Molecular cloning and sequence analysis of the penton base genes of type II avian adenoviruses

Prevalence and Molecular Characteristics of FAdV-4 from Indigenous Chicken Breeds in Yunnan Province, Southwestern China

Fowl adenovirus-induced hepatitis-pericardial effusion syndrome outbreaks have been increasingly reported in China since 2015, resulting in substantial economic losses to the poultry industry. The genetic diversity of indigenous chicken results in different immune traits, affecting the evolution of these viruses. Although the molecular epidemiology of fowl adenovirus serotype 4 (FAdV-4) has been well studied in commercial broiler and layer chickens, the prevalence and genetic characteristics of FAdV-4 in indigenous chickens remain largely unknown. In this study, samples were collected from six indigenous chicken breeds in Yunnan province, China. FAdV-positive samples were identified in five of the six indigenous chicken populations via PCR and 10 isolates were obtained. All FAdVs belonged to serotype FAdV-4 and species FAdV-C. The hexon, fiber, and penton gene sequence comparison analysis demonstrated that the prevalence of FAdV-4 isolates in these chickens might have originated from other provinces that exported chicks and poultry products to Yunnan province. Moreover, several distinct amino acid mutations were firstly identified in the major structural proteins. Our findings highlighted the need to decrease inter-regional movements of live poultry to protect indigenous chicken genetic resources and that the immune traits of these indigenous chickens might result in new mutations of FAdV-4 strains.

Phylogenetic and pathogenic characterization of current fowl adenoviruses in China

In recent years, fowl adenoviruses (FAdVs) continue to outbreak and cause huge economic losses to the poultry industry in China. The homologous recombination accounts for the diversity serotypes of adenovirus. However, the prevalence, recombination and pathogenicity of current FAdVs remain unclear. Herein, the prevalence, phylogenetic feature and pathogenicity of FAdVs in China in 2019 were characterized. Our findings showed that multiple species and serotypes of FAdVs currently circulate in China, including A, C, D and E species, and 1, 2, 4, 8a and 8b serotypes. Notably, the recombination occurred between FAdV-8a and FAdV-8b, and the recombination regions included Hexon, Fiber, ORF19 and ORF20. All five FAdVs replicated effectively in various chicken tissues, and viral shedding peaked at 4-8 dpi. Except CH/GDSZ/1905(FAdV-1/A), the remaining FAdVs caused obvious inclusion body hepatitis (IBH) in 3-week-old specific-pathogen-free (SPF) chickens, of which CH/JSXZ/1905(FAdV-4/C) caused hydropericardium-hepatitis syndrome (HHS) with a mortality rate of 62.5%. Taken together, our findings illustrate the prevalence, recombination and pathogenicity of current FAdVs in China and strengthen surveillance and further pathogenicity studies of FAdVs are extremely urgent.

Characterization of a new species of adenovirus in falcons

In 1996, a disease outbreak occurred at a captive breeding facility in Idaho, causing anorexia, dehydration, and diarrhea or sudden death in 72 of 110 Northern aplomado falcons (Falco femoralis septentrionalis) from 9 to 35 days of age and in 6 of 102 peregrine falcons (Falco peregrinus) from 14 to 25 days of age. Sixty-two Northern aplomado and six peregrine falcons died. Epidemiologic analyses indicated a point source epizootic, horizontal transmission, and increased relative risk associated with cross-species brooding of eggs. Primary lesions in affected birds were inclusion body hepatitis, splenomegaly, and enteritis. The etiology in all mortalities was determined by molecular analyses to be a new species of adenovirus distantly related to the group I avian viruses, serotypes 1 and 4, Aviadenovirus. In situ hybridization and PCR demonstrated that the virus was epitheliotropic and lymphotropic and that infection was systemic in the majority of animals. Adeno-associated virus was also detected by PCR in most affected falcons, but no other infectious agents or predisposing factors were found in any birds. Subsequent to the 1996 epizootic, a similar disease caused by the same adenovirus was found over a 5-year period in orange-breasted falcons (Falco deiroleucus), teita falcons (Falco fasciinucha), a merlin (Falco columbarius), a Vanuatu peregrine falcon (Falco peregrinus nesiotes), and gyrfalcon x peregrine falcon hybrids (Falco rusticolus/peregrinus) that died in Wyoming, Oklahoma, Minnesota, and California. These findings indicate that this newly recognized adenovirus is widespread in western and midwestern North America and can be a primary pathogen in different falcon species.

Identification and characterization of penton base and pVIII protein of egg drop syndrome virus

The nucleotide sequence and location of the penton base and pVIII genes of the egg drop syndrome (EDS) virus an avian adenovirus, were determined. The penton base gene is located at 34.8-38.8 map units. The coding sequence has a length of 1359 nt and encodes a polypeptide of 452 amino acids (aa) with a molecular weight of 51 105 Da. The amino acid sequence shows a homology of 57.3 and 55.3% to the structural protein IH of human adenovirus serotype 2 (HAd2) and fowl adenovirus serotype 1 (FAV1). The penton base protein lacks the integrin binding motifs RGD (Arg-Gly-Asp) and LDV (Leu-Asp-Val). At 65.1-67.3 map units an open reading frame of 753 nucleotides was identified which encodes the structural protein pVIH. It forms a protein of 250 aa with an expected molecular weight of 28 501 Da. Possible protease cleavage sites were identified. Amino acid homologies of 30.8 and 27.7% were found to the HAd2 and FAV1 pVIII genes. Remarkably, the overall amino acid identity with ovine adenovirus pVIII is 52%. The start codons of both genes are shifted leftwards compared with the respective structural elements on the HAd2 or FAV1 genomes which indicates a different genomic organization of the EDS virus.