Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2006
Publication Date: 11/1/2006
Citation: Wesley, R.D., Lager, K.M. 2006. Overcoming maternal antibody interference by vaccination with human adenovirus 5 recombinant viruses expressing the hemagglutinin and the nucleoprotein of swine influenza virus. Veterinary Microbiology. 118:67-75. 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 suckling pigs that have natural field exposure levels of maternally-derived, anti-SIV antibodies. These pigs with maternal antibodies would not be protected from pneumonia with currently available commercial vaccines. The immunization strategy that was tested consisted of priming alone with vectored recombinant vaccine or priming followed by booster immunization with commercial vaccine. Both vaccination strategies were effective as demonstrated by abrogation of clinical signs, by clearance of challenge virus from pulmonary fluids, by markedly reduced virus shedding in nasal secretions, and by the absence of moderate or severe lung lesions. These improved second generation SIV vaccines will benefit swine producers and veterinarians.
Technical Abstract: Sows and gilts lack immunity to human adenovirus 5 (Ad-5) vectored vaccines so immunogens of swine pathogens can be expressed with these vaccines in order to immunize suckling piglets that have interfering, maternally-derived antibodies. In this study 7 day old piglets, that had suckled H3N2 infected gilts, were sham-inoculated with a non-expressing Ad-5 vector or given a primary vaccination with replication-defective Ad-5 viruses expressed the H3 hemagglutinin and the nucleoprotein of swine influenza virus (SIV) subtype H3N2. The hemagglutination inhibition (HI) titer of the sham-inoculated group (n=12) showed continued antibody decay whereas piglets vaccinated with Ad-5 SIV (n=23) developed an active immune response by the second week post vaccination. At 4 weeks-of-age when the HI titer of the sham-inoculated group had decayed to 45, the sham-inoculated group and half of the Ad-5 SIV vaccinated pigs were boosted with a commercial inactivated SIV vaccine. The boosted pigs that had been primed in the presence of maternal interfering antibodies had a strong anamnestic response while sham-inoculated pigs did not respond to the commercial vaccine. Two weeks after the booster vaccination the pigs were challenged with a non-homologous H3N2 virulent SIV. The efficacy of the vaccination protocol was demonstrated by abrogation of clinical signs, by clearance of challenge virus from pulmonary lavage fluids, by markedly reduced virus shedding in nasal secretions, and by the absence of moderate or severe SIV-induced lung lesions. These recombinant Ad-5 SIV vaccines are useful for priming the immune system to override the effects of maternally-derived antibodies which interfere with conventional SIV vaccines.