Lysosomal enzyme changes in macrophages from mice given myocrisin and infected with avirulent Semliki Forest virus.

Myocrisin given to mice i.p. causes depression of lysosomal enzyme activity (acid phosphatase, beta-glucuronidase and N-acetyl-beta-D-glucosaminidase) in peritoneal macrophages. If avirulent Semliki Forest virus (SFV) is given i.p. 3 h after the Myocrisin, further depression of lysosomal enzyme activity occurs, a very high titre of virus is produced in these macrophages and the virus becomes lethal, causing 100% mortality. The possible interrelationships between depressed lysosomal activity, high virus titres and the production of a lethal virus infection are discussed.