Vaccine Design and Immunization Schedule.
A schematic representation of the Ad4 shuttle plasmid is shown (A). The shuttle plasmid containing the CMV-HA-PolyA expression cassette is shown (B). The two Adenoviral types and the location of the HA expression transgenes used as vaccine vectors are shown (C). The Ad4 vaccine had an E1 deletion whereas the Ad5 vaccine had E1 and E3 deletions. The HA transgene expression cassette was recombined in place of the E1 genes in both vaccine vectors. Mice were immunized with the vaccine vectors using three different doses (D). The mice were primed with the Ad4 vaccine vector and boosted 4 weeks later with the Ad5 vaccine vector. Test bleeds were taken 2 weeks post-boosting and the mice were challenged with lethal doses of influenza 4 weeks post-boosting. The mice were monitored for weight loss, disease and death. Mice that lost ≥25% of the day 0 body weight were humanely euthanized.