Evaluation of a recombinant human adenovirus-5 vaccine administered via needle-free device and intramuscular injection for vaccination of pigs against swine influenza virus

Abstract

To evaluate the safety and efficacy of a human adenovirus-5 vaccine for protecting weaned pigs against swine influenza virus subtype H3N2 infection when administered via 2 injection methods. 76 pigs. 6 groups of weaned pigs received a 10-fold serial dilution of recombinant adenovirus expressing H3 hemagglutinin and a constant amount of recombinant adenovirus expressing nucleoprotein, either via a needle-free injection device or by traditional IM injection. In each group of 10 pigs, 1 served as a nonvaccinated contact pig to monitor whether there was spread of vaccinial virus from pig to pig. Vaccinated pigs and nonvaccinated controls were challenged or sham-inoculated 5 weeks later. After challenge, pigs were observed for clinical signs and nasal secretions were tested for virus. On day 5 after challenge, pigs were euthanatized; lungs were examined for gross lesions, and bronchoalveolar lavage specimens were tested for virus replication. A hemagglutination inhibition (HI) antibody response was elicited in a dose-dependent manner. Traditional IM administered vaccination induced consistently higher HI antibody responses than vaccination via needle-free injection, but the differences were not significant. Likewise, traditional IM administration was superior at reducing nasal virus shedding except at the highest dose, at which both methods blocked virus replication. The severity of lung lesions was reduced in a dose-dependent manner by both vaccination methods. Sentinel pigs did not seroconvert. The human adenovirus-5 vaccine at high doses prevented nasal virus shedding after challenge exposure with both methods of administration. The replication-defective vaccine virus was not transmitted to sentinel pigs.