Functional Cystic Fibrosis Transmembrane Conductance Regulator Expression in Cystic Fibrosis Airway Epithelial Cells by AAV6.2-Mediated Segmental Trans -Splicing

Abstract

Cystic fibrosis is characterized by deficiency of the cystic fibrosis transmembrane conductance regulator (CFTR), a Cl⁻ transporter. The packaging constraints of adeno-associated viral (AAV) vectors preclude delivery of both an active promoter and CFTR cDNA to target cells. We hypothesized that segmental trans-splicing, in which two AAV vectors deliver the 5′ and 3′ halves of the CFTR cDNA, could mediate splicing of two pre-mRNAs into a full-length, functional CFTR mRNA. Using a segmental trans-splicing 5′ donor–3′ acceptor pair that split the CFTR cDNA between exons 14a and 14b, cotransfection of donor and acceptor plasmids into CFTR⁻ cells resulted in full-length CFTR message and protein. Microinjection of plasmids into CFTR⁻ cells produced cAMP-activated Cl⁻ conductance. Vectors created with an engineered human serotype, AAV6.2, were used to deliver CFTR donor and acceptor constructs, resulting in full-length CFTR mRNA and protein as well as cAMP-activated Cl⁻ conductance in CFTR⁻ cells, including human CF airway epithelial IB3-1 cells. Thus, segmental trans-splicing can be used with AAV vectors to mediate expression of CFTR, a strategy potentially applicable to individuals with CF.