Submitted to: Vaccine
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/13/2004
Publication Date: 9/3/2004
Citation: Wesley, R.D., Lager, K.M., Tang, M. 2004. Protection of weaned pigs by vaccination with human adenovirus 5 recombinant viruses expressing the hemagglutinin and the nucleoprotein of H3N2 swine influenza virus. Vaccine. 22:3427-3434. Interpretive Summary: Pathogens of the porcine respiratory disease complex, including viral pathogens like swine influenza virus (SIV), cause pneumonia in pigs which is the industry's most costly disease. This research focuses on improved vectored vaccines for protection of weaned pigs against SIV. Groups of pigs were vaccinated intramuscularly with human adenovirus-5 vaccines expressing either the SIV hemagglutinin or the SIV nucleoprotein. A third group of pigs was immunized with both recombinant vaccines in a mixture. Weaned pigs vaccinated with both recombinants simultaneously were completely protected from challenge infection with virulent influenza virus. Improved second generation SIV vaccines will benefit swine producers and veterinarians.
Technical Abstract: Swine influenza virus (SIV), subtype H3N2, is a new reassortant virus that emerged recently in North American swine causing severe respiratory and reproductive disease. In this study, 2 replication-defective adenovirus recombinants were developed as potential vaccines against H3N2 influenza viruses. Three groups of pigs (10 pigs/group) were vaccinated intramuscularly with the recombinants; one group was vaccinated with the recombinant adenovirus expressing the influenza virus H3 hemagglutinin (HA) protein, one group was vaccinated with the recombinant adenovirus expressing the nucleoprotein (NP), and one group was vaccinated with both recombinants in a mixture. Two additional control groups (10 pigs/group) were included in the animal trial. One control group was challenged with a virulent H3N2 field strain and one control group remained unchallenged. The results showed that pigs in the groups given the recombinant adenovirus expressing the HA protein developed high levels of virus-specific hemagglutination-inhibition (HI) antibody by 4 weeks post vaccination. Pigs in the group vaccinated with both recombinant viruses in a mixture were completely protected. Complete protection was shown by the lack of nasal shedding of virus following challenge and by the lack of lung lesions at one week following the challenge infection. Thus, replication-incompetent adenovirus vaccines given simultaneously to pigs are safe, efficacious for SIV and have the additional advantage over commercial vaccines that suckling piglets have no pre-existing maternally-derived antibody to block early life vaccination.