whether the phenotype of CD8α-/- and BXH2 mice could be restored to that of WT mice by adoptive transfer of WT CD8+ T cells or bone marrow (BM) derived CD8α+ DCs. Our results clearly demonstrate that CD8α DCs, rather than CD8 T cells, are responsible for enhanced viral latency and recurrences.

Coregulatory interactions among CD8α dendritic cells, the latency-associated transcript, and programmed death 1 contribute to higher levels of herpes simplex virus 1 latency

The latency-associated transcript (LAT) of herpes simplex virus 1 (HSV-1), CD8α(+) dendritic cells (DCs), and programmed death 1 (PD-1) have all been implicated in the HSV-1 latency-reactivation cycle. It is not known, however, whether an interaction between LAT and CD8α(+) DCs regulates latency and T-cell exhaustion. To address this question, we used LAT-expressing [LAT(+)] and LAT-negative [LAT(-)] viruses. Depletion of DCs in mice ocularly infected with LAT(+) virus resulted in a reduction in the number of T cells expressing PD-1 in the trigeminal ganglia (TG), whereas depletion of DCs in mice similarly infected with LAT(-) virus did not alter PD-1 expression. CD8α(+) DCs, but not CD4(+) DCs, infected with LAT(+) virus had higher levels of ICP0, ICP4, thymidine kinase (TK), and PD-1 ligand 1 (PD-L1) transcripts than those infected with LAT(-) virus. Coculture of infected bone marrow (BM)-derived DCs from wild-type (WT) mice, but not infected DCs from CD8α(-/-) mice, with WT naive T cells contributed to an increase in PD-1 expression. Transfer of bone marrow from WT mice but not CD8α(-/-) mice to recipient Rag1(-/-) mice increased the number of latent viral genomes in reconstituted mice infected with the LAT(+) virus. Collectively, these data indicated that a reduction in latency correlated with a decline in the levels of CD8α(+) DCs and PD-1 expression. In summary, our results demonstrate an interaction among LAT, PD-1, and CD11c CD8α(+) cells that regulates latency in the TG of HSV-1-infected mice.

IMPORTANCE

Very little is known regarding the interrelationship of LAT, PD-1, and CD8α(+) DCs and how such interactions might contribute to relative numbers of latent viral genomes. We show here that (i) in both in vivo and in vitro studies, deficiency of CD8α(+) DCs significantly reduced T-cell exhaustion in the presence of LAT(+) virus but not LAT(-) virus; (ii) HSV-1 infectivity was significantly lower in LAT(-)-infected DCs than in their LAT(+)-infected counterparts; and (iii) adoptive transfer of bone marrow (BM) from WT but not CD8α(-/-) mice to recipient Rag1(-/-) mice restored latency to the level in WT mice following infection with LAT(+) virus. These studies point to a key role for CD8α(+) DCs in T-cell exhaustion in the presence of LAT, which leads to larger numbers of latent viral genomes. Thus, altering this negative function of CD8α(+) DCs can potentially be used to generate a more effective vaccine against HSV infection.

An In Vitro HSV-1 Reactivation Model Containing Quiescently Infected PC12 Cells

Advances in the understanding of the infection and reactivation process of herpes simplex type 1 (HSV-1) are generally gained by monolayer cultures or extensive and cost-intensive animal models. So far, no reliable in vitro skin model exists either to investigate the molecular mechanisms involved in controlling latency and virus reactivation or to test pharmaceuticals. Here we demonstrate the first in vitro HSV-1 reactivation model generated by using the human keratinocyte cell line HaCaT grown on a collagen substrate containing primary human fibroblasts. We integrated the unique feature of a quiescently infected neuronal cell line, the rat pheochromocytoma line PC12, within the dermal layer of the three-dimensional skin equivalent. Transmission electron microscopy, a cell-based TCID₅₀ assay, and polymerase chain reaction analysis were used to verify cell latency. Thereby viral DNA could be detected, whereas extracellular as well as intracellular virus activity could not be found. Further, the infected PC12 cells show no spontaneous reactivation within the in vitro skin equivalent. In order to simulate a physiologically comparable HSV-1 infection, we achieved a specific and pointed reactivation of quiescently HSV-1 infected PC12 cells by UVB irradiation at 1000 mJ/cm².

Adaptive and innate transforming growth factor beta signaling impact herpes simplex virus 1 latency and reactivation

Innate and adaptive immunity play important protective roles by combating herpes simplex virus 1 (HSV-1) infection. Transforming growth factor β (TGF-β) is a key negative cytokine regulator of both innate and adaptive immune responses. Yet, it is unknown whether TGF-β signaling in either immune compartment impacts HSV-1 replication and latency. We undertook genetic approaches to address these issues by infecting two different dominant negative TGF-β receptor type II transgenic mouse lines. These mice have specific TGF-β signaling blockades in either T cells or innate cells. Mice were ocularly infected with HSV-1 to evaluate the effects of restricted innate or adaptive TGF-β signaling during acute and latent infections. Limiting innate cell but not T cell TGF-β signaling reduced virus replication in the eyes of infected mice. On the other hand, blocking TGF-β signaling in either innate cells or T cells resulted in decreased latency in the trigeminal ganglia of infected mice. Furthermore, inhibiting TGF-β signaling in T cells reduced cell lysis and leukocyte infiltration in corneas and trigeminal ganglia during primary HSV-1 infection of mice. These findings strongly suggest that TGF-β signaling, which generally functions to dampen immune responses, results in increased HSV-1 latency.

The role of LAT in increased CD8+ T cell exhaustion in trigeminal ganglia of mice latently infected with herpes simplex virus 1

Herpes simplex virus (HSV) infection is a classic example of latent viral infection in humans and experimental animal models. The HSV-1 latency-associated transcript (LAT) plays a major role in the HSV-1 latency reactivation cycle and thus in recurrent disease. Whether the presence of LAT leads to generation of dysfunctional T cell responses in the trigeminal ganglia (TG) of latently infected mice is not known. To address this issue, we used LAT-positive [LAT(+)] and LAT-deficient [LAT(-)] viruses to evaluate the effect of LAT on CD8 T cell exhaustion in TG of latently infected mice. The amount of latency as determined by quantitative reverse transcription-PCR (qRT-PCR) of viral DNA in total TG extracts was 3-fold higher with LAT(+) than with LAT(-) virus. LAT expression and increased latency correlated with increased mRNA levels of CD8, PD-1, and Tim-3. PD-1 is both a marker for exhaustion and a primary factor leading to exhaustion, and Tim-3 can also contribute to exhaustion. These results suggested that LAT(+) TG contain both more CD8(+) T cells and more CD8(+) T cells expressing the exhaustion markers PD-1 and Tim-3. This was confirmed by flow cytometry analyses of expression of CD3/CD8/PD-1/Tim-3, HSV-1, CD8(+) T cell pentamer (specific for a peptide derived from residues 498 to 505 of glycoprotein B [gB(498-505)]), interleukin-2 (IL-2), and tumor necrosis factor alpha (TNF-α). The functional significance of PD-1 and its ligands in HSV-1 latency was demonstrated by the significantly reduced amount of HSV-1 latency in PD-1- and PD-L1-deficient mice. Together, these results may suggest that both PD-1 and Tim-3 are mediators of CD8(+) T cell exhaustion and latency in HSV-1 infection.

Prospects for Developing an Effective Vaccine Against Ocular Herpes Simplex Virus Infection

One of the hallmarks of herpes simplex virus (HSV) infection is the establishment of a lifelong latent infection accompanied by periods of recurrent disease. Primary HSV infections or repeated clinical recurrences do not elicit immune responses capable of completely preventing recurrences of endogenous virus. It is therefore questionable if vaccination approaches that seek to mimic the immune response to natural infection will reduce infection or disease due to an exogenous viral challenge. Approaches to the induction of protective responses by altering or enhancing both innate and adaptive immunity, using novel vaccines specifically tested in models of HSV infections of the eye, such as recombinant viral vaccine vectors and DNA vaccines, are detailed in this review.

Role of dendritic cells in enhancement of herpes simplex virus type 1 latency and reactivation in vaccinated mice

Ocular infection with herpes simplex virus type 1 (HSV-1) frequently leads to recurrent infection, which is a major cause of corneal scarring. Thus, the prevention of the establishment of latency should be a primary goal of vaccination against HSV-1. To this end, we have examined the contribution of dendritic cells (DCs) to the efficacy of a vaccine against ocular HSV-1 infection. Transgenic mice (expressing a CD11c-diphtheria toxin receptor-green fluorescent protein construct) with a BALB/c background were immunized with a vaccine consisting of DNA that encodes five HSV-1 glycoproteins or were immunized with vector control DNA. The vaccinated mice were then depleted of their DCs through the injection of diphtheria toxin before and after ocular challenge with HSV-1. Analyses of HSV-1 replication in the eye, blepharitis, corneal scarring, and the survival of the infected mice upon primary infection indicated that DC depletion neither promoted nor compromised the efficacy of the vaccine. In contrast, DC depletion was associated with an approximately fivefold reduction in the level of latent virus in the trigeminal ganglia (TGs) of latently infected mice, as well as a significant reduction in the reactivation rate of latent virus. The possibility that DCs enhance the latency of HSV-1 in the TGs of ocularly infected mice suggests for the first time that DCs, rather than acting as "immune saviors," can exacerbate disease and compromise vaccine efficacy by enhancing viral latency and reactivation.

Management of neuropathic orofacial pain

Current management of painful trigeminal neuropathies relies on pharmacological (topical and systemic), surgical, and complementary modalities. There is, however, a lack of quality research relating to the effectiveness of these modalities. In this review we analyze the available data that relates to the therapy of trigeminal neuralgia, postherpetic neuralgia, and posttraumatic neuropathies and provide clinical guidelines. The review focuses on medical management, as well as surgical and other interventions for painful neuropathies.

Human herpesvirus latency

Herpesviruses are among the most successful human pathogens. In healthy individuals, primary infection is most often inapparent. After primary infection, the virus becomes latent in ganglia or blood mononuclear cells. Three major subfamilies of herpesviruses have been identified based on similar growth characteristics, genomic structure, and tissue predilection. Each herpesvirus has evolved its own unique ecological niche within the host that allows the maintenance of latency over the life of the individual (e.g. the adaptation to specific cell types in establishing latent infection and the mechanisms, including expression of different sets of genes, by which the virus remains latent). Neurotropic alphaherpesviruses become latent in dorsal root ganglia and reactivate to produce epidermal ulceration, either localized (herpes simplex types 1 and 2) or spread over several dermatomes (varicalla-zoster virus). Human cytomegalovirus, the prototype betaherpesvirus, establishes latency in bone marrow-derived myeloid progenitor cells. Reactivation of latent virus is especially serious in transplant recipients and AIDS patients. Lymphotropic gammaherpesviruses (Epstein-Barr virus) reside latent in resting B cells and reactivate to produce various neurologic complications. This review highlights the alphaherpesvirus, specifically herpes simplex virus type 1 and varicella-zoster virus, and describes the characteristics of latent infection.

Satellite glial cells in sensory ganglia: from form to function

Current information indicates that glial cells participate in all the normal and pathological processes of the central nervous system. Although much less is known about satellite glial cells (SGCs) in sensory ganglia, it appears that these cells share many characteristics with their central counterparts. This review presents information that has been accumulated recently on the physiology and pharmacology of SGCs. It appears that SGCs carry receptors for numerous neuroactive agents (e.g., ATP, bradykinin) and can therefore receive signals from other cells and respond to changes in their environment. Activation of SGCs might in turn influence neighboring neurons. Thus SGCs are likely to participate in signal processing and transmission in sensory ganglia. Damage to the axons of sensory ganglia is known to contribute to neuropathic pain. Such damage also affects SGCs, and it can be proposed that these cells have a role in pathological changes in the ganglia.

Diagnosis of periodontal manifestations of systemic diseases

Many systemic diseases can mimic periodontitis or gingivitis. These include many immunologic, infectious, neoplastic and metabolic disorders. In comparison with periodontitis and gingivitis, these disorders are considerable less common. However, since their diagnosis and management differ, a high index of suspicion is frequently needed when confronted a patient presenting with gingival or periodontal disease. This chapter has reviewed a number of systemic conditions that may mimic clinically both gingivitis and chronic periodontitis and has focused on the features that may assist the clinician in making the diagnosis and providing specific therapies.

Herpes simplex virion entry into and intracellular transport within mammalian cells

Alphaherpesviruses, membrane-enveloped DNA viruses that are responsible for a host of human ailments, bind to, enter and are directly targeted to specific intracellular domains within their mammalian host cells. This review emphasizes recent work on the best studied of the alphaherpesviruses, Herpes simplex virus type 1 (HSV1). One area of focus is on recent work that has identified viral glycoproteins that are important in binding and internalization of the virus to the host cell. Complementary work on the receptors for those viral glycoproteins that reside on the host cell surface is also presented, with some discussion of how receptor variety might lead to the tissue tropism demonstrated by alphaherpes viruses. An additional area of focus in this review is how HSV uses the host cell transport systems to achieve intracellular targeting of the incoming virion toward the cell nucleus, and, after production of newly synthesized and assembled viral progeny, targeting them toward the plasma membrane for release.

Herpes simplex virus type 1 encephalitis is associated with elevated levels of F2-isoprostanes and F4-neuroprostanes

To better understand the pathogenesis of herpes simplex virus type 1 (HSV-1) infections of the nervous system, concentrations of F(4)-neuroprostanes (F(4)-NP) and F(2)-isoprostanes (F(2)-IP) in the murine brain were determined following intracerebral inoculation of HSV-1 or normal saline. F(4)-NP are highly selective, quantitative markers of neuronal oxidative damage, while F(2)-IP are markers of oxidative damage to brain tissue not limited to a certain cell type. In contrast to saline-treated control animals, HSV-1-infected animals developed encephalitic symptoms associated with severe inflammation, widespread HSV-1 protein expression, and significantly elevated F(4)-NP and F(2)-IP levels in the brain. Survivors of acute HSV-1 infection showed no encephalitic symptoms 2 to 3 weeks following virus inoculation. Brain tissue derived from mice euthanized 2 month after virus inoculation demonstrated expression of HSV-1 latency-associated transcripts without detectable HSV-1 protein expression. However, brain tissue from these animals showed focal chronic inflammation, moderately elevated F(2)-IP levels, and normal levels of F(4)-NP. These observations provide novel biochemical evidence that oxidant tissue injury is a mechanism underlying neuronal damage during acute HSV-1 encephalitis and suggest that oxidative damage to tissue may continue in the mammalian brain until at least several weeks after recovery from the symptomatic phase of HSV-1 infection.

Spinal cord involvement in uncomplicated herpes zoster

We prospectively evaluated herpes zoster patients during the acute phase of the disease for central nervous system involvement. Of 24 patients with spinal zoster, 13 (54%) had spinal cord abnormality, which was asymptomatic in 12 of the 13. Age but not lack of acyclovir treatment was associated with such involvement. In all but 2, neurological involvement resolved within 6 months. Although the mechanism responsible for the neurological abnormalities is unknown, findings may support the hypothesis that zoster is associated with spread of viral infection into the spinal cord and therefore support the possibility that zoster is due to active viral replication in the ganglion.

Protective T-cell-based immunity induced in neonatal mice by a single replicative cycle of herpes simplex virus

Newborns are very susceptible to infections because their immune systems are not fully developed and react to antigen exposure preferentially with unresponsiveness. UV-inactivated herpes simplex virus type 1 (HSV-1) represents such an antigen and does not induce an immune response in neonates. In contrast, protective T cells were primed in newborn mice by a single replicative cycle of DISC HSV-1 given once within 24 h of birth. Each of the HSV-1-primed CD4(+) or CD8(+) T cells induced in wild-type or interferon-deficient mice conferred resistance to naive animals exposed to a lethal virus challenge. Inactivated HSV-1, injected at variable doses up to 10(4) times that of DISC HSV-1, was ineffective in inducing any detectable immune responses in neonates. Thus, the capacity of HSV-1 to replicate once, but not the number of virus particles per se, was decisive in inducing protective T-cell-associated immunity in newborn mice.

Infection and the etiology and pathogenesis of multiple sclerosis

Multiple sclerosis (MS) currently defies clinical and scientific definitions, and carries a prognosis that remains practically unchanged despite many years of intensive research. Although the prevailing dogma is that MS is an immune-mediated condition, it fulfills none of the criteria of an autoimmune disease. On the other hand, there is enough significant data to suggest that infectious agents(s) could be involved in either direct damage to the white matter or induce inflammatory responses that secondarily affect the brain. Our goal here is to review the data supporting the possibility that infection has a critical role in the disease, examine the list of potential candidates that have been suggested, and outline an approach regarding the potential role of infectious agents in the etiology and pathogenesis of MS.

Analysis of individual human trigeminal ganglia for latent herpes simplex virus type 1 and varicella-zoster virus nucleic acids using real-time PCR

Herpes simplex virus type 1 (HSV-1) and varicella-zoster virus (VZV) establish latent infections in the peripheral nervous system following primary infection. During latency both virus genomes exhibit limited transcription, with the HSV-1 LATs and at least four VZV transcripts consistently detected in latently infected human ganglia. In this study we used real-time PCR quantitation to determine the viral DNA copy number in individual trigeminal ganglia (TG) from 17 subjects. The number of HSV-1 genomes was not significantly different between the left and right TG from the same individual and varied per subject from 42.9 to 677.9 copies per 100 ng of DNA. The number of VZV genomes was also not significantly different between left and right TG from the same individual and varied per subject from 37.0 to 3,560.5 copies per 100 ng of DNA. HSV-1 LAT transcripts were consistently detected in ganglia containing latent HSV-1 and varied in relative expression by >500-fold. Of the three VZV transcripts analyzed, only transcripts mapping to gene 63 were consistently detected in latently infected ganglia and varied in relative expression by >2,000-fold. Thus, it appears that, similar to LAT transcription in HSV-1 latently infected ganglia, VZV gene 63 transcription is a hallmark of VZV latency.

Reactivation of human herpesviruses after allogeneic peripheral blood stem cell transplantation and bone marrow transplantation

Reactivation of latent herpesviruses results in outcomes ranging from asymptomatic shedding of viruses to severe diseases, depending on the immunological competence of the host. Severe and prolonged suppression of cellular and humoral immunity after hematopoietic stem cell transplantation is accompanied by a high incidence of symptomatic recurrent herpesvirus infections. Subclinical reactivation also occurs more frequently than previously expected in transplant recipients. An increasing viral load in the blood detected by an antigenemia assay or PCR and viral shedding in regional fluids have a predictive value for subsequent diseases. Monitoring of viral DNA in the peripheral blood after allogeneic bone marrow transplantation (allo-BMT) reveals unique temporal profiles of detection for each herpesvirus. Recent studies demonstrate that recovery of CD4+ T cells is enhanced within one month after allogeneic peripheral blood stem cell transplantation (allo-PBSCT) compared to allo-BMT. To clarify whether this immunological advantage could affect the reactivation of human herpesvirus (HHV), we monitored the emergence of viral DNA by a nested-double polymerase chain reaction in peripheral blood leukocytes. Detection rates of HHV-6 DNAs which peak at 3-4 weeks post-transplant, were significantly reduced after allo-PBSCT compared to allo-BMT, while those of other herpesviruses which tend to be reactivated later than this period (Epstein-Barr virus and cytomegalovirus) were similar between the two types of transplants. Detection of HHV-6 DNA within the first month after the transplant was associated with delayed platelet engraftment. These results underscore the important role of CD4+ T reconstitution in inhibiting virus reactivation post-transplant.

Persisting viruses and autoimmunity

Viral infections can be responsible for the onset and sustaining of autoimmune processes. We discuss how chronic inflammation associated with viral persistence is the prerequisite for initiation of a multi-step process leading to autoimmunity. Firstly, chronic inflammation may favor the priming of autoreactive T cells that have escaped thymic selection and are specific for self-mimicking viral peptides in the periphery. In addition, viral persistence and inflammation can act synergistically to induce and sustain autoimmunity either unveiling cryptic self-epitopes, or favoring determinant spreading, or activating dendritic cells, or promoting constant priming of new autoreactive T cells, or contributing to the efficient generation of effector cells, or, finally, restimulating memory T lymphocytes.

A novel link between stress and human cytomegalovirus (HCMV) infection: sympathetic hyperactivity stimulates HCMV activation

Recently, inflammatory mediators such as TNFalpha were identified as triggering active human cytomegalovirus (HCMV) infection. Here, we demonstrate that a highly stressful event in the absence of systemic inflammation, as observed in patients with acute myocardial infarction, leads to the development of an active HCMV infection in latently infected patients. Elucidating the molecular mechanism of virus activation, we could show that catecholamines directly stimulate the HCMV immediate-early (IE) enhancer/promoter in monocytic cells via beta-2 adrenergic receptors. Subsequent activation of the cAMP/PK-A-signaling pathway results in enhanced synthesis and binding of the transcription factor CREB-1/ATF-1 to the cAMP-responsive elements within the IE enhancer. Epinephrine also enhanced HCMV gene expression in infected THP-1 cells by about 50% in three of four experiments. These data suggest that HCMV, like HSV-1 and VZV, can be (re)activated under stress conditions.

Additive effect of neutralizing antibody and antiviral drug treatment in preventing virus escape and persistence

Poorly cytopathic or noncytopathic viruses can escape immune surveillance and establish a chronic infection. Here we exploited the strategy of combining antiviral drug treatment with the induction of a neutralizing antibody response to avoid the appearance of neutralization-resistant virus variants. Despite the fact that H25 immunoglobulin transgenic mice infected with lymphocytic choriomeningitis virus mounted an early neutralizing antibody response, the virus escaped from neutralization and persisted. After ribavirin treatment of H25 transgenic mice, the appearance of neutralization-resistant virus was prevented and virus was cleared. Thus, the combination of virus-neutralizing antibodies and chemotherapy efficiently controlled the infection, whereas each defense line alone did not. Similar additive effects may be unexpectedly efficient and beneficial in humans after infections with persistent viruses such as hepatitis C virus and hepatitis B virus and possibly human immunodeficiency virus.

Bell's palsy and herpes viruses: to (acyclo)vir or not to (acyclo)vir?

The majority of peripheral seventh cranial nerve palsy cases remain without an identified etiology and will eventually be diagnosed as idiopathic or Bell's palsy. Some features of this condition may be characteristic of a viral infection. Indeed, several herpes viruses have been implicated as potential causative pathogens. Besides varicella-zoster virus, shown to cause Bell's palsy under the Ramsay-Hunt syndrome, recent years have seen an increased interest and focus on the possible herpes simplex virus type 1 (HSV-1) etiology in idiopathic facial paralysis. We review the clinical, biological and virological basis for the potential herpetic cause of Bell's palsy and the rational for antiviral therapy in this condition.

Herpes simplex virus as a transneuronal tracer

Determining the connections of neural systems is critical for determining how they function. In this review, we focus on the use of HSV-1 and HSV-2 as transneuronal tracers. Using HSV to examine neural circuits is technically simple. HSV is injected into the area of interest, and after several days, the animals are perfused and processed for immunohistochemistry with antibodies to HSV proteins. Variables which influence HSV infection include species of host, age of host, titre of virus, strain of virus and phenotype of infected cell. The choice of strain of HSV is critically important. Several strains of HSV-1 and HSV-2 have been utilized for purposes of transneuronal tract-tracing. HSV has been used successfully to study neuronal circuitry in a variety of different neuroanatomical systems including the somatosensory, olfactory, visual, motor, autonomic and limbic systems.

Persisting viruses and chronic inflammation: understanding their relation to autoimmunity

Viral infections may induce and sustain autoimmune processes via several and overlapping mechanisms. We outline how chronic inflammation, sustained by persisting viruses, may be "the prerequisite" for initiation and maintenance of the multistep process leading to autoimmunity. Chronic inflammation may favour priming of autoreactive T cells which have escaped thymic tolerance and are able to mount a cross-reactive response to self-mimicking antigens carried by viruses in the periphery. Moreover, chronic inflammation and persisting viruses can synergistically support autoimmunity through other relevant mechanisms: unveiling of cryptic self-epitopes, determinant spreading, activation of dendritic cells, constant priming of new autoreactive T cells, and efficient generation and restimulation of memory cells. Therefore, viruses seem to play a key role among the many environmental factors which, together with the genetic background, have been implicated in the pathogenesis of autoimmune diseases. We will also discuss some hypotheses explaining why autoimmunity is a rare event.

Induction of protective cytotoxic T cell responses in the presence of high titers of virus-neutralizing antibodies: implications for passive and active immunization

The effect of preexistent virus-neutralizing antibodies on the active induction of antiviral T cell responses was studied in two model infections in mice. Against the noncytopathic lymphocytic choriomeningitis virus (LCMV), pretreatment with neutralizing antibodies conferred immediate protection against systemic virus spread and controlled the virus below detectable levels. However, presence of protective antibody serum titers did not impair induction of antiviral cytotoxic T lymphocyte (CTL) responses after infection with 10(2) PFU of LCMV. These CTLs efficiently protected mice independent of antibodies against challenge with LCMV-glycoprotein recombinant vaccinia virus; they also protected against otherwise lethal lymphocytic choriomeningitis caused by intracerebral challenge with LCMV-WE, whereas transfused antibodies alone did not protect, and in some cases even enhanced, lethal lymphocytic choriomeningitis. Against the cytopathic vesicular stomatitis virus (VSV), specific CTLs and Th cells were induced in the presence of high titers of VSV-neutralizing antibodies after infection with 10(6) PFU of VSV, but not at lower virus doses. Taken together, preexistent protective antibody titers controlled infection but did not impair induction of protective T cell immunity. This is particularly relevant for noncytopathic virus infections since both virus-neutralizing antibodies and CTLs are essential for continuous virus control. Therefore, to vaccinate against such viruses parallel or sequential passive and active immunization may be a suitable vaccination strategy to combine advantages of both virus-neutralizing antibodies and CTLs.