Derivation of a triple mosaic adenovirus based on modification of the minor capsid protein IX

Adenoviral capsid protein IX (pIX) has been shown to be a potential locale to insert targeting, imaging-related and therapeutic modalities by genetic modification. Recent evidences suggested that capsid protein mosaicism could be a promising strategy for improving the utility of Ad vector. In this study, we explored a method to genetically generate triple pIX mosaic Ad serotype 5 (Ad5) displaying three types of pIX on a single virion. pIXs were modified at their carboxy termini with a Flag sequence, a hexahistidine sequence (His₆) or a monomeric red fluorescent protein (mRFP1), respectively. Western blotting analysis and fluorescence microscopy of the purified recombinant viruses indicated that all three modified pIXs were incorporated into the viral particles. Immuno-gold electron microscopy (EM) further confirmed that three types of pIX indeed co-existed on an individual virion. These results firstly validated a triple mosaic capsid configuration on pIX, and demonstrated the possibility of further radical design.