Exploration of New Sites in Adenovirus Hexon for Foreign Peptides Insertion

Adenoviral vectors are now being explored as vaccine carriers to prevent infectious diseases in humans and animals. There are two strategies aimed at the expression of a vaccine antigen by adenoviral vectors. The first includes an insertion of the foreign gene expression cassette into the E1 region. The second strategy is antigen incorporation into the viral capsid proteins. To extend this methodology, we have searched for new sites at the human adenovirus serotype 5 major capsid protein hexon for a vaccine antigen insertion. To this end, we utilized sites in the hexon hypervariable region (HVR) 7, 8 and 9 to display a 15-mer peptide containing the main neutralizing epitope of porcine reproductive and respiratory syndrome virus. However, we could not rescue the viruses with the insertions of the peptide into HVR 8 and 9, consistent with the viruses being unable to tolerate insertions at these sites. In contrast, the virus with the insertion of the peptide in HVR 7 was viable - growing well in cell culture and the inserted peptide was exposed on the virion surface.