Recombinant Live Attenuated Influenza Vaccine Viruses Carrying Conserved T Cell Epitopes of Human Adenoviruses Induce Functional Cytotoxic T Cell Responses and Protect Mice against both Infections

Abstract

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.

A Strategy to Elicit M2e-Specific Antibodies Using a Recombinant H7N9 Live Attenuated Influenza Vaccine Expressing Multiple M2e Tandem Repeats

“…Here, we explored the possibility of licensed live attenuated influenza vaccine backbone as a viral vector to deliver additional conserved M2e epitopes of influenza A viruses to the target cells to enhance the breadth of protection afforded by classical LAIV viruses. It is well known that LAIVs induce cross-reactive immunity with a potential to protect against drifted influenza viruses in a variety of animal models as well as in human trials [ 15 , 42 , 43 , 44 ], and numerous studies have proven that LAIV is a promising viral vector for designing vaccines against other infectious pathogens [ 45 , 46 , 47 , 48 ]. Our recent study demonstrated that seasonal H1N1 and H3N2 LAIVs expressing four M2e tandem repeats within the chimeric HAs can elicit M2e-specific antibody and, to a lesser extent, T-cell responses which enhanced cross-protective potential of the vaccines [ 14 ].…”

Universal Live-Attenuated Influenza Vaccine Candidates Expressing Multiple M2e Epitopes Protect Ferrets against a High-Dose Heterologous Virus Challenge

“…Here, the transgene is not present in the viral particle, but should be translated within the infected cell, because the NS1 protein is abundantly expressed in the early stages of infection [ 29 ]. Such modification of LAIV genome has been previously shown as a promising strategy for the induction of robust cytotoxic T-cell responses to the inserted immunodominant CD8 T-cell epitope of a foreign pathogen [ 30 , 31 , 32 ]. In vitro studies confirmed that regardless of how the 4M2e cassette was inserted into the LAIV genome, M2e proteins were expressed at significantly higher levels when mammalian cells were infected with the LAIV+4M2e recombinant candidates than with the classic LAIV strain, demonstrating the LAIV’s ability to properly deliver additional M2e antigens to target cells.…”

Safety, Immunogenicity, and Protective Efficacy of a Chimeric A/B Live Attenuated Influenza Vaccine in a Mouse Model

“…To assess T-cell responses to influenza A virus, an intracellular cytokine staining (ICS) assay was performed as previously described [ 29 ]. Briefly, splenocytes were isolated 5 days after the influenza A virus challenge according to the design of the experiment described in Section 2.5 .…”