Cloning and Characterization of a Bovine Adeno-Associated Virus

Abstract

To better understand the relationship between primate adeno-associated viruses (AAVs) and those of other mammals, we have cloned and sequenced the genome of an AAV found as a contaminant in two isolates of bovine adenovirus that was reported to be serologically distinct from primate AAVs. The bovine AAV (BAAV) genome has 4,693 bp, and its organization is similar to that of other AAV isolates. The left-hand open reading frame (ORF) and both inverted terminal repeats (ITRs) have the highest homology with the rep ORF and ITRs of AAV serotype 5 (AAV-5) (89 and 96%, respectively). However, the right-hand ORF was only 55% identical to the AAV-5 capsid ORF; it had the highest homology with the capsid ORF of AAV-4 (76%). By comparing the BAAV cap sequence with a model of an AAV-4 capsid, we mapped the regions of BAAV VP1 that are divergent from AAV-4. These regions are located on the outside of the capsid and are partially located in exposed loops. BAAV was not neutralized by antisera raised against recombinant AAV-2, AAV-4, or AAV-5, and it demonstrated a unique cell tropism profile in four human cancer cell lines, suggesting that BAAV might have transduction activity distinct from that of other isolates. A murine model of salivary gland gene transfer was used to evaluate the in vivo performance of recombinant BAAV. Recombinant BAAV-mediated gene transfer was 11 times more efficient than that with AAV-2. Overall, these data suggest that vectors based on BAAV could be useful for gene transfer applications.Adeno-associated virus (AAV) was first described as a contaminant of tissue culture-grown simian virus 15 (a simian adenovirus) that is dependent on adenovirus for efficient replication (reviewed in reference 17). This description resulted in its name as well as its classification in the genus Dependovirus. AAV is a member of the Parvoviridae, a virus family characterized by a single-stranded linear DNA genome and a capsid with icosahedral symmetry measuring about 20 nm in diameter. AAV serotype 2 (AAV-2) is the best-characterized isolate and is discussed here as an AAV prototype.The AAV-2 genome consists of a linear single strand of DNA that is 4,780 nucleotides long. Both polarities of DNA are encapsulated by AAV-2 with equal efficiency. The AAV-2 genome contains two open reading frames (ORFs). The rep ORF encodes the nonstructural proteins essential for viral DNA replication, packaging, and AAV targeted integration. The cap ORF encodes three related proteins that assemble to form the virus capsid, while the rep ORF is transcribed from promoters at map units P5 and P19. The rep transcripts contain an intron close to the 3Ј end of the rep ORF that can be alternatively spliced. Thus, the rep ORF is expressed as four partially overlapping proteins, which are referred to according to their molecular weights: Rep78, Rep68, Rep52, and Rep40 (18,20,26). The cap ORF is expressed from a single promoter at P40. By alternative splicing and utilization of an alternative ACG start codon, the cap ORF produces three proteins (VP1 ...

A shortened adeno-associated virus expression cassette for CFTR gene transfer to cystic fibrosis airway epithelia

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Coordinated control of connexin 26 and connexin 30 at the regulatory and functional level in the inner ear

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Structural Insights into Adeno-Associated Virus Serotype 5

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