Abstract
Fowl adenoviruses (FAdVs) are infectious agents, mainly of chickens, which cause economic losses to the poultry industry. Only a single serotype, namely FAdV-5, constitutes the species Fowl aviadenovirus B (FAdV-B); however, recently, phylogenetic analyses have identified divergent strains of the species, implicating a more complex scenario and possibly a novel serotype. Therefore, field isolates of the species were collected to investigate the contemporary diversification within FAdV-B, including traditional serotyping. Full genomes of fourteen FAdV-B strains were sequenced and four strains, possessing discriminatory mutations in the antigenic domains, were compared using virus cross-neutralization. Essentially, strains with identical antigenic signatures to that of the first described divergent strain were found in the complete new dataset. While chicken antiserum against FAdV-5 reference strain 340 could not neutralize any of the newly isolated viruses, low homologous/heterologous titer ratios were measured reciprocally. Although they argue against a new serotype, our results indicate the emergence of escape variants in FAdV-B. Charge-influencing amino acid substitutions accounted for only a few mutations between the strains; still, these enabled one-way cross-neutralization only. These findings underline the continued merit of the cross-neutralization test as the gold standard for serotyping, complementary to advancing sequence data, and provide a snapshot of the actual diversity and evolution of species FAdV-B.
Highlights
Adenoviruses possess an icosahedral, non-enveloped capsid and a linear, non-segmented, double-stranded DNA genome, and infect all classes of vertebrates [1,2]
Strains of the species Fowl aviadenovirus A–E can cause severe economic losses for the poultry industry, especially in broiler production [5,6]. These five species are further divided into 12 serotypes (FAdV-1-8a and 8b-11), and there is a single serotype, fowl adenovirus 5 (FAdV-5), classified into the species Fowl aviadenovirus B (FAdV-B) [7,8]
Including plaque formation, rounding and condensation of cells, and detachment from the plate, similar to those caused by the reference strain 340
Summary
Adenoviruses possess an icosahedral, non-enveloped capsid and a linear, non-segmented, double-stranded DNA genome, and infect all classes of vertebrates [1,2]. The members of the genus Aviadenovirus infect exclusively birds [4]. Strains of the species Fowl aviadenovirus A–E can cause severe economic losses for the poultry industry, especially in broiler production [5,6]. These five species are further divided into 12 serotypes (FAdV-1-8a and 8b-11), and there is a single serotype, fowl adenovirus 5 (FAdV-5), classified into the species Fowl aviadenovirus B (FAdV-B) [7,8]. All other FAdV species contain certain serotypes which are the etiological agents of well-characterized chicken diseases (inclusion body hepatitis, hepatitis–hydropericardium syndrome and gizzard erosion) [9]. FAdV-B strains were detected from various pathologies (arthritis, enteritis, inclusion body hepatitis and hemorrhages, among others), but no primary disease was associated with them [10,11,12,13]
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