A sixth species of ovine adenovirus isolated from lambs in New Zealand

Serologic and hexon phylogenetic analysis of ruminant adenoviruses

The objectives of this study were to determine the antigenic relationship among ruminant adenoviruses and determine their phylogenetic relationship based on the deduced hexon gene amino acid sequence. Results of reciprocal cross-neutralization tests demonstrated antigenic relationships in either one or both directions among bovine adenovirus type 6 (BAdV-6), BAdV-7, ovine adenovirus type 7 (OAdV-7), caprine adenovirus type 1 (GAdV-1), and deer adenovirus (Odocoileus adenovirus 1, OdAdV-1). No antigenic cross-reactivity was observed among BAdV-1 through -5, and -8 and the other putative ruminant adenoviruses. Two PCR primer sets, one for mastadenovirus and atadenovirus that amplified an approximately 2,700-bp region in the hexon genes were used for comparative studies. Phylogenetic analysis of the deduced hexon amino acid sequences clustered the ruminant adenoviruses on the Mastadenovirus and Atadenovirus genus branches of the Adenoviridae tree. The recent classification of BAdV-6, and -7 as members of the genus Atadenovirus was supported by phylogenetic distance matrix analysis of their deduced hexon amino acid sequences. Further, we propose that BAdV-6 and -7 be recognized as members of new Atadenovirus species, Bovine adenovirus E and Bovine adenovirus F, respectively. Phylogenetic analysis of OdAdV-1 places this virus in the genus Atadenovirus with a proposed new species Odocoileus adenovirus A. OAdV-6 and GAdV-2 are proposed as members of new Mastadenovirus species Ovine adenovirus C and Goat adenovirus A, respectively.

Close phylogenetic relationship between egg drop syndrome virus, bovine adenovirus serotype 7, and ovine adenovirus strain 287

A cloned egg drop syndrome (EDS) virus genomic DNA fragment containing the protease gene has been identified and the complete nucleotide sequence of the protease and partial nucleotide sequence of the hexon genes has been determined. Phylogenetic analysis of the protease gene has revealed EDS virus to be genetically more closely related to bovine adenovirus type 7 (BAV-7) and ovine adenovirus isolate 287 (OAV287) than either of these two viruses are to other members of the genus Mastadenovirus or EDS virus is to an other member of the Aviadenovirus genus. The three viruses share further similarities in that they have a high percentage AT content in their genome and are characterized by having more compact genomes than other adenoviruses. The protease gene from all three viruses contained the active site residues (H55-D72-C122 triad) and C104 (providing a disulfide bond to cofactor pVIc). However, P137, found in all other members of the Mastadenovirus genus, and thought to be involved in trafficking, was missing from the protease of the EDS virus, BAV-7, and OAV287. These results suggest that EDS virus should be classified along with BAV-7 and OAV287 in a separate taxon.

Characterisation of Australian ovine adenovirus isolates

We have characterised two groups of adenoviruses isolated from sheep in Australia. Restriction endonuclease maps for enzymes BamHI, ClaI, SalI, SmaI and SphI have been determined for the genome of ovine adenoviruses related to bovine adenovirus serotype 7 (BAV 7) from sheep in Western Australia. Although previously serotyped as BAV 7 these isolates are different from bovine isolates of BAV 7 based on comparison with published restriction endonuclease profiles and maps of BAV 7 cattle isolates. Additional adenovirus isolates obtained from Victorian sheep have been serotyped as ovine adenovirus type 5 (OAV 5). On the basis of restriction endonuclease analysis these viruses are different from the sheep BAV 7 isolates. Following infection of sheep with ovine BAV 7 and OAV 5 isolates, virus was recovered from nasal and rectal swabs for several days. Antibodies detected by ELISA and serum neutralisation tests (SN) developed by 15 days after infection. Virus also spread from the infected sheep to an incontact control and one of ten sheep purchased for infection studies had SN antibodies to BAV 7 suggesting that BAV 7-like viruses naturally infect sheep in Victoria and Western Australia. With further development, these ovine adenoviruses may be suitable as vectors for the delivery of vaccine antigens to sheep and cattle.

Pulmonary lesions in lambs experimentally infected with ovine adenovirus 5 strain RTS-42

Twelve lambs were inoculated transtracheally and intranasally with Mastadenovirus ovi 5 strain RTS-42 and killed sequentially. Pulmonary lesions were studied by light and electron microscopy. Four lambs served as sham inoculated controls. Pulmonary lesions consisted of multifocal areas of bronchiolitis and alveolitis associated with necrosis and sloughing of isolated type I and type II alveolar epithelial cells and nonciliated bronchiolar epithelial cells. This was followed rapidly by hyperplasia of the remaining epithelium and repair of the damage. A cellular infiltrate of neutrophils and macrophages began at 2 days after inoculation, peaked at 4 days after inoculation, gradually diminished until minimal at 12 days after inoculation, and was resolved at 21 days after inoculation. Surfactant was abundant and, along with debris, was removed from the alveoli by macrophages. Clinical disease was not seen, but lesions were believed to be sufficient to allow bacteria to colonize the lungs and cause severe disease.

Subtypes of bovine adenovirus type 2 exhibit major differences in region E3

The genomes of two adenovirus type 2 strains which were isolated from different hosts have been investigated. One of these strains designated ORT-111 was originally isolated from a lamb in Hungary during an outbreak of pneumoenteritis. This isolate was typed as bovine adenovirus type 2 (Ad bos 2) in a neutralization assay. The genome of ORT-111 was compared to that of the prototype strain of Ad bos 2, a virus which exclusively has been isolated from cattle. Electron microscopic heteroduplex analysis showed that 95% of the genomes were well matched, forming stable duplexes at Tm -6 degrees. Two distinct substitution loops were, however, seen which were approximately 0.5 and 1.0 kbp long. The centers of the two loops were located 5.3 and 7.7 kbp from one end of the Ad bos 2 genome. In order to map these regions relative to the gene map of human adenovirus type 2 (Ad2), restriction enzyme cleavage fragments of the two bovine viruses were cloned and hybridized to different sets of restriction fragments of human Ad2. From these results it was apparent that the centers of the two substitution loops were located at coordinates 76 and 83, respectively; thus at positions which fall within region E3 and the adjacent gene for polypeptide VIII of human Ad2. The observed differences between the genomes of the two Ad bos 2 strains are in sharp contrast to those previously observed when the genomes of different human adenovirus serotypes were compared. In the latter case the hexon and the fiber genes showed the most pronounced variation.