Measles virus encephalitis and retinopathy in the Wistar rat

Spread of measles virus through axonal pathways into limbic structures in the brain of TAP1 -/- mice

The spread of measles virus into the brain was studied exploiting the olfactory pathway, which represents an important route of neuroinvasion by viruses. The virus was injected into the main olfactory bulb of wild-type mice and mice with disrupted TAP1 gene (TAP refers to the Transporter associated with Antigen Presentation), which codes for products essential for the cell-mediated immune response. Virus invasion was monitored for 4 weeks by immunohistochemistry. The distribution of measles virus was found to be restricted to brain areas connected with the olfactory bulbs. However, in the wild-type mice there was a marked infiltration of lymphocytes in the infected brain structures, and the virus did not pass beyond the piriform cortex. In the TAP1 -/- mice the virus spread more extensively along olfactory projections into the limbic system and monoaminergic brainstem neurons. Infected mice of both types developed seizures, which may have been focally evoked from the piriform cortex. This study provides evidence that measles virus can spread through axonal pathways in the brain. The findings obtained in the gene-manipulated mice point out that a compromised immune state of the host may potentiate targeting of virus to the limbic system through olfactory projections.

Susceptibility of human retinal pigment epithelial cells to different viruses

BACKGROUND

Different viruses have been reported to be involved in retinal diseases in animal systems. In humans, herpes simplex virus and cytomegalovirus have been found to cause retinal disease. Most of the studied viruses are neurotropic. In this study, the in vitro susceptibility of human retinal pigment epithelial cells (RPEC) to representative members of different groups of human pathogenic viruses was investigated.

METHODS

Early cultures of RPE C - after two or three passages - were infected with the following viruses: herpes simplex virus (HSV) type 1, human herpesvirus 6 (HHV-6), Epstein-Barr virus (EBV), cytomegalovirus (CMV), adenovirus types 1 and 7, measles virus, parainfluenza virus and coxsackie virus B3.

RESULTS

Cultures of RPE C could be infected with neurotropic viruses like HSV or measles virus as well as with typical respiratory viruses like parainfluenza or adenoviruses. Coxsackievirus, an enterovirus, replicated as well as human CMV, whereas EBV and HHV-6, two lymphotropic viruses, failed to infect RPE.

CONCLUSION

These findings suggest that a variety of viruses, including those causing rather common illnesses, might be capable of inducing retinal lesions under certain circumstances due to haematogenous spread during the course of viraemia.

Induction of class I and class II transplantation antigens in rat brain during fatal and non-fatal measles virus infection

Measles virus induced a marked increase in the expression of MHC-coded class I and class II antigens as detected by immunostaining during both fatal and non-fatal brain infections in rats. The distribution of these molecules in the brain was much more widespread than the occurrence of viral antigen suggesting a soluble factor for their induction. In 14-day-old rats with a non-fatal infection there was a marked infiltration of T lymphocytes of 'cytotoxic/suppressor' phenotype in the brain parenchyma, whereas T 'helper' cell phenotypes mainly were located perivascularly. In brains from newborn rats with a fatal infection no or only few lymphocytes were detected.

Central nervous system lesions in suckling mice and rats inoculated intranasally with sialodacryoadenitis virus

Suckling CD-1 and CFW mice and WI Wistar rats were inoculated intranasally with sialodacryoadenitis virus. In animals inoculated during the first week of life, there was an acute necrotizing encephalitis with malacia and minimal inflammatory cell response. In mice and rats which survived for up to 12 days post inoculation, loss of brain substance, gitter cells and occasionally mineralized debris were seen. Viral antigen was readily demonstrated in neurons and nasal epithelium in trypsin-treated, paraffin-embedded sections, and corresponded with the presence of lesions. There was no compelling evidence that sialodacryoadenitis virus invaded the central nervous system directly via the cribriform plate, and hematogenous spread was considered to be a likely route of spread to the brain. An age-related resistance to the encephalitic form was evident beginning at 10 days of age in both species. Thus it is conceivable that encephalitis could occur in young suckling rats exposed during naturally-occurring epizootics of sialodacryoadenitis.