Vaccination of pigs with a recombinant porcine adenovirus expressing the gD gene from pseudorabies virus

Five week old, commercially available large white pigs were vaccinated with either a single dose or two doses of a recombinant porcine adenovirus expr essing the glycoprotein D gene from pseudorabies virus (PRV). Pigs were mon itored for the development of serum neutralizing antibodies to PRV and chal lenged 3 weeks after final vaccination. Prior to challenge, pigs given 2 do ses of the vaccine demonstrated boosted levels of antibody compared with th ose given a single dose, and all surviving pigs had increased neutralizatio n titres over pre-challenge levels. Following challenge, pigs were monitore d for clinical signs of disease, with blood and nasal swabs collected for v irus isolation. All control animals became sick with elevated temperatures for 6 days post challenge, whereas; vaccinated animals displayed an increas e in body temperature for only 2-3 days. Control pigs and those given a sin gle dose all lost condition. but the group given 2 doses remained healthy. At postmortem, gross lesions of pneumonia only occurred in control animals and those given a single dose of vaccine. Histology carried out on the brai ns of all animals demonstrated a difference in severity of infection and fr equency of immunohistochemical antigen detection between test animals. with control and single dose groups being most severely affected and pigs given 2 doses the least. Virus isolation studies demonstrated that no viraemia c ould be detected, but virus was found in nasal swabs from some animals in b oth groups of vaccinates following challenge. (C) 2001 Elsevier Science Ltd . All rights reserved.