Protective immunity to Pseudomonas aeruginosa induced with a capsid-modified adenovirus expressing P. aeruginosa OprF

This study focuses on the development of a new clinical vaccine candidate (AdOprF.RGD.Epi8) against Pseudomonas aeruginosa using an E1(-) E3(-) adenovirus (Ad) vector expressing OprF (AdOprF.RGD.Epi8) and modifications of the Ad genome providing two capsid changes: (i) modification of the Ad hexon gene to incorporate an immune-dominant OprF epitope (Epi8) into loop 1 of the hexon, enabling repeat administration to boost the anti-OprF immune response, and (ii) modification of the fiber gene to incorporate an integrin-binding RGD sequence to enhance gene delivery to antigen-presenting cells. Western analysis confirmed that AdOprF.RGD.Epi8 expresses OprF, contains Epi8 in the hexon protein, and enhances gene transfer to dendritic cells compared to AdOprF, a comparable Ad vector expressing OprF with an unmodified capsid. Intramuscular immunization of C57BL/6 mice with AdOprF.RGD.Epi8 resulted in the generation of anti-OprF antibodies at comparable levels to those induced following immunization with AdOprF, but immunization with AdOprF.RGD.Epi8 was associated with increased CD4 and CD8 gamma interferon T-cell responses against OprF as well as increased survival against lethal pulmonary challenge with agar-encapsulated P. aeruginosa. Importantly, repeat administration of AdOprF.RGD.Epi8 resulted in boosting of the humoral anti-OprF response as well as increased protection, whereas no boosting could be achieved with repeat administration of AdOprF. This suggests that the capsid-modified AdOprF.RGD.Epi8 vector is a more effective immunogen compared to a comparable wild-type Ad capsid, making it a good candidate for an anti-P. aeruginosa vaccine.