Hydropericardium-hepatitis syndrome (HHS), a recently emerged disease of chickens, is caused by some strains of fowl adenovirus serotype 4 (FAdV-4). In this study, a Canadian FAdV-4 isolate, designated as FAdV-4 ON1, was evaluated for pathogenicity after oral and intramuscular (im) infection of specific pathogen free (SPF) chickens. Pathogenicity was evaluated by observation of clinical signs and gross and histological lesions. The highest viral DNA copy numbers, irrespective of the inoculation route, were detected in the cecal tonsils. Virus titers in cloacal swabs collected over the entire study period were compared between the orally and im inoculated chickens, and the difference in titers between the two groups was significant (P<0.001), the oral group had a higher rank. The antibody response of infected chickens tested by an adenovirus-specific ELISA showed a statistically significant (P<0.001) difference between the orally and im inoculated chickens. The im inoculated chickens had higher values than birds inoculated orally (P<0.001). Serum samples from both groups collected at 14 days post-infection completely neutralized FAdV-4 ON1. In addition, the effects of FAdV-4 ON1 infection on transcription of a number of avian cytokines were studied in vivo. The expression of interferon (IFN)-γ and interleukin (IL)-10 in the liver was induced at early times after infection. This FAdV-4 ON1 potentially could be used as a live vaccine against HHS and developed as vaccine vector. The GenBank/EMBL/DDBJ accession number for the FAdV-4 ON1 sequence is GU188428.

The fowl adenovirus type 8 (FAdV-8) genome was sequenced and found to be 45063 nucleotides in length, the longest adenovirus (AdV) genome for which the complete nucleotide sequence has been determined so far. No regions homologous to early regions 1, 3 and 4 (E1, E3 and E4) of mastadenoviruses were recognized. Gene homologues for early region 2 (E2) proteins, intermediate protein IVa2 and late proteins were found by their similarities to protein sequences from other AdVs. However, sequences homologous to intermediate protein IX and late protein V could not be identified. Sequences for virus-associated RNA could also not be recognized. Two regions of repeated sequences were found on the FAdV-8 genome. The shorter repeat region contained five identical and contiguous direct repeats that were each 33 bp long, while the longer repeat region was made of 13 identical and contiguous, 135 bp long repeated subunits.

Five recombinant porcine adenoviruses of serotype 5 (PAdV-5) carrying the full-length or the 5′ 2·2 kb half of the transmissible gastroenteritis virus (TGEV) spike (S) gene were generated by homologous recombination in E. coli strain BJ5183 cells and subsequent transfection of swine testicle cells. The foreign genes were inserted into the E3 region of PAdV-5. One recombinant virus had no deletion in the E3 region, whereas a 1·2 kb fragment was removed from the E3 region in the remainder of the recombinant viruses. One stable construct with a 4·4 kb insertion had a genome size of 109·6% of the wild-type genome, the largest reported for any recombinant adenovirus. Only those viruses that carried the S gene in the left to right orientation expressed the S gene. Three recombinant viruses were tested by oral immunization of pigs and both antibody response and virus shedding were monitored. None of the pigs showed clinical signs and the virus was recovered from rectal swabs until 6–7 days post-infection. Viruses expressing the S gene induced TGEV- and PAdV-5-specific virus-neutralizing antibodies. Moreover, TGEV-specific secretory IgA was detected in the small intestine and in the lungs of the immunized animals.