An adenovirus isolated from sheep and its relationship to type 2 bovine adenovirus

Adenovirus in Rural Côte D'Ivoire: High Diversity and Cross-Species Detection

The Taï region in Western Côte d'Ivoire is characterized by extensive overlap of human and animal habitats. This could influence patterns of adenovirus transmission between humans and domestic animals. Fecal samples from humans and various domestic animals were tested for the presence of adenoviruses by PCR. Phylogenetic and species delineation analyses were performed to further characterize the adenoviruses circulating in the region and to identify potential cross-species transmission events. Among domestic animals, adenovirus shedding was frequent (21.6% of domestic mammals and 41.5% of chickens) and the detected strains were highly diverse, several of them representing novel types. Although no evidence for zoonotic transmission of animal adenovirus was obtained, the present study provides concordant evidence in favor of common cross-species transmission of adenoviruses between different animal species and first indications for adenovirus transmission from humans to animals. These findings underline the thus far underestimated importance of reverse zoonotic transmission of viruses and of the role of domestic animals as pathogen reservoirs, "bridge species," or intermediate hosts.

Enteric viral infections in lambs or kids

Diarrhoea in lambs and kids is often a complex, multi-factorial syndrome. Common infectious causes of diarrhoea in lambs and kids during the first month of life are of bacterial or parasite nature. However, despite appreciable improvements in management practices and prevention and treatment strategies over the last decades, diarrhoea is still a common and costly syndrome affecting newborn small ruminants. Recent advances in the diagnostics and metagenomic investigations of the enteric environment have allowed discovering a number of novel viruses, although their pathobiological properties remain largely unknown. Assessing more in depth the impact of these viruses on the health and productions of these livestock animals is necessary and requires the development of accurate diagnostic tools and updating of the diagnostic algorithms of enteric pathological conditions.

DNA sequencing and phylogenetic analysis of the protease gene of ovine adenovirus 3 suggest that adenoviruses of sheep belong to two different genera

Until now, the only published ovine adenovirus DNA sequence was the complete genome of ovine adenovirus isolate 287 (OAV287) which, compared to other mammalian adenoviruses, possesses strikingly unique genomic organisation and should properly be classified into a new adenovirus genus. The protease gene sequence of ovine adenovirus type 3 (OAdV-3) was determined and analysed. The results of phylogenetic analysis of the 205 residue long protein demonstrated that OAdV-3 belongs to the genus Mastadenovirus, and is surprisingly closely related to bovine adenovirus type 2. In spite of the common host origin, the evolutionary distance between OAdV-3 and OAV287 proved to be great suggesting that sheep, similarly to cattle and fowl, might be infected by distantly related adenoviruses belonging to different genera.

Experimental infection of weaned calves and lambs with two strains of bovine adenovirus type 2

The pathogenicity of two genetically different strains of bovine adenovirus type 2 (BAV-2) was tested in a double cross experimental infection of weaned lambs and calves. One of the virus strains was isolated from cattle and represented BAV-2 subgroup "A", while the other was isolated from sheep and belonged to subgroup "B" (Belák et al., 1983). The two virus strains caused infection both in lambs and calves; the viruses were repeatedly reisolated and definite seroconversion was found in all four groups. However, remarkable differences were observed in the pathogenicity: the most intensive virus multiplication and shedding, the most severe clinical symptoms and histopathological lesions were observed in the lamb group infected with the ovine isolate.

Detection of bovine adenovirus nucleic acid sequences in nasal specimens by biotinylated DNA probes

Bovine adenovirus infection has been detected in experimentally infected lambs by applying the rapid and simple DNA detection method of direct filter hybridization (DFH). Three fragments of BAV-2 DNA were obtained by molecular cloning and labelled with biotin. Clone 207, representing an EcoRI fragment between coordinates 35 to 55 of the viral genome, showed the highest sensitivity to detect adenovirus DNA, thus, this probe was applied on nasal cells from the lambs. Comparative tests revealed a concordance over 97% between the results of conventional virus isolation and of the DFH method. Virus isolation required several weeks to be completed, whereas the DFH method gave results within 10 hours. Considering its simplicity, speed and economy, the DFH method is recommended as a practical diagnostic tool for the direct detection of adenoviruses in clinical specimens.

Antigenic relationship between human and animal adenovirus hexons determined by means of monoclonal antibodies directed against bovine adenovirus type 2 hexon

Eight monoclonal antibodies (MAbs) directed against bovine adenovirus (BAV) 2 subtype B hexon were studied with 12 different hexon types of human adenoviruses (AV) belonging to 5 different subgenera using indirect ELISA, passive hemagglutination (HA), and gel diffusion assays. Two hexon types of animal origin (BAV3 and SAV16) were investigated, too. The reactivity of the MAb IV.F3 was the broadest, i.e. in ELISA and HA experiments it reacted with all hexon types studied. Based on these results as well as on the results of gel diffusion assays, this MAb should recognize the genus specific epitope of adenovirus hexons. Three MAbs (CA12, III.B11, and A12) could recognize different epitopes showing intersubgenus or intertype specificities. In spite of the fact, that all the eight MAbs proved to be bound by the hexon of ORT/111 (BAV2 subtype B) blotted onto nitrocellulose filter, four of the eight MAbs (BB7, BH5, II.A9, and IV.F5) failed to react with any human, and animal hexon types used in the present experiments. The results suggest that a gradient of antigenic relationship may exist between BAV2 hexon and the hexons of human serotypes.

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.

DNA structure, and hemagglutination properties of bovine adenovirus type 2 strains which bypass species specificity

Bovine adenovirus type 2 (Ad bos 2) strains were examined which had been isolated during natural outbreaks among calves, and lambs in Hungary [Belák, S., Pálfi, V.: Arch. ges. Virusforsch. 46,366-369 (1974)]. Differences were detected in hemagglutination properties, and in the restriction site maps of the DNA, which seem to be sufficient to group isolates of Ad bos 2 into two subtypes (subspecies). Some of the strains, recovered from cattle including prototype strain No. 19 are suggested to be separated as subtype A. These viruses hemagglutinate bovine red blood cells, and the physical map of the DNA is similar to, or identical with that of the prototype strain. Virus strains tentatively grouped into subtype B are pathogenic for both cattle, and sheep under natural conditions. Members of subtype B hemagglutinate only rat erythrocytes, and characteristic differences may be detected with BamHI, EcoRI, KpnI, and SalI restriction endonucleases in comparison to the physical maps of the DNA of prototype virus. The genome size of all isolates tested was measured to be of Mr 19.5 to 20.0 X 10(6), similar to Ad ovi 1, 4, and Ad bos 4, and 6. All isolates of subtype B characteristics were shown to encapsidate heterogeneous genome populations which could be distinguished from those of subtype A by the presence of specific restriction endonuclease cleavage fragments with molar ratios of less than 1.0.

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

Two adenoviruses (WV419/75 and WV757/75), isolated from lambs in New Zealand were compared using neutralisation tests with the five recognised ovine adenovirus species, NINE bovine and four porcine adenoviruses. WV419/75 did not cross-react with any of the viruses tested and represents a new ovine adenovirus species (OAV-6). WV757/75 cross-reacted with bovine adenovirus type 7 (BAV-7) with a homologous to heterologous titre ratio of 16 in one direction only, and also showed a substantial one-way cross reaction in haemagglutination-inhibition tests (WV757 antiserum inhibiting haemagglutination by BAV-7). There was therefore insufficient distinction from BAV-7 virus to allow designation as a separate species. Fluorescent antibody studies with WV419 and WV757 demonstrated virus inclusions in the nuclei of infected cells. These were stained by antiserum to OAV-4 indicating presence of the mammalian group antigen. Thin section electron microscope studies showed typical adenovirus particles and associated inclusions in cell nuclei. The similarity of the two viruses to the bovine subgroup 2 adenoviruses in several of their properties is discussed.

Experimental infection of calves with an adenovirus isolated from sheep and related to bovine Adenovirus type 2 I. Clinical and virological studies

Colostrum deprived calves were experimentally infected with an adenovirus isolated from sheep and related to bovine adenovirus type 2. The calves showed respiratory symptoms and mild diarrhoea from the third day after infection. Laboratory tests revealed the development of leucopenia, lymphopenia, a drop of the pH of the urine and the appearance of pathological changes in the urine. The animals shed the virus in their nasal discharge, faeces and urine. Comparing the clinical and virological findings with the previous experimental infection of lambs it is concluded, that this type of adenovirus is similarly pathogenic for the two ruminant species.

Adenovirus infection in lambs. II. Experimental infection of lambs

Adenovirus strain GY/14 isolated during a natural outbreak was used in experimental infection. Three weeks old lambs responded with temperature rise, respiratory symptoms and diarrhoea to the infection. Infection spread to a contact animal, too. Reisolation of the virus was successful from the nasal discharge and feces from the 3rd to 10th, and the 3rd to 5th day following infection, respectively. In the killed experimental animals the pathological and histological changes observed were similar to those observed in natural cases. On comparing the natural outbreaks with the experimental infection the only difference appeared in the severity of the changes. Following the experimental infection characteristic nuclear inclusions appeared in the nasal and bronchiolar epithelium, in the alveolar septal cells and in the reticular cells of the lymph nodes. Epizootiologic observations and experimental results confirm the assumption that our adenovirus strains isolated from natural cases are pathogenic for lambs.

Comparative serological studies with mammalian adenoviruses

Nine serotypes of bovine adenovirus, five serotypes of ovine adenovirus, and four serotypes of porcine adenovirus were compared in reciprocal cross-neutralisation tests, to determine if viruses isolated from different species were indeed distinct serotypes. In addition, the above serotypes were tested for possible antigenic relationships with 28 of 32 human adenoviruses, by one-way cross neutralisation tests with human adenovirus antisera. The results indicated that all viruses tested were distinct serotypes. Ovine adenovirus types 4 and 5, until now not compared by neutralisation tests, were confirmed as separate serotypes.