Use of Cre/loxP recombination to swap cell binding motifs on the adenoviral capsid protein IX

We used Cre/loxP recombination to swap targeting ligands present on the adenoviral capsid protein IX (pIX). A loxP-flanked sequence encoding poly-lysine (pK—binds heparan sulfate proteoglycans) was engineered onto the 3′-terminus of pIX, and the resulting fusion protein allowed for routine virus propagation. Growth of this virus on Cre-expressing cells removed the pK coding sequence, generating virus that could only infect through alternative ligands, such as a tyrosine kinase receptor A (TrkA)-binding motif engineered into the capsid fibre protein for enhanced infection of neuronal cells. We used a similar approach to swap the pK motif on pIX for a sequence encoding a single-domain antibody directed towards CD66c for targeted infection of cancer cells; Cre-mediated removal of the pK-coding sequence simultaneously placed the single-domain antibody coding sequence in frame with pIX. Thus, we have developed a simple method to propagate virus lacking native viral tropism but containing cell-specific binding ligands.

► We describe a method to grow virus lacking native tropism but containing novel cell-binding ligands. ► Cre/loxP recombination was used to modify the adenovirus genome. ► A targeting ligand present on capsid protein IX was removed or replaced using recombination. ► Cre-loxP was also used to “swap” the identity of the targeting ligand present on pIX.