Evaluation of DNA vaccination with recombinant adenoviruses using bioluminescence imaging of antigen expression: impact of application routes and delivery with dendritic cells.

ABSTRACT

Recombinant DNA vaccines are able to induce strong CD8+ T cell mediated immunity and have become increasingly attractive for the prevention and treatment of infectious diseases and cancer. Dendritic cells (DC), which critically control cellular immune responses, have been transduced with antigen ex vivo and used as 'nature's adjuvant' to enhance vaccine efficacy. The impact of the application route on the in vivo distribution of antigen and the stimulation of CD8+ T cells have been subjects of considerable debate. Here we report the construction of vectors expressing a fusion protein between EGFP, the H2-K(b)-binding peptide OVA(aa257-264) and green click beetle luciferase as a model antigen which allows for simultaneous quantitative assessment of antigen expression using fluorescence and bioluminescence imaging in correlation with CD8+ T cell stimulation in vivo. We applied this construct to evaluate DNA vaccination with recombinant adenoviral vectors, assess the impact of using cultured DC for vaccine delivery and investigate different application routes. Antigen expression was non-invasively followed in vivo by visualizing bioluminescence with an ultrasensitive CCD camera. CD8+ T cell stimulation was detected with H2-K(b)-OVA(aa257-264) tetramers. We found that intravenous injection of adenovirus-transduced DC stimulated the strongest OVA(aa257-264)-specific cytotoxic T-lymphocyte (CTL) responses although it delivered two orders of magnitude less antigen in vivo when compared to direct injection of recombinant adenovirus. We believe that our experimental approach has the potential to facilitate translational development of improved genetic immunization strategies targeting DC directly in vivo.