title: Detailed molecular analyses of the hexon loop-1 and fibers of fowl aviadenoviruses reveal new insights into the antigenic relationship and confirm that specific genotypes are involved in field outbreaks of inclusion body hepatitis.
abstract: Forty-eight fowl aviadenoviruses (FAdVs) isolated from recent IBH outbreaks across Europe were investigated, by utilizing for the first time the two major adenoviral antigenic domains, hexon loop-1 and fiber, for compound molecular characterization of IBH-associated FAdVs. Successful target gene amplification, following virus isolation in cell culture or from FTA-card samples, demonstrated presence of FAdVs in all cases indicative for IBH. Based on hexon loop-1 analysis, 31 European field isolates exhibited highest nucleotide identity (>97.2%) to reference strains FAdV-2 or -11 representing FAdV-D, while 16 and one European isolates shared >96.0% nucleotide identity with FAdV-8a and -8b, or FAdV-7, the prototype strains representing FAdV-E. These results extend recognition of specific FAdV-D and FAdV-E affiliate genotypes as causative agents of IBH to the European continent. In all isolates, species specificity determined by fiber gene analysis correlated with hexon-based typing. A threshold of 72.0% intraspecies nucleotide identity between fibers from investigated prototype and field strains corresponded with demarcation criteria proposed for hexon, suggesting fiber-based analysis as a complementary tool for molecular FAdV typing. A limited number of strains exhibited inconsistencies between hexon and fiber subclustering, indicating potential constraints for single-gene based typing of those FAdVs. Within FAdV-D, field isolate fibers shared a high degree of nucleotide (>96.7%) and aa (>95.8%) identity, while FAdV-E field isolate fibers displayed greater nucleotide divergence of up to 22.6%, resulting in lower aa identities of >81.7%. Furthermore, comparison with FAdVs from IBH outbreaks outside Europe revealed close genetic relationship in the fiber, independent of the strains' geographic origin.
authors.affiliation: Christian Doppler Laboratory for Innovative Poultry Vaccines, University of Veterinary Medicine, Vienna, Austria. Electronic address: anna.schachner@vetmeduni.ac.at.
authors.forename: Anna
authors.initials: A
authors.lastname: Schachner
authors.affiliation: Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
authors.forename: Ana
authors.initials: A
authors.lastname: Marek
authors.affiliation: Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Grafl
authors.affiliation: Christian Doppler Laboratory for Innovative Poultry Vaccines, University of Veterinary Medicine, Vienna, Austria; Clinic for Poultry and Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Hess
mesh_terms: D000257:Adenoviridae Infections / Q000453:epidemiology / Q000276:immunology / Q000821:virology*; D000595:Amino Acid Sequence; D000818:Animals; D000259:Aviadenovirus / Q000235:genetics*; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics*; D004196:Disease Outbreaks; D005838:Genotype; D006524:Hepatitis, Viral, Animal / Q000453:epidemiology / Q000276:immunology / Q000821:virology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D036022:Capsid Proteins; C018315:hexon capsid protein, Adenovirus
keywords: Fiber; Fowl aviadenovirus; Hexon; Inclusion body hepatitis; Molecular characterization