Compositions and methods for generating adeno-associated viral vectors with undetectable capsid gene contamination
In one aspect, the present invention provides an intron-modified cap expression cassette useful for generating adeno-associated virus (AAV) vector particles. In another aspect, the present invention provides a method of reducing the immune response in a mammalian subject undergoing treatment with an AAV vector.
1. An intron-modified capsid expression cassette useful for generating adeno-associated virus (AAV) vector particles, said expression cassette comprising a polynucleotide comprising:
(a) a nucleic acid molecule encoding an AAV capsid protein operably linked to a promoter and a polyadenylation signal, wherein the encoded AAV capsid protein packages AAV vectors in the presence of rep and adeno helper functions, and
(b) one or more heterologous excisable introns operably linked to the nucleic acid molecule;
wherein said nucleic acid molecule has a length of less than 5 kilobases, and wherein said nucleic acid molecule and said one or more heterologous excisable introns together have a length of more than 5 kilobases, and
wherein the total size of the one or more heterologous excisable introns together is at least 2 kb.
2. The expression cassette of claim 1 , wherein the nucleic acid molecule encodes an AAV capsid protein from an AAV serotype selected from the group consisting of AAV-1, AAV-2, AAV-3, AAV-4, AAV-5, AAV-6, AAV-7, AAV-8, AAV-9, AAV-10, AAV-11, AAV-12, and AAV-13, or a variant or hybrid protein thereof.
3. The expression cassette of claim 1 , wherein the nucleic acid molecule encodes an AAV capsid protein from an AAV serotype selected from the group consisting of AAV-2, AAV-8, and AAV-6, or a variant or hybrid protein thereof.
4. The expression cassette of claim 1 , wherein the promoter is a heterologous promoter.
5. The expression cassette of claim 1 , wherein the one or more heterologous excisable introns are positioned between the promoter and an open reading frame encoding said AAV capsid protein.
6. The expression cassette of claim 1 , wherein the one or more heterologous excisable introns comprise at least one splice donor and at least one splice acceptor site.
7. The expression cassette of claim 1 , further comprising an AAV intron adjacent to the 3′ end of the one of more heterologous excisable introns.
8. The expression cassette of claim 7 , wherein the one or more heterologous excisable introns comprise at least one splice donor site and the AAV intron comprises at least one splice acceptor site.
9. A vector comprising the expression cassette of claim 1 .
10. A cell comprising the expression cassette of claim 1 .
11. A method of generating an expression cassette for producing adeno-associated virus (AAV) vectors, comprising inserting one or more heterologous excisable introns into a polynucleotide comprising a nucleic acid molecule encoding an AAV capsid protein operably linked to a promoter and a polyadenylation signal, wherein said nucleic acid molecule has a length of less than 5 kilobases, and wherein said nucleic acid molecule and said one or more heterologous excisable introns together have a length of more than 5 kilobases, and
wherein the total size of the one or more heterologous excisable introns together is at least 2 kb.
12. The method of claim 11 , wherein the one or more heterologous excisable introns are positioned between the promoter and an open reading frame encoding said AAV capsid protein.