Recombinant adenovirus encoding the HA gene from swine H3N2 influenza virus partially protects mice from challenge with heterologous virus: A/HK/1/68 (H3N2).

Immunization with recombinant adenoviral vaccine that induces potent immunity has been applied to many infectious diseases. We report here developing a recombinant adenoviral vaccine encoding the HA gene from swine H3N2 influenza virus (SIV). Two replication-defective recombinant adenoviruses were generated: (1) rAd-HA: recombinant adenovirus encoding the HA gene from swine H3N2 influenza virus, and (2) rAd-vector: a control recombinant adenovirus containing adenovirus and transfer plasmids without a foreign HA gene. Mice given rAd-HA developed high titers of neutralizing and hemagglutination inhibition antibodies to SIV in comparison to mice inoculated with rAd-vector or PBS as early as 2 weeks after immunization, and these antibodies were substantially increased in the mice given rAd-HA within the next 3 weeks following the first dose. However, these antibodies were not able to neutralize the virus, A/HK/68 (H3N2), used for challenge. Nonetheless mice immunized with one or two doses of rAd-HA were protected from lethal challenge with heterologous virus, A/HK/1/68 (H3N2). A statistically significant ( P < 0.03) difference between survival rates of rAd-HA mice vs. rAd-vector or PBS mice was observed.