Human adenoviruses (AdVs) are one of the most common causes of acute respiratory
viral infections worldwide. Multiple AdV serotypes with low cross-reactivity circulate in the human population, making the development of an effective
vaccine very challenging. In the current study, we designed a cross-reactive AdV
vaccine based on the
T-cell epitopes conserved among various AdV serotypes, which were inserted into the genome of a licensed cold-adapted live attenuated
influenza vaccine (LAIV) backbone. We rescued two recombinant LAIV-AdV
vaccines by inserting the selected AdV
T-cell epitopes into the open reading frame of full-length NA and truncated the NS1
proteins of the H7N9 LAIV virus. We then tested the
bivalent vaccines for their efficacy against
influenza and human AdV5 in a mouse model. The
vaccine viruses were attenuated in C57BL/6J mice and induced a strong
influenza-specific antibody and cell-mediated immunity, fully protecting the mice against virulent influenza virus
infection. The CD8 T-cell responses induced by both LAIV-AdV candidates were functional and efficiently killed the target cells loaded either with
influenza NP366 or AdV DBP418
peptides. In addition, high levels of recall memory T cells targeted to an immunodominant H2b-restricted CD8
T-cell epitope were detected in the immunized mice after the AdV5 challenge, and the magnitude of these responses correlated with the level of protection against pulmonary pathology caused by the AdV5
infection. Our findings suggest that the developed
recombinant vaccines can be used for combined protection against
influenza and human adenoviruses and warrant further evaluation on humanized animal models and subsequent human trials.