Experimental mumps virus-induced hydrocephalus: viral neurotropism and neuronal maturity.

In order to elucidate the relationship between virus neurotropism and neuronal maturity, two experiments were performed. First, mumps virus infectivity was compared among the different developmental stages of hamster brains inoculated with mumps virus by examining the immunohistochemical distribution of mumps virus antigen. Second, brain lesions resulting from mumps virus infection during the period of neuronal migration were histologically and ultrastructurally analyzed. Three groups of Syrian hamsters, Group E12 (fetuses on the 12th day of gestation), and Groups P2 and P30 (2 and 30 days old, respectively), were injected with mumps virus intraplacentally or intracerebrally. In Group P30, mumps virus antigen was observed specifically in ependymal cells and the choroid plexus. In addition to these areas, in Group P2, some neurons in layers II and III of the cerebral cortex also showed virus antigen immunoreactivity. In Group E12, mumps virus antigen accumulated primarily in the neuroepithelial cells within the ventricular zone. Neither specific intranuclear changes related to viral replication nor the formation of complete virions and nucleocapsids was observed. We conclude that mumps virus neurotropism to hamster brains is dependent on the degree of neuronal maturity and that mumps virus can induce an abortive infection and resultant neuronal cell necrosis in the immature developing hamster brain.