Insertion of Foreign Genes in Rubella Virus and their Stable Expression in a Live, Attenuated Viral Vaccine
Rubella virus (RUB) is the only member of the Rubivirus genus of the family Togaviridae. The RUB genomic RNA is a single-stranded, 9762-nt, positive-sense RNA that contains two long open reading frames (ORFs): a 5'-proximal ORF which encodes nonstructural proteins (NSP) that function primarily in viral RNA replication, including the RdRp, and a 3'-proximal ORF which encodes the virion structural proteins (SP), the capsid protein (C), and two envelope glycoproteins, E1 and E2. The genomic RNA serves as a template for synthesis of a complementary minus-strand RNA which is the template for synthesis of both the genomic RNA and the subgenomic (SG) RNA, from which the structural proteins are translated.
All earlier efforts at expressing foreign genes in rubella virus failed due to stability of the insert. The inventors have found a way to insert foreign genes into rubella virus such that the foreign genes can be expressed stably over many passages of the virus. More specifically, based on an earlier observation that rubella virus can tolerate a small deletion in the nonstructural genes and still replicate normally, the inventors’ have used this deletion to make room for insertion of a foreign gene. Thus, the inventors have conceptualized and reduced to practice a new way to use the already-approved rubella vaccine as a viral vector to express the additional protein antigens of a second (or multiple other) viruses. This is highly advantageous because it allows for production of a live virus vaccine when attenuation is not possible for highly virulent viruses such as HIV.
Furthermore, another advantage of this vaccine is that virus titers in cell culture reach one thousand (1000) human doses per milliliter (ml) of culture supernatant. This is highly desirable for production of multiple millions of doses for the developing world. In the developed world, this vaccine could be substituted for the current vaccine at almost no cost and used to immunize against rubella plus the inserted antigen(s). Without vaccination, the average age of becoming seropositive for rubella is approximately nine (9) years old. This new vaccine could be given to one to two year olds with a booster at nine years old. Additionally, this vaccine is already approved, so the safe and immunogenic doses are already known.
Potential Commercial Applications:
- Vaccines for the prevention of rubella and other indications
- Use of rubella vector for expression of foreign genes
- Novel vaccine candidate
- Rapid production time
Spadaccini A, Vimik K, Ni Y, Prutzman K, Berkower I. Stable expression of a foreign protein by a replication-competent rubella viral vector. Vaccine. 2010 Feb 3;28(5):1181-1187. PubMed: 19945412
Bill Ronnenberg, JD-MIP, MS
FDA Technology Transfer Program
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OTT Reference No: E-156-2008/0
Updated: August 7, 2015