Herpes simplex neuropathy

HSV-1 infection-induced herpetic neuralgia involves a CCL5/CCR5-mediated inflammation mechanism

Herpetic-related neuralgia (HN) caused by varicella-zoster virus (VZV) infection is one of the most typical and common neuropathic pain in the clinic. However, the potential mechanisms and therapeutic approaches for the prevention and treatment of HN are still unclear. This study aims to provide a comprehensive understanding of the molecular mechanisms and potential therapeutic targets of HN. We used an HSV-1 infection-induced HN mouse model and screened the differentially expressed genes (DEGs) in the DRG and spinal cord using an RNAseq technique. Moreover, bioinformatics methods were used to figure out the signaling pathways and expression regulation patterns of the DEGs enriched. In addition, quantitative real-time RT-PCR and western blot were carried out to further confirm the expression of DEGs. HSV-1 inoculation in mice resulted in mechanical allodynia, thermal hyperalgesia, and cold allodynia, following the infection of HSV-1 in both DRG and spinal cord. Besides, HSV-1 inoculation induced an up-regulation of ATF3, CGRP, and GAL in DRG and activation of astrocytes and microglia in the spinal cord. Moreover, 639 genes were upregulated, 249 genes were downregulated in DRG, whereas 534 genes were upregulated and 12 genes were downregulated in the spinal cord of mice 7 days after HSV-1 inoculation. GO and KEGG enrichment analysis suggested that immune responses and cytokine-cytokine receptor interaction are involved in DRG and spinal cord neurons in mice after HSV-1 infection. In addition, CCL5 and its receptor CCR5 were significantly upregulated in DRG and spinal cord upon HSV-1 infection in mice. And blockade of CCR5 exhibited a significant analgesic effect and suppressed the upregulation of inflammatory cytokines in DRG and spinal cord induced by HSV-1 infection in mice. HSV-1 infection-induced allodynia and hyperalgesia in mice through dysregulation of immune response and cytokine-cytokine receptor interaction mechanism. Blockade of CCR5 alleviated allodynia and hyperalgesia probably through the suppression of inflammatory cytokines. Therefore, CCR5 could be a therapeutic target for the alleviation of HSV-1 infection-induced HN.

Rodent models of postherpetic neuralgia: How far have we reached?

Background

Induced by varicella zoster virus (VZV), postherpetic neuralgia (PHN) is one of the common complications of herpes zoster (HZ) with refractory pain. Animal models play pivotal roles in disclosing the pain mechanisms and developing effective treatments. However, only a few rodent models focus on the VZV-associated pain and PHN.

Objective

To summarize the establishment and characteristics of popular PHN rodent models, thus offer bases for the selection and improvement of PHN models.

Design

In this review, we retrospect two promising PHN rodent models, VZV-induced PHN model and HSV1-induced PHN model in terms of pain-related evaluations, their contributions to PHN pathogenesis and pharmacology.

Results

Significant difference of two PHN models is the probability of virus proliferation; 2) Most commonly used pain evaluation of PHN model is mechanical allodynia, but pain-induced anxiety and other behaviours are worth noting; 3) From current PHN models, pain mechanisms involve changes in virus gene and host gene expression, neuroimmune-glia interactions and ion channels; 4) antiviral drugs and classical analgesics serve more on the acute stage of herpetic pain.

Conclusions

Different PHN models assessed by various pain evaluations combine to fulfil more comprehensive understanding of PHN.

Comparison of Herpes Simplex Virus Reactivation Frequency in Acute Idiopathic Cranial Mononeuropathy and Normal Population by Serological Assay

Background: Herpes simplex virus (HSV) is a neurotropic DNA virus with a high prevalence. Following primary infection, HSV remains dormant in the neural ganglia. Secondary infection can emerge after the reactivation of latent infection, presenting as neurological manifestations. Previous studies have demonstrated the relationship between HSV reactivation and selective involvement of cranial nerves. Depending on the affected nerve, cranial mononeuropathies can present with symptoms, including diplopia, blurred vision, vertigo, unilateral facial palsy, speech impairment, swallowing difficulties, and hoarseness. Objectives: This study used a serological assay to compare HSV reactivation frequency between patients with recent idiopathic cranial mononeuropathies and normal individuals. Methods: Plasma samples from 35 idiopathic cranial mononeuropathy cases (57.2% women, mean age 58.37 years) and 35 age and sex-matched healthy controls were analyzed for anti-HSV immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies by enzyme-linked immunosorbent assay (ELISA). Results: Anti-HSV IgG antibody was positive in 91.4% of patients and 88.6% of controls. The mean serum anti-HSV IgG antibody level was significantly higher in patients (146.78 ± 60 RU/mL) than in the controls (130.61 ± 52.99 RU/mL) (P-value = 0.037). Anti-HSV IgM antibody was positive in 37.1% of patients and 14.3% of controls (P = 0.042). Conclusions: The frequency of HSV reactivation was significantly higher in patients with acute idiopathic cranial mononeuropathy than in the healthy controls, indicating the possible role of HSV as an etiology of cranial mononeuropathy.

S100A9 plays a pivotal role in a mouse model of herpetic neuralgia via TLR4/TNF pathway

Herpetic neuralgia is a painful condition following herpes zoster disease, which results from Varicella-zoster virus reactivation in the dorsal or trigeminal sensory ganglia. Nevertheless, the pathophysiological mechanisms involved in herpetic neuralgia are not well understood. Recently, we identified, that neuroimmune-glia interactions in the sensory ganglion is a critical mechanism for the development of herpetic neuralgia. Here, we investigate the contribution of S100A9, a well-known pro-inflammatory molecule produced by myeloid cells, for the development of herpetic neuralgia using a murine model of HSV-1 infection. We found that cutaneous HSV-1 infection results in an increase of S100A9 expression in the Dorsal Root Ganglia (DRGs). Infiltrating neutrophils into the DRGs were the main source of S100A9 post HSV-1 infection. Functionally, genetic or pharmacological inhibition of S100A9 impairs the development of HSV-1 infection-induced mechanical pain hypersensitivity. Finally, we found that the pronociceptive role of S100A9 in herpetic neuralgia depends on the TLR4/TNF pathway. These results unraveled previously unknown mechanisms involved in the pathophysiology of herpetic neuralgia and indicate that S100A9 might be an important target for novel therapies aiming acute herpetic neuralgia.

Modulation of Voltage-Gated Sodium Channel Activity in Human Dorsal Root Ganglion Neurons by Herpesvirus Quiescent Infection

The molecular mechanisms of pain associated with alphaherpesvirus latency are not clear. We hypothesize that the voltage-gated sodium channels (VGSC) on the dorsal root ganglion (DRG) neurons controlling electrical impulses may have abnormal activity during latent viral infection and reactivation. We used herpes simplex virus 1 (HSV-1) to infect the human DRG-derived neuronal cell line HD10.6 in order to study the establishment and maintenance of viral latency, viral reactivation, and changes in the functional expression of VGSCs. Differentiated cells exhibited robust tetrodotoxin (TTX)-sensitive sodium currents, and acute infection significantly reduced the functional expression of VGSCs within 24 h and completely abolished VGSC activity within 3 days. A quiescent state of infection mimicking latency can be achieved in the presence of acyclovir (ACV) for 7 days followed by 5 days of ACV washout, and then the viruses can remain dormant for another 3 weeks. It was noted that during the establishment of HSV-1 latency, the loss of VGSC activity caused by HSV-1 infection could not be blocked by ACV treatment. However, neurons with continued ACV treatment for another 4 days showed a gradual recovery of VGSC functional expression. Furthermore, the latently infected neurons exhibited higher VGSC activity than controls. The overall regulation of VGSCs by HSV-1 during quiescent infection was proved by increased transcription and possible translation of Nav1.7. Together, these observations demonstrated a very complex pattern of electrophysiological changes during HSV infection of DRG neurons, which may have implications for understanding of the mechanisms of virus-mediated pain linked to latency and reactivation.IMPORTANCE The reactivation of herpesviruses, most commonly varicella-zoster virus (VZV) and pseudorabies virus (PRV), may cause cranial nerve disorder and unbearable pain. Clinical studies have also reported that HSV-1 causes postherpetic neuralgia and chronic occipital neuralgia in humans. The current work meticulously studies the functional expression profile changes of VGSCs during the processes of HSV-1 latency establishment and reactivation using human dorsal root ganglion-derived neuronal HD10.6 cells as an in vitro model. Our results indicated that VGSC activity was eliminated upon infection but steadily recovered during latency establishment and that latent neurons exhibited even higher VGSC activity. This finding advances our knowledge of how ganglion neurons generate uncharacteristic electrical impulses due to abnormal VGSC functional expression influenced by the latent virus.

Regulation of T-type Ca2+ channel expression by herpes simplex virus-1 infection in sensory-like ND7 cells

Infection of sensory neurons by herpes simplex virus (HSV)-1 disrupts electrical excitability, altering pain sensory transmission. Because of their low threshold for activation, functional expression of T-type Ca²⁺ channels regulates various cell functions, including neuronal excitability and neuronal communication. In this study, we have tested the effect of HSV-1 infection on the functional expression of T-type Ca²⁺ channels in differentiated ND7-23 sensory-like neurons. Voltage-gated Ca²⁺ currents were measured using whole cell patch clamp recordings in differentiated ND7-23 neurons under various culture conditions. Differentiation of ND7-23 cells evokes a significant increase in T-type Ca²⁺ current densities. Increased T-type Ca²⁺ channel expression promotes the morphological differentiation of ND7-23 cells and triggers a rebound depolarization. HSV-1 infection of differentiated ND7-23 cells causes a significant loss of T-type Ca²⁺ channels from the membrane. HSV-1 evoked reduction in the functional expression of T-type Ca²⁺ channels is mediated by several factors, including decreased expression of Ca_v3.2 T-type Ca²⁺ channel subunits and disruption of endocytic transport. Decreased functional expression of T-type Ca²⁺ channels by HSV-1 infection requires protein synthesis and viral replication, but occurs independently of Egr-1 expression. These findings suggest that infection of neuron-like cells by HSV-1 causes a significant disruption in the expression of T-type Ca²⁺ channels, which can results in morphological and functional changes in electrical excitability.

Involvement of aberrant calcium signalling in herpetic neuralgia

Alpha-herpesviruses, herpes simplex viruses (HSV) and varicella zoster virus (VZV), are pathogens of the peripheral nervous system. After primary infection, these viruses establish latency within sensory ganglia, while retaining the ability to reactivate. Reactivation of VZV results in herpes zoster, a condition characterized by skin lesions that leads to post-herpetic neuralgia. Recurrent reactivations of HSV, which cause mucocutaneous lesions, may also result in neuralgia. During reactivation of alpha-herpesviruses, satellite glial cells (SGCs), which surround neurons in sensory ganglia, become infected with the replicating virus. SGCs are known to contribute to neuropathic pain in a variety of animal pain models. Here we investigated how infection of short-term cultures of mouse trigeminal ganglia with HSV-1 affects communication between SGCs and neurons, and how this altered communication may increase neuronal excitability, thus contributing to herpetic neuralgia. Mechanical stimulation of single neurons or SGCs resulted in intercellular calcium waves, which were larger in cultures infected with HSV-1. Two differences were observed between control and HSV-1 infected cultures that could account for this augmentation. Firstly, HSV-1 infection induced cell fusion among SGCs and neurons, which would facilitate the spread of calcium signals over farther distances. Secondly, using calcium imaging and intracellular electrical recordings, we found that neurons in the HSV-1 infected cultures exhibited augmented influx of calcium upon depolarization. These virally induced changes may not only cause more neurons in the sensory ganglia to fire action potentials, but may also increase neurotransmitter release at the presynaptic terminals in the spinal cord. They are therefore likely to be contributing factors to herpetic neuralgia.

Animal models and pharmacology of herpetic and postherpetic pain

Varicella-zoster virus (VZV) causes varicella upon primary infection and subsequently becomes latent in the sensory ganglia. Reactivation of latent VZV in the sensory ganglion results in herpes zoster, which usually begins with pain and dysesthesia. Pain that persists long after healing of the rash is termed postherpetic neuralgia. VZV inoculation into rats induces mechanical allodynia and thermal hyperalgesia without causing herpes zoster. As with VZV, herpes simplex virus 1 (HSV1) is an alphaherpesvirus. HSV1 also becomes latent in the sensory ganglia after primary infection, and reactivation of latent HSV1 in the sensory ganglion results in herpes simplex. HSV1 inoculation into mice causes zoster-like skin lesions together with mechanical allodynia and mechanical hyperalgesia. A marked difference between the two rodent models is whether the herpes virus proliferates in the nervous system after inoculation. VZV-inoculated rats are useful for investigating mechanical allodynia induced by latent infection with herpes virus. HSV1-inoculated mice are useful for investigating mechanical allodynia induced by the proliferation of herpes virus in sensory neurons and for assessing the effects of acute herpetic pain on the incidence of postherpetic allodynia.

Herpesvirus infections of the nervous system

There are eight human herpesviruses (HHVs). Primary infection by any of the eight viruses, usually occurring in childhood, is either asymptomatic or produces fever and rash of skin or mucous membranes; other organs might be involved on rare occasions. After primary infection, the virus becomes latent in ganglia or lymphoid tissue. With the exception of HHV-8, which causes Kaposi's sarcoma in patients with AIDS, reactivation of HHVs can produce one or more of the following complications: meningitis, encephalitis, myelitis, vasculopathy, ganglioneuritis, retinal necrosis and optic neuritis. Disease can be monophasic, recurrent or chronic. Infection with each herpesvirus produces distinctive clinical features and imaging abnormalities. This Review highlights the patterns of neurological symptoms and signs, along with the typical imaging abnormalities, produced by each of the HHVs. Optimal virological studies of blood, cerebrospinal fluid and affected tissue for confirmation of diagnosis are discussed; this is particularly important because some HHV infections of the nervous system can be treated successfully with antiviral agents.

Herpes simplex virus type-1 latency-associated transcript-induced immunoreactivity of substance P in trigeminal neurons is reversed by bone morphogenetic protein-7

Herpes simplex virus type-1 (HSV-1) primarily infects mucoepithelial tissues of the eye and the orofacial region. Subsequently, the virus is retrogradely transported through the axons of the trigeminal sensory neurons to their nuclei, where the virus establishes a life-long latent infection. During this latency period, the viral genome is transcriptionally silent except for a single region encoding the latency-associated transcript (LAT). To understand how HSV-1 latency might affect the expression of substance P in sensory neurons, we transfected primary cultures of trigeminal neurons obtained from rat embryos, with LAT expressing plasmids. The expression of LAT increased the percentage of substance P-immunoreactive neurons by two thirds. To examine the effect of bone morphogenetic protein-7 (BMP7) on the LAT-induced increase in substance P expression in trigeminal neurons, cultures transfected with LAT were treated with BMP7. Treatment with BMP7 reversed the effects of LAT on substance P expression in trigeminal neurons. Our data show for the first time that LAT increases substance P expression in trigeminal neurons and BMP7 can reverse these effects of LAT.

Transient urinary retention and chronic neuropathic pain associated with genital herpes simplex virus infection

BACKGROUND

Genital herpes (GH) causes genital ulcer disease, severe transient pain, and often paresthesias. Whether or not GH can cause urinary retention or chronic neuropathic pain is not well known.

METHODS

We present two immunocompetent patients with GH associated with neuropathic symptoms. We also review the literature on GH and associated neurologic problems.

RESULTS

Patient 1 had primary herpes simplex virus (HSV)-2 infection with transient urinary retention and chronic bilateral neuropathic pain in the sacral area. Patient 2 had recurrent HSV-1 associated with unitaleral chronic neuropathic pain in the sacral area. Although transient urinary retention associated with GH is not uncommon, chronic neuropathic pain has not been reported previously.

CONCLUSIONS

Our cases show that chronic neuropathic pain, that is "pain initiated or caused by a primary lesion or dysfunction in the nervous system," can follow genital HSV infection.

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

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

Allodynia and hyperalgesia induced by herpes simplex virus type-1 infection in mice

Human subjects infected with herpes or varicella-zoster viruses complain of pain, such as allodynia, in or near the region with vesicles. However, the mechanisms of the pain are unclear. We show for the first time that infection with herpes simplex virus type-1 (HSV-1) induces allodynia and hyperalgesia in mice. When HSV-1 was inoculated on the hind paw of the mouse, eruption appeared on the back on day 5 post-inoculation, and zosteriform skin lesions were developed on the inoculated side. Allodynia and hyperalgesia became apparent in the hind paw on the inoculated side on day 5 and persisted until at least day 8. HSV-1 DNA was detected in the dorsal root ganglia from days 2 to 8 post-inoculation, with a peak effect on day 5. The application of heat-inactivated HSV-1 induced no allodynia, hyperalgesia and skin lesion. When started from days 0 or 2, repeated treatment with acyclovir, anti-HSV-1 agent, inhibited the appearance of allodynia, hyperalgesia, eruption and the viral proliferation in the dorsal root ganglia. In contrast, when started from days 5 or 6, acyclovir treatment slightly inhibited the development of skin lesions and the viral proliferation, but not allodynia and hyperalgesia. These results suggest that the propagation of HSV-1 in the dorsal root ganglia produces allodynia and hyperalgesia as a result of functional abnormality of the sensory neurons in mice. This may be a useful model for studying the mechanisms of herpetic pain.

Caffeine inhibits paresthesia induced by herpes simplex virus through action on primary sensory neurons in rats

Herpetic infection causes paresthesia, including hypoalgesia, in humans and hypoalgesia in rats. This study was conducted to examine the effect of caffeine, which inhibits replication of herpes simplex virus type-1 (HSV) and affects several neuronal functions, on HSV-induced paresthesia in rats. HSV-induced hypoalgesia was suppressed by repeated treatment of unilateral hindpaw with 10% caffeine gel regardless of when the treatment was started. Repeated treatment with acyclovir, an anti-HSV agent, suppressed HSV-induced hypoalgesia only when started before inoculation; acyclovir did not produce therapeutic effects on the HSV-induced sensory abnormality. Many dorsal root ganglion neurons were positive for HSV antigen following HSV inoculation of the hindpaw. Repeated treatment with caffeine and acyclovir markedly decreased HSV antigen-positive neurons in the dorsal root ganglia when started before, but not 2 or 4 days after, infection. These results suggest that topical caffeine inhibited HSV-induced paresthesia through direct action on sensory neurons, and that not only antiviral activity but also direct alteration of neural functions are involved in the caffeine sensory actions.

Paresthesia induced by cutaneous infection with herpes simplex virus in rats

To assess the effects of herpetic infection on somatic sensations, herpes simplex virus type-1 was inoculated into the unilateral hind paw of the rat and its behavioral responses to noxious pressure and tactile stimulation were examined. Herpetic infection significantly increased the nociceptive threshold of the treated hind paw with a delay around 4 days. The increase in the nociceptive threshold continued at least until post-inoculation day 21 and was larger at night than in the morning. Any alterations in tactile responses were not observed during this period. Herpetic DNA was detected by polymerase chain reaction in the inoculated skin, but not in the dorsal root ganglia on the inoculated side, on the next day after inoculation. But on the following days it was detected in the dorsal root ganglia, but not in the skin. These results suggest that herpetic infection of the dorsal root ganglion produces paresthesia as a functional abnormality of the sensory neurons in rats.

Postherpes simplex type 1 neuralgia simulating postherpetic neuralgia

Patients with prodromal neuralgia associated with recurrent herpes simplex type 1 (HST1) infection and chronic facial pain following years of relapsing HST1 have been described. Chronic neuralgia following a single clinical HST1 infection and simulating postherpetic neuralgia has not been previously reported. Such a case is described: A 49-yr-old woman with a 2-mo history of oral-facial dyskinesia developed burning pain and hypersensitivity of the left side of the tongue, lower gum, and inner cheek, followed 1 day later by a vesicular rash in the same painful distribution. Viral cultures of the lesions identified HST1 but not herpes zoster. Cerebrospinal fluid analyses during the vesicular lesion stage and 1 mo later were normal with no viral growth. Oral and facial lesions resolved after 10 days; acyclovir was given for 3 wk. Brain and brainstem magnetic resonance imaging (MRI), electroencephalogram, and brainstem evoked potential studies were normal. Hyperesthesias, allodynia, and burning pain persisted despite nonsteroidal antiinflammatory agents, codeine and hydrocodone. Oral opioids were administered until sedation occurred, with no relief of pain. The burning pain and hyperesthesia resolved after the 16th day of amitriptyline use, 75 mg/day. A trial off amitriptyline 6 mo later resulted in recurrence of pain, and amitriptyline was restarted with good pain control. Post-HST1 neuralgia may simulate postherpetic neuralgia clinically, and painful symptoms may respond to amitriptyline.

Pathogenesis of recurrent herpes simplex labialis. IV. Maturation of lesions within 8 hours after onset and implications for antiviral treatment

In order to define precisely the development of recurrent herpes simplex labialis, we studied 122 untreated or placebo-treated patients who were first seen when their lesions were less than 24 hours old. Subjects were divided into three groups with lesion ages of 0 to 8, 9 to 16, or 17 to 24 hours. Lesion pain, area, and virus titer were determined for each group at the time of the first clinic visit and again on the following day, and the change in lesion severity between visits was examined. The proportion of patients with increasing or decreasing lesion values was markedly influenced by lesion age. Among 0- to 8-hour-old lesions, area, pain, and virus titer increased in 27%, 21%, and 39% of the subjects, respectively, compared to 10%, 6%, and 0% among those lesions were 17 to 24 hours old at the first visit. A decrease in lesion area, pain, and virus titer was seen in 14%, 24%, and 12% of 0- to 8-hour-old lesions, compared with 35%, 65%, and 54% of the lesions in the 17- to 24-hour age group (p = 0.03, 0.006, and 0.0002). The majority of patients in each age group had mature lesions that remained unchanged or decreased in severity between visits. The possible benefits of antiviral chemotherapy to established lesions are limited because only a small number of untreated patients have progressive disease.

Genital herpes simplex--concepts and treatment

Genital herpes simplex is an increasingly common venereal disease caused by either herpes simplex virus type 1 or 2. The disease can be manifested in a primary and/or recurrent form, the clinical features and complications of which are reviewed. Potential problems include psychosocial difficulties, neonatal herpes simplex infections, and the possibility of an oncogenic role in cervical cancer. Diagnostic modalities, prophylactic measures, and management technics are discussed.

Facial neuralgia associated with recurrent herpes simplex

At least seven cases of facial neuralgia associated with recurrent herpes simplex have been reported in the medical literature. This condition has not been reported in the dental literature. A case of facial neuralgia associated with recurrent herpes simplex in a 34-year-old woman at varying intervals over a 20-year period is reported. Tension applied to the commissure on the right side of the patient's mouth during routine dental procedures can cause the neuralgia to develop, and she reports having undergone extraction of the permanent right mandibular first molar at the age of 15, when a similar neuralgia was present.

Transient neuropathic bladder following herpes simplex genitalis

A case of transient bladder dysfunction and urinary retention concomitant with herpes genitalis is presented. The protean manifestations of the herpes simplex virus, the similar neurotropic behavior of simplex and zoster, and the neurologic sequelae of the cutaneous simplex eruption are discussed. The possibility of sacral radiculopathy after herpes genitalis must be considered when evaluating acute or episodic neurogenic bladders.

Persistence in herpes simplex virus infections

Diseases of man caused by the virus of herpes simplex fall into two broad categories. The primary disease occurs only once in any individual's life and is caused by transmission of virus from an already infected human. Thereafter, the individual may be subject to recurrent herpetic disease, the manifestations of which are different from the primary disease. Recurrent disease varies in severity from trivial, to incapacitating and frankly lethal (as in diseases resulting from the virus's neurotropic and oncogenic properties). The source of the virus in recurrent herpetic disease has never been conclusively resolved, but is almost certainly endogenous to the patient. Theories, case reports and experiments exist to show that endogenous virus may, in periods of clinical quiescence, be latent (or persistent) at the site of the recurrent lesions itself, or more remotely in nerve tissues related to the site of recurrence.

Antibodies against herpes simplex virus type 1 subunit antigens in patients with trigeminal neuralgia and controls

Serum IgG antibody levels against herpes simplex virus (HSV) type 1 subunit (capsid, envelope, and excreted) antigens detected with radioimmunoassay were compared in 25 patients with trigeminal neuralgia and their age- and sex-matched controls. No significant differences were found between the patients and controls, either in the distribution of the antibody titers or in the mean titers against any of the subunit antigens tested. In 6 patients HSV antibody titers were tested before and after trigeminal root section; no significant changes were observed.