Reciprocal mutations of lung-tropic AAV capsids lead to improved transduction properties

Ashley L Cooney; Christian M Brommel; Soumba Traore; Gregory A Newby; David R Liu; Paul B McCray Jr; Patrick L Sinn

doi:10.3389/fgeed.2023.1271813

Reciprocal mutations of lung-tropic AAV capsids lead to improved transduction properties

Front Genome Ed. 2023 Nov 22:5:1271813. doi: 10.3389/fgeed.2023.1271813. eCollection 2023.

Authors

Ashley L Cooney^{1

2

3}, Christian M Brommel^{1

2

3}, Soumba Traore^{1

2

3}, Gregory A Newby^{4

5

6}, David R Liu^{4

5

6}, Paul B McCray Jr^{1

2

3}, Patrick L Sinn^{1

2

3}

Affiliations

¹ University of Iowa, Stead Family Department of Pediatrics, Iowa City, IA, United States.
² Pappajohn Biomedical Institute, Iowa City, IA, United States.
³ Center for Cystic Fibrosis Gene Therapy, University of Iowa, Iowa City, IA, United States.
⁴ Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of Harvard and MIT, Cambridge, MA, United States.
⁵ Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, United States.
⁶ Howard Hughes Medical Institute, Harvard University, Cambridge, MA, United States.

Abstract

Considerable effort has been devoted to developing adeno-associated virus (AAV)-based vectors for gene therapy in cystic fibrosis (CF). As a result of directed evolution and capsid shuffling technology, AAV capsids are available with widespread tropism for airway epithelial cells. For example, AAV2.5T and AAV6.2 are two evolved capsids with improved airway epithelial cell transduction properties over their parental serotypes. However, limited research has been focused on identifying their specific cellular tropism. Restoring cystic fibrosis transmembrane conductance regulator (CFTR) expression in surface columnar epithelial cells is necessary for the correction of the CF airway phenotype. Basal cells are a progenitor population of the conducting airways responsible for replenishing surface epithelial cells (including secretory cells and ionocytes), making correction of this cell population vital for a long-lived gene therapy strategy. In this study, we investigate the tropism of AAV capsids for three cell types in primary cultures of well-differentiated human airway epithelial (HAE) cells and primary human airway basal cells. We observed that AAV2.5T transduced surface epithelial cells better than AAV6.2, while AAV6.2 transduced airway basal cells better than AAV2.5T. We also investigated a recently developed capsid, AAV6.2FF, which has two surface tyrosines converted to phenylalanines. Next, we incorporated reciprocal mutations to create AAV capsids with further improved surface and basal cell transduction characteristics. Lastly, we successfully employed a split-intein approach using AAV to deliver an adenine base editor (ABE) to repair the CFTR ^R553X mutation. Our results suggest that rational incorporation of AAV capsid mutations improves AAV transduction of the airway surface and progenitor cells and may ultimately lead to improved pulmonary function in people with CF.

Keywords: adeno-associated virus capsid; airway epithelia; base editing; cystic fibrosis; gene therapy.

Abstract

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