Astrocytosis and cathepsin D activity in experimental measles encephalomyelitis

The temporal relationship between the activity of cathepsin D (CD), the major brain acid proteinase, inflammatory cell infiltration and reactive astrocytosis was examined in a hamster model of measles virus infection of the central nervous system. Twenty-five day old hamsters were inoculated intracerebrally with the HBS strain of measles virus and sacrificed 6, 10, and 16 days later. Mean CD levels in aqueous extracts of infected brain were significantly elevated on days 10 and 16 compared to control animals. Histologic examination showed that while the degree of inflammatory cell infiltration did not correlate with the elevations in CD activity (r = .38), there was a correlation with the degree of astrocytosis (r = .995). This suggests that the increase in CD was due to astrocytic changes and not directly related to mononuclear inflammatory cell infiltration.