Encephalitis induced by bovine herpesvirus 5 and protection by prior vaccination or infection with bovine herpesvirus 1.
Calves were intranasally challenged with bovine herpesvirus 5 (BHV5) and followed for the development of viral infection, clinical encephalitis, histologic lesions in the brain, and viral sequences in the trigeminal ganglia. Calves that were previously vaccinated with bovine herepesvirus 1 (BHV1, n = 4) or previously infected with BHV1 (n = 5) or that had not been exposed to either virus (n = 4) were compared. No calf developed signs of encephalitis, although all calves developed an infection as indicated by nasal secretion of BHV5 and seroconversion to the virus. Histologic lesions of encephalitis consisting of multifocal gliosis and perivascular cuffs of lymphocytes were observed in calves not previously exposed to BHV1. BHV5 sequences were amplified from the trigeminal ganglia of calves previously vaccinated and from calves not previously exposed to BHV1; calves sequentially challenged with BHV1 and later BHV5 had exclusively BHV1 sequences in their trigeminal ganglia. Administration of dexamethasone 28 days after BHV5 challenge did not influence clinical disease or histologic lesions in either previously unexposed calves (n = 2) or previously immunized calves (n = 2), although it did cause recrudescence of BHV5, as detected by nasal virus secretion. (+info)
Role of nitric oxide in pathogenesis of herpes simplex virus encephalitis in rats.
The role of nitric oxide (NO) in the pathogenesis of viral encephalitis was investigated by using an experimental model of herpes simplex virus type 1 (HSV-1) encephalitis in Lewis rats. The expression of inducible NO synthase (iNOS) mRNA determined by Northern blotting was observed first in the olfactory bulb and the brain stem on day 5 after intranasal inoculation of HSV-1, and thereafter iNOS mRNA was detected in other brain regions, i.e., cerebrum and cerebellum. In various parts of the brain, excessive NO production was identified by electron spin resonance spectroscopy. The temporal and spatial patterns of iNOS expression coincided with those of viral propagation, as demonstrated by polymerase chain reaction for HSV-1 gene expression as well as by the plaque-forming assay. Immunohistochemical study determined that iNOS was localized mainly in monocyte-derived macrophages. Treatment of virus-infected animals with the NOS inhibitor Nomega-monomethyl-l-arginine (l-NMMA), but not Nomega-monomethyl-d-arginine, significantly ameliorated not only clinical symptoms such as paralysis and seizures but also mortality. Virus yield from brain tissue was not affected by l-NMMA treatment. It is of interest that increased expression of the antioxidant enzyme heme oxygenase-1 was observed in the HSV-1-infected brain; this increased expression was strongly inhibited by l-NMMA treatment. These data suggest that the high level of NO produced by iNOS is a pathogenic factor in HSV-1-induced encephalitis in rats. (+info)
Virus infection induces neuronal apoptosis: A comparison with trophic factor withdrawal.
Multicellular organisms can employ a number of defences to combat viral replication, the most dramatic being implementation of a cell autonomous apoptotic process. The overall cost to the viability of an organism of losing infected cells by apoptosis may be small if the dying cells can be substituted. In contrast, suicide of irreplaceable cells such as highly specialised neurons may have a more dramatic, even fatal consequence. Previous in vitro approaches to understanding whether neurotropic viruses cause neurons to apoptose have utilised transformed cell lines. These are not in the appropriate state of differentiation to provide an accurate indication of events in vivo. We have chosen to characterise the ability of a model CNS disease-causing virus, Semliki Forest virus (SFV), to infect and trigger apoptosis in primary cultures of nerve growth factor (NGF)-dependent sensory neurons. These cells are known to die when deprived of NGF and constitute a useful indicator of apoptosis. We observe that infection causes cell death which bears the morphological hallmarks of apoptosis, this occurs even in the present of survival promoting NGF and is concomitant with new virus production. Using the TUNEL (transferase dUTP nick end labelling) technique we show that SFV-induced apoptosis involves DNA fragmentation and requires caspase (CED-3/ICE cysteine protease) activation, as does apoptosis induced by NGF-deprivation. Extensive areas of apoptosis, as defined using a combination of ultrastructural analysis and TUNEL occur in infected neonatal mouse brains. The novel evidence that infection of primary neurons with SFV induces apoptosis with activation of one or more caspases defines a system for the further anlaysis of apoptosis regulation in physiologically relevant neurons. (+info)
Ectopic expression of DNA encoding IFN-alpha 1 in the cornea protects mice from herpes simplex virus type 1-induced encephalitis.
A novel approach to combat acute herpes simplex virus type 1 (HSV-1) infection has recently been developed by administration with a plasmid DNA construct encoding cytokine genes. Cytokines, especially type I IFNs (IFN-alpha and IFN-beta) play an important role in controlling acute HSV-1 infection. The purpose of the present study was to investigate the potential efficacy of ectopically expressed IFN-alpha 1 against ocular HSV-1 infection following in situ transfection of mouse cornea with a naked IFN-alpha 1-containing plasmid DNA. Topical administration of the IFN-alpha 1 plasmid DNA exerted protection against ocular HSV-1 challenge in a time- and dose-dependent manner and antagonized HSV-1 reactivation. In addition, IFN-alpha 1-transfected eyes expressed a fivefold increase in MHC class I mRNA over vector-treated controls. The protective efficacy of the IFN-alpha 1 transgene antagonized viral replication, as evidenced by the reduction of the viral gene transcripts (infected cell polypeptide 27, thymidine kinase, and viral protein 16) and viral load in eyes and trigeminal ganglia during acute infection. The administration of neutralizing Ab to IFN-alpha beta antagonized the protective effect of the IFN-alpha 1 transgene in mice. Collectively, these findings demonstrate the potential of using naked plasmid DNA transfection in the eye to achieve ectopic gene expression of therapeutically active agents. (+info)
Laboratory diagnosis of common viral infections of the central nervous system by using a single multiplex PCR screening assay.
A multiplex PCR assay that detects the four commonest causes of viral meningitis and encephalitis in the United Kingdom (herpes simplex virus [HSV] type 1 [HSV-1], HSV type 2 [HSV-2], varicella-zoster virus [VZV], and enteroviruses) was developed, and its sensitivity was compared with those of similar assays described previously for this application. Compared to the previous assays, this single multiplex PCR assay had higher molecular sensitivities for the detection for each of the viruses and improved utility for routine use in a diagnostic laboratory. The assay was used to test a series of 1,683 consecutive cerebrospinal fluid (CSF) samples between June 1997 and March 1998 inclusively. Viral nucleic acid was detected in 138 (8.2%) of the CSF samples, including enteroviruses in 51 samples, HSV-2 in 33 samples, VZV in 28 samples, and HSV-1 in 25 samples. Compared to the accepted relative incidence of viral etiologies, aseptic meningitis due to HSV-2 infection was high, and in adult female patients with symptoms of aseptic meningitis, HSV-2 was the virus most commonly detected in the CSF. (+info)
Outbreak of Hendra-like virus--Malaysia and Singapore, 1998-1999.
During September 29, 1998-April 4, 1999, 229 cases of febrile encephalitis (111 [48%] fatal) were reported to the Malaysian Ministry of Health (MOH). During March 13-19, 1999, nine cases of similar encephalitic illnesses (one fatal) and two cases of respiratory illness occurred among abattoir workers in Singapore. Tissue culture isolation identified a previously unknown infectious agent from ill patients. This report summarizes the preliminary epidemiologic and laboratory investigations of these cases, which indicate that a previously unrecognized paramyxovirus related to, but distinct from, the Australian Hendra virus is associated with this outbreak. (+info)
Long term neurological outcome of herpes encephalitis.
Twenty eight children with herpes simplex encephalitis were followed up for a mean of 5.5 years. Two children died and 26 survived, of whom 16 were left with no neurological sequelae and 10 had persistent neurological sequelae. Mean (SD) Glasgow coma score was significantly lower in the patients with neurological sequelae (7.7 (1.5)) and the patients who died (4.5 (0.7)), compared with the patients without neurological sequelae (11 (1.7)). (+info)
Update: outbreak of Nipah virus--Malaysia and Singapore, 1999.
During March 1999, health officials in Malaysia and Singapore, in collaboration with Australian researchers and CDC, investigated reports of febrile encephalitic and respiratory illnesses among workers who had exposure to pigs. A previously unrecognized paramyxovirus (formerly known as Hendra-like virus), now called Nipah virus, was implicated by laboratory testing in many of these cases. Febrile encephalitis continues to be reported in Malaysia but has decreased coincident with mass culling of pigs in outbreak areas. No new cases of febrile illness associated with Nipah virus infection have been identified in Singapore since March 19, 1999, when abattoirs were closed. This report summarizes interim findings from ongoing epidemiologic and laboratory investigations in Malaysia and Singapore. (+info)