The optimization of HA DNA vaccines against equine H3N8 influenza

Objective To develop a higly immunogenic DNA vaccine against equine influenza H3N8.Methods According to the amino acids sequence of HA antigen from equine influenza A strain A/Equine/Xinjiang/3/08 (H3N8),a codon optimized H3HA genes was chemically synthesized.It was then subcloned into vector pJW4303 to express the wild type HA insert (H3HA /XJ3-08-wt).The codon optimized HA gene was further modified to either replace the original HA leader sequence with a human tissue plasminogen activator (tPA) leader (H3HA /XJ3-08-tPA) or truncate the HA coding sequence to express only the extracellular portion of the HA protein (H3HA/XJ3-08-dTM).The expression of the above three HA DNA vaccines was verified in 293T cells by Western blot analysis.New Zealand White rabbits were vaccinated with three versions of HA DNA vaccines or vector individually by electroporation.H3HA specific antibody responses in rabbit sera were analyzed by ELISA and the protective antibody activities were measured by HI against equine H3N8 virus.Results The H3HA DNA plasmids could express HA antigen successfully in 293T cells in vitro,and induced high level protective anti-H3HA antibody.Among three H3HA DNA vaccines,HA DNA vaccine design with a tPA leader showed the best immunogenicity.Conclusion Optimal HA DNA vaccines against H3N8 equine influenza have been successfully constructed,affording a new way to develop equine H3N8 vaccine in the future.