Herpes simplex encephalitis: an autopsy case with isolation of type 1 herpes simplex virus

Summary An adult case of herpes simplex encephalitis was studied after autopsy. Postmortem examination revealed necrotizing encephalitis associated with Cowdry type A intranuclear inclusion bodies in glial cells. Herper simplex virus type 1 was isolated from the removed brain. Herpes simplex virus antigens were detected diffusely in wide areas of the brain by immunofluorescent test and viral particles characteristic to herpes simplex virus were demonstrated by electron microscopy. There was an apparent discrepancy between severity of histological changes and distribution of virus antigen.     

聚合酶链反应诊断单纯疱疹病毒性脑炎

用聚合酶链反应（ＰＣＲ）扩增患者脑脊液（ＣｈＦ）中病毒特异性ＤＮＡ可早期快速诊断单纯疱疹病毒性脑炎（ＨＳＥ）。１９例临床确诊的病毒性脑炎患者，经ＰＣＲ在ＣＳＦ中检出单纯疱疹病毒（ＨＳＶ）１３例，全部阳性标本均经分子杂交证实为ＨＳＶ－ＤＮＡ，而１４例其他神经疾病（ＯＮＤ）对照组均为阴性，显示了这一方法的特异性。其中７例病毒性脑炎ＣＳＦ标本分别用ＰＣＲ分子杂交和病毒分离等三种方法检测ＨＳＶ；显示ＰＣＲ最为敏感。表明ＰＣＲ技术的广泛应用将提高ＨＳＥ的早期诊断水平，指导临床正确治疗。     

Changes in vascular permeability of the central nervous system by experimental herpes simplex and vaccinia virus infections

Summary A study was made to examine the occurrence and distribution of changes in vascular permeability in viral infections of the CNS in mice. Vascular permeability was demonstrated by fluorescent microscopic tracing of intravasally introduced serum albumin labeled with Evans blue. Viruses—Herpes simplex and different strains of vaccinia—were used, which produce contrasting clinical pictures and morphological changes following intracerebral inoculation. Immunofluorescent technique was employed for the localization of viral antigen. The principal findings were as follows:Infection with neurovirulent strains of vaccinia was followed by widespread lesions of the vascular permeability with exudation of albumin in the leptomeninges and diffusion in the neuropil of the cerebral and cerebellar cortex. Unless very large doses of a non-neuroadapted vaccinia strain were injected i.c., no clinical sings of disease appeared and no changes of the vascular permeability were detected in spite of virus multiplication.Following infection with Herpes simplex, changes of the vascular permeability were seen mainly in the hippocampal regions, in areas bordering on the ventricles and in the olfactory bulbs.The significance of the increased vascular permeability for the clinical picture is discussed, as is the relationship between the oedema and the reactions of the neuroectodermal cells.This study was supported by a grant, B69-12X-82-05, from the Swedish Medical Research Council. The authors wish to express their gratitude to Drs.E. Lycke, L. Lindholm, andY. Olsson for valuable criticism and advice and to Mrs.Gun Lundblad for skilful technical assistance.     

Anti-herpes simplex type 1 activity in IgG subclasses produced systemically and intrathecally in patients with herpes encephalitis

Summary The role of the humoral immune response in herpes simplex encephalitis (HSE) is largely unknown. The finding that herpes simplex virus type 1 (HSV 1) induced IgG Fc receptor binds to all IgG subclasses except IgG 3 prompted an investigation of anti-HSV activity in IgG subclasses from serum and cerebrospinal fluid (CSF) in ten patients with proven or highly probable HSE by means of a monoclonal antibody IgG subclass-specific solid-phase radioimmunoassay (SPRIA). In contrast to serum, CSF contained no or low anti-HSV IgG titres during the first 2 weeks of disease in five of seven patients tested. The IgG titres rose thereafter for at least 4 weeks after the start of illness and remained high in both serum and CSF up to 393 days. The anti-HSV IgG subclass distribution in serum was IgG 1 (ten of ten), IgG 2 (two of ten), IgG 3 (six of ten), and IgG 4 (six of ten). Two patients had a simultaneous anti-HSV IgG 3 and IgG 4 response. With the exception of one patient lacking anti-HSV IgG 4 and two patients lacking anti-HSV IgG 2, the subclass distribution in CSF was the same as in serum. The anti-HSV subclass distribution in sera from ten seropositive patients without evidence of recent herpes infection did not differ from that of the HSE patients, except that five of ten patients had simultaneous anti-HSV IgG 3 and IgG 4 responses. Thus we could not correlate the anti-HSV subclass response in patients with HSE with the subclass preference of the HSV-induced Fc receptor.     

Concurrent herpes simplex type 1 necrotizing encephalitis,cytomegalovirus ventriculoencephalitis and cerebral lymphoma in an AIDS patient

Unlike cytomegalovirus (CMV) ventriculoencephalitis, herpes simplex virus type 1 necrotizing encephalitis has only rarely been observed in AIDS patients. A 40-year-old bisexual man was followed for an HIV1 infection from 1987 onwards. In June 1993 he was referred for sudden confusion, left hemiparesia and fever. The blood contained less than 10 CD4 lymphocytes/mm³. The patient remained comatose and febrile, and died 4 weeks later. In coronal sections of the brain there was necrosis of the internal parts of the left temporal lobe, necrosis of certain areas of the ventricular walls and a small tumor at the top of the right frontal lobe, which proved to be a polymorphic high-grade lymphoma. CMV ventriculoencephalitis lesions were prominent in the ventricular walls of the oecipital lobes and there was a strong nuclear signal for CMV using in situ hybridization. Herpes simplex virus type 1 was shown in the nuclei and cytoplasm of certain neurons and astrocytes in the borders of the necrotized temporal lobe areas by immunohistochemistry, in situ hybridization and electron microscopy, whereas in situ hybridization and immunohistochemistry for CMV were negative in such areas. Necrotizing type 1 encephalitis must not be overlooked in immunodeficient patients.     

Intractable seizure disorder associated with chronic herpes infection HSV1 detection in tissue by the polymerase chain reaction

We describe the pathological findings and report the detection of herpes simplex virus 1 (HSV1) in the brain in three patients who presented with intractable seizures. All three patients had a previous history of HSV1 encephalitis and went on to develop a medically refractory seizure disorder necessitating surgical intervention. HSV1 encephalitis was clinically diagnosed and treated at 6 months, 3 years, and 7 months and surgical resection was done at 8.5 years, 6 years, and 3 years, in cases 1, 2 and 3, respectively. Pathological examination revealed chronic encephalitis in all three cases, with microglial nodules, intraparenchymal, perivascular and meningeal lymphocytic infiltrates, and gliosis. While immunohistochemical and ultrastructural studies were negative for viral pathogens, polymerase chain reaction (PCR) analysis revealed HSV1 genome. These cases represent examples of chronic herpes encephalitis and seizure disorder with presence of viral genome in the brain long after the initial episode of treated herpes encephalitis. Received: 15 September 1997     

Two cases of necrotizing myelopathy associated with malignancy caused by herpes simplex virus type 2

Summary Two cases of necrotizing myelopathy were autopsied; one was complicated with lung carcinoma and the other with chronic type adult T cell leukemia (ATL leukemia). To our knowledge, they were the first cases of their type in Japan. In both cases, necrosis of the spinal cord was observed in the gray and white matter along most of its extent. Marked changes were found in the lumbar segment. The patients were not treated with intravenous cancer chemotherapy or irradiation. Immunohistochemical and electron microscopic examination revealed an extremely strong infection of herpes simplex virus (HSV) type 2. However, HSV type 1 and cytomegalovirus antigens were not detected.     

Central nervous system infection and immune response in mice inoculated into the lip with herpes simplex virus type 1

Virus may be recovered from various areas of the central nervous system (CNS) of mice for as long as 11 days after inoculation of herpes simplex virus type 1 (HSV-1) into the lip. The probability of isolation from any particular region of the CNS seems to be a function of the distance of that area from the root-entry zone of the trigeminal nerve. It is also mouse strain-dependent, with much more extensive evidence of brain infection being found in BALB/c and C3H rather than C57BL/6 mice, in which it is limited to the pons. The virus could not be isolated from the CNS of BALB/c mice after 10 days, though HSV-1 is readily recovered from the trigeminal ganglia at least through day 38. Significant concentrations of HSV-1-specific immunoglobulin (Ig) were demonstrated consistently in cerebrospinal fluid (CSF) from day 12 after exposure to virus. The persistence of relatively high concentrations of IgM in the CSF indicates that much of this antibody may be synthesized locally in the brain.     

The distribution of herpes simplex type 1 antigen in mouse central nervous system after different routes of inoculation

Herpes simplex type 1 virus was inoculated into 3-week-old mice via four different routes; intracerebral, intravenous, intranasal and directly into the sciatic nerve. Virus antigen-containing cells in the central nervous system were identified by both an immunofluorescence and immunoperoxidase method. The portal of entry of virus into the CNS appeared to be the major determinant of distribution of virus antigen. Direct haematogenous seeding of virus into the CNS was not proven. It seems probable that infection was first established in sensory ganglia. Within the CNS, regions of high virus antigen concentration paralleled high cell density suggesting cell to cell spread. Consistent involvement of certain neuron groups may be due to their selective vulnerability. These animal experiments provide some explanation for the patterns of CNS herpetic infection observed in man.     

Virus spread and initial pathological changes in the nervous system in genital herpes simplex virus type 2 infection in mice

Summary Mice were infected by the vaginal route with the MS strain of herpes simplex virus type 2 (HSV-2). Serial vaginal cultures were used to confirm infection and to select mice for this study. Two mice were killed by perfusion on days 2–6 post infection (p.i.) and lumbar and sacral cord with cauda were fixed and embedded for electron microscopy. Semithin Epon-sections were stained for viral antigen using a rabbit anti-HSV-2 antiserum and the Avidin-Biotin (ABC) method. Thin sections from antigen-positive blocks were examined by electron microscopy, and the number and types of infected cells detected by these two methods were compared. A good correlation was found between detection of infected cells by these methods. Infected cells included neurons of dorsal root ganglia and spinal cord, satellite cells of dorsal root ganglia, non-myelinating Schwann cells, astrocytes, oligodendrocytes and arachnoidal cells. Infected cells were first detected in the cauda on day 3 p.i. and in the spinal cord on day 5 p.i. The temporal and spatial distribution of infected cells was consistent with neural spread to and within the CNS. The pathological lesions showed a good correlation with the distribution and number of infected cells and are probably due to a direct virus effect. The similar sensitivity of the Epon-ABC method to electron microscopy in detecting infected cells indicates that this method may have useful applications in both experimental and diagnostic work.     

Differentiation of herpes simplex virus 1 and 2 in cerebrospinal fluid of patients with HSV encephalitis and meningitis by stringent hybridization of PCR-amplified DNAs

Differentiation of herpes simplex virus (HSV) types 1 and 2 in cerebrospinal fluid of 17 patients with serological1y diagnosed HSV encephalitis and meningitis or acute limbic encephalitis was determined by stringent hybridization of polymerase chain reaction — amplified DNAs. Ten of 17 patients were positive; six with HSV 1 isolates and four with HSV 2 isolates. We detected HSV type 1 in two cases of meningitis, although meningitis is generally thought to be caused by type 2. Additionally, HSV type 2 was found in one case of acute adult encephalitis, which is generally due to HSV type 1. HSV DNAs could be detected for over I month after onset, although our patients included several prolonged and recurrent cases. HSV DNA genomes were not detected in three cases of acute limbic encephalitis. Our study indicates that this method can be used for type differentiation in HSV CNS infections.     

Comparative analysis of intrathecal antibody synthesis and DNA amplification for the diagnosis of cytomegalovirus infection of the central nervous system in AIDS patients

We evaluated 49 paired cerebrospinal fluid (CSF) and serum samples of 35 patients infected with the human immunodeficiency virus type 1 (HIV-1) for laboratory evidence of cytomegalovirus (CMV) infection. The patients were grouped according to clinical criteria as probable CMV encephalitis/polyradiculomyelitis, CMV retinitis, cerebral toxoplasmosis, progressive multifocal leukoencephalopathy, HIV-1-related cognitive/motor complex, HIV-1-associated myelopathy, and other neurological diseases. Paired CSF and serum samples were analysed for CMV deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR), quantitative intrathecal synthesis of immunoglobulin G (IgG) antibodies specific for recombinant phosphoprotein 150 (pp150) of CMV and CMV-specific serum IgM. Intrathecal synthesis of pp150-specific IgG was detected in 26% of patients (9/35), serum IgM was found in 23% of patients (8/35), and PCR of CSF was positive in 11% of patients (4/35). Detection of CMV-specific DNA in CSF preceded the intrathecal antibody synthesis in three patients for whom serial samples were available. PCR results of the CSF became negative in one patient with CMV polyradiculomyelitis after successful therapy with 9-[2-hydroxy-l(hydroxymethyl) ethoxymethyl] guanine (DHPG). PCR has a higher diagnostic specificity in the acute phase of CMV infection than intrathecal antibody synthesis. The serum IgM response to CMV cannot be used to monitor a compartmentalized immune response in the central nervous system while an intrathecal immune response seems to be associated with recovery either spontaneously or as a result of treatment.     

Targets of herpes simplex virus type 1 infection in a mouse corneal model

Summary In animal models, spread of herpes simplex virus type 1 (HSV-1) from epithelial replication sites to the peripheral and central nervous system is known from analysis of individually dissected tissues. To examine virus spread in undissociated tissues, corneas of adult mice were inoculated with HSV-1. After 1 to 13 days groups of mice were perfused with formalin, and decalcified blocks of head and neck were embedded in paraffin. At intervals, serial sections were screened for HSV antigen. On days 1 and 2, viral antigen was restricted to cornea and conjunctiva but by days 3 and 4 was also seen in autonomic ganglia and the trigeminal system. On day 6, HSV antigen reached its maximum extent; infected sites included the trigeminal complex (ganglion, root, peripheral ophthalmic and maxillary branches and spinal nucleus and tract), ehtmoid sinus and olfactory buld, visual system, and autonomic ganglia (ciliary, pterygopalatine and superior cervical). Antigen progressively diminished on days 8 and 10, and was not detected on day 13. This method demonstrates a broader range of infected tissues and suggests a more complex pattern of HSV spread than has been previously recognized. Virus appears to reach the intracranial compartment by four different neural routes. When effects of higher and lower corneal inoculation doses were compared, a lower dose resulted in lower peak HSV titers in trigeminal ganglion and brain stem and later virus appearance in these tissues. Thus, dose may influence the kinetics of HSV spread from the peripheral inoculation site to the CNS.Supported in part by U.S.U.H.S. grant, R07396. the opinions or assertions contained herein are the private views of the authors and should not be construed as official or necessarily reflecting the views of the Uniformed Services University of the Health Sciences or Department of Defense. There is no objection to its presentation and/or publication     

Herpes simplex virus type 2 meningitis without genital lesions: An immunoblot study

Summary Two sexually active female patients presented with acute meningitis. The CSF abnormalities were severe and persistent. In spite of the absence of genital lesions, serological studies revealed a primary infection by herpes simplex virus type 2. An immunoblot study revealed intrathecal synthesis of anti-herpes antibodies early in the course of the disease.     

Exposure to herpes simplex virus,type 1 and reduced cognitive function

Herpes simplex virus, type 1 (HSV-1) causes cold sores, keratitis and rarely, fatal encephalitis. The infection is lifelong, with sensory ganglia serving as reservoirs of latent infection. Recently, exposure to HSV-1 has also been repeatedly associated with reduced cognitive function among healthy individuals without prior encephalitis. Though HSV-1 does not elevate risk for schizophrenia (SZ) per se, exposure is likewise associated with impaired cognitive functions among SZ patients. The range of cognitive changes observed in HSV-1 exposed persons has not been investigated systematically, nor is it known whether interaction between HSV-1 exposure and SZ related factors contributes to the impairment among SZ patients. Persons with or without schizophrenia/schizophreniform disorder (N = 298 total, DSM IV criteria) were assessed for HSV-1 exposure using serum HSV-1 antibody titers. The Penn Computerized Neurocognitive battery was used to assess eight cognitive domains with respect to accuracy and speed. There were no significant case–control differences in HSV-1 exposure. The SZ/schizophreniform disorder cases were significantly impaired in all cognitive domains compared with the controls. HSV-1 exposure was also associated with reduced cognitive function in the entire sample, but the magnitude of the effects and their patterns differed from the SZ related changes. Further, statistically significant interactions between HSV-1 exposure and SZ case status were not detected. HSV-1 exposure does not elevate risk for SZ, but it is associated with reduced function in specific cognitive domains regardless of SZ diagnostic status. An ‘epidiagnostic’ model for the association is proposed to explain the results.     

Resistance of rat CNS to brain stem infection with herpes simplex virus type 1

Infection of the CNS by herpes simplex type 1 (HSV-1) via the trigeminal route to the brain stem was elucidated in a rat model. In contrast to the earlier described cortical and hippocampal infection after intracranial injection, the CNS showed a profound resistance to HSV-1 infection when the virus was administred by nose inoculation, as judged by histopathology and immunohistochemistry. In contrast, when the distribution of HSV-1 in the brain was investigated after nose inoculation by polymerase chain reaction, viral DNA was detected at all levels from the ganglia to the cortex. When replication of HSV-1 was assayed in primary cell cultures of rat astrocytes derived from brain stem, striatum, hippocampus and cerebral cortex, significantly lower virus yields were obtained in brain stem-derived astrocytes cultures as compared with in cortex-derived astrocytes. This finding was independent of whether HSV-1 strains used originated from brains of patients suffering from herpes simplex encephalitis or from patients with oral cutaneous lesions and lacking neurological symptoms. Also, by immunocytochemistry of cultures after HSV-1 infection, a lower number of plaques were seen in brain stem-derived astrocytes as compared with cortex-derived astrocytes. The observed relative resistance of brain stem-derived astrocytes to replicate HSV-1 might contribute to the ability of the brain stem to withstand infection during reactivation of this virus in the trigeminal neurons.Financial support was received from the Swedish Medical Research Council, the Medical Society of Göteborg, the Swedish Medical Society, and the Faculty of Medicine, University of Göteborg     

The heterogeneity in the immune response and efficiency of viral dissemination in brain infected with herpes simplex virus type 1 through peripheral or central route

Using immunohistochemistry on adjacent brain sections, we studied the correlation between the dissemination of the virus, the inflammatory responses and the expression of major histocompatibility complex (MHC) proteins in rat brain infected with herpes simplex virus (HSV-1) F strain by either corneal scarification or intracerebral injection. Our results showed that the mortality of the corneally infected rats was much higher than that of the intracerebrally infected rats, due to a more extensive dissemination of the virus in the brain, particularly in the brain stem. The inflammatory responses were similar in brains infected through either route, as demonstrated by the expression of MHC I/II antigens on infiltrating lymphocytes, leukocytes and macrophage/microglia cells. While there was strong immunoreactivity for HSV-1 antigens in the cerebral cortex, the infiltrates were only located in subcortical areas, especially the hippocampus. Therefore, the distribution of these immune cells did not always overlap with the regions of viral infection. These results suggest that HSV-1 disseminate more efficiently from the peripheral to the central nervous system (CNS) than from CNS to CNS, which is independent of the immune responses, and that the cerebral cortex may immunologically respond to HSV-1 infection differently from other brain regions. Received: 16 June 1998 / Revised: 22 October 1998 / Accepted: 11 November 1998     

Valacyclovir treatment ameliorates the persistently increased pentylenetetrazol-induced seizure susceptibility in mice with herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) is an important pathogen related to epilepsy. We have shown previously that corneal inoculation of mice with HSV-1 causes acute spontaneous behavioral and electrophysiological seizures and increases hippocampal excitability and kainite-induced seizure susceptibility. In this study, we aimed to determine whether early-life HSV-1 infection in mice might cause short- and long-term enhanced susceptibility to pentylenetetrazol (PTZ)-induced seizures and to evaluate whether early antiviral drug therapy was effectively ameliorating this deficit. Seizure threshold was calculated by the latency of onset of the myoclonic jerk, generalized clonus, and maximal tonic-clonic convulsion. We demonstrate that the localization of viral antigens was predominantly within the bilateral temporal areas (amygdala, piriform, and entorhinal cortex) of HSV-1-infected mice. We also present evidence that mice of all HSV-1-infected groups had a shorter latency and higher severity to PTZ-induced seizures than in age-matched, mock-infected controls. Treatment of HSV-1-infected mice with valacyclovir, a potent inhibitor of HSV-1 replication, produced a dose-dependent decrease in the signs of neurological deficits, pathological damages, and PTZ-induced seizure severity. Our results are consistent with the hypothesis that early-life HSV-1 infection leads to persistent enhancement of neuronal excitability in limbic circuits, which could result in an overall increased propensity to induce seizures later in life. Additionally, prompt optimal antiviral therapy effectively decreases seizure susceptibility in HSV-1-infected mice by limiting the level of viral replication and inflammatory response induced by virus. The present study provides not only experimental evidence, but also a new therapeutic strategy in HSV-1-associated human epilepsy.     

Herpes simplex virus,type 1 invasion of the rabbit and mouse nervous systems revealed by in situ hybridization

Summary Using a³H-labelled virion DNA probe applied to tissue sections, we have previously identified the precise microscopic anatomical localtion of herpes simplex virus (HSV) during the acute and latent stages of infection of the mouse trigeminal ganglia and central nervous system (CNS). In the present investigation, we compared the mouse and the rabbit with respect to their ability to support acute and latent infections of trigeminal ganglionic and central nervous system neurons. We found that HSV-1, strain F, produced acute and latent infection of trigeminal ganglion cells in both mice and rabbits; however, lower levels of HSV-1 RNA were expressed in rabbit neurons as compared to mouse neurons, and many fewer neurons of the rabbit supported an acute infection than in the mouse. Studies of the trigeminal system within the CNS revealed that HSV-1 established latency more readily in the mouse than in the rabbit. The histopathology observed in acutely infected rabbit brain was less intense and less widespread than in mouse brain.Supported by the Medical Research Service of the Veterans Administration and by Institutional and Biomedical Research Support Funds awarded by the Dean of the Medical School, University of Utah     

Discrimination of herpes simplex virus types 1 and 2 cerebral infections in a rat model

Summary A rat model was used to evaluate intertypic differences after intracranial (i.c.) inoculation of herpes simplex virus (HSV) types 1 and 2 strains with regard to neurovirulence and neuropathology, and influence of age on susceptibility. In adult rats, HSV-1 strains were more virulent than HSV-2 strains. HSV-1 replicated to higher titers in the central nervous system (CNS) of rats, as compared with HSV-2. In rats of less than 2–3 weeks of age, HSV-1 and HSV-2 were equally virulent, but morphological examination of rat brains showed typespecific differences in pathology and viral distribution already at the early postnatal stage. After HSV-1 infection, neuronal infection of the hippocampus, followed by cortical infection and edematous destruction dominated, while a preponderance of meningitis and invasive encephalitis was seen after HSV-2 infection. We suggest that the rat might be a useful model for human HSV infection in the CNS with discrimination between HSV-1 and HSV-2 infections, also at the early postnatal stage.Supported by the Swedish Medical Research Council (proj. no. 4514 and 07121), the Göteborg Medical Society, and the Swedish Medical Society