Secretion of rubella virions and virus-like particles in cultured epithelial cells

Rubella virus (RV) is an enveloped RNA virus that causes systemic infection s in humans. More importantly, first trimester in utero infection leads to a collection of devastating birth defects known as congenital rubella syndr ome. Epithelial cells are the first line of defense against viruses and con sequently, the polarity of virus secretion is an important factor affecting viral spread. As a first step toward understanding how RV interacts with e pithelial cells, we have examined the release of RV-like particles and viri ons from polarized cells in culture. RV structural proteins were targeted t o the Golgi complex and virus particle formation occurred on intracellular membranes in three different polarized epithelial cells. Polarized cells co uld be infected from the apical and basal membranes, indicating that recept ors are not confined to one surface. The secretion of virus-like particles and infectious virions varied according to cell type. In two of the three p olarized cell lines examined, virus was released primarily from the apical surface, but significant quantities were also secreted from the basolateral membrane. Release of virus from the apical surface may facilitate virus sp read from person to person, whereas basolateral secretion could be importan t for establishing a systemic infection and/or crossing the placenta prior to fetal infection. (C) 1999 Academic Press.