Highly infectious rubella virus cDNA clones derived from infectious cDNA clone
having a low specific infectivity and methods of obtaining highly infectious rubella
virus cDNA clones. Togavirus expression vectors of improved stability for the expression
of live, attenuated togavirus and a foreign gene, based on the nucleic acid sequence
of an infectious rubella virus clone and contain a togavirus non-structural protein
open reading frame; an expression element for expression of a foreign gene; a foreign
gene or a multiple cloning site for insertion of a foreign gene; an expression
element for the expression of the live, attenuated togavirus; and a togavirus structural
protein open reading frame. The expression element is either a subgenomic promoter
or an internal ribosome entry site (IRES). Administration of the vector as an immunization
agents is useful for the induction of immuity against the togavirus, the foreign
gene, or both.