Desmoglein 2 (DSG2)-knockout human respiratory epithelial cell model to study species B adenovirus receptor usage

With an increasing number of human adenoviruses identified, the selection of potential therapeutic vectors broadens. For safety reasons, achieving cell-specific gene delivery is crucial to minimize off-target effects. Therefore, it is essential to gain a systematic understanding of adenovirus receptor-usage. Our aim is to establish a human-originated in vitro model for comparative analysis of human adenoviruses receptor usage. Based on our previous work of human CD46 and coxsackievirus and adenovirus receptor (CAR) knockout cell lines, we generated desmoglein 2 (DSG2) knockout cell lines using genome-engineering technology based on Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9 (CRISPR/Cas9). All together, we established a panel of cell lines that carry a single, double, or triple knockout of the three major human adenovirus receptors: CAR, CD46 and DSG2. Notably, cell proliferation speed was affected by the CAR-knockout, but not the DSG2-or CD46-knockouts. In addition, the spheroid formation ability was sharply reduced in CAR- or DSG2-knockout cells, but not the CD46-knockout cells. With this receptor-knockout model, we confirmed the receptor usage of nine species B adenoviruses. Furthermore, adenovirus vectors containing a previously identified DSG2-binding affinity-enhanced mutation showed DSG2-dependent cell entry within this cell model, which indicates that they are de-targeted from CD46 - the ubiquitously expressed receptor on all nucleated cells. Collectively, our findings show that the adenovirus major receptor knockout cell lines can serve as an in vitro model to help select adenovirus types suitable for individual applications and to better understand adenovirus infection biology.