Stable expression of a foreign protein by a replication-competent rubella viral vector.

Live, attenuated rubella vaccine has been used successfully for many years. By expressing additional viral antigens in rubella, we could expand its range and utility as a live, replicating viral vector. Previously, limitations on insert size and stability restricted rubella's ability to express exogenous antigens and immunize against other viruses. In this study, we have overcome this problem by creating a deletion in non-structural protein P150 that makes room for the insert. The resulting rubella hybrid stably expressed a model protein for over 10 passages, while replicating and expressing rubella proteins normally. The foreign protein, GFP, was as large as many important viral antigens, and the virus grew to sufficiently high titers for vaccine use. Further progress in expressing exogenous viral antigens in rubella may produce live viral vectors capable of immunizing against viruses for which attenuation is not currently feasible.