Aminopeptidase activity in the brains of mice with chronic Toxoplasma gondii infections.

Aminopeptidase activity on beta-naphthylamide (NA) substrates was assayed in brain extracts from normal and Toxoplasma gondii-infected mice at 4 months postinfection. Correlations of levels of aminopeptidase activity, Toxoplasma-specific antibody production, and the number of brain cysts were studied in normal and Toxoplasma-infected mice. The Toxoplasma-specific antibody and the formation of cysts were markedly enhanced in the parasite-infected mice. The highest levels of activity for the NA substrates tested were observed in normal mice. In contrast, the activity levels were significantly lower in T. gondii-infected mice than in the corresponding normal mice. These results suggest an association between chronic toxoplasmosis and aminopeptidase activity in the parasite-infected host brain.