Expression of soluble forms of rubella virus glycoproteins in mammalian cells

Rubella virus (RV) virions contain two envelope glycoproteins, E1 and E2. Removal of hydrophobic regions in their carboxyl termini by genetic engineering caused them to be secreted rather than maintained in cell membranes of transfected COS cells. Truncated E2 was secreted in the absence of E1, whereas E1 lacking its transmembrane domain required coexpression of E2 for export from the cell. Secreted E2 was found to contain both O-linked and N-linked complex glycans, whereas secreted E1 retained virus neutralization and hemagglutination epitopes, suggesting the possibility of using soluble RV antigens as subunit vaccines and for serodiagnostic purposes. Stable Chinese hamster ovary cell lines secreting RV E1 were constructed for large scale preparation of recombinant E1.