RUBELLA-VIRUS REPLICATION COMPLEXES ARE VIRUS-MODIFIED LYSOSOMES

Replication complexes are membrane-bound cytoplasmic vacuoles involved in rubella virus (RV) replication. These structures can be identified by their characteristic morphology at the electron microscopy (EM) le vel and by their association with double-stranded (ds) RNA in immunogo ld labeling EM studies. Although these virus-induced structures bear s ome resemblance to lysosomes, their exact nature and origin are unknow n. In this study, the localization of two lysosomal markers, lysosomal -associated membrane protein (Lamp-1) and acid phosphatase, relative t o the replication complexes was examined by light and electron microsc opy. Confocal microscopy using antibodies to dsRNA and Lamp-1 showed c olocalization of these two markers in the cytoplasm of RV-infected cel ls. Immunogold labeling EM studies using antibodies to Lamp-1 confirme d that Lamp-1 was associated with RV replication complexes. EM histoch emical studies demonstrated the presence of acid phosphatase in the va cuoles of RV replication complexes. Taken together, these studies show that RV replication complexes are virus-modified lysosomes. (C) 1998 Academic Press.