The protective effects of a d-tetra-peptide hydrogel adjuvant vaccine against H7N9 influenza virus in mice

Repeated waves of influenza virus H7N9 epidemics after 2013 have caused severe influenza in humans, with mortality reaching approximately 40%–50%. To prevent possible pandemics, the development of highly effective vaccines against influenza virus H7N9 is highly desired. In the present study, by taking advantage of the d-tetra-peptide adjuvant (G^DF^DF^DY), we reported a simple method to prepare H7N9 vaccines. Naproxen (Npx), with good anti inflammatory and broad anti-viral effects, was employed as an N-terminal capping group to construct a hydrogel precursor, Npx-G^DF^DF^DY. The hydrogel adjuvant was prepared using a routine heating cooling protocol and the final vaccine was ready after mixing with the split A/Zhejiang/DTID-ZJU01/2013 (H7N9) antigen by vortexing. Compared with the traditional Al(OH)₃ adjuvant vaccine and the split vaccine, our hydrogel adjuvant vaccine showed the best preventive effects against H7N9 infection. A mechanistic study illustrated that higher antibody responses and variations in cytokine expression might account for its increased protective effects. Our strategy demonstrated the advantages of a peptide hydrogel adjuvant in the application of vaccines against H7N9 and demonstrated its potential application in vaccines against emerging threats from other viruses.