Herpes simplex virus-host cell relationships in organized cultures of mammalian nerve tissues

Replication of rabies virus in organized cultures of Mammalian neural tissues

Organized cultures of dorsal root ganglion and spinal cord ganglion from rat and mouse were used as a model to study the pathogenesis of rabies infection in neural tissue. Two strains of fixed virus and one of street virus were used. Virus replication was similar to that detected in other rabies virus host cell systems, although virus yields remained in relatively low titer. Sequential observations of individual neurons in organized cultures revealed that cytopathic effects usually became evident at 3 days and progressed from cytoplasmic granulation to complete neuronolysis. It was shown by electron microscopy that a small percentage of the inclusion bodies, which appeared in the neurons as well as glial cells, were associated with virus assembly. These findings were similar, regardless of strain of virus employed. Previous experiments done in vivo have shown differences in the type of cytopathic effect produced by street virus and by fixed virus. It is thought that the combination of host cell system and strain of virus is important in determining the course of infection.

Herpes simplex virus type-2 infection by a footpad route results in neuronal death in mouse spinal ganglia

We have examined the effects of herpes simplex virus type 2 (HSV-2) infection on neuron numbers in mouse dorsal root ganglia (DRG) following unilateral hind footpad inoculation. One month following HSV-2 strain MS inoculation, tissue sections of decalcified spine containing the paired 4th and 5th lumbar DRGs were stained with cresyl violet. Neuronal numbers, somal areas and ganglion volumes were determined for ganglia ipsilateral and contralateral to both HSV-2 and medium inoculations. One month following HSV-2 infection, 47-88% of neurons disappeared in the ipsilateral ganglia. The somal areas of the remaining neurons in these ganglia fell within the range of the uninfected population. Ganglionic shrinkage did not occur as a result of HSV-2 infection; neurons were replaced by large numbers of inflammatory cells. Neuron numbers in the contralateral control ganglia of the HSV-2 inoculated mice appeared slightly decreased. Mice inoculated with medium contained similar numbers of neurons in ipsilateral and contralateral ganglia. These results show that, in addition to other previously described host alterations, infection with HSV-2 strain MS results in neuronal death in the affected host ganglia. This is the first in vivo quantitative documentation of neuronal death induced by herpes simplex virus infection.

Herpes simplex virus infection induces a selective increase in the proportion of galanin-positive neurons in mouse sensory ganglia

We examined the effects of herpes simplex virus type 2 (HSV-2) infection on host neuropeptide content in mouse dorsal root ganglia (DRG) neurons following unilateral hind footpad inoculation. At selected survival times following infection, adjacent tissue sections of decalcified spine containing the paired 4th and 5th lumbar DRGs were immunoreacted to detect HSV-2, calcitonin gene-related peptide (CGRP), or galanin antigen. Labeled and unlabeled neurons were counted and the somal areas for all neurons in the infected and the contralateral uninfected DRG in each mouse were compared. HSV-positive neurons were small. HSV-2 antigen was present in neurons at Day 5; by Day 14 the antigen had disappeared. Galanin positivity was first seen at Day 8, peaked at Day 14, gradually declined on Days 21 and 28, and returned to control values by Day 42. The mean soma size of the labeled population was small. Galanin antigen was not seen in DRG at any time following sham inoculation. At all times after infection, equal numbers of CGRP-positive neurons were seen in infected and uninfected ganglia and in sham-operated mice. These results show that HSV-2 infection differentially affects host neuropeptide production and that nervous system effects are not restricted to the acute stage of infection. These events are consistent with those seen in other injury/regeneration paradigms.

Nerve growth factor deprivation results in the reactivation of latent herpes simplex virus in vitro

Primary sympathetic neuronal cultures were maintained for up to 5 weeks after inoculation with herpes simplex virus (HSV) without evidence of viral infection. Upon deprivation of nerve growth factor, the cultures produced infectious HSV, indicating that the cultures harbored latent HSV. This study demonstrates a function of nerve growth factor in the maintenance of HSV latency.

Use of aggregating brain cultures to study the replication of herpes simplex virus types 1 and 2 in central nervous system tissue

A novel tissue culture system consisting of reaggregated embryonic mouse brain cells was used to examine the replication of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) within central nervous system tissue. Brain aggregates cultured 30-40 days in vitro demonstrated progressive maturation and differentiation into cells recognizable as neurons, astrocytes and oligodendrocytes, with the latter cell type exhibiting myelin production. Mature aggregates were infected with HSV and sampled at timed intervals postinfection for morphological, virological, and biochemical assays. By electron microscopy mature nucleocapsids were observed in the nucleus of peripheral cells at 9 h and in all cell types by 33 h. Virus-specific antigens were observed, using the immunoperoxidase test, within peripheral cells at 12 h postinfection (p.i.). By 24 h p.i., antigen production had progressed throughout the infected aggregates. Growth curves of HSV-1 and HSV-2 for intracellular and extracellular infectious virus production correlated well with virus-induced morphological changes and antigen production. SDS-polyacrylamide slab gel electrophoresis of isotopically-labelled proteins and glycoproteins synthesized from 4 to 24 h p.i. in virus-infected aggregates revealed typical HSV-1 polypeptide profiles and HSV-1 and HSV-2 glycoprotein profiles. Our results suggest that aggregating brain cultures may provide a useful and more accurate in vitro model for the study of HSV-induced neurological disease.

Herpes simplex virus infection of isolated autonomic neurons in culture: viral replication and spread in a neuronal network

Cultures of isolated neurons, derived from the superior cervical ganglion (SCG) of the newborn rat and maintained in the absence of nonneuronal cells, were infected with herpes simplex virus (HSV) type 1. By phase-contrast microscopy, including time-lapse cinematography, cytopathologic changes appeared first in neuronal cell bodies and only approximately 24 hours later were axonal abnormalities detectable. Despite low yields of viral progeny, infection spread readily within the two-dimensional network of neurons and their processes. Immunoperoxidase staining for viral antigens confirmed the replication and spread of virus and revealed that antigen extended along axons during infection. Antiviral antibody added to the overlay medium slowed but did not prevent the spread of infection, indicating that virus passed from neuron to neuron over axonal pathways. Despite alteration of neuronal macromolecular synthesis early in infection, axonal transport is apparently preserved long enough to allow propagation of virus over interconnecting neural pathways.

Herpes simplex virus replication in pheochromocytoma cell line that responds to nerve growth factor

Cultured cells of neural origin (PC-12, pheochromocytoma cell line) respond to nerve growth factor (NGF) by extending neurites. These cells whether treated with NGF or not can be infected with herpes simplex virus and produce progeny virus. Viral antigens are detected on the cell surface and fusion of cells to form polykaryocytes takes place. Nucleocapsids are found within the cell nucleus and enveloped virus in a present both in the cytoplasm and extracellular space. Virus was not observed within the neurites but laterations in the neurite microtubular structure occurred after infection.

The effects of measles virus and various strains of SSPE virus on organotypic cultures of nervous tissue

The neurotropic effects, virologic behaviors and morphologic appearances of 4 strains of subacute sclerosing panencephalitis (SSPE) virus have been examined in organotypic cultures of hamster cerebellar tissue and have been compared with the Edmonston strain of measles virus in the same system. While measles virus caused extensive damage to nervous tissue, the SSPE strains, in general, exerted a less deleterious effect. All of the SSPE viruses replicated in this tissue. The SSPE strains showed morphologic variation ranging from normal measles-type virions to apparently nucleocapsid deficient forms. It is speculated that some of these differences between measles and SSPE virus may account for the differences in the in vivo conditions with which they are associated.

Vascular and neuroglial changes in experimental herpes simplex encephalitis: ultrastructural study

Generalized vascular changes and diffused proliferation of reactive microglia were observed in an experimental model of HSV encephalitis of mice. The wide spread of these changes contrasted with the localized character of virus replication and the confined areas of damaged nervous tissue. The vascular and microglial changes were precocious in animals inoculated with concentrated virus suspension (10(5.5)LD50) while they appeared late in mice inoculated with diluted virus suspension (100 LD50). After inoculation with U.V. inactivated virus no changes were seen. The results obtained in this study suggest that the vascular and microglial modifications are not related to a direct cytopathic effect of the virus but dependent on the amount of virus present in the central nervous system and linked to the virus DNA.

Demyelination and cytopathic effects in cultures of mammalian dorsal root ganglia infected with encephalomyocarditis virus

Replication of encephalomyocarditis virus and its cytopathic effects were studied in myelinated cultures of dorsal root ganglia obtained from newborn mice. Six hours after infection virus progeny was detected in the culture. At 24 h the virus titer reached 2 times 10(6) PFU per culture and remained at this level until 48 h. The first cytopathic alterations began at 24 h and consisted of rounding of Schwann and satellites cells and their detachment from neurons. Later, bead-like swellings of the myelin appeared along the axons followed by splitting and degeneration of lamellae. The cytopathic effect in the neurons started 29 h after infection, reaching complete neuronolysis at 48 h. Virus particles, scattered or arranged in crystal-like aggregates, were first seen in the cytoplasm of glial cells and then in neurons and axons.

Ultrastructure of Junín virus in mouse whole brain and mouse brain tissue cultures

Comparative ultrastructural studies were performed on the development of Junín virus in mouse brain and in cerebellum explants and brain monolayers of the same animal. In mouse brain, neurons and astrocytes released virus particles by a budding mechanism identical to that previously described for this virus. In the neurons, the viral multiplication took place in the perikarion as well as in the cytoplasmic processes, including areas near synapses. Viral particles were observed emerging from pericapillary neurons and astrocytes. In the explants, the budding also occurred in neurons and astrocytes. In the monolayers, however, the virus originated in astrocytes and cells of fibroblastic appearance, which were the two cell types that developed in this substrate. These results indicate that the characteristics of the development of Junín virus in mouse brain are faithfully reproduced in cerebellum explants from the same animal, thus allowing some extrapolation of data from one system to the other. The explant proved to be a better model than the monolayer, not only because it reproduced the structural complexity of nervous tissue better, but also because it contains neurons and astrocytes, i.e., the two cell types that release the virus in the in vivo system.

Ultrastructural study of long-term measles infection in cultures of hamster dorsal-root ganglion

The morphogenesis of the Edmonston strain of measles is described in cultures of hamster dorsal-root ganglion maintained for as long as 63 days postinoculation. The patterns observed confirmed those previously reported in both neural and non-neural tissue. However, in the present tissue, the development of viral material could be followed chronologically within different cell types such as neurons and Schwann cells. Active replication was visualized up to 63 days postinoculation. The appearance of cytoplasmic nucleocapsid preceded that of intranuclear nucleocapsid, the latter occurring after 14 days. These intranuclear inclusions were formed after the transformation of the nucleoli into bizarre pleomorphic bodies which eventually segregated into clumps of nucleocapsid. These intranuclear inclusions mimic those seen in subacute sclerosing panencephalitis, now known to be etiologically related to a measles-like virus.

Ultrastructure of measles virus in cultures of hamster cerebellum

Replication of Edmonston strain of measles virus in cultures of hamster central nervous system tissue was studied by electron microscopy of ultrathin sections. Infected cultures were fixed from 3 hr to 39 days postinoculation (PI). Measles nucleocapsid was first seen within the cytoplasm of giant cells, the latter appearing 5 to 6 days PI. Measles virus particles were most abundant at 10 days PI and appeared to bud off from areas of the cell membrane along which nucleocapsid was aligned. Intranuclear nucleocapsid was more abundant at later stages, and by 39 days PI entire nuclei were seen to be occupied. By this time, the cytoplasmic formations, which had been sequestered by membranes, appeared to lose their regular structure. Budding viral particles at 39 days PI were of a much simplified structure and did not involve the alignment of nucleocapsid about their periphery.