Metabolically activated recombinant viral vectors and methods for their preparation and use
Recombinant viral vectors, especially parvovirus vectors such as adeno-associated virus (AAV) vectors, capable of enhanced expression of heterologous sequences, and methods for their construction and use, are provided. The vectors have a structure, or are capable of rapidly adopting a structure, which involves intrastrand base pairing of at least one region in a heterologous sequence.
1. A method for preparing a recombinant adeno-associated virus (rAAV), the method comprising:
1) incubating a host cell under conditions that allow AAV replication and encapsidation, wherein said host cell comprises:
(a) a rAAV vector comprising a heterologous nucleotide sequence and one or more AAV inverted terminal repeat (ITR) sequences flanking said heterologous sequence, wherein the vector is less than about 2.5 kb, and
(b) AAV rep function, AAV cap function, and helper virus function for AAV; and
2) purifying rAAV particles produced from the host cell, wherein the rAAV particles comprise a rAAV genome which forms intrastrand base pairs along its length, such that expression of a coding region of the heterologous sequence is enhanced relative to a rAAV vector that lacks sufficient intrastrand base pairing to enhance said expression.
2. The method of claim 1 wherein rep and cap functions are provided by a rep-cap cassette that is stably integrated in the host cell genome.
3. The method of claim 1 wherein rep and cap functions are provided by a plasmid.
4. The method of claim 1 wherein the rAAV vector is provided in a plasmid.
5. The method of claim 1 , wherein the rAAV vector is stably integrated into the host cell genome.
6. The method of claim 1 wherein helper functions are provided by adenovirus infection.
7. A population of rAAV particles produced according to the method of claim 1 .
8. A population of rAAV vectors produced according to the method of claim 1 .
9. The method of claim 1 , wherein the rAAV particles are purified to deplete helper virus.