Spread of vesicular stomatitis virus along the visual pathways after retinal infection in the mouse

Summary Vesicular stomatitis virus (VSV) was injected into the left eyeball of 3-week-old mice and it infected the retinal ganglion cells. The infection spread rapidly along the visual pathways to the postsynaptic neurons in the contralateral superior collicle (SC) and lateral geniculate body (LGB). The distributional pattern of the viral immunoreactivity indicated an anterograde axonal transport of the infectious material. A subsequent spread to the ganglion cells of the right retina further indicated retrograde axonal VSV transport. Within the retina the infection spread from the ganglion cells to the pigment epithelium. Although a transneuronal spread of the VSV infection was observed, no VSV budding from or uptake in synaptic membranes was demonstrated ultrastructurally in the retina or the superior collicle. In the retina virions budded from the perikaryal and dendritic plasma membranes of the ganglion cells as well as from the nerve cell bodies of the inner and outer nuclear layers, but not from the receptor segments. In the superior collicle budding was also observed from the plasma membranes of nerve cell bodies and dendrites. In contrast, the intraocular injection of Sendai virus caused a limited retinal ganglion cell infection, with no further propagation in the retina or to the SC or LGB.     

Sleep and behavior during vesicular stomatitis virus induced encephalitis in BALB/cJ and C57BL/6J mice

Intranasal application of vesicular stomatitis virus (VSV) produces a well-characterized model of viral encephalitis in mice. Within one day post-infection (PI), VSV travels to the olfactory bulb and, over the course of 7 days, it infects regions and tracts extending into the brainstem followed by clearance and recovery in most mice by PI day 14 (PI 14). Infectious diseases are commonly accompanied by excessive sleepiness; thus, sleep is considered a component of the acute phase response to infection. In this project, we studied the relationship between sleep and VSV infection using C57BL/6 (B6) and BALB/c mice. Mice were implanted with transmitters for recording EEG, activity and temperature by telemetry. After uninterrupted baseline recordings were collected for 2 days, each animal was infected intranasally with a single low dose of VSV (5 × 10⁴ PFU). Sleep was recorded for 15 consecutive days and analyzed on PI 0, 1, 3, 5, 7, 10, and 14. Compared to baseline, amounts of non-rapid eye movement sleep (NREM) were increased in B6 mice during the dark period of PI 1–5, whereas rapid eye movement sleep (REM) was significantly reduced during the light periods of PI 0–14. In contrast, BALB/c mice showed significantly fewer changes in NREM and REM. These data demonstrate sleep architecture is differentially altered in these mouse strains and suggests that, in B6 mice, VSV can alter sleep before virus progresses into brain regions that control sleep.     

Spread of HSV-1 to the suprachiasmatic nuclei and retina in T cell depleted BALB/c mice

Following uniocular anterior chamber inoculation of the KOS strain of HSV-1 in euthymic BALB/c mice, virus spreads from the injected eye to the brain, and from the brain to the optic nerve and retina of the uninjected eye by day 7 post inoculation (P.I.), but the optic nerve and retina of the injected eye are not infected with virus. Infection of the optic nerve and retina of the injected eye is observed only in athymic mice or in mice depleted of both CD4⁺ and CD8⁺ T cells. To determine the role of T cells in virus spread, adult female BALB/c mice were thymectomized and T cell depleted. Mice were co-injected with the KOS strain of HSV-1 and RH116, a thymidine kinase-negative mutant of KOS containing the Escherichia coli lac Z gene. Animals were sacrificed on days 3–7 P.I., and the eyes and brains were examined for blue-stained, virus-infected cells. A difference in the timing of virus infection was observed in the area of the suprachiasmatic nuclei only in mice depleted of both CD4⁺ and CD8⁺ T cells, and in this group, the contralateral suprachiasmatic nucleus was infected two days earlier. Since one route by which virus could infect the retina of the injected eye is via connections of the contralateral suprachiasmatic nucleus to the ipsilateral optic nerve, these findings suggest that (a) retinitis observed in the injected eyes of mice depleted of both CD4⁺ and CD8⁺ T cells results from virus infection of the contralateral suprachiasmatic nucleus followed by spread of virus to the ipsilateral optic nerve and retina and (b) early HSV-1 infection of the contralateral suprachiasmatic nucleus is prevented by a T cell dependent mechanism.     

T Lymphocyte infiltration in the brain following anterior chamber inoculation of HSV-1

Following inoculation of the KOS strain of herpes simplex virus type 1 (HSV-1) into one anterior chamber of euthymic BALB/c mice, virus spreads from the injected eye to the central nervous system and from the central nervous system to the optic nerve and retina of only the uninoculated eye. In contrast, in athymic BALB/c mice or mice depleted of both CD4⁺ and CD8⁺ T cells, virus spreads to the optic nerve and retina of both the injected eye and the uninjected eye. To determine the location in the central nervous system where spread of virus to the optic nerve and retina of the injected eye is prevented, euthymic BALB/c mice were injected with a mixture of KOS and RH116, a mutant of KOS that contains the Escherichia coli β-galactosidase (β-gal) gene. Several animals were sacrified each day; serial frozen sections of the brain were prepared and sequential sections were stained for β-gal or for T cells. At all sites except the suprachiasmatic nuclei, virus and T cells arrived at approximately the same time. However, at day 5 post inoculation (PI), T cells were present in both the ipsilateral and the contralateral suprachiasmatic nuclei, but only the ipsilateral suprachiasmatic nucleus was virus-positive. Since virus spreads from the ipsilateral suprachiasmatic nucleus to the contralateral optic nerve, these results suggest that T cells infiltrating the area of the contralateral suprachiasmatic nucleus prior to the arrival of virus at this site prevent virus spread into the optic nerve of the inoculated eye.     

Effects of thymosin α1 on the development of amoeboid microglial cells in the corpus callosum of neonatal BALB/c and athymic mice

The present study investigated the effects of intraperitoneal injections of thymosin α1 on the supraventricular amoeboid microglial cells (SAMC) in the newborn athymic and normal BALBrc mice. The microglial cells labelled by the lectin GSA I-B4 and the antibody Mac-1 showed a 27% reduction in number in the athymic mice receiving thymosin α1 injections compared with those receiving vehicle injections, and a 37% reduction in BALB/c mice receiving thymosin α1 injections compared with those receiving vehicle injections. Some of the SAMC in both BALB/c and athymic mice receiving thymosin α1 injections became ramified, while the remainder still exhibited their normal amoeboid appearance with few filopodial processes. Ultrastructurally, the lectin reaction product was confined to the plasma membrane and some cytoplasmic vacuoles of labelled SAMC. In both BALB/c and athymic mice, some labelled microglial cells became slender or elongated after thymosin α1 injections. Also their cytoplasm was reduced and contained fewer organelles. Radioimmunoassay of the plasma of thymosin α1 and vehicle-injected mice showed that there was a significant increase in the cortisol level in BALB/c (P <0.01) and athymic (P <0.001) mice 5 days after thymosin α1 injections, compared with that of the control mice. The results point to a strong correlation between the reduction of SAMC and the increased level of plasma cortisol. Supporting this is the fact that cortisol is known to suppress the production of monocytes considered to be the precursors of amoeboid microglia.     

Modulatory effects of d-serine and sarcosine on NMDA receptor-mediated neurotransmission are apparent after stress in the genetically inbred BALB/c mouse strain

Abnormalities of NMDA receptor-mediated neurotransmission are involved in the pathophysiology of schizophrenia, Alzheimer's disease, substance abuse and seizure disorders. The NMDA receptor is implicated in schizophrenia because phencyclidine (PCP), a noncompetitive NMDA receptor antagonist, binds to a hydrophobic domain within the channel, precipitating a schizophreniform psychosis in susceptible persons. Pharmacological, environmental, and genetic variables alter NMDA receptor-mediated neurotransmission. Inbred mouse strains differ in their sensitivity to some of the behavioral effects of MK-801 (dizocilpine), a PCP analogue. The NMDA receptor complex in the BALB/c strain could reflect a unique stoichiometric combination of receptor subunits resulting in a higher proportion of the channels in the open configuration, a higher affinity of MK-801 for its hydrophobic channel domain, and/or a combination of the above. The BALB/c mouse strain, "stressed" mice, and behavioral consequences of MK-801 administration represent models of altered glutamatergic neural transmission. We were interested in examining the effect of stress on the modulatory properties of d-serine and sarcosine. d-Serine is a naturally occurring glycine agonist that modulates the ability of l-glutamate to influence the opening of the NMDA receptor-associated ionophore, and sarcosine is a naturally occurring glycine reuptake inhibitor. The data suggest that 24h after stress, d-serine and sarcosine interact synergistically to reduce MK-801's ability to antagonize electrically precipitated tonic hindlimb extension. Under conditions of stress, modulatory effects of d-serine and sarcosine on the antiseizure effect of MK-801 are observed that are not apparent in the nonstress condition. The results could be relevant to the development of glycinergic interventions for the treatment of neuropsychiatric disorders.